Sea water quality assessment of Prince Islands' beaches in Istanbul.

PubMed

Ilter Turkdogan Aydinol, F; Kanat, Gurdal; Bayhan, Hurrem

2012-01-01

In this study, seawater samples were subjected to microbiological and physicochemical analysis (water temperature, pH, Secchi disc depth and ammonia) in the Prince Islands which are located in Marmara Sea, being one of the most popular swimming areas in Istanbul. The monitoring program of the study has been carried out in the summer for 6 weeks at eight stations around the Prince Islands. Measured total coliform values were between 5 ± 2 and 26 ± 55 and faecal coliform values were between 4 ± 2 and 24 ± 50 in the monitoring stations. A statistical study has been conducted to find the relationship between total and faecal coliform concentrations, and t tests were applied. There was no significant difference in each location of the Islands, except one location. The results were evaluated by comparing with national and EU bathing water standards. Results of the study show that deep sea discharges and sea currents contribute dilution of coliform concentration in a positive way, and locations near coastal zones of the islands have acceptable values which are required by the regulations.

The Correlation between Insertion Depth of Prodisc-C Artificial Disc and Postoperative Kyphotic Deformity: Clinical Importance of Insertion Depth of Artificial Disc.

PubMed

Lee, Do-Youl; Kim, Se-Hoon; Suh, Jung-Keun; Cho, Tai-Hyoung; Chung, Yong-Gu

2012-09-01

This study was designed to investigate the correlation between insertion depth of artificial disc and postoperative kyphotic deformity after Prodisc-C total disc replacement surgery, and the range of artificial disc insertion depth which is effective in preventing postoperative whole cervical or segmental kyphotic deformity. A retrospective radiological analysis was performed in 50 patients who had undergone single level total disc replacement surgery. Records were reviewed to obtain demographic data. Preoperative and postoperative radiographs were assessed to determine C2-7 Cobb's angle and segmental angle and to investigate postoperative kyphotic deformity. A formula was introduced to calculate insertion depth of Prodisc-C artificial disc. Statistical analysis was performed to search the correlation between insertion depth of Prodisc-C artificial disc and postoperative kyphotic deformity, and to estimate insertion depth of Prodisc-C artificial disc to prevent postoperative kyphotic deformity. In this study no significant statistical correlation was observed between insertion depth of Prodisc-C artificial disc and postoperative kyphotic deformity regarding C2-7 Cobb's angle. Statistical correlation between insertion depth of Prodisc-C artificial disc and postoperative kyphotic deformity was observed regarding segmental angle (p<0.05). It failed to estimate proper insertion depth of Prodisc-C artificial disc effective in preventing postoperative kyphotic deformity. Postoperative segmental kyphotic deformity is associated with insertion depth of Prodisc-C artificial disc. Anterior located artificial disc leads to lordotic segmental angle and posterior located artificial disc leads to kyphotic segmental angle postoperatively. But C2-7 Cobb's angle is not affected by artificial disc location after the surgery.

Application of LANDSAT to the surveillance and control of lake eutrophication in the Great Lakes basin. [Saginaw Bay, Michigan and Wisconsin

NASA Technical Reports Server (NTRS)

Rogers, R. H. (Principal Investigator)

1976-01-01

The author has identified the following significant results. Computer techniques were developed for mapping water quality parameters from LANDSAT data, using surface samples collected in an ongoing survey of water quality in Saginaw Bay. Chemical and biological parameters were measured on 31 July 1975 at 16 bay stations in concert with the LANDSAT overflight. Application of stepwise linear regression bands to nine of these parameters and corresponding LANDSAT measurements for bands 4 and 5 only resulted in regression correlation coefficients that varied from 0.94 for temperature to 0.73 for Secchi depth. Regression equations expressed with the pair of bands 4 and 5, rather than the ratio band 4/band 5, provided higher correlation coefficients for all the water quality parameters studied (temperature, Secchi depth, chloride, conductivity, total kjeldahl nitrogen, total phosphorus, chlorophyll a, total solids, and suspended solids).

Kerr Reservoir LANDSAT experiment analysis for March 1981

NASA Technical Reports Server (NTRS)

Lecroy, S. R. (Principal Investigator)

1982-01-01

LANDSAT radiance data were used in an experiment conducted on the waters of Kerr Reservoir to determine if reliable algorithms could be developed that relate water quality parameters to remotely sensed data. A mix of different types of algorithms using the LANDSAT bands was generated to provide a thorough understanding of the relationships among the data involved. Except for secchi depth, the study demonstrated that for the ranges measured, the algorithms that satisfactorily represented the data encompass a mix of linear and nonlinear forms using only one LANDSAT band. Ratioing techniques did not improve the results since the initial design of the experiment minimized the errors against which this procedure is effective. Good correlations were found for total suspended solids, iron, turbidity, and secchi depth. Marginal correlations were discovered for nitrate and tannin + lignin. Quantification maps of Kerr Reservoir are presented for many of the water quality parameters using the developed algorithms.

Estimation of water turbidity in Gorgan Bay, South-east of Caspian Sea by using IRS-LISS-III images.

PubMed

Aghighi, Hossein; Alimohammadi, Abbas; Saradjian, Mohammad Reza; Ashourloo, Davood

2008-03-01

In this research, usefulness of IRS-LISS-III data of Gorgan Bay, South-east of Caspian Sea located in North of Iran for water turbidity mapping, has been tested. After correction of geometric and radiometric errors, the resulting radiance data were used for examination of correlations between the remotely sensed and in situ water turbidity data simultaneously measured by the Secchi depth approach. Results of this research showed good relations between the Secchi depth and spectral data. The fitted statistical model was very significant (R2 = 0.77) and test of the model performance by independent samples was encouraging. Because of the low costs encountered with acquisition and processing of remotely sensed data, further research in larger scales for the purpose of more precise test of the approach for water turbidity mapping and monitoring is recommended.

The impact of a hydroelectric power plant on the sediment load in downstream water bodies, Svartisen, northern Norway.

PubMed

Bogen, J; Bønsnes, T E

2001-02-05

When the Svartisen hydroelectric power plant was put into operation, extensive sediment pollution was observed in the downstream fjord area. This paper discusses the impact of the power plant and the contribution from various sources of sediment. Computation of the sediment load was based on samples collected one to four times per day. Grain size distribution analyses of suspended sediments were carried out and used as input in a routing model to study the movement of sediments through the system. Suspended sediment delivered to the fjord before the power station was constructed was measured as 8360 metric tons as an annual mean for a 12-year period. During the years 1995-1996 when the power plant was operating, the total suspended load through the power station was measured as 32609 and 30254 metric tons, respectively. Grain size distribution analyses indicate a major change in the composition of the sediments from 9% clay before the power plant was operative to 50-60% clay afterwards. This change, together with the increase in sediment load, is believed to be one of the main causes of the drastic reduction in secchi depths in the fjord. The effect of the suspended sediment load on the fjord water turbidity was evaluated by co-plotting secchi depth and power station water discharge. Measurements during 1995 and 1996 showed that at the innermost of these locations the water failed to attain the minimum requirement of 2 m secchi depth. In later years secchi depths were above the specified level. In 1997 and 1998 the conditions improved. At the more distal locality, the conditions were acceptable with only a few exceptions. A routing model was applied to data acquired at a location 2 km from the power station in order to calculate the contributions from various sediment sources. This model indicated that the contribution from reservoir bed erosion dominated in 1994 but decreased significantly in 1995. Future operation of the power station will mostly take place with a high water level in the reservoir and is likely to result in acceptable water quality in the fjord. However, during periods of low drawdown, sediment pollution may again become a problem.

SIMULATION OF DISSOLVED OXYGEN PROFILES IN A TRANSPARENT, DIMICTIC LAKE

EPA Science Inventory

Thrush Lake is a small, highly transparent lake in northeastern Minnesota. rom 1986 to 1991, vertical profiles of water temperature, dissolved oxygen, chlorophyll a concentration, underwater light irradiance, and Secchi depths were measured at monthly intervals during the ice-fre...

Use of Landsat data to predict the trophic state of Minnesota lakes

NASA Technical Reports Server (NTRS)

Lillesand, T. M.; Johnson, W. L.; Deuell, R. L.; Lindstrom, O. M.; Meisner, D. E.

1983-01-01

Near-concurrent Landsat Multispectral Scanner (MSS) and ground data were obtained for 60 lakes distributed in two Landsat scene areas. The ground data included measurement of secchi disk depth, chlorophyll-a, total phosphorous, turbidity, color, and total nitrogen, as well as Carlson Trophic State Index (TSI) values derived from the first three parameters. The Landsat data best correlated with the TSI values. Prediction models were developed to classify some 100 'test' lakes appearing in the two analysis scenes on the basis of TSI estimates. Clouds, wind, poor image data, small lake size, and shallow lake depth caused some problems in lake TSI prediction. Overall, however, the Landsat-predicted TSI estimates were judged to be very reliable for the secchi-derived TSI estimation, moderately reliable for prediction of the chlorophyll-a TSI, and unreliable for the phosphorous value. Numerous Landsat data extraction procedures were compared, and the success of the Landsat TSI prediction models was a strong function of the procedure employed.

Thermal, chemical, and optical properties of Crater Lake, Oregon

USGS Publications Warehouse

Larson, G.L.; Hoffman, R.L.; McIntire, D.C.; Buktenica, M.W.; Girdner, S.F.

2007-01-01

Crater Lake covers the floor of the Mount Mazama caldera that formed 7700 years ago. The lake has a surface area of 53 km2 and a maximum depth of 594 m. There is no outlet stream and surface inflow is limited to small streams and springs. Owing to its great volume and heat, the lake is not covered by snow and ice in winter unlike other lakes in the Cascade Range. The lake is isothermal in winter except for a slight increase in temperature in the deep lake from hyperadiabatic processes and inflow of hydrothermal fluids. During winter and spring the water column mixes to a depth of about 200-250 m from wind energy and convection. Circulation of the deep lake occurs periodically in winter and spring when cold, near-surface waters sink to the lake bottom; a process that results in the upwelling of nutrients, especially nitrate-N, into the upper strata of the lake. Thermal stratification occurs in late summer and fall. The maximum thickness of the epilimnion is about 20 m and the metalimnion extends to a depth of about 100 m. Thus, most of the lake volume is a cold hypolimnion. The year-round near-bottom temperature is about 3.5??C. Overall, hydrothermal fluids define and temporally maintain the basic water quality characteristics of the lake (e.g., pH, alkalinity and conductivity). Total phosphorus and orthophosphate-P concentrations are fairly uniform throughout the water column, where as total Kjeldahl-N and ammonia-N are highest in concentration in the upper lake. Concentrations of nitrate-N increase with depth below 200 m. No long-term changes in water quality have been detected. Secchi disk (20-cm) clarity varied seasonally and annually, but was typically highest in June and lowest in August. During the current study, August Secchi disk clarity readings averaged about 30 m. The maximum individual clarity reading was 41.5 m in June 1997. The lowest reading was 18.1 m in July 1995. From 1896 (white-dinner plate) to 2003, the average August Secchi disk reading was about 30 m. No long-term changes in the Secchi disk clarity were observed. Average turbidity of the water column (2-550 m) between June and September from 1991 to 2000 as measured by a transmissometer ranged between 88.8% and 90.7%. The depth of 1% of the incident solar radiation during thermal stratification varied annually between 80 m and 100 m. Both of these measurements provided additional evidence about the exceptional clarity of Crater Lake. ?? 2007 Springer Science+Business Media B.V.

Tampa Bay Water Clarity Model (TBWCM): As a Predictive Tool

EPA Science Inventory

The Tampa Bay Water Clarity Model was developed as a predictive tool for estimating the impact of changing nutrient loads on water clarity as measured by secchi depth. The model combines a physical mixing model with an irradiance model and nutrient cycling model. A 10 segment bi...

Water quality determination by photographic analysis. [optical density and water turbidity

NASA Technical Reports Server (NTRS)

Klooster, S. A.; Scherz, J. P.

1973-01-01

Aerial reconnaissance techniques to extract water quality parameters from aerial photos are reported. The turbidity can be correlated with total suspended solids if the constituent parts of the effluent remain the same and the volumetric flow remains relatively constant. A monochromator is used for the selection of the bandwidths containing the most information. White reflectance panels are used to locate sampling points and eliminate inherent energy changes from lens flare, radial lens fall-off, and changing subject illumination. Misleading information resulting from bottom effects is avoided by the use of Secchi disc readings and proper choice of wavelength for analyzing the photos.

LANDSAT digital data for water pollution and water quality studies in Southern Scandinavia

NASA Technical Reports Server (NTRS)

Hellden, U.; Akersten, I.

1977-01-01

Spectral diagrams, illustrating the spectral characteristics of different water types, were constructed by means of simple statistical analysis of the various reflectance properties of water areas in Southern Scandinavia as registered by LANDSAT-1. There were indications that water whose spectral reproduction is dominated by chlorophyllous matter (phytoplankton) can be distinguished from water dominated by nonchlorophyllous matter. Differences between lakes, as well as the patchiness of individual lakes, concerning secchi disc transparency could be visualized after classification and reproduction in black and white and in color by means of line printer, calcomp plotter (CRT), and ink jet plotter respectively.

Coastal Secchi Depth Atlas

DTIC Science & Technology

1985-07-01

ptical properties 5pley. I(-,8). Table 5. Chart 4-Percentage of one-degree squares. 13 f plankton aleae . 0 Table 6. Global coverage-Percentage of one...optical properties result from (e.g., Colorado River), typical in mountainous (tectonic) regions, 9. Hunghlo (Red)110 Mekong and/or organic sediments...typical in mountainous (tectonic) regions, 9. Hungho (Red) 160 Inadequate 10. Mekong 160 Sufficient larger-sized particles in suspension. The

Seasonal variations in zooplankton abundances in the Iturbide reservoir (Isidro Fabela, State of Mexico, Mexico).

PubMed

Sarma, S S S; Osnaya-Espinosa, Lidia Rosario; Aguilar-Acosta, Claudia Romina; Nandini, S

2011-07-01

This studywas undertaken to quantify the seasonal variations of zooplankton (rotifers, cladocerans and copepods) and selected physico-chemical variables (temperature, pH, conductivity, Secchi disc transparency, dissolved oxygen, ammonia, nitrate and phosphate concentrations) in the Iturbide dam. Monthly zooplankton samples (50 l filtered through 50 microm mesh, in duplicates from each of the 4 stations) were collected from February 2008 to January 2009. Simultaneously physico-chemical variables were measured. The zooplankton samples were fixed in 4% formalin in the field. In general, the temperature ranged from 9 to 16 degrees C, rarely exceeding 20 degrees C. Secchi transparency was nearly 100% since the reservoir was shallow (< 2 m) even during the rainy seasons. Dissolved oxygen was generally high, 13-18 mg l(-1). Nitrate levels (10 to 170 microg l(-1)) were low while phosphates were relatively high (9 to 35 microg l(-1)). The Iturbide reservoir was dominated by rotifer species. We encountered in all, 55 taxa of rotifers, 9 cladocerans and 2 copepods. The rotifer families Trichocercidae and Notommatidae had the highest number of species (7 each) followed by Colurellidae and Lecanidae (6 and 5 species, respectively). Trichocerca elongata, Ascomorpha ovalis, K. americana, K. cochlearis, Lepadella patella and Pompholyx sulcata were the dominant rotifers during the study period. On an annual average, rotifer density ranged between 50-200 ind.(-1). Among crustaceans Chydorus brevilabris and Macrothrix triserialis were most abundant. The maximal density of these cladocerans was about 50 ind. l(-1). Copepods were much lower in numbers (< 20 ind. l(-1)). In general the density of zooplankton was higher during summer months (April to July) than during winter. Shannon-Wiener diversity index varied from 1.0 to 4.3 depending on the site and the sampling period. Based on the data of Secchi transparency and nutrient concentrations, the Iturbide reservoir appeared to be mesotrophic.

Size matters: Perceived depth magnitude varies with stimulus height.

PubMed

Tsirlin, Inna; Wilcox, Laurie M; Allison, Robert S

2016-06-01

Both the upper and lower disparity limits for stereopsis vary with the size of the targets. Recently, Tsirlin, Wilcox, and Allison (2012) suggested that perceived depth magnitude from stereopsis might also depend on the vertical extent of a stimulus. To test this hypothesis we compared apparent depth in small discs to depth in long bars with equivalent width and disparity. We used three estimation techniques: a virtual ruler, a touch-sensor (for haptic estimates) and a disparity probe. We found that depth estimates were significantly larger for the bar stimuli than for the disc stimuli for all methods of estimation and different configurations. In a second experiment, we measured perceived depth as a function of the height of the bar and the radius of the disc. Perceived depth increased with increasing bar height and disc radius suggesting that disparity is integrated along the vertical edges. We discuss size-disparity correlation and inter-neural excitatory connections as potential mechanisms that could account for these results. Copyright © 2016 Elsevier Ltd. All rights reserved.

Landsat - What is operational in water resources

NASA Technical Reports Server (NTRS)

Middleton, E. M.; Munday, J. C., Jr.

1981-01-01

Applications of Landsat data in hydrology and water quality measurement were examined to determine which applications are operational. In hydrology, the principal applications have been surface water inventory, and land cover analysis for (1) runoff modeling and (2) abatement planning for non-point pollution and erosion. In water quality measurement, the principal applications have been: (1) trophic state assessment, and (2) measurement of turbidity and suspended sediment. The following applications were found to be operational: mapping of surface water, snow cover, and land cover (USGS Level 1) for watershed applications; measurement of turbidity, Secchi disk depth, suspended sediment concentration, and water depth.

Father Secchi Goes to Washington

NASA Astrophysics Data System (ADS)

McCarthy, M. F.

1994-12-01

In 1848 a small group of Jesuit refugees arrived at Georgetown College near Washington, D.C. Among them was a young priest, Angelo Secchi, who had finished theology studies in Rome, but had not been able to complete his final examinations. This done successfully, Secchi turned to astronomy and the new facilities of the Georgetown College Observatory, directed by its founder, Fr. James Curley. During his two years in Washington, Secchi studied physics, wrote an article on Electrical Rheometry for the Smithsonian Institution, and formed a friendship with Matthew Fontaine Maury of the U.S. Navy, who headed the Chart Service and in 1844 was named superintendent of the National Observatory. This was later named the U.S. Naval Observatory. Secchi's friendships formed during the Washington visit proved most helpful for relations between European astronomers and U.S. colleagues. Secchi, after his return to Rome constructed the Observatory of the Collegio Romano atop the baroque Church of St. Ignatius in Rome and began his work in spectral classification of stars.

Field measurements of the spectral response of natural waters

NASA Technical Reports Server (NTRS)

Bartolucci, L. A.; Robinson, B. F.; Silva, L. F.

1977-01-01

The spectral response (air-water interface reflectance and water-volume scattering) of turbid river water (99 mg/liter suspended solids) and relatively clear lake water (10 mg/liter suspended solids) was measured in situ with a field spectroradiometer. The influence of the river bottom on the spectral response of the water also was determined by using a modified Secchi disc approach. The results indicated that turbid river water had a higher spectral response than clear lake water (about 6 percent) in the red (0.6-0.7 micron) and near-infrared (0.7-0.9 micron) portions of the spectrum. Also, the reflectance characteristics of the river bottom did not influence the spectral response of the turbid river water when the water was deeper than 30 cm

Seafarer citizen scientist ocean transparency data as a resource for phytoplankton and climate research.

PubMed

Seafarers, Secchi Disk; Lavender, Samantha; Beaugrand, Gregory; Outram, Nicholas; Barlow, Nigel; Crotty, David; Evans, Jake; Kirby, Richard

2017-01-01

The oceans' phytoplankton that underpin the marine food chain appear to be changing in abundance due to global climate change. Here, we compare the first four years of data from a citizen science ocean transparency study, conducted by seafarers using home-made Secchi Disks and a free Smartphone application called Secchi, with contemporaneous satellite ocean colour measurements. Our results show seafarers collect useful Secchi Disk measurements of ocean transparency that could help future assessments of climate-induced changes in the phytoplankton when used to extend historical Secchi Disk data.

The aquatic optics of Lake Tahoe, California-Nevada

NASA Astrophysics Data System (ADS)

Swift, Theodore John

The causes of visual clarity decline and variability in Lake Tahoe, USA, were investigated within the framework of hydrologic optics theory. Ultra-oligotrophic subalpine (1898 m elevation) Lake Tahoe is among the world's clearest, deepest (499 m) and largest (500 km2), representing a unique environmental and economic resource. University of California Davis has documented a ˜0.3 m y-1 trend of decreasing Secchi depth, with ˜3 m interannual variations. Previous work strongly suggested two seasonal modes due to independent processes: A June minimum is due primarily to tributary sediment discharge during snowmelt. A December minimum is due to the deepening mixed layer bringing up phytoplankton and other particles that form a deep particle maximum (DCM) well below the summer mixed layer and Secchi depth stratum. SEM and elemental analysis confirmed as much as 60 percent of near-surface suspended particles were of terrestrial inorganic origin in summer, with inorganic particles minimal (˜20 percent) in winter. Chromophoric dissolved organic matter (CDOM) light absorption in Tahoe is extremely low, comparable to pelagic marine waters, and plays a minor role in clarity loss in Tahoe. However, CDOM reduces ultraviolet light penetration. Mean absorption is 0.040 +/- 0.003 m-1 at 400 nm with 0.023 +/- 0.004 nm-1 exponential slope. The CDOM appears to be autochthonous (phytoplankton), rather than allocthonous (terrestrial humic substances). Chlorophyll-specific particulate absorption is similar to that found for temperate oceans, implying that ocean color models can be successfully applied to Lake Tahoe. Chlorophyll-specific diffuse attenuation along with increased scattering by sediments has caused an upward shift of the DCM from 60--90 m (early 1970s) to 40--70 m recently. Increased attenuation will reduce benthic relative to pelagic primary production. Since measurements in 1971, the lake's color has shifted slightly from blue towards green, though more seasonal measurements are needed to fully quantify the recent range of variation. A clarity model was developed that predicts Secchi depth and diffuse attenuation from inorganic particle and chlorophyll concentration. While organic particles are generally the numerical majority, inorganic particles cause ˜60% of clarity loss, algal-derived particles contribute ˜25%, with the remainder due to CDOM and pure water absorption.

The role of gap edge instabilities in setting the depth of planet gaps in protoplanetary discs

NASA Astrophysics Data System (ADS)

Hallam, P. D.; Paardekooper, S.-J.

2017-08-01

It is known that an embedded massive planet will open a gap in a protoplanetary disc via angular momentum exchange with the disc material. The resulting surface density profile of the disc is investigated for one-dimensional and two-dimensional disc models and, in agreement with previous work, it is found that one-dimensional gaps are significantly deeper than their two-dimensional counterparts for the same initial conditions. We find, by applying one-dimensional torque density distributions to two-dimensional discs containing no planet, that the excitement of the Rossby wave instability and the formation of Rossby vortices play a critical role in setting the equilibrium depth of the gap. Being a two-dimensional instability, this is absent from one-dimensional simulations and does not limit the equilibrium gap depth there. We find similar gap depths between two-dimensional gaps formed by torque density distributions, in which the Rossby wave instability is present, and two-dimensional planet gaps, in which no Rossby wave instability is present. This can be understood if the planet gap is maintained at marginal stability, even when there is no obvious Rossby wave instability present. Further investigation shows the final equilibrium gap depth is very sensitive to the form of the applied torque density distribution, and using improved one-dimensional approximations from three-dimensional simulations can go even further towards reducing the discrepancy between one- and two-dimensional models, especially for lower mass planets. This behaviour is found to be consistent across discs with varying parameters.

Crack orientation and depth estimation in a low-pressure turbine disc using a phased array ultrasonic transducer and an artificial neural network.

PubMed

Yang, Xiaoxia; Chen, Shili; Jin, Shijiu; Chang, Wenshuang

2013-09-13

Stress corrosion cracks (SCC) in low-pressure steam turbine discs are serious hidden dangers to production safety in the power plants, and knowing the orientation and depth of the initial cracks is essential for the evaluation of the crack growth rate, propagation direction and working life of the turbine disc. In this paper, a method based on phased array ultrasonic transducer and artificial neural network (ANN), is proposed to estimate both the depth and orientation of initial cracks in the turbine discs. Echo signals from cracks with different depths and orientations were collected by a phased array ultrasonic transducer, and the feature vectors were extracted by wavelet packet, fractal technology and peak amplitude methods. The radial basis function (RBF) neural network was investigated and used in this application. The final results demonstrated that the method presented was efficient in crack estimation tasks.

Crack Orientation and Depth Estimation in a Low-Pressure Turbine Disc Using a Phased Array Ultrasonic Transducer and an Artificial Neural Network

PubMed Central

Yang, Xiaoxia; Chen, Shili; Jin, Shijiu; Chang, Wenshuang

2013-01-01

Stress corrosion cracks (SCC) in low-pressure steam turbine discs are serious hidden dangers to production safety in the power plants, and knowing the orientation and depth of the initial cracks is essential for the evaluation of the crack growth rate, propagation direction and working life of the turbine disc. In this paper, a method based on phased array ultrasonic transducer and artificial neural network (ANN), is proposed to estimate both the depth and orientation of initial cracks in the turbine discs. Echo signals from cracks with different depths and orientations were collected by a phased array ultrasonic transducer, and the feature vectors were extracted by wavelet packet, fractal technology and peak amplitude methods. The radial basis function (RBF) neural network was investigated and used in this application. The final results demonstrated that the method presented was efficient in crack estimation tasks. PMID:24064602

Seafarer citizen scientist ocean transparency data as a resource for phytoplankton and climate research

PubMed Central

Seafarers, Secchi Disk; Lavender, Samantha; Beaugrand, Gregory; Crotty, David; Evans, Jake

2017-01-01

The oceans’ phytoplankton that underpin the marine food chain appear to be changing in abundance due to global climate change. Here, we compare the first four years of data from a citizen science ocean transparency study, conducted by seafarers using home-made Secchi Disks and a free Smartphone application called Secchi, with contemporaneous satellite ocean colour measurements. Our results show seafarers collect useful Secchi Disk measurements of ocean transparency that could help future assessments of climate-induced changes in the phytoplankton when used to extend historical Secchi Disk data. PMID:29211734

Water Quality, Physical Habitat, and Biology of the Kijik River Basin, Lake Clark National Park and Preserve, Alaska, 2004-2005

USGS Publications Warehouse

Brabets, Timothy P.; Ourso, Robert T.

2006-01-01

The U.S. Geological Survey and the National Park Service conducted a water-quality investigation of the Kijik River Basin in Lake Clark National Park and Preserve from June 2004 to March 2005. The Kijik River Basin was studied because it has a productive sockeye salmon run that is important to the larger Kvichak River watershed. Water-quality, physical habitat, and biological characteristics were assessed. Water type throughout the Kijik River Basin is calcium bicarbonate although Little Kijik River above Kijik Lake does have slightly higher concentrations of sulfate and chloride. Alkalinity concentrations are generally less than 28 milligrams per liter, indicating a low buffering capacity of these waters. Lachbuna Lake traps much of the suspended sediment from the glacier streams in the headwaters of the basin as evidenced by low secchi-disc transparency of 1 to 2 meters and low suspended sediment concentrations in the Kijik River downstream from the lake. Kijik Lake is a fed by clearwater streams and has secchi-disc readings ranging from 11 to 15 meters. Streambed sediments collected from four surface sites analyzed for trace elements indicated that arsenic concentrations at all sites were above proposed guidelines. However, arsenic concentrations are due to the local geology, not anthropogenic factors. Benthic macroinvertebrate qualitative multi-habitat samples collected from two sites on the Little Kijik River and two sites on the main stem of the Kijik River indicated a total of 69 taxa present among the four sites. The class Insecta, made up the largest percentage of macroinvertebrates, totaling 70 percent of the families found. The insects were comprised of four orders; Diptera (flies and midges), Ephemeroptera (mayflies), Plecoptera (stoneflies), and Trichoptera (caddisflies). One-hundred twenty-two species of periphytic algae were identified in qualitative multi-habitat samples collected at the four stream sites. Eight species of non-motile, diatoms were collected from all four stream sites suggesting that the areas from which they were collected are relatively stable and unaffected by sedimentation.

Effect of intense short rainfall events on coastal water quality parameters from remote sensing data

NASA Astrophysics Data System (ADS)

Corbari, Chiara; Lassini, Fabio; Mancini, Marco

2016-07-01

Strong rainfall events, especially during summer, in small river basins cause spills in the sea that often compromise the quality of coastal waters. The goal of this paper is then to study the changes of coastal waters quality as a result of intense rainfall events during the bathing season through the use of remote sensing data. These analyses are performed at the outlets of small watersheds which are not usually affected by high sediment transport as in the case of large basins which are persistently affected by intense solid transport which does not allow retrieving a reliable correlation between rainfall events and water quality parameters. Four small watersheds in different Italian regions on the Mediterranean Sea are selected for this study. The remotely sensed parameters of turbidity, total suspend solids and secchi disk depth, are retrieved from MODIS data. Secchi disk depths are also compared to available ground data during the summer seasons between 2003 and 2006 showing good correlations. Then the spatial and temporal changes of these parameters are analyzed after intense short storm events. Increases of turbidity and total suspend solids are found to be around 35 NTU and 20 mg L-1 respectively depending on the intensity of the rainfall event and on the distance from the shoreline. Moreover the recovery of water quality after the rain event is reached after two or three days.

Fjord light regime: Bio-optical variability, absorption budget, and hyperspectral light availability in Sognefjord and Trondheimsfjord, Norway

NASA Astrophysics Data System (ADS)

Mascarenhas, V. J.; Voß, D.; Wollschlaeger, J.; Zielinski, O.

2017-05-01

Optically active constituents (OACs) in addition to water molecules attenuate light via processes of absorption and scattering and thereby determine underwater light availability. An analysis of their optical properties helps in determining the contribution of each of these to light attenuation. With an aim to study the bio-optical variability, absorption budget and 1% spectral light availability, hydrographical (temperature and salinity), and hyperspectral optical (downwelling irradiance and upwelling radiance) profiles were measured along fjord transects in Sognefjord and Trondheimsfjord, Norway. Optical water quality observations were also performed using Secchi disc and Forel-Ule scale. In concurrence, water samples were collected and analyzed via visible spectrophotometry, fluorometry, and gravimetry to quantify and derive inherent optical properties of the water constituents. An absorption model (R2 = 0.91, n = 36, p < 0.05) as a function of OACs is developed for Sognefjord using multiple regression analysis. Influenced by glacial meltwater, Sognefjord had higher concentration of inorganic suspended matter, while Trondheimsfjord had higher concentrations of CDOM. Increase in turbidity caused increased attenuation of light upstream, as a result of which the euphotic depth decreased from outer to inner fjord sections. Triangular representation of absorption budget revealed dominant absorption by CDOM at 443-555 nm, while that by phytoplankton at 665 nm. Sognefjord however exhibited much greater optical complexity. A significantly strong correlation between salinity and acdom440 is used to develop an algorithm to estimate acdom440 using salinity in Trondheimsfjord.

Relations of biological indicators to nutrient data for lakes and streams in Pennsylvania and West Virginia, 1990-98

USGS Publications Warehouse

Brightbill, Robin A.; Koerkle, Edward H.

2003-01-01

The Clean Water Action Plan of 1998 provides a blueprint for federal agencies to work with states, tribes, and other stakeholders to protect and restore the Nation's water resources. The plan includes an initiative that addresses the nutrient-enrichment problem of lakes and streams across the United States. The U.S. Environmental Protection Agency (USEPA) is working to set nutrient criteria by nationwide nutrient ecoregions that are an aggregation of the Omernik level III ecoregions. Because low levels of nutrients are necessary for healthy streams and elevated concentrations can cause algal blooms that deplete available oxygen and kill off aquatic organisms, criteria levels are to be set, in part, using the relation between chlorophyll a and concentrations of total nitrogen and total phosphorus.Data from Pennsylvania and West Virginia, collected between 1990 and 1998, were analyzed for relations between chlorophyll a, nutrients, and other explanatory variables. Both phytoplankton and periphyton chlorophyll a concentrations from lakes and streams were analyzed separately within each of the USEPA nutrient ecoregions located within the boundaries of the two states. These four nutrient ecoregions are VII (Mostly Glaciated Dairy), VIII (Nutrient Poor, Largely Glaciated Upper Midwest and Northeast), IX (Southeastern Temperate Forested Plains and Hills), and XI (Central and Eastern Forested Uplands).Phytoplankton chlorophyll a concentrations in lakes were related to total nitrogen, total phosphorus, Secchi depth, concentration of dissolved oxygen, pH, water temperature, and specific conductivity. In nutrient ecoregion VII, nutrients were not significant predictors of chlorophyll a concentrations. Total nitrogen, Secchi depth, and pH were significantly related to phytoplankton chlorophyll a concentrations in nutrient ecoregion IX. Lake periphyton chlorophyll a concentrations from nutrient ecoregion XI were related to total phosphorus rather than total nitrogen, Secchi depth, and pH. In all cases, Secchi depth was inversely related to the chlorophyll a concentrations in a lake. Nutrient ecoregion VIII had too few samples for any type of analysis.Streams within the different nutrient ecoregions had many variables that were significantly related to periphyton chlorophyll a concentrations. These variables consisted of total nitrogen, total phosphorus, drainage area, percent forest cover, several macroinvertebrate indices, pH, basin slope, total residue, total suspended solids, and water temperature. Nutrients were not significantly related to periphyton chlorophyll a in streams within nutrient ecoregions VII or IX but were in nutrient ecoregion XI. Drainage area, percent forest cover, and several invertebrate indices were significant variables in nutrient ecoregion VII. Percent forest cover and several invertebrate indices had a negative relation with chlorophyll a concentrations in these streams. Percent forest cover and basin slope had a negative effect on periphyton in nutrient ecoregion IX streams. Light availability was more critical to periphyton growth in streams than nutrients.Ecoregion XI had enough samples to do seasonal analyses. Summer-season periphyton chlorophyll a concentrations in nutrient ecoregion XI streams were positively related to total phosphorus and drainage area but negatively related to percent forest cover. Summer-season phytoplankton in streams was related to different variables within the same nutrient ecoregion. Both total nitrogen and total phosphorus were positively related with chlorophyll a concentrations as well as basin slope, total residue, and total suspended solids but negatively related to pH. The winter stream phytoplankton chlorophyll a concentrations were related to water temperature only.

The use of LANDSAT-1 imagery for water quality studies in southern Scandinavia

NASA Technical Reports Server (NTRS)

Hellden, U.

1975-01-01

The possibilities of using LANDSAT-1 images for environmental studies, with special references to water quality studies, were investigated by selecting test areas in southern Scandinavia. The MSS images of different bands are compared under the magnification of an Interpretoscope and densitometric analyses are performed in a Schnell-photometer. The possibility of tracing pollution plumes is studied in the Oresund outside Copenhagen. The effect of different sewers and the circulation of the polluted water is analyzed in various situations. The variation in reflectivity of a great number of lakes in South and Middle Sweden is studied by means of densitometric analyses and significant regional differences are found. The correlation with in situ measurements of water quality (turbidity and secchi disc transparency) of the sampled lakes (made by the National Swedish Environment Protection Board) is fairly good.

Comparison of optic disc topography in non-glaucomatous eyes of children with juvenile diabetes mellitus and normal children.

PubMed

Elgin, Ufuk; Cankaya, Bülent; Simsek, Tulay; Batman, Aygen

2010-01-01

To compare the optic disc topography parameters of children with juvenile diabetes mellitus and normal children using the Heidelberg Retinal Tomograph (HRT III) (Heidelberg Engineering, Heidelberg, Germany). The topographic optic disc parameters (cup volume, cup area, rim volume, rim area, disc area, mean cup-to-disc ratio, and mean cup depth) of 28 non-glaucomatous eyes of 28 children with type 1 diabetes mellitus and 28 eyes of 28 age-matched healthy children were compared using the nonparametric Mann-Whitney U test. No statistically significant differences were found between cup volume (P = .782), cup area (P = .878), rim volume (P = .853), disc area (P = .452), mean cup-to-disc ratio (P = .852), and mean cup depth (P = .711) of eyes of cases with diabetes mellitus and normal subjects. This result suggests that non-glaucomatous eyes of children with type 1 diabetes mellitus and healthy subjects have similar topographic optic disc characteristics. Copyright 2010, SLACK Incorporated.

Joint optic disc and cup boundary extraction from monocular fundus images.

PubMed

Chakravarty, Arunava; Sivaswamy, Jayanthi

2017-08-01

Accurate segmentation of optic disc and cup from monocular color fundus images plays a significant role in the screening and diagnosis of glaucoma. Though optic cup is characterized by the drop in depth from the disc boundary, most existing methods segment the two structures separately and rely only on color and vessel kink based cues due to the lack of explicit depth information in color fundus images. We propose a novel boundary-based Conditional Random Field formulation that extracts both the optic disc and cup boundaries in a single optimization step. In addition to the color gradients, the proposed method explicitly models the depth which is estimated from the fundus image itself using a coupled, sparse dictionary trained on a set of image-depth map (derived from Optical Coherence Tomography) pairs. The estimated depth achieved a correlation coefficient of 0.80 with respect to the ground truth. The proposed segmentation method outperformed several state-of-the-art methods on five public datasets. The average dice coefficient was in the range of 0.87-0.97 for disc segmentation across three datasets and 0.83 for cup segmentation on the DRISHTI-GS1 test set. The method achieved a good glaucoma classification performance with an average AUC of 0.85 for five fold cross-validation on RIM-ONE v2. We propose a method to jointly segment the optic disc and cup boundaries by modeling the drop in depth between the two structures. Since our method requires a single fundus image per eye during testing it can be employed in the large-scale screening of glaucoma where expensive 3D imaging is unavailable. Copyright © 2017 Elsevier B.V. All rights reserved.

Computer Mapping of Water Quality in Saginaw Bay with LANDSAT Digital Data

NASA Technical Reports Server (NTRS)

Rogers, R. H. (Principal Investigator); Shah, N. J.; Smith, V. E.; Mckeon, J. B.

1976-01-01

The author has identified the following significant results. LANDSAT digital data and ground truth measurements for Saginaw Bay (Lake Huron), Michigan, for 31 July 1975 were correlated by stepwise linear regression and the resulting equations used to estimate invisible water quality parameters in nonsampled areas. Chloride, conductivity, total Kjeldahl nitrogen, total phosphorus, and chlorophyll a were best correlated with the ratio of LANDSAT Band 4 to Band 5. Temperature and Secchi depth correlate best with Band 5.

Water-quality data for Smith and Bybee Lakes, Portland, Oregon, June to November, 1982

USGS Publications Warehouse

Clifton, Daphne G.

1983-01-01

Water-quality monitoring at Smith and Bybee Lakes included measurement of water temperature, dissolved oxygen concentration and percent saturation, pH, specific conductance, lake depth, alkalinity, dissolved carbon, total dissolved solids, secchi disk light transparency, nutrients, and chlorophyll a and b. In addition, phytoplankton, zooplankton, and benthic invertebrate populations were identified and enumerated. Lakebed sediment was analyzed for particle size, volatile solids, immediate oxygen demand, trace metals, total organic carbon, nutrients, and organic constituents. (USGS)

Tres Marias Reservoir, Minas Gerais State: Study of the dispersion of suspended sediments in surface waters using orbital images

NASA Technical Reports Server (NTRS)

Dejesusparada, N. (Principal Investigator); Sausen, T. M.

1980-01-01

Computer compatible tapes from LANDSAT were used to compartmentalize the Ires Marias reservoir according to respective grey level spectral response. Interactive and automatic, supervised classification, was executed from the IMAGE-100 system. From the simple correlation analysis and graphic representation, it is shown that grey tone levels are inversely proportional to Secchi Depth values. It is further shown that the most favorable period to conduct an analysis of this type is during the rainy season.

Trophic state in Voyageurs National Park lakes before and after implementation of a revised water-level management plan

USGS Publications Warehouse

Christensen, Victoria G.; Maki, Ryan P.

2015-01-01

We compiled Secchi depth, total phosphorus, and chlorophyll a (Chla) data from Voyageurs National Park lakes and compared datasets before and after a new water-level management plan was implemented in January 2000. Average Secchi depth transparency improved (from 1.9 to 2.1 m, p = 0.020) between 1977-1999 and 2000-2011 in Kabetogama Lake for August samples only and remained unchanged in Rainy, Namakan, and Sand Point Lakes, and Black Bay in Rainy Lake. Average open-water season Chla concentration decreased in Black Bay (from an average of 13 to 6.0 μg/l, p = 0.001) and Kabetogama Lake (from 9.9 to 6.2 μg/l, p = 0.006) between 1977-1999 and 2000-2011. Trophic state index decreased significantly in Black Bay from 59 to 51 (p = 0.006) and in Kabetogama Lake from 57 to 50 (p = 0.006) between 1977-1999 and 2000-2011. Trophic state indices based on Chla indicated that after 2000, Sand Point, Namakan, and Rainy Lakes remained oligotrophic, whereas eutrophication has decreased in Kabetogama Lake and Black Bay. Although nutrient inputs from inflows and internal sources are still sufficient to produce annual cyanobacterial blooms and may inhibit designated water uses, trophic state has decreased for Kabetogama Lake and Black Bay and there has been no decline in lake ecosystem health since the implementation of the revised water-level management plan.

Deep-down ionization of protoplanetary discs

NASA Astrophysics Data System (ADS)

Glassgold, A. E.; Lizano, S.; Galli, D.

2017-12-01

The possible occurrence of dead zones in protoplanetary discs subject to the magneto-rotational instability highlights the importance of disc ionization. We present a closed-form theory for the deep-down ionization by X-rays at depths below the disc surface dominated by far-ultraviolet radiation. Simple analytic solutions are given for the major ion classes, electrons, atomic ions, molecular ions and negatively charged grains. In addition to the formation of molecular ions by X-ray ionization of H2 and their destruction by dissociative recombination, several key processes that operate in this region are included, e.g. charge exchange of molecular ions and neutral atoms and destruction of ions by grains. Over much of the inner disc, the vertical decrease in ionization with depth into the disc is described by simple power laws, which can easily be included in more detailed modelling of magnetized discs. The new ionization theory is used to illustrate the non-ideal magnetohydrodynamic effects of Ohmic, Hall and Ambipolar diffusion for a magnetic model of a T Tauri star disc using the appropriate Elsasser numbers.

Geometry of the intervertebral volume and vertebral endplates of the human spine.

PubMed

van der Houwen, E B; Baron, P; Veldhuizen, A G; Burgerhof, J G M; van Ooijen, P M A; Verkerke, G J

2010-01-01

Replacement of a degenerated vertebral disc with an artificial intervertebral disc (AID) is currently possible, but poses problems, mainly in the force distribution through the vertebral column. Data on the intervertebral disc space geometry will provide a better fit of the prosthesis to the vertebrae, but current literature on vertebral disc geometry is very scarce or not suitable. In this study, existing CT-scans of 77 patients were analyzed to measure the intervertebral disc and vertebral endplate geometry of the lumbar spine. Ten adjacent points on both sides of the vertebrae (S1-superior to T12-inferior) and sagittal and transverse diameters were measured to describe the shape of the caudal and cranial vertebral planes of the vertebrae. It was found that the largest endplate depth is located in the middle or posterior regions of the vertebra, that there is a linear relationship between all inferior endplate depths and the endplate location (p < 0.0001) within the spinal column, and that the superior endplate depth increases with age by about 0.01 mm per year (p < 0.02). The wedge angle increases from T12-L1 to L5-S1. The results allow for improvement of the fit of intervertebral disc-prostheses to the vertebrae and optimized force transmission through the vertebral column.

Planet-disc interaction in laminar and turbulent discs

NASA Astrophysics Data System (ADS)

Stoll, Moritz H. R.; Picogna, Giovanni; Kley, Wilhelm

2017-07-01

In weakly ionised discs turbulence can be generated through the vertical shear instability (VSI). Embedded planets are affected by a stochastic component in the torques acting on them, which can impact their migration. In this work we study the interplay between a growing planet embedded in a protoplanetary disc and the VSI turbulence. We performed a series of 3D hydrodynamical simulations for locally isothermal discs with embedded planets in the mass range from 5 to 100 Earth masses. We study planets embedded in an inviscid disc that is VSI unstable, becomes turbulent, and generates angular momentum transport with an effective α = 5 × 10-4. This is compared to the corresponding viscous disc using exactly this α-value. In general we find that the planets have only a weak impact on the disc turbulence. Only for the largest planet (100 M⊕) does the turbulent activity become enhanced inside of the planet. The depth and width of a gap created by the more massive planets (30,100 M⊕) in the turbulent disc equal exactly that of the corresponding viscous case, leading to very similar torque strengths acting on the planet, with small stochastic fluctuations for the VSI disc. At the gap edges vortices are generated that are stronger and longer-lived in the VSI disc. Low mass planets (with Mp ≤ 10 M⊕) do not open gaps in the disc in either case, but generate for the turbulent disc an overdensity behind the planet that exerts a significant negative torque. This can boost the inward migration in VSI turbulent discs well above the Type I rate. Owing to the finite turbulence level in realistic 3D discs the gap depth will always be limited and migration will not stall in inviscid discs.

Biotic and abiotic factors influencing zooplankton vertical distribution in Lake Huron

USGS Publications Warehouse

Nowicki, Carly J.; Bunnell, David B.; Armenio, Patricia M.; Warner, David M.; Vanderploeg, Henry A.; Cavaletto, Joann F.; Mayer, Christine M.; Adams, Jean V.

2017-01-01

The vertical distribution of zooplankton can have substantial influence on trophic structure in freshwater systems, particularly by determining spatial overlap for predator/prey dynamics and influencing energy transfer. The zooplankton community in some of the Laurentian Great Lakes has undergone changes in composition and declines in total biomass, especially after 2003. Mechanisms underlying these zooplankton changes remain poorly understood, in part, because few studies have described their vertical distributions during daytime and nighttime conditions or evaluated the extent to which predation, resources, or environmental conditions could explain their distribution patterns. Within multiple 24-h periods during July through October 2012 in Lake Huron, we conducted daytime and nighttime sampling of zooplankton, and measured food (chlorophyll-a), temperature, light (Secchi disk depth), and planktivory (biomass of Bythotrephes longimanus and Mysis diluviana). We used linear mixed models to determine whether the densities for 22 zooplankton taxa varied between day and night in the epi-, meta-, and hypolimnion. For eight taxa, higher epilimnetic densities were observed at night than during the day; general linear models revealed these patterns were best explained by Mysis diluviana (four taxa), Secchi disk depth (three taxa), epilimnetic water temperature (three taxa), chlorophyll (one taxon), and biomass of Bythotrephes longimanus (one taxon). By investigating the potential effects of both biotic and abiotic variables on the vertical distribution of crustacean zooplankton and rotifers, we provide descriptions of the Lake Huron zooplankton community and discuss how future changes in food web dynamics or climate change may alter zooplankton distribution in freshwater environments.

Combining lake and watershed characteristics with Landsat TM data for remote estimation of regional lake clarity

USGS Publications Warehouse

McCullough, Ian M.; Loftin, Cyndy; Sader, Steven A.

2012-01-01

Water clarity is a reliable indicator of lake productivity and an ideal metric of regional water quality. Clarity is an indicator of other water quality variables including chlorophyll-a, total phosphorus and trophic status; however, unlike these metrics, clarity can be accurately and efficiently estimated remotely on a regional scale. Remote sensing is useful in regions containing a large number of lakes that are cost prohibitive to monitor regularly using traditional field methods. Field-assessed lakes generally are easily accessible and may represent a spatially irregular, non-random sample of a region. We developed a remote monitoring program for Maine lakes >8 ha (1511 lakes) to supplement existing field monitoring programs. We combined Landsat 5 Thematic Mapper (TM) and Landsat 7 Enhanced Thematic Mapper Plus (ETM+) brightness values for TM bands 1 (blue) and 3 (red) to estimate water clarity (secchi disk depth) during 1990–2010. Although similar procedures have been applied to Minnesota and Wisconsin lakes, neither state incorporates physical lake variables or watershed characteristics that potentially affect clarity into their models. Average lake depth consistently improved model fitness, and the proportion of wetland area in lake watersheds also explained variability in clarity in some cases. Nine regression models predicted water clarity (R2 = 0.69–0.90) during 1990–2010, with separate models for eastern (TM path 11; four models) and western Maine (TM path 12; five models that captured differences in topography and landscape disturbance. Average absolute difference between model-estimated and observed secchi depth ranged 0.65–1.03 m. Eutrophic and mesotrophic lakes consistently were estimated more accurately than oligotrophic lakes. Our results show that TM bands 1 and 3 can be used to estimate regional lake water clarity outside the Great Lakes Region and that the accuracy of estimates is improved with additional model variables that reflect physical lake characteristics and watershed conditions.

Computer mapping of turbidity and circulation patterns in Saginaw Bay, Michigan from LANDSAT data

NASA Technical Reports Server (NTRS)

Rogers, R. H. (Principal Investigator); Reed, L. E.; Smith, V. E.

1975-01-01

The author has identified the following significant results. LANDSAT was used as a basis for producing geometrically-corrected, color-coded imagery of turbidity and circulation patterns in Saginaw Bay, Michigan (Lake Huron). This imagery shows nine discrete categories of turbidity, as indicated by nine Secchi depths between 0.3 and 3.3 meters. The categorized imagery provided an economical basis for extrapolating water quality parameters from point samples to unsample areas. LANDSAT furnished a synoptic view of water mass boundaries that no amount of ground sampling or monitoring could provide.

Landsat Thematic Mapper monitoring of turbid inland water quality

NASA Technical Reports Server (NTRS)

Lathrop, Richard G., Jr.

1992-01-01

This study reports on an investigation of water quality calibration algorithms under turbid inland water conditions using Landsat Thematic Mapper (TM) multispectral digital data. TM data and water quality observations (total suspended solids and Secchi disk depth) were obtained near-simultaneously and related using linear regression techniques. The relationships between reflectance and water quality for Green Bay and Lake Michigan were compared with results for Yellowstone and Jackson Lakes, Wyoming. Results show similarities in the water quality-reflectance relationships, however, the algorithms derived for Green Bay - Lake Michigan cannot be extrapolated to Yellowstone and Jackson Lake conditions.

Application of remote sensing for fishery resources assessment and monitoring. [Gulf of Mexico

NASA Technical Reports Server (NTRS)

Savastano, K. J. (Principal Investigator)

1975-01-01

The author has identified the following significant results. The distribution and abundance of white marlin correlated with the chlorophyll, water temperature, and Secchi depth sea truth measurements. Results of correlation analyses for dolphin were inconclusive. Predicition models for white marlin were developed using stepwise multiple regression and discriminant function analysis techniques which demonstrated a potential for increasing the probability of game fishing success. The S190A and B imagery was density sliced/color enhanced with white marlin location superimposed on the image, but no density/white marlin relationship could be established.

Data on the distribution and abundance of submersed aquatic vegetation in the tidal Potomac River, Maryland, Virginia, and the District of Columbia, 1985

USGS Publications Warehouse

Rybicki, N.B.; Anderson, R.T.; Shapiro, J.M.; Jones, C.L.; Carter, Virginia

1986-01-01

This report summarizes data on the distribution and abundance of submersed aquatic vegetation collected in the tidal Potomac River during 1985. Plant species were identified and dry weight determined for selected sites. Information on competition between Hydrilla verticillata and other species was measured. Water-quality characteristics measured include temperature, specific conductance, dissolved oxygen, pH, and transparency as indicated by Secchi depth. A map was made of the distribution of submersed aquatic vegetation based on transect samples and a complete shoreline survey. (USGS)

Seasonal dynamics of dissolved, particulate and microbial components of a tidal saltmarsh-dominated estuary under contrasting levels of freshwater discharge

NASA Astrophysics Data System (ADS)

Bittar, Thais B.; Berger, Stella A.; Birsa, Laura M.; Walters, Tina L.; Thompson, Megan E.; Spencer, Robert G. M.; Mann, Elizabeth L.; Stubbins, Aron; Frischer, Marc E.; Brandes, Jay A.

2016-12-01

Tidal Spartina-dominated saltmarshes and estuaries on the Southeast US coast are global hotspots of productivity. In coastal Georgia, tidal amplitudes and saltmarsh productivity are the highest along the Southeast US coast. Coastal Georgia is characterized by a humid subtropical seasonal climate, and inter-annual variability in precipitation, and freshwater discharge. The 2012-2013 timeframe encompassed contrasting levels of discharge for the Savannah River, a major Georgia river, with a 4.3-fold greater discharge in summer 2013 relative to summer 2012. In situ measurements of temperature, salinity, precipitation and Secchi depth, and water samples were collected weekly at high tide throughout 2012 and 2013 from the Skidaway River Estuary, a tidal saltmarsh-dominated estuary in coastal Georgia influenced by Savannah River hydrology. The effects of elevated discharge on the seasonal trends of water column components were evaluated. The shift from low discharge (2012) to high discharge (2013) led to decreased salinity in summer 2013, but no significant increases in inorganic nutrient (NH4, NOx, SiO2 and PO4) concentrations. Dissolved inorganic carbon (DIC) concentrations decreased, and DIC stable isotopic signatures (δ13C-DIC values) were depleted in summer 2013 relative to summer 2012. In 2013 dissolved organic carbon (DOC) concentrations, chromophoric and fluorescent dissolved organic matter (DOM: CDOM, FDOM) intensities, specific UV-absorbance (SUVA254) and relative humic-like fluorescence were all higher than in 2012, indicating that, as discharge increased in 2013, estuarine water became enriched in terrigenous DOM. Secchi depth and particulate organic carbon (POC) and nitrogen (PON) concentrations displayed clear seasonal patterns that were not significantly altered by discharge. However, δ13C-POC and δ15N-PON isotopic signatures indicated higher terrigenous contributions at elevated discharge. Discharge influenced cyanobacterial composition, but did not affect total abundance of phytoplankton (<52 μm) or chlorophyll-a concentrations, a proxy for phytoplankton biomass. Phytoplankton community dynamics were primarily seasonally-driven. Bacterioplankton abundance and community composition, based upon flow cytometry, were affected by discharge, possibly due to decreased salinity and/or increased inputs of terrigenous DOM. Seasonal patterns in inorganic nutrient, POC, PON and chlorophyll-a concentrations, and Secchi depth were not significantly influenced by the 2013 increase in discharge. For other components, most notably δ13C-DIC values, DOM and bacterioplankton, the influence of increased discharge in 2013 was superimposed upon their seasonal patterns. This study showed that in addition to tidal mixing and in situ saltmarsh and estuarine production and removal processes, the level of riverine freshwater discharge impacted the quantity and character of many water column components in this tidal saltmarsh ecosystem.

Full-Scale Linear Cutting Tests in Chongqing Sandstone to Study the Influence of Confining Stress on Rock Cutting Forces by TBM Disc Cutter

NASA Astrophysics Data System (ADS)

Pan, Yucong; Liu, Quansheng; Liu, Jianping; Peng, Xingxin; Kong, Xiaoxuan

2018-06-01

In order to study the influence of confining stress on rock cutting forces by tunnel boring machine (TBM) disc cutter, full-scale linear cutting tests are conducted in Chongqing Sandstone (uniaxial compressive strength 60.76 MPa) using five equal biaxial confining stressed conditions, i.e. 0-0, 5-5, 10-10, 15-15 and 20-20 MPa; disc cutter normal force, rolling force, cutting coefficient and normalized resultant force are analysed. It is found that confining stress can greatly affect disc cutter resultant force, its proportion in normal and rolling directions and its acting point for the hard Chongqing Sandstone and the confining stress range used in this study. For every confining stressed condition, as cutter penetration depth increases, disc cutter normal force increases with decreasing speed, rolling force and cutting coefficient both increase linearly, and acting point of the disc cutter resultant force moves downward at some extent firstly and then upward back to its initial position. For same cutter penetration depth, as confining stress increases, disc cutter normal force, rolling force, cutting coefficient and normalized resultant force all increase at some extent firstly and then decrease rapidly to very small values (quite smaller than those obtained under the non-stressed condition) after some certain confining stress thresholds. The influence of confining stress on rock cutting by TBM disc cutter can be generally divided into three stages as confining stress increases, i.e. strengthening effect stage, damaging effect stage and rupturing effect stage. In the former two stages (under low confining stress), rock remains intact and rock cutting forces are higher than those obtained under the non-stressed condition, and thus rock cutting by TBM disc cutter is restrained; in the last stage (under high confining stress), rock becomes non-intact and rock slabbing failure is induced by confining stress before disc cutting, and thus rock cutting by TBM disc cutter is facilitated. Meanwhile, some critical values of confining stress and cutter penetration depth are identified to represent the changes of rock cutting state. This study provides better understanding of the influence of confining stress on disc cutter performance and can guide to optimize the TBM operation under stressed condition.

Morphological Features and Important Parameters of Large Optic Discs for Diagnosing Glaucoma

PubMed Central

Okimoto, Satoshi; Yamashita, Keiko; Shibata, Tetsuo; Kiuchi, Yoshiaki

2015-01-01

Purpose To compare the optic disc parameters of glaucomatous eyes to those of non-glaucomatous eyes with large discs. Methods We studied 225 consecutive eyes with large optic discs (>2.82 mm2): 91 eyes with glaucoma and 134 eyes without glaucoma. An eye was diagnosed with glaucoma when visual field defects were detected by the Humphrey Field Analyzer. All of the Heidelberg Retina Tomograph II (HRT II) parameters were compared between the non-glaucomatous and glaucomatous eyes. A logistic regression analysis of the HRT II parameters was used to establish a new formula for diagnosing glaucoma, and the sensitivity and specificity of the Moorfields Regression Analysis (MRA) was compared to the findings made by our analyses. Results The mean disc area was 3.44±0.50 mm2 in the non-glaucomatous group and 3.40±0.52 mm2 in the glaucoma group. The cup area, cup volume, cup-to-disc area ratio, linear cup/disc ratio, mean cup depth, and the maximum cup depth were significantly larger in glaucomatous eyes than in the non-glaucomatous eyes. The rim area, rim volume, cup shape measurement, mean retinal nerve fiber layer (RNFL) thickness, and RFNL cross-sectional area were significantly smaller in glaucomatous eyes than in non-glaucomatous eyes. The cup-to-disc area ratio, the height variation contour (HVC), and the RNFL cross-sectional area were important parameters for diagnosing the early stage glaucoma, and the cup-to-disc area ratio and cup volume were useful for diagnosing advanced stage glaucoma in eyes with a large optic disc. The new formula had higher sensitivity and specificity for diagnosing glaucoma than MRA. Conclusions The cup-to-disc area ratio, HVC, RNFL cross-sectional area, and cup volume were important parameters for diagnosing glaucoma in eyes with a large optic disc. The important disc parameters to diagnose glaucoma depend on the stage of glaucoma in patients with large discs. PMID:25798580

Light attenuation and submersed macrophyte distribution in the tidal Potomac River and estuary

USGS Publications Warehouse

Carter, V.; Rybicki, N.B.

1990-01-01

Changing light availability may be responsible for the discontinuous distribution of submersed aquatic macrophytes in the freshwater tidal Potomac River. During the 1985-1986 growing seasons, light attenuation and chlorophyll a and suspended particulate material concentrations were measured in an unvegetated reach (B) and in two adjacent vegetated reaches (A and C). Light attenuation in reach B (the lower, fresh to oligohaline tidal river) was greater than that in reach A (the recently revegetated, upper, freshwater tidal river) in both years. Reach B light attenuation was greater than that in reach C (the vegetated, oligohaline to mesohaline transition zone of the Potomac Estuary) in 1985 and similar to that in reach C in 1986. In reach B, 5% of total below-surface light penetrated only an average of 1.3 m in 1985 and 1.0m in 1986, compared with 1.9 m and 1.4 m in reach A in 1985 and 1986, respectively. Water column chlorophyll a concentration controlled light availability in reaches A and B in 1985, whereas both chlorophyll a and suspended particulate material concentrations were highly correlated with attenuation in both reaches in 1986. Reach C light attenuation was correlated with suspended particulate material in 1986. The relationship between attenuation coefficient and Secchi depth was KPAR=1.38/Secchi depth. The spectral distribution of light at 1 m was shifted toward the red portion of the visible spectrum compared to surface light. Blue light was virtually absent at 1.0 m in reach B during July and August 1986. Tidal range is probably an important factor in determining light availability for submersed macrophyte propagule survival at the sediment-water interface in this shallow turbid system. ?? 1990 Estuarine Research Federation.

Sensitivity and cost considerations for the detection and eradication of marine pests in ports.

PubMed

Hayes, Keith R; Cannon, Rob; Neil, Kerry; Inglis, Graeme

2005-08-01

Port surveys are being conducted in Australia, New Zealand and around the world to confirm the presence or absence of particular marine pests. The most critical aspect of these surveys is their sensitivity-the probability that they will correctly identify a species as present if indeed it is present. This is not, however, adequately addressed in the relevant national and international standards. Simple calculations show that the sensitivity of port survey methods is closely related to their encounter rate-the average number of target individuals expected to be detected by the method. The encounter rate (which reflects any difference in relative pest density), divided by the cost of the method, provides one way to compare the cost-effectiveness of different survey methods. The most cost-effective survey method is site- and species-specific but, in general, will involve sampling from the habitat with the highest expected population of target individuals. A case study of Perna viridis in Trinity Inlet, Cairns, demonstrates that plankton trawls processed with gene probes provide the same level of sensitivity for a fraction of the cost associated with the next best available method-snorkel transects in bad visibility (secchi depth=0.72 m). Visibility and the adult/larvae ratio, however, are critical to these arguments. If visibility were good (secchi depth=10 m), the two approaches would be comparable. Diver deployed quadrats were at least three orders of magnitude less cost-effective in this case study. It is very important that environmental managers and scientists perform sensitivity calculations before embarking on port surveys to ensure the highest level of sensitivity is achieved for any given budget.

Shifts in coastal fish communities: Is eutrophication always beneficial for sticklebacks?

NASA Astrophysics Data System (ADS)

Gagnon, Karine; Gräfnings, Max; Boström, Christoffer

2017-11-01

Following declines of predatory fish, mesopredators such as sticklebacks have been linked to shifts in coastal trophic networks through both top-down (preying on mesograzers and facilitating algal blooms) and bottom-up (benefitting from eutrophicated conditions) processes. Here, we tested whether the association between eutrophication effects (filamentous algae and turbidity) and sticklebacks held true in the Finnish Archipelago Sea where predatory fish populations have remained stable. If so, sticklebacks should be more abundant in the middle archipelago, where eutrophic conditions have led to increased turbidity, higher filamentous algal loads, and decreased cover of submerged aquatic vegetation (SAV), than in the outer archipelago, where environmental conditions are better. We measured the spatial and seasonal variation of sticklebacks (three-spined Gasterosteus aculeatus and nine-spined Pungitius pungitius) in middle and outer archipelago sites, as well as environmental variables potentially affecting their abundance. Adults and juveniles of both species were more abundant in the outer than middle archipelago. The outer archipelago was characterized by greater Secchi depth throughout the summer and higher SAV cover in late summer. Secchi depth was positively correlated with stickleback abundance of both species, while SAV cover was also positively correlated in late summer. Filamentous algal cover was high in both the middle and outer archipelago, but not consistently associated with stickleback abundance throughout the summer. While sticklebacks have been thought to both contribute to, and benefit from, eutrophication, our results instead suggest that the resulting environmental changes may have adverse effects on sticklebacks, especially if predators are present. This may lead them to shift their breeding grounds and spatial distribution to less eutrophicated areas where lower turbidity and the resulting increased availability of SAV provide refuge from predators for juveniles, and higher quality breeding and feeding grounds for adults.

The Effect of Ambient Water Quality on Lakefront Property Values: Evidence from Coeur d'Alene, Idaho

NASA Astrophysics Data System (ADS)

Liao, H.

2015-12-01

Climate warming is causing water temperatures to increase and subsequent changes in water quality. To develop innovative approaches for mitigating the possible negative social consequences of such changes, more research efforts are needed to investigate how people perceive and respond to ambient water quality. This research examines the amenity value of water quality in the areas centered on Lake Coeur d'Alene of Northern Idaho. Through a hedonic analysis, we find that two important water-quality variables have had significant effects on lakefront property values, including Secchi disc reading, a technical measure of water clarity, and the presence of Eurasian watermilfoil, an aquatic invasive species. We further explore the spatial heterogeneity of water-quality benefits along the urban-rural gradient and find that access to urban amenities has strengthened the water-quality benefits in the lakefront housing market. Our findings could be used to incentivize private property owners and stakeholders to commit time and funding to cope with the potential degradation of water quality under climate change.

Balancing lake ecological condition and agriculture irrigation needs in the Mississippi Alluvial Valley

USGS Publications Warehouse

Miranda, Leandro E.; Omer, A.R.; Killgore, K.J.

2017-01-01

The Mississippi Alluvial Valley includes hundreds of floodplain lakes that support unique fish assemblages and high biodiversity. Irrigation practices in the valley have lowered the water table, increasing the cost of pumping water, and necessitating the use of floodplain lakes as a source of water for irrigation. This development has prompted the need to regulate water withdrawals to protect aquatic resources, but it is unknown how much water can be withdrawn from lakes before ecological integrity is compromised. To estimate withdrawal limits, we examined descriptors of lake water quality (i.e., total nitrogen, total phosphorus, turbidity, Secchi visibility, chlorophyll-a) and fish assemblages (species richness, diversity, composition) relative to maximum depth in 59 floodplain lakes. Change-point regression analysis was applied to identify critical depths at which the relationships between depth and lake descriptors exhibited a rapid shift in slope, suggesting possible thresholds. All our water quality and fish assemblage descriptors showed rapid changes relative to depth near 1.2–2.0 m maximum depth. This threshold span may help inform regulatory decisions about water withdrawal limits. Alternatives to explain the triggers of the observed threshold span are considered.

Measurement of Optic Disc Cup Surface Depth Using Cirrus HD-OCT.

PubMed

Kim, Young Kook; Ha, Ahnul; Lee, Won June; Jeoung, Jin Wook; Park, Ki Ho

2017-12-01

To introduce the measurement method of optic disc cup surface depth using spectral-domain optical coherence tomography (SD-OCT) and then evaluate the rates of cup surface depression at 3 different stages of glaucoma. We retrospectively identified 52 eyes with preperimetric glaucoma, 56 with mild-or-moderate glaucoma and 50 with severe glaucoma and followed them for at least 48 months. Eyes were imaged using SD-OCT (Cirrus HD-OCT) at 12-month intervals. The mean cup surface depth was calculated using the following formula: Cup volume/(disc area×average cup-to-disc ratio)-200 μm. The rates of mean cup surface depression (μm/y) were significantly greater in mild-or-moderate glaucoma (-7.96±1.03) than in preperimetric (-3.11±0.61) and severe glaucoma (-0.70±0.12; all P<0.001). The percentile rates of mean cup surface depression (%/y) were significantly greater than those of average of retinal nerve fiber layer (RNFL) thinning (%/y) in preperimetric glaucoma (-1.64±0.12 vs. -1.11±0.07; P<0.001) and mild-or-moderate glaucoma (-4.20±0.33 vs. -3.14±0.19; P<0.001); and conversely, in severe glaucoma, mean cup surface depth changed slower than did average RNFL thickness (-0.64±0.06 vs. -0.75±0.08%/y; P<0.001). In early-to-moderate glaucoma, the cup surface depth changed faster than did the RNFL thickness. These results signify the possibility that SD-OCT-based estimation of cup surface depth might be useful for monitoring of glaucoma development and progression.

Diffusion on Viscous Fluids, Existence and Asymptotic Properties of Solutions,

DTIC Science & Technology

1983-09-01

Matematica - Politecuico di Milano (1982). 11.* P. Secchi "On the Initial Value ProbleM for the Nquations of Notion of Viscous Incompressible Fluids In...of two viscous Incompressible Fluids’, preprint DepartLmento dl matematica - Politecuico di Milano (1982). -15- 11. P. Secchi 00n the XnitiaI Value

Eutrophication of Lake Tasaul, Romania-proposals for rehabilitation.

PubMed

Alexandrov, Mihaela Laurenta; Bloesch, Jürg

2009-08-01

Lake Tasaul on the Black Sea coast is highly eutrophic, but not strongly contaminated (heavy metals, PAHs, and organochlorine pesticides). Cyanophytes dominate phytoplankton by 67-94% and form frequent algal blooms. High primary production (up to 270 mg C(ass)/m(2).h) and algal biomass (maximum chlorophyll a concentration 417 microg/l) may be controlled by light, as Secchi depth is often below 1 m. The main tributary, Casimcea River, provides high quantities of suspended matter and about 3 tons TP/year and 660 tons TN/year. Based on chemical and biological analysis as well as fishery investigations, we provide recommendations for Lake Tasaul rehabilitation.

Valuable water

NASA Astrophysics Data System (ADS)

Carlowicz, Michael

In some places, money flows with water. Studying both the water quality and property values around 22 lakes in south-central Maine, Kevin Boyle and Holly James of the University of Maine and Roy Bouchard of the Maine Department of Environmental Protection have found that good water quality makes waterfront property even more valuable. To gauge water quality, the researchers used Secchi disks to measure the clarity of the water at depth. They also reviewed 543 lakefront property sales between 1990 and 1994 to determine how values correlated with changing water conditions. The group also considered such factors as lake frontage, sizes of the houses and lots, and size of the lake.

Determination of cup-to-disc ratio of optical nerve head for diagnosis of glaucoma on stereo retinal fundus image pairs

NASA Astrophysics Data System (ADS)

Muramatsu, Chisako; Nakagawa, Toshiaki; Sawada, Akira; Hatanaka, Yuji; Hara, Takeshi; Yamamoto, Tetsuya; Fujita, Hiroshi

2009-02-01

A large cup-to-disc (C/D) ratio, which is the ratio of the diameter of the depression (cup) to that of the optical nerve head (ONH, disc), can be one of the important signs for diagnosis of glaucoma. Eighty eyes, including 25 eyes with the signs of glaucoma, were imaged by a stereo retinal fundus camera. An ophthalmologist provided the outlines of cup and disc on a regular monitor and on the stereo display. The depth image of the ONH was created by determining the corresponding pixels in a pair of images based on the correlation coefficient in localized regions. The areas of the disc and cup were determined by use of the red component in one of the color images and by use of the depth image, respectively. The C/D ratio was determined based on the largest vertical lengths in the cup and disc areas, which was then compared with that by the ophthalmologist. The disc areas determined by the computerized method agreed relatively well with those determined by the ophthalmologist, whereas the agreement for the cup areas was somewhat lower. When C/D ratios were employed for distinction between the glaucomatous and non-glaucomatous eyes, the area under the receiver operating characteristic curve (AUC) was 0.83. The computerized analysis of ONH can be useful for diagnosis of glaucoma.

Contribution to a bio-optical model for remote sensing of Lena River water

NASA Astrophysics Data System (ADS)

Örek, H.; Doerffer, R.; Röttgers, R.; Boersma, M.; Wiltshire, K. H.

2013-11-01

Bio-optical measurements and sampling were carried out in the delta of the Lena River (northern Siberia, Russia) between 26 June and 4 July 2011. The aim of this study was to determine the inherent optical properties of the Lena water, i.e., absorption, attenuation, and scattering coefficients, during the period of maximum runoff. This aimed to contribute to the development of a bio-optical model for use as the basis for optical remote sensing of coastal water of the Arctic. In this context the absorption by CDOM (colored dissolved organic matter) and particles, and the concentrations of total suspended matter, phytoplankton-pigments, and carbon were measured. CDOM was found to be the most dominant parameter affecting the optical properties of the river, with an absorption coefficient of 4.5-5 m-1 at 442 nm, which was almost four times higher than total particle absorption values at visible wavelength range. The wavelenght-dependence of absorption of the different water constituents was chracterized by determining the semi logarithmic spectral slope. Mean CDOM, and detritus slopes were 0.0149 nm-1(standard deviation (stdev) = 0.0003, n = 18), and 0.0057 nm-1 (stdev = 0.0017, n = 19), respectively, values which are typical for water bodies with high concentrations of dissolved and particulate carbon. Mean chlorophyll a and total suspended matter were 1.8 mg m-3 (stdev = 0.734 n = 18) and 31.9 g m-3 (stdev = 19.94, n = 27), respectively. DOC (dissolved organic carbon) was in the range 8-10 g m-3 and the total particulate carbon (PC) in the range 0.25-1.5 g m-3. The light penetration depth (Secchi disc depth) was in the range 30-90 cm and was highly correlated with the suspended matter concentration. The period of maximum river runoff in June was chosen to obtain bio-optical data when maximum water constituents are transported into the Laptev Sea. However, we are aware that more data from other seasons and other years need to be collected to establish a general bio-optical model of the Lena water and conclusively characterize the light climate with respect to primary production.

Spectral analysis of the Forel-Ule Ocean colour comparator scale

NASA Astrophysics Data System (ADS)

Wernand, M. R.; van der Woerd, H. J.

2010-04-01

François Alphonse Forel (1890) and Willi Ule (1892) composed a colour comparator scale, with tints varying from indigo-blue to coca-cola brown, to quantify the colour of natural waters, like seas, lakes and rivers. For each measurement, the observer compares the colour of the water above a submersed white disc (Secchi disc) with the hand-held scale of pre-defined colours. The scale can be well reproduced from a simple recipe for twenty-one coloured chemical solutions and because the ease of its use, the Forel-Ule (FU) scale has been applied globally and intensively by oceanographers and limnologists from the year 1890. Indeed, the archived FU data belong to the oldest oceanographic data sets and do contain information on the changes in geobiophysical properties of natural waters during the last century. In this article we describe the optical properties of the FU-scale and its ability to cover the colours of natural waters, as observed by the human eye. The recipe of the scale and its reproduction is described. The spectral transmission of the tubes, with belonging chromaticity coordinates, is presented. The FU scale, in all its simplicity, is found to be an adequate ocean colour comparator scale. The scale is well characterized, is stable and observations are reproducible. This supports the idea that the large historic data base of FU measurements is coherent and well calibrated. Moreover, the scale can be coupled to contemporary multi-spectral observations with hand-held and satellite-based spectrometers.

STEREO SECCHI and S/WAVES Observations of Spacecraft Debris Caused by Micron-Size Interplanetary Dust Impacts

NASA Astrophysics Data System (ADS)

St. Cyr, O. C.; Kaiser, M. L.; Meyer-Vernet, N.; Howard, R. A.; Harrison, R. A.; Bale, S. D.; Thompson, W. T.; Goetz, K.; Maksimovic, M.; Bougeret, J.-L.; Wang, D.; Crothers, S.

2009-05-01

Early in the STEREO mission observers noted that the white-light instruments of the SECCHI suite were detecting significantly more spacecraft-related “debris” than any previously flown coronagraphic instruments. Comparison of SECCHI “debris storms” with S/WAVES indicates that almost all are coincident with the most intense transient emissions observed by the radio and plasma waves instrument. We believe the debris is endogenous ( i.e., from the spacecraft thermal blanketing), and the storms appear to be caused by impacts of large interplanetary dust grains that are detected by S/WAVES. Here we report the observations, compare them to interplanetary dust distributions, and document a reminder for future spacebased coronagraphic instrument builders.

Design and experiment on 2KF-15 type disc cutter and shallow fertilization machine in rubber plantation

NASA Astrophysics Data System (ADS)

Deng, Yiguo; Zhang, Yuan; Wang, Yeqin

2017-12-01

At present, the trenching and fertilization machine has a serious weed plug problem when trenching and fertilization operation in rubber plantation. So a disc cutter and shallow fertilization machine in rubber plantation named 2KF-15 was designed, the design scheme used the front disc cutter cutting the grass, while using the rear of the disc furrow to trenching, the prototype of a disc anti-plugging trenching and shallow fertilization machine was completed. Afterwards, a series of trenching and fertilization field experiments were carried out, and the results showed that the ditching depth of this machine could achieve from 131 to 176 mm, and the average depth could reach 156 mm, the ditching depth stability coefficient could achieve 90.3%; The fertilizer amount of this machine could achieve from 113.2 to 156.4 kg/hm2, the average fertilizer amount reach 134.2kg/hm2, the fertilizer amount stability coefficient could achieve 89.6%, the fertilizer broken rate was 0%, the fertilizer coverage rate of 98.4%;The situation of fertilizer accumulation occurred less by using this machine, and the fertilization performance was relatively stable. This new designed machine for trenching, fertilization and covering the soil were carried out at the same time. So the number of operations could be effectively reduced. This new designed machine does not only meet the agronomic requirements of rubber plantation fertilization, but also provides a reference for the trenching and fertilization operation in other.

Utilizing Depth of Colonization of Seagrasses to Develop ...

EPA Pesticide Factsheets

US EPA is working with state and local partners in Florida to develop numeric water quality criteria to protect estuaries from nutrient pollution. Similar to other nutrient management programs in Florida, EPA is considering status of seagrass habitats as an indicator of biological integrity, with depth of colonization of seagrasses used to relate potential seagrass extent to water quality requirements (especially water clarity). We developed and validated an automated methodology for evaluating depth of colonization and applied it to generate 228 estimates of seagrass colonization depth for coverage years spanning 67 years (1940-2007) in a total of 100 segments within 19 estuarine and coastal areas in Florida. A validation test showed that two parameters that were computed, Zc50 and ZcMax, approximated the average and 95th percentile depth at the deep-water margin of seagrass beds. Zc50 was estimated separately for continuous seagrass vs. all seagrass. Average values for Zc50 as well as long-term trends were evaluated for the entire state, illustrating a decline on average from early years (e.g., 1940-1953) to a middle period (1982-1999) and a variable degree of recovery since 2000. The largest decrease in Zc50 occurred in Florida panhandle estuaries. Extensive water quality data compiled in the Florida DEP’s Impaired Waters Rule database was evaluated to characterize Secchi depth, CDOM, TSS, and chlorophyll-a in relation to depth of colonization estima

Enhance field water-color measurements with a Secchi disk and its implication for fusion of active and passive ocean-color remote sensing.

PubMed

Lee, Zhongping; Shang, Shaoling; Du, Keping; Liu, Bingyi; Lin, Gong; Wei, Jianwei; Li, Xiaolong

2018-05-01

Inversion of the total absorption (a) and backscattering coefficients of bulk water through a fusion of remote sensing reflectance (R rs ) and Secchi disk depth (Z SD ) is developed. An application of such a system to a synthesized wide-range dataset shows a reduction of ∼3 folds in the uncertainties of inverted a(λ) (in a range of ∼0.01-6.8  m -1 ) from R rs (λ) for the 350-560 nm range. Such a fusion is further proposed to process concurrent active (ocean LiDAR) and passive (ocean-color) measurements, which can lead to nearly "exact" analytical inversion of an R rs spectrum. With such a fusion, it is found that the uncertainty in the inverted total a in the 350-560 nm range could be reduced to ∼2% for the synthesized data, which can thus significantly improve the derivation of a coefficients of other varying components. Although the inclusion of Z SD places an extra constraint in the inversion of R rs , no apparent improvement over the quasi-analytical algorithm (QAA) was found when the fusion of Z SD and R rs was applied to a field dataset, which calls for more accurate determination of the absorption coefficients from water samples.

Combined in-depth, 3D, en face imaging of the optic disc, optic disc pits and optic disc pit maculopathy using swept-source megahertz OCT at 1050 nm.

PubMed

Maertz, Josef; Kolb, Jan Philip; Klein, Thomas; Mohler, Kathrin J; Eibl, Matthias; Wieser, Wolfgang; Huber, Robert; Priglinger, Siegfried; Wolf, Armin

2018-02-01

To demonstrate papillary imaging of eyes with optic disc pits (ODP) or optic disc pit associated maculopathy (ODP-M) with ultrahigh-speed swept-source optical coherence tomography (SS-OCT) at 1.68 million A-scans/s. To generate 3D-renderings of the papillary area with 3D volume-reconstructions of the ODP and highly resolved en face images from a single densely-sampled megahertz-OCT (MHz-OCT) dataset for investigation of ODP-characteristics. A 1.68 MHz-prototype SS-MHz-OCT system at 1050 nm based on a Fourier-domain mode-locked laser was employed to acquire high-definition, 3D datasets with a dense sampling of 1600 × 1600 A-scans over a 45° field of view. Six eyes with ODPs, and two further eyes with glaucomatous alteration or without ocular pathology are presented. 3D-rendering of the deep papillary structures, virtual 3D-reconstructions of the ODPs and depth resolved isotropic en face images were generated using semiautomatic segmentation. 3D-rendering and en face imaging of the optic disc, ODPs and ODP associated pathologies showed a broad spectrum regarding ODP characteristics. Between individuals the shape of the ODP and the appending pathologies varied considerably. MHz-OCT en face imaging generates distinct top-view images of ODPs and ODP-M. MHz-OCT generates high resolution images of retinal pathologies associated with ODP-M and allows visualizing ODPs with depths of up to 2.7 mm. Different patterns of ODPs can be visualized in patients for the first time using 3D-reconstructions and co-registered high-definition en face images extracted from a single densely sampled 1050 nm megahertz-OCT (MHz-OCT) dataset. As the immediate vicinity to the SAS and the site of intrapapillary proliferation is located at the bottom of the ODP it is crucial to image the complete structure and the whole depth of ODPs. Especially in very deep pits, where non-swept-source OCT fails to reach the bottom, conventional swept-source devices and the MHz-OCT alike are feasible and beneficial methods to examine deep details of optic disc pathologies, while the MHz-OCT bears the advantage of an essentially swifter imaging process.

Initial evaluation of acoustic reflectors for the preservation of sensitive abdominal skin areas during MRgFUS treatment.

PubMed

Gorny, Krzysztof R; Chen, Shigao; Hangiandreou, Nicholas J; Hesley, Gina K; Woodrum, David A; Brown, Douglas L; Felmlee, Joel P

2009-04-21

During MR-guided focused ultrasound (MRgFUS) treatments of uterine fibroids using ExAblate(R)2000 (InSightec, Haifa, Israel), individual tissue ablations are performed extracorporeally through the patient's abdomen using an annular array FUS transducer embedded within the MR table. Ultrasound intensities in the near field are below therapeutic levels and, under normal conditions, heating of the patient skin is minimal. However, increased absorption of ultrasound energy within sensitive skin areas or areas with differing acoustic properties, such as scars, may lead to skin burns and therefore these areas must be kept outside the near field of the FUS beam. Depending on their location and size the sensitive areas may either obstruct parts of the fibroid from being treated or prevent the entire MRgFUS treatment altogether. The purpose of this work is to evaluate acoustic reflector materials that can be applied to protect skin and the underlying sensitive areas. Reflection coefficients of cork (0.88) and foam (0.91) based materials were evaluated with a hydrophone. An ExAblate 2000 MRgFUS system was used to simulate clinical treatment with discs of reflector materials placed in a near field underneath a gel phantom. MR thermometry was used to monitor temperature elevations as well as the integrity of the focal spot. The phantom measurements showed acoustic shadow zones behind the reflectors with zone depths changing between 7 and 27 mm, for reflector disc diameters increasing from 10 to 30 mm (40 mm diameter discs completely blocked the FUS beam at the depth evaluated). The effects on thermal lesions due to the presence of the reflectors in the FUS beam were found to diminish with decreasing disc diameter and increasing sonication depth. For a 20 mm diameter disc and beyond 50 mm sonication depth, thermal lesions were minimally affected by the presence of the disc. No heating was observed on the skin side of the foam reflectors, as confirmed by measurements performed with adhesive temperature labels. We present these data and discuss possible applications to clinical MRgFUS treatments.

Secchi, Angelo (1818-78)

NASA Astrophysics Data System (ADS)

Murdin, P.

2000-11-01

Born in Reggio Emilia, became a Jesuit and was exiled with the rest of the order by Mazzini's Roman Republic. After a period at Georgetown Observatory, he returned to Italy in 1849 as director of the Roman College Observatory, constructing a new observatory dome on top of the main pillars of the incomplete church of Saint Ignazio. Secchi used its telescopes for solar and stellar research, one of ...

Effects of annulus defects and implantation of poly(lactic-co-glycolic acid) (PLGA)/fibrin gel scaffolds on nerves ingrowth in a rabbit model of annular injury disc degeneration.

PubMed

Xin, Long; Xu, Weixing; Yu, Leijun; Fan, Shunwu; Wang, Wei; Yu, Fang; Wang, Zhenbin

2017-05-12

Growth of nerve fibers has been shown to occur in a rabbit model of intravertebral disc degeneration (IVD) induced by needle puncture. As nerve growth may underlie the process of chronic pain in humans affected by disc degeneration, we sought to investigate the factors underlying nerve ingrowth in a minimally invasive annulotomy rabbit model of IVD by comparing the effects of empty disc defects with those of defects filled with poly(lactic-co-glycolic acid)/fibrin gel (PLGA) plugs. New Zealand white rabbits (n = 24) received annular injuries at three lumbar levels (L3/4, L4/5, and L5/6). The discs were randomly assigned to four groups: (a) annular defect (1.8-mm diameter; 4-mm depth) by mini-trephine, (b) annular defect implanted with a PLGA scaffold containing a fibrin gel, (c) annular puncture by a 16G needle (5-mm depth), and (d) uninjured L2/3 disc (control). Disc degeneration was evaluated by radiography, MRI, histology, real-time PCR, and analysis of proteoglycan (PG) content. Nerve ingrowth into the discs was assessed by immunostaining with the nerve marker protein gene product 9.5. Injured discs showed a progressive disc space narrowing with significant disc degeneration and proteoglycan loss, as confirmed by imaging results, molecular and compositional analysis, and histological examinations. In 16G punctured discs, nerve ingrowth was observed on the surface of scar tissue. In annular defects, nerve fibers were found to be distributed along small fissures within the fibrocartilaginous-like tissue that filled the AF. In discs filled with PLGA/ fibrin gel, more nerve fibers were observed growing deeper into the inner AF along the open annular track.  In addition, innervations scores showed significantly higher than those of punctured discs and empty defects. A limited vascular proliferation was found in the injured sites and regenerated tissues. Nerve ingrowth was significantly higher in PLGA/fibrin-filled discs than in empty defects. Possible explanations include (i) annular fissures along the defect and early loss of proteoglycan may facilitate the ingrowth process and (ii) biodegradable PLGA/fibrin gel may promote adverse growth of nerves and blood vessels into deeper parts of injured disc. The rabbit annular defect model of disc degeneration appears suitable to investigate the effects of nerve ingrowth in relation to pain generation.

Temporomandibular joint arthrocentesis for internal derangement with disc displacement without reduction.

PubMed

Bhargava, Darpan; Jain, Megha; Deshpande, Ashwini; Singh, Ajita; Jaiswal, Jagdish

2015-06-01

Temporomandibular joint (TMJ) disc derangement is defined as a malpositioning of the articular disc relative to the condyle and eminence. Arthrocentesis of the TMJ is a minimally invasive chair side procedure for the patients with TMJ internal derangement. This case report presents convincing results to keep arthrocentesis as an imperative procedure to relieve such patients of their acute symptoms. TMJ dynamics has also been discussed for an in-depth understanding of the pathology in cases with internal derangement.

Biological invasion by a benthivorous fish reduced the cover and species richness of aquatic plants in most lakes of a large North American ecoregion.

PubMed

Bajer, Przemyslaw G; Beck, Marcus W; Cross, Timothy K; Koch, Justine D; Bartodziej, William M; Sorensen, Peter W

2016-12-01

Biological invasions are projected to be the main driver of biodiversity and ecosystem function loss in lakes in the 21st century. However, the extent of these future losses is difficult to quantify because most invasions are recent and confounded by other stressors. In this study, we quantified the outcome of a century-old invasion, the introduction of common carp to North America, to illustrate potential consequences of introducing non-native ecosystem engineers to lakes worldwide. We used the decline in aquatic plant richness and cover as an index of ecological impact across three ecoregions: Great Plains, Eastern Temperate Forests and Northern Forests. Using whole-lake manipulations, we demonstrated that both submersed plant cover and richness declined exponentially as carp biomass increased such that plant cover was reduced to <10% and species richness was halved in lakes in which carp biomass exceeded 190 kg ha -1 . Using catch rates amassed from 2000+ lakes, we showed that carp exceeded this biomass level in 70.6% of Great Plains lakes and 23.3% of Eastern Temperate Forests lakes, but 0% of Northern Forests lakes. Using model selection analysis, we showed that carp was a key driver of plant species richness along with Secchi depth, lake area and human development of lake watersheds. Model parameters showed that carp reduced species richness to a similar degree across lakes of various Secchi depths and surface areas. In regions dominated by carp (e.g., Great Plains), carp had a stronger impact on plant richness than human watershed development. Overall, our analysis shows that the introduction of common carp played a key role in driving a severe reduction in plant cover and richness in a majority of Great Plains lakes and a large portion of Eastern Temperate Forests lakes in North America. © 2016 John Wiley & Sons Ltd.

Methane and carbon dioxide emissions from 40 lakes along a north–south latitudinal transect in Alaska

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sepulveda-Jauregui, A.; Walter Anthony, K. M.; Martinez-Cruz, K.

Uncertainties in the magnitude and seasonality of various gas emission modes, particularly among different lake types, limit our ability to estimate methane (CH 4) and carbon dioxide (CO 2) emissions from northern lakes. Here we assessed the relationship between CH 4 and CO 2 emission modes in 40 lakes along a latitudinal transect in Alaska to physicochemical limnology and geographic characteristics, including permafrost soil type surrounding lakes. Emission modes included Direct Ebullition, Diffusion, Storage flux, and a newly identified Ice-Bubble Storage (IBS) flux. We found that all lakes were net sources of atmospheric CH 4 and CO 2, but themore » climate warming impact of lake CH 4 emissions was two times higher than that of CO 2. Ebullition and Diffusion were the dominant modes of CH 4 and CO 2 emissions respectively. IBS, ~ 10% of total annual CH 4 emissions, is the release to the atmosphere of seasonally ice-trapped bubbles when lake ice confining bubbles begins to melt in spring. IBS, which has not been explicitly accounted for in regional studies, increased the estimate of springtime emissions from our study lakes by 320%. Geographically, CH 4 emissions from stratified, dystrophic interior Alaska thermokarst (thaw) lakes formed in icy, organic-rich yedoma permafrost soils were 6-fold higher than from non-yedoma lakes throughout the rest of Alaska. Total CH 4 emission was correlated with concentrations of phosphate and total nitrogen in lake water, Secchi depth and lake area, with yedoma lakes having higher nutrient concentrations, shallower Secchi depth, and smaller lake areas. Our findings suggest that permafrost type plays important roles in determining CH 4 emissions from lakes by both supplying organic matter to methanogenesis directly from thawing permafrost and by enhancing nutrient availability to primary production, which can also fuel decomposition and methanogenesis.« less

Methane and carbon dioxide emissions from 40 lakes along a north–south latitudinal transect in Alaska

DOE PAGES

Sepulveda-Jauregui, A.; Walter Anthony, K. M.; Martinez-Cruz, K.; ...

2014-09-12

Uncertainties in the magnitude and seasonality of various gas emission modes, particularly among different lake types, limit our ability to estimate methane (CH 4) and carbon dioxide (CO 2) emissions from northern lakes. Here we assessed the relationship between CH 4 and CO 2 emission modes in 40 lakes along a latitudinal transect in Alaska to physicochemical limnology and geographic characteristics, including permafrost soil type surrounding lakes. Emission modes included Direct Ebullition, Diffusion, Storage flux, and a newly identified Ice-Bubble Storage (IBS) flux. We found that all lakes were net sources of atmospheric CH 4 and CO 2, but themore » climate warming impact of lake CH 4 emissions was two times higher than that of CO 2. Ebullition and Diffusion were the dominant modes of CH 4 and CO 2 emissions respectively. IBS, ~ 10% of total annual CH 4 emissions, is the release to the atmosphere of seasonally ice-trapped bubbles when lake ice confining bubbles begins to melt in spring. IBS, which has not been explicitly accounted for in regional studies, increased the estimate of springtime emissions from our study lakes by 320%. Geographically, CH 4 emissions from stratified, dystrophic interior Alaska thermokarst (thaw) lakes formed in icy, organic-rich yedoma permafrost soils were 6-fold higher than from non-yedoma lakes throughout the rest of Alaska. Total CH 4 emission was correlated with concentrations of phosphate and total nitrogen in lake water, Secchi depth and lake area, with yedoma lakes having higher nutrient concentrations, shallower Secchi depth, and smaller lake areas. Our findings suggest that permafrost type plays important roles in determining CH 4 emissions from lakes by both supplying organic matter to methanogenesis directly from thawing permafrost and by enhancing nutrient availability to primary production, which can also fuel decomposition and methanogenesis.« less

Influence of dreissenid mussels on catchability of benthic fishes in bottom trawls

USGS Publications Warehouse

Kocovsky, Patrick M.; Stapanian, Martin A.

2011-01-01

Inferring trends in true abundance of fish populations from catch per unit effort data requires either the knowledge of capture probability or the assumption that it is constant, both of which are unlikely contingencies. We developed and validated an index of catchability (a proxy measure for capture probability) from a long-term data set describing nearshore waters of western Lake Erie, and we used the index to test the hypothesis that catchability of four abundant benthic species captured in bottom trawls changed after the invasion of dreissenid mussels. We estimated daytime and nighttime catchability for 1972–1990 (predreissenid period) and 1991–2009 (dreissenid period); we then tested for differences between nighttime and daytime catchability in the predreissenid and dreissenid periods and the nighttime–daytime differential in catchability during the dreissenid period. We also tested relationships between Secchi depth and the catchability index via linear regression. Catchability indices for white perch Morone americana, yellow perch Perca flavescens, and trout-perch Percopsis omiscomaycus did not differ between daytime and nighttime during the predreissenid period. After establishment of dreissenids, all three of these species had lower daytime catchability than nighttime catchability and had positive nighttime–daytime differentials, indicating a shift toward higher nighttime catchability relative to daytime catchability. Changes in catchability indices for freshwater drum Aplodinotus grunniens were opposite the changes observed for the other three species, possibly because the freshwater drum is the only species that actively feeds on dreissenids. Catchability indices were negatively related to water clarity (Secchi depth) for three of the species. Our results are consistent with the hypothesis that catchability of the four most common benthic fish species captured in bottom trawls within nearshore waters of western Lake Erie changed after the dreissenid invasion because of increased water clarity and increased visibility, which led to greater daytime trawl avoidance.

Application of Airborne Hydrographic Laser Scanning for Mapping Shallow Water Riverine Environments in the Pacific Northwest, United States

NASA Astrophysics Data System (ADS)

Cooper, C.; Nayegandhi, A.; Faux, R.

2013-12-01

Small-footprint, green wavelength airborne LiDAR systems can provide seamless topography across the land-water interface at very high spatial resolution. These data have the potential to improve floodplain modeling, fisheries habitat assessments, stream restoration efforts, and other applications by continuously mapping shallow water depths that are difficult or impossible to measure using traditional ground-based or water-borne survey techniques. WSI (Corvallis, Oregon) in collaboration with Dewberry, (Tampa, Florida) and Riegl (Orlando, Florida), deployed the Riegl VQ-820-G hydrographic airborne laser scanner to map riverine and lacustrine environments from Oregon to Minnesota. Discussion will focus on the ability to accurately map depth and underwater structure, as well as riparian vegetation and terrain under different conditions. Results indicate that depth penetration varies with both water (i.e. clarity and surface conditions) and bottom conditions (i.e. substrate, depth, and landform). Depth penetration was typically limited to 1 Secchi depth or less across selected project areas. As an example, the green LiDAR system effectively mapped 83% of a shallow water river system, the Sandy River, with typical depths ranging from 0-2.5 meters. WSI will show quantitative comparisons of Green LiDAR surveys against more traditional methods such as rod or sonar surveys. WSI will also discuss advantages and limitations of Green LiDAR surveys for bathymetric modeling including survey accuracy, density, and efficiency along with data processing challenges not inherent with traditional NIR LiDAR processing.

Using CHEMTAX to evaluate seasonal and interannual dynamics of the phytoplankton community off the South-west coast of Portugal

NASA Astrophysics Data System (ADS)

Goela, P. C.; Danchenko, S.; Icely, J. D.; Lubian, L. M.; Cristina, S.; Newton, A.

2014-12-01

CHEMTAX was used to assess the relative contribution of the main phytoplankton classes to the total concentration of Chlorophyll a (Chl a) from the waters off SW coast of Portugal. Sampling campaigns were carried out during all seasons from 2008 to 2012, at three stations located 2, 10 and 18 km from the coast. Samples were taken from the surface, mid-Secchi and Secchi depth, for the determination of Chl a and other phytoplanktonic pigments by HPLC. Supporting data were also obtained including dissolved inorganic nutrients, salinity, transparency, temperature and upwelling indices. The CHEMTAX results were also related to microscopy counts and also spectral analysis of absorption of other samples from the same sampling campaigns. The pigment results showed that diatoms dominated from early spring to summer, coinciding with upwelling conditions, while cryptophytes, prymnesiophytes and prasinophytes dominated in autumn and winter, coinciding with seasonal stratification. Although the contribution of cyanobacteria to total Chl a was generally low, there were occasional sampling campaigns where it was exceptionally high, but these appeared not to be related to upwelling. Dinoflagellates and chrysophytes were minority groups although the pigment marker peridinin that was used to distinguish dinoflagellates was not adequate for distinguishing all the members of this group. CHEMTAX was particularly useful for discriminating between the smaller (0-20 μm) classes of the microplankton that could not be easily identified by microscopy.

Global Lakes Sentinel Services: Water Quality Parameters Retrieval in Lakes Using the MERIS and S3-OLCI Band Sets

NASA Astrophysics Data System (ADS)

Peters, Steef; Alikas, Krista; Hommersom, Annelies; Latt, Silver; Reinart, Anu; Giardino, Claudia; Bresciani, Mariano; Philipson, Petra; Ruescas, Ana; Stelzer, Kerstin; Schenk, Karin; Heege, Thomas; Gege, Peter; Koponen, Sampsa; Kallio, Karri; Zhang, Yunlin

2015-12-01

The European collaborative project GLaSS aims to prepare for the use of the data streams from Sentinel 2 and Sentinel 3. Its focus is on inland waters, since these are considered to be sentinels for land-use- and climate change and need to be monitored closely. One of the objectives of the project is to compare existing water quality algorithms and parameterizations on the basis of in-situ spectral observations and Hydrolight simulations. A first achievement of the project is the collection of over 400 Rrs spectra with accompanying data on CHL, TSM, aCDOM and Secchi depth. Especially the dataset on Lake CDOM measurements represents a rather unique reference dataset.

Processing multispectral data obtained by orbital platforms of the LANDSAT series for studies of water quality in Guanabara Bay. M.S. Thesis

NASA Technical Reports Server (NTRS)

Dejesusparada, N. (Principal Investigator); Verdesio, J. J.

1981-01-01

The relationship existing between Guanabara Bay water quality ground truth parameters and LANDSAT MSS video data was investigated. The parameters considered were: chorophyll content, water transparency usng the Secchi disk, salinity, and dissolved ammonia. Data from two overflights was used, and methods of processing digital data were compared. Linear and nonlinear regression analyses were utilized, comparing original data with processed data by using the correlation coefficient and the estimation mean error. It was determined that better quality data are obtained by using radiometric correction programs with a physical basis, contrast ratio, and normalization. Incidental locations of floating vegetation, changes in bottom depth, oil slicks, and ships at anchor were made.

The Location of the Deepest Point of the Eyeball Determines the Optic Disc Configuration.

PubMed

Kim, Yong Chan; Jung, Younhea; Park, Hae-Young Lopilly; Park, Chan Kee

2017-07-19

Tilted and rotated appearances are hallmarks of the myopic optic disc. As the eyeball grows axially, the posterior pole elongates not only globally but in a localized manner as well. In this process, the optic disc is pulled towards the deepest point of the elongated eyeball, which might result in a change in optic disc configuration. Thus, we hypothesized that analyzing the variation of posterior pole contour can play a major role in understanding optic disc configuration in myopic subjects. By analyzing consecutive images of swept source OCT coronal sections at the posterior pole, the deepest interface between Bruch's membrane and the choroid could be identified as the deepest point of the eyeball (DPE). The location and the properties of the DPE differed significantly between the 125 eyes of non-glaucomatous myopic group and the 40 eyes of non-glaucomatous emmetropic group classified based on 24 mm axial length. The results suggested that the larger disc to DPE angle and the larger disc to DPE depth strongly predicts the optic disc torsion degree and the optic disc tilt. Our findings suggest that identifying the posterior pole profile plays a major role in understanding the optic disc alterations found in myopic subjects.

Formation of lamellar cross bridges in the annulus fibrosus of the intervertebral disc is a consequence of vascular regression.

PubMed

Smith, Lachlan J; Elliott, Dawn M

2011-05-01

Cross bridges are radial structures within the highly organized lamellar structure of the annulus fibrosus of the intervertebral disc that connect two or more non-consecutive lamellae. Their origin and function are unknown. During fetal development, blood vessels penetrate deep within the AF and recede during postnatal growth. We hypothesized that cross bridges are the pathways left by these receding blood vessels. Initially, the presence of cross bridges was confirmed in cadaveric human discs aged 25 and 53 years. Next, L1-L2 intervertebral discs (n=4) from sheep ranging in age from 75 days fetal gestation to adult were processed for paraffin histology. Mid-sagittal sections were immunostained for endothelial cell marker PECAM-1. The anterior and posterior AF were imaged using differential interference contrast microscopy, and the following parameters were quantified: total number of distinct lamellae, total number of cross bridges, percentage of cross bridges staining positive for PECAM-1, cross bridge penetration depth (% total lamellae), and PECAM-1 positive cross bridge penetration depth. Cross bridges were first observed at 100 days fetal gestation. The overall number peaked in neonates then remained relatively unchanged. The percentage of PECAM-1 positive cross bridges declined progressively from almost 100% at 100 days gestation to less than 10% in adults. Cross bridge penetration depth peaked in neonates then remained unchanged at subsequent ages. Depth of PECAM-1 positive cross bridges decreased progressively after birth. Findings were similar for both the anterior and posterior. The AF lamellar architecture is established early in development. It later becomes disrupted as a consequence of vascularization. Blood vessels then recede, perhaps due to increasing mechanical stresses in the surrounding matrix. In this study we present evidence that the pathways left by receding blood vessels remain as lamellar cross bridges. It is unclear whether the presence of cross bridges in the aging and degenerating intervertebral disc would be advantageous or detrimental, and this question should be addressed by future studies. Copyright © 2011 International Society of Matrix Biology. Published by Elsevier B.V. All rights reserved.

Gap formation by inclined massive planets in locally isothermal three-dimensional discs

NASA Astrophysics Data System (ADS)

Chametla, Raúl O.; Sánchez-Salcedo, F. J.; Masset, F. S.; Hidalgo-Gámez, A. M.

2017-07-01

We study gap formation in gaseous protoplanetary discs by a Jupiter mass planet. The planet's orbit is circular and inclined relative to the mid-plane of the disc. We use the impulse approximation to estimate the gravitational tidal torque between the planet and the disc, and infer the gap profile. For low-mass discs, we provide a criterion for gap opening when the orbital inclination is ≤30°. Using the fargo3d code, we simulate the disc response to an inclined massive planet. The dependence of the depth and width of the gap obtained in the simulations on the inclination of the planet is broadly consistent with the scaling laws derived in the impulse approximation. Although we mainly focus on planets kept on fixed orbits, the formalism permits to infer the temporal evolution of the gap profile in the cases where the inclination of the planet changes with time. This study may be useful to understand the migration of massive planets on inclined orbit, because the strength of the interaction with the disc depends on whether a gap is opened or not.

Planet signatures and Size Segregation in Debris Discs

NASA Astrophysics Data System (ADS)

Thébault, Philippe

2014-01-01

The response of a debris disc to a planetary perturber is the result of the complex interplay between gravitational effects, grain collisions and stellar radiation pressure (Stark & Kuchner (2009). We investigate to what extent this response can depart from the pure gravitational case when including grain collisional production and radiation pressure. We use the DyCoSS code (Thébault (2012), designed to study the coupled effect of collisions and dynamics for systems at steady state with one perturbing body. We focus on two outcomes: the 2D surface density profile of the disc+planet system, and the way the Particle Size Distribution (PSD) is spatially segregated within the disc. We consider two set-ups: 1) a narrow ring with an exterior ``shepherding'' planet, and 2) an extended disc in which a planet is embedded. For each case, the planet mass and orbit are explored as free parameters, and an unperturbed ``no-planet'' case is also considered. Another parameter is the disc's collisional activity, as parameterized by its optical depth τ.

NOHRSC Interactive Snow Information

Science.gov Websites

-present) RFC Basin Other (non-RFC) Basin State NSA region (Discussion) NSA subregion (Disc.) Basins by None Snow Water Equivalent Snow Depth Shallow SWE Shallow Snow Depth Snow Temperature Snow Density Snow Melt Snow Precipitation Non-Snow Precipitation Air Temperature Solar Radiation Relative Humidity

[Self-assembly tissue engineering fibrocartilage model of goat temporomandibular joint disc].

PubMed

Kang, Hong; Li, Zhen-Qiang; Bi, Yan-Da

2011-06-01

To construct self-assembly fibrocartilage model of goat temporomandibular joint disc and observe the biological characteristics of the self-assembled fibrocartilage constructs, further to provide a basis for tissue engineering of the temporomandibular joint disc and other fibrocartilage. Cells from temporomandibular joint discs of goats were harvested and cultured. 5.5 x 10(6) cells were seeded in each agarose well with diameter 5 mm x depth 10 mm, daily replace of medium, cultured for 2 weeks. One day after seeding, goat temporomandibular joint disc cells in agarose wells were gathered and began to self-assemble into a disc-shaped base, then gradually turned into a round shape. When cultured for 2 weeks, hematoxylin-eosin staining was conducted and observed that cells were round and wrapped around by the matrix. Positive Safranin-O/fast green staining for glycosaminoglycans was observed throughout the entire constructs, and picro-sirius red staining was examined and distribution of numerous type I collagen was found. Immunohistochemistry staining demonstrated brown yellow particles in cytoplasm and around extracellular matrix, which showed self-assembly construct can produce type I collagen as native temporomandibular joint disc tissue. Production of extracellular matrix in self-assembly construct as native temporomandibular joint disc tissue indicates that the use of agarose wells to construct engineered temporomandibular joint disc will be possible and practicable.

Efficient radiative transfer techniques in hydrodynamic simulations

NASA Astrophysics Data System (ADS)

Mercer, A.; Stamatellos, D.; Dunhill, A.

2018-05-01

Radiative transfer is an important component of hydrodynamic simulations as it determines the thermal properties of a physical system. It is especially important in cases where heating and cooling regulate significant processes, such as in the collapse of molecular clouds, the development of gravitational instabilities in protostellar discs, disc-planet interactions, and planet migration. We compare two approximate radiative transfer methods which indirectly estimate optical depths within hydrodynamic simulations using two different metrics: (i) the gravitational potential and density of the gas (Stamatellos et al.), and (ii) the pressure scale-height (Lombardi et al.). We find that both methods are accurate for spherical configurations e.g. in collapsing molecular clouds and within clumps that form in protostellar discs. However, the pressure scale-height approach is more accurate in protostellar discs (low and high-mass discs, discs with spiral features, discs with embedded planets). We also investigate the β-cooling approximation which is commonly used when simulating protostellar discs, and in which the cooling time is proportional to the orbital period of the gas. We demonstrate that the use of a constant β cannot capture the wide range of spatial and temporal variations of cooling in protostellar discs, which may affect the development of gravitational instabilities, planet migration, planet mass growth, and the orbital properties of planets.

Use of thematic mapper imagery to assess water quality, trophic state, and macrophyte distributions in Massachusetts lakes

USGS Publications Warehouse

Waldron, Marcus C.; Steeves, Peter A.; Finn, John T.

2001-01-01

During the spring and summer of 1996, 1997, and 1998, measurements of phytoplankton- chlorophyll concentration, Secchi disk transparency, and color were made at 97 Massachusetts lakes within 24 hours of Landsat Thematic Mapper imaging of the lakes in an effort to assess water quality and trophic state. Spatial distributions of floating, emergent, and submerged macrophytes were mapped in 49 of the lakes at least once during the 3-year period. The maps were digitized and used to assign pixels in the thematic mapper images to one of four vegetation cover classes-open water, 1-50 percent floating-and-emergent-vegetation cover, 51-100 percent floating-and-emergent-vegetation cover, and submerged vegetation at any density. The field data were collected by teams of U.S. Geological Survey and Massachusetts Department of Environmental Management staff and by 76 volunteers. Side-by-side sampling by U.S. Geological Survey and volunteer field teams resulted in statistically similar chlorophyll determinations, Secchi disk readings, and temperature measurements, but concurrent color determinations were not similar, possibly due to contamination of sample bottles issued to the volunteers.Attempts to develop predictive relations between phytoplankton-chlorophyll concentration, Secchi disk transparency, lake color, dissolved organic carbon, and various combinations of thematic mapper bands 1, 2, 3, and 4 digital numbers were unsuccessful, primarily because of the extremely low concentrations of chlorophyll in the lakes studied, and also because of the highly variable dissolved organic carbon concentrations.Predictive relations were developed between Secchi disk transparency and phytoplankton-chlorophyll concentration, and between color and dissolved organic carbon concentration. Phytoplankton-chlorophyll concentration was inversely correlated with Secchi disk transparency during all three sampling periods. The relations were very similar in 1996 and 1997 and indicated that 62 to 67 percent of the variability in Secchi disk transparency could be explained by the chlorophyll concentration. Analysis of color and dissolved organic carbon concentrations in water samples collected by U.S. Geological Survey field teams in 1996-98 indicated that 91 percent of the variance in color in Massachusetts lakes can be explained by variations in dissolved organic carbon.Areas of open-water, submerged vegetation, and two surface-vegetation-cover classes predicted from Thematic Mapper images acquired in the summer of 1996 closely matched the areas observed in a set of field observations. However, the same analysis applied to a set of data acquired in the summer of 1997 resulted in somewhat less reliable predictions, and an attempt to predict 1996 vegetation-cover areas using the relations developed in the 1997 analysis was unsuccessful.

Preliminary optical coherence tomography investigation of the temporo-mandibular joint disc

NASA Astrophysics Data System (ADS)

Mărcăuteanu, Corina; Demjan, Enikö; Sinescu, Cosmin; Negrutiu, Meda; Motoc, Adrian; Lighezan, Rodica; Vasile, Liliana; Hughes, Mike; Bradu, Adrian; Dobre, George; Podoleanu, Adrian G.

2010-02-01

Aim and objectives. The morphology and position of the temporo-mandibular disc are key issues in the diagnosis and treatment of arthrogenous temporo-mandibular disorders. Magnetic resonance imaging and arthroscopy are used today to identify: flattening of the pars posterior of the disc, perforation and/or adhesions in the pars intermedia of the disc and disc displacements. The present study proposes the investigation of the temporo-mandibular joint disc by optical coherence tomography (OCT). Material and methods. 8 human temporo-mandibular joint discs were harvested from dead subjects, under 40 year of age, and conserved in formalin. They had a normal morphology, with a thicker pars posterior (2,6 mm on the average) and a thinner pars intermedia (1mm on the average). We investigated the disc samples using two different OCT systems: an en-face OCT (time domain (TD)-OCT) system, working at 1300 nm (C-scan and B-scan mode) and a spectral OCT system (a Fourier domain (FD)-OCT) system , working at 840 nm (B-scan mode). Results. The OCT investigation of the temporo-mandibular joint discs revealed a homogeneous microstructure. The longer wavelength of the TD-OCT offers a higher penetration depth (2,5 mm in air), which is important for the analysis of the pars posterior, while the FD-OCT is much faster. Conclusions: OCT is a promising imaging method for the microstructural characterization of the temporo-mandibular disc.

Studies of the inner shelf and coastal sedimentation environment of the Beaufort Sea from ERTS-1

NASA Technical Reports Server (NTRS)

Reimnitz, E. (Principal Investigator); Barnes, P. W.

1973-01-01

The author has identified the following significant results. The particulate transport processes involved in the movement of surficial waters were examined using secchi disc readings, light attenuation coefficients, and particulate weights from filtration. Observations gathered during the summers of 1971 and 1972 indicate a remarkable difference in particulate matter and turbidity between the two years. ERTS-1 imagery during August 1972 showed turbid water along the northern Alaska coast. The uniformity of distribution of the turbid water and the fact that the river discharge is low at this period suggest that the turbidity is related to causes other than river effluent. Studies indicate that wave action is a more significant factor influencing particulate transport than believed heretofore. The boundary between the essentially immobile shorefast ice and the moving pack ice has been plotted from several ERTS-1 images and found to occur fairly consistently along the 20 meter contour. Considering the vast difference in the amount of ice movement shoreward and seaward of this boundary, ice-bottom action should also be different on either side of this boundary and for that matter at the shear zone that develops along the boundary.

The blooms of a cyanobacterium, Microcystis cf. aeruginosa in a severely polluted estuary, the Golden Horn, Turkey

NASA Astrophysics Data System (ADS)

Taş, Seyfettin; Okuş, Erdoğan; Aslan-Yılmaz, Aslı

2006-07-01

The distribution of toxic cyanobacterium Microcystis cf. aeruginosa in the severely polluted Golden Horn Estuary was studied from 1998 to 2000. Microcystis persisted at the upper estuary where the water circulation was poor and values ranged between 2.9 × 10 4 and 2.7 × 10 6 cells ml -1 throughout the study. Simultaneously measured physical (salinity, temperature, rainfall and secchi disc) and chemical parameters (nutrients and dissolved oxygen) were evaluated together with Microcystis data. Although the Microcystis blooms generally occur in summer due to the increase in temperature, the blooms were recorded in winter in the present study. The abundance of Microcystis depended on the variations in salinity and both blooms were recorded below S = 2. A moderate partial correlation between Microcystis abundance and salinity was detected in the presence of temperature, dissolved oxygen and precipitation data ( r = -0.561, p = 0.002). The M. cf. aeruginosa abundance was low in the summer when the salinity was higher than winter. A remarkable increase in the eukaryotic phytoplankton abundance following the improvements in the water quality of the estuary occurred, whilst the Microcystis abundance remained below bloom level.

Application of LANDSAT to the surveillance and control of lake eutrophication in the Great Lakes Basin

NASA Technical Reports Server (NTRS)

Rogers, R. H. (Principal Investigator)

1975-01-01

The author has identified the following significant results. Preliminary results in Saginaw Bay show that processed LANDSAT data provides a synoptic view of turbidity and circulation patterns that no degree of ground monitoring can provide. Processed imagery was produced to show nine discrete categories of turbidity, as indicated by nine Secchi depths between 0.3 and 3.3 meters. Analysis of lakes near Madison, Wisconsin show that inland lake water can be categorized by LANDSAT as clear, tannin, algal, and red clay. LANDSAT's capability to inventory watershed land use was throughly demonstrated in the Ohio-Kentucky-Indiana regional planning area. Computer tabulations providing area covered by each of 16 land use categories were rapidly and economically produced for each of the 225 watersheds and nine counties.

Effects of smallmouth buffalo, Ictiobus bubalus biomass on water transparency, nutrients, and productivity in shallow experimental ponds

USGS Publications Warehouse

Goetz, Daniel B.; Kroger, Robert; Miranda, Leandro E.

2014-01-01

The smallmouth buffalo Ictiobus bubalus is a native benthivore to floodplain lakes in the Yazoo River Basin, USA. Based on evidence from other benthivorous fish studies we hypothesized high biomasses of I. bubalus contribute to poor water quality conditions. We tested this hypothesis in shallow (< 1.5 m) 0.05 ha earthen ponds at three stocking biomasses over a 10-week period during the summer of 2012. The most notable results from the permutational multivariate analysis of variance suggest I. bubalus at high and moderate biomasses significantly (p < 0.05) enhanced turbidity and suspended solid levels while decreasing Secchi depth. Our results suggest that effects of I. bubalus on water clarity may have considerable ecological implications in natural habitats such as shallow floodplain lakes.

Monitoring coastal water properties and current circulation with ERTS-1. [Delaware Bay

NASA Technical Reports Server (NTRS)

Klemas, V.; Otley, M.; Wethe, C.; Rogers, R.

1974-01-01

Imagery and digital tapes from nine successful ERTS-1 passes over Delaware Bay during different portions of the tidal cycle have been analyzed with special emphasis on turbidity, current circulation, waste disposal plumes and convergent boundaries between different water masses. ERTS-1 image radiance correlated well with Secchi depth and suspended sediment concentration. Circulation patterns observed by ERTS-1 during different parts of the tidal cycle, agreed well with predicted and measured currents throughout Delaware Bay. Convergent shear boundaries between different water masses were observed from ERTS-1. In several ERTS-1 frames, waste disposal plumes have been detected 36 miles off Delaware's Atlantic coast. The ERTS-1 results are being used to extend and verify hydrodynamic models of the bay, developed for predicting oil slick movement and estimating sediment transport.

Mississippi Sound remote sensing study. [NASA Earth Resources Laboratory seasonal experiments

NASA Technical Reports Server (NTRS)

Atwell, B. H.; Thomann, G. C.

1973-01-01

A study of the Mississippi Sound was initiated in early 1971 by personnel of NASA Earth Resources Laboratory. Four separate seasonal experiments consisting of quasi-synoptic remote and surface measurements over the entire area were planned. Approximately 80 stations distributed throughout Mississippi Sound were occupied. Surface water temperature and secchi extinction depth were measured at each station and water samples were collected for water quality analyses. The surface distribution of three water parameters of interest from a remote sensing standpoint - temperature, salinity and chlorophyll content - are displayed in map form. Areal variations in these parameters are related to tides and winds. A brief discussion of the general problem of radiative measurements of water temperature is followed by a comparison of remotely measured temperatures (PRT-5) to surface vessel measurements.

The blue-to-green reflectance ratio and lake water quality

NASA Technical Reports Server (NTRS)

Piech, K. R.; Schott, J. R.; Stewart, K. M.

1978-01-01

Correlations between the relative values of the blue and green reflectances of a lake and water quality indices, such as depth of photic zone, Secchi disk transparency, attenuation coefficient, and chlorophyll concentration, have been observed during an intensive satellite, aircraft, and surface vessel study of Lake Ontario and Conesus Lake. Determinations of blue and green reflectances from Skylab S190A color imagery are in excellent agreement with values obtained from small-scale color imagery from aircraft. Further, the accuracy of the satellite data appears within that required for extrapolation to the water quality indices. The study has also determined that changes in chlorophyll, lignin, and humic acid concentration can be discriminated by the behavior of the blue-to-green reflectance ratio and the reflectances of the green and red bands.

Bay of Fundy verification of a system for multidate Landsat measurement of suspended sediment

NASA Technical Reports Server (NTRS)

Munday, J. C., Jr.; Afoldi, T. T.; Amos, C. L.

1981-01-01

A system for automated multidate Landsat CCT MSS measurement of suspended sediment concentration (S) has been implemented and verified on nine sets (108 points) of data from the Bay of Fundy, Canada. The system employs 'chromaticity analysis' to provide automatic pixel-by-pixel adjustment of atmospheric variations, permitting reference calibration data from one or several dates to be spatially and temporally extrapolated to other regions and to other dates. For verification, each data set was used in turn as test data against the remainder as a calibration set: the average absolute error was 44 percent of S over the range 1-1000 mg/l. The system can be used to measure chlorophyll (in the absence of atmospheric variations), Secchi disk depth, and turbidity.

2015 status of the Lake Ontario lower trophic levels

USGS Publications Warehouse

Holeck, Kristen T.; Rudstam, Lars G.; Hotaling, Christopher; McCullough, Russ D.; Lemon, Dave; Pearsall, Web; Lantry, Jana; Connerton, Michael J.; LaPan, Steve; Biesinger, Zy; Lantry, Brian F.; Walsh, Maureen; Weidel, Brian C.

2016-01-01

Offshore spring total phosphorus (TP) in 2015 was 4.2 μ g/L, the same as in 2014; this is lower than 2001 - 2013, but there is no significant time trend 2001 - 2015. Offshore soluble reactive phosphorus (SRP) was very low in 2015; Apr/May - Oct mean values were <1 μ g/L at most sites. SRP has been stable in nearshore and offshore habitats since 1998 (range, 0.4 – 3.3 μ g/L). TP concentrations were low at both nearshore and offshore locations (range 4.2 - 8.1 μ g/L), and TP and SRP concentrations were significantly higher in the nearshore as compared to the offshore (6.8 μ g/L vs 4.8 μ g/L, TP; 1.1 μ g/L vs 0.7 μ g/L, SRP).Chlorophyll-a and Secchi depth values are indicative of oligotrophic conditions in nearshore and offshore habitats. Offshore summer chlorophyll- a declined significantly 2000 - 2015. Nearshore chlorophyll- a increased 1995 - 2004 but then declined 2005 - 2015. Epilimnetic chlorophyll-a averaged between 0.9 and 1.9 1 μg/L across sites, and offshore concentrations (1.4 1 μg/L) were significantly higher than nearshore (1.1 μg/L). Summer Secchi depth increased significantly in the offshore 2000 -2015 and showed no trend in the nearshore, 1995 - 2015. Apr/May - Oct Secchi depth ranged from 5.0 m to 13.0 m at individual sites and was higher in the offshore (9.5 m) than nearshore (6.2 m).In 2015, Apr/May - Oct epilimnetic zooplankton density, size, and biomass were not different between the offshore and the nearshore, but cyclopoid biomass was higher in the offshore (8.3 mg/m 3 vs 2.0 mg/m3) and Bythotrephes biomass was higher in the nearshore (0.17 mg/m3 vs 0.04 mg/m3).Zooplankton density and biomass peaked in September, an atypical pattern. This coincided with peaks in calanoid copepod, daphnid, and Holopedium Holopedium biomass in the nearshore has increased significantly since 1995.The predatory cladoceran Cercopagis continued to be abundant in summer in the nearshore (3.4 μ g/L) but not in the offshore (0.8 μ g/L). Bythotrephes biomass was very low (<0.3 μ g/L) in both nearshore and offshore habitats. Combined biomass of these predatory cladocerans in the offshore was the lowest recorded since 2001.Summer nearshore zooplankton density and biomass declined significantly 1995 - 2004 and then increased significantly 2005 – 2015. The decline was due to reductions in bosminids and cyclopoids and the increase was due mostly to a rebound in bosminids.Summer offshore zooplankton density and biomass increased significantly 2005 - 2015. The increase was due to an increase in bosminids and cyclopoids. In 2015, offshore summer epilimnetic zooplankton biomass was 52 mg/m3 (2005 - 2014 mean=18 mg/m3).Most zooplankton biomass was found in the metalimnion in July and in the hypolimnion in September. Cyclopoids and Limnocalanus dominated the metalimnion and Limnocalanus dominated the hypolimnion. Whole water column samples taken show a stable zooplankton biomass but changing community composition since 2010. Cyclopoids increased 2013 - 2015 and daphnids declined 2014 - 2015.

Evaluating lake phytoplanton response to human disturbance and climate change using satellite imagery

NASA Astrophysics Data System (ADS)

Novitski, Linda Nicole

Accurate and cost-effective assessment of water quality is necessary for proper management and restoration of inland water bodies susceptible to algal bloom conditions. Landsat and MODIS satellite images were used to create chlorophyll and Secchi depth predictive models for algal assessment of Great Lakes and other lakes of the United States. Boosted regression tree (BRT) models using satellite imagery are both easy to use and can have high predictive performance. BRT models inferred chlorophyll and Secchi depth more accurately than linear regression models for all study locations. Inferred chlorophyll of inner Saginaw Bay was subsequently used in ecological models to help understand the ecological drivers of algal blooms in this ecosystem. For small lakes (non-Great Lakes), the best national Landsat model for ln-transformed chlorophyll was the BRT model and had a cross-validation R 2 of 0.44 and a 0.76 ln-transformed mug/L RMSE. The best national Landsat model for Secchi depth was also a BRT model that had an adjusted R 2 of 0.52 and a 0.80 m RMSE. We assessed the applicability of the national chlorophyll model for ecological analysis by comparing the total phosphorus- chlorophyll relationship with chlorophyll determined from sampling or remote sensing, which showed the total phosphorus- chlorophyll relationship had an adjusted R2 = 0.58 and 1.02 ln-transformed microg/L RMSE with sampled chlorophyll versus an adjusted R2 = 0.56 and 1.04 ln-transformed mug/L RMSE with chlorophyll determined by the boosted regression tree remote sensing model. For Great Lakes models, the MODIS BRT model predicted chlorophyll most accurately of the three BRT models and compared well to other models in the literature. BRT models for Landsat ETM+ and TM more accurately predicted chlorophyll than the MSS model and all Landsat models had favorable results when compared to the literature. BRT chlorophyll predictive models are useful in helping to understand historical, long-term chlorophyll trends and to inform us of how climate change may alter ecosystems in the future. In inner Saginaw Bay, annual average and upper quartile Landsat-derived chlorophyll decreased from 7.44 to 6.62 and 8.38 to 7.38 mug/L between 1973-1982, and annual upper quartile of 8-day phosphorus loads increased from 5.29 to 6.79 kg between 1973-2012. Simple linear and multiple regression models and Wilcoxon rank test results for MODIS and Landsat-derived chlorophyll indicate that distance from the Saginaw River mouth influences chlorophyll concentration in Saginaw Bay; Landsat-derived surface water temperature and phosphorus loads to a lesser extent. Mixed-effect models for MODIS and Landsat-derived chlorophyll were related to chlorophyll better than simple linear or multiple regressions, with random effects of pixel and sample date contributing substantially to predictive power (NSE=0.35-70), though phosphorus loads, distance to Saginaw River mouth, and water were significant fixed effects in most models. Water quality changes in Saginaw Bay between 1972-2012 were influenced by phosphorus loading and distance to the Saginaw River's mouth. Landsat and MODIS imagery are complementary platforms because of the long history of Landsat operation and the finer spectral resolution and image frequency of MODIS. Remote sensing water quality assessment tools can be valuable for limnological study, ecological assessment, and water resource management.

Preliminary study on differentiation between glaucomatous and non-glaucomatous eyes on stereo fundus images using cup gradient models

NASA Astrophysics Data System (ADS)

Muramatsu, Chisako; Hatanaka, Yuji; Ishida, Kyoko; Sawada, Akira; Yamamoto, Tetsuya; Fujita, Hiroshi

2014-03-01

Glaucoma is one of the leading causes of blindness in Japan and the US. One of the indices for diagnosis of glaucoma is the cup-to-disc ratio (CDR). We have been developing a computerized method for measuring CDR on stereo fundus photographs. Although our previous study indicated that the method may be useful, cup determination was not always successful, especially for the normal eyes. In this study, we investigated a new method to quantify the likelihood of glaucomatous disc based on the similarity scores to the glaucoma and non-glaucoma models. Eighty-seven images, including 40 glaucomatous eyes, were used in this study. Only one eye from each patient was used. Using a stereo fundus camera, two images were captured from different angles, and the depth image was created by finding the local corresponding points. One of the characteristics of a glaucomatous disc can be not only that the cup is enlarged but it has an acute slope. On the other hand, a non-glaucomatous cup generally has a gentle slope. Therefore, our models were constructed by averaging the depth gradient images. In order to account for disc size, disc outline was automatically detected, and all images were registered by warping the disc outline to a circle with a predetermined diameter using thin plate splines. Similarity scores were determined by multiplying a test case with both models. At the sensitivity of 90.0%, the specificity was improved from 83.0% using the CDR to 97.9% by the model-based method. The proposed method may be useful for differentiation of glaucomatous eyes.

Abundance of Ohio shrimp (Macrobrachium ohione) and Glass shrimp (Palaemonetes kadiakensis) in the unimpounded Upper Mississippi River

USGS Publications Warehouse

Barko, V.A.; Hrabik, R.A.

2004-01-01

Large rivers of the United States have been altered by construction and maintenance of navigation channels, which has resulted in habitat loss and degradation. Using 7 y of Long Term Resource Monitoring Program data collected from the unimpounded upper Mississippi River, we investigated Ohio and Glass Shrimp abundance collected from four physical habitats of the unimpounded upper Mississippi River: main channel border, main channel border with wing dike, open side channel and closed side channel. Our objective was to assess associations between Ohio and Glass Shrimp abundance, environmental measurements and the four habitats to better understand the ecology of these species in a channelized river system. Ohio Shrimp were most abundant in the open side channels, while Glass Shrimp were most abundant in the main channel border wing dike habitat. Thirty-two percent of the variance in Glass Shrimp abundance was explained by year 1995, year 1998, water temperature, depth of gear deployment, Secchi disk transparency and river elevation. Approximately 8% of variation in Ohio Shrimp abundance was explained by Secchi disk transparency. Catch-per-unit-effort (CPUE) was greatest in 1998 for Glass Shrimp but lowest in 1997. Conversely, CPUE was greatest in 1996 for Ohio Shrimp and lowest in 2000. Both species exhibited inter-annual variability in CPUE. Long-term impacts of river modifications on aquatic invertebrates have not been well documented in many large, river systems and warrants further study. The findings from this study provide ecological information on Glass and Ohio Shrimp in a channelized river system.

Evidence for a current sheet forming in the wake of a coronal mass ejection from multi-viewpoint coronagraph observations

NASA Astrophysics Data System (ADS)

Patsourakos, S.; Vourlidas, A.

2011-01-01

Context. Ray-like features observed by coronagraphs in the wake of coronal mass ejections (CMEs) are sometimes interpreted as the white light counterparts of current sheets (CSs) produced by the eruption. The 3D geometry of these ray-like features is largely unknown and its knowledge should clarify their association to the CS and place constraints on CME physics and coronal conditions. Aims: If these rays are related to field relaxation behind CMEs, therefore representing current sheets, then they should be aligned to the CME axis. With this study we test these important implications for the first time. Methods: An example of such a post-CME ray was observed by various coronagraphs, including these of the Sun Earth Connection Coronal and Heliospheric investigation (SECCHI) onboard the Solar Terrestrial Relations Observatory (STEREO) twin spacecraft and the Large Angle Spectrometric Coronagraph (LASCO) onboard the Solar and Heliospheric Observatory (SOHO). The ray was observed in the aftermath of a CME which occurred on 9 April 2008. The twin STEREO spacecraft were separated by about 48° on that day. This significant separation combined with a third “eye” view supplied by LASCO allow for a truly multi-viewpoint observation of the ray and of the CME. We applied 3D forward geometrical modeling to the CME and to the ray as simultaneously viewed by SECCHI-A and B and by SECCHI-A and LASCO, respectively. Results: We found that the ray can be approximated by a rectangular slab, nearly aligned with the CME axis, and much smaller than the CME in both terms of thickness and depth (≈0.05 and 0.15 R⊙ respectively). The ray electron density and temperature were substantially higher than their values in the ambient corona. We found that the ray and CME are significantly displaced from the associated post-CME flaring loops. Conclusions: The properties and location of the ray are fully consistent with the expectations of the standard CME theories for post-CME current sheets. Therefore, our multi-viewpoint observations supply strong evidence that the observed post-CME ray is indeed related to a post-CME current sheet. Movies are only available in electronic form at http://www.aanda.org

3D Modeling of CMEs observed with STEREO

NASA Astrophysics Data System (ADS)

Bosman, E.; Bothmer, V.

2012-04-01

From January 2007 until end of 2010, 565 typical large-scale coronal mass ejections (CMEs) have been identified in the SECCHI/COR2 synoptic movies of the STEREO Mission. A subset comprising 114 CME events, selected based on the CME's brightness appearance in the SECCHI/COR2 images, has been modeled through the Graduated Cylindrical Shell (GCS) Model developed by Thernisien et al. (2006). This study presents an overview of the GCS forward-modeling results and an interpretation of the CME characteristics in relationship to their solar source region properties and solar cycle appearances.

The Disrupted-in-Schizophrenia-1 Ser704Cys polymorphism and brain neurodevelopmental markers in schizophrenia and healthy subjects.

PubMed

Takahashi, Tsutomu; Nakamura, Mihoko; Nakamura, Yukako; Aleksic, Branko; Kido, Mikio; Sasabayashi, Daiki; Takayanagi, Yoichiro; Furuichi, Atsushi; Nishikawa, Yumiko; Noguchi, Kyo; Ozaki, Norio; Suzuki, Michio

2015-01-02

Increasing evidence has implicated the role of Disrupted-in-Schizophrenia-1 (DISC1), a potential susceptibility gene for schizophrenia, in early neurodevelopmental processes. However, the effect of its genotype variation on brain morphologic changes related to neurodevelopmental abnormalities in schizophrenia remains largely unknown. This magnetic resonance imaging study examined the association between DISC1 Ser704Cys polymorphism and a range of brain neurodevelopmental markers [cavum septi pellucidi (CSP), adhesio interthalamica (AI), olfactory sulcus depth, and sulcogyral pattern (Types I, II, III, and IV) in the orbitofrontal cortex (OFC)] in an all Japanese sample of 75 schizophrenia patients and 87 healthy controls. The Cys carriers had significantly larger CSP than the Ser homozygotes for both schizophrenia patients and healthy controls. The Cys carriers also exhibited a reduction in the Type I pattern of the right OFC in the healthy controls, but not in the schizophrenia patients. The DISC1 Ser704Cys polymorphism did not affect the AI and olfactory sulcus depth in either group. These results suggested a possible role of the DISC1 genotype in the early neurodevelopment of human brains, but failed to show its specific role in the neurodevelopmental pathology of schizophrenia. Copyright © 2014 Elsevier Inc. All rights reserved.

African Descent and Glaucoma Evaluation Study (ADAGES)

PubMed Central

Girkin, Christopher A.; Sample, Pamela A.; Liebmann, Jeffrey M.; Jain, Sonia; Bowd, Christopher; Becerra, Lida M.; Medeiros, Felipe A.; Racette, Lyne; Dirkes, Keri A.; Weinreb, Robert N.; Zangwill, Linda M.

2010-01-01

Objective To define differences in optic disc, retinal nerve fiber layer, and macular structure between healthy participants of African (AD) and European descent (ED) using quantitative imaging techniques in the African Descent and Glaucoma Evaluation Study (ADAGES). Methods Reliable images were obtained using stereoscopic photography, confocal scanning laser ophthalmoscopy (Heidelberg retina tomography [HRT]), and optical coherence tomography (OCT) for 648 healthy subjects in ADAGES. Findings were compared and adjusted for age, optic disc area, and reference plane height where appropriate. Results The AD participants had significantly greater optic disc area on HRT (2.06 mm2; P<.001) and OCT (2.47 mm2; P<.001) and a deeper HRT cup depth than the ED group (P<.001). Retinal nerve fiber layer thickness was greater in the AD group except within the temporal region, where it was significantly thinner. Central macular thickness and volume were less in the AD group. Conclusions Most of the variations in optic nerve morphologic characteristics between the AD and ED groups are due to differences in disc area. However, differences remain in HRT cup depth, OCT macular thickness and volume, and OCT retinal nerve fiber layer thickness independent of these variables. These differences should be considered in the determination of disease status. PMID:20457974

Biometry and spectral domain optical coherence tomography parameters in children with large cupping.

PubMed

Jung, Jong Jin; Baek, Seung-Hee; Kim, Ungsoo Samuel

2013-09-01

The purpose of this study is to investigate optic nerve head using spectral domain optical coherence tomography (SD-OCT) in children with large cupping. 111 eyes (4-10 years) were divided into three groups according to the cup to disc ratio: group 1, ≤0.3; group 2, 0.4-0.6; and group 3, ≥0.7. The rim area, disc area, average cup to disc ratio, vertical cup to disc ratio, and cup volume were investigated using SD-OCT (Cirrus HD-OCT, Carl Zeiss, Jena, Germany), and the axial length and anterior chamber depth (ACD) were measured by IOL master (IOL master 500, Carl Zeiss, Jena, Germany). Next, we compared ocular biometry and SD-OCT between the three groups. The mean age of group 1 was 6.48 ± 1.42 years, 7.00 ± 1.75 years in group 2, and 6.63 ± 1.82 years in group 3 (p = 0.370). A significant difference was seen in the spherical equivalent between the groups (p = 0.001). Group 2 had the most myopic refractive errors. As the cup to disc ratio increases, disc area, average cup to disc ratio, vertical cup to disc ratio, and cup volume increase significantly. When the results of ocular biometry and SD-OCT are adjusted for axial length, only disc area showed a significant correlation with cup to disc ratio (ACD: p = 0.473, rim area: p = 0.639, disc area: p = 0.005, and cup volume: p = 0.325). Axial length is the key factor determining disc size, which in turn is important for determining cup to disc ratio. Normal children with large cupping should be examined for axial length, myopic refractive errors, and disc size.

A simple framework for modelling the dependence of bulk Comptonization by turbulence on accretion disc parameters

NASA Astrophysics Data System (ADS)

Kaufman, J.; Blaes, O. M.; Hirose, S.

2018-06-01

Warm Comptonization models for the soft X-ray excess in active galactic nuclei (AGN) do not self-consistently explain the relationship between the Comptonizing medium and the underlying accretion disc. Because of this, they cannot directly connect the fitted Comptonization temperatures and optical depths to accretion disc parameters. Since bulk velocities exceed thermal velocities in highly radiation pressure dominated discs, in these systems bulk Comptonization by turbulence may provide a physical basis in the disc itself for warm Comptonization models. We model the dependence of bulk Comptonization on fundamental accretion disc parameters, such as mass, luminosity, radius, spin, inner boundary condition, and α. In addition to constraining warm Comptonization models, our model can help distinguish contributions from bulk Comptonization to the soft X-ray excess from those due to other physical mechanisms, such as absorption and reflection. By linking the time variability of bulk Comptonization to fluctuations in the disc vertical structure due to magnetorotational instability (MRI) turbulence, our results show that observations of the soft X-ray excess can be used to study disc turbulence in the radiation pressure dominated regime. Because our model connects bulk Comptonization to 1D vertical structure temperature profiles in a physically intuitive way, it will be useful for understanding this effect in future simulations run in new regimes.

Measurement of occlusion of the spinal canal and intervertebral foramen by intervertebral disc bulge

PubMed Central

Cuchanski, Mathieu; Cook, Daniel; Whiting, Donald M.; Cheng, Boyle C.

2011-01-01

Background Disc protrusion has been proposed to be a possible cause of both pain and stenosis in the lower spine. No previous study has described the amount of disc occlusion of the spinal canal and intervertebral foramen that occurs under different loading conditions. The objective of this study was to quantitatively assess the percent occlusion of the spinal canal and intervertebral foramen by disc bulge under different loading conditions. Methods Spinal canal depth and foraminal width were measured on computed tomography–scanned images of 7 human lumbar spine specimens. In vitro disc bulge measurements were completed by use of a previously described method in which single functional spinal units were subjected to 3 separate load protocols in a spine test machine and disc bulge was recorded with an optoelectric motion system that tracked active light-emitting diodes placed on the posterior and posterolateral aspects of the intervertebral disc. Occlusion was defined as percentage of encroachment into area of interest by maximum measured disc bulge at corresponding point of interest (the spinal canal is at the posterior point; the intervertebral foramen is at the posterolateral point). Results The mean spinal canal depth and mean foraminal width were 19 4 ± mm and 5 ± 2 mm, respectively. Mean spinal canal occlusion under a 250-N axial load, ± 2.5 Nm of flexion/extension, and ± 2.5 Nm of lateral bend was 2.5% ± 1.9%, 2.5% ± 1.6%, and 1.5% ± 0.8%, respectively. Mean intervertebral foramen occlusion under a 250-N axial load, ± 2.5 Nm of flexion/extension, and ± 2.5 Nm of lateral bend was 7.8% ± 4.7%, 9.5% ± 5.7%, and 11.3% ± 6.2%, respectively. Conclusion Percent occlusion of the spinal canal and intervertebral foramen is dependent on magnitude and direction of load. Exiting neural elements at the location of the intervertebral foramen are the most vulnerable to impingement and generation of pain. PMID:25802663

Kinematic relationship between missed ligamentum flavum bulge and degenerative factors in the cervical spine.

PubMed

Zhong, Guibin; Buser, Zorica; Lao, Lifeng; Yin, Ruofeng; Wang, Jeffrey C

2015-10-01

Bulging of ligamentum flavum can happen with the aging process and can lead to compression of the spinal cord and nerves. However, the distribution and the risk factors associated with a missed ligamentum flavum bulge (LFB) are unknown. The aim was to evaluate the distribution and risk factors associated with missed LFB in the cervical spine. This was a retrospective analysis of kinematic magnetic resonance images (kMRI). Patients diagnosed with symptomatic neck pain or radiculopathy between March 2011 and October 2012 were included. The outcome measures were missed LFB and degenerative factors. A total of 200 patients (1,000 cervical segments) underwent upright kMRI in neutral, flexion, and extension postures. The LFB, sagittal cervical angles, disc herniation, disc degeneration, disc height, angular motion, translational motion, age, and gender were recorded. After excluding segments with LFB in neutral and flexion position, Pearson and Spearman correlation coefficients were used to evaluate the relation between the risk factors and missed LFB in the extension position. The average depth of LFB was 0.24±0.71 mm at C2-C3, 1.02±1.42 mm at C3-C4, 1.65±1.48 mm at C4-C5, 2.13±1.37 mm at C5-C6, and 1.05±1.54 mm at C6-C7. The distribution of LFB was the most frequent at C5-C6 level (76.58%) followed by C4-C5 (63.06%). Disc herniation, disc degeneration, angular variation, and translational motion were significantly correlated with missed LFB at C4-C5 andC5-C6. Disc degeneration was the only factor significantly correlated with missed LFB at all cervical segments. Occurrence and depth of missed LFB was the highest at C4-C5 and C5-C6 compared with other cervical levels. Disc degeneration, disc herniation, angular variation, and translational motion could play a role in the development of LFB at C4-C5 andC5-C6. Copyright © 2015 Elsevier Inc. All rights reserved.

Topographic optic disc analysis by Heidelberg retinal tomography in ocular Behçet's disease

PubMed Central

Berker, Nilufer; Elgin, Ufuk; Ozdal, Pinar; Batman, Aygen; Soykan, Emel; Ozkan, Seyhan S

2007-01-01

Aim To compare the topographic characteristics of the optic discs in patients with severe and mild ocular Behçet's disease by using Heidelberg retinal tomographaphy (HRT). Methods This prospective study included 47 eyes of 47 patients with ocular BD who were being followed‐up at the Uveitis Clinic of the Ankara Ulucanlar Eye Research Hospital, Ankara, Turkey. The patients were divided into two groups. Group 1 consisted of 21 eyes with mild uveitis, and group 2 consisted of 26 eyes with severe uveitis. All patients underwent topographic optic disc analysis by HRT II, and the quantitative optic disc parameters of both groups were compared by non‐parametric Mann‐Whitney U test. Results The mean cup volume, rim volume, cup area, disc area and cup depth in group 1 were found to be statistically significantly greater than those in group 2 (p<0.0001, p = 0.03, p = 0.021, p = 0.01 and p = 0.017, respectively), while the difference between the mean cup‐to‐disc ratios in group 1 and group 2 were found to be statistically insignificant (p = 0.148). Conclusion A relationship was found between the severity of ocular BD and optic disc topography determined by HRT. In eyes with smaller optic discs, uveitis was observed to have a more severe course with more frequent relapses than those with larger discs. PMID:17475703

Topographic optic disc analysis by Heidelberg retinal tomography in ocular Behcet's disease.

PubMed

Berker, Nilufer; Elgin, Ufuk; Ozdal, Pinar; Batman, Aygen; Soykan, Emel; Ozkan, Seyhan S

2007-09-01

To compare the topographic characteristics of the optic discs in patients with severe and mild ocular Behçet's disease by using Heidelberg retinal tomographaphy (HRT). This prospective study included 47 eyes of 47 patients with ocular BD who were being followed-up at the Uveitis Clinic of the Ankara Ulucanlar Eye Research Hospital, Ankara, Turkey. The patients were divided into two groups. Group 1 consisted of 21 eyes with mild uveitis, and group 2 consisted of 26 eyes with severe uveitis. All patients underwent topographic optic disc analysis by HRT II, and the quantitative optic disc parameters of both groups were compared by non-parametric Mann-Whitney U test. The mean cup volume, rim volume, cup area, disc area and cup depth in group 1 were found to be statistically significantly greater than those in group 2 (p<0.0001, p = 0.03, p = 0.021, p = 0.01 and p = 0.017, respectively), while the difference between the mean cup-to-disc ratios in group 1 and group 2 were found to be statistically insignificant (p = 0.148). A relationship was found between the severity of ocular BD and optic disc topography determined by HRT. In eyes with smaller optic discs, uveitis was observed to have a more severe course with more frequent relapses than those with larger discs.

Assessing the ecological effects of human impacts on coral reefs in Bocas del Toro, Panama.

PubMed

Seemann, Janina; González, Cindy T; Carballo-Bolaños, Rodrigo; Berry, Kathryn; Heiss, Georg A; Struck, Ulrich; Leinfelder, Reinhold R

2014-03-01

Environmental and biological reef monitoring was conducted in Almirante Bay (Bahía Almirante) in Bocas del Toro, Panama, to assess impacts from anthropogenic developments. An integrated monitoring investigated how seasonal temperature stress, turbidity, eutrophication and physical impacts threatened reef health and biodiversity throughout the region. Environmental parameters such as total suspended solids [TSS], carbon isotopes (δ(13)C), C/N ratios, chlorophyll a, irradiance, secchi depth, size fractions of the sediments and isotope composition of dissolved inorganic carbon [DIC] of the water were measured throughout the years 2010 and 2011 and were analysed in order to identify different impact sources. Compared to data from Collin et al. (Smithsonian Contributions to the Marine Sciences 38:324-334, 2009) chlorophyll a has doubled at sites close to the city and the port Almirante (from 0.46-0.49 to 0.78-0.97 μg l(-1)) and suspension load increased, visible by a decrease in secchi depth values. Visibility decreased from 9-13 m down to 4 m at the bay inlet Boca del Drago, which is strongly exposed to river run off and dredging for the shipping traffic. Eutrophication and turbidity levels seemed to be the determining factor for the loss of hard coral diversity, most significant at chlorophyll a levels higher than 0.5 μg l(-1) and TSS levels higher than 4.7 mg l(-1). Hard coral cover within the bay has also declined, at some sites down to <10 % with extremely low diversities (7 hard coral species). The hard coral species Porites furcata dominated the reefs in highly impacted areas and showed a strong recovery after bleaching and a higher tolerance to turbidity and eutrophication compared to other hard coral species in the bay. Serious overfishing was detected in the region by a lack of adult and carnivorous fish species, such as grunts, snappers and groupers. Study sites less impacted by anthropogenic activities and/or those with local protection showed a higher hard coral cover and fish abundance; however, an overall loss of hard coral diversity was observed.

Assessment of predictive models for chlorophyll-a concentration of a tropical lake

PubMed Central

2011-01-01

Background This study assesses four predictive ecological models; Fuzzy Logic (FL), Recurrent Artificial Neural Network (RANN), Hybrid Evolutionary Algorithm (HEA) and multiple linear regressions (MLR) to forecast chlorophyll- a concentration using limnological data from 2001 through 2004 of unstratified shallow, oligotrophic to mesotrophic tropical Putrajaya Lake (Malaysia). Performances of the models are assessed using Root Mean Square Error (RMSE), correlation coefficient (r), and Area under the Receiving Operating Characteristic (ROC) curve (AUC). Chlorophyll-a have been used to estimate algal biomass in aquatic ecosystem as it is common in most algae. Algal biomass indicates of the trophic status of a water body. Chlorophyll- a therefore, is an effective indicator for monitoring eutrophication which is a common problem of lakes and reservoirs all over the world. Assessments of these predictive models are necessary towards developing a reliable algorithm to estimate chlorophyll- a concentration for eutrophication management of tropical lakes. Results Same data set was used for models development and the data was divided into two sets; training and testing to avoid biasness in results. FL and RANN models were developed using parameters selected through sensitivity analysis. The selected variables were water temperature, pH, dissolved oxygen, ammonia nitrogen, nitrate nitrogen and Secchi depth. Dissolved oxygen, selected through stepwise procedure, was used to develop the MLR model. HEA model used parameters selected using genetic algorithm (GA). The selected parameters were pH, Secchi depth, dissolved oxygen and nitrate nitrogen. RMSE, r, and AUC values for MLR model were (4.60, 0.5, and 0.76), FL model were (4.49, 0.6, and 0.84), RANN model were (4.28, 0.7, and 0.79) and HEA model were (4.27, 0.7, and 0.82) respectively. Performance inconsistencies between four models in terms of performance criteria in this study resulted from the methodology used in measuring the performance. RMSE is based on the level of error of prediction whereas AUC is based on binary classification task. Conclusions Overall, HEA produced the best performance in terms of RMSE, r, and AUC values. This was followed by FL, RANN, and MLR. PMID:22372859

Methane and carbon dioxide emissions from 40 lakes along a north–south latitudinal transect in Alaska

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sepulveda-Jauregui, A.; Walter Anthony, K. M.; Martinez-Cruz, K.

Uncertainties in the magnitude and seasonality of various gas emission modes, particularly among different lake types, limit our ability to estimate methane (CH 4) and carbon dioxide (CO 2) emissions from northern lakes. Here we assessed the relationship between CH 4 and CO 2 emission modes in 40 lakes along a latitudinal transect in Alaska to lakes' physicochemical properties and geographic characteristics, including permafrost soil type surrounding lakes. Emission modes included direct ebullition, diffusion, storage flux, and a newly identified ice-bubble storage (IBS) flux. We found that all lakes were net sources of atmospheric CH 4 and CO 2, butmore » the climate warming impact of lake CH 4 emissions was 2 times higher than that of CO 2. Ebullition and diffusion were the dominant modes of CH 4 and CO 2 emissions, respectively. IBS, ~10% of total annual CH 4 emissions, is the release to the atmosphere of seasonally ice-trapped bubbles when lake ice confining bubbles begins to melt in spring. IBS, which has not been explicitly accounted for in regional studies, increased the estimate of springtime emissions from our study lakes by 320%. Geographically, CH 4 emissions from stratified, mixotrophic interior Alaska thermokarst (thaw) lakes formed in icy, organic-rich yedoma permafrost soils were 6-fold higher than from non-yedoma lakes throughout the rest of Alaska. The relationship between CO 2 emissions and geographic parameters was weak, suggesting high variability among sources and sinks that regulate CO 2 emissions (e.g., catchment waters, pH equilibrium). Total CH 4 emission was correlated with concentrations of soluble reactive phosphorus and total nitrogen in lake water, Secchi depth, and lake area, with yedoma lakes having higher nutrient concentrations, shallower Secchi depth, and smaller lake areas. In conclusion, our findings suggest that permafrost type plays important roles in determining CH 4 emissions from lakes by both supplying organic matter to methanogenesis directly from thawing permafrost and by enhancing nutrient availability to primary production, which can also fuel decomposition and methanogenesis.« less

Methane and carbon dioxide emissions from 40 lakes along a north–south latitudinal transect in Alaska

DOE PAGES

Sepulveda-Jauregui, A.; Walter Anthony, K. M.; Martinez-Cruz, K.; ...

2015-06-02

Uncertainties in the magnitude and seasonality of various gas emission modes, particularly among different lake types, limit our ability to estimate methane (CH 4) and carbon dioxide (CO 2) emissions from northern lakes. Here we assessed the relationship between CH 4 and CO 2 emission modes in 40 lakes along a latitudinal transect in Alaska to lakes' physicochemical properties and geographic characteristics, including permafrost soil type surrounding lakes. Emission modes included direct ebullition, diffusion, storage flux, and a newly identified ice-bubble storage (IBS) flux. We found that all lakes were net sources of atmospheric CH 4 and CO 2, butmore » the climate warming impact of lake CH 4 emissions was 2 times higher than that of CO 2. Ebullition and diffusion were the dominant modes of CH 4 and CO 2 emissions, respectively. IBS, ~10% of total annual CH 4 emissions, is the release to the atmosphere of seasonally ice-trapped bubbles when lake ice confining bubbles begins to melt in spring. IBS, which has not been explicitly accounted for in regional studies, increased the estimate of springtime emissions from our study lakes by 320%. Geographically, CH 4 emissions from stratified, mixotrophic interior Alaska thermokarst (thaw) lakes formed in icy, organic-rich yedoma permafrost soils were 6-fold higher than from non-yedoma lakes throughout the rest of Alaska. The relationship between CO 2 emissions and geographic parameters was weak, suggesting high variability among sources and sinks that regulate CO 2 emissions (e.g., catchment waters, pH equilibrium). Total CH 4 emission was correlated with concentrations of soluble reactive phosphorus and total nitrogen in lake water, Secchi depth, and lake area, with yedoma lakes having higher nutrient concentrations, shallower Secchi depth, and smaller lake areas. In conclusion, our findings suggest that permafrost type plays important roles in determining CH 4 emissions from lakes by both supplying organic matter to methanogenesis directly from thawing permafrost and by enhancing nutrient availability to primary production, which can also fuel decomposition and methanogenesis.« less

Dissolved oxygen stratification and response to thermal structure and long-term climate change in a large and deep subtropical reservoir (Lake Qiandaohu, China).

PubMed

Zhang, Yunlin; Wu, Zhixu; Liu, Mingliang; He, Jianbo; Shi, Kun; Zhou, Yongqiang; Wang, Mingzhu; Liu, Xiaohan

2015-05-15

From January 2010 to March 2014, detailed depth profiles of water temperature, dissolved oxygen (DO), and chromophoric dissolved organic matter (CDOM) were collected at three sites in Lake Qiandaohu, a large, deep subtropical reservoir in China. Additionally, we assessed the changes in DO stratification over the past 61 years (1953-2013) based on our empirical models and long-term air temperature and transparency data. The DO concentration never fell below 2 mg/L, the critical value for anoxia, and the DO depth profiles were closely linked to the water temperature depth profiles. In the stable stratification period in summer and autumn, the significant increase in CDOM in the metalimnion explained the decrease in DO due to the oxygen consumed by CDOM. Well-developed oxygen stratification was detected at the three sites in spring, summer and autumn and was associated with thermal stratification. Oxycline depth was significantly negatively correlated with daily air temperature and thermocline thickness but significantly positively correlated with thermocline depth during the stratification weakness period (July-February). However, there were no significant correlations among these parameters during the stratification formation period (March-June). The increase of 1.67 °C in yearly average daily air temperature between 1980 and 2013 and the decrease of 0.78 m in Secchi disk depth caused a decrease of 1.65 m and 2.78 m in oxycline depth, respectively, facilitating oxygen stratification and decreasing water quality. Therefore, climate warming has had a substantial effect on water quality through changing the DO regime in Lake Qiandaohu. Copyright © 2015 Elsevier Ltd. All rights reserved.

Microstructure of the optic disc pit in open-angle glaucoma.

PubMed

Choi, Yun Jeong; Lee, Eun Ji; Kim, Bo Hyuk; Kim, Tae-Woo

2014-11-01

To investigate the structural and clinical characteristics of the optic disc pit (ODP) in primary open-angle glaucoma (POAG) via enhanced depth imaging (EDI) spectral-domain optical coherence tomography (SD-OCT). Prospective, observational case series. Seventy POAG eyes clinically diagnosed with an ODP via stereo disc photography. Optic discs were scanned using EDI SD-OCT. Serial horizontal and vertical B-scan images covering the optic discs were obtained from each eye. The structural characteristics of the ODP were investigated via 3-dimensional images constructed from the serial B-scans, focusing on the presence of alterations in the contour of the lamina cribrosa (LC) or prelaminar tissue (PLT), in conjunction with associated clinical characteristics. The structural characteristics of the ODP and associated clinical characteristics. In the EDI SD-OCT images, the ODP was viewed as an isolated alteration of the LC (n = 14, 20.0%) or PLT (n = 16, 22.9%) or an alteration of both the LC and PLT (n = 40, 57.1%). Alterations of the LC were located at the mid-periphery near the LC insertion (n = 17) or far periphery adjacent to the LC insertion (n = 37), and the depth of alteration was deep (n = 23), involving nearly full-thickness LC, or shallow (n = 31), with partially visible LC at the base. Fifty-four eyes (77.1%) exhibited parafoveal visual field (VF) defect within 10 degrees of fixation, and in 98.1% of these eyes (53/54) it was spatially associated with the location of ODP. The parafoveal VF defect was more prevalent in eyes with LC alteration than those without (83.3% vs. 56.2%, P = 0.023) and in eyes with deep LC defect than those with shallow defect (95.7% vs. 74.2%, P = 0.036). Disc hemorrhage (32.4% vs. 0.0%, P = 0.008) and peripapillary retinoschisis (18.9 vs. 0.0%, P = 0.055) were more strongly associated with LC alterations located at the far periphery than at the mid-periphery. Enhanced depth imaging SD-OCT facilitated visualization of the varied structure of the ODP, which presented as alteration of the LC or PLT or both. The clinical significance of differing characteristics of ODP microstructure remains to be determined. Copyright © 2014 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

Presence and distribution of nitrate and selected pesticides in surficial-sand aquifers and selected lakes, 1983-94, East Otter Tail County, Minnesota

USGS Publications Warehouse

Smith, Shannon E.; Ruhl, James E.

1995-01-01

Lake water was sampled from 11 sites on Little Pine, Big Pine, Rush, and Otter Tail Lakes. Nitrate-nitrogen concentrations were all below the detection limit (0.05 mg/L). The concentration of triazine herbicide compounds, as determined by immunoassay, was at or below the detection limit (0.10 ug/L) at all 11 sites. Dissolved oxygen concentrations at the sites ranged from 7.3 to 10.1 mg/L at the water surface, and from 5.3 to 9.7 mg/L at depth. Secchi disk transparency readings ranged from 4.0 to 7.4 feet. Total phosphorus concentrations were generally near or below the detection limit (0.01 mg/L) except at one site where the water had a total phosphorus concentration of 0.06 mg/L.

Water-quality data for selected sites on Reversed, Rush, and Alger Creeks and Gull and Silver Lakes, Mono County, California, April 1994 to March 1995

USGS Publications Warehouse

Wang, Bronwen; Rockwell, G.L.; Blodgett, J.C.

1995-01-01

Water-quality data for selected sites on Reversed, Rush, and Alger Creeks and Gull and Silver Lakes, Mono County, California, were collected from April 1994 to March 1995. Water samples were analyzed for major ions and trace elements, nutrients, methylene blue active substances, and oil and grease. Field measurements were made for discharge, specific conductance, pH, water temperature, barometric pressure, dissolved oxygen, and alkalinity. Additional data collected include vertical water profiles of specific conductance, pH, water temperature, and dissolved oxygen collected at 3.3-foot intervals for Gull and Silver Lakes; chlorophyll-a and -b concentrations and Secchi depth for Gull and Silver Lakes; sediment interstitial- water nutrient concentrations in cores from Gull Lake; and lake surface and volume of Gull and Silver Lakes.

Effects of smallmouth buffalo, Ictiobus bubalus biomass on water transparency, nutrients, and productivity in shallow experimental ponds.

PubMed

Goetz, D; Kröger, R; Miranda, L E

2014-05-01

The smallmouth buffalo Ictiobus bubalus is a native benthivore to floodplain lakes in the Yazoo River Basin, USA. Based on evidence from other benthivorous fish studies we hypothesized high biomasses of I. bubalus contribute to poor water quality conditions. We tested this hypothesis in shallow (<1.5 m) 0.05 ha earthen ponds at three stocking biomasses over a 10-week period during the summer of 2012. The most notable results from the permutational multivariate analysis of variance suggest I. bubalus at high and moderate biomasses significantly (p < 0.05) enhanced turbidity and suspended solid levels while decreasing Secchi depth. Our results suggest that effects of I. bubalus on water clarity may have considerable ecological implications in natural habitats such as shallow floodplain lakes.

Sources and cycling of major ions and nutrients in Devils Lake, North Dakota

USGS Publications Warehouse

Lent, R.M.

1994-01-01

Devils Lake is a saline lake in a large, closed drainage basin in northeastern North Dakota. Previous studies determined that major-ion and nutrient concentrations in Devils Lake are strongly affected by microbially mediated sulfate reduction and dissolution of sulfate and carbonate minerals in the bottom sediments. These studies documented substantial spatial variability in the magnitude of calculated benthic fluxes coincident with the horizontal salinity gradient in Devils Lake. The purpose of the present study is to evaluate seasonal variability in benthic-flux rates, and to understand the effect of these fluxes on the major-ion and nutrient chemistries in Devils Lake between May and October 1991. During the study period, the water column was well mixed, and specific conductance, pH, and temperature did not vary with depth. Dissolved oxygen was enriched near the lake surface due to photosynthesis. Major-ion concentrations and nutrient concentrations did not vary with depth. Because the water-quality data were obtained during open-water periods, the vertical profiles reflect well-mixed conditions. However, the first and last profiles for the study period did document near-bottom maxima of major cations. Secchi-disk depth varied from 0.82 meter on May 7,1991, to 2.13 meters on June 5, 1991. The mean Secchi-disk depth during the study period was 1.24 meters. Seasonal variations in Secchi-disk depths were attributed to variations in primary productivity and phytoplankton communities. Nutrient cycles in Devils Lake were evaluated using gross primary productivity rate data, sediment trap data, and major-ion and nutrient benthic-flux rate data. Gross primary productivity rate was smallest in May (0.076 gram of carbon per square meter per day) and largest in September (1.8 grams of carbon per square meter per day). Average gross primary productivity for the study period was 0.87 gram of carbon per square meter per day. Average gross primary productivity is consistent with historic data from Devils Lake and with data from other eutrophic lakes.The average flux of organic carbon for the study period was 12 grams per square meter per day. The calculated carbon to nitrogen to phosphorus ratio (317:25:1) is similar to the Redfield ratio (106:16:1); therefore, most organic matter probably is derived from lacustrine phytoplankton.Calculated benthic-flux rates indicated that bottom sediments are important sources of majorions and nutrients to Devils Lake. Only one of the cores collected during this study indicated a net sulfate flux from the lake into the sediments. Seasonal variations in major-ion and nutrient benthic fluxes generally were small. However, there were important differences between the calculated benthic fluxes for this study and the calculated benthic fluxes for 1990. Calculated benthic fluxes of bicarbonate, ammonia, and phosphorus for this study were smaller than calculated benthic fluxes for 1990. The large differences between fluxes for 1990 and 1991 were attributed to calm, stratified water-column conditions in 1990 and well-mixed water-column conditions in 1991.The role of benthic fluxes in the chemical mass balances in Devils Lake was evaluated by calculating response times for major ions and nutrients in Devils Lake. The calculated response times for major ions in Devils Lake ranged from 6.7 years for bicarbonate to 34 years for sulfur (as 804). The response times for major ions are significantly shorter than previous estimates that did not include benthic fluxes. In addition, the relatively short response times for nitrogen (4.2 years) and phosphorus (0.95 year) indicate that nutrients are recycled rapidly between bottom sediments and the lake. During the study period, benthic fluxes were the dominant source of major ions and nutrients to Devils Lake and greatly reduced the response times of all major ions and nutrients for Devils Lake. As a result, bottom-sediment processes appear to buffer major-ion and nutrient concentrations in the lake. Any future attempt to evaluate water quality in Devils Lake should include the effects of bottom-sediment processes.

SDSS-IV MaNGA: constraints on the conditions for star formation in galaxy discs

NASA Astrophysics Data System (ADS)

Stark, David V.; Bundy, Kevin A.; Orr, Matthew E.; Hopkins, Philip F.; Westfall, Kyle; Bershady, Matthew; Li, Cheng; Bizyaev, Dmitry; Masters, Karen L.; Weijmans, Anne-Marie; Lacerna, Ivan; Thomas, Daniel; Drory, Niv; Yan, Renbin; Zhang, Kai

2018-02-01

Regions of disc galaxies with widespread star formation tend to be both gravitationally unstable and self-shielded against ionizing radiation, whereas extended outer discs with little or no star formation tend to be stable and unshielded on average. We explore what drives the transition between these two regimes, specifically whether discs first meet the conditions for self-shielding (parametrized by dust optical depth, τ) or gravitational instability (parametrized by a modified version of Toomre's instability parameters, Qthermal, which quantifies the stability of a gas disc that is thermally supported at T = 104 K). We first introduce a new metric formed by the product of these quantities, Qthermalτ, which indicates whether the conditions for disc instability or self-shielding are easier to meet in a given region of a galaxy, and we discuss how Qthermalτ can be constrained even in the absence of direct gas information. We then analyse a sample of 13 galaxies with resolved gas measurements and find that on average galaxies will reach the threshold for disc instabilities (Qthermal < 1) before reaching the threshold for self-shielding (τ > 1). Using integral field spectroscopic observations of a sample of 236 galaxies from the Mapping Nearby Galaxies at APO (MaNGA) survey, we find that the value of Qthermalτ in star-forming discs is consistent with similar behaviour. These results support a scenario where disc fragmentation and collapse occurs before self-shielding, suggesting that gravitational instabilities are the primary condition for widespread star formation in galaxy discs. Our results support similar conclusions based on recent galaxy simulations.

Ocular characteristics associated with the location of focal lamina cribrosa defects in open-angle glaucoma patients.

PubMed

Park, H-Yl; Hwang, Y S; Park, C K

2017-04-01

PurposeTo investigate the clinical characteristics according to the location of focal lamina cribrosa (LC) defects and its associated ocular features.Patients and methodsA total of 139 open-angle glaucoma patients underwent Spectralis optical coherence tomography (OCT) with enhanced depth imaging. Alterations in the contour of the LC were investigated to find focal LC defects. The location of the visible LC defect from the neural canal wall (far-peripheral and mid-peripheral) and clock-hour position (superotemporal, temporal and inferotemporal) were classified. Disc ovality ratio and disc-foveal angle were measured from disc and retinal nerve fiber layer (RNFL) photographs. The disc tilt degree was measured using a Heidelberg Retina Tomograph (HRT) III system. The en face OCT image of the disc scans was registered to the disc and RNFL photographs, to determine whether the focal LC defects corresponded spatially to the glaucomatous damage location.ResultsEyes with far-peripheral LC defects were significantly myopic and had a higher disc ovality ratio. The disc tilt degree obtained by HRT revealed significant temporal disc tilt in eyes with temporal LC defects (P<0.001). Eyes with inferotemporal LC defects had a significantly larger disc-foveal angle (P=0.027). The inferotemporal LC defects corresponded to the location of glaucomatous damage in 81.6%; however, only 46.2% of eyes with a superotemporal LC defect and 3.2% of eyes with a temporal LC defect corresponded spatially with the glaucomatous damage location.ConclusionsThe clinical characteristics and association with glaucomatous damage location were different according to the location of focal LC defect.

Comparison of CME three-dimensional parameters derived from single and multi-spacecraft

NASA Astrophysics Data System (ADS)

LEE, Harim; Moon, Yong-Jae; Na, Hyeonock; Jang, Soojeong

2014-06-01

Several geometrical models (e.g., cone and flux rope models) have been suggested to infer three-dimensional parameters of CMEs using multi-view observations (STEREO/SECCHI) and single-view observations (SOHO/LASCO). To prepare for when only single view observations are available, we have made a test whether the cone model parameters from single-view observations are consistent with those from multi-view ones. For this test, we select 35 CMEs which are identified as CMEs, whose angular widths are larger than 180 degrees, by one spacecraft and as limb CMEs by the other ones. For this we use SOHO/LASCO and STEREO/SECCHI data during the period from 2010 December to 2011 July when two spacecraft were separated by 90±10 degrees. In this study, we compare the 3-D parameters of these CMEs from three different methods: (1) a triangulation method using STEREO/SECCHI and SOHO/LASCO data, (2) a Graduated Cylindrical Shell (GCS) flux rope model using STEREO/SECCHI data, and (3) an ice cream cone model using SOHO/LASCO data. The parameters used for comparison are radial velocities, angular widths and source location (angle γ between the propagation direction and the plan of the sky). We find that the radial velocities and the γ-values from three methods are well correlated with one another (CC > 0.8). However, angular widths from the three methods are somewhat different with the correlation coefficients of CC > 0.4. We also find that the correlation coefficients between the locations from the three methods and the active region locations are larger than 0.9, implying that most of the CMEs are radially ejected.

Response of fishes to floodplain connectivity during and following a 500-year flood event in the unimpounded upper Mississippi River

USGS Publications Warehouse

Barko, V.A.; Herzog, D.P.; O'Connell, M. T.

2006-01-01

We examined data collected on fish assemblage structure among three differing floodplain types (broad, moderate, and narrow) during the 1993 flood in the unimpounded reach of the upper Mississippi River. This 500 year flood event provided a unique opportunity to investigate fish-floodplain function because the main river channel is otherwise typically disjunct from approximately 82% of its floodplain by an extensive levee system. Fishes were sampled during three separate periods, and 42 species of adult and young-of-the-year (YOY) fishes were captured. Analysis of similarity (ANOSIM) revealed a significant and distinguishable difference between both adult and YOY assemblage structure among the three floodplain types. Analysis of variance revealed that Secchi transparency, turbidity, water velocity, and dissolved oxygen were significantly different among the floodplain types. However, only depth of gear deployment and Secchi transparency were significantly correlated with adult assemblage structure. None of these variables were significantly correlated with YOY assemblage structure. The numerically abundant families (adult and YOY catches combined) on the floodplain included Centrarchidae, Ictularidae, and Cyprinidae. Both native and non-native fishes were captured on the floodplain, and several of the numerically abundant species that were captured on the floodplain peaked in catch-per-unit-effort 1-3 years after the 1993 flood event. This suggests that some species may have used flooded terrestrial habitat for spawning, feeding, or both. The findings from our study provide much needed insight into fish-floodplain function in a temperate, channelized river system and suggest that lateral connectivity of the main river channel to less degraded reaches of its floodplain should become a management priority not only to maintain faunal biodiversity but also potentially reduce the impacts of non-native species in large river systems.

Analysis of optic disc change using the heidelberg retina tomograph in an acquired pit of the optic nerve.

PubMed

Oh, Joo Youn; Park, Ki Ho

2004-01-01

A 51-year-old woman diagnosed as having normal-tension glaucoma developed an acquired pit of the optic nerve. The optic disc was viewed by the Heidelberg Retina Tomograph (HRT; Heidelberg Engineering, Heidelberg, Germany) before and after development of an acquired pit of the optic nerve. HRT parameters and cross-sectional images of the optic disc were compared. Maximum cup depth at the site of the acquired pit of the optic nerve increased after development of the acquired pit of the optic nerve (from 1.200 to 2.432 mm). The neuroretinal rim area and volume in the inferotemporal octant were reduced (rim area from 0.070 to 0.010 mm2, rim volume from 0.009 to 0.001 mm3). The morphologic changes in the optic disc were also detected topographically and reflectively.

Changes in water clarity in response to river discharges on the Great Barrier Reef continental shelf: 2002-2013

NASA Astrophysics Data System (ADS)

Fabricius, K. E.; Logan, M.; Weeks, S. J.; Lewis, S. E.; Brodie, J.

2016-05-01

Water clarity is a key factor for the health of marine ecosystems. The Australian Great Barrier Reef (GBR) is located on a continental shelf, with >35 major seasonal rivers discharging into this 344,000 km2 tropical to subtropical ecosystem. This work investigates how river discharges affect water clarity in different zones along and across the GBR. For each day over 11 years (2002-2013) we calculated 'photic depth' as a proxy measure of water clarity (calibrated to be equivalent to Secchi depth), for each 1 km2 pixel from MODIS-Aqua remote sensing data. Long-term and seasonal changes in photic depth were related to the daily discharge volumes of the nearest rivers, after statistically removing the effects of waves and tides on photic depth. The relationships between photic depths and rivers differed across and along the GBR. They typically declined from the coastal to offshore zones, and were strongest in proximity to rivers in agriculturally modified catchments. In most southern inner zones, photic depth declined consistently throughout the 11-year observation period; such long-term trend was not observed offshore nor in the northern regions. Averaged across the GBR, photic depths declined to 47% of local maximum values soon after the onset of river floods, and recovery to 95% of maximum values took on average 6 months (range: 150-260 days). The river effects were strongest at latitude 14.5°-19.0°S, where river loads are high and the continental shelf is narrow. Here, even offshore zones showed a >40% seasonal decline in photic depth, and 17-24% reductions in annual mean photic depth in years with large river nutrients and sediment loads. Our methodology is based on freely available data and tools and may be applied to other shelf systems, providing valuable insights in support of ecosystem management.

Intercomparison of the LASCO-C2, SECCHI-COR1, SECCHI-COR2, and Mk4 Coronagraphs

NASA Technical Reports Server (NTRS)

Frazin, Richard A.; Vasquez, Alberto M.; Thompson, William T.; Hewett, Russell J.; Lamy, Philippe; Llebaria, Antoine; Vourlidas, Angelos; Burkepile, Joan

2012-01-01

In order to assess the reliability and consistency of white-light coronagraph measurements, we report on quantitative comparisons between polarized brightness [pB] and total brightness [B] images taken by the following white-light coronagraphs: LASCO-C2 on SOHO, SECCHI-COR1 and -COR2 on STEREO, and the ground-based MLSO-Mk4. The data for this comparison were taken on 16 April 2007, when both STEREO spacecraft were within 3.1 deg. of Earth’s heliographic longitude, affording essentially the same view of the Sun for all of the instruments. Due to the difficulties of estimating stray-light backgrounds in COR1 and COR2, only Mk4 and C2 produce reliable coronal-hole values (but not at overlapping heights), and these cannot be validated without rocket flights or ground-based eclipse measurements. Generally, the agreement between all of the instruments’ pB values is within the uncertainties in bright streamer structures, implying that measurements of bright CMEs also should be trustworthy. Dominant sources of uncertainty and stray light are discussed, as is the design of future coronagraphs from the perspective of the experiences with these instruments.

Characterizing light attenuation within Northwest Florida ...

EPA Pesticide Factsheets

Water Quality (WQ) condition is based on ecosystem stressor indicators (e.g. water clarity) which are biogeochemically important and critical when considering the Deepwater Horizon oil spill restoration efforts under the 2012 RESTORE Act. Nearly all of the proposed RESTORE projects list restoring WC as a goal, but 90% neglect water clarity. Here, dynamics of optical constituents impacting clarity are presented from a 2009-2011 study within Pensacola, Choctawhatchee, St. Andrew and St. Joseph estuaries (targeted RESTORE sites) in Northwest Florida. Phytoplankton were the smallest contribution to total absorption (at-wPAR) at 412 nm (5-11%), whereas colored dissolved organic matter was the largest (61-79%). Estuarine at-wPAR was significantly related to light attenuation (KdPAR), where individual contributors to clarity and the influence of climatic events were discerned. Provided are conversion equations demonstrating interoperability of clarity indicators between traditional State-measured WQ measures (e.g. secchi disc), optical constituents, and even satellite remote sensing for obtaining baseline assessments. This paper arose from efforts under SSWR and SHC to utilize water quality data as baseline measures for RESTORE Act monitoring in Florida estuaries. This paper aims to (1) describe dynamics of optical constituents that impact water clarity in four NW Florida estuaries, and (2) make a case for the total absorption coefficient (at-wPAR) as a valuable

Functional parameter screening for predicting durability of rolling sliding contacts with different surface finishes

NASA Astrophysics Data System (ADS)

Dimkovski, Z.; Lööf, P.-J.; Rosén, B.-G.; Nilsson, P. H.

2018-06-01

The reliability and lifetime of machine elements such as gears and rolling bearings depend on their wear and fatigue resistance. In order to screen the wear and surface damage, three finishing processes: (i) brushing, (ii) manganese phosphating and (iii) shot peening were applied on three disc pairs and long-term tested on a twin-disc tribometer. In this paper, the elastic contact of the disc surfaces (measured after only few revolutions) was simulated and a number of functional and roughness parameters were correlated. The functional parameters consisted of subsurface stresses at different depths and a new parameter called ‘pressure spikes’ factor’. The new parameter is derived from the pressure distribution and takes into account the proximity and magnitude of the pressure spikes. Strong correlations were found among the pressure spikes’ factor and surface peak/height parameters. The orthogonal shear stresses and Von Mises stresses at the shallowest depths under the surface have shown the highest correlations but no good correlations were found when the statistics of the whole stress fields was analyzed. The use of the new parameter offers a fast way to screen the durability of the contacting surfaces operating at similar conditions.

Monitoring coastal water properties and circulation from ERTS-1. [Delaware Bay

NASA Technical Reports Server (NTRS)

Klemas, V. (Principal Investigator)

1973-01-01

The author has identified the following significant results. Imagery and digital tapes from nine successful ERTS-1 passes over Delaware Bay during different portions of the tidal cycle have been analyzed with special emphasis on turbidity, current circulation, waste disposal plumes, and convergent boundaries between different water masses. ERTS-1 image radiance correlated well with Secchi depth and suspended sediment concentration. MSS band 5 seemed to give the best representation of sediment load in the upper one meter of the water column. Circulation patterns observed by ERTS-1 during different parts of the tidal cycle, agreed well with predicted and measured currents throughout Delaware Bay. During flood tide the suspended sediment as visible from ERTS-1 also correlated well with the depth profile. Convergent shear boundaries between different water masses were observed from ERTS-1, with foam lines containing high concentrations of lead, mercury, and other toxic substances. Several fronts have been seen. Those near the mouth of the bay are associated with the tidal intrusion of shelf water. Fronts in the interior of the bay on the Delaware side appear to be associated with velocity shears induced by differences in bottom topography. Waste disposal plumes have benn detected 36 miles offshore.

Spatial and Temporal Variations of Water Quality and Trophic Status in Sembrong Reservoir, Johor

NASA Astrophysics Data System (ADS)

Intan Najla Syed Hashim, Syarifah; Hidayah Abu Talib, Siti; Salleh Abustan, Muhammad

2018-03-01

A study of spatial and temporal variations on water quality and trophic status was conducted to determine the temporal (average reading by month) and spatial variations of water quality in Sembrong reservoir and to evaluate the trophic status of the reservoir. Water samples were collected once a month from November 2016 to June 2017 in seventeen (17) sampling stations at Sembrong Reservoir. Results obtained on the concentration of dissolved oxygen (DO), water temperature, pH and secchi depth had no significant differences compared to Total Phosphorus (TP) and chlorophyll-a. The water level has significantly decreased the value of the water temperature, pH and TP. The water quality of Sembrong reservoir is classified in Class II which is suitable for recreational uses and required conventional treatment while TSI indicates that sembrong reservoir was in lower boundary of classical eutrophic (TSI > 50).

Dynamic study of the upper Sao Francisco river and Tres Marias reservoir using MSS/LANDSAT images. M.S. Thesis; [BRazil

NASA Technical Reports Server (NTRS)

Dejesusparada, N. (Principal Investigator); Sausen, T. M.

1981-01-01

The relationship between the dispersion and concentration of sediment in the superficial layers of the Tres Marias reservoir and the dynamics of the drainage basins of its tributaries was verified using LANDSAT MSS imagery. The drainage network, dissection patterns, and land use of each watershed were considered in an analysis of multispectral images, corresponding to bands 4,5, and 7, of dry and rainy seasons in 1973, 1975, 1977, and 1978. The superficial layer water layers of the reservoir were also divided according to the grey level pattern of each image. Two field trips were made to collect Secchi depths and in situ water reflectance. It is concluded that it is possible to determine the main factors that act in the dynamics of the drainage basins of a reservoir by simultaneous control of the physical variables and the antropic action of each basin.

Reconciling catch differences from multiple fishery independent gill net surveys

USGS Publications Warehouse

Kraus, Richard T.; Vandergoot, Christopher; Kocovsky, Patrick M.; Rogers, Mark W.; Cook, H. Andrew; Brenden, Travis O.

2017-01-01

Fishery independent gill net surveys provide valuable demographic information for population assessment and resource management, but relative to net construction, the effects of ancillary species, and environmental variables on focal species catch rates are poorly understood. In response, we conducted comparative deployments with three unique, inter-agency, survey gill nets used to assess walleye Sander vitreus in Lake Erie. We used an information-theoretic approach with Akaike’s second-order information criterion (AICc) to evaluate linear mixed models of walleye catch as a function of net type (multifilament and two types of monofilament netting), mesh size (categorical), Secchi depth, temperature, water depth, catch of ancillary species, and interactions among selected variables. The model with the greatest weight of evidence showed that walleye catches were positively associated with potential prey and intra-guild predators and negatively associated with water depth and temperature. In addition, the multifilament net had higher average walleye catches than either of the two monofilament nets. Results from this study both help inform decisions about proposed gear changes to stock assessment surveys in Lake Erie, and advance our understanding of how multispecies associations explain variation in gill net catches. Of broader interest to fishery-independent gill net studies, effects of abiotic variables and ancillary species on focal specie’s catch rates were small in comparison with net characteristics of mesh size or twine type.

Disc origin of broad optical emission lines of the TDE candidate PTF09djl

NASA Astrophysics Data System (ADS)

Liu, F. K.; Zhou, Z. Q.; Cao, R.; Ho, L. C.; Komossa, S.

2017-11-01

An otherwise dormant supermassive black hole (SMBH) in a galactic nucleus flares up when it tidally disrupts a star passing by. Most of the tidal disruption events (TDEs) and candidates discovered in the optical/UV have broad optical emission lines with complex and diverse profiles of puzzling origin. In this Letter, we show that the double-peaked broad H α line of the TDE candidate PTF09djl can be well modelled with a relativistic elliptical accretion disc and the peculiar substructures with one peak at the line rest wavelength and the other redshifted to about 3.5 × 104 km s-1 are mainly due to the orbital motion of the emitting matter within the disc plane of large inclination 88° and pericentre orientation nearly vertical to the observer. The accretion disc has an extreme eccentricity 0.966 and semimajor axis of 340 BH Schwarzschild radii. The viewing angle effects of large disc inclination lead to significant attenuation of He emission lines originally produced at large electron scattering optical depth and to the absence/weakness of He emission lines in the spectra of PTF09djl. Our results suggest that the diversities of line intensity ratios among the line species in optical TDEs are probably due to the differences of disc inclinations.

Lights and shadows: multi-wavelength analysis of young stellar objects and their protoplanetary discs

NASA Astrophysics Data System (ADS)

Rigon, Laura

2016-03-01

Stars form from the collapse of molecular clouds and evolve in an environment rich in gas and dust before becoming Main Sequence stars. During this phase, characterised by the presence of a protoplanetary disc, stars manifest changes in the structure and luminosity. This thesis performs a multi-wavelength analysis, from optical to mm range, on a sample of young stars (YSOs), mainly Classical T Tauri (CTTS). The purpose is to study optical and infrared variability and its relation with the protoplanetary disc. Longer wavelength, in the mm range, are used instead to investigate the evolution of the disc, in terms of dust growth. In optical, an F-test on a sample of 39 CTTS reveals that 67% of the stars are variable. The variability, quantified through pooled sigma, is visible both in magnitude amplitudes and changes over time. Time series analysis applied on the more variable stars finds the presence of quasi periodicity, with periods longer than two weeks, interpreted either as eclipsing material in the disc happening on a non-regular basis, or as a consequence of star-disc interaction via magnetic field lines. The variability of YSOs is confirmed also in infrared, even if with lower amplitude. No strong correlations are found between optical and infrared variability, which implies a different cause or a time shift in the two events. By using a toy model to explore their origin, I find that infrared variations are likely to stem from emissions in the inner disc. The evolution of discs in terms of dust growth is confirmed in most discs by the analysis of the slope of the spectral energy distribution (SED), after correcting for wind emission and optical depth effects. However, the comparison with a radiative transfer model highlights that a number of disc parameters, in particular disc masses and temperature, dust size distribution and composition, can also affect the slope of the SED.

In-depth analysis of bicycle hydraulic disc brakes

NASA Astrophysics Data System (ADS)

Maier, Oliver; Györfi, Benedikt; Wrede, Jürgen; Arnold, Timo; Moia, Alessandro

2017-10-01

Hydraulic Disc Brakes (HDBs) represent the most recent and innovative bicycle braking system. Especially Electric Bicycles (EBs), which are becoming more and more popular, are equipped with this powerful, unaffected by environmental influences, and low-wear type of brakes. As a consequence of the high braking performance, typical bicycle braking errors lead to more serious accidents. This is the starting point for the development of a Braking Dynamics Assistance system (BDA) to prevent front wheel lockup and nose-over (falling over the handlebars). One of the essential prerequisites for the system design is a better understanding of bicycle HDBs' characteristics. A physical simulation model and a test bench have been built for this purpose. The results of the virtual and real experiments conducted show a high correlation and allow valuable insights into HDBs on bicycles, which have not been studied scientifically in any depth so far.

3D Observations techniques for the solar corona

NASA Astrophysics Data System (ADS)

Portier-Fozzani, F.; Papadopoulo, T.; Fermin, I.; Bijaoui, A.; Stereo/Secchi 3D Team; et al.

In this talk, we will present a review of the different 3D techniques concerning observations of the solar corona made by EUV imageur (such as SOHO/EIT and STEREO/SECCHI) and by coronagraphs (SOHO/LASCO and STEREO/SECCHI). Tomographic reconstructions need magnetic extrapolation to constraint the model (classical triangle mash reconstruction, or more evoluated pixon method). For 3D reconstruction the other approach is stereovision. Stereoscopic techniques are built in a specific way to take into account the optical thin medium of the solar corona, which makes most of the classical stereo method not directly applicable. To improve such method we need to take into account how to describe an image by computer vision : an image is not only a set of intensities but its descriptions/representations in term of sub-objects is needed for the structures extractions and matching. We will describe optical flow methods to follow the structures, and decomposition in sub-areas depending of the solar cycle. After recalling results obtained with geometric loops reconstructions and their consequences for twist measurement and helicity evaluation, we will describe how we can mix pixel and conceptual recontruction for stereovision. We could then include epipolar geometry and Multiscale Vision Model (MVM) to enhance the reconstruction. These concepts are under development for STEREO/SECCHI.

Overview of the limnology of crater lake

USGS Publications Warehouse

Larson, G.L.

1996-01-01

Crater Lake occupies the collapsed caldera of volcanic Mount Mazama in Crater Lake National Park, Oregon. It is the deepest lake (589 m) in the United States and the 7th deepest lake in the world. The water column mixes to a depth of about 200 m in winter and spring from wind energy and cooling. The deep lake is mixed in winter and early spring each year when relatively cold water near the surface sinks and exchanges positions with water in the deep basins of the lake. The lake becomes thermally stratified in summer and early fall. The metalimnion extends to a depth of about 100 m; thus most of the water column is a cold hypolimnion. Secchi disk clarity measurements typically are in the upper-20-m range to the low-30-m range in summer and early fall. Concentrations of nutrients are low, although conductivity is relatively high owing to the inflow of hydrothermal fluids. Total chlorophyll is low in concentration, but typically maximal at a depth of 120 m during periods of thermal stratification. Primary production also is low, with the maximum levels occurring between the depth of 40 and 80 m. Phytoplankton taxa are spatially segregated from each other within the water column to a depth of 200 m in summer and early fall. The same generalization applies to the Zooplankton taxa. Water level, clarity, concentrations of total chlorophyll, primary production, and abundances of zooplankton and introduced kokanee salmon exhibit long-term fluctuations. Based primarily on a recent 10-year study of the lake, the lake is considered to be pristine, except for the consequences of fish introductions. ?? 1996 by the Northwest Scientific Association. All rights reserved.

Overview of the limnology of Crater Lake

USGS Publications Warehouse

Larson, Gary L.

1996-01-01

Crater Lake occupies the collapsed caldera of volcanic Mount Mazama in Crater Lake National Park, Oregon. It is the deepest lake (589 m) in the United States and the 7th deepest lake in the world. The water column mixes to a depth of about 200 m in winter and spring from wind energy and cooling. The deep lake is mixed in winter and early spring each year when relatively cold water near the surface sinks and exchanges positions with water in the deep basins of the lake. The lake becomes thermally stratified in summer and early fall. The metalimnion extends to a depth of about 100 m; thus most of the water column is a cold hypolimnion. Secchi disk clarity measurements typically are in the upper-20-m range to the low-30-m range in summer and early fall. Concentrations of nutrients are low, although conductivity is relatively high owing to the inflow of hydrothermal fluids. Total chlorophyll is low in concentration, but typically maximal at a depth of 120 m during periods of thermal stratification. Primary production also is low, with the maximum levels occurring between the depth of 40 and 80 m. Phytoplankton taxa are spatially segregated from each other within the water column to a depth of 200 m in summer and early fall. The same generalization applies to the zooplankton taxa. Water level, clarity, concentrations of total chlorophyll, primary production, and abundances of zooplankton and introduced kokanee salmon exhibit long-term fluctuations. Based primarily on a recent 10-year study of the lake, the lake is considered to be pristine, except for the consequences of fish introductions.

STEREO SECCHI Observations of Space Debris: Are They Associated with S/WAVES Dust Detections?

NASA Astrophysics Data System (ADS)

St. Cyr, O. C.; Howard, R. A.; Wang, D.; Thompson, W. T.; Harrison, R. A.; Kaiser, M. L.

2007-12-01

White-light coronagraphs are optimized to reject stray light in order to accomplish their primary science objective - - the observation of coronal mass ejections (CMEs) and the corona. Because they were designed to detect these faint signals while pointing at the Sun, many spacebased coronagraphs in the past (Skylab, SMM, SOHO) have detected "debris" apparently associated with the vehicle. These appear to be sunlit particles very near the front of the telescope aperture (~meters). In at least one case, these earlier debris sightings were interpreted as deteriorating insulation from the thermal blankets on the spacecraft (St. Cyr and Warner, 1991ASPC...17..126S); and for the earlier Sklyab observations, the sightings were believed to be associated with water droplets (Eddy, "A New Sun: The Solar Results from Skylab", NASA SP-402, p119, 1979.) The STEREO SECCHI suite of white-light coronagraphs represents the most recent instantations of these specialized instruments, and for the first time we are able to track CMEs from their initiation at the Sun out to 1 A.U. Since observations commenced, the SECCHI white-light telescopes have been sporadically detecting debris particles. Most of the detections are individual or small numbers of bright objects in the field which therefore do not affect the primary science goals of the mission. But on several occasions in the eight months' of observation there have been "swarms" of these bright objects which completely obscure the field of view of one or more instrument for a brief period of time. Here we report on the intriguing possibility that the SECCHI debris sightings represent particles of thermal insulation, ejected from the spacecraft by interplanetary dust impacts. Because of the large field of view and high duty cycle of the Heliospheric Imagers on STEREO, we may be able to demonstrate that some of these have also been detected by STEREO S/WAVES as sporadic plasma emissions.

Water Quality, Hydrology, and Simulated Response to Changes in Phosphorus Loading of Butternut Lake, Price and Ashland Counties, Wisconsin, with Special Emphasis on the Effects of Internal Phosphorus Loading in a Polymictic Lake

USGS Publications Warehouse

Robertson, Dale M.; Rose, William J.

2008-01-01

Butternut Lake is a 393-hectare, eutrophic to hypereutrophic lake in northcentral Wisconsin. After only minor improvements in water quality were observed following several actions taken to reduce the nutrient inputs to the lake, a detailed study was conducted from 2002 to 2007 by the U.S. Geological Survey to better understand how the lake functions. The goals of this study were to describe the water quality and hydrology of the lake, quantify external and internal sources of phosphorus, and determine the effects of past and future changes in phosphorus inputs on the water quality of the lake. Since the early 1970s, the water quality of Butternut Lake has changed little in response to nutrient reductions from the watershed. The largest changes were in near-surface total phosphorus concentrations: August concentrations decreased from about 0.09 milligrams per liter (mg/L) to about 0.05 mg/L, but average summer concentrations decreased only from about 0.055-0.060 mg/L to about 0.045 mg/L. Since the early 1970s, only small changes were observed in chlorophyll a concentrations and water clarity (Secchi depths). All major water and phosphorus sources, including the internal release of phosphorus from the sediments (internal loading), were measured directly, and minor sources were estimated to construct detailed water and phosphorus budgets for the lake during monitoring years (MY) 2003 and 2004. During these years, Butternut Creek, Spiller Creek, direct precipitation, small tributaries and near-lake drainage area, and ground water contributed about 62, 20, 8, 7, and 3 percent of the inflow, respectively. The average annual load of phosphorus to the lake was 2,540 kilograms (kg), of which 1,590 kg came from external sources (63 percent) and 945 kg came from the sediments in the lake (37 percent). Of the total external sources, Butternut Creek, Spiller Creek, small tributaries and near-lake drainage area, septic systems, precipitation, and ground water contributed about 63, 23, 9, 3, 1, and 1 percent, respectively. Because of the high internal phosphorus loading, the eutrophication models used in this study were unable to simulate the observed water-quality characteristics in the lake without incorporating this source of phosphorus. However, when internal loading of phosphorus was added to the BATHTUB model, it accurately simulated the average water-quality characteristics measured in MY 2003 and 2004. Model simulations demonstrated a relatively linear response between in-lake total phosphorus concentrations and external phosphorus loading; however, the changes in concentrations were smaller than the changes in external phosphorus loadings (about 25-40 percent of the change in phosphorus loading). Changes in chlorophyll a concentrations, the percentage of days with algal blooms, and Secchi depths were nonlinear and had a greater response to reductions in phosphorus loading than to increases in phosphorus loading. A 50-percent reduction in external phosphorus loading caused an 18-percent decrease in chlorophyll a concentrations, a 41-percent decrease in the percentage of days with algal blooms, and a 12-percent increase in Secchi depth. When the additional internal phosphorus loading was removed from model simulations, all of these constituents showed a much greater response to changes in external phosphorus loading. Because of Butternut Lake's morphometry, it is polymictic, which means it mixes frequently and does not develop stable thermal stratification throughout the summer. This characteristic makes it more vulnerable than dimictic lakes, which mix in spring and fall and develop stable thermal stratification during summer, to the high internal phosphorus loading that has resulted from historically high, nonnatural, external phosphorus loading. In polymictic lakes, the phosphorus released from the sediments is mixed into the upper part of the lake throughout summer. Once Butternut Lake became hypereutrophic (very p

The transiting dust clumps in the evolved disc of the Sun-like UXor RZ Psc.

PubMed

Kennedy, Grant M; Kenworthy, Matthew A; Pepper, Joshua; Rodriguez, Joseph E; Siverd, Robert J; Stassun, Keivan G; Wyatt, Mark C

2017-01-01

RZ Psc is a young Sun-like star, long associated with the UXor class of variable stars, which is partially or wholly dimmed by dust clumps several times each year. The system has a bright and variable infrared excess, which has been interpreted as evidence that the dimming events are the passage of asteroidal fragments in front of the host star. Here, we present a decade of optical photometry of RZ Psc and take a critical look at the asteroid belt interpretation. We show that the distribution of light curve gradients is non-uniform for deep events, which we interpret as possible evidence for an asteroidal fragment-like clump structure. However, the clumps are very likely seen above a high optical depth midplane, so the disc's bulk clumpiness is not revealed. While circumstantial evidence suggests an asteroid belt is more plausible than a gas-rich transition disc, the evolutionary status remains uncertain. We suggest that the rarity of Sun-like stars showing disc-related variability may arise because (i) any accretion streams are transparent and/or (ii) turbulence above the inner rim is normally shadowed by a flared outer disc.

The transiting dust clumps in the evolved disc of the Sun-like UXor RZ Psc

NASA Astrophysics Data System (ADS)

Kennedy, Grant M.; Kenworthy, Matthew A.; Pepper, Joshua; Rodriguez, Joseph E.; Siverd, Robert J.; Stassun, Keivan G.; Wyatt, Mark C.

2017-01-01

RZ Psc is a young Sun-like star, long associated with the UXor class of variable stars, which is partially or wholly dimmed by dust clumps several times each year. The system has a bright and variable infrared excess, which has been interpreted as evidence that the dimming events are the passage of asteroidal fragments in front of the host star. Here, we present a decade of optical photometry of RZ Psc and take a critical look at the asteroid belt interpretation. We show that the distribution of light curve gradients is non-uniform for deep events, which we interpret as possible evidence for an asteroidal fragment-like clump structure. However, the clumps are very likely seen above a high optical depth midplane, so the disc's bulk clumpiness is not revealed. While circumstantial evidence suggests an asteroid belt is more plausible than a gas-rich transition disc, the evolutionary status remains uncertain. We suggest that the rarity of Sun-like stars showing disc-related variability may arise because (i) any accretion streams are transparent and/or (ii) turbulence above the inner rim is normally shadowed by a flared outer disc.

Monitoring and modeling water temperature and trophic status of a shallow Mediterranean lake

NASA Astrophysics Data System (ADS)

Giadrossich, Filippo; Bueche, Thomas; Pulina, Silvia; Marrosu, Roberto; Padedda, Bachisio Mario; Mariani, Maria Antonietta; Vetter, Mark; Cohen, Denis; Pirastru, Mario; Niedda, Marcello; Lugliè, Antonella

2017-04-01

Lakes are sensitive to changes in climate and human activities. Over the last few decades, Mediterranean lakes have experienced various problems due to the current climate change (drought, flood, warming, salt accumulation, water quality changes, etc.), often amplified by water use, intensification of land use activities, and pollution. The overall impact of these changes on water resources is still an open question. In this study we monitor the trophic status and the dynamics of water temperature of Lake Baratz, the only natural lake in Sardinia, Italy, characterized by high salinity and shallow depth. We extend the research carried out in the past 8 years by integrating new physical, chemical and biological data using a multidisciplinary approach that combines hydrological and biological dynamics. In particular, the lake water balance and the thermal and hydrochemical regime are studied with a lake dynamic model (the General Lake Model or GLM) which combine the energy budget method for estimating lake evaporation, and a physically-based rainfall-runoff simulator for estimating lake inflow, calibrated with measurements at the cross section of the main inlet stream. The trophic state of the lake was evaluated applying the OCDE Probability Distribution Diagrams method, which requires nutrient concentrations in the lake (total phosphorus), phytoplankton chlorophyll a and Secchi disk transparency data. We collected field data from a raft station and a land station, measuring net solar radiation, air temperature and relative humidity, precipitation, wind velocity, atmospheric pressure, and temperature from thermistors submerged in the uppermost three centimeters of water and beneath the lake surface at depths of 1, 2, 3, 4, 5, 6, and 8 m. Samples for nutrients and chlorophyll a analyses were collected at the same above mentioned depths close to the raft station using a Niskin bottle. Temperature, salinity, pH, and dissolved oxygen were measured using a multi-parametric probe. Water temperature is modelled with a unidimensional model. The validation of the model is verified by comparing recorded with simulated data. The results show a good fit of the modelled water temperature, with a mean error of 0.11 °C and a root mean square error of 1.31 °C. The largest of the mean error values is recorded in the bottom layers (0.71 °C), while in central (thermocline) and surface layers the average error is negligible. Total phosphorus values confirmed the eutrophic state of the lake (>35 mg P m-3). On the contrary, chlorophyll a and Secchi disk data indicated a more probable mesotrophic state. This frame highlights the necessity of further investigations on the responses of the lake's biological community to the different hydrological regimes in the different years.

The use of roving discs and orthogonal natural frequencies for crack identification and location in rotors

NASA Astrophysics Data System (ADS)

Haji, Zyad N.; Olutunde Oyadiji, S.

2014-11-01

A variety of approaches that have been developed for the identification and localisation of cracks in a rotor system, which exploit natural frequencies, require a finite element model to obtain the natural frequencies of the intact rotor as baseline data. In fact, such approaches can give erroneous results about the location and depth of a crack if an inaccurate finite element model is used to represent an uncracked model. A new approach for the identification and localisation of cracks in rotor systems, which does not require the use of the natural frequencies of an intact rotor as a baseline data, is presented in this paper. The approach, named orthogonal natural frequencies (ONFs), is based only on the natural frequencies of the non-rotating cracked rotor in the two lateral bending vibration x-z and y-z planes. The approach uses the cracked natural frequencies in the horizontal x-z plane as the reference data instead of the intact natural frequencies. Also, a roving disc is traversed along the rotor in order to enhance the dynamics of the rotor at the cracked locations. At each spatial location of the roving disc, the two ONFs of the rotor-disc system are determined from which the corresponding ONF ratio is computed. The ONF ratios are normalised by the maximum ONF ratio to obtain normalised orthogonal natural frequency curves (NONFCs). The non-rotating cracked rotor is simulated by the finite element method using the Bernoulli-Euler beam theory. The unique characteristics of the proposed approach are the sharp, notched peaks at the crack locations but rounded peaks at non-cracked locations. These features facilitate the unambiguous identification and locations of cracks in rotors. The effects of crack depth, crack location, and mass of a roving disc are investigated. The results show that the proposed method has a great potential in the identification and localisation of cracks in a non-rotating cracked rotor.

ALMA observations of the multiplanet system 61 Vir: what lies outside super-Earth systems?

NASA Astrophysics Data System (ADS)

Marino, S.; Wyatt, M. C.; Kennedy, G. M.; Holland, W.; Matrà, L.; Shannon, A.; Ivison, R. J.

2017-08-01

A decade of surveys has hinted at a possible higher occurrence rate of debris discs in systems hosting low-mass planets. This could be due to common favourable forming conditions for rocky planets close in and planetesimals at large radii. In this paper, we present the first resolved millimetre study of the debris disc in the 4.6 Gyr old multiplanet system 61 Vir, combining Atacama Large Millimeter/submillimeter Array and James Clerk Maxwell Telescope data at 0.86 mm. We fit the data using a parametric disc model, finding that the disc of planetesimals extends from 30 au to at least 150 au, with a surface density distribution of millimetre-sized grains with a power-law slope of 0.1^{+1.1}_{-0.8}. We also present a numerical collisional model that can predict the evolution of the surface density of millimetre grains for a given primordial disc, finding that it does not necessarily have the same radial profile as the total mass surface density (as previous studies suggested for the optical depth), with the former being flatter. Finally, we find that if the planetesimal disc was stirred at 150 au by an additional unseen planet, that planet should be more massive than 10 M⊕ and lie between 10 and 20 au. Lower planet masses and semimajor axes down to 4 au are possible for eccentricities ≫0.1.

Generalized scaling of seasonal thermal stratification in lakes

NASA Astrophysics Data System (ADS)

Shatwell, T.; Kirillin, G.

2016-12-01

The mixing regime is fundamental to the biogeochemisty and ecology of lakes because it determines the vertical transport of matter such as gases, nutrients, and organic material. Whereas shallow lakes are usually polymictic and regularly mix to the bottom, deep lakes tend to stratify seasonally, separating surface water from deep sediments and deep water from the atmosphere. Although empirical relationships exist to predict the mixing regime, a physically based, quantitative criterion is lacking. Here we review our recent research on thermal stratification in lakes at the transition between polymictic and stratified regimes. Using the mechanistic balance between potential and kinetic energy in terms of the Richardson number, we derive a generalized physical scaling for seasonal stratification in a closed lake basin. The scaling parameter is the critical mean basin depth that delineates polymictic and seasonally stratified lakes based on lake water transparency (Secchi depth), lake length, and an annual mean estimate for the Monin-Obukhov length. We validated the scaling on available data of 374 global lakes using logistic regression and found it to perform better than other criteria including a conventional open basin scaling or a simple depth threshold. The scaling has potential applications in estimating large scale greenhouse gas fluxes from lakes because the required inputs, like water transparency and basin morphology, can be acquired using the latest remote sensing technologies. The generalized scaling is universal for freshwater lakes and allows the seasonal mixing regime to be estimated without numerically solving the heat transport equations.

Lake Ontario water quality during the 2003 and 2008 intensive field years and comparison with long-term trends

USGS Publications Warehouse

Holeck, K. T.; Rudstam, L. G.; Watkins, J. M.; Luckey, F. J.; Lantry, J. R.; Lantry, Brian F.; Trometer, E. S.; Koops, M. A.; Johnson, Terry B.

2015-01-01

Phosphorus loading declined between the 1970s and the 1990s, leading to oligotrophication of the offshore waters of Lake Ontario during that time period. Using lake-wide data from the intensive field years of 2003 and 2008 and from available long-term data sets on several trophic state indicators (total phosphorus [TP], soluble reactive silica [SRSi], chlorophyll a and Secchi disc transparency [SDT]), we tested the hypothesis that oligotrophication of the offshore waters of Lake Ontario has continued in the 2000s. Significant differences between 2003 and 2008 include higher spring (April) TP, SRSi, and SDT in 2008, lower summer (July–August) SDT in 2008, higher summer chlorophyll a in 2008, and lower fall (September) TP, SRSi, and chlorophyll a in 2008. The decline in SRSi from spring to summer was greater in 2008 than in 2003. Change point and regression analyses on the long-term data revealed no trend in spring TP since 1996, in summer chlorophyll a since 1994, in spring SDT since 1998, in spring SRSi or SRSi decline from spring to summer since 1999, or in summer SDT since 2001. Neither the comparison of the 2003 and 2008 surveys nor the analysis of the long-term data supported our hypothesis of continued oligotrophication of the offshore of Lake Ontario in the 2000s.

Deducing material quality in cast and hot-forged steels by new bending test

NASA Astrophysics Data System (ADS)

Valberg, Henry; Langøy, Morten; Nedreberg, Mette; Helvig, Torgeir

2017-10-01

A special bend test has been developed and applied for the purpose of characterization and comparison of the material ductility in crankpin steel discs manufactured by casting, or casting subsequently followed by hot open-die forging (ODF) or closed-die forging (CDF). The bending test specimen consists of a small rectangular plate of material with a round hole cut out in the middle. The "eye-shape" specimens were cut out from various positions either near to the surface of, or from the interior of the discs. The test method revealed differences in ductility for the investigated materials, and for different depth positions inside the discs. The roughening of the specimen surface on the top-side of the specimen bend also varied dependent on the processing method for the material. Current results show that this test method is useful for evaluation of material quality in differently processed material. Experimental bend test results are presented for differently processed variants of the same material, i.e., crankpin discs either made by solely casting or casting subsequently followed by hot working either by ODF or CDF.

Role of chondroitin sulphate tethered silk scaffold in cartilaginous disc tissue regeneration.

PubMed

Bhattacharjee, Maumita; Chawla, Shikha; Chameettachal, Shibu; Murab, Sumit; Bhavesh, Neel Sarovar; Ghosh, Sourabh

2016-04-12

Strategies for tissue engineering focus on scaffolds with tunable structure and morphology as well as optimum surface chemistry to simulate the anatomy and functionality of the target tissue. Silk fibroin has demonstrated its potential in supporting cartilaginous tissue formation both in vitro and in vivo. In this study, we investigate the role of controlled lamellar organization and chemical composition of biofunctionalized silk scaffolds in replicating the structural properties of the annulus region of an intervertebral disc using articular chondrocytes. Covalent attachment of chondroitin sulfate (CS) to silk is characterized. CS-conjugated silk constructs demonstrate enhanced cellular metabolic activity and chondrogenic redifferentiation potential with significantly improved mechanical properties over silk-only constructs. A matrix-assisted laser desorption ionization-time of flight analysis and protein-protein interaction studies help to generate insights into how CS conjugation can facilitate the production of disc associated matrix proteins, compared to a silk-only based construct. An in-depth understanding of the interplay between such extra cellular matrix associated proteins should help in designing more rational scaffolds for cartilaginous disc regeneration needs.

Multiple extreme environmental conditions of intermittent soda pans in the Carpathian Basin (Central Europe).

PubMed

Boros, Emil; Katalin, V-Balogh; Vörös, Lajos; Horváth, Zsófia

2017-01-01

Soda lakes and pans represent saline ecosystems with unique chemical composition, occurring on all continents. The purpose of this study was to identify and characterise the main environmental gradients and trophic state that prevail in the soda pans (n=84) of the Carpathian Basin in Central Europe. Underwater light conditions, dissolved organic matter, phosphorus and chlorophyll a were investigated in 84 pans during 2009-2010. Besides, water temperature was measured hourly with an automatic sensor throughout one year in a selected pan. The pans were very shallow (median depth: 15 cm), and their extremely high turbidity (Secchi depth median: 3 cm, min: 0.5 cm) was caused by high concentrations of inorganic suspended solids (median: 0.4 g L -1 , max: 16 g L -1 ), which was the dominant (>50%) contributing factor to the vertical attenuation coefficient in 67 pans (80%). All pans were polyhumic (median DOC: 47 mg L -1 ), and total phosphorus concentration was also extremely high (median: 2 mg L -1 , max: 32 mg L -1 ). The daily water temperature maximum (44 °C) and fluctuation maximum (28 °C) were extremely high during summertime. The combination of environmental boundaries: shallowness, daily water temperature fluctuation, intermittent hydroperiod, high turbidity, polyhumic organic carbon concentration, high alkalinity and hypertrophy represent a unique extreme aquatic ecosystem.

Bait type influences on catch and bycatch in tandem hoop nets set in reservoirs

USGS Publications Warehouse

Long, James M.; Stewart, David R.; Shiflet, Jeremy; Balsman, Dane; Shoup, Daniel E.

2017-01-01

Tandem hoop nets have become the primary gear for sampling channel catfish Ictalurus punctatus, but suffer from high incidences of bycatch, particularly aquatic turtles that usually drown as a result. We sought to determine if bait type, ZOTE© soap and ground cheese logs, would influence catch of channel catfish (CPUE and mean TL) and bycatch of fishes and aquatic turtles. We sampled with tandem hoop nets in 13 Kentucky reservoirs (5–73 ha) using a crossover design and two sampling events. We found no difference in channel catfish catch rates between bait types, but mean sizes of fish caught using ZOTE© soap were approximately 24 mm longer compared to cheese. Fish bycatch was similar between bait types, but tandem hoop nets baited with ZOTE© soap caught up to 61% fewer turtles and mortality of turtles that were captured was up to 12% lower than those baited with cheese. Depth of net set, water temperature, and Secchi depth were environmental factors measured that affected catch and bycatch, but varied among species. Using ZOTE© soap as bait in tandem hoop nets appears to be a fairly simple and straightforward method for maintaining high catch rates of channel catfish while minimizing turtle mortality.

Sink fast and swim harder! Round-trip cost-of-transport for buoyant divers.

PubMed

Miller, Patrick J O; Biuw, Martin; Watanabe, Yuuki Y; Thompson, Dave; Fedak, Mike A

2012-10-15

Efficient locomotion between prey resources at depth and oxygen at the surface is crucial for breath-hold divers to maximize time spent in the foraging layer, and thereby net energy intake rates. The body density of divers, which changes with body condition, determines the apparent weight (buoyancy) of divers, which may affect round-trip cost-of-transport (COT) between the surface and depth. We evaluated alternative predictions from external-work and actuator-disc theory of how non-neutral buoyancy affects round-trip COT to depth, and the minimum COT speed for steady-state vertical transit. Not surprisingly, the models predict that one-way COT decreases (increases) when buoyancy aids (hinders) one-way transit. At extreme deviations from neutral buoyancy, gliding at terminal velocity is the minimum COT strategy in the direction aided by buoyancy. In the transit direction hindered by buoyancy, the external-work model predicted that minimum COT speeds would not change at greater deviations from neutral buoyancy, but minimum COT speeds were predicted to increase under the actuator disc model. As previously documented for grey seals, we found that vertical transit rates of 36 elephant seals increased in both directions as body density deviated from neutral buoyancy, indicating that actuator disc theory may more closely predict the power requirements of divers affected by gravity than an external work model. For both models, minor deviations from neutral buoyancy did not affect minimum COT speed or round-trip COT itself. However, at body-density extremes, both models predict that savings in the aided direction do not fully offset the increased COT imposed by the greater thrusting required in the hindered direction.

Automated determination of cup-to-disc ratio for classification of glaucomatous and normal eyes on stereo retinal fundus images

NASA Astrophysics Data System (ADS)

Muramatsu, Chisako; Nakagawa, Toshiaki; Sawada, Akira; Hatanaka, Yuji; Yamamoto, Tetsuya; Fujita, Hiroshi

2011-09-01

Early diagnosis of glaucoma, which is the second leading cause of blindness in the world, can halt or slow the progression of the disease. We propose an automated method for analyzing the optic disc and measuring the cup-to-disc ratio (CDR) on stereo retinal fundus images to improve ophthalmologists' diagnostic efficiency and potentially reduce the variation on the CDR measurement. The method was developed using 80 retinal fundus image pairs, including 25 glaucomatous, and 55 nonglaucomatous eyes, obtained at our institution. A disc region was segmented using the active contour method with the brightness and edge information. The segmentation of a cup region was performed using a depth map of the optic disc, which was reconstructed on the basis of the stereo disparity. The CDRs were measured and compared with those determined using the manual segmentation results by an expert ophthalmologist. The method was applied to a new database which consisted of 98 stereo image pairs including 60 and 30 pairs with and without signs of glaucoma, respectively. Using the CDRs, an area under the receiver operating characteristic curve of 0.90 was obtained for classification of the glaucomatous and nonglaucomatous eyes. The result indicates potential usefulness of the automated determination of CDRs for the diagnosis of glaucoma.

The collagen structure of bovine intervertebral disc studied using polarization-sensitive optical coherence tomography

NASA Astrophysics Data System (ADS)

Matcher, Stephen J.; Winlove, C. Peter; Gangnus, Sergei V.

2004-04-01

Polarization-sensitive optical coherence tomography (PS-OCT) is used to measure the birefringence properties of bovine intervertebral disc and equine flexor tendon. For equine tendon the birefringence Dgrn is (6.0 ± 0.2) × 10-3 at a wavelength of 1.3 µm. This is somewhat larger than the values reported for bovine tendon. The surface region of the annulus fibrosus of a freshly excised intact bovine intervertebral disc displays an identical value of birefringence, Dgrn = (6.0 ± 0.6) × 10-3 at 1.3 µm. The nucleus pulposus does not display birefringence, the measured apparent value of Dgrn = (0.39 ± 0.01) × 10-3 being indistinguishable from the effects of depolarization due to multiple scattering. A clear difference is found between the depth-resolved retardance of equine tendon and that of bovine intervertebral disc. This apparently relates to the lamellar structure of the latter tissue, in which the collagen fibre orientation alternates between successive lamellae. A semi-empirical model based on Jones calculus shows that the measurements are in reasonable agreement with previous optical and x-ray data. These results imply that PS-OCT could be a useful tool to study collagen organization within the intervertebral disc in vitro and possibly in vivo and its variation with applied load and disease.

Long-term citizen-collected data reveal geographical patterns and temporal trends in lake water clarity

USGS Publications Warehouse

Lottig, Noah R.; Wagner, Tyler; Henry, Emily N.; Cheruvelil, Kendra Spence; Webster, Katherine E.; Downing, John A.; Stow, Craig A.

2014-01-01

We compiled a lake-water clarity database using publically available, citizen volunteer observations made between 1938 and 2012 across eight states in the Upper Midwest, USA. Our objectives were to determine (1) whether temporal trends in lake-water clarity existed across this large geographic area and (2) whether trends were related to the lake-specific characteristics of latitude, lake size, or time period the lake was monitored. Our database consisted of >140,000 individual Secchi observations from 3,251 lakes that we summarized per lake-year, resulting in 21,020 summer averages. Using Bayesian hierarchical modeling, we found approximately a 1% per year increase in water clarity (quantified as Secchi depth) for the entire population of lakes. On an individual lake basis, 7% of lakes showed increased water clarity and 4% showed decreased clarity. Trend direction and strength were related to latitude and median sample date. Lakes in the southern part of our study-region had lower average annual summer water clarity, more negative long-term trends, and greater inter-annual variability in water clarity compared to northern lakes. Increasing trends were strongest for lakes with median sample dates earlier in the period of record (1938–2012). Our ability to identify specific mechanisms for these trends is currently hampered by the lack of a large, multi-thematic database of variables that drive water clarity (e.g., climate, land use/cover). Our results demonstrate, however, that citizen science can provide the critical monitoring data needed to address environmental questions at large spatial and long temporal scales. Collaborations among citizens, research scientists, and government agencies may be important for developing the data sources and analytical tools necessary to move toward an understanding of the factors influencing macro-scale patterns such as those shown here for lake water clarity.

Long-Term Citizen-Collected Data Reveal Geographical Patterns and Temporal Trends in Lake Water Clarity

PubMed Central

Lottig, Noah R.; Wagner, Tyler; Norton Henry, Emily; Spence Cheruvelil, Kendra; Webster, Katherine E.; Downing, John A.; Stow, Craig A.

2014-01-01

We compiled a lake-water clarity database using publically available, citizen volunteer observations made between 1938 and 2012 across eight states in the Upper Midwest, USA. Our objectives were to determine (1) whether temporal trends in lake-water clarity existed across this large geographic area and (2) whether trends were related to the lake-specific characteristics of latitude, lake size, or time period the lake was monitored. Our database consisted of >140,000 individual Secchi observations from 3,251 lakes that we summarized per lake-year, resulting in 21,020 summer averages. Using Bayesian hierarchical modeling, we found approximately a 1% per year increase in water clarity (quantified as Secchi depth) for the entire population of lakes. On an individual lake basis, 7% of lakes showed increased water clarity and 4% showed decreased clarity. Trend direction and strength were related to latitude and median sample date. Lakes in the southern part of our study-region had lower average annual summer water clarity, more negative long-term trends, and greater inter-annual variability in water clarity compared to northern lakes. Increasing trends were strongest for lakes with median sample dates earlier in the period of record (1938–2012). Our ability to identify specific mechanisms for these trends is currently hampered by the lack of a large, multi-thematic database of variables that drive water clarity (e.g., climate, land use/cover). Our results demonstrate, however, that citizen science can provide the critical monitoring data needed to address environmental questions at large spatial and long temporal scales. Collaborations among citizens, research scientists, and government agencies may be important for developing the data sources and analytical tools necessary to move toward an understanding of the factors influencing macro-scale patterns such as those shown here for lake water clarity. PMID:24788722

A meta-analysis of water quality and aquatic macrophyte responses in 18 lakes treated with lanthanum modified bentonite (Phoslock(®)).

PubMed

Spears, Bryan M; Mackay, Eleanor B; Yasseri, Said; Gunn, Iain D M; Waters, Kate E; Andrews, Christopher; Cole, Stephanie; De Ville, Mitzi; Kelly, Andrea; Meis, Sebastian; Moore, Alanna L; Nürnberg, Gertrud K; van Oosterhout, Frank; Pitt, Jo-Anne; Madgwick, Genevieve; Woods, Helen J; Lürling, Miquel

2016-06-15

Lanthanum (La) modified bentonite is being increasingly used as a geo-engineering tool for the control of phosphorus (P) release from lake bed sediments to overlying waters. However, little is known about its effectiveness in controlling P across a wide range of lake conditions or of its potential to promote rapid ecological recovery. We combined data from 18 treated lakes to examine the lake population responses in the 24 months following La-bentonite application (range of La-bentonite loads: 1.4-6.7 tonnes ha(-1)) in concentrations of surface water total phosphorus (TP; data available from 15 lakes), soluble reactive phosphorus (SRP; 14 lakes), and chlorophyll a (15 lakes), and in Secchi disk depths (15 lakes), aquatic macrophyte species numbers (6 lakes) and aquatic macrophyte maximum colonisation depths (4 lakes) across the treated lakes. Data availability varied across the lakes and variables, and in general monitoring was more frequent closer to the application dates. Median annual TP concentrations decreased significantly across the lakes, following the La-bentonite applications (from 0.08 mg L(-1) in the 24 months pre-application to 0.03 mg L(-1) in the 24 months post-application), particularly in autumn (0.08 mg L(-1) to 0.03 mg L(-1)) and winter (0.08 mg L(-1) to 0.02 mg L(-1)). Significant decreases in SRP concentrations over annual (0.019 mg L(-1) to 0.005 mg L(-1)), summer (0.018 mg L(-1) to 0.004 mg L(-1)), autumn (0.019 mg L(-1) to 0.005 mg L(-1)) and winter (0.033 mg L(-1) to 0.005 mg L(-1)) periods were also reported. P concentrations following La-bentonite application varied across the lakes and were correlated positively with dissolved organic carbon concentrations. Relatively weak, but significant responses were reported for summer chlorophyll a concentrations and Secchi disk depths following La-bentonite applications, the 75th percentile values decreasing from 119 μg L(-1) to 74 μg L(-1) and increasing from 398 cm to 506 cm, respectively. Aquatic macrophyte species numbers and maximum colonisation depths increased following La-bentonite application from a median of 5.5 species to 7.0 species and a median of 1.8 m to 2.5 m, respectively. The aquatic macrophyte responses varied significantly between lakes. La-bentonite application resulted in a general improvement in water quality leading to an improvement in the aquatic macrophyte community within 24 months. However, because, the responses were highly site-specific, we stress the need for comprehensive pre- and post-application assessments of processes driving ecological structure and function in candidate lakes to inform future use of this and similar products. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Water-quality and lake-stage data for Wisconsin lakes, water year 1996

USGS Publications Warehouse

,

1997-01-01

The purpose of this report is to provide information about the physical and chemical characteristics of Wisconsin lakes. Data that have been collected at specific lakes, and information to aid in the interpretation of those data, are included in this report. Data collected includes measurements of lake stage and in-lake water quality. Graphs of Secchi depths, surface totalphosphorus and chlorophyll-a concentrations versus time are included for lakes with two or more years of data. Graphs of vertical profiles of temperature, dissolved oxygen, pH, and specific conductance are included for sites where these parameters were measured. Descriptive information for each lake includes: location of the lake, drainage area of the lake's watershed, period for which data are available, revisions to previously published records, and pertinent remarks. Additional data, such as streamflow and water quality in tributary and outlet streams of some of the lakes, are published in another volume: "Water Resources Data-Wisconsin, 1996."

Analysis of the spatio-temporal variability of seawater quality in the southeastern Arabian Gulf.

PubMed

Mezhoud, Nahla; Temimi, Marouane; Zhao, Jun; Al Shehhi, Maryam Rashed; Ghedira, Hosni

2016-05-15

In this study, seawater quality measurements, including salinity, sea surface temperature (SST), chlorophyll-a (Chl-a), Secchi disk depth (SDD), pH, and dissolved oxygen (DO), were made from June 2013 to November 2014 at 52 stations in the southeastern Arabian Gulf. Significant variability was noticed for all collected parameters. Salinity showed a decreasing trend, and Chl-a, DO, pH, and SDD demonstrated increasing trends from shallow onshore stations to deep offshore ones, which could be attributed to variations of ocean circulation and meteorological conditions from onshore to offshore waters, and the likely effects of desalination plants along the coast. Salinity and temperature were high in summer and low in winter while Chl-a, SDD, pH, and DO indicated an opposite trend. The CTD profiles showed vertically well-mixed structures. Qualitative analysis of phytoplankton showed a high diversity of species without anomalous species found except in Ras Al Khaimah stations where diatoms were the dominating ones. Copyright © 2016 Elsevier Ltd. All rights reserved.

Water-quality and lake-stage data for Wisconsin lakes, water year 2005

USGS Publications Warehouse

Rose, W.J.; Garn, H.S.; Goddard, G.L.; Marsh, S.B.; Olson, D.L.; Robertson, Dale M.

2006-01-01

The U.S. Geological Survey (USGS), in cooperation with local and other agencies, collects data at selected lakes throughout Wisconsin. These data, accumulated over many years, provide a data base for developing an improved understanding of the water quality of lakes. The purpose of this report is to provide information about the chemical and physical charac-teristics of Wisconsin lakes. Data that have been collected at specific lakes, and information to aid in the interpretation of those data, are included in this report. Data collected include measure-ments of in-lake water quality and lake stage. Time series graphs of Secchi depths, surface total phosphorus and chlorophyll a concentrations collected during non-frozen periods are included for all lakes. Graphs of vertical profiles of temperature, dissolved oxygen, pH, and specific conductance are included for sites where these parameters were measured. Descriptive infor-mation for each lake includes: location of the lake, area of the lake's watershed, period for which data are available, revisions to previously published records, and pertinent remarks.

Water quality, hydrology, and the effects of changes in phosphorus loading to Pike Lake, Washington County, Wisconsin, with special emphasis on inlet-to-outlet short-circuiting

USGS Publications Warehouse

Rose, William J.; Robertson, Dale M.; Mergener, Elizabeth A.

2004-01-01

Simulations using water-quality models within the Wisconsin Lake Model Suite (WiLMS) indicated Pike Lake's response to 13 different phosphorus-loading scenarios. These scenarios included a base 'normal' year (2000) for which lake water quality and loading were known, six different percentage increases or decreases in phosphorus loading from controllable sources, and six different loading scenarios corresponding to specific management actions. Model simulations indicate that a 50-percent reduction in controllable loading sources would be needed to achieve a mesotrophic classification with respect to phosphorus, chlorophyll a, and Secchi depth (an index of water clarity). Model simulations indicated that short-circuiting of phosphorus from the inlet to the outlet was the main reason the water quality of the lake is good relative to the amount of loading from the Rubicon River and that changes in the percentage of inlet-to-outlet short-circuiting have a significant influence on the water quality of the lake.

Application of ecological, geological and oceanographic ERTS-1 imagery to Delaware's coastal resources management

NASA Technical Reports Server (NTRS)

Klemas, V. (Principal Investigator); Bartlett, D. S.; Philpot, W. D.; Davis, G. R.; Rogers, R. H.; Reed, L.

1974-01-01

The author has identified the following significant results. Data from twelve successful ERTS-1 passes over Delaware Bay have been analyzed with special emphasis on coastal vegetation, land use, current circulation, water turbidity and pollution dispersion. Secchi depth, suspended sediment concentration and transmissivity as measured from helicopters and boats were correlated with ERTS-1 image radiance. Multispectral signatures of acid disposal plumes, sediment plumes and slick were investigated. Ten vegetative cover and water discrimination classes were selected for mapping: (1) forest-land; (2) Phragmites communis; (3) Spartina patens and Distichlis spicata; (4) Spartina alterniflora; (5) cropland; (6) plowed cropland; (7) sand and bare sandy soil; (8) bare mud; (9) deep water; and (10) sediment-laden and shallow water. Canonical analysis predicted good classification accuracies for most categories. The actual classification accuracies were very close to the predicted values with 8 of 10 categories classified with greater than 90% accuracy indicating that representative training sets had been selected.

Light from the Waves

NASA Technical Reports Server (NTRS)

2002-01-01

For many years limnologists have been looking for an alternative to the Secchi disk. In the mid to late 1970s, Lillesand (then at Minnesota) along with colleagues in Wisconsin began to toy with the idea of using remote sensing satellites to observe lake quality from space. They reasoned that if water quality information could be extracted from images taken by orbiting satellites, the number of lakes monitored could be greatly expanded. For several years, the scientists experimented with data from early Landsat missions, but the data provided only very rough estimates of water quality. 'We were able to get accurate measurements of water clarity only after Landsat Thematic Mapper (TM) data became available,' says Lillesand. Since 1972 the Landsat program has launched a series of Earth observation satellites into orbit, collecting image data of our planet's surface. The sensors on the first three satellites in the series, launched in the 1970s, had a coarse spatial resolution (80 meters), and only four spectral bands. Later versions of Landsat have carried improved sensors-the Thematic Mapper instrument on Landsats 4 and 5, and the Enhanced Thematic Mapper Plus on the most recent of the series, Landsat 7, launched in 1999. The Thematic Mapper and the Enhanced Thematic Mapper instruments acquire images in seven different wavelengths of radiation reflected or emitted from the surface of the Earth. The wavelengths are in the visible, reflective infrared and thermal infrared parts of the spectrum. With a spatial resolution of 30 meters, the images are well suited for mapping and monitoring large features such as lakes. 'It was the higher resolution and the addition of the blue band on the Thematic Mapper that gave us clearer results,' says Lillesand. The researchers found that when the amount of blue light reflecting off of the lake was high and the red light was low, the lake generally had high water quality. 'It's common sense. When you look at a clear lake from a distance it appears blue,' says Lillesand. Lakes loaded with algae and sediments, on the other hand, reflect less blue light and more red light. He further explains that the scientists first acquired Landsat Thematic Mapper data of the lakes with known Secchi depths. They then analyzed the satellite data to see if they could arrive at an image that displayed lake clarity as accurately as the Secchi disk measurements. In the end, Lillesand and his colleagues were able to retrieve water clarity maps and measurements from the satellite imagery that were as accurate as Secchi disk measurements. For roughly ten years, this knowledge was put to little use. Then, in the late 1990s, researchers at the University of Minnesota launched a pilot project to measure the water quality of the lakes around the Minneapolis/St. Paul metropolitan area. With a single Landsat TM image, they obtained coverage of all the lakes in the seven-county region. They put the images of the lakes through an analysis similar to that developed a decade earlier and classified lake water quality measurements for over 500 lakes. They tested the Landsat water quality readings against Secchi measurements of sample lakes, and the two sets of data matched up very closely. 'With the Landsat images we ended up getting water quality measurements of 10 times as many lakes as we would have with the Secchi disk data,' says Brezonik. The Minnesota team then dusted off archived Landsat images dating back to the early 1970s and ran them through the same procedure. They found that most of the lakes around the seven-county metro area have not changed in quality over the past 25 years, with somewhat more (7 percent) increasing than decreasing (3 percent) in quality. The results proved so successful that a team of scientists led by Brezonik and Marvin Bauer, director of the University of Minnesota Remote Sensing and Geospatial Analysis Laboratory, expanded the survey to the entire state. The statewide project was funded in part by NASA's Upper Midwest Regional Earth Science Applications Center (RESAC), which was established to monitor and analyze the natural resources in the Upper Great Lakes region. For the statewide water quality map, the researchers assembled the best of two year's worth of cloud-free Landsat images taken of Minnesota. 'We were able to get water clarity readings on 100 percent of the lakes larger than 20 acres using the satellite data,' Brezonik says. Of the 12,700 bodies of water classified as lakes in Minnesota, roughly 10,000 are larger than 20 acres. Once again, the readings matched up with the Secchi disk records. 'When we put the map together, we did see a very strong north-south pattern in Minnesota,' says Brezonik. In the northeast Minnesota the lakes are very clear and the water quality is high. Moving south and southwest, the water clarity and quality diminishes. He believes there are two major reasons for this pattern. The first is that most of the farms and the people in Minnesota are in the southern half of the state. Nutrient-rich run-off from farms and urban developments has caused algae to grow. In the northeast, dense forests where fewer people live surround the lakes. He says the second reason is that the lakes in the south are generally shallower than those in the north. Deeper lakes generally absorb excess sediment and nutrients better. Though the team has not yet finished analyzing archived data from the past, Brezonik believes that the lakes have probably maintained the same level of quality over the past 15 years.

Transient events in bright debris discs: Collisional avalanches revisited

NASA Astrophysics Data System (ADS)

Thebault, P.; Kral, Q.

2018-01-01

Context. A collisional avalanche is set off by the breakup of a large planetesimal, releasing vast amounts of small unbound grains that enter a debris disc located further away from the star, triggering there a collisional chain reaction that could potentially create detectable transient structures. Aims: We investigate this mechanism, using for the first time a fully self-consistent code coupling dynamical and collisional evolutions. We also quantify for the first time the photometric evolution of the system and investigate whether or not avalanches could explain the short-term luminosity variations recently observed in some extremely bright debris discs. Methods: We use the state-of-the-art LIDT-DD code. We consider an avalanche-favoring A6V star, and two set-ups: a "cold disc" case, with a dust release at 10 au and an outer disc extending from 50 to 120 au, and a "warm disc" case with the release at 1 au and a 5-12 au outer disc. We explore, in addition, two key parameters: the density (parameterized by its optical depth τ) of the main outer disc and the amount of dust released by the initial breakup. Results: We find that avalanches could leave detectable structures on resolved images, for both "cold" and "warm" disc cases, in discs with τ of a few 10-3, provided that large dust masses (≳1020-5 × 1022 g) are initially released. The integrated photometric excess due to an avalanche is relatively limited, less than 10% for these released dust masses, peaking in the λ 10-20 μm domain and becoming insignificant beyond 40-50 μm. Contrary to earlier studies, we do not obtain stronger avalanches when increasing τ to higher values. Likewise, we do not observe a significant luminosity deficit, as compared to the pre-avalanche level, after the passage of the avalanche. These two results concur to make avalanches an unlikely explanation for the sharp luminosity drops observed in some extremely bright debris discs. The ideal configuration for observing an avalanche would be a two-belt structure, with an inner belt (at 1 or 10 au for the "warm" and "cold" disc cases, respectively) of fractional luminosity f ≳ 10-4 where breakups of massive planetesimals occur, and a more massive outer belt, with τ of a few 10-3, into which the avalanche chain reaction develops and propagates.

[Maculopathy in case of the pit of the disc].

PubMed

Kolár, P

2005-09-01

The pit of the disc is a congenital anomaly of the optic nerve disc. The prevalence is 1/11 000 patients. On the affected side, the optic disc is in 85% of cases larger than the disc of the other healthy eye. The pit of the disc is very often associated with the presence of the cilioretinal artery. Maculopathy in congenital pit of the optic nerve disc was described in the early 30's of the last century by Calhoun. The average age of the patients is roughly 30 years of age (20-40 years). The complementary examination method, which may help to clarify anatomical conditions of the macular region, is the optical coherence tomography. The defect of the optic disc of different depth caused by the pit and maculopathy caused by retinoschisis communicating with the temporal rim of the disc are found. This case report refers to a 29 years old man with disturbing relative central scotoma and decreased vision for one month in his right eye, who underwent classical three-ports pars plana vitrectomy with expansive gas tamponade. On the basis of differential diagnosis discretion, the temporally localized pit of the disc accompanied by maculopathy due to retonoschisis was detemined. The surgical treatment by means of three-ports pars plana vitrectomy and peeling of the inner limiting membrane with expansive gas tamponade restored in our patient the physiological macular structure followed by improvement of the best-corrected visual acuity. No complications were noticed during the surgery or after it as well. Among the differential diagnoses, it is necessary to eliminate other possible causes of maculopathy in young patients as well as other congenital anomalies of the optic disc, which may be related to the maculopathy. Maculopathy following the pit of the optic nerve disc represents relatively rare diagnostic entity. According to the literature, the natural course of this disease results in very low final best-corrected visual acuity, often worse than 5/50 (0,1 or 20/200). The therapeutic possibility for patients with this disease is operative approach by means of pars plana vitrectomy with peeling of the inner limiting membrane and accompanied by expansive gas tamponade as already mentioned in our case report.

The Partition Intervalometer: A Programmable Underwater Timer for Marking Accumulated Sediment Profiles Collected in Anderson Sediment Traps: Development, Operation, Testing Procedures, and Field Results

USGS Publications Warehouse

Rendigs, Richard R.; Anderson, Roger Y.; Xu, Jingping; Davis, Raymond E.; Bergeron, Emile M.

2009-01-01

This manual illustrates the development of a programmable instrument designed to deploy a series of wafer-shaped discs (partitions) into the collection tube of a sediment trap in various aquatic environments. These hydrodynamically shaped discs are deployed at discrete time intervals from the Intervalometer and provide markers that delineate time intervals within the sediments that accumulate in the collection tube. The timer and mechanical system are lodged in an air-filled, water-tight pressure housing that is vertically hung within the confines of a cone-shaped sediment trap. The instrumentation has been operationally pressure tested to an equivalent water depth of approximately 1 km. Flaws discovered during extensive laboratory and pressure testing resulted in the implementation of several mechanical modifications (such as a redesign of the rotor and the discs) that improved the operation of the rotor assembly as well as the release of discs through the end cap. These results also identified a preferred azimuth placement of the rotor disc relative to the drop hole of the end cap. In the initial field trial, five sediment traps and coupled Intervalometers were attached to moored arrays and deployed at two sites off the coast of Southern California for approximately 8 months. Each of the instruments released 18 discs at the programmed 10 day intervals, except one unit, which experienced a malfunction after approximately 4 months. Most of the discs oriented in a near-horizontal position upon the surface of the sediment in the collection tubes. Sampling of the sediments for geochemical analyses was improved by these clearly defined markers, which indicated the changes in the flux and nature of sediments accumulated during the deployment period of each sediment trap.

Urgency for sustainable development in coastal urban areas with reference to weather pattern, land use, and water quality.

PubMed

Sheela, A M; Letha, J; Swarnalatha, K; Baiju, K V; Sankar, Divya

2014-05-01

Water pollution is one of the most critical problems affecting mankind. Weather pattern and land use of catchment area have significant role in quality of water bodies. Due to climate change, there is frequent variation in weather pattern all over the world. There is also rapid change in land use due to increase in population and urbanization. The study was carried out to analyze the effect of change in weather pattern during the monsoon periods of 2008 and 2012 on water quality of a tropical coastal lake system. The nature and extent of variation in different water quality parameters namely electrical conductivity (EC), magnesium (Mg), sodium (Na), chloride (Cl), sulphate (SO4), turbidity, Secchi disk depth, biochemical oxygen demand (BOD), phosphate (PO4), calcium (Ca), and water temperature as well as the effect of various land use activities in the lake basin on water quality have also been studied. There is significant reduction in precipitation, EC, Mg, Na, Cl, SO4, turbidity, and Secchi disk depths whereas a significant rise in the BOD, PO4, Ca, and water temperature were observed in 2012. This significant reduction in electrical conductivity during 2012 revealed that because of less precipitation, the lake was separated from the sea by the sandbar during most of the monsoon period and thereby interrupted the natural flushing process. This caused the accumulation of organic matter including phosphate and thereby resulting reduction in clarity and chlorophyll-a (algae) in the lake. The unsustainable development activities of Thiruvanathapuram city are mainly responsible for the degradation of water bodies. The lack of maintenance and augmentation activities namely replacement of old pipes and periodical cleaning of pipe lines of the old sewer system in the city results in the bypass of sewage into water bodies. Because of the existence of the old sewerage system, no effort has been taken by the individual establishment/house of the city to provide their own treatment system for sewage and sullage and the untreated wastes are discharged into these old sewer pipes and ultimately the wastes reach the water bodies. In this context, decentralized treatment of sewage, sullage, and garbage by individual houses/establishments/hotels/hospitals is a better option for the developing countries. With the rapid developmental activities, and due to the variation of precipitation due to climate change, it is highly essential to provide proper waste treatment/augmentation facilities in urban lake system because a slight variation in the weather pattern can result in serious implications in the already polluted water bodies.

The transiting dust clumps in the evolved disc of the Sun-like UXor RZ Psc

PubMed Central

Kenworthy, Matthew A.; Pepper, Joshua; Rodriguez, Joseph E.; Siverd, Robert J.; Stassun, Keivan G.; Wyatt, Mark C.

2017-01-01

RZ Psc is a young Sun-like star, long associated with the UXor class of variable stars, which is partially or wholly dimmed by dust clumps several times each year. The system has a bright and variable infrared excess, which has been interpreted as evidence that the dimming events are the passage of asteroidal fragments in front of the host star. Here, we present a decade of optical photometry of RZ Psc and take a critical look at the asteroid belt interpretation. We show that the distribution of light curve gradients is non-uniform for deep events, which we interpret as possible evidence for an asteroidal fragment-like clump structure. However, the clumps are very likely seen above a high optical depth midplane, so the disc’s bulk clumpiness is not revealed. While circumstantial evidence suggests an asteroid belt is more plausible than a gas-rich transition disc, the evolutionary status remains uncertain. We suggest that the rarity of Sun-like stars showing disc-related variability may arise because (i) any accretion streams are transparent and/or (ii) turbulence above the inner rim is normally shadowed by a flared outer disc. PMID:28280566

Observability of planet-disc interactions in CO kinematics

NASA Astrophysics Data System (ADS)

Pérez, Sebastián; Casassus, S.; Benítez-Llambay, P.

2018-06-01

Empirical evidence of planets in gas-rich circumstellar discs is required to constrain giant planet formation theories. Here we study the kinematic patterns which arise from planet-disc interactions and their observability in CO rotational emission lines. We perform three-dimensional hydrodynamical simulations of single giant planets, and predict the emergent intensity field with radiative transfer. Pressure gradients at planet-carved gaps, spiral wakes and vortices bear strong kinematic counterparts. The iso-velocity contours in the CO(2-1) line centroids vo reveal large-scale perturbations, corresponding to abrupt transitions from below sub-Keplerian to super-Keplerian rotation along with radial and vertical flows. The increase in line optical depth at the edge of the gap also modulates vo, but this is a mild effect compared to the dynamical imprint of the planet-disc interaction. The large-scale deviations from the Keplerian rotation thus allow the planets to be indirectly detected via the first moment maps of molecular gas tracers, at ALMA angular resolutions. The strength of these deviations depends on the mass of the perturber. This initial study paves the way to eventually determine the mass of the planet by comparison with more detailed models.

Abiotic control of underwater light in a drinking water reservoir: Photon budget analysis and implications for water quality monitoring

NASA Astrophysics Data System (ADS)

Watanabe, Shohei; Laurion, Isabelle; Markager, Stiig; Vincent, Warwick F.

2015-08-01

In optically complex inland waters, the underwater attenuation of photosynthetically active radiation (PAR) is controlled by a variable combination of absorption and scattering components of the lake or river water. Here we applied a photon budget approach to identify the main optical components affecting PAR attenuation in Lake St. Charles, a drinking water reservoir for Québec City, Canada. This analysis showed the dominant role of colored dissolved organic matter (CDOM) absorption (average of 44% of total absorption during the sampling period), but with large changes over depth in the absolute and relative contribution of the individual absorption components (water, nonalgal particulates, phytoplankton and CDOM) to PAR attenuation. This pronounced vertical variation occurred because of the large spectral changes in the light field with depth, and it strongly affected the average in situ diffuse absorption coefficients in the water column. For example, the diffuse absorption coefficient for pure-water in the ambient light field was 10-fold higher than the value previously measured in the blue open ocean and erroneously applied to lakes and coastal waters. Photon absorption budget calculations for a range of limnological conditions confirmed that phytoplankton had little direct influence on underwater light, even at chlorophyll a values above those observed during harmful algal blooms in the lake. These results imply that traditional measures of water quality such as Secchi depth and radiometric transparency do not provide a meaningful estimate of the biological state of the water column in CDOM-colored lakes and reservoirs.

Eutrophication in the Yunnan Plateau lakes: the influence of lake morphology, watershed land use, and socioeconomic factors.

PubMed

Liu, Wenzhi; Li, Siyue; Bu, Hongmei; Zhang, Quanfa; Liu, Guihua

2012-03-01

Lakes play an important role in socioeconomic development and ecological balance in China, but their water quality has deteriorated considerably in recent decades. In this study, we investigated the spatial-temporal variations of eutrophication parameters (secchi depth, total nitrogen, total phosphorus, chemical oxygen demand, chlorophyll-a, trophic level index, and trophic state index) and their relationships with lake morphology, watershed land use, and socioeconomic factors in the Yunnan Plateau lakes. Results indicated that about 77.8% of lakes were eutrophic according to trophic state index. The plateau lakes showed spatial variations in water quality and could be classified into high-nutrient and low-nutrient groups. However, because watersheds were dominated by vegetation, all eutrophication parameters except chlorophyll-a showed no significant differences between the wet and dry seasons. Lake depth, water residence time, volume, and percentage of built-up land were significantly related to several eutrophication parameters. Agricultural land use and social-economic factors had no significant correlation with all eutrophication parameters. Stepwise regression analyses demonstrated that lake depth and water residence time accounted for 73.8% to 87.6% of the spatial variation of single water quality variables, respectively. Redundancy analyses indicated that lake morphology, watershed land use, and socioeconomic factors together explained 74.3% of the spatial variation in overall water quality. The results imply that water quality degradation in the plateau lakes may be mainly due to the domestic and industrial wastewaters. This study will improve our understanding of the determinants of lake water quality and help to design efficient strategies for controlling eutrophication in the plateau region.

From toes to top-of-atmosphere: Fowler's Sneaker Depth index of water clarity for the Chesapeake Bay.

PubMed

Crooke, Benjamin; McKinna, Lachlan I W; Cetinić, Ivona

2017-04-17

Fowler's Sneaker Depth (FSD), analogous to the well known Secchi disk depth (Zsd), is a visually discerned citizen scientist metric used to assess water clarity in the Patuxent River estuary. In this study, a simple remote sensing algorithm was developed to derive FSD from space-borne spectroradiometric imagery. An empirical model was formed that estimates FSD from red-end remote sensing reflectances at 645 nm, Rrs(645). The model is based on a hyperbolic function relating water clarity to Rrs(645) that was established using radiative transfer modeling and fine tuned using in-water FSD measurements and coincident Rrs(645) data observed by NASA's Moderate Resolution Imaging Spectroradiometer aboard the Aqua spacecraft (MODISA). The resultant FSD algorithm was applied to Landsat-8 Operational Land Imager data to derive a short time-series for the Patuxent River estuary from January 2015 to June 2016. Satellite-derived FSD had an inverse, statistically significant relationship (p<0.005) with total suspended sediment concentration (TSS). Further, a distinct negative relationship between FSD and chlorophyll concentration was discerned during periods of high biomass (> 4 μg L^-1). The complex nature of water quality in the mid-to-upper Chesapeake Bay was captured using a MODISA-based FSD time series (2002-2016). This study demonstrates how a citizen scientist-conceived observation can be coupled with remote sensing. With further refinement and validation, the FSD may be a useful tool for delivering scientifically relevant results and for informing and engaging local stakeholders and policy makers.

Is the X-discontinuity really related to the presence of eclogite bodies in the mantle?

NASA Astrophysics Data System (ADS)

Woodland, Alan; Knapp, Nadia; Klimm, Kevin

2013-04-01

A local seismic feature observed at ~300 km depth is referred to as the X-discontinuity (X-disc, e.g. Revenaugh & Jordan 1991). Several petrological explanations have been proposed for this discontinuity, but Pushcharovsky & Pushcharovsky (2012) attribute it to the formation of stishovite in eclogitic bodies, based upon the suggestion of Williams & Revenaugh (2005). If this link between the X-disc and the presence of eclogite is valid, it could have important geodynamic implications. In their model, stishovite appears in the eclogitic assemblage either through the transformation of previously existing free coesite or by exsolution of "excess" SiO2 from Ca-Eskola-bearing clinopyroxene (Ca0.50.5Si2O6). Essential to this model is if the amount of free SiO2 is enough to produce the observed seismic impedance contrast or not. To test whether exsolution of stishovite from Ca-Eskola-bearing clinopyroxene is a feasible mechanism, we have undertaken high-pressure experiments to determine the maximum Ca-Eskola component that can be incorporated in clinopyroxene over a range of P-T conditions, both shallower and deeper than that corresponding to the position of the X-disc. One series of experiments were performed in the simplified CaO-MgO-Al2O3-SiO2±Na2O system and one with 3 "natural" analog eclogite compositions (K2O-Na2O-CaO-MgO-FeO-Al2O3-SiO2). For the CMAS-experiments, all samples have the typical eclogitic assemblage of clinopyroxene + garnet ± SiO2 ± kyanite. With increasing pressure, the amount of garnet increases at the expense of clinopyroxene. Maximizing the Ca-Eskola content of clinopyroxene requires coexistence with a free SiO2 phase and an elevated Al2O3 content, but not necessarily the presence of kyanite. Ca-Eskola contents of ~20 mol % are obtained at 4 GPa, but decrease steadily with increasing pressure so that ˜ 4 mol % is present at pressures corresponding to the depth of the X-disc. Experiments in natural analog eclogite compositions produced even less Ca-Eskola component in clinopyroxene. Thus no sharp change in Ca-Eskola content occurs as a function of pressure and at depths corresponding to the X-discontinuity exsolution of all Ca-Eskola component will yield only < 1 wt% free SiO2. This amount is insufficient to produce a large enough impedance contrast to explain the X-disc. If the X-disc is related to the appearance of stishovite in eclogite as proposed by Williams & Revenaugh (2005), then free SiO2 must be already present in the mineral assemblage. However, our preliminary results suggest that in an unmodified MORB-type eclogite only minor amounts of free SiO2 will be present. Greater amounts of free SiO2 can only be reached in eclogite residues after melt extraction at high pressures of ~5 GPa, where as residues from melting at lower pressures (i.e. 2.5 GPa) do not produce any free SiO2. Therefore, if at all, only subducted oceanic crust that first experienced melting at high pressures can contain enough free SiO2 to produce the observed impedance contrast of the X-disc as it transforms to stishovite. Pushcharovsky DY & Pushcharovsky YM (2012) Earth-Sci Revs, 113, 94-109. Revenaugh J & Jordan TH (1991) J Geophys Res, 96, 19,781- 19,810, Williams Q & Revenaugh J (2005) Geology, 33, 1-4.

Table Rock Lake Water-Clarity Assessment Using Landsat Thematic Mapper Satellite Data

USGS Publications Warehouse

Krizanich, Gary; Finn, Michael P.

2009-01-01

Water quality of Table Rock Lake in southwestern Missouri is assessed using Landsat Thematic Mapper satellite data. A pilot study uses multidate satellite image scenes in conjunction with physical measurements of secchi disk transparency collected by the Lakes of Missouri Volunteer Program to construct a regression model used to estimate water clarity. The natural log of secchi disk transparency is the dependent variable in the regression and the independent variables are Thematic Mapper band 1 (blue) reflectance and a ratio of the band 1 and band 3 (red) reflectance. The regression model can be used to reliably predict water clarity anywhere within the lake. A pixel-level lake map of predicted water clarity or computed trophic state can be produced from the model output. Information derived from this model can be used by water-resource managers to assess water quality and evaluate effects of changes in the watershed on water quality.

Adaptations in rod outer segment disc membranes in response to environmental lighting conditions.

PubMed

Rakshit, Tatini; Senapati, Subhadip; Parmar, Vipul M; Sahu, Bhubanananda; Maeda, Akiko; Park, Paul S-H

2017-10-01

The light-sensing rod photoreceptor cell exhibits several adaptations in response to the lighting environment. While adaptations to short-term changes in lighting conditions have been examined in depth, adaptations to long-term changes in lighting conditions are less understood. Atomic force microscopy was used to characterize the structure of rod outer segment disc membranes, the site of photon absorption by the pigment rhodopsin, to better understand how photoreceptor cells respond to long-term lighting changes. Structural properties of the disc membrane changed in response to housing mice in constant dark or light conditions and these adaptive changes required output from the phototransduction cascade initiated by rhodopsin. Among these were changes in the packing density of rhodopsin in the membrane, which was independent of rhodopsin synthesis and specifically affected scotopic visual function as assessed by electroretinography. Studies here support the concept of photostasis, which maintains optimal photoreceptor cell function with implications in retinal degenerations. Copyright © 2017 Elsevier B.V. All rights reserved.

Limnology of nine small lakes, Matanuska-Susitna Borough, Alaska, and the survival and growth rates of rainbow trout

USGS Publications Warehouse

Woods, P.F.

1985-01-01

The survival and growth rates of rainbow trout (Salmo gairdnieri) were concurrently measured with selected limnological characteristics in nine small (surface area < 25 sq hectometers) lakes in the Matanuska-Susitna Borough. The project goal was to develop empirical models for predicting rainbow trout growth rates from the following variables: total phosphorus concentration, chlorophyll a concentration, Secchi disc transparency, or the morphoedaphic index--a means of characterizing potential biological productivity. No suitable model could be developed from the data collected during 1982 and 1983. The lack of significant correlation was attributed in part to the wide variation in survival of rainbow trout. Winterkills, caused by severe depletion of dissolved oxygen, were suspected in four of the lakes. Varied levels of fishing pressure and competition with threespine stickleback (Gasterosteus aculeatus) also influenced survival of rainbow trout but their effects were overshadowed by winterkill. Predictive capability was also reduced because of inconsistencies in rankings generated by each of the four limnological variables chosen as indicators of potential biological productivity. A lake ranked low in productivity by one variable was commonly ranked high in productivity by another variable. The survivability of rainbow trout stocked in lakes such as these nine may be a more important indicator of potential biomass production than are indicators of lake fertility. Assessments of a lake 's susceptibility to winterkill and the degree of competition with threespine stickleback are suggested as important topics for additional research. (Author 's abstract)

A new device for acquiring ground truth on the absorption of light by turbid waters

NASA Technical Reports Server (NTRS)

Klemas, V. (Principal Investigator); Srna, R.; Treasure, W.

1974-01-01

The author has identified the following significant results. A new device, called a Spectral Attenuation Board, has been designed and tested, which enables ERTS-1 sea truth collection teams to monitor the attenuation depths of three colors continuously, as the board is being towed behind a boat. The device consists of a 1.2 x 1.2 meter flat board held below the surface of the water at a fixed angle to the surface of the water. A camera mounted above the water takes photographs of the board. The resulting film image is analyzed by a micro-densitometer trace along the descending portion of the board. This yields information on the rate of attenuation of light penetrating the water column and the Secchi depth. Red and green stripes were painted on the white board to approximate band 4 and band 5 of the ERTS MSS so that information on the rate of light absorption by the water column of light in these regions of the visible spectrum could be concurrently measured. It was found that information from a red, green, and white stripe may serve to fingerprint the composition of the water mass. A number of these devices, when automated, could also be distributed over a large region to provide a cheap method of obtaining valuable satellite ground truth data at present time intervals.

Multiple extreme environmental conditions of intermittent soda pans in the Carpathian Basin (Central Europe)

PubMed Central

Boros, Emil; Katalin, V.-Balogh; Vörös, Lajos; Horváth, Zsófia

2017-01-01

Soda lakes and pans represent saline ecosystems with unique chemical composition, occurring on all continents. The purpose of this study was to identify and characterise the main environmental gradients and trophic state that prevail in the soda pans (n=84) of the Carpathian Basin in Central Europe. Underwater light conditions, dissolved organic matter, phosphorus and chlorophyll a were investigated in 84 pans during 2009–2010. Besides, water temperature was measured hourly with an automatic sensor throughout one year in a selected pan. The pans were very shallow (median depth: 15 cm), and their extremely high turbidity (Secchi depth median: 3 cm, min: 0.5 cm) was caused by high concentrations of inorganic suspended solids (median: 0.4 g L–1, max: 16 g L–1), which was the dominant (>50%) contributing factor to the vertical attenuation coefficient in 67 pans (80%). All pans were polyhumic (median DOC: 47 mg L–1), and total phosphorus concentration was also extremely high (median: 2 mg L–1, max: 32 mg L–1). The daily water temperature maximum (44 °C) and fluctuation maximum (28 °C) were extremely high during summertime. The combination of environmental boundaries: shallowness, daily water temperature fluctuation, intermittent hydroperiod, high turbidity, polyhumic organic carbon concentration, high alkalinity and hypertrophy represent a unique extreme aquatic ecosystem. PMID:28572691

Bulk Comptonization by Turbulence in Black Hole Accretion Discs

NASA Astrophysics Data System (ADS)

Kaufman, Jason

Radiation pressure dominated accretion discs may have turbulent velocities that exceed the electron thermal velocities. Bulk Comptonization by the turbulence may therefore dominate over thermal Comptonization in determining the emergent spectrum. We discuss how to self-consistently resolve and interpret this effect in calculations of spectra of radiation MHD simulations. In particular, we show that this effect is dominated by radiation viscous dissipation and can be treated as thermal Comptonization with an equivalent temperature. We investigate whether bulk Comptonization may provide a physical basis for warm Comptonization models of the soft X-ray excess in AGN. We characterize our results with temperatures and optical depths to make contact with other models of this component. We show that bulk Comptonization shifts the Wien tail to higher energy and lowers the gas temperature, broadening the spectrum. More generally, we model the dependence of this effect on a wide range of fundamental accretion disc parameters, such as mass, luminosity, radius, spin, inner boundary condition, and the alpha parameter. Because our model connects bulk Comptonization to one dimensional vertical structure temperature profiles in a physically intuitive way, it will be useful for understanding this effect in future simulations run in new regimes. We also develop a global Monte Carlo code to study this effect in global radiation MHD simulations. This code can be used more broadly to compare global simulations with observed systems, and in particular to investigate whether magnetically dominated discs can explain why observed high Eddington accretion discs appear to be thermally stable.

Disk displacement, eccentric condylar position, osteoarthrosis - misnomers for variations of normality? Results and interpretations from an MRI study in two age cohorts.

PubMed

Türp, Jens C; Schlenker, Anna; Schröder, Johannes; Essig, Marco; Schmitter, Marc

2016-11-17

Clinical decision-making and prognostic statements in individuals with manifest or suspected temporomandibular disorders (TMDs) may involve assessment of (a) the position of articular disc relative to the mandibular condyle, (b) the location of the condyle relative to the temporal joint surfaces, and (c) the depth of the glenoid fossa of the temporomandibular joints (TMJs). The aim of this study was twofold: (1) Determination of the prevalence of these variables in two representative population-based birth cohorts. (2) Reinterpretation of the clinical significance of the findings. From existing magnetic resonance imaging (MRI) scans of the TMJs that had been taken in 2005 and 2006 from 72 subjects born between 1930 and 1932 and between 1950 and 1952, respectively, the condylar position at closed jaw was calculated as percentage displacement of the condyle from absolute centricity. By using the criteria introduced by Orsini et al. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 86:489-97, 1998), a textbook-like disc position at closed jaw was distinguished from an anterior location. TMJ morphology of the temporal joint surfaces was assessed at open jaw by measuring the depth of the glenoid fossa, using the method proposed by Muto et al. (J Oral Maxillofac Surg 52:1269-72, 1994). Frequency distributions were recorded for the condylar and disc positions at closed jaw. Student's t-test with independent samples was used as test of significance to detect differences of condylar positions between the age cohorts (1930 vs. 1950) and the sexes. The significance levels were set at 5%. First, the results from the measurement of the age cohorts were compared without differentiation of sexes, i.e., age cohort 1930-1932 versus age cohort 1950-1952. Subsequently, the age cohorts were compared by sex, i.e., men in cohort 1930-1932 versus men in cohort 1950-1952, and women in cohort 1930-1932 women men in cohort 1950-1952. In both cohorts, condylar position was characterized by great variability. About 50% of the condyles were located centrically, while the other half was either in an anterior or in a posterior position. In both female cohorts, a posterior position predominated, whereas a centric position prevailed among men. Around 75% of the discs were positioned textbook-like, while the remaining forth was located anteriorly. Age had no statistically significant influence on condylar or on disc position. Conversely, comparison between the age groups revealed a statistically significant decrease of the depth of the glenoid fossa in both older cohorts. This age-dependent changes may be interpreted as flattening of the temporal joint surfaces. We call for a re-interpretation of imaging findings because they may insinuate pathology which usually is not present. Instead, anterior or posterior positions of the mandibular condyle as well as an anterior location of the articular disc should be construed as a variation of normalcy. Likewise, flattening of articular surfaces of the TMJs may be considered as normal adaptive responses to increased loading, rather than pathological degenerative changes. Not applicable.

The relationship between 3D morphology of optic disc and spatial patterns of visual field loss in glaucoma

NASA Astrophysics Data System (ADS)

Wang, Mengyu; Wang, Hui; Baniasadi, Neda; Elze, Tobias

2017-02-01

Purpose: Optic disc tilt defined over 3D optic disc morphology has been shown to be associated with the location of initial glaucomatous damages. In this work, we study the impact of optic cup depth (OCD) on spatial patterns of visual field loss in glaucoma. Methods: Pairs of reliable Cirrus OCT scans around optic disc and Humphrey visual fields of glaucoma patients without visually significant cataract and age-related macular degeneration were selected. The most recent visit of a randomly selected eye of each patient was chosen. The OCD was automatically calculated on the superior-inferior cross sectional image passing through the optic disc center. The correlations between the mean pattern deviation (PD) of each sector in glaucoma hemifield test (GHT) and Garway-Heath scheme and OCD were evaluated for all severities glaucoma and mild glaucoma (mean deviation >= -5 dB), respectively. Results: 424 eyes of 424 patients passed the data reliability criteria with 346 mild glaucoma patients. For all severities glaucoma, there was no significant correlation between the mean sector PD and OCD. For mild glaucoma, OCD was uniquely correlated to the mean PD of the inferior pericentral sector (r=-0.18, p=0.01) in GHT, which was independent of mean deviation and retinal nerve fiber layer thickness (p<0.001 for both). Conclusion: OCD was uniquely correlated to the vision loss of the inferior pericentral sector in GHT and Garway- Health scheme for mild glaucoma. Future advancement of OCT imaging techniques may provide better clinical diagnosis for early glaucoma by focusing on 3D morphological variation of the optic disc.

The Analysis of Alpha Beta Pruning and MTD(f) Algorithm to Determine the Best Algorithm to be Implemented at Connect Four Prototype

NASA Astrophysics Data System (ADS)

Tommy, Lukas; Hardjianto, Mardi; Agani, Nazori

2017-04-01

Connect Four is a two-player game which the players take turns dropping discs into a grid to connect 4 of one’s own discs next to each other vertically, horizontally, or diagonally. At Connect Four, Computer requires artificial intelligence (AI) in order to play properly like human. There are many AI algorithms that can be implemented to Connect Four, but the suitable algorithms are unknown. The suitable algorithm means optimal in choosing move and its execution time is not slow at search depth which is deep enough. In this research, analysis and comparison between standard alpha beta (AB) Pruning and MTD(f) will be carried out at the prototype of Connect Four in terms of optimality (win percentage) and speed (execution time and the number of leaf nodes). Experiments are carried out by running computer versus computer mode with 12 different conditions, i.e. varied search depth (5 through 10) and who moves first. The percentage achieved by MTD(f) based on experiments is win 45,83%, lose 37,5% and draw 16,67%. In the experiments with search depth 8, MTD(f) execution time is 35, 19% faster and evaluate 56,27% fewer leaf nodes than AB Pruning. The results of this research are MTD(f) is as optimal as AB Pruning at Connect Four prototype, but MTD(f) on average is faster and evaluates fewer leaf nodes than AB Pruning. The execution time of MTD(f) is not slow and much faster than AB Pruning at search depth which is deep enough.

XPS and bioactivity study of the bisphosphonate pamidronate adsorbed onto plasma sprayed hydroxyapatite coatings

NASA Astrophysics Data System (ADS)

McLeod, Kate; Kumar, Sunil; Smart, Roger St. C.; Dutta, Naba; Voelcker, Nicolas H.; Anderson, Gail I.; Sekel, Ron

2006-12-01

This paper reports the use of X-ray photoelectron spectroscopy (XPS) to investigate bisphosphonate (BP) adsorption onto plasma sprayed hydroxyapatite (HA) coatings commonly used for orthopaedic implants. BPs exhibit high binding affinity for the calcium present in HA and hence can be adsorbed onto HA-coated implants to exploit their beneficial properties for improved bone growth at the implant interface. A rigorous XPS analysis of pamidronate, a commonly used nitrogenous BP, adsorbed onto plasma sprayed HA-coated cobalt-chromium substrates has been carried out, aimed at: (a) confirming the adsorption of this BP onto HA; (b) studying the BP diffusion profile in the HA coating by employing the technique of XPS depth profiling; (c) confirming the bioactivity of the adsorbed BP. XPS spectra of plasma sprayed HA-coated discs exposed to a 10 mM aqueous BP solution (pamidronate) for periods of 1, 2 and 24 h showed nitrogen and phosphorous photoelectron signals corresponding to the BP, confirming its adsorption onto the HA substrate. XPS depth profiling of the 2 h BP-exposed HA discs showed penetration of the BP into the HA matrix to depths of at least 260 nm. The bioactivity of the adsorbed BP was confirmed by the observed inhibition of osteoclast (bone resorbing) cell activity. In comparison to the HA sample, the HA sample with adsorbed BP exhibited a 25-fold decrease in primary osteoclast cells.

Effect of moderate intraocular pressure changes on topographic measurements with confocal scanning laser tomography in patients with glaucoma.

PubMed

Nicolela, Marcelo T; Soares, Adael S; Carrillo, Monica M; Chauhan, Balwantray C; LeBlanc, Raymond P; Artes, Paul H

2006-05-01

To evaluate optic disc topography changes after intraocular pressure (IOP) modulation in patients with glaucoma. Twenty-three patients with glaucoma were studied. Three mean optic disc topography images were obtained with the Heidelberg Retina Tomograph II at baseline and weeks 1, 2, 4, and 8 (visits 1, 2, 3, 4, and 5, respectively). Topical medications were discontinued in the study eye after visit 1 and resumed after visit 4 but maintained in the contralateral control eye. Central corneal thickness was measured at the last visit. Topographic changes were determined by stereometric parameters (rim area and mean cup depth) and at discrete topographic locations using the Topographic Change Analysis program (from the Heidelberg Retina Tomograph II). In the study eyes, IOP increased significantly (5.4 mm Hg at visit 4; P<.001) after withdrawal of topical medications but returned to baseline levels after resuming medications; no statistically significant topographic changes, however, were observed. Moreover, no relationship between change in IOP and stereometric parameters was observed. Central corneal thickness was not associated with changes in optic disc topography induced by IOP modulation. In patients with glaucoma, significant but relatively moderate IOP increases and decreases on the order of 5 mm Hg did not appear to have an effect on optic disc topography.

Deep and wide gaps by super Earths in low-viscosity discs

NASA Astrophysics Data System (ADS)

Ginzburg, Sivan; Sari, Re'em

2018-06-01

Planets can open cavities (gaps) in the protoplanetary gaseous discs in which they are born by exerting gravitational torques. Viscosity counters these torques and limits the depletion of the gaps. We present a simple one-dimensional scheme to calculate the gas density profile inside gaps by balancing the gravitational and viscous torques. By generalizing the results of Goodman & Rafikov (2001), our scheme properly accounts for the propagation of angular momentum by density waves. This method allows us to easily study low-viscosity discs, which are challenging for full hydrodynamical simulations. We complement our numerical integration by analytical equations for the gap's steady-state depth and width as a function of the planet's to star's mass ratio μ, the gas disc's aspect ratio h, and its Shakura & Sunyaev viscosity parameter α. Specifically, we focus on low-mass planets (μ < μth ≡ h3) and identify a new low-viscosity regime, α < h(μ/μth)5, in which the classical analytical scaling relations are invalid. Equivalently, this low-viscosity regime applies to every gap that is depleted by more than a factor of (μth/μ)3 relative to the unperturbed density. We show that such gaps are significantly deeper and wider than previously thought, and consequently take a longer time to reach equilibrium.

Kerr Reservoir LANDSAT experiment analysis for November 1980

NASA Technical Reports Server (NTRS)

Lecroy, S. R.

1982-01-01

An experiment was conducted on the waters of Kerr Reservoir to determine if reliable algorithms could be developed that relate water quality parameters to remotely sensed data. LANDSAT radiance data was used in the analysis since it is readily available and covers the area of interest on a regular basis. By properly designing the experiment, many of the unwanted variations due to atmosphere, solar, and hydraulic changes were minimized. The algorithms developed were constrained to satisfy rigorous statistical criteria before they could be considered dependable in predicting water quality parameters. A complete mix of different types of algorithms using the LANDSAT bands was generated to provide a thorough understanding of the relationships among the data involved. The study demonstrated that for the ranges measured, the algorithms that satisfactorily represented the data are mostly linear and only require a maximum of one or two LANDSAT bands. Rationing techniques did not improve the results since the initial design of the experiment minimized the errors that this procedure is effective against. Good correlations were established for inorganic suspended solids, iron, turbidity, and secchi depth.

A Comprehensive Review on Water Quality Parameters Estimation Using Remote Sensing Techniques.

PubMed

Gholizadeh, Mohammad Haji; Melesse, Assefa M; Reddi, Lakshmi

2016-08-16

Remotely sensed data can reinforce the abilities of water resources researchers and decision makers to monitor waterbodies more effectively. Remote sensing techniques have been widely used to measure the qualitative parameters of waterbodies (i.e., suspended sediments, colored dissolved organic matter (CDOM), chlorophyll-a, and pollutants). A large number of different sensors on board various satellites and other platforms, such as airplanes, are currently used to measure the amount of radiation at different wavelengths reflected from the water's surface. In this review paper, various properties (spectral, spatial and temporal, etc.) of the more commonly employed spaceborne and airborne sensors are tabulated to be used as a sensor selection guide. Furthermore, this paper investigates the commonly used approaches and sensors employed in evaluating and quantifying the eleven water quality parameters. The parameters include: chlorophyll-a (chl-a), colored dissolved organic matters (CDOM), Secchi disk depth (SDD), turbidity, total suspended sediments (TSS), water temperature (WT), total phosphorus (TP), sea surface salinity (SSS), dissolved oxygen (DO), biochemical oxygen demand (BOD) and chemical oxygen demand (COD).

A Comprehensive Review on Water Quality Parameters Estimation Using Remote Sensing Techniques

PubMed Central

Gholizadeh, Mohammad Haji; Melesse, Assefa M.; Reddi, Lakshmi

2016-01-01

Remotely sensed data can reinforce the abilities of water resources researchers and decision makers to monitor waterbodies more effectively. Remote sensing techniques have been widely used to measure the qualitative parameters of waterbodies (i.e., suspended sediments, colored dissolved organic matter (CDOM), chlorophyll-a, and pollutants). A large number of different sensors on board various satellites and other platforms, such as airplanes, are currently used to measure the amount of radiation at different wavelengths reflected from the water’s surface. In this review paper, various properties (spectral, spatial and temporal, etc.) of the more commonly employed spaceborne and airborne sensors are tabulated to be used as a sensor selection guide. Furthermore, this paper investigates the commonly used approaches and sensors employed in evaluating and quantifying the eleven water quality parameters. The parameters include: chlorophyll-a (chl-a), colored dissolved organic matters (CDOM), Secchi disk depth (SDD), turbidity, total suspended sediments (TSS), water temperature (WT), total phosphorus (TP), sea surface salinity (SSS), dissolved oxygen (DO), biochemical oxygen demand (BOD) and chemical oxygen demand (COD). PMID:27537896

LANDSAT-1 data as it has been applied for land use and water quality data by the Virginia State Water Control Board. 1: The state project. 2: Monitoring water quality from LANDSAT

NASA Technical Reports Server (NTRS)

Trexler, P. L.; Barker, J. L.

1975-01-01

LANDSAT-1 imagery has been used for water quality and land use monitoring in and around the Swift Creek and Lake Chesdin Reservoirs in Virginia. This has proved useful by (1) helping determine valid reservoir sampling stations, (2) monitoring areas not accessible by land or water, (3) giving the State a viable means of measuring Secchi depth readings in these inaccessible areas, (4) giving an overview of trends in changing sedimentation loadings over a given time period and classifying these waters into various categories, (5) enabling the State to inventory all major lakes and reservoirs and computing their acreage, (6) monitoring land use changes in any specific area, (7) evaluating possible long-term environmental effects of nearby developments, and (8) monitoring and predicting population shifts with possible impact on water quality problems. The main problems in the long-term use of such imagery appear to be cost and lack of consistency due to cloud cover limitations.

Production of a water quality map of Saginaw Bay by computer processing of LANDSAT-2 data

NASA Technical Reports Server (NTRS)

Mckeon, J. B.; Rogers, R. H.; Smith, V. E.

1977-01-01

Surface truth and LANDSAT measurements collected July 31, 1975, for Saginaw Bay were used to demonstrate a technique for producing a color coded water quality map. On this map, color was used as a code to quantify five discrete ranges in the following water quality parameters: (1) temperature, (2) Secchi depth, (3) chloride, (4) conductivity, (5) total Kjeldahl nitrogen, (6) total phosphorous, (7)chlorophyll a, (8) total solids and (9) suspended solids. The LANDSAT and water quality relationship was established through the use of a set of linear regression equations where the water quality parameters are the dependent variables and LANDSAT measurements are the independent variables. Although the procedure is scene and surface truth dependent, it provides both a basis for extrapolating water quality parameters from point samples to unsampled areas and a synoptic view of water mass boundaries over the 3000 sq. km bay area made from one day's ship data that is superior, in many ways, to the traditional machine contoured maps made from three day's ship data.

Interannual and long-term changes in the trophic state of a multibasin lake: Effects of morphology, climate, winter aeration, and beaver activity

USGS Publications Warehouse

Robertson, Dale M.; Rose, William; Reneau, Paul C.

2016-01-01

Little St. Germain Lake (LSG), a relatively pristine multibasin lake in Wisconsin, USA, was examined to determine how morphologic (internal), climatic (external), anthropogenic (winter aeration), and natural (beaver activity) factors affect the trophic state (phosphorus, P; chlorophyll, CHL; and Secchi depth, SD) of each of its basins. Basins intercepting the main flow and external P sources had highest P and CHL and shallowest SD. Internal loading in shallow, polymictic basins caused P and CHL to increase and SD to decrease as summer progressed. Winter aeration used to eliminate winterkill increased summer internal P loading and decreased water quality, while reductions in upstream beaver impoundments had little effect on water quality. Variations in air temperature and precipitation affected each basin differently. Warmer air temperatures increased productivity throughout the lake and decreased clarity in less eutrophic basins. Increased precipitation increased P in the basins intercepting the main flow but had little effect on the isolated deep West Bay. These relations are used to project effects of future climatic changes on LSG and other temperate lakes.

The correlation and quantification of airborne spectroradiometer data to turbidity measurements at Lake Powell, Utah

NASA Technical Reports Server (NTRS)

Merry, C. J.

1979-01-01

A water sampling program was accomplished at Lake Powell, Utah, during June 1975 for correlation to multispectral data obtained with a 500-channel airborne spectroradiometer. Field measurements were taken of percentage of light transmittance, surface temperature, pH and Secchi disk depth. Percentage of light transmittance was also measured in the laboratory for the water samples. Analyses of electron micrographs and suspended sediment concentration data for four water samples located at Hite Bridge, Mile 168, Mile 150 and Bullfrog Bay indicated differences in the composition and concentration of the particulate matter. Airborne spectroradiometer multispectral data were analyzed for the four sampling locations. The results showed that: (1) as the percentage of light transmittance of the water samples decreased, the reflected radiance increased; and (2) as the suspended sediment concentration (mg/l) increased, the reflected radiance increased in the 1-80 mg/l range. In conclusion, valuable qualitative information was obtained on surface turbidity for the Lake Powell water spectra. Also, the reflected radiance measured at a wavelength of 0.58 micron was directly correlated to the suspended sediment concentration.

Observability of forming planets and their circumplanetary discs - I. Parameter study for ALMA

NASA Astrophysics Data System (ADS)

Szulágyi, J.; Plas, G. van der; Meyer, M. R.; Pohl, A.; Quanz, S. P.; Mayer, L.; Daemgen, S.; Tamburello, V.

2018-01-01

We present mock observations of forming planets with Atacama Large Millimeter Array (ALMA). The possible detections of circumplanetary discs (CPDs) were investigated around planets of Saturn, 1, 3, 5, and 10 Jupiter-masses that are placed at 5.2 au from their star. The radiative, 3D hydrodynamic simulations were then post-processed with RADMC3D and the ALMA observation simulator. We found that even though the CPDs are too small to be resolved, they are hot due to the accreting planet in the optically thick limit; therefore, the best chance to detect them with continuum observations in this case is at the shortest ALMA wavelengths, such as band 9 (440 μm). Similar fluxes were found in the case of Saturn and Jupiter-mass planets, as for the 10 MJup gas-giant, due to temperature-weighted optical depth effects: when no deep gap is carved, the planet region is blanketed by the optically thick circumstellar disc leading to a less efficient cooling there. A test was made for a 52 au orbital separation, which showed that optically thin CPDs are also detectable in band 7 but they need longer integration times (>5 h). Comparing the gap profiles of the same simulation at various ALMA bands and the hydro simulation confirmed that they change significantly, first because the gap is wider at longer wavelengths due to decreasing optical depth; secondly, the beam convolution makes the gap shallower and at least 25 per cent narrower. Therefore, caution has to be made when estimating planet masses based on ALMA continuum observations of gaps.

Global dust attenuation in disc galaxies: strong variation with specific star formation and stellar mass, and the importance of sample selection

NASA Astrophysics Data System (ADS)

Devour, Brian M.; Bell, Eric F.

2016-06-01

We study the relative dust attenuation-inclination relation in 78 721 nearby galaxies using the axis ratio dependence of optical-near-IR colour, as measured by the Sloan Digital Sky Survey, the Two Micron All Sky Survey, and the Wide-field Infrared Survey Explorer. In order to avoid to the greatest extent possible attenuation-driven biases, we carefully select galaxies using dust attenuation-independent near- and mid-IR luminosities and colours. Relative u-band attenuation between face-on and edge-on disc galaxies along the star-forming main sequence varies from ˜0.55 mag up to ˜1.55 mag. The strength of the relative attenuation varies strongly with both specific star formation rate and galaxy luminosity (or stellar mass). The dependence of relative attenuation on luminosity is not monotonic, but rather peaks at M3.4 μm ≈ -21.5, corresponding to M* ≈ 3 × 1010 M⊙. This behaviour stands seemingly in contrast to some older studies; we show that older works failed to reliably probe to higher luminosities, and were insensitive to the decrease in attenuation with increasing luminosity for the brightest star-forming discs. Back-of-the-envelope scaling relations predict the strong variation of dust optical depth with specific star formation rate and stellar mass. More in-depth comparisons using the scaling relations to model the relative attenuation require the inclusion of star-dust geometry to reproduce the details of these variations (especially at high luminosities), highlighting the importance of these geometrical effects.

OCoc- from Ocean Colour to Organic Carbon

NASA Astrophysics Data System (ADS)

Heim, B.; Overduin, P. P.; Schirrmeister, L.; Lantuit, H.; Doerffer, R.

2009-12-01

Enhanced permafrost warming and increased arctic river discharges have heightened concern about the input of terrigenous matter into Arctic coastal waters. The ‘OCoc-from Ocean Colour to Organic Carbon’ project (IPY-project 1176), funded by the German Research Foundation (DFG), is an Ocean Colour study joined with the Arctic Coastal Dynamics ACD network and Arctic Circum-polar Coastal Observatory Network ACCO-Net (IPY-project 90). OCoc uses Ocean Colour satellite data for synoptical monitoring of organic matter fluxes from fluvial and coastal sources. Initial results from German-Russian expeditions at the southeastern Laptev Sea Coast (Arctic Siberia, Russia) in August 2008 and August 2009 are presented. Large parts of this coastal zone are characterized by highly erosive organic-rich material. Ocean Colour MERIS Reduced Resolution (RR)-LIB data of the have been processed towards optical aquatic parameters using Beam-Visat4.2 and the MERIS case2 regional processor for coastal application (C2R). Calculated aquatic parameters are absorption and backscattering coefficients, apparent optical properties such as the first attenuation depth (‘Z90’) and calculated concentrations of chlorophyll, total suspended matter and coloured dissolved organic matter absorption from the water leaving reflectances. Initial comparisons with expedition data (Secchi depths, cDOM) show that the MERIS-C2R optical parameters ’total absorption’ and the first attenuation depth, ’Z90’, seem adequately to represent true conditions. High attenuation values in the spectral blue wavelength range may serve as tracer for the organic-rich terrigenous input. The synoptic information of Ocean Colour products will provide valuable spatial and dynamical information on the Organic Carbon and sediment fluxes from the Siberian permafrost coast.

Water-quality data for the Ohio River from New Cumberland Dam to Pike Island Dam, West Virginia and Ohio, June-November 1992

USGS Publications Warehouse

Miller, Kimberly F.; Faulkenburg, C.W.; Chambers, D.B.; Waldron, M.C.

1995-01-01

This report contains water-quality data for the Ohio River, collected during the summer and fall of 1992, from river mile 51.1 (3.3 miles upstream from New Cumberland Dam) to river mile 84.0 (0.2 miles upstream from Pike Island Dam). The data were collected to assess the effects of hydropower development on water quality. Water quality was determined by a combination of repeated synoptic field measurements and laboratory analyses. Synoptic measurements were made along a longitudinal transect with 18 mid-channel sampling sites; cross-sectional transects of water quality were measured at 5 of these sites. Water-quality measurements also were made at two sites located on the back-channel (Ohio) side of Browns Island. Water temperature, dissolved oxygen concentration, pH, and specific conductance were measured at each longitudinal-transect and back-channel sampling site. Longitudinal-transect and back-channel stations were sampled at three depths (about 3.3 feet below the surface of the water, middle of the water column, and near the bottom of the river). Cross-sectional transects consisted of three or four detailed vertical pro- files of the same characteristics. Water samples were collected from three depths at the mid-channel vertical profile in each cross-sectional transect and were analyzed for concentrations of phyto- plankton photosynthetic pigments chlorophyll a and chlorophyll b. Estimates of the depth of light penetration (Secchi disk transparency) were made at pigment-sampling locations whenever light and river-surface conditions were appropriate. Synoptic sampling usually was completed in 12 hours or less and was repeated seven times between June 25 and November 6, 1992.

Stereoscopic Analysis of 19 May and 31 Aug 2007 Filament Eruptions

NASA Technical Reports Server (NTRS)

Liewer, Paulett; DeJong, E. M.; Hall, J. R.

2008-01-01

The presentation outline includes results from stereoscopic analysis of SECCHI/EUVI data for 19 May 2007 filament eruption, including the determined 3D trajectory of erupting filament, strong evidence for reconnection below erupting filament as consistent with standard model, and comparison of EUVI and H-alpha images during eruption; and results from stereoscopic analytic of 21 August 2007 filament eruption. Slide topics include standard model of filament eruption; 2007 May 19 STEREO A/SECCHI/EUVI 195 and 304 A: CME signatures and filament eruption, 3D reconstruction of erupting prominence; filament's relation to coronal magnetic fields; 3d reconstructions of filament eruption; height-time plot of eruption from 3D reconstructions; detailed pre-eruptions comparison of H-alpha and EUVI 304 at 12:42 UT; comparisons during the eruption; STEREO prominence and CME August 31, 2007; reconstructions of prominence and leading edges of both dark cavity and CME; and 3D reconstructions of prominence and leading edges.

HeLM: a macrophyte-based method for monitoring and assessment of Greek lakes.

PubMed

Zervas, Dimitrios; Tsiaoussi, Vasiliki; Tsiripidis, Ioannis

2018-05-05

The Water Framework Directive (WFD) requires Member States to develop appropriate assessment methods for the classification of the ecological status of their surface waters. Mediterranean region has lagged behind in this task, so we propose here the first developed method for Greek lakes, Hellenic Lake Macrophyte (HeLM) assessment method. This method is based on two metrics, a modified trophic index and maximum colonization depth C max that quantify the degree of changes in lake macrophytic vegetation, as a response to eutrophication and general degradation pressures. The method was developed on the basis of a data set sampled from 272 monitoring transects in 16 Greek lakes. Sites from three lakes were selected as potential reference sites by using a screening process. Ecological quality ratios were calculated for each metric and for each lake, and ecological status class boundaries were defined. For the evaluation of effectiveness of the method, the correlations between individual metrics and final HeLM values and common pressure indicators, such as total phosphorus, chlorophyll a and Secchi depth, were tested and found highly significant and relatively strong. In addition, the ability of HeLM values and its individual metrics to distinguish between different macrophytic communities' structure was checked using aquatic plant life-forms and found satisfactory. The HeLM method gave a reliable assessment of the macrophytic vegetation's condition in Greek lakes and may constitute a useful tool for the classification of ecological status of other Mediterranean lakes.

Galaxy Zoo: quantitative visual morphological classifications for 48 000 galaxies from CANDELS

NASA Astrophysics Data System (ADS)

Simmons, B. D.; Lintott, Chris; Willett, Kyle W.; Masters, Karen L.; Kartaltepe, Jeyhan S.; Häußler, Boris; Kaviraj, Sugata; Krawczyk, Coleman; Kruk, S. J.; McIntosh, Daniel H.; Smethurst, R. J.; Nichol, Robert C.; Scarlata, Claudia; Schawinski, Kevin; Conselice, Christopher J.; Almaini, Omar; Ferguson, Henry C.; Fortson, Lucy; Hartley, William; Kocevski, Dale; Koekemoer, Anton M.; Mortlock, Alice; Newman, Jeffrey A.; Bamford, Steven P.; Grogin, N. A.; Lucas, Ray A.; Hathi, Nimish P.; McGrath, Elizabeth; Peth, Michael; Pforr, Janine; Rizer, Zachary; Wuyts, Stijn; Barro, Guillermo; Bell, Eric F.; Castellano, Marco; Dahlen, Tomas; Dekel, Avishai; Ownsworth, Jamie; Faber, Sandra M.; Finkelstein, Steven L.; Fontana, Adriano; Galametz, Audrey; Grützbauch, Ruth; Koo, David; Lotz, Jennifer; Mobasher, Bahram; Mozena, Mark; Salvato, Mara; Wiklind, Tommy

2017-02-01

We present quantified visual morphologies of approximately 48 000 galaxies observed in three Hubble Space Telescope legacy fields by the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) and classified by participants in the Galaxy Zoo project. 90 per cent of galaxies have z ≤ 3 and are observed in rest-frame optical wavelengths by CANDELS. Each galaxy received an average of 40 independent classifications, which we combine into detailed morphological information on galaxy features such as clumpiness, bar instabilities, spiral structure, and merger and tidal signatures. We apply a consensus-based classifier weighting method that preserves classifier independence while effectively down-weighting significantly outlying classifications. After analysing the effect of varying image depth on reported classifications, we also provide depth-corrected classifications which both preserve the information in the deepest observations and also enable the use of classifications at comparable depths across the full survey. Comparing the Galaxy Zoo classifications to previous classifications of the same galaxies shows very good agreement; for some applications, the high number of independent classifications provided by Galaxy Zoo provides an advantage in selecting galaxies with a particular morphological profile, while in others the combination of Galaxy Zoo with other classifications is a more promising approach than using any one method alone. We combine the Galaxy Zoo classifications of `smooth' galaxies with parametric morphologies to select a sample of featureless discs at 1 ≤ z ≤ 3, which may represent a dynamically warmer progenitor population to the settled disc galaxies seen at later epochs.

CLADOCERAN BODY LENGTH AND ASSESSMENT OF SECCHI DISK TRANSPARENCY IN NORTHEASTERN U.S. LAKES. (R826591)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

On the uniqueness of motion of viscous gaseous stars

NASA Astrophysics Data System (ADS)

Secchi, Paolo

1990-11-01

The existence of solutions of the evolutionary equations of motion of a star regarded as a compressible viscous fluid with self-gravitation, bounded by a free surface, has recently been considered by Secchi (1990). In this paper, the uniqueness of the solutions cited is studied.

Characteristics of EUV Coronal Jets Observed with STEREO/SECCHI

NASA Astrophysics Data System (ADS)

Nisticò, G.; Bothmer, V.; Patsourakos, S.; Zimbardo, G.

2009-10-01

In this paper we present the first comprehensive statistical study of EUV coronal jets observed with the SECCHI (Sun Earth Connection Coronal and Heliospheric Investigation) imaging suites of the two STEREO spacecraft. A catalogue of 79 polar jets is presented, identified from simultaneous EUV and white-light coronagraph observations, taken during the time period March 2007 to April 2008, when solar activity was at a minimum. The twin spacecraft angular separation increased during this time interval from 2 to 48 degrees. The appearances of the coronal jets were always correlated with underlying small-scale chromospheric bright points. A basic characterization of the morphology and identification of the presence of helical structure were established with respect to recently proposed models for their origin and temporal evolution. Though each jet appeared morphologically similar in the coronagraph field of view, in the sense of a narrow collimated outward flow of matter, at the source region in the low corona the jet showed different characteristics, which may correspond to different magnetic structures. A classification of the events with respect to previous jet studies shows that amongst the 79 events there were 37 Eiffel tower-type jet events, commonly interpreted as a small-scale (˜35 arc sec) magnetic bipole reconnecting with the ambient unipolar open coronal magnetic fields at its loop tops, and 12 lambda-type jet events commonly interpreted as reconnection with the ambient field happening at the bipole footpoints. Five events were termed micro-CME-type jet events because they resembled the classical coronal mass ejections (CMEs) but on much smaller scales. The remaining 25 cases could not be uniquely classified. Thirty-one of the total number of events exhibited a helical magnetic field structure, indicative for a torsional motion of the jet around its axis of propagation. A few jets are also found in equatorial coronal holes. In this study we present sample events for each of the jet types using both, STEREO A and STEREO B, perspectives. The typical lifetimes in the SECCHI/EUVI ( Extreme UltraViolet Imager) field of view between 1.0 to 1.7 R ⊙ and in SECCHI/COR1 field of view between 1.4 to 4 R ⊙ are obtained, and the derived speeds are roughly estimated. In summary, the observations support the assumption of continuous small-scale reconnection as an intrinsic feature of the solar corona, with its role for the heating of the corona, particle acceleration, structuring and acceleration of the solar wind remaining to be explored in more detail in further studies.

Optic nerve head cupping in glaucomatous and non-glaucomatous optic neuropathy.

PubMed

Fard, Masoud Aghsaei; Moghimi, Sasan; Sahraian, Alireza; Ritch, Robert

2018-05-23

Enlargement of optic disc cupping is seen both in glaucoma and in neurological disorders. We used enhanced depth imaging with spectral-domain optical coherence tomography to differentiate glaucoma from non-glaucomatous optic neuropathy. The optic discs were scanned in this prospective comparative study, and the lamina cribrosa (LC) thickness and anterior laminar depth (ALD) in the central, superior and inferior optic nerve head, and peripapillary choroidal thicknesses, were measured. There were 31 eyes of 31 patients with severe glaucoma and 33 eyes of 19 patients with non-glaucomatous cupping. Eyes of 29 healthy controls were also enrolled. There was no significant difference in the cup-to-disc ratio and in the average peripapillary nerve fibre layer thickness between the glaucoma and non-glaucomatous cupping groups (p>0.99). The average peripapillary choroidal thickness was thinner in glaucoma eyes than in the control eyes after adjusting for age and axial length. Glaucomatous and non-glaucomatous eyes had greater ALD and thinner LC than the control eyes (p<0.001 for both). ALDs of glaucoma eyes were deeper than non-glaucomatous eyes (p=0.01 for central ALD) when age, axial length and peripapillary choroidal thickness were included in the linear mixed model. Prelaminar thickness and LC thickness of glaucoma eyes were not different from non-glaucomatous eyes after adjusting. Deeper ALD was observed in glaucoma than non-glaucomatous cupping after adjusting for choroidal thickness. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Experimental models for contamination of titanium surfaces and disinfection protocols.

PubMed

Sousa, Vanessa; Mardas, Nikos; Spratt, David; Boniface, David; Dard, Michel; Donos, Nikolaos

2016-10-01

The aim of this pilot study was to describe an in vitro model of peri-implantitis microcosm for contamination of titanium surfaces and an in vivo model for evaluating different disinfection strategies of titanium surfaces. Biofilms were grown in vitro for 30 days on sandblasted large-grit acid-etched (SLA) Ti discs (n = 69) in a constant depth film fermentor (CDFF) associated with peri-implantitis conditions. Four Swedish loop rabbits were randomly allocated in three test groups (T 1 , T 2 , T 3 ) and one control group (C). In group C, two sterile SLA Ti discs were implanted/fixed in each tibia. In the test groups (to evaluate the potential of different surface disinfection techniques), one sterile and three previously disinfected SLA Ti discs were placed following different disinfection protocols: group T 1 : the discs were treated with a titanium brush - TiB; group T 2 : the discs were treated with the combination of TiB and photodynamic therapy; and group T 3 : the discs were treated with TiB and 1%NaOCl plus 0.2%CHX. Tensile strength test and qualitative histological analysis were performed on all 16 discs after 4 weeks of healing. Thirty days following CDFF emulating peri-implantitis microcosm, all SLA Ti discs had a mean total viable aerobes and facultative anaerobes count of 8.06 log 10  CFU/biofilm and anaerobes 8.32 log 10  CFU/biofilm. Before implantation/fixation on the tibia, differences of log 10  CFU/biofilm counts between control and test groups after post hoc adjustment were highly significant (P < 0.001). In the in vivo analysis, group C exhibited the highest tensile strength (67.60 N [25.64-127.02]) and the histological sections revealed the presence of dense mature bone in direct contact with the disc surface. The analysis at the test groups showed that T 2 presented with the highest tensile strength in comparison with the other two test groups. The in vitro model used in this study provides a valuable and reproducible tool for evaluating the in vitro dynamics of the peri-implantitis microcosm biofilm and for contaminating in a reproducible manner titanium surfaces. At the same time, the in vivo model used in this study provides a standardised mode of evaluating disinfection modalities of previously infected titanium surfaces. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Abrupt transitions of the top-down controlled Black Sea pelagic ecosystem during 1960 2000: Evidence for regime-shifts under strong fishery exploitation and nutrient enrichment modulated by climate-induced variations

NASA Astrophysics Data System (ADS)

Oguz, Temel; Gilbert, Denis

2007-02-01

Functioning of the Black Sea ecosystem has profoundly changed since the early 1970s under cumulative effects of excessive nutrient enrichment, strong cooling/warming, over-exploitation of pelagic fish stocks, and population outbreak of gelatinous carnivores. Applying a set of criteria to the long-term (1960-2000) ecological time-series data, the present study demonstrates that the Black Sea ecosystem was reorganised during this transition phase in different forms of top-down controlled food web structure through successive regime-shifts of distinct ecological properties. The Secchi disc depth, oxic-anoxic interface zone, dissolved oxygen and hydrogen sulphide concentrations also exhibit abrupt transition between their alternate regimes, and indicate tight coupling between the lower trophic food web structure and the biogeochemical pump in terms of regime-shift events. The first shift, in 1973-1974, marks a switch from large predatory fish to small planktivore fish-controlled system, which persisted until 1989 in the form of increasing small pelagic and phytoplankton biomass and decreasing zooplankton biomass. The increase in phytoplankton biomass is further supported by a bottom-up contribution due to the cumulative response to high anthropogenic nutrient load and the concurrent shift of the physical system to the "cold climate regime" following its ˜20-year persistence in the "warm climate regime". The end of the 1980s signifies the depletion of small planktivores and the transition to a gelatinous carnivore-controlled system. By the end of the 1990s, small planktivore populations take over control of the system again. Concomitantly, their top-down pressure when combined with diminishing anthropogenic nutrient load and more limited nutrient supply into the surface waters due to stabilizing effects of relatively warm winter conditions switched the "high production" regime of phytoplankton to its background "low production" regime. The Black Sea regime-shifts appear to be sporadic events forced by strong transient decadal perturbations, and therefore differ from the multi-decadal scale cyclical events observed in pelagic ocean ecosystems under low-frequency climatic forcing. The Black Sea observations illustrate that eutrophication and extreme fishery exploitation can indeed induce hysteresis in large marine ecosystems, when they can exert sufficiently strong forcing onto the system. They further illustrate the link between the disruption of the top predators, proliferation of new predator stocks, and regime-shift events. Examples of these features have been reported for some aquatic ecosystems, but are extremely limited for large marine ecosystems.

The Effects of High Density on the X-ray Spectrum Reflected from Accretion Discs Around Black Holes

NASA Technical Reports Server (NTRS)

Garcia, Javier A.; Fabian, Andrew C.; Kallman, Timothy R.; Dauser, Thomas; Parker, Micahel L.; McClintock, Jeffrey E.; Steiner, James F.; Wilms, Jorn

2016-01-01

Current models of the spectrum of X-rays reflected from accretion discs around black holes and other compact objects are commonly calculated assuming that the density of the disc atmosphere is constant within several Thomson depths from the irradiated surface. An important simplifying assumption of these models is that the ionization structure of the gas is completely specified by a single, fixed value of the ionization parameter (xi), which is the ratio of the incident flux to the gas density. The density is typically fixed at n(sub e) = 10(exp 15) per cu cm. Motivated by observations, we consider higher densities in the calculation of the reflected spectrum. We show by computing model spectra for n(sub e) approximately greater than 10(exp 17) per cu cm that high-density effects significantly modify reflection spectra. The main effect is to boost the thermal continuum at energies 2 approximately less than keV. We discuss the implications of these results for interpreting observations of both active galactic nuclei and black hole binaries. We also discuss the limitations of our models imposed by the quality of the atomic data currently available.

Symposium P: Three-Dimensional Architectures for Energy Generation and Storage

DTIC Science & Technology

2010-09-02

anodic oxidation of aluminum to produce anodic aluminum oxide ( AAO ). The nanopores have diameters 15-100nm and depths 1-30um... aluminum oxide ( AAO ) template which can be successfully applied for fabrication of vertically aligned SiNWs. Then, we have investigated the electrical...performed in quiescent and rotating disc electrode (RDE) experiments. PSJfl Lateral Growth of Deep Nanopores in Anodic Aluminum Oxide as a Platform

Welding with the thin disc laser: new processing and application potentials

NASA Astrophysics Data System (ADS)

Hügel, H.; Ruβ, A.; Weberpals, J.; Dausinger, F.

2005-09-01

Thin disc lasers represent a new class of welding lasers in that they combine the beneficial characteristics of CO2- and Nd:YAG-lasers. Their good focusability--values of M2 around 20 are typical for devices in the multi kW power range--can be utilized in several ways to improve the welding performance: compared to lamp-pumped Nd:YAG-lasers, the laser power required at the threshold to the deep penetration regime can be reduced, the welding depth can be increased and far higher values of traverse speed are applicable at prescribed welding depths. Alternatively, the high beam quality allows the use of focusing optics with large focal lengths, hence enabling the realization of "remote welding" concepts. At the same time, a wavelength of 1.03 μm (Yb:YAG) provides, in comparison to CO2-lasers, a high absorptivity at metallic workpieces and a low sensitivity against plasma production; both effects contribute to the efficiency, stability and achievable quality of the welding process. Further, beam delivery via flexible glass fibers with core diameters of 100 μm to 150 μm is possible. With these features and an overall (plug) efficiency of more than 20 %, this laser offers a large potential for many applications.

Void fraction and velocity measurement of simulated bubble in a rotating disc using high frame rate neutron radiography.

PubMed

Saito, Y; Mishima, K; Matsubayashi, M

2004-10-01

To evaluate measurement error of local void fraction and velocity field in a gas-molten metal two-phase flow by high-frame-rate neutron radiography, experiments using a rotating stainless-steel disc, which has several holes of various diameters and depths simulating gas bubbles, were performed. Measured instantaneous void fraction and velocity field of the simulated bubbles were compared with the calculated values based on the rotating speed, the diameter and the depth of the holes as parameters and the measurement error was evaluated. The rotating speed was varied from 0 to 350 rpm (tangential velocity of the simulated bubbles from 0 to 1.5 m/s). The effect of shutter speed of the imaging system on the measurement error was also investigated. It was revealed from the Lagrangian time-averaged void fraction profile that the measurement error of the instantaneous void fraction depends mainly on the light-decay characteristics of the fluorescent converter. The measurement error of the instantaneous local void fraction of simulated bubbles is estimated to be 20%. In the present imaging system, the light-decay characteristics of the fluorescent converter affect the measurement remarkably, and so should be taken into account in estimating the measurement error of the local void fraction profile.

Drivers of change for lakewater clarity

Treesearch

Lawrence A. Baker; Johanna E. Schussler; Stephanie A. Snyder

2008-01-01

Lakes in the Upper Midwest have undergone extensive lakeshore development over the past 30 years, raising concerns about eutrophication. We examined 11 case study lakes in Minnesota that had undergone substantial shoreline development over the past 30 years to evaluate drivers of change in clarity. Relationships between current Secchi disk transparency (SDT) and the...

The Longitudinal Properties of a Solar Energetic Particle Event Investigated Using Modern Solar Imaging

DTIC Science & Technology

2012-06-10

and white light) and the longitudinal extent of the SEP event in the heliosphere. 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION...The STEREO SECCHI data are pro- duced by a consortium of RAL (UK), NRL (USA), LMSAL (USA), GSFC (USA), MPS (Germany), CSL (Belgium), IOTA (France

Sensitivity Monitoring of the SECCHI COR1 Telescopes on STEREO

NASA Astrophysics Data System (ADS)

Thompson, William T.

2018-03-01

Measurements of bright stars passing through the fields of view of the inner coronagraphs (COR1) on board the Solar Terrestrial Relations Observatory (STEREO) are used to monitor changes in the radiometric calibration over the course of the mission. Annual decline rates are found to be 0.648 ± 0.066%/year for COR1-A on STEREO Ahead and 0.258 ± 0.060%/year for COR1-B on STEREO Behind. These rates are consistent with decline rates found for other space-based coronagraphs in similar radiation environments. The theorized cause for the decline in sensitivity is darkening of the lenses and other optical elements due to exposure to high-energy solar particles and photons, although other causes are also possible. The total decline in the COR-B sensitivity when contact with Behind was lost on 1 October 2014 was 1.7%, while COR1-A was down by 4.4%. As of 1 November 2017, the COR1-A decline is estimated to be 6.4%. The SECCHI calibration routines will be updated to take these COR1 decline rates into account.

Data dependence for the amplitude equation of surface waves

NASA Astrophysics Data System (ADS)

Secchi, Paolo

2016-04-01

We consider the amplitude equation for nonlinear surface wave solutions of hyperbolic conservation laws. This is an asymptotic nonlocal, Hamiltonian evolution equation with quadratic nonlinearity. For example, this equation describes the propagation of nonlinear Rayleigh waves (Hamilton et al. in J Acoust Soc Am 97:891-897, 1995), surface waves on current-vortex sheets in incompressible MHD (Alì and Hunter in Q Appl Math 61(3):451-474, 2003; Alì et al. in Stud Appl Math 108(3):305-321, 2002) and on the incompressible plasma-vacuum interface (Secchi in Q Appl Math 73(4):711-737, 2015). The local-in-time existence of smooth solutions to the Cauchy problem for the amplitude equation in noncanonical variables was shown in Hunter (J Hyperbolic Differ Equ 3(2):247-267, 2006), Secchi (Q Appl Math 73(4):711-737, 2015). In the present paper we prove the continuous dependence in strong norm of solutions on the initial data. This completes the proof of the well-posedness of the problem in the classical sense of Hadamard.

The distribution of interstellar dust in CALIFA edge-on galaxies via oligochromatic radiative transfer fitting

NASA Astrophysics Data System (ADS)

De Geyter, Gert; Baes, Maarten; Camps, Peter; Fritz, Jacopo; De Looze, Ilse; Hughes, Thomas M.; Viaene, Sébastien; Gentile, Gianfranco

2014-06-01

We investigate the amount and spatial distribution of interstellar dust in edge-on spiral galaxies, using detailed radiative transfer modelling of a homogeneous sample of 12 galaxies selected from the Calar Alto Legacy Integral Field Area survey. Our automated fitting routine, FITSKIRT, was first validated against artificial data. This is done by simultaneously reproducing the Sloan Digital Sky Survey g-, r-, i- and z-band observations of a toy model in order to combine the information present in the different bands. We show that this combined, oligochromatic fitting has clear advantages over standard monochromatic fitting especially regarding constraints on the dust properties. We model all galaxies in our sample using a three-component model, consisting of a double-exponential disc to describe the stellar and dust discs and using a Sérsic profile to describe the central bulge. The full model contains 19 free parameters, and we are able to constrain all these parameters to a satisfactory level of accuracy without human intervention or strong boundary conditions. Apart from two galaxies, the entire sample can be accurately reproduced by our model. We find that the dust disc is about 75 per cent more extended but only half as high as the stellar disc. The average face-on optical depth in the V band is 0.76 and the spread of 0.60 within our sample is quite substantial, which indicates that some spiral galaxies are relatively opaque even when seen face-on.

A Survey of Submerged Aquatic Vegetation in Three Sub-arctic Lakes near Abisko, Sweden

NASA Astrophysics Data System (ADS)

Sampson, J.; Stilson, K.; Varner, R. K.; Crill, P. M.; Wik, M.; Crawford, M.

2014-12-01

We surveyed the submerged aquatic vegetation (SAV) in three sub-arctic lakes (Mellan Harrsjön, Inre Harrsjön, and Villasjön) located near Abisko in northern Sweden. Samples were collected using an extended rake, after which they were photographed and the plants identified. We also collected environmental data including temperature, dissolved oxygen, and secchi depth. Percent cover of SAV was taken twice using a 0.5 m. quadrat in shallow areas to track the changes in vegetation growth over time. In addition, we tested surface sediment samples for grain size and carbon, hydrogen, nitrogen, and sulfur composition. The percent cover of SAV in Mellan Harrsjön varied from 36%-49% and in Inre Harrsjön it averaged 19%. Across all three lakes, the average percent clay, silt, and sand was 3.8%, 50.1%, 46%, respectively. Because little research similar to this has been conducted in the area in such a comprehensive manner, these results are important to establish a baseline. Furthermore, these data will help establish how the SAV and environmental data may contribute to methane production and emission in these sub-arctic lakes.

Phytoplankton and nutrient dynamics in Winyah Bay, SC.

NASA Astrophysics Data System (ADS)

Boneillo, G. E.; Brooks, S. S.; Brown, S. L.; Woodford, K. M.; Wright, C. R.

2016-02-01

Winyah Bay is a coastal plain estuary located in South Carolina that has been classified for a moderate risk of Eutrophication by NOAA. Winyah Bay receives freshwater input from four rivers, the Waccamaw, Sampit, Black, and Pee Dee Rivers. The Waccamaw, Sampit and Black River are blackwater systems that discharge elevated amounts of colored dissolved organic matter. During the summer and fall of 2015, bioassay experiments were performed to simultaneously examine both light and nutrient (nitrogen & phosphate) limitation throughout Winyah Bay. Sampling stations near the mouth of the Waccamaw and Sampit Rivers showed that phytoplankton were light limited in the late summer instead of nutrient limited. These stations were located in the industrialized area of the bay and typically had the highest nutrient concentrations and highest turbidity, with Secchi depths typically less than 0.5 meters. Results indicated that phytoplankton may be nitrogen limited near the mouth of Winyah Bay, where nutrient concentrations and turbidity were observed to be lower than locations further upstream. There was also an observed dissolved oxygen and pH gradient during the summer of 2015. Dissolved oxygen levels less than 4.0 mg/L were routinely observed near the industrialized head of the estuary and corresponded with lower pH values.

Characterization of Lake Michigan coastal lakes using zooplankton assemblages

USGS Publications Warehouse

Whitman, Richard L.; Nevers, Meredith B.; Goodrich, Maria L.; Murphy, Paul C.; Davis, Bruce M.

2004-01-01

Zooplankton assemblages and water quality were examined bi-weekly from 17 April to 19 October 1998 in 11 northeastern Lake Michigan coastal lakes of similar origin but varied in trophic status and limnological condition. All lakes were within or adjacent to Sleeping Bear Dunes National Lakeshore, Michigan. Zooplankton (principally microcrustaceans and rotifers) from triplicate Wisconsin net (80 I?m) vertical tows taken at each lake's deepest location were analyzed. Oxygen-temperature-pH-specific conductivity profiles and surface water quality were concurrently measured. Bray-Curtis similarity analysis showed small variations among sample replicates but large temporal differences. The potential use of zooplankton communities for environmental lake comparisons was evaluated by means of BIOENV (Primer 5.1) and principal component analyses. Zooplankton analyzed at the lowest identified taxonomic level yielded greatest sensitivity to limnological variation. Taxonomic and ecological aggregations of zooplankton data performed comparably, but less well than the finest taxonomic analysis. Secchi depth, chlorophyll a, and sulfate concentrations combined to give the best correlation with patterns of variation in the zooplankton data set. Principal component analysis of these variables revealed trophic status as the most influential major limnological gradient among the study lakes. Overall, zooplankton abundance was an excellent indicator of variation in trophic status.

A method for estimating the diffuse attenuation coefficient (KdPAR)from paired temperature sensors

USGS Publications Warehouse

Read, Jordan S.; Rose, Kevin C.; Winslow, Luke A.; Read, Emily K.

2015-01-01

A new method for estimating the diffuse attenuation coefficient for photosynthetically active radiation (KdPAR) from paired temperature sensors was derived. We show that during cases where the attenuation of penetrating shortwave solar radiation is the dominant source of temperature changes, time series measurements of water temperatures at multiple depths (z1 and z2) are related to one another by a linear scaling factor (a). KdPAR can then be estimated by the simple equation KdPAR ln(a)/(z2/z1). A suggested workflow is presented that outlines procedures for calculating KdPAR according to this paired temperature sensor (PTS) method. This method is best suited for conditions when radiative temperature gains are large relative to physical noise. These conditions occur frequently on water bodies with low wind and/or high KdPARs but can be used for other types of lakes during time periods of low wind and/or where spatially redundant measurements of temperatures are available. The optimal vertical placement of temperature sensors according to a priori knowledge of KdPAR is also described. This information can be used to inform the design of future sensor deployments using the PTS method or for campaigns where characterizing sub-daily changes in temperatures is important. The PTS method provides a novel method to characterize light attenuation in aquatic ecosystems without expensive radiometric equipment or the user subjectivity inherent in Secchi depth measurements. This method also can enable the estimation of KdPAR at higher frequencies than many manual monitoring programs allow.

Aquatic ecosystem health and trophic status classification of the Bitter Lakes along the main connecting link between the Red Sea and the Mediterranean.

PubMed

El-Serehy, Hamed A; Abdallah, Hala S; Al-Misned, Fahad A; Irshad, Rizwan; Al-Farraj, Saleh A; Almalki, Esam S

2018-02-01

The Bitter Lakes are the most significant water bodies of the Suez Canal, comprising 85% of the water volume, but spreading over only 24% of the length of the canal. The present study aims at investigation of the trophic status of the Bitter Lakes employing various trophic state indices, biotic and abiotic parameters, thus reporting the health of the Lake ecosystem according to the internationally accepted classification criteria's. The composition and abundance of phytoplankton with a dominance of diatoms and a decreased population density of 4315-7376 ind. l -1 reflect the oligotrophic nature of this water body. The intense growth of diatoms in the Bitter Lakes depends on silicate availability, in addition to nitrate and phosphate. If the trophic state index (TSI) is applied to the lakes under study it records that the Bitter Lakes have an index under 40. Moreover, in the total chlorophyll- a measurements of 0.35-0.96 µg l -1 there are more indicative of little algal biomass and lower biological productivity. At 0.76-2.3 µg l -1 , meanwhile, the low quantity of Phosphorus is a further measure of low biological productivity. In the Bitter Lakes, TN/TP ratios are high and recorded 147.4, and 184.7 for minimum and maximum ratios, respectively. These values indicate that in Bitter lakes, the limiting nutrient is phosphorus and confirm the oligotrophic status of the Bitter Lakes. The latter conclusion is supported by Secchi disc water clarity measurements, showing that light can penetrate, and thus algae can photosynthesize, as deep as >13 m. This study, therefore, showed that the Bitter Lakes of the Suez Canal exhibit oligotrophic conditions with clear water, low productivity and with no algal blooming.

CME Research and Space Weather Support for the SECCHI Experiments on the STEREO Mission

DTIC Science & Technology

2014-01-14

Corbett, ed., Cambridge Univ. Press (2010) Kahler, S.W. and D. F. Webb, "Tracking Nonradial Motions and Azimuthal Expansions of Interplanetary CME...Imaging and In-situ Data from LASCO, STEREO and SMEI", Bull. AAS, 41(2), p. 855, 2009. Kahler S. and D. Webb, "Tracking Nonradial Motions and

Outer edges of debris discs. How sharp is sharp?

NASA Astrophysics Data System (ADS)

Thébault, P.; Wu, Y.

2008-04-01

Context: Rings or annulus-like features have been observed in most imaged debris discs. Outside the main ring, while some systems (e.g., β Pictoris and AU Mic) exhibit smooth surface brightness profiles (SB) that fall off roughly as ~r-3.5, others (e.g. HR 4796A and HD 139664) display large drops in luminosity at the ring's outer edge and steeper radial luminosity profiles. Aims: We seek to understand this diversity of outer edge profiles under the “natural” collisional evolution of the system, without invoking external agents such as planets or gas. Methods: We use a multi-annulus statistical code to follow the evolution of a collisional population, ranging in size from dust grains to planetesimals and initially confined within a belt (the “birth ring”). The crucial effect of radiation pressure on the dynamics and spatial distribution of the smallest grains is taken into account. We explore the dependence of the resulting disc surface brightness profile on various parameters. Results: The disc typically evolves toward a “standard” steady state, where the radial surface brightness profile smoothly decreases with radius as r-3.5 outside the birth ring. This confirms and extends the semi-analytical study of Strubbe & Chiang (2006, ApJ, 648, 652) and provides a firm basis for interpreting observed discs. Deviations from this typical profile, in the form of a sharp outer edge and a steeper fall-off, occur for two “extreme” cases: 1) when the birth ring is so massive that it becomes radially optically thick for the smallest grains. However, the required disc mass is probably too high here to be realistic; 2) when the dynamical excitation of the dust-producing planetesimals is so low (< e> and < i> ≤ 0.01) that the smallest grains, which otherwise dominate the optical depth of the system, are preferentially depleted. This low-excitation case, although possibly not generic, cannot be ruled out by observations for most systems, . Conclusions: Our “standard” profile provides a satisfactory explanation for a large group of debris discs that show smooth outer edges and SB ∝ r-3.5. Systems with sharper outer edges, barring other confining agents, could still be explained by “natural” collisional evolution if their dynamical excitation is very low. We show that such a dynamically-cold case provides a satisfactory fit to the specific HR4796A ring.

Water-quality assessment of Lakes Maumelle and Winona, Arkansas, 1991 through 2003

USGS Publications Warehouse

Galloway, Joel M.; Green, W. Reed

2004-01-01

Lakes Maumelle and Winona are water-supply reservoirs for the Little Rock and North Little Rock metropolitan areas in central Arkansas. In addition to water supply, the reservoirs are used for recreation and fish and wildlife habitat. The purpose of this report is to describe the hydrology and water quality of Lakes Maumelle and Winona and their inflows from data collected by the U.S. Geological Survey in cooperation with Central Arkansas Water for calendar years 1991 through 2003. The main inflows into Lakes Maumelle and Winona, the Maumelle River and Alum Fork Saline River, exhibited typical seasonal variability in streamflow with high flows usually occurring in the late fall, winter, and early spring, and low or no flow in the summer and early fall. The highest annual mean streamflow occurred in 1991 and the lowest annual mean streamflow occurred in 1992 for the Maumelle River and 1995 for the Alum Fork Saline River. Water quality measured in Lakes Maumelle and Winona varied spatially and temporally. Although total phosphorus concentrations were substantially higher at the upper ends of the lakes than at the lower ends of the lakes, nitrogen and orthophosphorus concentrations were not significantly different among the sampling sites on each lake. The highest concentrations of nitrogen generally were measured in 1991 and from 1998 through 2003 at all of the sampling sites. The highest total phosphorus concentrations were measured from 1994 to 1996 and from 1998 to 2001 on Lake Maumelle and from 1993 to 1994 on Lake Winona. Total and dissolved organic carbon concentrations were similar among sites on each lake and the greatest concentrations were measured in 1996 and 1997 at all of the sites. The chlorophyll a concentrations varied seasonally, with the highest concentrations in October and November, but were relatively uniform spatially and annually in Lakes Maumelle and Winona for 1991 through 2003. Water clarity was greater at the lower ends of the lakes than at the upper ends. Secchi depth varied seasonally, with the greatest depth from July to September and the least depth during October through December. There was no apparent trend in Secchi depth over the entire sampling period. The trophic state indices calculated from near-surface concentrations of total phosphorus and chlorophyll a for Lakes Maumelle and Winona indicated that they generally were oligotrophic although they fluctuated in time between mesotrophic and oligotrophic conditions. Water-quality concentrations generally were less for the main inflow to Lake Winona, the Alum Fork Saline River, than for the Maumelle River, Bringle, Yount, and Reece Creeks, which flow into Lake Maumelle. Nutrient concentrations for the Maumelle and Alum Fork Saline Rivers remained fairly uniform from 1991 through 2003. Suspended-sediment concentrations generally were greatest at Bringle Creek. Concentrations of fecal streptococci measured at the Alum Fork Saline River were similar to concentrations measured at the Maumelle River, and fecal coliforms concentrations for the Alum Fork Saline River were approximately half the concentration measured at the Maumelle River. Bringle and Reece Creeks had greater concentrations of fecal coliforms and fecal streptococci than the Maumelle River, and Yount Creek had the lowest concentration of fecal streptococci among all the sites. Annual loads of nutrients, dissolved organic carbon, and suspended sediment estimated for the Maumelle River and the Alum Fork Saline River were similar between sites and varied with time from 1991 through 2003. Annual loads were greatest in 1991 for the Maumelle and Alum Fork Saline Rivers and the least in 2000 for the Maumelle River and 1995 for the Alum Fork Saline River. Estimated loads also demonstrated seasonal trends with the highest daily loads in the winter and fall and lowest daily loads in the summer for both sites. Annual yields of nutrients and dissolved organic carbon computed

Poseidon's paintbox : historical archives of ocean colour in global-change perspective

NASA Astrophysics Data System (ADS)

Wernand, M. R.

2011-11-01

In the thesis introduction issues are discussed on the historical background of marine optics and on marine optical devices that were used over the past centuries to observe and measure; as in all sciences, in marine optics we can see a steady development: that of ‘measuring’, beginning many centuries ago, to 'knowing' and since less than a century to the understanding of the phenomenon. Hereafter, six themes are treated successively. The first theme, ‘Ocean optics from 1600 (Hudson) to 1930 (Raman), shift in interpretation of natural water colouring’, addresses the question of why it took so long a time to explain the phenomenon ‘the colouring of the sea’, especially the blue colour, despite the age-long interest of sailors, for practical purposes of navigation and detection of fish - of which more later. The second theme ‘On the history of the Secchi disc’, describes the search to establish methods for the determination of (sea) water clarity concerning purposes of navigation (near coast colour changes) just mentioned to detect shoals, and for a more basic purpose, tracing lost objects. The search to determine the clarity of lakes and seas culminated in the invention of the Secchi disc, used since the late 19th century. The third theme, ‘Spectral analysis of the Forel-Ule ocean colour comparator scale’, addresses the accuracy of a colour scale proposed, used in limnology and oceanography. Scale observations are put into perspective with contemporary measurements on the colour of the sea. The fourth theme, ‘Ocean colour changes in the North Pacific since 1930’, handles the question whether long-term ocean colour changes using historic Forel-Ule observations, in this part of the ocean made very frequently over time, can be determined in relation to global change. In principal global warming may cause a gradual change in ocean colour due to the effect of biological, chemical and physical aspects of the ocean-surface. The fifth theme, ‘MERIS-based ocean colour classification using the Forel-Ule scale’, addresses the question whether a relation can be established between the old Forel-Ule methodology, the classification of ocean colour by means of one of the scale colours, and the more recent satellite ocean colour methodology. The sixth theme, ‘Trends in ocean colour and chlorophyll concentration since 1889 to present’, addresses decadal colour changes per ocean and sea, using the longest available Forel-Ule dataset and confirms the possibility to transform these colour changes into chlorophyll concentration (indicative of the biomass of marine planktonic microalgae) changes. Such a transformation is needed to provide a link to the present in which chlorophyll concentrations are determined by using new technologies such as satellite remote sensing calibrated with high-performance liquid chromatography (HPLC) pigment analysis to determine marine microalgae pigments.

Water quality of the Chokosna, Gilahina, Lakina Rivers, and Long Lake watershed along McCarthy Road, Wrangell-St. Elias National Park and Preserve, Alaska, 2007-08

USGS Publications Warehouse

Brabets, Timothy P.; Ourso, Robert T.; Miller, Matthew P.; Brasher, Anne M. D.

2011-01-01

The Chokosna, Gilahina, and Lakina River basins, and the Long Lake watershed are located along McCarthy Road in Wrangell–St. Elias National Park and Preserve. The rivers and lake support a large run of sockeye (red) salmon that is important to the commercial and recreational fisheries in the larger Copper River. To gain a better understanding of the water quality conditions of these watersheds, these basins were studied as part of a cooperative study with the National Park Service during the open water periods in 2007 and 2008. Water type of the rivers and Long Lake is calcium bicarbonate with the exception of that in the Chokosna River, which is calcium bicarbonate sulfate water. Alkalinity concentrations ranged from 63 to 222 milligrams per liter, indicating a high buffering capacity in these waters. Analyses of streambed sediments indicated that concentrations of the trace elements arsenic, chromium, and nickel exceed levels that might be toxic to fish and other aquatic organisms. However, these concentrations reflect local geology rather than anthropogenic sources in this nearly pristine area. Benthic macroinvertebrate qualitative multi-habitat and richest targeted habitat samples collected from six stream sites along McCarthy Road indicated a total of 125 taxa. Insects made up the largest percentage of macroinvertebrates, totaling 83 percent of the families found. Dipterans (flies and midges) accounted for 43 percent of all macroinvertebrates found. Analysis of the macroinvertebrate data by non-metric multidimensional scaling indicated differences between (1) sites at Long Lake and other stream sites along McCarthy Road, likely due to different basin characteristics, (2) the 2007 and 2008 data, probably from the higher rainfall in 2008, and (3) macroinvertebrate data collected in south-central Alaska, which represents a different climate zone. The richness, abundance, and community composition of periphytic algae taxa was variable between sampling sites. Taxa richness and diversity were highest at the Long Lake outflow site, suggesting that the lake may have contributed planktonic taxa to the periphytic community and (or) created physical and chemical conditions at the outlet that were favorable to a variety of taxa. Long Lake is fed by groundwater and by clear water (non glacial) streams, resulting in relatively high Secchi-disc readings ranging from 17.5 to 23 feet. Depth profiles of water temperature in the lake show a strong stratification during the summer from the surface to about 13 feet, with temperatures ranging from 16 to 5 °C. Depth profiles of dissolved oxygen in the lake show a strong stratification between 26 and 33 feet, below which the concentrations of dissolved oxygen decrease from 10 to 2 milligrams per liter. Because the Long Lake outlet stream supports a large run of sockeye salmon and water temperature is an important factor during its life cycle, a logistic model was used to simulate 1998–2006 water temperatures at this site. Analysis of simulation results for 1998–2008 indicated no significant trends in water temperature. 2007 water temperatures were the highest during the 10-year period.

Water-quality data for the Ohio River from New Cumberland Dam to Pike Island Dam, West Virginia and Ohio, May-October 1993

USGS Publications Warehouse

Miller, K.F.; Messinger, Terence; Waldron, M.C.; Faulkenburg, C.W.

1996-01-01

This report contains water-quality data for the Ohio River from river mile 51.1 (3.3 miles upstream from New Cumberland Dam) to river mile 84.0 (0.2 miles upstream from Pike Island Dam) that were collected during the summer and fall of 1993. The data were collected to establish the water quality of the Ohio River and to use in assessing the proposed effects of hydropower development on the water quality of the Ohio River. Water quality was determined by a combination of repeated synoptic field measurements, continuous-record monitoring, and laboratory analyses. Synoptic measurements were made along a longitudinal transect with 18 mid-channel sampling sites; cross-sectional transects of water-quality measurements were made at 5 of these sites. Water-quality measurements also were made at two sites located on the back-channel (Ohio) side of Browns Island. At each longitudinal-transect and back-channel sampling site, measurements were made of specific conductance, pH, water temperature, and dissolved oxygen conentration. Longitudinal-transect and back-channel stations were sampled at four depths (at the surface, about 3.3 feet below the surface, middle of the water column, and near the bottom of the river). Cross-sectional transects consisted of three to four detailed vertical profiles of the same characteristics. Water samples were collected from three depths at the mid-channel vertical profile in each cross-sectional transect and were analyzed for concentrations of phytoplankton photosynthetic pigments chlorophyll a and chlorophyll b. Estimates of the depth of light penetration (Secchi-disk transparency) were made at pigment-sampling locations whenever light and river-surface conditions were appropriate. Synoptic sampling usually was completed in 12 hours or less and was repeated 10 times from May through October 1993. Continuous-record monitoring of water quality consisted of hourly measurements of specific conductance, pH, water temperature, and dissolved oxygen concentration, made at a depth of 6.6 feet upstream and downstream of New Cumberland Dam. Continuous monitors were operated from May through October 1993.

Water-quality data for the Ohio River from Willow Island Dam to Belleville Dam, West Virginia and Ohio, May-October 1993

USGS Publications Warehouse

Miller, K.F.

1996-01-01

This report contains water-quality data for the Ohio River from river mile 160.6 (1.1 mile upstream from Willow Island Dam) to river mile 203.6 (0.3 mile upstream from Belleville Dam) that were collected during the summer and fall of 1993. The data were collected to establish the water quality of the Ohio River and to use in assessing the proposed effects of hydropower development on the water quality of the Ohio River. Water quality was monitored by a combination of synoptic field measurements, laboratory analyses, and continuous- record monitoring. Field measurements of water- quality characteristics were made along a longitudinal transect with 24 mid-channel sampling sites; cross-sectional transects of water-quality measurements were made at six of these sites. Water-quality measurements also were made at six sites located on the back-channel (West Virginia) sides of Marietta, Muskingum, and Blennerhassett Islands. At each longitudinal-transect and back- channel sampling site, measurements of specific conductance, pH, water temperature, and dissolved oxygen concentration were made at three depths (about 3.3 feet below the surface of the water, middle of the water column, and near the bottom of the river). Cross-sectional transects consisted of three to four detailed vertical profiles of the same characteristics. Water samples were collected at three depths in the mid-channel vertical profile in each cross-sectional transect and were analyzed for concentrations of phytoplankton chlorophyll a and chlorophyll b. Estimates of the depth of light penetration (Secchi disk transparency) were made at phytoplankton- pigment-sampling locations whenever light and river-surface conditions were appropriate. Each synoptic sampling event was completed in 2 days or less. The entire network was sampled 10 times from May 24 to October 27, 1993. Continuous-record monitoring of water quality consisted of hourly measurments of specific conductance, pH, water temperature, and dissolved oxygen concentration that were made at a depth of 6.6 feet at the ends of the upstream and downstream wingwalls at Willow Island Dam. Continuous-record monitors were operated from May through October 1993.

High-Resolution Imaging of the Optic Nerve and Retina in Optic Nerve Hypoplasia

PubMed Central

Pilat, Anastasia; Sibley, Daniel; McLean, Rebecca J.; Proudlock, Frank A.; Gottlob, Irene

2015-01-01

Purpose To investigate the optic nerve and macular morphology in patients with optic nerve hypoplasia (ONH) using spectral-domain optical coherence tomography (SD OCT). Design Prospective, cross-sectional, observational study. Subjects A total of 16 participants with ONH (10 female and 6 male; mean age, 17.2 years; 6 bilateral involvement) and 32 gender-, age-, ethnicity-, and refraction-matched healthy controls. Methods High-resolution SD OCT (Copernicus [Optopol Technology S.A., Zawiercie, Poland], 3 μm resolution) and handheld SD OCT (Bioptigen Inc [Research Triangle Park, NC], 2.6 μm resolution) devices were used to acquire horizontal scans through the center of the optic disc and macula. Main Outcome Measures Horizontal optic disc/cup and rim diameters, cup depth, peripapillary retinal nerve fiber layer (RNFL), and thickness of individual retinal layers in participants with ONH and in controls. Results Patients with ONH had significantly smaller discs (P < 0.03 and P < 0.001 compared with unaffected eye and healthy controls, respectively), horizontal cup diameter (P < 0.02 for both), and cup depth (P < 0.02 and P < 0.01, respectively). In the macula, significantly thinner RNFL (nasally), ganglion cell layer (GCL) (nasally and temporally), inner plexiform layer (IPL) (nasally), outer nuclear layer (ONL) (nasally), and inner segment (centrally and temporally) were found in patients with ONH compared with the control group (P < 0.05 for all comparisons). Continuation of significantly thicker GCL, IPL, and outer plexiform layer in the central retinal area (i.e., foveal hypoplasia) was found in more than 80% of patients with ONH. Clinically unaffected fellow eyes of patients with ONH showed mild features of underdevelopment. Visual acuity and presence of septo-optic dysplasia were associated with changes in GCL and IPL. Sensitivity and specificity for the detection of ONH based on disc and retinal optical coherence tomography (OCT) parameters were >80%. Conclusions Our study provides evidence of retinal changes in ONH. In addition to thinning of retina layers mainly involving the RNFL and GCL, signs reminiscent of foveal hypoplasia were observed in patients with ONH. Optic nerve and foveal parameters measured using OCT showed high sensitivity and specificity for detecting ONH, demonstrating their useful for clinical diagnosis. PMID:25939636

Fluid pressure development beneath the décollement at the Nankai subduction zone: its implications for slow earthquakes

NASA Astrophysics Data System (ADS)

Hirose, T.; Kamiya, N.; Yamamoto, Y.; Heuer, V.; Inagaki, F.; Kubo, Y.

2017-12-01

Pore fluid pressure along a fault zone is very important for understanding earthquake generation processes in subduction zones. However, quantitative constraints on the pore pressure are quite limited. Here we report two estimates of the pore pressure developed within the underthrust sediments in the Nankai Trough off Cape Muroto, Japan, using the shipboard data obtained during IODP Expedition 370 (Heuer et al., 2017). First estimates are based on the depth trend of porosity data in the lower Shikoku Basin (LSB) facies, in which the décollement zone has propagated. Porosities in the LSB facies generally decrease with depth, but turn to increase by 5-7% below the décollement zone at 760 mbsf. Deeper than 830 mbsf, porosities resume a general compaction trend. By applying the method followed by Screaton et al. (2002) in which the downward porosity-increase is reflected by an excess pore pressure, we estimated the highest excess pore pressure of 4.2 MPa (λ* = 0.4: a ratio of excess pore pressure to effective overburden stress) at 1020 mbsf within the underthrust sediments. Another estimate is based on the analysis of upwelling drilling-mud flow from the borehole, which is a direct evidence the development of overpressure. We assumed that the borehole penetrated a disc-shaped high pore pressure zone with 10 m thickness and the steady-state flow. Then the pore pressure for a given radius of the disc-shaped zone, which is necessary for explaining the observed flow rate, was calculated using Darcy's law. The calculation yields that the pore pressure exceeded by 2-4 MPa above hydrostatic in case of the 10-13 m2 permeability and the 100-1000 m radius of the disc-shaped zone. Our analysis indicates a significant development of excess pore pressure beneath the décollement zone, most likely at the depth of 1020 mbsf where the highest overpressure was estimated from the downhole porosity trend and also an anomaly in relative hydrocarbon gas concentrations. Friction experiments by Sawai et al. (2016) show that a transition from stable to unstable slip behavior appears with increasing pore fluid pressure that is a prerequisite for the generation of slow earthquakes. Thus, slow earthquakes that occurred off Cape Muroto (Obara & Kato, 2016) can be attributed with the observed significant overpressure beneath the décollement.

Chlorophyll maxima in mountain ponds and lakes, Mount Rainier National Park, Washington State, USA

USGS Publications Warehouse

Larson, Gary L.

2000-01-01

Hypolimnetic chlorophyll maxima are common in clear lakes and often occur at depths with between 1 and 0.1% of the surface incident light. Little is known, however, about the concentrations of chlorophyll in thermally unstratified mountain ponds and how these concentrations compare to epilimnetic and hypolimnetic concentrations in mountain lakes. The objectives of this study were to document the concentrations of chlorophyll in thermally unstratified ponds and stratified lakes in Mount Rainier National Park (MORA) and to compare the results with concentrations and distributions of chlorophyll in clear-deep lakes in the Oregon Cascade Range and the Sierra Nevada Range. Thirty-two ponds (<2.5 m deep) and 14 lakes(>9.9 m deep) were sampled primarily during the summers of 1992 to 1996 at MORA. Water samples from near the surface (0.1–0.5 m) of ponds and near the surface and near the bottom of lakes were collected over the deepest part of each system. One exception, Mowich Lake, was sampled at seven depths between the surface and 50 m (Z=58.6 m). Chlorophyll concentrations were low in all systems, but higher in ponds (average 1.8 μg·L−1) than in lakes. Chlorophyll concentrations were higher in hypolimnetic lake samples (average 0.7 μg·L−1) than in epilimnetic lake samples (average 0.2 μg·L−1). Elevated concentrations of chlorophyll in mountain ponds, relative to those in hypolimnetic lake samples, may have been influenced by increased nutrient availability from interactions at the mud-water interface and, in this park, defecation by elk that used many of the ponds as wallows. Mowich Lake showed a chlorophyll maximum (~1.5 μg·L−1) near the lake bottom. Based on Secchi disk clarity readings, the depth of 1.0% incident surface solar radiation was greater than the maximum depths of the ponds and lakes. Comparative data from other clear-deep lakes in the Oregon Cascade Range and Sierra Nevada Range suggested that deep-chlorophyll maxima (~1.5 μg·L−1) occurred at <1.0% and > 0.1% of the incident surface solar radiation, and that the typical maximum depths ranged between 75 and 140 m during thermal stratification.

Mastering multi-depth bio-chip patterns with DVD LBRs

NASA Astrophysics Data System (ADS)

Carson, Doug

2017-08-01

Bio chip and bio disc are rapidly growing technologies used in medical, health and other industries. While there are numerous unique designs and features, these products all rely on precise three-dimensional micro-fluidic channels or arrays to move, separate and combine samples under test. These bio chip and bio disc consumables are typically manufactured by molding these parts to a precise three-dimensional pattern on a negative metal stamper, or they can be made in smaller quantities using an appropriate curable resin and a negative mold/stamper. Stampers required for bio chips have been traditionally made using either micro machining or XY stepping lithography. Both of these technologies have their advantages as well as limitations when it comes to creating micro-fluidic patterns. Significant breakthroughs in continuous maskless lithography have enabled accurate and efficient manufacturing of micro-fluidic masters using LBRs (Laser Beam Recorders) and DRIE (Deep Reactive Ion Etching). The important advantages of LBR continuous lithography vs. XY stepping lithography and micro machining are speed and cost. LBR based continuous lithography is >100x faster than XY stepping lithography and more accurate than micro machining. Several innovations were required in order to create multi-depth patterns with sub micron accuracy. By combining proven industrial LBRs with DCA's G3-VIA pattern generator and DRIE, three-dimensional bio chip masters and stampers are being manufactured efficiently and accurately.

Grinding damage assessment for CAD-CAM restorative materials.

PubMed

Curran, Philippe; Cattani-Lorente, Maria; Anselm Wiskott, H W; Durual, Stéphane; Scherrer, Susanne S

2017-03-01

To assess surface/subsurface damage after grinding with diamond discs on five CAD-CAM restorative materials and to estimate potential losses in strength based on crack size measurements of the generated damage. The materials tested were: Lithium disilicate (LIT) glass-ceramic (e.max CAD), leucite glass-ceramic (LEU) (Empress CAD), feldspar ceramic (VM2) (Vita Mark II), feldspar ceramic-resin infiltrated (EN) (Enamic) and a composite reinforced with nano ceramics (LU) (Lava Ultimate). Specimens were cut from CAD-CAM blocs and pair-wise mirror polished for the bonded interface technique. Top surfaces were ground with diamond discs of respectively 75, 54 and 18μm. Chip damage was measured on the bonded interface using SEM. Fracture mechanics relationships were used to estimate fracture stresses based on average and maximum chip depths assuming these to represent strength limiting flaws subjected to tension and to calculate potential losses in strength compared to manufacturer's data. Grinding with a 75μm diamond disc induced on a bonded interface critical chips averaging 100μm with a potential strength loss estimated between 33% and 54% for all three glass-ceramics (LIT, LEU, VM2). The softer materials EN and LU were little damage susceptible with chips averaging respectively 26μm and 17μm with no loss in strength. Grinding with 18μm diamond discs was still quite detrimental for LIT with average chip sizes of 43μm and a potential strength loss of 42%. It is essential to understand that when grinding glass-ceramics or feldspar ceramics with diamond discs surface and subsurface damage are induced which have the potential of lowering the strength of the ceramic. Careful polishing steps should be carried out after grinding especially when dealing with glass-ceramics. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Performance, Agility and Cost of Cloud Computing Services for NASA GES DISC Giovanni Application

NASA Astrophysics Data System (ADS)

Pham, L.; Chen, A.; Wharton, S.; Winter, E. L.; Lynnes, C.

2013-12-01

The NASA Goddard Earth Science Data and Information Services Center (GES DISC) is investigating the performance, agility and cost of Cloud computing for GES DISC applications. Giovanni (Geospatial Interactive Online Visualization ANd aNalysis Infrastructure), one of the core applications at the GES DISC for online climate-related Earth science data access, subsetting, analysis, visualization, and downloading, was used to evaluate the feasibility and effort of porting an application to the Amazon Cloud Services platform. The performance and the cost of running Giovanni on the Amazon Cloud were compared to similar parameters for the GES DISC local operational system. A Giovanni Time-Series analysis of aerosol absorption optical depth (388nm) from OMI (Ozone Monitoring Instrument)/Aura was selected for these comparisons. All required data were pre-cached in both the Cloud and local system to avoid data transfer delays. The 3-, 6-, 12-, and 24-month data were used for analysis on the Cloud and local system respectively, and the processing times for the analysis were used to evaluate system performance. To investigate application agility, Giovanni was installed and tested on multiple Cloud platforms. The cost of using a Cloud computing platform mainly consists of: computing, storage, data requests, and data transfer in/out. The Cloud computing cost is calculated based on the hourly rate, and the storage cost is calculated based on the rate of Gigabytes per month. Cost for incoming data transfer is free, and for data transfer out, the cost is based on the rate in Gigabytes. The costs for a local server system consist of buying hardware/software, system maintenance/updating, and operating cost. The results showed that the Cloud platform had a 38% better performance and cost 36% less than the local system. This investigation shows the potential of cloud computing to increase system performance and lower the overall cost of system management.

Three-Dimensional Properties of Coronal Mass Ejections from STEREO/SECCHI Observations

NASA Astrophysics Data System (ADS)

Bosman, E.; Bothmer, V.; Nisticò, G.; Vourlidas, A.; Howard, R. A.; Davies, J. A.

2012-11-01

We identify 565 coronal mass ejections (CMEs) between January 2007 and December 2010 in observations from the twin STEREO/SECCHI/COR2 coronagraphs aboard the STEREO mission. Our list is in full agreement with the corresponding SOHO/LASCO CME Catalog (http://cdaw.gsfc.nasa.gov/CME_list/) for events with angular widths of 45∘ and up. The monthly event rates behave similarly to sunspot rates showing a three- to fourfold rise between September 2009 and March 2010. We select 51 events with well-defined white-light structure and model them as three-dimensional (3D) flux ropes using a forward-modeling technique developed by Thernisien, Howard and Vourlidas (Astrophys. J. 652, 763 - 773, 2006). We derive their 3D properties and identify their source regions. We find that the majority of the CME flux ropes (82 %) lie within 30∘ of the solar equator. Also, 82 % of the events are displaced from their source region, to a lower latitude, by 25∘ or less. These findings provide strong support for the deflection of CMEs towards the solar equator reported in earlier observations, e.g. by Cremades and Bothmer ( Astron. Astrophys. 422, 307 - 322, 2004).

Physical, chemical, and biological characteristics of Pueblo Reservoir, Colorado, 1985-89

USGS Publications Warehouse

Lewis, Michael E.; Edelmann, Patrick

1994-01-01

Physical, chemical, and biological characteristics of Pueblo Reservoir are described on the basis of data collected from spring 1985 through fall 1989. Also included are discussions of water quality of the upper Arkansas River Basin and the reservoir as they relate to reservoir operations. Pueblo Reservoir is a multipurpose, main-stem reservoir on the Arkansas River about 6 miles west of Pueblo, Colorado. At the top of its conservation pool, the reservoir is more than 9 miles long and ranges in depth from a few feet at the inflow to about 155 feet at the dam. Pueblo Reservoir derives most of its contents from the Arkansas River, which comprises native and transmountain flow. With respect to water temperature, the reservoir typically was well mixed to weakly stratified during the early spring and gradually became strongly stratified by May. The strong thermal stratification and underflow of the Arkansas River generally persisted into August, at which time the reservoir surface began to cool and the reservoir subsequently underwent fall turnover. Following fall turnover, the reservoir was stratified to some degree in the shallow upstream part and well mixed in the deeper middle and downstream parts. Reservoir residence times were affected by the extent of stratification present. When the reservoir was well mixed, residence times were as long as several months. During the summer when the reservoir was strongly stratified, reservoir releases were large, and when underflow was the prevalent flow pattern of the Arkansas River, reservoir residence times were as short as 30 days.Most particulate matter settled from the water column between the inflow and a distance of about 5 miles downstream. On occasions of large streamflows and sediment loads from the Arkansas River, particulate matter was transported completely through the reservoir. Water transparency, as measured with a Secchi disk, increased in a downstream direction from the reservoir inflow. The increase probably was a result of sediment settling from the water column in the upstream part of the reservoir. Secchi-disk depths in December through April were larger than those in May through November. Secchi-disk depths were small between May through August as inflow sediment loads and reservoir biomass increased. In the fall, Secchi-disk depths remained small possibly as the result of resuspension of sediment and detritus within the water column. Dissolved-oxygen concentrations generally were near supersaturation near the reservoir surface. Dissolved-oxygen concentrations decreased with increasing depth. On several occasions during the summer, dissolved oxygen became completely depleted in the hypolimnion of the downstream part of the reservoir. The most extensive period of anoxia that was measured was in August 1988; the bottom 12 to 30 feet of the downstream end of the reservoir was anoxic. Fall turnover typically resulted in well-oxygenated conditions throughout the water column from September or October through the spring. Values of pH ranged from 7.5 to 9.0 and typically were largest near the surface and decreased with depth.Dissolved-solids concentrations in the reservoir primarily are affected by dissolved solids in the inflow from the Arkansas River. Concentrations are largest during periods of decreased streamflows, September through April, and decrease with increasing streamflows in May through August. The median dissolved-solids concentration increased from 224 milligrams per liter at the inflow to 262 milligrams per liter at the outflow. However, a statistical analysis of dissolved solids indicated the apparent increase in dissolved-solids concentrations between the inflow and outflow was not significant. Calcium, sulfate, and bicarbonate are the major dissolved ions in Pueblo Reservoir.Concentrations of the major nutrients, nitrogen and phosphorus, varied within the reservoir because of settling of particulate matter, uptake by phytoplankton near the reservoir surface, and releases from the reservoir bottom sediments. Phosphorus was indicated to be a potentially growth-limiting nutrient in the reservoir because of its relatively small concentrations. During 1986 and 1987, the reservoir retained about 35 percent (359 tons) of the total nitrogen load and about 83 percent (203 tons) of the total phosphorus load. Settling of particulate matter from the water column and uptake by phytoplankton are the major nutrient sinks in the reservoir.Barium, iron, manganese, and zinc were the major trace elements in Pueblo Reservoir. Traceelement concentrations in the reservoir varied because of seasonality of trace-element concentrations in the Arkansas River, settling of particulate matter, and flux of trace elements from the bottom sediments. The aquatic-life standard in Pueblo Reservoir for total-recoverable iron (1,000 micrograms per liter) and the public water-supply standard for dissolved manganese (50 micrograms per liter) were exceeded on several occasions during the summer. Elevated concentrations of totalrecoverable iron and dissolved manganese in the Arkansas River during summer runoff contributed to exceedances in the upper part of the reservoir. Flux of manganese from the reservoir bottom sediments during periods of low or depleted dissolved-oxygen concentrations contributed to exceedances in the deeper, downstream parts of the reservoir. Concentrations of lead, mercury, and zinc were elevated in the reservoir bottom sediments and may be the result of metal-mine drainage in the upper Arkansas River Basin. Median concentrations of total organic carbon ranged from 3.1 to 4.5 milligrams per liter in May through September and from 2.5 to 3.5 milligrams per liter in October through April. Totalorganic-carbon concentrations in the reservoir were largest in the summer when streamflows and total-organic-carbon concentrations are largest in the Arkansas River. Total-organic-carbon concentrations in the reservoir decrease downstream from the reservoir inflow because of settling of particulate organic carbon. Levels of gross-alpha and gross-beta radioactivity generally were relatively low. In 7 of 31 samples collected, dissolved gross-alpha radioactivity, as natural uranium, exceeded 5 picocuries per liter, the level at which additional radiochemical analyses are recommended for drinking-water supplies. Potential sources of uranium in Pueblo Reservoir include weathering of exposed uranium ore deposits in the upper Arkansas River Basin and a uranium milling operation near Canon City.Phytoplankton densities and biovolumes measured during the winter, spring, and fall generally were indicative of a small to moderate algal biomass. Phytoplankton production tended to be largest during the summer. During the summer, phytoplankton densities and biovolumes generally were indicative of a moderate to large algal biomass. However, excessive algal production and biomass periodically occurred during the spring, summer, and fall. Three species of phytoplankton that are specifically associated with taste-and-odor problems in drinking water were identified on several occasions in water samples collected from Pueblo Reservoir. Reservoir operations and hydrodynamics can substantially affect processes that affect reservoir water quality. Stratification, underflow, and hypolimnetic withdrawals affect concentrations of dissolved solids, availability of nutrients, and concentrations of metals in the reservoir. Stratification impedes the mixing of epilimnetic and hypolimnetic waters, and the prevalent underflow that occurs during the summer results in a decrease in the potential dilution of inflowing river water with reservoir water. The underflow also decreases the maximum available nutrient load to the euphotic zone, which can, in turn, offset the maximum algal growth potential. Increased dissolved-solids, nutrient, and metal concentrations that occur in the hypolimnion during the summer are partially offset by hypolimnetic withdrawals.

Water quality, hydrology, and simulated response to changes in phosphorus loading of Mercer Lake, Iron County, Wisconsin, with special emphasis on the effects of wastewater discharges

USGS Publications Warehouse

Robertson, Dale M.; Garn, Herbert S.; Rose, William J.; Juckem, Paul F.; Reneau, Paul C.

2012-01-01

Mercer Lake is a relatively shallow drainage lake in north-central Wisconsin. The area near the lake has gone through many changes over the past century, including urbanization and industrial development. To try to improve the water quality of the lake, actions have been taken, such as removal of the lumber mill and diversion of all effluent from the sewage treatment plant away from the lake; however, it is uncertain how these actions have affected water quality. Mercer Lake area residents and authorities would like to continue to try to improve the water quality of the lake; however, they would like to place their efforts in the actions that will have the most beneficial effects. To provide a better understanding of the factors affecting the water quality of Mercer Lake, a detailed study of the lake and its watershed was conducted by the U.S. Geological Survey in collaboration with the Mercer Lake Association. The purposes of the study were to describe the water quality of the lake and the composition of its sediments; quantify the sources of water and phosphorus loading to the lake, including sources associated with wastewater discharges; and evaluate the effects of past and future changes in phosphorus inputs on the water quality of the lake using eutrophication models (models that simulate changes in phosphorus and algae concentrations and water clarity in the lake). Based on analyses of sediment cores and monitoring data collected from the lake, the water quality of Mercer Lake appears to have degraded as a result of the activities in its watershed over the past 100 years. The water quality appears to have improved, however, since a sewage treatment plant was constructed in 1965 and its effluent was routed away from the lake in 1995. Since 2000, when a more consistent monitoring program began, the water quality of the lake appears to have changed very little. During the two monitoring years (MY) 2008-09, the average summer near-surface concentration of total phosphorus was 0.023 mg/L, indicating the lake is borderline mesotrophic-eutrophic, or has moderate to high concentrations of phosphorus, whereas the average summer chlorophyll a concentration was 3.3 mg/L and water clarity, as measured with a Secchi depth, was 10.4 ft, both indicating mesotrophic conditions or that the lake has a moderate amount of algae and water clarity. Although actions have been taken to eliminate the wastewater discharges, the bottom sediment still has slightly elevated concentrations of several pollutants from wastewater discharges, lumber operations, and roadway drainage, and a few naturally occurring metals (such as iron). None of the concentrations, however, were high enough above the defined thresholds to be of concern. Based on nitrogen to phosphorus ratios, the productivity (algal growth) in Mercer Lake should typically be limited by phosphorus; therefore, understanding the phosphorus input to the lake is important when management efforts to improve or prevent degradation of the lake water quality are considered. Total inputs of phosphorus to Mercer Lake were directly estimated for MY 2008-09 at about 340 lb/yr and for a recent year with more typical hydrology at about 475 lb/yr. During these years, the largest sources of phosphorus were from Little Turtle Inlet, which contributed about 45 percent, and the drainage area near the lake containing the adjacent urban and residential developments, which contributed about 24 percent. Prior to 1965, when there was no sewage treatment plant and septic systems and other untreated systems contributed nutrients to the watershed, phosphorus loadings were estimated to be about 71 percent higher than during around 2009. In 1965, a sewage treatment plant was built, but its effluent was released in the downstream end of the lake. Depending on various assumptions on how much effluent was retained in the lake, phosphorus inputs from wastewater may have ranged from 0 to 342 lb. Future highway and stormwater improvements have been identified in the Mercer Infrastructure Improvement Project, and if they are done with the proposed best management practices, then phosphorus inputs to the lake may decrease by about 40 lb. Eutrophication models [Canfield and Bachman model (1981) and Carlson Trophic State Index equations (1977)] were used to predict how the water quality of Mercer Lake should respond to changes in phosphorus loading. A relatively linear response was found between phosphorus loading and phosphorus and chlorophyll a concentrations in the lake, with changes in phosphorus concentrations being slightly less (about 80 percent) and changes in chlorophyll a concentrations being slightly more (about 120 percent) than the changes in phosphorus loadings to the lake. Water clarity, indicated by Secchi depths, responded more to decreases in phosphorus loading than to increases in loading. Results from the eutrophication models indicated that the lake should have been negatively affected by the wastewater discharges. Prior to 1965, when there was no sewage treatment plant effluent and inputs from the septic systems and other untreated systems were thought to be high, the lake should have been eutrophic; near the surface, average phosphorus concentrations were almost 0.035 mg/L, chlorophyll a concentrations were about 7 μg/L, and Secchi depths were about 6 ft, which agreed with the shallower Secchi depths during this time estimated from the sediment-core analysis. The models indicated that between 1965 and 1995, when the lake retained some of the effluent from the new sewage treatment plant, water quality should have been between the conditions estimated prior to 1965 and what was expected during typical hydrologic conditions around MY 2008-09. The models also indicated that if the future Mercer Infrastructure Improvement Project is conducted with the best management practices as proposed, the water quality in the lake could improve slightly from that measured during 2006-10. Because of the small amount of phosphorus that is presently input into Mercer Lake any additional phosphorus added to the lake could degrade water quality; therefore, management actions can usefully focus on minimizing future phosphorus inputs. Phosphorus released from the sediments of a degraded lake often delays its response to decreases in external phosphorus loading, especially in shallow, frequently mixed systems. Mercer Lake, however, remains stratified throughout most of the summer, and phosphorus released from the sediments represents only about 6 percent, or a small fraction, of the total phosphorus load to the lake. Therefore, the phosphorus trapped in the sediments should minimally affect the long-term water quality of the lake and should not delay the response in its productivity to future changes in nutrient loading from its watershed.

Developing Predictive Models for Algal Bloom Occurrence and Identifying Factors Controlling their Occurrence in the Charlotte County and Surroundings

NASA Astrophysics Data System (ADS)

Karki, S.; Sultan, M.; Elkadiri, R.; Chouinard, K.

2017-12-01

Numerous occurrences of harmful algal blooms (Karenia Brevis) were reported from Southwest Florida along the coast of Charlotte County, Florida. We are developing data-driven (remote sensing, field, and meteorological data) models to accomplish the following: (1) identify the factors controlling bloom development, (2) forecast bloom occurrences, and (3) make recommendations for monitoring variables that are found to be most indicative of algal bloom occurrences and for identifying optimum locations for monitoring stations. To accomplish these three tasks we completed/are working on the following steps. Firstly, we developed an automatic system for downloading and processing of ocean color data acquired through MODIS Terra and MODIS Aqua products using SeaDAS ocean color processing software. Examples of extracted variables include: chlorophyll a (OC3M), chlorophyll a Generalized Inherent Optical Property (GIOP), chlorophyll a Garver-Siegel- Maritorena (GSM), sea surface temperature (SST), Secchi disk depth, euphotic depth, turbidity index, wind direction and speed, colored dissolved organic material (CDOM). Secondly we are developing a GIS database and a web-based GIS to host the generated remote sensing-based products in addition to relevant meteorological and field data. Examples of the meteorological and field inputs include: precipitation amount and rates, concentrations of nitrogen, phosphorous, fecal coliform and Dissolved Oxygen (DO). Thirdly, we are constructing and validating a multivariate regression model and an artificial neural network model to simulate past algal bloom occurrences using the compiled archival remote sensing, meteorological, and field data. The validated model will then be used to predict the timing and location of algal bloom occurrences. The developed system, upon completion, could enhance the decision making process, improve the citizen's quality of life, and strengthen the local economy.

Coordinated aircraft and ship surveys for determining impact of river inputs on great lakes waters. Remote sensing results

NASA Technical Reports Server (NTRS)

Raquet, C. A.; Salzman, J. A.; Coney, T. A.; Svehla, R. A.; Shook, D. F.; Gedney, R. T.

1980-01-01

The remote sensing results of aircraft and ship surveys for determining the impact of river effluents on Great Lakes waters are presented. Aircraft multi-spectral scanner data were acquired throughout the spring and early summer of 1976 at five locations: the West Basin of Lake Erie, Genesee River - Lake Ontario, Menomonee River - Lake Michigan, Grand River - Lake Michigan, and Nemadji River - Lake Superior. Multispectral scanner data and ship surface sample data are correlated resulting in 40 contour plots showing large-scale distributions of parameters such as total suspended solids, turbidity, Secchi depth, nutrients, salts, and dissolved oxygen. The imagery and data analysis are used to determine the transport and dispersion of materials from the river discharges, especially during spring runoff events, and to evaluate the relative effects of river input, resuspension, and shore erosion. Twenty-five LANDSAT satellite images of the study sites are also included in the analysis. Examples of the use of remote sensing data in quantitatively estimating total particulate loading in determining water types, in assessing transport across international boundaries, and in supporting numerical current modeling are included. The importance of coordination of aircraft and ship lake surveys is discussed, including the use of telefacsimile for the transmission of imagery.

Integration of remote sensing and geographic information systems for Great Lakes water quality monitoring

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lathrop, R.G. Jr.

1988-01-01

The utility of three operational satellite remote sensing systems, namely, the Landsat Thematic Mapper (TM), the SPOT High Resolution Visible (HRV) sensors and the NOAA Advanced Very High Resolution Radiometer (AVHRR), were evaluated as a means of estimating water quality and surface temperature. Empirical calibration through linear regression techniques was used to relate near-simultaneously acquired satellite radiance/reflectance data and water quality observations obtained in Green Bay and the nearshore waters of Lake Michigan. Four dates of TM and one date each of SPOT and AVHRR imagery/surface reference data were acquired and analyzed. Highly significant relationships were identified between the TMmore » and SPOT data and secchi disk depth, nephelometric turbidity, chlorophyll a, total suspended solids (TSS), absorbance, and surface temperature (TM only). The AVHRR data were not analyzed independently but were used for comparison with the TM data. Calibrated water quality image maps were input to a PC-based raster GIS package, EPPL7. Pattern interpretation and spatial analysis techniques were used to document the circulation dynamics and model mixing processes in Green Bay. A GIS facilitates the retrieval, query and spatial analysis of mapped information and provides the framework for an integrated operational monitoring system for the Great Lakes.« less

The effects of grazers and light penetration on the survival of transplants of Vallisneria americana Michs in the tidal Potomac River, Maryland

USGS Publications Warehouse

Carter, V.; Rybicki, N.B.

1985-01-01

Poor light penetration and grazing are among the factors potentially responsible for the lack of submersed aquatic macrophytes in the tidal Potomac River. Between 1980 and 1983, plugs, springs and tubers of Vallisneria americana Michx were transplanted from the oligohaline Potomac Estuary to six sites in the freshwater tidal Potomac River. Transplants made in 1980 and 1981 were generally successful only when protected by full exclosures which prevented grazing. Grazing resulted in the removal of whole plants or clipping off of plant leaves in unprotected plots. Plants protected in the first year were permanently established, despite the occurrence of grazing in subsequent years, at Elodea Cove and Rosier Bluff, where light penetration was high (average 1% light level was 1.6-1.7 m). Plants were not permanent;y established at Goose Island, where light penetration was lower (average 1% light level was 1.4 m) and grazing occurred, or Neabsco Bay where light penetration was very low (average 1% light level was 1.0 m) and grazing may not have occurred. In 1983, Secchi depth transparencies in the upper tidal river were improved significantly compared to 1978-1981. Both protected and unprotected transplants thrived in 1983. ?? 1985.

The Sun in STEREO

NASA Technical Reports Server (NTRS)

2006-01-01

Parallax gives depth to life. Simultaneous viewing from slightly different vantage points makes binocular humans superior to monocular cyclopes, and fixes us in the third dimension of the Universe. We've been stunned by 3-d images of Venus and Mars (along with more familiar views of earth). Now astronomers plan to give us the best view of all, 3-d images of the dynamic Sun. That's one of the prime goals of NASA's Solar Terrestrial Relations Observatories, also known as STEREO. STEREO is a pair of spacecraft observatories, one placed in orbit in front of earth, and one to be placed in an earth-trailing orbit. Simultaneous observations of the Sun with the two STEREO spacecraft will provide extraordinary 3-d views of all types of solar activity, especially the dramatic events called coronal mass ejections which send high energy particles from the outer solar atmosphere hurtling towards earth. The image above the first image of the sun by the two STEREO spacecraft, an extreme ultraviolet shot of the Sun's million-degree corona, taken by the Extreme Ultraviolet Imager on the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) instrument package. STEREO's first 3-d solar images should be available in April if all goes well. Put on your red and blue glasses!

Nitrogen and the Baltic Sea: managing nitrogen in relation to phosphorus.

PubMed

Elmgren, R; Larsson, U

2001-10-26

The Baltic is a large, brackish sea (4 x 10(5) km2) extending from 54N to approximately 66N, with a fourfold larger drainage area (population 8 x 10(7). Surface salinity (2 to 8 PSU) and hence biodiversity is low. In the last century, annual nutrient loads increased to 10(6) metric tons N and 5 x 10(4) ton P. Eutrophication is evident in the N-limited south, where cyanobacteria fix 2 to 4 x 10(5) ton N each summer, Secchi depths have been halved, and O2-deficient bottom areas have spread. Production remains low in the P-limited north. In nutrient-enriched coastal areas, phytoplankton blooms, toxic at times, and filamentous macroalgae reduce amenity values. Loads need to be reduced of both N, to reduce production, and P, to limit N-fixing cyanobacterial blooms. When large N-load reductions have been achieved locally, algal biomass has declined. So far, P loads have been reduced more than N loads. If this continues, a P-limited Baltic proper may result, very different from previous N-limited conditions. Reaching the management goal of halved anthropogenic N and P loads at minimum cost will require better understanding of biogeochemical nutrient cycles, economic evaluation of proposed measures, and improved stakeholder participation.

Assessment of the Eutrophication-Related Environmental Parameters in Two Mediterranean Lakes by Integrating Statistical Techniques and Self-Organizing Maps.

PubMed

Hadjisolomou, Ekaterini; Stefanidis, Konstantinos; Papatheodorou, George; Papastergiadou, Evanthia

2018-03-19

During the last decades, Mediterranean freshwater ecosystems, especially lakes, have been under severe pressure due to increasing eutrophication and water quality deterioration. In this article, we compared the effectiveness of different data analysis methods by assessing the contribution of environmental parameters to eutrophication processes. For this purpose, principal components analysis (PCA), cluster analysis, and a self-organizing map (SOM) were applied, using water quality data from two transboundary lakes of North Greece. SOM is considered as an advanced and powerful data analysis tool because of its ability to represent complex and nonlinear relationships among multivariate data sets. The results of PCA and cluster analysis agreed with the SOM results, although the latter provided more information because of the visualization abilities regarding the parameters' relationships. Besides nutrients that were found to be a key factor for controlling chlorophyll-a (Chl - a), water temperature was related positively with algal production, while the Secchi disk depth parameter was found to be highly important and negatively related toeutrophic conditions. In general, the SOM results were more specific and allowed direct associations between the water quality variables. Our work showed that SOMs can be used effectively in limnological studies to produce robust and interpretable results, aiding scientists and managers to cope with environmental problems such as eutrophication.

Aquatic vegetation in response to increased eutrophication and degraded light climate in Eastern Lake Taihu: Implications for lake ecological restoration.

PubMed

Zhang, Yunlin; Liu, Xiaohan; Qin, Boqiang; Shi, Kun; Deng, Jianming; Zhou, Yongqiang

2016-04-04

Terrestrial and aquatic ecosystem degradation is widely recognized as a major global environmental and development problem. Although great efforts have been made to prevent aquatic ecosystem degradation, the degree, extent and impacts of this phenomenon remain controversial and unclear, such as its driving mechanisms. Here, we present results from a 17-year field investigation (1998-2014) of water quality and a 12-year remote sensing mapping (2003-2014) of the aquatic vegetation presence frequency (VPF) in Eastern Lake Taihu, a macrophyte-dominated bay of Lake Taihu in China. In the past 17 years, nutrient concentrations and water level (WL) have significantly increased, but the Secchi disk depth (SDD) has significantly decreased. These changes were associated with increased lake eutrophication and a degraded underwater light climate that further inhibited the growth of aquatic vegetation. In Eastern Lake Taihu, increased nutrients, chlorophyll a and WL, and a decreased SDD were all significantly correlated with a decreased VPF. NH4(+)-N concentration and SDD/WL were the most important controlling factors for VPF. Therefore, increased anthropogenic nutrient inputs and a degraded underwater light climate surely result in a decreased VPF. These results elucidate the driving mechanism of aquatic vegetation degradation and will facilitate Lake Taihu ecological restoration.

Aquatic vegetation in response to increased eutrophication and degraded light climate in Eastern Lake Taihu: Implications for lake ecological restoration

NASA Astrophysics Data System (ADS)

Zhang, Yunlin; Liu, Xiaohan; Qin, Boqiang; Shi, Kun; Deng, Jianming; Zhou, Yongqiang

2016-04-01

Terrestrial and aquatic ecosystem degradation is widely recognized as a major global environmental and development problem. Although great efforts have been made to prevent aquatic ecosystem degradation, the degree, extent and impacts of this phenomenon remain controversial and unclear, such as its driving mechanisms. Here, we present results from a 17-year field investigation (1998-2014) of water quality and a 12-year remote sensing mapping (2003-2014) of the aquatic vegetation presence frequency (VPF) in Eastern Lake Taihu, a macrophyte-dominated bay of Lake Taihu in China. In the past 17 years, nutrient concentrations and water level (WL) have significantly increased, but the Secchi disk depth (SDD) has significantly decreased. These changes were associated with increased lake eutrophication and a degraded underwater light climate that further inhibited the growth of aquatic vegetation. In Eastern Lake Taihu, increased nutrients, chlorophyll a and WL, and a decreased SDD were all significantly correlated with a decreased VPF. NH4+-N concentration and SDD/WL were the most important controlling factors for VPF. Therefore, increased anthropogenic nutrient inputs and a degraded underwater light climate surely result in a decreased VPF. These results elucidate the driving mechanism of aquatic vegetation degradation and will facilitate Lake Taihu ecological restoration.

Occurrence and Characteristics of Microplastic Pollution in Xiangxi Bay of Three Gorges Reservoir, China.

PubMed

Zhang, Kai; Xiong, Xiong; Hu, Hongjuan; Wu, Chenxi; Bi, Yonghong; Wu, Yonghong; Zhou, Bingsheng; Lam, Paul K S; Liu, Jiantong

2017-04-04

Microplastic pollution in inland waters is receiving growing attentions. Reservoirs are suspected to be particularly vulnerable to microplastic pollution. However, very limited information is currently available on pollution characteristics of microplastics in reservoir ecosystems. This work studied the distribution and characteristics of microplastics in the backwater area of Xiangxi River, a typical tributary of the Three Gorges Reservoir. Microplastics were detected in both surface water and sediment with concentrations ranging from 0.55 × 10 5 to 342 × 10 5 items km -2 and 80 to 864 items m -2 , respectively. Polyethylene, polypropylene, and polystyrene were identified in surface water, whereas polyethylene, polypropylene, and polyethylene terephthalate, and pigments were observed in sediment. In addition, microplastics were also detected in the digestion tracts of 25.7% of fish samples, and polyethylene and nylon were identified. Redundancy analysis indicates a weak correlation between microplastics and water quality variables but a negative correlation with water level of the reservoir and Secchi depth. Results from this study confirm the presence of high abundance microplastics in reservoir impacted tributaries, and suggest that water level regulated hydrodynamic condition and input of nonpoint sources are important regulators for microplastic accumulation and distribution in the backwater area of reservoir tributaries.

LANDSAT/coastal processes

NASA Technical Reports Server (NTRS)

James, W. P. (Principal Investigator); Hill, J. M.; Bright, J. B.

1977-01-01

The author has identified the following significant results. Correlations between the satellite radiance values water color, Secchi disk visibility, turbidity, and attenuation coefficients were generally good. The residual was due to several factors including systematic errors in the remotely sensed data, errors, small time and space variations in the water quality measurements, and errors caused by experimental design. Satellite radiance values were closely correlated with the optical properties of the water.

2014 status of the Lake Ontario lower trophic levels

USGS Publications Warehouse

Holeck, Kristen T.; Rudstam, Lars G.; Hotaling, Christopher; McCullough, Russ D.; Lemon, Dave; Pearsall, Web; Lantry, Jana; Connerton, Michael J.; LaPan, Steve; Biesinger, Zy; Lantry, Brian F.; Walsh, Maureen; Weidel, Brian C.

2015-01-01

Soluble reactive phosphorus (SRP) concentrations have been stable in nearshore and offshore habitats since 1998 (0.4 – 3.3 μg/L). SRP concentrations were low in 2014; Apr/May – Oct mean values were <1 μg/L at most sites. Spring TP concentrations at individual sites exceeded 10 μg/L on occasion, but spring means were below the 10 μg/L target set by the Great Lakes Water Quality Agreement of 1978 for offshore waters of Lake Ontario. TP concentrations were low at both nearshore and offshore locations; Apr/May – Oct mean values from individual sites ranged from 4.6 – 9.1 μg/L. Spring TP has declined significantly in the longer data series (since 1981), but not since 1995 indicating stable nutrient loading into Lake Ontario for nearly two decades. It averaged 7.8 μg/L in the nearshore and 5.6 μg/L in the offshore in 2014.Chlorophyll-a and secchi depth values are indicative of oligotrophic conditions in nearshore and offshore habitats. Offshore summer chlorophyll-a declined significantly in both the short- (2000-2014) and long-term (1981-2014) time series at a rate of 4-6% per year. Nearshore chlorophyll-a increased after 2003 but then declined again after 2009. Epilimnetic chlorophyll-a averaged between 0.6 and 1.6 μg/L across sites with no difference between nearshore and offshore habitats. Apr/May – Oct Secchi depth ranged from 4.0 m to 10.8 m at individual sites and was higher in the offshore (average 9.1 m) than nearshore (5.9 m).In 2014, Apr/May – Oct epilimnetic zooplankton density, size, and biomass were not different between the offshore and the nearshore, and there were no differences in epilimnetic biomass between offshore and nearshore areas for any of the zooplankton groups.Zooplankton density and biomass peaked in September, an atypical pattern. This coincided with peaks in calanoid copepod, daphnid, and Holopedium biomass. Holopedium biomass in the nearshore increased significantly since 1995.The predatory cladoceran Cercopagis continued to be abundant in the summer, peaking at ~10 mg/m3in the offshore. Bythotrephes biomass was at its lowest level since 2005 in both offshore and nearshore habitats.Summer nearshore zooplankton density and biomass have declined significantly since 1995 at rates of 9-10% per year but have remained stable since 2005. However, bosminids and daphnids increased in 2013 and 2014.Summer offshore zooplankton density and biomass declined significantly in the long-term (since 1981), but remained at a lower stable level 2000 – 2014. A positive change point in 2013 is due to increases in bosminids, cyclopoid copepods, and daphnids.The observed decline in zooplankton biomass may be due in part to redistribution of zooplankton throughout the water column. Most of the zooplankton biomass was in the metalimnion and hypolimnion during the stratified period in 2014. By October, the bulk of the biomass was in the epilimnion.

Three-Dimensional Structure and Evolution of Extreme-Ultraviolet Bright Points Observed by STEREO/SECCHI/EUVI

NASA Technical Reports Server (NTRS)

Kwon, Ryun Young; Chae, Jongchul; Davila, Joseph M.; Zhang, Jie; Moon, Yong-Jae; Poomvises, Watanachak; Jones, Shaela I.

2012-01-01

We unveil the three-dimensional structure of quiet-Sun EUV bright points and their temporal evolution by applying a triangulation method to time series of images taken by SECCHI/EUVI on board the STEREO twin spacecraft. For this study we examine the heights and lengths as the components of the three-dimensional structure of EUV bright points and their temporal evolutions. Among them we present three bright points which show three distinct changes in the height and length: decreasing, increasing, and steady. We show that the three distinct changes are consistent with the motions (converging, diverging, and shearing, respectively) of their photospheric magnetic flux concentrations. Both growth and shrinkage of the magnetic fluxes occur during their lifetimes and they are dominant in the initial and later phases, respectively. They are all multi-temperature loop systems which have hot loops (approx. 10(exp 6.2) K) overlying cooler ones (approx 10(exp 6.0) K) with cool legs (approx 10(exp 4.9) K) during their whole evolutionary histories. Our results imply that the multi-thermal loop system is a general character of EUV bright points. We conclude that EUV bright points are flaring loops formed by magnetic reconnection and their geometry may represent the reconnected magnetic field lines rather than the separator field lines.

STEREO/SECCHI Stereoscopic Observations Constraining the Initiation of Polar Coronal Jets

NASA Technical Reports Server (NTRS)

Patsourakos, S.; Pariat, E.; Vourlidas, A.; Antiochos, S. K.; Wuelser, J. P.

2008-01-01

We report on the first stereoscopic observations of polar coronal jets made by the EUVI/SECCHI imagers on board the twin STEREO spacecraft. The significantly separated viewpoints (approximately 11 degrees ) allowed us to infer the 3D dynamics and morphology of a well-defined EUV coronal jet for the first time. Triangulations of the jet's location in simultaneous image pairs led to the true 3D position and thereby its kinematics. Initially the jet ascends slowly at approximately equal to 10-20 kilometers per second and then, after an apparent 'jump' takes place, it accelerates impulsively to velocities exceeding 300 kilometers per second with accelerations exceeding the solar gravity. Helical structure is the most important geometrical feature of the jet which shows evidence of untwisting. The jet structure appears strikingly different from each of the two STEREO viewpoints: face-on in the one viewpoint and edge-on in the other. This provides conclusive evidence that the observed helical structure is real and is not resulting from possible projection effects of single viewpoint observations. The clear demonstration of twisted structure in polar jets compares favorably with synthetic images from a recent MHD simulation of jets invoking magnetic untwisting as their driving mechanism. Therefore, the latter can be considered as a viable mechanism for the initiation of polar jets.

Kootenay Lake Fertilization Experiment, Year 15 (North Arm) and Year 3 (South Arm) (2006) Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schindler, E.U.; Sebastian, D.; Andrusak, G.F.

2009-07-01

This report summarizes results from the fifteenth year (2006) of nutrient additions to the North Arm of Kootenay Lake and three years of nutrient additions to the South Arm. Experimental fertilization of the lake has been conducted using an adaptive management approach in an effort to restore lake productivity lost as a result of nutrient uptake in upstream reservoirs. The primary objective of the experiment is to restore kokanee (Oncorhynchus nerka) populations, which are the main food source for Gerrard rainbow trout (Oncorhynchus mykiss) and bull trout (Salvelinus confluentus). The quantity of agricultural grade liquid fertilizer (10-34-0, ammonium polyphosphate andmore » 28-0-0, urea ammonium nitrate) added to the North Arm in 2006 was 44.7 tonnes of P and 248.4 tonnes of N. The total fertilizer load added to the South Arm was 257 tonnes of nitrogen; no P was added. Kootenay Lake has an area of 395 km{sup 2}, a maximum depth of 150 m, a mean depth of 94 m, and a water renewal time of approximately two years. Kootenay Lake is a monomictic lake, generally mixing from late fall to early spring and stratifying during the summer. Surface water temperatures generally exceed 20 C for only a few weeks in July. Results of oxygen profiles were similar to previous years with the lake being well oxygenated from the surface to the bottom depths at all stations. Similar to past years, Secchi disc measurements at all stations in 2006 indicate a typical seasonal pattern of decreasing depths associated with the spring phytoplankton bloom, followed by increasing depths as the bloom gradually decreases by the late summer and fall. Total phosphorus (TP) ranged from 2-7 {micro}g/L and tended to decrease as summer advanced. Over the sampling season dissolved inorganic nitrogen (DIN) concentrations decreased, with the decline corresponding to nitrate (the dominant component of DIN) being utilized by phytoplankton during summer stratification. Owing to the importance of epilimnetic nitrate that is required for optimal phytoplankton growth discrete depth water sampling occurred in 2006 to measure more accurately changes in the nitrate concentrations. As expected there was a seasonal decline in nitrate concentrations, thus supporting the strategy of increasing the nitrogen loading in both arms. These in-season changes emphasize the need for an adaptive management approach to ensure the nitrogen to phosphorus (N:P) ratio does not decrease below 15:1 (weight:weight) during the fertilizer application period. Phytoplankton composition determined from the integrated samples (0-20m) was dominated by diatoms, followed by cryptophytes and chrysophytes. The contribution of cryptophytes to total biomass was higher in 2006 than in 2005. Cryptophytes, considered being edible biomass for zooplankton and Daphnia spp., increased in 2006. Phytoplankton in the discrete depth samples (2, 5, 10, 15 and 20m) demonstrated a clear north to south gradient in average phytoplankton density and biomass among the three stations sampled, with highest values at the North Arm station (KLF 2) and lowest values in the most southern station in the South Arm (KLF 7). Populations were dominated by flagellates at all stations and depths in June and July, then dominated by diatoms in August and September in the North and South arms of the lake. There were no large bluegreen (cyanobacteria) populations in either arm of the lake in 2006. Seasonal average zooplankton abundance and biomass in both the main body of the lake and in the West Arm increased in 2006 compared to 2005. Zooplankton density was numerically dominated by copepods and biomass was dominated by Daphnia spp. The annual average mysid biomass data at deep stations indicated that the North Arm of Kootenay Lake was more productive than the South Arm in 2006. Mysid densities increased through the summer and declined in the winter; mean whole lake values remain within prefertilization densities. Kokanee escapement to Meadow Creek declined in 2006 to approximately 400,000 spawners. The Lardeau River escapement also declined with approximately 100,000 spawners. Escapement in the South Arm tributaries in 2006 was similar to 2005 with virtually no spawners. The mean size of female and male kokanee from Meadow Creek was larger than the past three years (24.9 cm and 25.2 cm, respectively) and larger than the long term average (25.2 cm). This is indicative of a density dependent growth response as a decline in in-lake abundance and returning spawners occurred. Spring hydroacoustic estimates indicated low densities of South Arm kokanee with most of the North Arm fry remaining at the most northerly stations. By the fall, the distribution of kokanee from the North Arm to the South Arm was fairly uniform, a normal occurrence in Kootenay Lake. Fall hydroacoustic estimates in 2006 increased to approximately 22 million kokanee.« less

Full-disc 13CO(1-0) mapping across nearby galaxies of the EMPIRE survey and the CO-to-H2 conversion factor

NASA Astrophysics Data System (ADS)

Cormier, D.; Bigiel, F.; Jiménez-Donaire, M. J.; Leroy, A. K.; Gallagher, M.; Usero, A.; Sandstrom, K.; Bolatto, A.; Hughes, A.; Kramer, C.; Krumholz, M. R.; Meier, D. S.; Murphy, E. J.; Pety, J.; Rosolowsky, E.; Schinnerer, E.; Schruba, A.; Sliwa, K.; Walter, F.

2018-04-01

Carbon monoxide (CO) provides crucial information about the molecular gas properties of galaxies. While 12CO has been targeted extensively, isotopologues such as 13CO have the advantage of being less optically thick and observations have recently become accessible across full galaxy discs. We present a comprehensive new data set of 13CO(1-0) observations with the IRAM 30-m telescope of the full discs of nine nearby spiral galaxies from the EMPIRE survey at a spatial resolution of ˜1.5 kpc. 13CO(1-0) is mapped out to 0.7 - 1 r25 and detected at high signal-to-noise ratio throughout our maps. We analyse the 12CO(1-0)-to-13CO(1-0) ratio (ℜ) as a function of galactocentric radius and other parameters such as the 12CO(2-1)-to-12CO(1-0) intensity ratio, the 70-to-160 μm flux density ratio, the star formation rate surface density, the star formation efficiency, and the CO-to-H2 conversion factor. We find that ℜ varies by a factor of 2 at most within and amongst galaxies, with a median value of 11 and larger variations in the galaxy centres than in the discs. We argue that optical depth effects, most likely due to changes in the mixture of diffuse/dense gas, are favoured explanations for the observed ℜ variations, while abundance changes may also be at play. We calculate a spatially resolved 13CO(1-0)-to-H2 conversion factor and find an average value of 1.0 × 1021 cm-2 (K km s-1)-1 over our sample with a standard deviation of a factor of 2. We find that 13CO(1-0) does not appear to be a good predictor of the bulk molecular gas mass in normal galaxy discs due to the presence of a large diffuse phase, but it may be a better tracer of the mass than 12CO(1-0) in the galaxy centres where the fraction of dense gas is larger.

Remineralization efficacy of a toothpaste containing 8% arginine and calcium carbonate on enamel surface.

PubMed

Huang, Yajing; Duan, Yanxia; Qian, Yingzi; Huang, Rui; Yang, Zhengyan; Li, Yueheng; Zhou, Zhi

2013-10-01

To investigate the remineralization efficacy of different types of toothpastes on initial enamel lesions in vitro. Artificial initial lesions were created on 150 enamel discs from freshly extracted bovine incisors. These enamel discs were divided into five groups. The test treatment consisted of undiluted Colgate Sensitive Pro-Relief Toothpaste containing 8.0% arginine, calcium carbonate and 1,450 ppm fluoride that was applied on the enamel surface under a pH-cycling including 4 x 3-minute application daily for 12 days and soaked in remineralizing solution during the untreated periods. The two other test products were commercial products: Crest Cavity Protection Toothpaste, containing 0.11% fluoride and GC Tooth Mousse, a professional remineralizing treatment paste (the active ingredients: casein phosphopeptide - amorphous calcium phosphate, fluoride). NaF solution (0.14% fluoride) was used as the positive control, while double distilled water (ddH2O) was used as the negative control. The remineralization of enamel discs was evaluated using Knoop hardness test, confocal laser scanning microscopy (CLSM) and polarized light microscopy (PLM), and the caries lesion depth was quantified using an image analyzer. The data were analyzed by ANOVA. All test products showed a recovery of the Knoop Hardness Number (KHN) after remineralization cycling treatment. The recovery of enamel KHN for Colgate Sensitive Pro-Relief, GC Mousse, Crest toothpasteand NaF groups were 44.53 +/- 6.72%, 35.00 +/- 7.83%, 24.56 +/- 5.95% and 42.51 +/- 6.74% respectively, while the recovery of negative control group was 18.99 +/- 4.98%. PLM results indicated the lesion depth recovery of 49.63 +/- 8.06%, 35.08 +/- 2.19%, 22.60 +/- 7.30% and 53.20 +/- 1.48% respectively, which were also significantly greater than that of the negative group (20.51 +/- 4.80%). CLSM analysis showed a reduction of average area, and total and average dye fluorescence of the lesions after treatment. The Colgate Sensitive Pro-Relief group presented significantly greater remineralization than the other toothpaste groups, while the Crest toothpaste group showed the lowest remineralization ability.

Naval Research Laboratory Space Science Division Newsletter: 01/2007

DTIC Science & Technology

2007-04-20

Temperature Solar Flare Images 5. SECCHI HI-1B First Light 6. NRL SEAP Student Receives Intel Science Talent Search Semifinalist Award 7. NASA...achieved first light on 28 OCT 2006. EIS is observing emission lines produced by highly ionized elements in the solar corona and transition region of...measurements of the solar corona and CMEs as they propagate through the inner heliosphere. STEREO launched October 25, 2006, and achieved first light in early

OCoc- from Ocean Colour to Organic Carbon

NASA Astrophysics Data System (ADS)

Heim, B.; Overduin, P. P.; Schirrmeister, L.; Doerffer, R.

2009-04-01

Enhanced permafrost warming and increased arctic river discharges have heightened concern about the input of terrigenous matter into Arctic coastal waters. Especially, large parts of the Central and Eastern Siberian coastline are characterized by highly erosive sedimentary ice-rich material. The ‘OCoc-from Ocean Colour to Organic Carbon' project (IPY-project 1176), funded by the German Research Foundation (DFG), is an Ocean Colour study joined with the Arctic Circum-polar Coastal Observatory Network Acco-Net (ACCO-Net: IPY-project 90) originating from the Arctic Coastal Dynamics ACD project . OCoc uses Ocean Colour satellite data for synoptic monitoring of the input of organic matter - from both fluvial and coastal sources - into the Arctic coastal waters. Initial results from the German-Russian Expedition Lena08 along the southeastern Laptev Sea Coast (Arctic Siberia, Russia) in August 2008 are presented. Ocean Colour MERIS Reduced Resolution (RR)-LIB data of the Laptev Sea Coast from August 2008 have been processed towards L2 parameters using Beam-Visat4.2© and the MERIS case2 regional processor for coastal application (C2R). C2R uses neural network procedures for the retrieval of water leaving reflectances and neural network procedures to derive the inherent optical properties (IOPs) from the water leaving reflectances. C2R output parameters are IOPs (absorption and backscattering coefficients), apparent optical properties (AOPs) (water leaving radiance reflectance, attenuation coefficient ‘k'), optical parameters such as the first attenuation depth (‘Z90') and calculated concentrations of chlorophyll, total suspended matter, and yellow substance absorption. Initial comparisons with Lena08-Expedition data (Secchi depths, cDOM) and water transparency data from former arctic cruises show that the MERIS-C2R optical parameters 'total absorption' and the first attenuation depth, 'Z90', seem adequately to represent true conditions. High attenuation values are the tracers for the organic-rich terrigenous input. The synoptic information of MERIS Ocean Colour products will provide valuable spatial and dynamical information on the Organic Carbon and sediment fluxes from the Siberian permafrost coast.

Comparison of animal discs used in disc research to human lumbar disc: torsion mechanics and collagen content.

PubMed

Showalter, Brent L; Beckstein, Jesse C; Martin, John T; Beattie, Elizabeth E; Espinoza Orías, Alejandro A; Schaer, Thomas P; Vresilovic, Edward J; Elliott, Dawn M

2012-07-01

Experimental measurement and normalization of in vitro disc torsion mechanics and collagen content for several animal species used in intervertebral disc research and comparing these with the human disc. To aid in the selection of appropriate animal models for disc research by measuring torsional mechanical properties and collagen content. There is lack of data and variability in testing protocols for comparing animal and human disc torsion mechanics and collagen content. Intervertebral disc torsion mechanics were measured and normalized by disc height and polar moment of inertia for 11 disc types in 8 mammalian species: the calf, pig, baboon, goat, sheep, rabbit, rat, and mouse lumbar discs, and cow, rat, and mouse caudal discs. Collagen content was measured and normalized by dry weight for the same discs except the rat and the mouse. Collagen fiber stretch in torsion was calculated using an analytical model. Measured torsion parameters varied by several orders of magnitude across the different species. After geometric normalization, only the sheep and pig discs were statistically different from human discs. Fiber stretch was found to be highly dependent on the assumed initial fiber angle. The collagen content of the discs was similar, especially in the outer annulus where only the calf and goat discs were statistically different from human. Disc collagen content did not correlate with torsion mechanics. Disc torsion mechanics are comparable with human lumbar discs in 9 of 11 disc types after normalization by geometry. The normalized torsion mechanics and collagen content of the multiple animal discs presented are useful for selecting and interpreting results for animal disc models. Structural organization of the fiber angle may explain the differences that were noted between species after geometric normalization.

Analysis of ambient conditions and simulation of hydrodynamics and water-quality characteristics in Beaver Lake, Arkansas, 2001 through 2003

USGS Publications Warehouse

Galloway, Joel M.; Green, W. Reed

2006-01-01

Beaver Lake is a large, deep-storage reservoir located in the upper White River Basin in northwestern Arkansas. The purpose of this report is to describe the ambient hydrologic and water-quality conditions in Beaver Lake and its inflows and describe a two-dimensional model developed to simulate the hydrodynamics and water quality of Beaver Lake from 2001 through 2003. Water-quality samples were collected at the three main inflows to Beaver Lake; the White River near Fayetteville, Richland Creek at Goshen, and War Eagle Creek near Hindsville. Nutrient concentrations varied among the tributaries because of land use and contributions of nutrients from point sources. The median concentrations of total ammonia plus organic nitrogen were greater for the White River than Richland and War Eagle Creeks. The greatest concentrations of nitrite plus nitrate and total nitrogen, however, were observed at War Eagle Creek. Phosphorus concentrations were relatively low, with orthophosphorus and dissolved phosphorus concentrations mostly below the laboratory reporting limit at the three sites. War Eagle Creek had significantly greater median orthophosphorus and total phosphorus concentrations than the White River and Richland Creek. Dissolved organic-carbon concentrations were significantly greater at the White River than at War Eagle and Richland Creeks. The White River also had significantly greater turbidity than War Eagle Creek and Richland Creek. The temperature distribution in Beaver Lake exhibits the typical seasonal cycle of lakes and reservoirs located within similar latitudes. Beaver Lake is a monomictic system, in which thermal stratification occurs annually during the summer and fall and complete mixing occurs in the winter. Isothermal conditions exist throughout the winter and early spring. Nitrogen concentrations varied temporally, longitudinally, and vertically in Beaver Lake for 2001 through 2003. Nitrite plus nitrate concentrations generally decreased from the upstream portion of Beaver Lake to the downstream portion and generally were greater in the hypolimnion. Total ammonia plus organic nitrogen concentrations also decreased from the upstream end of Beaver Lake to the downstream end and were substantially greater in the hypolimnion of Beaver Lake. Phosphorus concentrations mostly were near or below laboratory detection limits in the epilimnion and metalimnion in Beaver Lake and were substantially greater in the hypolimnion in the upstream and middle parts of the reservoir. Measured total and dissolved organic carbon in Beaver Lake was relatively uniform spatially, longitudinally, and vertically in the reservoir from January 2001 through December 2003. Chlorophyll a concentrations measured at sites in the upstream portion of the lake were significantly greater than at the other sites in the downstream portion of Beaver Lake. During the study period, water clarity in Beaver Lake was significantly greater at the downstream end of the reservoir than at the upstream end. The greatest Secchi depths at the downstream end of the reservoir generally were observed in 2001 compared to 2002 and 2003, but did not have a seasonal pattern as observed at sites in the middle and upstream portion of the reservoir. Similar to Secchi depth results, turbidity results indicated greater water clarity in the downstream portion of Beaver Lake compared to the upstream portion. Turbidity also was greater in the hypolimnion than in the epilimnion in the reservoir during the stratification season. A two-dimensional, laterally averaged, hydrodynamic, and water-quality model using CE-QUAL-W2 Version 3.1 was developed for Beaver Lake and calibrated based on vertical profiles of temperature and dissolved oxygen, and water-quality constituent concentrations collected at various depths at four sites in the reservoir from April 2001 to April 2003. Simulated temperatures and dissolved-oxygen concentrations compared reasonably well with measured t

A Novel Mobile Testing Equipment for Rock Cuttability Assessment: Vertical Rock Cutting Rig (VRCR)

NASA Astrophysics Data System (ADS)

Yasar, Serdar; Yilmaz, Ali Osman

2017-04-01

In this study, a new mobile rock cutting testing apparatus was designed and produced for rock cuttability assessment called vertical rock cutting rig (VRCR) which was designed specially to fit into hydraulic press testing equipment which are available in almost every rock mechanics laboratory. Rock cutting trials were initiated just after the production of VRCR along with calibration of the measuring load cell with an external load cell to validate the recorded force data. Then, controlled rock cutting tests with both relieved and unrelieved cutting modes were implemented on five different volcanic rock samples with a standard simple-shaped wedge tool. Additionally, core cutting test which is an important approach for roadheader performance prediction was simulated with VRCR. Mini disc cutters and point attack tools were used for execution of experimental trials. Results clearly showed that rock cutting tests were successfully realized and measuring system is delicate to rock strength, cutting depth and other variables. Core cutting test was successfully simulated, and it was also shown that rock cutting tests with mini disc cutters and point attack tools are also successful with VRCR.

In vitro wear of new indirect resin composites.

PubMed

Jain, V; Platt, J A; Moore, B K; Borges, G A

2009-01-01

This in vitro study evaluated the toothbrush abrasion wear, three-body Alabama wear and two-body pin-on-disc wear of four commercial indirect resin composites. Enamel shades of Radica (R), Sculpture Plus (S), Belleglass-NG (B) and Gradia Indirect (G) were used. For measuring wear due to toothbrush abrasion, six specimens of each group were fabricated, then brushed in a toothbrush abrasion machine for 20,000 cycles. Material loss was determined by weighing and conversion to volume loss. Three-body wear was measured on six samples for each group using an Alabama-type wear testing machine for 400,000 cycles. Wear depth was measured with a contact profilometer. For two-body wear, five disc specimens were prepared and tested in a two-body wear-testing machine against hydroxypatite sliders for 25,000 cycles. Data were analyzed with one-way analysis of variance (ANOVA) and Tukey test (alpha=0.05). Wear was the highest in Sculpture Plus by all three methods tested and the lowest wear was observed in Belleglass-NG. No statistical difference in wear was noted from Radica.

Geographic and Environmental Sources of Variation in Lake Bacterial Community Composition†

PubMed Central

Yannarell, Anthony C.; Triplett, Eric W.

2005-01-01

This study used a genetic fingerprinting technique (automated ribosomal intergenic spacer analysis [ARISA]) to characterize microbial communities from a culture-independent perspective and to identify those environmental factors that influence the diversity of bacterial assemblages in Wisconsin lakes. The relationships between bacterial community composition and 11 environmental variables for a suite of 30 lakes from northern and southern Wisconsin were explored by canonical correspondence analysis (CCA). In addition, the study assessed the influences of ARISA fragment detection threshold (sensitivity) and the quantitative, semiquantitative, and binary (presence-absence) use of ARISA data. It was determined that the sensitivity of ARISA was influential only when presence-absence-transformed data were used. The outcomes of analyses depended somewhat on the data transformation applied to ARISA data, but there were some features common to all of the CCA models. These commonalities indicated that differences in bacterial communities were best explained by regional (i.e., northern versus southern Wisconsin lakes) and landscape level (i.e., seepage lakes versus drainage lakes) factors. ARISA profiles from May samples were consistently different from those collected in other months. In addition, communities varied along gradients of pH and water clarity (Secchi depth) both within and among regions. The results demonstrate that environmental, temporal, regional, and landscape level features interact to determine the makeup of bacterial assemblages in northern temperate lakes. PMID:15640192

Satellite-based virtual buoy system to monitor coastal water quality

NASA Astrophysics Data System (ADS)

Hu, Chuanmin; Barnes, Brian B.; Murch, Brock; Carlson, Paul

2014-05-01

There is a pressing need to assess coastal and estuarine water quality state and anomaly events to facilitate coastal management, but such a need is hindered by lack of resources to conduct frequent ship-based or buoy-based measurements. Here, we established a virtual buoy system (VBS) to facilitate satellite data visualization and interpretation of water quality assessment. The VBS is based on a virtual antenna system (VAS) that obtains low-level satellite data and generates higher-level data products using both National Aeronautics and Space Administration standard algorithms and regionally customized algorithms in near real time. The VB stations are predefined and carefully chosen to cover water quality gradients in estuaries and coastal waters, where multiyear time series at monthly and weekly intervals are extracted for the following parameters: sea surface temperature (°C), chlorophyll-a concentration (mg m-3), turbidity (NTU), diffuse light attenuation at 490 nm [Kd(490), m-1] or secchi disk depth (m), absorption coefficient of colored dissolved organic matter (m-1), and bottom available light (%). The time-series data are updated routinely and provided in both ASCII and graphical formats via a user-friendly web interface where all information is available to the user through a simple click. The VAS and VBS also provide necessary infrastructure to implement peer-reviewed regional algorithms to generate and share improved water quality data products with the user community.

Occurrence and dominance of Cylindrospermopsis raciborskii and dissolved cylindrospermopsin in urban reservoirs used for drinking water supply, South China.

PubMed

Lei, Lamei; Peng, Liang; Huang, Xianghui; Han, Bo-Ping

2014-05-01

The tropical cyanobacterium Cylindrospermopsis raciborskii is of particular concern for its invasive characteristics and production of the toxin cylindrospermopsin (CYN). The present study represents the first attempt to determine the distribution of C. raciborskii and CYN in tropical China. The presence of C. raciborskii and CYN, as well as the composition of phytoplankton, was determined from a total of 86 samples from 25 urban reservoirs for drinking water supply in Dongguan City of South China. The presence of C. raciborskii was observed in 21 of the 25 reservoirs and confirmed that this species has been widely distributed in the investigated reservoirs. C. raciborskii accounted for between 0.1 and 90.3 % of the total phytoplankton biomass and contributed to the majority of the phytoplankton in some reservoirs such as Tangkengbian and Xiagongyan. Its biomass was negatively correlated with NO3 (-)-N concentration and Secchi depth. Dissolved CYN was detected in more than one-half of the reservoirs with concentrations up to 8.25 μg L(-1), and it positively correlated with C. raciborskii biomass. Dissolved microcystins (MCs) were detected in 12 of the 25 reservoirs with a maximum concentration 1.99 μg L(-1). Our data strongly suggest that C. raciborskii and CYN could be important health hazards in urban reservoirs of South China and that more data are needed for further assessment.

Predicting potentially toxigenic Pseudo-nitzschia blooms in the Chesapeake Bay

USGS Publications Warehouse

Anderson, C.R.; Sapiano, M.R.P.; Prasad, M.B.K.; Long, W.; Tango, P.J.; Brown, C.W.; Murtugudde, R.

2010-01-01

Harmful algal blooms are now recognized as a significant threat to the Chesapeake Bay as they can severely compromise the economic viability of important recreational and commercial fisheries in the largest estuary of the United States. This study describes the development of empirical models for the potentially domoic acid-producing Pseudo-nitzschia species complex present in the Bay, developed from a 22-year time series of cell abundance and concurrent measurements of hydrographic and chemical properties. Using a logistic Generalized Linear Model (GLM) approach, model parameters and performance were compared over a range of Pseudo-nitzschia bloom thresholds relevant to toxin production by different species. Small-threshold blooms (???10cellsmL-1) are explained by time of year, location, and variability in surface values of phosphate, temperature, nitrate plus nitrite, and freshwater discharge. Medium- (100cellsmL-1) to large- threshold (1000cellsmL-1) blooms are further explained by salinity, silicic acid, dissolved organic carbon, and light attenuation (Secchi) depth. These predictors are similar to other models for Pseudo-nitzschia blooms on the west coast, suggesting commonalities across ecosystems. Hindcasts of bloom probabilities at a 19% bloom prediction point yield a Heidke Skill Score of -53%, a Probability of Detection ~75%, a False Alarm Ratio of ~52%, and a Probability of False Detection ~9%. The implication of possible future changes in Baywide nutrient stoichiometry on Pseudo-nitzschia blooms is discussed. ?? 2010 Elsevier B.V.

Monitoring water quality in a hypereutrophic reservoir using Landsat ETM+ and OLI sensors: how transferable are the water quality algorithms?

PubMed

Deutsch, Eliza S; Alameddine, Ibrahim; El-Fadel, Mutasem

2018-02-15

The launch of the Landsat 8 in February 2013 extended the life of the Landsat program to over 40 years, increasing the value of using Landsat to monitor long-term changes in the water quality of small lakes and reservoirs, particularly in poorly monitored freshwater systems. Landsat-based water quality hindcasting often incorporate several Landsat sensors in an effort to increase the temporal range of observations; yet the transferability of water quality algorithms across sensors remains poorly examined. In this study, several empirical algorithms were developed to quantify chlorophyll-a, total suspended matter (TSM), and Secchi disk depth (SDD) from surface reflectance measured by Landsat 7 ETM+ and Landsat 8 OLI sensors. Sensor-specific multiple linear regression models were developed by correlating in situ water quality measurements collected from a semi-arid eutrophic reservoir with band ratios from Landsat ETM+ and OLI sensors, along with ancillary data (water temperature and seasonality) representing ecological patterns in algae growth. Overall, ETM+-based models outperformed (adjusted R 2 chlorophyll-a = 0.70, TSM = 0.81, SDD = 0.81) their OLI counterparts (adjusted R 2 chlorophyll-a = 0.50, TSM = 0.58, SDD = 0.63). Inter-sensor differences were most apparent for algorithms utilizing the Blue spectral band. The inclusion of water temperature and seasonality improved the power of TSM and SDD models.

Assessment of the Eutrophication-Related Environmental Parameters in Two Mediterranean Lakes by Integrating Statistical Techniques and Self-Organizing Maps

PubMed Central

Stefanidis, Konstantinos; Papatheodorou, George

2018-01-01

During the last decades, Mediterranean freshwater ecosystems, especially lakes, have been under severe pressure due to increasing eutrophication and water quality deterioration. In this article, we compared the effectiveness of different data analysis methods by assessing the contribution of environmental parameters to eutrophication processes. For this purpose, principal components analysis (PCA), cluster analysis, and a self-organizing map (SOM) were applied, using water quality data from two transboundary lakes of North Greece. SOM is considered as an advanced and powerful data analysis tool because of its ability to represent complex and nonlinear relationships among multivariate data sets. The results of PCA and cluster analysis agreed with the SOM results, although the latter provided more information because of the visualization abilities regarding the parameters’ relationships. Besides nutrients that were found to be a key factor for controlling chlorophyll-a (Chl-a), water temperature was related positively with algal production, while the Secchi disk depth parameter was found to be highly important and negatively related toeutrophic conditions. In general, the SOM results were more specific and allowed direct associations between the water quality variables. Our work showed that SOMs can be used effectively in limnological studies to produce robust and interpretable results, aiding scientists and managers to cope with environmental problems such as eutrophication. PMID:29562675

Detailed Vascular Anatomy of the Human Retina by Projection-Resolved Optical Coherence Tomography Angiography

NASA Astrophysics Data System (ADS)

Campbell, J. P.; Zhang, M.; Hwang, T. S.; Bailey, S. T.; Wilson, D. J.; Jia, Y.; Huang, D.

2017-02-01

Optical coherence tomography angiography (OCTA) is a noninvasive method of 3D imaging of the retinal and choroidal circulations. However, vascular depth discrimination is limited by superficial vessels projecting flow signal artifact onto deeper layers. The projection-resolved (PR) OCTA algorithm improves depth resolution by removing projection artifact while retaining in-situ flow signal from real blood vessels in deeper layers. This novel technology allowed us to study the normal retinal vasculature in vivo with better depth resolution than previously possible. Our investigation in normal human volunteers revealed the presence of 2 to 4 distinct vascular plexuses in the retina, depending on location relative to the optic disc and fovea. The vascular pattern in these retinal plexuses and interconnecting layers are consistent with previous histologic studies. Based on these data, we propose an improved system of nomenclature and segmentation boundaries for detailed 3-dimensional retinal vascular anatomy by OCTA. This could serve as a basis for future investigation of both normal retinal anatomy, as well as vascular malformations, nonperfusion, and neovascularization.

[Research progress of intervertebral disc endogenous stem cells for intervertebral disc regeneration].

PubMed

Liang, Hang; Deng, Xiangyu; Shao, Zengwu

2017-10-01

To summarize the research progress of intervertebral disc endogenous stem cells for intervertebral disc regeneration and deduce the therapeutic potential of endogenous repair for intervertebral disc degeneration. The original articles about intervertebral disc endogenous stem cells for intervertebral disc regeneration were extensively reviewed; the reparative potential in vivo and the extraction and identification in vitro of intervertebral disc endogenous stem cells were analyzed; the prospect of endogenous stem cells for intervertebral disc regeneration was predicted. Stem cell niche present in the intervertebral discs, from which stem cells migrate to injured tissues and contribute to tissues regeneration under certain specific microenvironment. Moreover, the migration of stem cells is regulated by chemokines system. Tissue specific progenitor cells have been identified and successfully extracted and isolated. The findings provide the basis for biological therapy of intervertebral disc endogenous stem cells. Intervertebral disc endogenous stem cells play a crucial role in intervertebral disc regeneration. Therapeutic strategy of intervertebral disc endogenous stem cells is proven to be a promising biological approach for intervertebral disc regeneration.

Comparison of Animal Discs Used in Disc Research to Human Lumbar Disc: Torsion Mechanics and Collagen Content

PubMed Central

Showalter, Brent L.; Beckstein, Jesse C.; Martin, John T.; Beattie, Elizabeth E.; Orías, Alejandro A. Espinoza; Schaer, Thomas P.; Vresilovic, Edward J.; Elliott, Dawn M.

2012-01-01

Study Design Experimental measurement and normalization of in vitro disc torsion mechanics and collagen content for several animal species used in intervertebral disc research and comparing these to the human disc. Objective To aid in the selection of appropriate animal models for disc research by measuring torsional mechanical properties and collagen content. Summary of Background Data There is lack of data and variability in testing protocols for comparing animal and human disc torsion mechanics and collagen content. Methods Intervertebral disc torsion mechanics were measured and normalized by disc height and polar moment of inertia for 11 disc types in 8 mammalian species: the calf, pig, baboon, goat, sheep, rabbit, rat, and mouse lumbar, and cow, rat, and mouse caudal. Collagen content was measured and normalized by dry weight for the same discs except the rat and mouse. Collagen fiber stretch in torsion was calculated using an analytical model. Results Measured torsion parameters varied by several orders of magnitude across the different species. After geometric normalization, only the sheep and pig discs were statistically different from human. Fiber stretch was found to be highly dependent on the assumed initial fiber angle. The collagen content of the discs was similar, especially in the outer annulus where only the calf and goat discs were statistically different from human. Disc collagen content did not correlate with torsion mechanics. Conclusion Disc torsion mechanics are comparable to human lumbar discs in 9 of 11 disc types after normalization by geometry. The normalized torsion mechanics and collagen content of the multiple animal discs presented is useful for selecting and interpreting results for animal models of the disc. Structural composition of the disc, such as initial fiber angle, may explain the differences that were noted between species after geometric normalization. PMID:22333953

Glaucoma-induced optic disc morphometric changes and glaucoma diagnostic ability of Heidelberg Retina Tomograph II in highly myopic eyes.

PubMed

Mayama, Chihiro; Tsutsumi, Tae; Saito, Hitomi; Asaoka, Ryo; Tomidokoro, Atsuo; Iwase, Aiko; Otani, Shinichiro; Miyata, Kazunori; Araie, Makoto

2014-01-01

This study was performed to first investigate the morphological differences in the optic nerve head between highly myopic non-glaucomatous controls and highly myopic glaucomatous eyes in comparison with the differences between emmetropic non-glaucomatous controls and emmetropic glaucomatous eyes using confocal scanning laser ophthalmoscopy. Further, the ability of the apparatus in glaucoma diagnosis in highly myopic eyes was compared with that in emmetropic eyes. Healthy subjects and age-matched patients with early-stage open-angle glaucoma were divided into two groups: emmetropic eyes (-1.0 to +1.0 diopters) and highly myopic eyes (-12.0 to -5.0 diopters).The participants were comprised of 65 emmetropic normal eyes, 59 emmetropic glaucomatous eyes, 62 highly myopic normal eyes, and 68 highly myopic glaucomatous eyes and eyes with pathologic myopia were carefully excluded. Confocal scanning laser tomographic parameters were compared among all subjects after adjustment for age and disc area. The ROC curves and sensitivity and specificity for glaucoma detection using several clinical methods were then compared between the emmetropic and highly myopic eyes. Rim area, cup/disc area ratio, mean cup depth, and cup shape measure of glaucoma eyes are significantly different from those of normal eyes in both highly myopic eyes and emmetropic eyes. Methodological overestimation of retinal nerve fiber layer cross sectional area due to optic disc tilting was suggested in the highly myopic eyes. The diagnostic performance of glaucoma using several discriminant methods significantly deteriorated in the highly myopic eyes. In the highly myopic glaucomatous eyes, confocal scanning laser tomographic parameters were significantly different from that of non-glaucomatous highly myopic eyes but diagnostic performance of glaucoma was deteriorated than that in emmetropic eyes. These findings demonstrate the utility and limitations of the apparatus in diagnosing glaucoma in highly myopic patients.

Choroidal thickness in Chinese patients with non-arteritic anterior ischemic optic neuropathy.

PubMed

Jiang, Libin; Chen, Lanlan; Qiu, Xiujuan; Jiang, Ran; Wang, Yaxing; Xu, Liang; Lai, Timothy Y Y

2016-08-31

Non-arteritic anterior ischemic optic neuropathy (NA-AION) is one of the most common types of ischemic optic neuropathy. Several recent studies suggested that abnormalities of choroidal thickness might be associated with NA-AION. The main objective of this case-control study was to evaluate whether choroidal thickness is an ocular risk factor for the development of NA-AION by evaluating the peripapillary and subfoveal choroidal thicknesses in affected Chinese patients. Forty-four Chinese patients with unilateral NA-AION were recruited and compared with 60 eyes of 60 normal age and refractive-error matched control subjects. Peripapillary and subfoveal choroidal thicknesses were measured by enhanced depth imaging optical coherence tomography. Choroidal thicknesses of eyes with NA-AION and unaffected fellow eyes were compared with normal controls. Choroidal thicknesses of NA-AION eyes with or without optic disc edema were also compared. The correlation between choroidal thickness and retinal nerve fiber layer (RNFL) thickness, logMAR best-corrected visual acuity (BCVA), and the mean deviation (MD) of Humphrey static perimetry in NA-AION eyes were analyzed. The peripapillary choroidal thicknesses at the nasal, nasal inferior and temporal inferior segments in NA-AION eyes with optic disc edema were significantly thicker compared with that of normal subjects (P < 0.05). There was no significant difference in the choroidal thicknesses between the unaffected fellow eyes of NA-AION patients and normal eyes of healthy controls; or between the NA-AION eyes with resolved optic disc edema and normal eyes (all P > 0.05). No significant correlation between choroidal thickness and RNFL thickness, logMAR BCVA and perimetry MD was found in eyes affected by NA-AION (all P > 0.05). Increase in peripapillary choroid thickness in some segments was found in NA-ION eyes with optic disc edema. However, our findings do not support the hypothesis that choroidal thickness is abnormal in Chinese patients with NA-AION compared with normal subjects with similar age and refractive error status.

Study on Tribological Properties of CoCrMo Alloys against Metals and Ceramics as Bearing Materials for Artificial Cervical Disc

NASA Astrophysics Data System (ADS)

Xiang, Dingding; Song, Jian; Wang, Song; Liao, Zhenhua; Liu, Yuhong; Tyagi, Rajnesh; Liu, Weiqiang

2018-02-01

CoCrMo alloys are believed to be a kind of potential material for artificial cervical disc. However, the tribological properties of CoCrMo alloys against different metals and ceramics are not systematically studied. In this study, the tribological behaviors of CoCrMo alloys against metals (316L, Ti6Al4V) and ceramics (Si3N4, ZrO2) were focused under dry friction and 25 wt.% newborn calf serum (NCS)-lubricated conditions using a ball-on-disc apparatus under reciprocating motion. The microstructure, composition and hardness of CoCrMo alloys were characterized using x-ray diffraction, scanning electron microscopy (SEM) and hardness testers, respectively. The contact angles of the CoCrMo alloys with deionized water and 25 wt.% NCS were measured by the OCA contact angle measuring instrument. The maximum wear width, wear depth and wear volume were measured by three-dimensional white light interference. The morphology and the EDX analysis of the wear marks on CoCrMo alloys were examined by SEM to determine the basic mechanism of friction and wear. The dominant wear mechanism in dry friction for CoCrMo alloys against all pairings was severe abrasive wear, accompanied with a lot of material transfer. Under 25 wt.% NCS-lubricated condition, the wear mechanism for CoCrMo alloys against ceramics (Si3N4, ZrO2) was also mainly severe abrasive wear. However, severe abrasive wear and electrochemical corrosion occurred for the CoCrMo-316L pairing under lubrication. Severe abrasive wear, adhesive wear and electrochemical corrosion occurred for the CoCrMo-Ti6Al4V pairing under lubrication. According to the results, the tribological properties of CoCrMo alloys against ceramics were better than those against metals. The CoCrMo-ZrO2 pairing displayed the best tribological behaviors and could be taken as a potential candidate bearing material for artificial cervical disc.

Peripapillary Retinoschisis in Glaucomatous Eyes

PubMed Central

Lee, Eun Ji; Kim, Tae-Woo; Kim, Mijin; Choi, Yun Jeong

2014-01-01

Purpose To investigate the structural and clinical characteristics of peripapillary retinoschisis observed in glaucomatous eyes using spectral-domain optical coherence tomography (SD-OCT). Methods Circumpapillary retinal nerve fiber layer (cpRNFL) and macular cross-hair SD-OCT scans and infrared fundus images of the glaucoma patients from the Investigating Glaucoma Progression Study (IGPS) and healthy volunteers were reviewed. Optic disc images obtained using enhanced depth imaging (EDI) SD-OCT were also evaluated. The structural characteristics and clinical course of the retinoschisis associated with glaucoma were investigated. Results Twenty-five retinoschisis areas were found in 22 of the 372 patients (5.9%) included in the IGPS, and in 1 area in 1 of 187 healthy control subjects (0.5%). In the 22 glaucomatous eyes with retinoschisis, the schisis was attached to the optic disc and overlapped with the retinal nerve fiber layer (RNFL) defect. The RNFL was the layer most commonly affected by the retinoschisis, either alone or together with other deeper layers. Acquired optic disc pit was identified in 8 eyes on disc photography and/or B-scan images obtained by EDI SD-OCT. Spontaneous resolution of this condition was observed in nine eyes. No retinal detachment or macular involvement of the retinoschisis was observed in any of the eyes. Multivariate analysis showed a significant influence of a higher intraocular pressure at SD-OCT scanning on the presence of retinoschisis (Odds ratio  = 1.418, P = 0.001). Conclusions The present study investigated 22 cases of peripapillary retinoschisis in glaucomatous eyes. The retinoschisis was attached to the optic nerve and topographically correlated with RNFL defect. It often resolved spontaneously without causing severe visual disturbance. Care should be taken not to overestimate the RNFL thickness in eyes with retinoschisis, and also not to misinterpret the resolution of retinoschisis as a rapid glaucomatous RNFL deterioration. PMID:24587238

Gobiesox lanceolatus, a new species of clingfish (Teleostei:  Gobiesocidae) from Los Frailes submarine canyon, Gulf of California, Mexico.

PubMed

Hastings, Philip A; Conway, Kevin W

2017-01-17

Gobiesox lanceolatus is described from a single specimen collected from 300 meters depth in the Los Frailes submarine canyon in the southwestern Gulf of California. The "Canyon Clingfish" is unique within Gobiesox in having a lanceolate caudal fin, with the central rays longer than those above and below them. It is also distinguished by 14 dorsal-fin rays (first tiny and unsegmented), 11 anal-fin rays, 28 pectoral-fin rays, anus slightly closer to anal-fin origin than to posterior margin of pelvic disc, and dorsal-fin origin in front of vertical from anus. It is most similar to Gobiesox eugrammus, known from Isla Guadelupe, the coast of outer Baja California and southern California. This is the deepest record for a species of Gobiesox and only four other species of clingfishes are known from greater depths.

Continuous water sampling and water analysis in estuaries

USGS Publications Warehouse

Schemel, L.E.; Dedini, L.A.

1982-01-01

Salinity, temperature, light transmission, oxygen saturation, pH, pCO2, chlorophyll a fluorescence, and the concentrations of nitrate, nitrite, dissolved silica, orthophosphate, and ammonia are continuously measured with a system designed primarily for estuarine studies. Near-surface water (2-m depth) is sampled continuously while the vessel is underway; on station, water to depths of 100 m is sampled with a submersible pump. The system is comprised of commercially available instruments, equipment, and components, and of specialized items designed and fabricated by the authors. Data are read from digital displays, analog strip-chart recorders, and a teletype printout, and can be logged in disc storage for subsequent plotting. Data records made in San Francisco Bay illustrate physical, biological, and chemical estuarine processes, such as mixing and phytoplankton net production. The system resolves large- and small-scale events, which contributes to its reliability and usefulness.

Process cost and facility considerations in the selection of primary cell culture clarification technology.

PubMed

Felo, Michael; Christensen, Brandon; Higgins, John

2013-01-01

The bioreactor volume delineating the selection of primary clarification technology is not always easily defined. Development of a commercial scale process for the manufacture of therapeutic proteins requires scale-up from a few liters to thousands of liters. While the separation techniques used for protein purification are largely conserved across scales, the separation techniques for primary cell culture clarification vary with scale. Process models were developed to compare monoclonal antibody production costs using two cell culture clarification technologies. One process model was created for cell culture clarification by disc stack centrifugation with depth filtration. A second process model was created for clarification by multi-stage depth filtration. Analyses were performed to examine the influence of bioreactor volume, product titer, depth filter capacity, and facility utilization on overall operating costs. At bioreactor volumes <1,000 L, clarification using multi-stage depth filtration offers cost savings compared to clarification using centrifugation. For bioreactor volumes >5,000 L, clarification using centrifugation followed by depth filtration offers significant cost savings. For bioreactor volumes of ∼ 2,000 L, clarification costs are similar between depth filtration and centrifugation. At this scale, factors including facility utilization, available capital, ease of process development, implementation timelines, and process performance characterization play an important role in clarification technology selection. In the case study presented, a multi-product facility selected multi-stage depth filtration for cell culture clarification at the 500 and 2,000 L scales of operation. Facility implementation timelines, process development activities, equipment commissioning and validation, scale-up effects, and process robustness are examined. © 2013 American Institute of Chemical Engineers.

Electromagnetic versus Lense-Thirring alignment of black hole accretion discs

NASA Astrophysics Data System (ADS)

Polko, Peter; McKinney, Jonathan C.

2017-01-01

Accretion discs and black holes (BHs) have angular momenta that are generally misaligned, which can lead to warped discs and bends in any jets produced. We examine whether a disc that is misaligned at large radii can be aligned more efficiently by the torque of a Blandford-Znajek (BZ) jet than by Lense-Thirring (LT) precession. To obtain a strong result, we will assume that these torques maximally align the disc, rather than cause precession, or disc tearing. We consider several disc states that include radiatively inefficient thick discs, radiatively efficient thin discs, and super-Eddington accretion discs. The magnetic field strength of the BZ jet is chosen as either from standard equipartition arguments or from magnetically arrested disc (MAD) simulations. We show that standard thin accretion discs can reach spin-disc alignment out to large radii long before LT would play a role, due to the slow infall time that gives even a weak BZ jet time to align the disc. We show that geometrically thick radiatively inefficient discs and super-Eddington discs in the MAD state reach spin-disc alignment near the BH when density profiles are shallow as in magnetohydrodynamical simulations, while the BZ jet aligns discs with steep density profiles (as in advection-dominated accretion flows) out to larger radii. Our results imply that the BZ jet torque should affect the cosmological evolution of BH spin magnitude and direction, spin measurements in active galactic nuclei and X-ray binaries, and the interpretations for Event Horizon Telescope observations of discs or jets in strong-field gravity regimes.

Quantification of in vitro produced wear sites on composite resins using contact profilometry and CCD microscopy: a methodological investigation.

PubMed

Koottathape, Natthavoot; Takahashi, Hidekazu; Finger, Wernerj; Kanehira, Masafumi; Iwasaki, Naohiko; Aoyagi, Yujin

2012-06-01

Although attritive and abrasive wear of recent composite resins has been substantially reduced, in vitro wear testing with reasonably simulating devices and quantitative determination of resulting wear is still needed. Three-dimensional scanning methods are frequently used for this purpose. The aim of this trial was to compare maximum depth of wear and volume loss of composite samples, evaluated with a contact profilometer and a non-contact CCD camera imaging system, respectively. Twenty-three random composite specimens with wear traces produced in a ball-on-disc sliding device, using poppy seed slurry and PMMA suspension as third-body media, were evaluated with the contact profilometer (TalyScan 150, Taylor Hobson LTD, Leicester, UK) and with the digital CCD microscope (VHX1000, KEYENCE, Osaka, Japan). The target parameters were maximum depth of the wear and volume loss.Results - The individual time of measurement needed with the non-contact CCD method was almost three hours less than that with the contact method. Both, maximum depth of wear and volume loss data, recorded with the two methods were linearly correlated (r(2) > 0.97; p < 0.01). The contact scanning method and the non-contact CCD method are equally suitable for determination of maximum depth of wear and volume loss of abraded composite resins.

Kinematic Evaluation of Association between Disc Bulge Migration, Lumbar Segmental Mobility, and Disc Degeneration in the Lumbar Spine Using Positional Magnetic Resonance Imaging

PubMed Central

Hu, Jonathan K.; Morishita, Yuichiro; Montgomery, Scott R.; Hymanson, Henry; Taghavi, Cyrus E.; Do, Duc; Wang, Jeff C.

2011-01-01

Degenerative disc disease and disc bulge in the lumbar spine are common sources of lower back pain. Little is known regarding disc bulge migration and lumbar segmental mobility as the lumbar spine moves from flexion to extension. In this study, 329 symptomatic (low back pain with or without neurological symptoms) patients with an average age of 43.5 years with varying degrees of disc degeneration were examined to characterize the kinematics of the lumbar intervertebral discs through flexion, neutral, and extension weight-bearing positions. In this population, disc bulge migration associated with dynamic motion of the lumbar spine significantly increased with increased grade of disk degeneration. Although no obvious trends relating the migration of disc bulge and angular segmental mobility were seen, translational segmental mobility tended to increase with disc bulge migration in all of the degenerative disc states. It appears that many factors, both static (intervertebral disc degeneration or disc height) and dynamic (lumbar segmental mobility), affect the mechanisms of lumbar disc bulge migration. PMID:24353937

Imaginal Disc Abnormalities in Lethal Mutants of Drosophila

PubMed Central

Shearn, Allen; Rice, Thomas; Garen, Alan; Gehring, Walter

1971-01-01

Late lethal mutants of Drosophila melanogaster, dying after the larval stage of development, were isolated. The homozygous mutant larvae were examined for abnormal imaginal disc morphology, and the discs were injected into normal larval hosts to test their capacities to differentiate into adult structures. In about half of the mutants analyzed, disc abnormalities were found. Included among the abnormalities were missing discs, small discs incapable of differentiating, morphologically normal discs with limited capacities for differentiation, and discs with homeotic transformations. In some mutants all discs were affected, and in others only certain discs. The most extreme abnormal phenotype is a class of “discless” mutants. The viability of these mutant larvae indicates that the discs are essential only for the development of an adult and not of a larva. The late lethals are therefore a major source of mutants for studying the genetic control of disc formation. Images PMID:5002822

Intermediate mass black holes in AGN discs - I. Production and growth

NASA Astrophysics Data System (ADS)

McKernan, B.; Ford, K. E. S.; Lyra, W.; Perets, H. B.

2012-09-01

Here we propose a mechanism for efficiently growing intermediate mass black holes (IMBH) in discs around supermassive black holes. Stellar mass objects can efficiently agglomerate when facilitated by the gas disc. Stars, compact objects and binaries can migrate, accrete and merge within discs around supermassive black holes. While dynamical heating by cusp stars excites the velocity dispersion of nuclear cluster objects (NCOs) in the disc, gas in the disc damps NCO orbits. If gas damping dominates, NCOs remain in the disc with circularized orbits and large collision cross-sections. IMBH seeds can grow extremely rapidly by collisions with disc NCOs at low relative velocities, allowing for super-Eddington growth rates. Once an IMBH seed has cleared out its feeding zone of disc NCOs, growth of IMBH seeds can become dominated by gas accretion from the active galactic nucleus (AGN) disc. However, the IMBH can migrate in the disc and expand its feeding zone, permitting a super-Eddington accretion rate to continue. Growth of IMBH seeds via NCO collisions is enhanced by a pile-up of migrators. We highlight the remarkable parallel between the growth of IMBH in AGN discs with models of giant planet growth in protoplanetary discs. If an IMBH becomes massive enough it can open a gap in the AGN disc. IMBH migration in AGN discs may stall, allowing them to survive the end of the AGN phase and remain in galactic nuclei. Our proposed mechanisms should be more efficient at growing IMBH in AGN discs than the standard model of IMBH growth in stellar clusters. Dynamical heating of disc NCOs by cusp stars is transferred to the gas in an AGN disc helping to maintain the outer disc against gravitational instability. Model predictions, observational constraints and implications are discussed in a companion paper (Paper II).

Optic Nerve Head Development in Healthy Infants and Children Using Handheld Spectral-Domain Optical Coherence Tomography.

PubMed

Patel, Aarti; Purohit, Ravi; Lee, Helena; Sheth, Viral; Maconachie, Gail; Papageorgiou, Eleni; McLean, Rebecca J; Gottlob, Irene; Proudlock, Frank A

2016-10-01

To determine feasibility of optic nerve head (ONH) imaging and to characterize ONH development in full-term infants without sedation using handheld spectral-domain optical coherence tomography (SD OCT). Prospective cross-sectional study. Three hundred fifty-two children aged between 1 day and 13 years. All participants were imaged using handheld SD OCT without sedation during a single scan session. The percentage of successful scans was calculated. Interexaminer reproducibility and differences between right and left eyes were assessed using intraclass correlation coefficients (ICCs). Images were analyzed using ImageJ software. The developmental trajectories over time for ONH parameters were calculated using fractional polynomial modelling. Disc and cup diameter (expressed as distance in micrometers and visual angle in degrees), cup depth, Bruch's membrane opening-minimum rim width (BMO-MRW), retinal thickness, and retinal nerve fiber layer (RNFL; 1700 μm and 6° from the disc center). On average, 70% of participants were imaged successfully. Interexaminer reliability was excellent (ICC, >0.89) for diametric and retinal thickness parameters. Right and left eyes were similar for diametric measurements (ICC, >0.79), but more variable for nasal BMO-MRW, RNFL, and retinal thickness. The mean disc and cup diameter increase by 30% and 40%, respectively, between birth and 13 years of age when expressed as a distance measure, but remained constant (at 5°-5.5° and 2°, respectively) when expressed as a visual angle with reference to the eye nodal point. The peripapillary temporal RNFL demonstrated a marked initial decrease of nearly 35% between birth and approximately 18 months of age. This was followed by a slow increase up to 12 years of age when measured at 1700 μm from the disc center, although there was little change when measured at 6° from the disc center. We demonstrated feasibility of handheld SD OCT imaging of the ONH in full-term infants and children without anaesthesia or sedation. This is the first in vivo handheld SD OCT study to describe the development of ONH parameters during the critical early years of visual maturation. Our results provide a normative database for use in routine practice and further studies of ONH pathologic features. Copyright © 2016 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

The effect of parental factors in children with large cup-to-disc ratios.

PubMed

Park, Hae-Young Lopilly; Ha, Min Ji; Shin, Sun Young

2017-01-01

To investigate large cup-to-disc ratios (CDR) in children and to determine the relationship between parental CDR and clinical characteristics associated with glaucoma. Two hundred thirty six children aged 6 to 12 years with CDR ≥ 0.6 were enrolled in this study. Subjects were classified into two groups based on parental CDR: disc suspect children with disc suspect (CDR ≥0.6) parents and disc suspect children without disc suspect parents. Ocular variables were compared between the two groups. Of the 236 disc suspect children, 100 (42.4%) had at least one disc suspect parent. Intraocular pressure (IOP) was higher in disc suspect children with disc suspect parents (16.52±2.66 mmHg) than in disc suspect children without disc suspect parents (14.38±2.30 mmHg, p = 0.023). In the group with disc suspect parents, vertical CDR significantly correlated with IOP (R = -0.325, p = 0.001), average retinal nerve fiber layer (RNFL) thickness (R = -0.319, p = 0.001), rim area (R = -0.740, p = 0.001), and cup volume (R = 0.499, p = 0.001). However, spherical equivalent (R = 0.333, p = 0.001), AL (R = -0.223, p = 0.009), and disc area (R = 0.325, p = 0.001) significantly correlated with vertical CDR in disc suspect children without disc suspect parents, in contrast to those with disc suspect parents. Larger vertical CDR was associated with the presence of disc suspect parents (p = 0.001), larger disc area (p = 0.001), thinner rim area (p = 0.001), larger average CDR (p = 0.001), and larger cup volume (p = 0.021). Family history of large CDR was a significant factor associated with large vertical CDR in children. In children with disc suspect parents, there were significant correlations between IOP and average RNFL thickness and vertical CDR.

Effects of disc warping on the inclination evolution of star-disc-binary systems

NASA Astrophysics Data System (ADS)

Zanazzi, J. J.; Lai, Dong

2018-07-01

Several recent studies have suggested that circumstellar discs in young stellar binaries may be driven into misalignement with their host stars due to the secular gravitational interactions between the star, disc, and the binary companion. The disc in such systems is twisted/warped due to the gravitational torques from the oblate central star and the external companion. We calculate the disc warp profile, taking into account the bending wave propagation and viscosity in the disc. We show that for typical protostellar disc parameters, the disc warp is small, thereby justifying the `flat-disc' approximation adopted in previous theoretical studies. However, the viscous dissipation associated with the small disc warp/twist tends to drive the disc towards alignment with the binary or the central star. We calculate the relevant time-scales for the alignment. We find that the alignment is effective for sufficiently cold discs with strong external torques, especially for systems with rapidly rotating stars, but is ineffective for the majority of the star-disc-binary systems. Viscous warp-driven alignment may be necessary to account for the observed spin-orbit alignment in multiplanet systems if these systems are accompanied by an inclined binary companion.

Simulating Dynamic Equilibria: A Class Experiment

NASA Astrophysics Data System (ADS)

Harrison, John A.; Buckley, Paul D.

2000-08-01

A first-order reversible reaction is simulated on an overhead projector using small coins or discs. A simulation is carried out in which initially there are 24 discs representing reactant A and none representing reactant B. At the end of each minute half of the reactant A discs get converted to reactant B, and one quarter of the reactant B discs get converted to reactant A discs. Equilibrium is established with 8 A discs and 16 B discs, and no further net change is observed as the simulation continues. Another simulation beginning with 48 A discs and 0 B discs leads at equilibrium to 16 A discs and 32 B discs. These results illustrate how dynamic equilibria are established and allow the introduction of the concept of an equilibrium constant. Le Châtelier's principle is illustrated by further simulations.

Gas turbine sealing apparatus

DOEpatents

Wiebe, David J; Wessell, Brian J; Ebert, Todd; Beeck, Alexander; Liang, George; Marussich, Walter H

2013-02-19

A gas turbine includes forward and aft rows of rotatable blades, a row of stationary vanes between the forward and aft rows of rotatable blades, an annular intermediate disc, and a seal housing apparatus. The forward and aft rows of rotatable blades are coupled to respective first and second portions of a disc/rotor assembly. The annular intermediate disc is coupled to the disc/rotor assembly so as to be rotatable with the disc/rotor assembly during operation of the gas turbine. The annular intermediate disc includes a forward side coupled to the first portion of the disc/rotor assembly and an aft side coupled to the second portion of the disc/rotor assembly. The seal housing apparatus is coupled to the annular intermediate disc so as to be rotatable with the annular intermediate disc and the disc/rotor assembly during operation of the gas turbine.

Probing the structure of the gas in the Milky Way through X-ray high-resolution spectroscopy

NASA Astrophysics Data System (ADS)

Gatuzz, Efraín; Churazov, Eugene

2018-02-01

We have developed a new X-ray absorption model, called IONeq, which computes the optical depth τ(E) simultaneously for ions of all abundant elements, assuming ionization equilibrium and taking into account turbulent broadening. We use this model to analyse the interstellar medium (ISM) absorption features in the Milky Way for a sample of 18 Galactic (LMXBs) and 42 extragalactic sources (mainly Blazars). The absorbing ISM was modelled as a combination of three components/phases - neutral (T ≲ 1 × 104 K), warm (T ˜ 5 × 104 K) and hot (T ˜ 2 × 106 K). We found that the spatial distribution of both, neutral and warm components, are difficult to describe using smooth profiles due to non-uniform distribution of the column densities over the sky. For the hot phase we used a combination of a flattened disc and a halo, finding comparable column densities for both spatial components, of the order of ˜6-7 × 1018 cm-2, although this conclusion depends on the adopted parametrization. If the halo component has sub-solar abundance Z, then the column density has to be scaled up by a factor of Z_{⊙}/Z. The vertically integrated column densities of the disc components suggest the following mass fractions for these three ISM phases in the Galactic disc: neutral ˜ 89 per cent, warm ˜ 8 per cent and hot ˜ 3 per cent components, respectively. The constraints on the radial distribution of the halo component of the hot component are weak.

Manipulator having thermally conductive rotary joint for transferring heat from a test specimen

DOEpatents

Haney, S.J.; Stulen, R.H.; Toly, N.F.

1983-05-03

A manipulator for rotatably moving a test specimen in an ultra-high vacuum chamber includes a translational unit movable in three mutually perpendicular directions. A manipulator frame is rigidly secured to the translational unit for rotatably supporting a rotary shaft. A first copper disc is rigidly secured to an end of the rotary shaft for rotary movement within the vacuum chamber. A second copper disc is supported upon the first disc. The second disc receives a cryogenic cold head and does not rotate with the first disc. The second disc receives a cryogenic cold head and does not rotate with the first disc. A sapphire plate is interposed between the first and second discs to prevent galling of the copper material while maintaining high thermal conductivity between the first and second discs. A spring is disposed on the shaft to urge the second disc toward the first disc and compressingly engage the interposed sapphire plate. A specimen mount is secured to the first disc for rotation within the vacuum chamber. The specimen maintains high thermal conductivity with the second disc receiving the cryogenic transfer line.

Linking hydrodynamic complexity to delta smelt (Hypomesus transpacificus) distribution in the San Francisco Estuary, USA

USGS Publications Warehouse

Bever, Aaron J.; MacWilliams, Michael L.; Herbold, Bruce; Brown, Larry R.; Feyrer, Frederick V.

2016-01-01

Long-term fish sampling data from the San Francisco Estuary were combined with detailed three dimensional hydrodynamic modeling to investigate the relationship between historical fish catch and hydrodynamic complexity. Delta Smelt catch data at 45 stations from the Fall Midwater Trawl (FMWT) survey in the vicinity of Suisun Bay were used to develop a quantitative catch-based station index. This index was used to rank stations based on historical Delta Smelt catch. The correlations between historical Delta Smelt catch and 35 quantitative metrics of environmental complexity were evaluated at each station. Eight metrics of environmental conditions were derived from FMWT data and 27 metrics were derived from model predictions at each FMWT station. To relate the station index to conceptual models of Delta Smelt habitat, the metrics were used to predict the station ranking based on the quantified environmental conditions. Salinity, current speed, and turbidity metrics were used to predict the relative ranking of each station for Delta Smelt catch. Including a measure of the current speed at each station improved predictions of the historical ranking for Delta Smelt catch relative to similar predictions made using only salinity and turbidity. Current speed was also found to be a better predictor of historical Delta Smelt catch than water depth. The quantitative approach developed using the FMWT data was validated using the Delta Smelt catch data from the San Francisco Bay Study. Complexity metrics in Suisun Bay were-evaluated during 2010 and 2011. This analysis indicated that a key to historical Delta Smelt catch is the overlap of low salinity, low maximum velocity, and low Secchi depth regions. This overlap occurred in Suisun Bay during 2011, and may have contributed to higher Delta Smelt abundance in 2011 than in 2010 when the favorable ranges of the metrics did not overlap in Suisun Bay.

Relationship among fish assemblages and main-channel-border physical habitats in the unimpounded Upper Mississippi River

USGS Publications Warehouse

Barko, V.A.; Herzog, D.P.; Hrabik, R.A.; Scheibe, J.S.

2004-01-01

Large rivers worldwide have been altered by the construction and maintenance of navigation channels, which include extensive bank revetments, wing dikes, and levees. Using 7 years of Long-Term Resource Monitoring Program (LTRMP) data collected from the unimpounded upper Mississippi River, we investigated assemblages in two main-channel-border physical habitats-those with wing dikes and those without wing dikes. Fishes were captured using daytime electrofishing, mini-fyke netting, large hoop netting, and small hoop netting. Our objectives were to (1) assess associations among fish species richness, physical measurements, and main-channel-border physical habitats using stepwise multiple regression and indicator variables; (2) identify abundant adult and young-of-year (age-0) families in both physical habitats to further investigate assemblage composition; and (3) calculate standardized species richness estimates within each physical habitat for adult and age-0 fishes to provide additional information on community structure. We found species richness was greater at wing dikes for both adult and age-0 fishes when compared with main channel borders. Stepwise multiple regression revealed significant relationships between adult species richness and passive gear deployment (e.g,, hoop nets and mini-fyke nets), physical habitat type, and river elevation, as well as interactions between physical habitat and passive gears, and physical habitat and transparency (i.e., Secchi depth). This model explained 56% of the variance in adult species richness. Approximately 15% of the variation in age-0 species richness was explained by the sample period, sample date, transparency, physical habitat, and depth of gear deployment. Long-term impacts of river modifications on fishes have not been well documented in many large river systems and warrant further study. The findings from this study provide baseline ecological information on fish assemblages using main channel borders in the unimpounded upper Mississippi River, information that will aid managers making channel maintenance decisions in large river systems.

On the diversity and statistical properties of protostellar discs

NASA Astrophysics Data System (ADS)

Bate, Matthew R.

2018-04-01

We present results from the first population synthesis study of protostellar discs. We analyse the evolution and properties of a large sample of protostellar discs formed in a radiation hydrodynamical simulation of star cluster formation. Due to the chaotic nature of the star formation process, we find an enormous diversity of young protostellar discs, including misaligned discs, and discs whose orientations vary with time. Star-disc interactions truncate discs and produce multiple systems. Discs may be destroyed in dynamical encounters and/or through ram-pressure stripping, but reform by later gas accretion. We quantify the distributions of disc mass and radii for protostellar ages up to ≈105 yr. For low-mass protostars, disc masses tend to increase with both age and protostellar mass. Disc radii range from of order 10 to a few hundred au, grow in size on time-scales ≲ 104 yr, and are smaller around lower mass protostars. The radial surface density profiles of isolated protostellar discs are flatter than the minimum mass solar nebula model, typically scaling as Σ ∝ r-1. Disc to protostar mass ratios rarely exceed two, with a typical range of Md/M* = 0.1-1 to ages ≲ 104 yr and decreasing thereafter. We quantify the relative orientation angles of circumstellar discs and the orbit of bound pairs of protostars, finding a preference for alignment that strengths with decreasing separation. We also investigate how the orientations of the outer parts of discs differ from the protostellar and inner disc spins for isolated protostars and pairs.

Novel localized heating technique on centrifugal microfluidic disc with wireless temperature monitoring system.

PubMed

Joseph, Karunan; Ibrahim, Fatimah; Cho, Jongman

2015-01-01

Recent advances in the field of centrifugal microfluidic disc suggest the need for electrical interface in the disc to perform active biomedical assays. In this paper, we have demonstrated an active application powered by the energy harvested from the rotation of the centrifugal microfluidic disc. A novel integration of power harvester disc onto centrifugal microfluidic disc to perform localized heating technique is the main idea of our paper. The power harvester disc utilizing electromagnetic induction mechanism generates electrical energy from the rotation of the disc. This contributes to the heat generation by the embedded heater on the localized heating disc. The main characteristic observed in our experiment is the heating pattern in relative to the rotation of the disc. The heating pattern is monitored wirelessly with a digital temperature sensing system also embedded on the disc. Maximum temperature achieved is 82 °C at rotational speed of 2000 RPM. The technique proves to be effective for continuous heating without the need to stop the centrifugal motion of the disc.

Linear analysis of the evolution of nearly polar low-mass circumbinary discs

NASA Astrophysics Data System (ADS)

Lubow, Stephen H.; Martin, Rebecca G.

2018-01-01

In a recent paper Martin & Lubow showed through simulations that an initially tilted disc around an eccentric binary can evolve to polar alignment in which the disc lies perpendicular to the binary orbital plane. We apply linear theory to show both analytically and numerically that a nearly polar aligned low-mass circumbinary disc evolves to polar alignment and determine the alignment time-scale. Significant disc evolution towards the polar state around moderately eccentric binaries can occur for typical protostellar disc parameters in less than a typical disc lifetime for binaries with orbital periods of order 100 yr or less. Resonant torques are much less effective at truncating the inner parts of circumbinary polar discs than the inner parts of coplanar discs. For polar discs, they vanish for a binary eccentricity of unity. The results agree with the simulations in showing that discs can evolve to a polar state. Circumbinary planets may then form in such discs and reside on polar orbits.

A new in vivo animal model to create intervertebral disc degeneration characterized by MRI, radiography, CT/discogram, biochemistry, and histology.

PubMed

Zhou, HaoWei; Hou, ShuXun; Shang, WeiLin; Wu, WenWen; Cheng, Yao; Mei, Fang; Peng, BaoGan

2007-04-15

A new in vivo sheep model was developed that produced disc degeneration through the injection of 5-bromodeoxyuridine (BrdU) into the intervertebral disc. This process was studied using magnetic resonance imaging (MRI), radiography, CT/discogram, histology, and biochemistry. To develop a sheep model of intervertebral disc degeneration that more faithfully mimics the pathologic hallmarks of human intervertebral disc degeneration. Recent studies have shown age-related alterations in proteoglycan structure and organization in human intervertebral discs. An animal model that involves the use of age-related changes in disc cells can be beneficial over other more invasive degenerative models that involves directly damaging the matrix of disc tissue. Twelve sheep were injected with BrdU or vehicle (phosphate-buffered saline) into the central region of separate lumbar discs. Intact discs were used as controls. At the 2-, 6-, 10-, and 14-week time points, discs underwent MRI, radiography, histology, and biochemical analyses. A CT/discogram study was performed at the 14-week time point. MRI demonstrated a progressive loss of T2-weighted signal intensity at BrdU-injected discs over the 14-week study period. Radiograph findings included osteophyte and disc space narrowing formed by 10 weeks post-BrdU treatment. CT discography demonstrated internal disc disruption in several BrdU-treated discs at the 14-week time point. Histology showed a progressive loss of the normal architecture and cell density of discs from the 2-week time point to the 14-week time point. A progressive loss of cell proliferation capacity, water content, and proteoglycans was also documented. BrdU injection into the central region of sheep discs resulted in degeneration of intervertebral discs. This progressive, degenerative process was confirmed using MRI, histology, and by observing changes in biochemistry. Degeneration occurred in a manner that was similar to that observed in human disc degeneration.

Neurologic outcome after thoracolumbar partial lateral corpectomy for intervertebral disc disease in 72 dogs.

PubMed

Salger, Florian; Ziegler, Luisa; Böttcher, Irene Christine; Oechtering, Gerhard; Böttcher, Peter; Flegel, Thomas

2014-07-01

To determine neurologic outcome and factors influencing outcome after thoracolumbar partial lateral corpectomy (PLC) in dogs with intervertebral disc disease (IVDD) causing ventral spinal cord compression. Retrospective case series. Dogs with IVDD (n = 72; 87 PLC). Dogs with IVDD between T9 and L5 were included if treated by at least 1 PLC. Exclusion criteria were: previous spinal surgery, combination of PLC with another surgical procedure. Neurologic outcome was assessed by: (1) modified Frankel score (MFS) based on neurologic examinations at 4 time points (before surgery, immediately after PLC, at discharge and 4 weeks after PLC); and (2) owner questionnaire. The association of the following factors with neurologic outcome was analyzed: age, body weight, duration of current neurologic dysfunction (acute, chronic), IVDD localization, breed (chondrodystrophic, nonchondrodystrophic), number of PLCs, degree of presurgical spinal cord compression and postsurgical decompression, slot depth, presurgical MFS. Presurgical spinal cord compression was determined by CT myelography (71 dogs) or MRI (1 dog), whereas postsurgical decompression and slot depth were determined on CT myelography (69 dogs). MFS was improved in 18.7%, 31.7%, and 64.2% of dogs at the 3 postsurgical assessments, whereas it was unchanged in 62.6%, 52.8%, and 32.0% at corresponding time points. Based on owner questionnaire, 91.4% of dogs were ambulatory 6 months postsurgically with 74.5% having a normal gait. Most improvement in neurologic function developed within 6 months after surgery. Presurgical MFS was the only variable significantly associated with several neurologic outcome measurements (P < .01). PLC is an option for decompression in ventrally compressing thoracolumbar IVDD. Prognosis is associated with presurgical neurologic condition. © Copyright 2014 by The American College of Veterinary Surgeons.

Investigation of Product Performance of Al-Metal Matrix Composites Brake Disc using Finite Element Analysis

NASA Astrophysics Data System (ADS)

Fatchurrohman, N.; Marini, C. D.; Suraya, S.; Iqbal, AKM Asif

2016-02-01

The increasing demand of fuel efficiency and light weight components in automobile sectors have led to the development of advanced material parts with improved performance. A specific class of MMCs which has gained a lot of attention due to its potential is aluminium metal matrix composites (Al-MMCs). Product performance investigation of Al- MMCs is presented in this article, where an Al-MMCs brake disc is analyzed using finite element analysis. The objective is to identify the potentiality of replacing the conventional iron brake disc with Al-MMCs brake disc. The simulation results suggested that the MMCs brake disc provided better thermal and mechanical performance as compared to the conventional cast iron brake disc. Although, the Al-MMCs brake disc dissipated higher maximum temperature compared to cast iron brake disc's maximum temperature. The Al-MMCs brake disc showed a well distributed temperature than the cast iron brake disc. The high temperature developed at the ring of the disc and heat was dissipated in circumferential direction. Moreover, better thermal dissipation and conduction at brake disc rotor surface played a major influence on the stress. As a comparison, the maximum stress and strain of Al-MMCs brake disc was lower than that induced on the cast iron brake disc.

Are Collapsed Cervical Discs Amenable to Total Disc Arthroplasty?: Analysis of Prospective Clinical Data With 2-Year Follow Up.

PubMed

Patwardhan, Avinash G; Carandang, Gerard; Voronov, Leonard I; Havey, Robert M; Paul, Gary A; Lauryssen, Carl; Coric, Domagoj; Dimmig, Thomas; Musante, David

2016-12-15

Analysis of prospectively collected radiographic data. To investigate the influence of preoperative index-level range of motion (ROM) and disc height on postoperative ROM after cervical total disc arthroplasty (TDA) using compressible disc prostheses. Clinical studies demonstrate benefits of motion preservation over fusion; however, questions remain unanswered as to which preoperative factors have the ability to identify patients who are most likely to have good postoperative motion, which is the primary rationale for TDA. We analyzed prospectively collected data from a single-arm, multicenter study with 2-year follow up of 30 patients with 48 implanted levels. All received compressible cervical disc prostheses of 6 mm-height (M6C, Spinal Kinetics, Sunnyvale, CA). The influence of index-level preoperative disc height and ROM (each with two levels: below-median and above-median) on postoperative ROM was analyzed using 2 x 2 ANOVA. We further analyzed the radiographic outcomes of a subset of discs with preoperative height less than 3 mm, the so-called "collapsed" discs. Shorter (3.0 ± 0.4 mm) discs were significantly less mobile preoperatively than taller (4.4 ± 0.5 mm) discs (6.7° vs. 10.5°, P = 0.01). The postoperative ROM did not differ between the shorter and taller discs (5.6° vs. 5.0°, P = 0.63). Tall discs that were less mobile preoperatively had significantly smaller postoperative ROM than short discs with above-median preoperative mobility (P < 0.05). The "collapsed discs" (n = 8) were less mobile preoperatively compared with all discs combined (5.1° vs. 8.6°, P < 0.01). These discs were distracted to more than two times the preoperative height, from 2.6 to 5.7 mm, and had significantly greater postoperative ROM than all discs combined (7.6° vs. 5.3°, P < 0.05). We observed a significant interaction between preoperative index-level disc height and ROM in influencing postoperative ROM. Although limited by small sample size, the results suggest discs with preoperative height less than 3 mm may be amenable to disc arthroplasty using compressible disc prostheses. 2.

CT morphometry of adult thoracic intervertebral discs.

PubMed

Fletcher, Justin G R; Stringer, Mark D; Briggs, Christopher A; Davies, Tilman M; Woodley, Stephanie J

2015-10-01

Despite being commonly affected by degenerative disorders, there are few data on normal thoracic intervertebral disc dimensions. A morphometric analysis of adult thoracic intervertebral discs was, therefore, undertaken. Archival computed tomography scans of 128 recently deceased individuals (70 males, 58 females, 20-79 years) with no known spinal pathology were analysed to determine thoracic disc morphometry and variations with disc level, sex and age. Reliability was assessed by intraclass correlation coefficients (ICCs). Anterior and posterior intervertebral disc heights and axial dimensions were significantly greater in men (anterior disc height 4.0±1.4 vs 3.6±1.3 mm; posterior disc height 3.6±0.90 vs 3.4±0.93 mm; p<0.01). Disc heights and axial dimensions at T4-5 were similar or smaller than at T2-3, but thereafter increased caudally (mean anterior disc height T4-5 and T10-11, 2.7±0.7 and 5.4±1.2 mm, respectively, in men; 2.6±0.8 and 5.1±1.3 mm, respectively, in women; p<0.05). Except at T2-3, anterior disc height decreased with advancing age and anteroposterior and transverse disc dimensions increased; posterior and middle disc heights and indices of disc shape showed no consistent statistically significant changes. Most parameters showed substantial to almost perfect agreement for intra- and inter-rater reliability. Thoracic disc morphometry varies significantly and consistently with disc level, sex and age. This study provides unique reference data on adult thoracic intervertebral disc morphometry, which may be useful when interpreting pathological changes and for future biomechanical and functional studies.

Quantitating Human Optic Disc Topography

NASA Astrophysics Data System (ADS)

Graebel, William P.; Cohan, Bruce E.; Pearch, Andrew C.

1980-07-01

A method is presented for quantitatively expressing the topography of the human optic disc, applicable in a clinical setting to the diagnosis and management of glaucoma. Pho-tographs of the disc illuminated by a pattern of fine, high contrast parallel lines are digitized. From the measured deviation of the lines as they traverse the disc surface, disc topography is calculated, using the principles of optical sectioning. The quantitators applied to express this topography have the the following advantages : sensitivity to disc shape; objectivity; going beyond the limits of cup-disc ratio estimates and volume calculations; perfect generality in a mathematical sense; an inherent scheme for determining a non-subjective reference frame to compare different discs or the same disc over time.

Asymmetric MHD outflows/jets from accreting T Tauri stars

NASA Astrophysics Data System (ADS)

Dyda, S.; Lovelace, R. V. E.; Ustyugova, G. V.; Lii, P. S.; Romanova, M. M.; Koldoba, A. V.

2015-06-01

Observations of jets from young stellar objects reveal the asymmetric outflows from some sources. A large set of 2.5D magnetohydrodynamic simulations was carried out for axisymmetric viscous/diffusive disc accretion to rotating magnetized stars for the purpose of assessing the conditions where the outflows are asymmetric relative to the equatorial plane. We consider initial magnetic fields that are symmetric about the equatorial plane and consist of a radially distributed field threading the disc (disc field) and a stellar dipole field. (1) For pure disc-fields the symmetry or asymmetry of the outflows is affected by the mid-plane plasma β of the disc. For discs with small plasma β, outflows are symmetric to within 10 per cent over time-scales of hundreds of inner disc orbits. For higher β discs, the coupling of the upper and lower coronal plasmas is broken, and quasi-periodic field motion leads to asymmetric episodic outflows. (2) Accreting stars with a stellar dipole field and no disc-field exhibit episodic, two component outflows - a magnetospheric wind and an inner disc wind. Both are characterized by similar velocity profiles but the magnetospheric wind has densities ≳ 10 times that of the disc wind. (3) Adding a disc field parallel to the stellar dipole field enhances the magnetospheric winds but suppresses the disc wind. (4) Adding a disc field which is antiparallel to the stellar dipole field in the disc suppresses the magnetospheric and disc winds. Our simulations reproduce some key features of observations of asymmetric outflows of T Tauri stars.

Ranges of Cervical Intervertebral Disc Deformation During an In Vivo Dynamic Flexion–Extension of the Neck

PubMed Central

Yu, Yan; Mao, Haiqing; Li, Jing-Sheng; Tsai, Tsung-Yuan; Cheng, Liming; Wood, Kirkham B.; Li, Guoan; Cha, Thomas D.

2017-01-01

While abnormal loading is widely believed to cause cervical spine disc diseases, in vivo cervical disc deformation during dynamic neck motion has not been well delineated. This study investigated the range of cervical disc deformation during an in vivo functional flexion–extension of the neck. Ten asymptomatic human subjects were tested using a combined dual fluoroscopic imaging system (DFIS) and magnetic resonance imaging (MRI)-based three-dimensional (3D) modeling technique. Overall disc deformation was determined using the changes of the space geometry between upper and lower endplates of each intervertebral segment (C3/4, C4/5, C5/6, and C6/7). Five points (anterior, center, posterior, left, and right) of each disc were analyzed to examine the disc deformation distributions. The data indicated that between the functional maximum flexion and extension of the neck, the anterior points of the discs experienced large changes of distraction/compression deformation and shear deformation. The higher level discs experienced higher ranges of disc deformation. No significant difference was found in deformation ranges at posterior points of all the discs. The data indicated that the range of disc deformation is disc level dependent and the anterior region experienced larger changes of deformation than the center and posterior regions, except for the C6/7 disc. The data obtained from this study could serve as baseline knowledge for the understanding of the cervical spine disc biomechanics and for investigation of the biomechanical etiology of disc diseases. These data could also provide insights for development of motion preservation surgeries for cervical spine. PMID:28334358

Ranges of Cervical Intervertebral Disc Deformation During an In Vivo Dynamic Flexion-Extension of the Neck.

PubMed

Yu, Yan; Mao, Haiqing; Li, Jing-Sheng; Tsai, Tsung-Yuan; Cheng, Liming; Wood, Kirkham B; Li, Guoan; Cha, Thomas D

2017-06-01

While abnormal loading is widely believed to cause cervical spine disc diseases, in vivo cervical disc deformation during dynamic neck motion has not been well delineated. This study investigated the range of cervical disc deformation during an in vivo functional flexion-extension of the neck. Ten asymptomatic human subjects were tested using a combined dual fluoroscopic imaging system (DFIS) and magnetic resonance imaging (MRI)-based three-dimensional (3D) modeling technique. Overall disc deformation was determined using the changes of the space geometry between upper and lower endplates of each intervertebral segment (C3/4, C4/5, C5/6, and C6/7). Five points (anterior, center, posterior, left, and right) of each disc were analyzed to examine the disc deformation distributions. The data indicated that between the functional maximum flexion and extension of the neck, the anterior points of the discs experienced large changes of distraction/compression deformation and shear deformation. The higher level discs experienced higher ranges of disc deformation. No significant difference was found in deformation ranges at posterior points of all the discs. The data indicated that the range of disc deformation is disc level dependent and the anterior region experienced larger changes of deformation than the center and posterior regions, except for the C6/7 disc. The data obtained from this study could serve as baseline knowledge for the understanding of the cervical spine disc biomechanics and for investigation of the biomechanical etiology of disc diseases. These data could also provide insights for development of motion preservation surgeries for cervical spine.

The presence of pleiotrophin in the human intervertebral disc is associated with increased vascularization: an immunohistologic study.

PubMed

Johnson, William E B; Patterson, Angela M; Eisenstein, Stephen M; Roberts, Sally

2007-05-20

An immunohistological study of surgical specimens of human intervertebral disc. To examine the presence of pleiotrophin in diseased or damaged intervertebral disc tissue and the association between its presence and the extent of tissue vascularization and innervation. Increased levels of pleiotrophin, a growth and differentiation factor that is active in various pathophysiologic processes, including angiogenesis, has been associated with osteoarthritic changes of human articular cartilage. The association between pleiotrophin expression and pathologic conditions of the human intervertebral disc is unknown. Specimens of human lumbar intervertebral discs, obtained following surgical discectomy, were divided into 3 groups: non-degenerated discs (n = 7), degenerated discs (n = 6), and prolapsed discs (n = 11). Serial tissue sections of each specimen were immunostained to determine the presence of pleiotrophin, blood vessels (CD34-positive endothelial cells), and nerves (neurofilament 200 kDa [NF200]-positive nerve fibers). Pleiotrophin immunoreactivity was seen in disc cells, endothelial cells, and in the extracellular matrix in most specimens of intervertebral disc but was most prevalent in vascularized tissue in prolapsed discs. There was a significant correlation between the presence of pleiotrophin-positive disc cells and that of CD34-positive blood vessels. NF200-positive nerves were seen in vascularized areas of more degenerated discs, but nerves did not appear to codistribute with blood vessels or pleiotrophin positivity in prolapsed discs. Pleiotrophin is present in pathologic human intervertebral discs, and its prevalence and distribution suggest that it may play a role in neovascularization of diseased or damaged disc tissue.

MRI evaluation of spontaneous intervertebral disc degeneration in the alpaca cervical spine.

PubMed

Stolworthy, Dean K; Bowden, Anton E; Roeder, Beverly L; Robinson, Todd F; Holland, Jacob G; Christensen, S Loyd; Beatty, Amanda M; Bridgewater, Laura C; Eggett, Dennis L; Wendel, John D; Stieger-Vanegas, Susanne M; Taylor, Meredith D

2015-12-01

Animal models have historically provided an appropriate benchmark for understanding human pathology, treatment, and healing, but few animals are known to naturally develop intervertebral disc degeneration. The study of degenerative disc disease and its treatment would greatly benefit from a more comprehensive, and comparable animal model. Alpacas have recently been presented as a potential large animal model of intervertebral disc degeneration due to similarities in spinal posture, disc size, biomechanical flexibility, and natural disc pathology. This research further investigated alpacas by determining the prevalence of intervertebral disc degeneration among an aging alpaca population. Twenty healthy female alpacas comprised two age subgroups (5 young: 2-6 years; and 15 older: 10+ years) and were rated according to the Pfirrmann-grade for degeneration of the cervical intervertebral discs. Incidence rates of degeneration showed strong correlations with age and spinal level: younger alpacas were nearly immune to developing disc degeneration, and in older animals, disc degeneration had an increased incidence rate and severity at lower cervical levels. Advanced disc degeneration was present in at least one of the cervical intervertebral discs of 47% of the older alpacas, and it was most common at the two lowest cervical intervertebral discs. The prevalence of intervertebral disc degeneration encourages further investigation and application of the lower cervical spine of alpacas and similar camelids as a large animal model of intervertebral disc degeneration. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Seasonal and interannual variability in the taxonomic composition and production dynamics of phytoplankton assemblages in Crater Lake, Oregon

USGS Publications Warehouse

C. David, McIntire; Larson, Gary L.; Truitt, Robert E.

2007-01-01

Taxonomic composition and production dynamics of phytoplankton assemblages in Crater Lake, Oregon, were examined during time periods between 1984 and 2000. The objectives of the study were (1) to investigate spatial and temporal patterns in species composition, chlorophyll concentration, and primary productivity relative to seasonal patterns of water circulation; (2) to explore relationships between water column chemistry and the taxonomic composition of the phytoplankton; and (3) to determine effects of primary and secondary consumers on the phytoplankton assemblage. An analysis of 690 samples obtained on 50 sampling dates from 14 depths in the water column found a total of 163 phytoplankton taxa, 134 of which were identified to genus and 101 were identified to the species or variety level of classification. Dominant species by density or biovolume included Nitzschia gracilis, Stephanodiscus hantzschii, Ankistrodesmus spiralis, Mougeotia parvula, Dinobryon sertularia, Tribonema affine, Aphanocapsa delicatissima, Synechocystis sp., Gymnodinium inversum, and Peridinium inconspicuum. When the lake was thermally stratified in late summer, some of these species exhibited a stratified vertical distribution in the water column. A cluster analysis of these data also revealed a vertical stratification of the flora from the middle of the summer through the early fall. Multivariate test statistics indicated that there was a significant relationship between the species composition of the phytoplankton and a corresponding set of chemical variables measured for samples from the water column. In this case, concentrations of total phosphorus, ammonia, total Kjeldahl nitrogen, and alkalinity were associated with interannual changes in the flora; whereas pH and concentrations of dissolved oxygen, orthophosphate, nitrate, and silicon were more closely related to spatial variation and thermal stratification. The maximum chlorophyll concentration when the lake was thermally stratified in August and September was usually between depths of 100 m and 120 m. In comparison, the depth of maximum primary production ranged from 60 m to 80 m at this time of year. Regression analysis detected a weak negative relationship between chlorophyll concentration and Secchi disk depth, a measure of lake transparency. However, interannual changes in chlorophyll concentration and the species composition of the phytoplankton could not be explained by the removal of the septic field near Rim Village or by patterns of upwelling from the deep lake. An alternative trophic hypothesis proposes that the productivity of Crater Lake is controlled primarily by long-term patterns of climatic change that regulate the supply of allochthonous nutrients.

Applicability of Aerial Green LiDAR to a Large River in the Western United States

NASA Astrophysics Data System (ADS)

Conner, J. T.; Welcker, C. W.; Cooper, C.; Faux, R.; Butler, M.; Nayegandhi, A.

2013-12-01

In October 2012, aerial green LiDAR data were collected in the Snake River (within Idaho and Oregon) to test this emerging technology in a large river with poor water clarity. Six study areas (total of 30 river miles spread out over 250 river miles) were chosen to represent a variety of depths, channel types, and surface conditions to test the accuracy, depth penetration, data density of aerial green LiDAR. These characteristics along with cost and speed of acquisition were compared to other bathymetric survey techniques including rod surveys (total station and RTK-GPS), single-beam sonar, and multibeam echosounder (MBES). The green LiDAR system typically measured returns from the riverbed through 1-2 meters of water, which was less than one Secchi depth. However, in areas with steep banks or aquatic macrophytes, LiDAR returns from the riverbed were less frequent or non-existent. In areas of good return density, depths measured from green LiDAR data corresponded well with previously collected data sets from traditional bathymetric survey techniques. In such areas, the green LiDAR point density was much higher than both rod and single beam sonar surveys, yet lower than MBES. The green LiDAR survey was also collected more efficiently than all other methods. In the Snake River, green LiDAR does not provide a method to map the entire riverbed as it only receives bottom returns in shallow water, typically at the channel margins. However, green LiDAR does provide survey data that is an excellent complement to MBES, which is more effective at surveying the deeper portions of the channel. In some cases, the green LiDAR was able to provide data in areas that the MBES could not, often due to issues with navigating the survey boat in shallow water. Even where both MBES and green LiDAR mapped the river bottom, green LiDAR often provides more accurate data through a better angle of incidence and less shadowing than the MBES survey. For one MBES survey in 2013, the green LiDAR data was used to create a map of shallow hazards to be avoided during the survey for the safety of the crew and the MBES equipment. While green LiDAR does not provide a single solution to all large river surveying problems, when combined with MBES it allows for more complete, more efficient, and safer surveys in a large river.

Are 3-D coronal mass ejection parameters from single-view observations consistent with multiview ones?

NASA Astrophysics Data System (ADS)

Lee, Harim; Moon, Y.-J.; Na, Hyeonock; Jang, Soojeong; Lee, Jae-Ok

2015-12-01

To prepare for when only single-view observations are available, we have made a test whether the 3-D parameters (radial velocity, angular width, and source location) of halo coronal mass ejections (HCMEs) from single-view observations are consistent with those from multiview observations. For this test, we select 44 HCMEs from December 2010 to June 2011 with the following conditions: partial and full HCMEs by SOHO and limb CMEs by twin STEREO spacecraft when they were approximately in quadrature. In this study, we compare the 3-D parameters of the HCMEs from three different methods: (1) a geometrical triangulation method, the STEREO CAT tool developed by NASA/CCMC, for multiview observations using STEREO/SECCHI and SOHO/LASCO data, (2) the graduated cylindrical shell (GCS) flux rope model for multiview observations using STEREO/SECCHI data, and (3) an ice cream cone model for single-view observations using SOHO/LASCO data. We find that the radial velocities and the source locations of the HCMEs from three methods are well consistent with one another with high correlation coefficients (≥0.9). However, the angular widths by the ice cream cone model are noticeably underestimated for broad CMEs larger than 100° and several partial HCMEs. A comparison between the 3-D CME parameters directly measured from twin STEREO spacecraft and the above 3-D parameters shows that the parameters from multiview are more consistent with the STEREO measurements than those from single view.

Morphological and kinematic evolution of three interacting coronal mass ejections of 2011 February 13-15

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mishra, Wageesh; Srivastava, Nandita, E-mail: wageesh@prl.res.in

2014-10-10

During 2011 February 13-15, three Earth-directed coronal mass ejections (CMEs) launched in succession were recorded as limb CMEs by STEREO/SECCHI coronagraphs (COR). These CMEs provided an opportunity to study their geometrical and kinematic evolution from multiple vantage points. In this paper, we examine the differences in geometrical evolution of slow and fast CMEs during their propagation in the heliosphere. We also study their interaction and collision using STEREO/SECCHI COR and Heliospheric Imager (HI) observations. We have found evidence of interaction and collision between the CMEs of February 15 and 14 in the COR2 and HI1 field of view (FOV), respectively,more » while the CME of February 14 caught up with the CME of February 13 in the HI2 FOV. By estimating the true mass of these CMEs and using their pre- and post-collision dynamics, the momentum and energy exchange between them during the collision phase are studied. We classify the nature of the observed collision between the CMEs of February 14 and 15 as inelastic, reaching close to the elastic regime. Relating imaging observations with in situ WIND measurements at L1, we find that the CMEs move adjacent to each other after their collision in the heliosphere and are recognized as distinct structures in in situ observations. Our results highlight the significance of HI observations in studying CME-CME collision for the purpose of improved space weather forecasting.« less

Archival-grade optical disc design and international standards

NASA Astrophysics Data System (ADS)

Fujii, Toru; Kojyo, Shinichi; Endo, Akihisa; Kodaira, Takuo; Mori, Fumi; Shimizu, Atsuo

2015-09-01

Optical discs currently on the market exhibit large variations in life span among discs, making them unsuitable for certain business applications. To assess and potentially mitigate this problem, we performed accelerated degradation testing under standard ISO conditions, determined the probable disc failure mechanisms, and identified the essential criteria necessary for a stable disc composition. With these criteria as necessary conditions, we analyzed the physical and chemical changes that occur in the disc components, on the basis of which we determined technological measures to reduce these degradation processes. By applying these measures to disc fabrication, we were able to develop highly stable optical discs.

Thermal analysis of disc brakes using finite element method

NASA Astrophysics Data System (ADS)

Jaenudin, Jamari, J.; Tauviqirrahman, M.

2017-01-01

Disc brakes are components of a vehicle that serve to slow or stop the rotation of the wheel. This paper discusses the phenomenon of heat distribution on the brake disc during braking. Heat distribution on the brake disc is caused by kinetic energy changing into mechanical energy. Energy changes occur during the braking process due to friction between the surface of the disc and a disc pad. The temperature resulting from this friction rises high. This thermal analysis on brake discs is aimed to evaluate the performance of an electric car in the braking process. The aim of this study is to analyze the thermal behavior of the brake discs using the Finite Element Method (FEM) through examining the heat distribution on the brake disc using 3-D modeling. Results obtained from the FEM reflect the effects of high heat due to the friction between the disc pad with the disc rotor. Results of the simulation study are used to identify the effect of the heat distribution that occurred during the braking process.

Manipulator having thermally conductive rotary joint for transferring heat from a test specimen

DOEpatents

Haney, Steven J.; Stulen, Richard H.; Toly, Norman F.

1985-01-01

A manipulator for rotatably moving a test specimen in an ultra-high vacuum chamber includes a translational unit movable in three mutually perpendicular directions. A manipulator frame is rigidly secured to the translational unit for rotatably supporting a rotary shaft. A first copper disc is rigidly secured to an end of the rotary shaft for rotary movement within the vacuum chamber. A second copper disc is supported upon the first disc. The second disc receives a cryogenic cold head and does not rotate with the first disc. A sapphire plate is interposed between the first and second discs to prevent galling of the copper material while maintaining high thermal conductivity between the first and second discs. A spring is disposed on the shaft to urge the second disc toward the first disc and compressingly engage the interposed sapphire plate. A specimen mount is secured to the first disc for rotation within the vacuum chamber. The specimen maintains high thermal conductivity with the second disc receiving the cryogenic transfer line.

Circumplanetary discs around young giant planets: a comparison between core-accretion and disc instability

NASA Astrophysics Data System (ADS)

Szulágyi, J.; Mayer, L.; Quinn, T.

2017-01-01

Circumplanetary discs can be found around forming giant planets, regardless of whether core accretion or gravitational instability built the planet. We carried out state-of-the-art hydrodynamical simulations of the circumplanetary discs for both formation scenarios, using as similar initial conditions as possible to unveil possible intrinsic differences in the circumplanetary disc mass and temperature between the two formation mechanisms. We found that the circumplanetary discs' mass linearly scales with the circumstellar disc mass. Therefore, in an equally massive protoplanetary disc, the circumplanetary discs formed in the disc instability model can be only a factor of 8 more massive than their core-accretion counterparts. On the other hand, the bulk circumplanetary disc temperature differs by more than an order of magnitude between the two cases. The subdiscs around planets formed by gravitational instability have a characteristic temperature below 100 K, while the core-accretion circumplanetary discs are hot, with temperatures even greater than 1000 K when embedded in massive, optically thick protoplanetary discs. We explain how this difference can be understood as the natural result of the different formation mechanisms. We argue that the different temperatures should persist up to the point when a full-fledged gas giant forms via disc instability; hence, our result provides a convenient criterion for observations to distinguish between the two main formation scenarios by measuring the bulk temperature in the planet vicinity.

Wear behaviour of the couple polyethylene Ti6Al4V: Effects of the metallic surface preparation and nitrogen implantation

NASA Astrophysics Data System (ADS)

Martinella, R.; Giovanardi, S.; Palombarini, G.; Corchia, M.; Delogu, P.; Giorgi, R.; Tosello, C.

The wear behaviour improvement of the tribological couple Ti6Al4V-UHMWPE is of great interest to the medical field. Wear tests were carried out in water on a reciprocating UHMWPE annulus on implanted Ti6Al4V disc tribotestcr, with loads and velocities simulating those of hip joints. A comparison of wear behaviours was also carried out between untreated Ti6Al4V samples and Ti6Al4V subjected to a special lapping procedure. UHMWPE worn against ion-implanted and especially lapped Ti alloy showed the lowest wear rate, while, the highest (about one order of magnitude) was shown by the UHMWPE against untreated Ti6Al4V samples. XPS and AES surface analyses were carried out on metallic discs to examine the chemical composition of the surface before wear tests. Moreover depth distribution of nitrogen in implanted samples was determined using the same techniques. SEM observations displayed a polyethylene transfer film on all metallic surfaces, particularly on untreated Ti6Al4V samples. A discussion about uselessness of more conventional surface treatments for the Ti alloy is also reported.

Kinematics of a selectively constrained radiolucent anterior lumbar disc: comparisons to hybrid and circumferential fusion.

PubMed

Daftari, Tapan K; Chinthakunta, Suresh R; Ingalhalikar, Aditya; Gudipally, Manasa; Hussain, Mir; Khalil, Saif

2012-10-01

Despite encouraging clinical outcomes of one-level total disc replacements reported in literature, there is no compelling evidence regarding the stability following two-level disc replacement and hybrid constructs. The current study is aimed at evaluating the multidirectional kinematics of a two-level disc arthroplasty and hybrid construct with disc replacement adjacent to rigid circumferential fusion, compared to two-level fusion using a novel selectively constrained radiolucent anterior lumbar disc. Nine osteoligamentous lumbosacral spines (L1-S1) were tested in the following sequence: 1) Intact; 2) One-level disc replacement; 3) Hybrid; 4) Two-level disc replacement; and 5) Two-level fusion. Range of motion (at both implanted and adjacent level), and center of rotation in sagittal plane were recorded and calculated. At the level of implantation, motion was restored when one-level disc replacement was used but tended to decrease with two-level disc arthroplasty. The findings also revealed that both one-level and two-level disc replacement and hybrid constructs did not significantly change adjacent level kinematics compared to the intact condition, whereas the two-level fusion construct demonstrated a significant increase in flexibility at the adjacent level. The location of center of rotation in the sagittal plane at L4-L5 for the one-level disc replacement construct was similar to that of the intact condition. The one-level disc arthroplasty tended to mimic a motion profile similar to the intact spine. However, the two-level disc replacement construct tended to reduce motion and clinical stability of a two-level disc arthroplasty requires additional investigation. Hybrid constructs may be used as a surgical alternative for treating two-level lumbar degenerative disc disease. Published by Elsevier Ltd.

Polar alignment of a protoplanetary disc around an eccentric binary II: Effect of binary and disc parameters

NASA Astrophysics Data System (ADS)

Martin, Rebecca G.; Lubow, Stephen H.

2018-06-01

In a recent paper Martin & Lubow showed that a circumbinary disc around an eccentric binary can undergo damped nodal oscillations that lead to the polar (perpendicular) alignment of the disc relative to the binary orbit. The disc angular momentum vector aligns to the eccentricity vector of the binary. We explore the robustness of this mechanism for a low mass disc (0.001 of the binary mass) and its dependence on system parameters by means of hydrodynamic disc simulations. We describe how the evolution depends upon the disc viscosity, temperature, size, binary mass ratio, orbital eccentricity and inclination. We compare results with predictions of linear theory. We show that polar alignment of a low mass disc may occur over a wide range of binary-disc parameters. We discuss the application of our results to the formation of planetary systems around eccentric binary stars.

Proto-planetary disc evolution and dispersal

NASA Astrophysics Data System (ADS)

Rosotti, Giovanni Pietro

2015-05-01

Planets form from gas and dust discs in orbit around young stars. The timescale for planet formation is constrained by the lifetime of these discs. The properties of the formed planetary systems depend thus on the evolution and final dispersal of the discs, which is the main topic of this thesis. Observations reveal the existence of a class of discs called "transitional", which lack dust in their inner regions. They are thought to be the last stage before the complete disc dispersal, and hence they may provide the key to understanding the mechanisms behind disc evolution. X-ray photoevaporation and planet formation have been studied as possible physical mechanisms responsible for the final dispersal of discs. However up to now, these two phenomena have been studied separately, neglecting any possible feedback or interaction. In this thesis we have investigated what is the interplay between these two processes. We show that the presence of a giant planet in a photo-evaporating disc can significantly shorten its lifetime, by cutting the inner regions from the mass reservoir in the exterior of the disc. This mechanism produces transition discs that for a given mass accretion rate have larger holes than in models considering only X-ray photo-evaporation, constituting a possible route to the formation of accreting transition discs with large holes. These discs are found in observations and still constitute a puzzle for the theory. Inclusion of the phenomenon called "thermal sweeping", a violent instability that can destroy a whole disc in as little as 10 4 years, shows that the outer disc left can be very short-lived (depending on the X-ray luminosity of the star), possibly explaining why very few non accreting transition discs are observed. However the mechanism does not seem to be efficient enough to reconcile with observations. In this thesis we also show that X-ray photo-evaporation naturally explains the observed correlation between stellar masses and accretion rates and is therefore the ideal candidate for driving disc evolution. Another process that can influence discs is a close encounter with another star. In this thesis we develop a model to study the effect of stellar dynamics in the natal stellar cluster on the discs, following for the first time at the same time the stellar dynamics together with the evolution of the discs. We find that, although close encounters with stars are unlikely to change significantly the mass of a disc, they can change substantially its size, hence imposing an upper limit on the observed disc radii. Finally, we investigated in this thesis whether discs can be reformed after their dispersal. If a star happens to be in a region that is currently forming stars, it can accrete material from the interstellar medium. This mechanism may result in the production of "second generation" discs such that in a given star forming region a few percent of stars may still possess a disc, in tentative agreement with observations of so called "old accretors", which are difficult to explain within the current paradigm of disc evolution and dispersal.

Orbital alignment of circumbinary planets that form in misaligned circumbinary discs: the case of Kepler-413b

NASA Astrophysics Data System (ADS)

Pierens, A.; Nelson, R. P.

2018-06-01

Although most of the circumbinary planets detected by the Kepler spacecraft are on orbits that are closely aligned with the binary orbital plane, the systems Kepler-413 and Kepler-453 exhibit small misalignments of ˜2.5°. One possibility is that these planets formed in a circumbinary disc whose midplane was inclined relative to the binary orbital plane. Such a configuration is expected to lead to a warped and twisted disc, and our aim is to examine the inclination evolution of planets embedded in these discs. We employed 3D hydrodynamical simulations that examine the disc response to the presence of a modestly inclined binary with parameters that match the Kepler-413 system, as a function of disc parameters and binary inclinations. The discs all develop slowly varying warps, and generally display very small amounts of twist. Very slow solid body precession occurs because a large outer disc radius is adopted. Simulations of planets embedded in these discs resulted in the planet aligning with the binary orbit plane for disc masses close to the minimum mass solar nebular, such that nodal precession of the planet was controlled by the binary. For higher disc masses, the planet maintains near coplanarity with the local disc midplane. Our results suggest that circumbinary planets born in tilted circumbinary discs should align with the binary orbit plane as the disc ages and loses mass, even if the circumbinary disc remains misaligned from the binary orbit. This result has important implications for understanding the origins of the known circumbinary planets.

Audiovisual Bounce-Inducing Effect: Attention Alone Does Not Explain Why the Discs Are Bouncing

ERIC Educational Resources Information Center

Grassi, Massimo; Casco, Clara

2009-01-01

Two discs moving from opposite points in space, overlapping and stopping at the other disc's starting point, can be seen as either bouncing or streaming through each other. With silent displays, observers report the discs as streaming, whereas if a sound is played when the discs touch each other, observers report the discs as bouncing. The origin…

Reduction of turbulent skin-friction drag by oscillating discs

NASA Astrophysics Data System (ADS)

Wise, Daniel; Ricco, Pierre

2013-11-01

A new drag-reduction method, based on the active technique proposed by Ricco & Hahn (2013), i.e. steadily rotating flush-mounted discs, is studied by DNS. The effect of sinusoidally oscillating discs on the turbulent channel-flow drag is investigated at Reτ = 180 , based on the friction velocity of the stationary-wall case and the half channel height. A parametric investigation on the disc diameter, tip velocity and oscillation period yielded a maximum drag reduction of 18.5%. Regions of net power saved, calculated by considering the power spent to enforce the disc motion against the viscous resistance of the fluid, are found to reach up to 6.5% for low disc tip velocities. Significantly, the characteristic time-scale for the oscillating disc forcing is double that for the steadily rotating discs, representing a further step towards industrial implementation. The oscillating disc forcing, similar to the steadily rotating disc forcing, creates streamwise-elongated structures between the discs. These structures - largely unaffected by the periodic wall forcing and persisting throughout the entire period of the oscillation - are the main contributor to the additional Reynolds stresses term created by the disc forcing, and are important for the drag reduction mechanism.

Formation of neuronal pathways in the imaginal discs of Drosophila melanogaster.

PubMed

Jan, Y N; Ghysen, A; Christoph, I; Barbel, S; Jan, L Y

1985-09-01

We have followed the formation of neuronal pathways in different imaginal discs of Drosophila. The pattern is highly reproducible for a given disc type but distinct for each type of discs: in leg discs, several neurons are present before metamorphosis and provide two major pathways that are joined by later neurons; in the wing and haltere discs, a few pairs of neurons appear after the onset of metamorphosis and pioneer the major pathways; in antenna discs, no pioneers are detected before massive neuronal differentiation begins. The mechanisms used for axonal guidance seem common to all discs, and the differences between discs can be accounted for simply by differences in the arrangement and birth time of pioneer neurons. Different subsets of pioneer neurons are deleted by mutations such as scute and engrailed.

The relationship between quantitative measures of disc height and disc signal intensity with Pfirrmann score of disc degeneration.

PubMed

Salamat, Sara; Hutchings, John; Kwong, Clemens; Magnussen, John; Hancock, Mark J

2016-01-01

To assess the relationship between quantitative measures of disc height and signal intensity with the Pfirrmann disc degeneration scoring system and to test the inter-rater reliability of the quantitative measures. Participants were 76 people who had recently recovered from their last episode of acute low back pain and underwent MRI scan on a single 3T machine. At all 380 lumbar discs, quantitative measures of disc height and signal intensity were made by 2 independent raters and compared to Pfirrmann scores from a single radiologist. For quantitative measures of disc height and signal intensity a "raw" score and 2 adjusted ratios were calculated and the relationship with Pfirrmann scores was assessed. The inter-tester reliability of quantitative measures was also investigated. There was a strong linear relationship between quantitative disc signal intensity and Pfirrmann scores for grades 1-4, but not for grades 4 and 5. For disc height only, Pfirrmann grade 5 had significantly reduced disc height compared to all other grades. Results were similar regardless of whether raw or adjusted scores were used. Inter-rater reliability for the quantitative measures was excellent (ICC > 0.97). Quantitative measures of disc signal intensity were strongly related to Pfirrmann scores from grade 1 to 4; however disc height only differentiated between grade 4 and 5 Pfirrmann scores. Using adjusted ratios for quantitative measures of disc height or signal intensity did not significantly alter the relationship with Pfirrmann scores.

Effects of disc mid-plane evolution on CO snowline location

NASA Astrophysics Data System (ADS)

Panić, O.; Min, M.

2017-05-01

Temperature changes in the planet forming disc mid-planes carry important physico-chemical consequences, such as the effect on the locations of the condensation fronts of molecules - the snowlines. Snowlines impose major chemical gradients and possibly foster grain growth. The aim of this paper is to understand how disc mid-plane temperature changes with gas and dust evolution, and identify trends that may influence planet formation or allow to constrain disc evolution observationally. We calculate disc temperature, hydrostatic equilibrium and dust settling in a mutually consistent way from a grid of disc models at different stages of gas loss, grain growth and hole opening. We find that the CO snowline location depends very strongly on disc properties. The CO snowline location migrates closer to the star for increasing degrees of gas dispersal and dust growth. Around a typical A-type star, the snowline can be anywhere between several tens and a few hundred au, depending on the disc properties such as gas mass and grain size. In fact, gas loss is as efficient as dust evolution in settling discs, and flat discs may be gas-poor counterparts of flared discs. Our results, in the context of different pre-main-sequence evolution of the luminosity in low- and intermediate-mass stars suggest very different thermal (and hence chemical) histories in these two types of discs. Discs of T Tauri stars settle and cool down, while discs of Herbig Ae stars may remain rather warm throughout the pre-main sequence.

Kozai-Lidov disc instability

NASA Astrophysics Data System (ADS)

Lubow, Stephen H.; Ogilvie, Gordon I.

2017-08-01

Recent results by Martin et al. showed in 3D smoothed particle hydrodynamics simulations that tilted discs in binary systems can be unstable to the development of global, damped Kozai-Lidov (KL) oscillations in which the discs exchange tilt for eccentricity. We investigate the linear stability of KL modes for tilted inviscid discs under the approximations that the disc eccentricity is small and the disc remains flat. By using 1D equations, we are able to probe regimes of large ratios of outer to inner disc edge radii that are realistic for binary systems of hundreds of astronomical unit separations and are not easily probed by multidimensional simulations. For order unity binary mass ratios, KL instability is possible for a window of disc aspect ratios H/r in the outer parts of a disc that roughly scale as (nb/n)2 ≲ H/r ≲ nb/n, for binary orbital frequency nb and orbital frequency n at the disc outer edge. We present a framework for understanding the zones of instability based on the determination of branches of marginally unstable modes. In general, multiple growing eccentric KL modes can be present in a disc. Coplanar apsidal-nodal precession resonances delineate instability branches. We determine the range of tilt angles for unstable modes as a function of disc aspect ratio. Unlike the KL instability for free particles that involves a critical (minimum) tilt angle, disc instability is possible for any non-zero tilt angle depending on the disc aspect ratio.

Coaxial line configuration for microwave power transmission study of YBa2Cu3O(7-delta) thin films

NASA Technical Reports Server (NTRS)

Chorey, C. M.; Miranda, F. A.; Bhasin, K. B.

1991-01-01

Microwave transmission measurements through YBa2Cu3O(7-delta) (YBCO) high-transition-temperature superconducting thin films on lanthanum aluminate (LaAlO3) have been performed in a coaxial line at 10 GHz. LaAlO3 substrates were ultrasonically machined into washer-shaped discs, polished, and coated with laser-ablated YBCO. These samples were mounted in a 50-ohm coaxial air line to form a short circuit. The power transmitted through the films as a function of temperature was used to calculate the normal state conductivity and the magnetic penetration depth for the films.

Predicting potentially toxigenic Pseudo-nitzschia blooms in the Chesapeake Bay

NASA Astrophysics Data System (ADS)

Anderson, Clarissa R.; Sapiano, Mathew R. P.; Prasad, M. Bala Krishna; Long, Wen; Tango, Peter J.; Brown, Christopher W.; Murtugudde, Raghu

2010-11-01

Harmful algal blooms are now recognized as a significant threat to the Chesapeake Bay as they can severely compromise the economic viability of important recreational and commercial fisheries in the largest estuary of the United States. This study describes the development of empirical models for the potentially domoic acid-producing Pseudo-nitzschia species complex present in the Bay, developed from a 22-year time series of cell abundance and concurrent measurements of hydrographic and chemical properties. Using a logistic Generalized Linear Model (GLM) approach, model parameters and performance were compared over a range of Pseudo-nitzschia bloom thresholds relevant to toxin production by different species. Small-threshold blooms (≥10 cells mL -1) are explained by time of year, location, and variability in surface values of phosphate, temperature, nitrate plus nitrite, and freshwater discharge. Medium- (100 cells mL -1) to large- threshold (1000 cells mL -1) blooms are further explained by salinity, silicic acid, dissolved organic carbon, and light attenuation (Secchi) depth. These predictors are similar to other models for Pseudo-nitzschia blooms on the west coast, suggesting commonalities across ecosystems. Hindcasts of bloom probabilities at a 19% bloom prediction point yield a Heidke Skill Score of ~53%, a Probability of Detection ˜ 75%, a False Alarm Ratio of ˜ 52%, and a Probability of False Detection ˜9%. The implication of possible future changes in Baywide nutrient stoichiometry on Pseudo-nitzschia blooms is discussed.

Phytoplankton biomass and composition in a well-flushed, sub-tropical estuary: The contrasting effects of hydrology, nutrient loads and allochthonous influences.

PubMed

Hart, J A; Phlips, E J; Badylak, S; Dix, N; Petrinec, K; Mathews, A L; Green, W; Srifa, A

2015-12-01

The primary objective of this study was to examine trends in phytoplankton biomass and species composition under varying nutrient load and hydrologic regimes in the Guana Tolomato Matanzas estuary (GTM), a well-flushed sub-tropical estuary located on the northeast coast of Florida. The GTM contains both regions of significant human influence and pristine areas with only modest development, providing a test case for comparing and contrasting phytoplankton community dynamics under varying degrees of nutrient load. Water temperature, salinity, Secchi disk depth, nutrient concentrations and chlorophyll concentrations were determined on a monthly basis from 2002 to 2012 at three representative sampling sites in the GTM. In addition, microscopic analyses of phytoplankton assemblages were carried out monthly for a five year period from 2005 through 2009 at all three sites. Results of this study indicate that phytoplankton biomass and composition in the GTM are strongly influenced by hydrologic factors, such as water residence times and tidal exchanges of coastal waters, which in turn are affected by shifts in climatic conditions, most prominently rainfall levels. These influences are exemplified by the observation that the region of the GTM with the longest water residence times but lowest nutrient loads exhibited the highest phytoplankton peaks of autochthonous origin. The incursion of a coastal bloom of the toxic dinoflagellate Karenia brevis into the GTM in 2007 demonstrates the potential importance of allochthonous influences on the ecosystem. Copyright © 2015 Elsevier Ltd. All rights reserved.

Lake St. Clair zooplankton: Evidence for post-Dreissena changes

USGS Publications Warehouse

David, Katherine A.; Davis, Bruce M.; Hunter, R. Douglas

2009-01-01

We surveyed the zooplankton of Lake St. Clair at 12 sites over ten dates from May to October 2000. Mean zooplankton density by site and date was 168.6 individuals/L, with Dreissena spp. veligers the most abundant taxon at 122.7 individuals/L. Rotifers, copepods, and cladocerans were far lower in mean abundance than in the early 1970s (rotifers, 20.9/L; copepods, 18.1/L; and cladocerans, 6.8/L). Species richness of zooplankton taxa in 2000 was 147, which was virtually unchanged from that of the first reported survey in 1894. Overall, the decline in abundance was greatest for rotifers (-90%) and about equal for cladocerans (-69%) and copepods (-66%). The decrease in abundance of Daphnia spp. was especially dramatic in Canadian waters. The decline in the southeastern region was significant for all three major groups of zooplankton, whereas in the northwestern region the decline was significant only for rotifers. From June to August 2000, Lake St. Clair open waters were numerically dominated by Dreissena spp. veligers, with a reduced abundance of rotifers and crustaceans compared to pre-Dreissena spp. surveys. Mean nutrient concentrations were not different from the 1970s, but Secchi depth (greater) and chlorophyll a concentration (lower) were. Disproportionate reduction in rotifer abundance is consistent with hypotheses implicating direct consumption by settled Dreissena spp. Reduction of crustaceans is likely due to more complex interactions including removal of nauplii as well as resource competition for phytoplankton.

Deteriorating water clarity in shallow waters: Evidence from long term MODIS and in-situ observations

NASA Astrophysics Data System (ADS)

Shi, Kun; Zhang, Yunlin; Zhu, Guangwei; Qin, Boqiang; Pan, Delu

2018-06-01

Water clarity (Secchi disk depth: SDD), as a proxy of water transparency, provides important information on the light availability to the water or lake ecosystem. Shallow lakes have been experienced dramatic environmental and climatic change. This study demonstrated using combination of long-term MODIS and in-situ measurements to track the dynamics of SDD with these environmental and climate changes in shallow water environments. We selected a typical turbid shallow Lake Taihu as our case study. Based on MODIS-Aqua data, an empirical model for estimating SDD was developed and validated. Subsequently, we employed the proposed model to derive the spatial and temporal SDD distribution patterns of Lake Taihu from 2003 to 2015. Combining MODIS-derived SDD time series of 2003-2015 and long-term in-situ SDD observations dated back to 1993, we elucidated SDD long-term variation trends and driving mechanism. Deteriorating water clarity from the long-term SDD observations indicated that Lake Taihu became more and more turbid and water quality was decreasing. Increasing in cyanobacterial bloom area, as a result of decreasing in wind speed and eutrophication, may partially be responsible for the decreasing trend. A predicted future decrease in the wind speed in Lake Taihu region could enhance the formation of cyanobacterial blooms and consequently lead to a further decrease in water clarity. This study suggested that coupling remote sensing monitoring and long-term in-situ observations could provide robust evidence and new insights to elucidate long-term dynamics in aquatic ecosystem evolution.

Liquid-film electron stripper

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gavin, B.F.

1986-12-02

This patent describes an improved liquid-film electron stripper for high intensity heavy ion beams comprising: at least one rotatable disc mounted in a housing, means for rotating the disc, a liquid reservoir operatively connected to the housing, means for directing liquid from the reservoir onto the rotatable disc for forming a film of liquid as liquid is spun from the disc, the disc being configured to define a sharp edge located at one side of the periphery of the disc, and configured to include a flat, smooth radially outer section located adjacent the sharp edge, the liquid being directed ontomore » the flat, smooth section of the disc, the means for directing liquid onto the disc including a nozzle positioned with respect to the disc so that liquid from the nozzle impinges at about a 90/sup 0/ angle with respect to the flat, smooth surface of the disc, and liquid film terminator means located in spaced relation to the disc and approximately perpendicular to a formed liquid film, the terminator means comprising at least one ribbon of material secured to the housing.« less

In Vitro Maturation and In Vivo Integration and Function of an Engineered Cell-Seeded Disc-like Angle Ply Structure (DAPS) for Total Disc Arthroplasty.

PubMed

Martin, J T; Gullbrand, S E; Kim, D H; Ikuta, K; Pfeifer, C G; Ashinsky, B G; Smith, L J; Elliott, D M; Smith, H E; Mauck, R L

2017-11-17

Total disc replacement with an engineered substitute is a promising avenue for treating advanced intervertebral disc disease. Toward this goal, we developed cell-seeded disc-like angle ply structures (DAPS) and showed through in vitro studies that these constructs mature to match native disc composition, structure, and function with long-term culture. We then evaluated DAPS performance in an in vivo rat model of total disc replacement; over 5 weeks in vivo, DAPS maintained their structure, prevented intervertebral bony fusion, and matched native disc mechanical function at physiologic loads in situ. However, DAPS rapidly lost proteoglycan post-implantation and did not integrate into adjacent vertebrae. To address this, we modified the design to include polymer endplates to interface the DAPS with adjacent vertebrae, and showed that this modification mitigated in vivo proteoglycan loss while maintaining mechanical function and promoting integration. Together, these data demonstrate that cell-seeded engineered discs can replicate many characteristics of the native disc and are a viable option for total disc arthroplasty.

Rethinking Black Hole Accretion Discs

NASA Astrophysics Data System (ADS)

Salvesen, Greg

Accretion discs are staples of astrophysics. Tapping into the gravitational potential energy of the accreting material, these discs are highly efficient machines that produce copious radiation and extreme outflows. While interesting in their own right, accretion discs also act as tools to study black holes and directly influence the properties of the Universe. Black hole X-ray binaries are fantastic natural laboratories for studying accretion disc physics and black hole phenomena. Among many of the curious behaviors exhibited by these systems are black hole state transitions -- complicated cycles of dramatic brightening and dimming. Using X-ray observations with high temporal cadence, we show that the evolution of the accretion disc spectrum during black hole state transitions can be described by a variable disc atmospheric structure without invoking a radially truncated disc geometry. The accretion disc spectrum can be a powerful diagnostic for measuring black hole spin if the effects of the disc atmosphere on the emergent spectrum are well-understood; however, properties of the disc atmosphere are largely unconstrained. Using statistical methods, we decompose this black hole spin measurement technique and show that modest uncertainties regarding the disc atmosphere can lead to erroneous spin measurements. The vertical structure of the disc is difficult to constrain due to our ignorance of the contribution to hydrostatic balance by magnetic fields, which are fundamental to the accretion process. Observations of black hole X-ray binaries and the accretion environments near supermassive black holes provide mounting evidence for strong magnetization. Performing numerical simulations of accretion discs in the shearing box approximation, we impose a net vertical magnetic flux that allows us to effectively control the level of disc magnetization. We study how dynamo activity and the properties of turbulence driven by the magnetorotational instability depend on the magnetized state of the gas, spanning weak-to-strong disc magnetization regimes. We also demonstrate that a background poloidal magnetic flux is required to form and sustain a strongly magnetized accretion disc. This thesis motivates the need for understanding how magnetic fields affect the observed spectrum from black hole accretion discs.

Ensuring long-term reliability of the data storage on optical disc

NASA Astrophysics Data System (ADS)

Chen, Ken; Pan, Longfa; Xu, Bin; Liu, Wei

2008-12-01

"Quality requirements and handling regulation of archival optical disc for electronic records filing" is released by The State Archives Administration of the People's Republic of China (SAAC) on its network in March 2007. This document established a complete operative managing process for optical disc data storage in archives departments. The quality requirements of the optical disc used in archives departments are stipulated. Quality check of the recorded disc before filing is considered to be necessary and the threshold of the parameter of the qualified filing disc is set down. The handling regulations for the staffs in the archives departments are described. Recommended environment conditions of the disc preservation, recording, accessing and testing are presented. The block error rate of the disc is selected as main monitoring parameter of the lifetime of the filing disc and three classes pre-alarm lines are created for marking of different quality check intervals. The strategy of monitoring the variation of the error rate curve of the filing discs and moving the data to a new disc or a new media when the error rate of the disc reaches the third class pre-alarm line will effectively guarantee the data migration before permanent loss. Only when every step of the procedure is strictly implemented, it is believed that long-term reliability of the data storage on optical disc for archives departments can be effectively ensured.

How do accretion discs break?

NASA Astrophysics Data System (ADS)

Dogan, Suzan

2016-07-01

Accretion discs are common in binary systems, and they are often found to be misaligned with respect to the binary orbit. The gravitational torque from a companion induces nodal precession in misaligned disc orbits. In this study, we first calculate whether this precession is strong enough to overcome the internal disc torques communicating angular momentum. We compare the disc precession torque with the disc viscous torque to determine whether the disc should warp or break. For typical parameters precession wins: the disc breaks into distinct planes that precess effectively independently. To check our analytical findings, we perform 3D hydrodynamical numerical simulations using the PHANTOM smoothed particle hydrodynamics code, and confirm that disc breaking is widespread and enhances accretion on to the central object. For some inclinations, the disc goes through strong Kozai cycles. Disc breaking promotes markedly enhanced and variable accretion and potentially produces high-energy particles or radiation through shocks. This would have significant implications for all binary systems: e.g. accretion outbursts in X-ray binaries and fuelling supermassive black hole (SMBH) binaries. The behaviour we have discussed in this work is relevant to a variety of astrophysical systems, for example X-ray binaries, where the disc plane may be tilted by radiation warping, SMBH binaries, where accretion of misaligned gas can create effectively random inclinations and protostellar binaries, where a disc may be misaligned by a variety of effects such as binary capture/exchange, accretion after binary formation.

Notochord Cells in Intervertebral Disc Development and Degeneration

PubMed Central

McCann, Matthew R.; Séguin, Cheryle A.

2016-01-01

The intervertebral disc is a complex structure responsible for flexibility, multi-axial motion, and load transmission throughout the spine. Importantly, degeneration of the intervertebral disc is thought to be an initiating factor for back pain. Due to a lack of understanding of the pathways that govern disc degeneration, there are currently no disease-modifying treatments to delay or prevent degenerative disc disease. This review presents an overview of our current understanding of the developmental processes that regulate intervertebral disc formation, with particular emphasis on the role of the notochord and notochord-derived cells in disc homeostasis and how their loss can result in degeneration. We then describe the role of small animal models in understanding the development of the disc and their use to interrogate disc degeneration and associated pathologies. Finally, we highlight essential development pathways that are associated with disc degeneration and/or implicated in the reparative response of the tissue that might serve as targets for future therapeutic approaches. PMID:27252900

Developing NanoFoil-Heated Thin-Film Thermal Battery

DTIC Science & Technology

2013-09-01

buffer discs (in gray) sandwiching the NanoFoil disc (in yellow). Two Microtherm discs (in dark gray) bracketed the sandwich to prevent excessive heat...of the fuse strip with a Microtherm disc. Cathode Electrolyte Anode Microtherm Heat paper NanoFoil Buffer Agilent 34970A 606.5 Nichrome wire Maccor...gray) sandwiching the NanoFoil disc (in yellow). Two Microtherm discs (in dark gray) bracketed the sandwich to prevent excessive heat loss

Is there any relationship between proinflammatory mediator levels in disc material and myelopathy with cervical disc herniation and spondylosis? A non-randomized, prospective clinical study

PubMed Central

Asir, Alparslan; Cetinkal, Ahmet; Gedik, Nursal; Kutlay, Ahmet Murat; Çolak, Ahmet; Kurtar, Sedat; Simsek, Hakan

2007-01-01

The proinflammatory mediator (PIM) levels were assessed in surgically removed samples of herniated cervical intervertebral discs. The objective of this study was to investigate if there is a correlation between the levels of PIMs in disc material and myelopathy associated with cervical intervertebral disc herniation and spondylosis. The role of proinflammatory mediators in the degeneration of intervertebral disc and the inflammatory effects of disc herniations on radicular pain has been previously published. However, the possible relationship between PIMs and myelopathy related to cervical disc herniation and spondylosis has not been investigated before. Thirty-two patients undergoing surgery for cervical disc herniation and spondylosis were investigated. Surgically obtained disc materials, stored at 70°C, were classified into two groups: cervical disc herniation alone or with myelopathy. Biochemical preparation and solid phase enzyme amplified sensitivity immunoassay (ELISIA) analysis of the samples were performed to assess the concentration of mediators in the samples. Very similar values of interleukin-6 were found in both groups whereas the concentrations of mediators were significantly higher in myelopathy group. This study has demonstrated that PIMs are involved in cervical intervertebral disc degeneration with higher concentrations in the samples associated with myelopathy. PMID:17476536

Effect of collagen fibre orientation on intervertebral disc torsion mechanics.

PubMed

Yang, Bo; O'Connell, Grace D

2017-12-01

The intervertebral disc is a complex fibro-cartilaginous material, consisting of a pressurized nucleus pulposus surrounded by the annulus fibrosus, which has an angle-ply structure. Disc injury and degeneration are noted by significant changes in tissue structure and function, which significantly alters stress distribution and disc joint stiffness. Differences in fibre orientation are thought to contribute to changes in disc torsion mechanics. Therefore, the objective of this study was to evaluate the effect of collagen fibre orientation on internal disc mechanics under compression combined with axial rotation. We developed and validated a finite element model (FEM) to delineate changes in disc mechanics due to fibre orientation from differences in material properties. FEM simulations were performed with fibres oriented at [Formula: see text] throughout the disc (uniform by region and fibre layer). The initial model was validated by published experimental results for two load conditions, including [Formula: see text] axial compression and [Formula: see text] axial rotation. Once validated, fibre orientation was rotated by [Formula: see text] or [Formula: see text] towards the horizontal plane, resulting in a decrease in disc joint torsional stiffness. Furthermore, we observed that axial rotation caused a sinusoidal change in disc height and radial bulge, which may be beneficial for nutrient transport. In conclusion, including anatomically relevant fibre angles in disc joint FEMs is important for understanding stress distribution throughout the disc and will be important for understanding potential causes for disc injury. Future models will include regional differences in fibre orientation to better represent the fibre architecture of the native disc.

Toward Understanding the Early Stags of an Impulsively Accelerated Coronal Mass Ejection

DTIC Science & Technology

2010-08-09

B. E., & Howard, R. A . 2009, ApJ, 702, 901 Wood, B. E., Karovska , M., Chen, J., Brueckner, G. E., Cook, J. W., & Howard, R. A . 1999, ApJ, 512, 484...ar X iv :1 00 8. 11 71 v1 [ as tr o- ph .S R ] 6 A ug 2 01 0 Astronomy & Astrophysics manuscript no. bubble c© ESO 2010 August 9, 2010 Toward...understanding the early stages of an impulsively accelerated coronal mass ejection SECCHI observations S. Patsourakos1, A . Vourlidas2, and B. Kliem3,4

Oblique view of the lunar surface taken from Apollo 8 spacecraft

NASA Image and Video Library

1968-12-24

AS08-17-2814 (21-27 Dec. 1968) --- This oblique view of the lunar surface taken from the Apollo 8 spacecraft looking westward across the Sea of Fertility into the Sea of Tranquility shows the terrain the astronauts will see as the approach Apollo Landing Site East 2. The landing site is at the horizon about one-third of the distance from the left to the right photograph margin. The prominent crater in the highlands near the center of the picture is Secchi, about 25 kilometers (15 statute miles) in diameter.

Regression Analysis of Optical Coherence Tomography Disc Variables for Glaucoma Diagnosis.

PubMed

Richter, Grace M; Zhang, Xinbo; Tan, Ou; Francis, Brian A; Chopra, Vikas; Greenfield, David S; Varma, Rohit; Schuman, Joel S; Huang, David

2016-08-01

To report diagnostic accuracy of optical coherence tomography (OCT) disc variables using both time-domain (TD) and Fourier-domain (FD) OCT, and to improve the use of OCT disc variable measurements for glaucoma diagnosis through regression analyses that adjust for optic disc size and axial length-based magnification error. Observational, cross-sectional. In total, 180 normal eyes of 112 participants and 180 eyes of 138 participants with perimetric glaucoma from the Advanced Imaging for Glaucoma Study. Diagnostic variables evaluated from TD-OCT and FD-OCT were: disc area, rim area, rim volume, optic nerve head volume, vertical cup-to-disc ratio (CDR), and horizontal CDR. These were compared with overall retinal nerve fiber layer thickness and ganglion cell complex. Regression analyses were performed that corrected for optic disc size and axial length. Area-under-receiver-operating curves (AUROC) were used to assess diagnostic accuracy before and after the adjustments. An index based on multiple logistic regression that combined optic disc variables with axial length was also explored with the aim of improving diagnostic accuracy of disc variables. Comparison of diagnostic accuracy of disc variables, as measured by AUROC. The unadjusted disc variables with the highest diagnostic accuracies were: rim volume for TD-OCT (AUROC=0.864) and vertical CDR (AUROC=0.874) for FD-OCT. Magnification correction significantly worsened diagnostic accuracy for rim variables, and while optic disc size adjustments partially restored diagnostic accuracy, the adjusted AUROCs were still lower. Axial length adjustments to disc variables in the form of multiple logistic regression indices led to a slight but insignificant improvement in diagnostic accuracy. Our various regression approaches were not able to significantly improve disc-based OCT glaucoma diagnosis. However, disc rim area and vertical CDR had very high diagnostic accuracy, and these disc variables can serve to complement additional OCT measurements for diagnosis of glaucoma.

Gravitational Instabilities in a Protosolar-like Disc

NASA Astrophysics Data System (ADS)

Evans, Mark Graham

2018-02-01

This thesis presents a study of protoplanetary discs around young, low mass protostars. Such discs are believed to be massive enough to develop gravitational instabilities, which subsequently form spiral structures. The dynamical and chemical evolutions of a protosolar-like, gravitationally unstable disc are explored and the spiral structure in the disc is found to shock-heat material. This affects the chemical composition via enhanced desorption rates and endothermic reaction rates and through global mixing of the disc. As a result, the gravitational instability in the model disc leads to transient and permanent changes in the disc chemistry, and also provides a chemically-rich midplane in contrast to simulations of more evolved discs. Secondly, radiative transfer calculations are performed for the dust continuum, and model-tailored grid construction is found to improve the accuracy of the resultant flux images. Continuum observations of the model disc are synthesised and the spiral structure (driven by the gravitational instability) is shown to be readily detectable with ALMA across a range of frequencies, disc inclinations and dust opacities. The derivation of disc mass from the observed flux densities is explored but the method commonly utilised is found to be unreliable and underestimate the disc mass. Therefore, it is concluded that gravitational instabilities could be retrospectively validated in discs previously thought not massive enough to be self-gravitating. Finally, radiative transfer calculations are performed for molecular line transitions. Methods for improving the accuracy of line flux images are explored and the validity of assuming local thermodynamic equilibrium is assessed. Observations of the line fluxes are synthesised without noise and the spiral structure is found to be traced to an extent by all transitions considered, which is not necessarily congruent with the underlying distribution of the molecular species. The disc is seen in absorption in all transitions considered, due to the global mixing of the disc, which suggests absorption features could be a signature of gravitational instability in young protoplanetary discs. The sensitivities required to detect flux originating in spiral features are determined and it is found that a dedicated observation with ALMA should be capable of spatially resolving spiral structure in a Class 0 disc. Whether the spiral structure can be also be determined from spectral features is explored, which is shown to only be reliable with PV diagrams of nearly edge-on discs. The derivation of protostellar mass from PV diagrams is also explored and found to most likely be unreliable for gravitationally unstable discs.

NuSTAR + XMM-Newton monitoring of the neutron star transient AX J1745.6-2901

NASA Astrophysics Data System (ADS)

Ponti, G.; Bianchi, S.; Muñoz-Darias, T.; Mori, K.; De, K.; Rau, A.; De Marco, B.; Hailey, C.; Tomsick, J.; Madsen, K. K.; Clavel, M.; Rahoui, F.; Lal, D. V.; Roy, S.; Stern, D.

2018-01-01

AX J1745.6-2901 is a high-inclination (eclipsing) transient neutron star (NS) low-mass X-ray binary showcasing intense ionized Fe K absorption. We present here the analysis of 11 XMM-Newton and 15 NuSTAR new data sets (obtained between 2013 and 2016), therefore tripling the number of observations of AX J1745.6-2901 in outburst. Thanks to simultaneous XMM-Newton and NuSTAR spectra, we greatly improve on the fitting of the X-ray continuum. During the soft state, the emission can be described by a disc blackbody (kT ∼ 1.1-1.2 keV and inner disc radius rDBB ∼ 14 km), plus hot (kT ∼ 2.2-3.0 keV) blackbody radiation with a small emitting radius (rBB ∼ 0.5 - 0.8 km) likely associated with the boundary layer or NS surface, plus a faint Comptonization component. Imprinted on the spectra are clear absorption features created by both neutral and ionized matter. Additionally, positive residuals suggestive of an emission Fe K α disc line and consistent with relativistic ionized reflection are present during the soft state, while such residuals are not significant during the hard state. The hard-state spectra are characterized by a hard (Γ ∼ 1.9-2.1) power law, showing no evidence for a high energy cut-off (kTe > 60-140 keV) and implying a small optical depth (τ < 1.6). The new observations confirm the previously witnessed trend of exhibiting strong Fe K absorption in the soft state that significantly weakens during the hard state. Optical (GROND) and radio (GMRT) observations suggest for AX J1745.6-2901 a standard broad-band spectral energy distribution as typically observed in accreting NSs.

Nanophase change for data storage applications.

PubMed

Shi, L P; Chong, T C

2007-01-01

Phase change materials are widely used for date storage. The most widespread and important applications are rewritable optical disc and Phase Change Random Access Memory (PCRAM), which utilizes the light and electric induced phase change respectively. For decades, miniaturization has been the major driving force to increase the density. Now the working unit area of the current data storage media is in the order of nano-scale. On the nano-scale, extreme dimensional and nano-structural constraints and the large proportion of interfaces will cause the deviation of the phase change behavior from that of bulk. Hence an in-depth understanding of nanophase change and the related issues has become more and more important. Nanophase change can be defined as: phase change at the scale within nano range of 100 nm, which is size-dependent, interface-dominated and surrounding materials related. Nanophase change can be classified into two groups, thin film related and structure related. Film thickness and clapping materials are key factors for thin film type, while structure shape, size and surrounding materials are critical parameters for structure type. In this paper, the recent development of nanophase change is reviewed, including crystallization of small element at nano size, thickness dependence of crystallization, effect of clapping layer on the phase change of phase change thin film and so on. The applications of nanophase change technology on data storage is introduced, including optical recording such as super lattice like optical disc, initialization free disc, near field, super-RENS, dual layer, multi level, probe storage, and PCRAM including, superlattice-like structure, side edge structure, and line type structure. Future key research issues of nanophase change are also discussed.

Spinal disabilities in military and civil aviators.

PubMed

Taneja, Narinder

2008-12-01

The purpose of this study was to analyze the nature and cause of spinal disabilities among military and civil aircrew in India. Studies suggest that military aircrew may be more prone than nonaviators to develop spinal disabilities. An in-depth analysis of such disabilities can enable policy makers to develop data-driven preventive health programs. Extensive literature search did not reveal even a single study focusing on spinal disabilities in symptomatic aircrew. A case record of each aircrew is maintained at the Institute of Aerospace Medicine, Indian Air Force, Bangalore, India These records were accessed for all aircrew evaluated for spinal disabilities from the year 2000 to 2006. The total data comprises of 239 military and 11 civil aircrew. Most of the military aircrew were from the fighter stream. The spectrum of causes for spinal disabilities ranged from ejection, aircraft accidents to road traffic accidents, and falls. Degenerative disc disease was the leading cause in helicopter and transport pilots, whereas fractures were the predominant category in fighter pilots. A total of 153 vertebral fractures and 190 intervertebral discs were involved. There were significant differences in the age and distribution of this aircrew. Spinal disabilities assume significance for variety of reasons. Firstly, a large number of spinal disabilities caused by vehicular trauma are preventable. Second, they generally entail a prolonged course of recovery. Third, they can result in loss of trained human resources, especially when the individual cannot return to his or her original workspace. This study provides insights into the nature of spinal disabilities in civil and military aviation. Ejection and aircraft accidents remain the leading cause of vertebral fractures. Disc degenerative disease is a cause of concern. Physical conditioning and regular physical exercise may possibly minimize spinal disabilities in susceptible aircrew.

Ocular dimensions in relation to auxological data in a sample of Swedish children aged 4-15 years.

PubMed

Raffa, Lina H; Hellström, Ann; Aring, Eva; Andersson, Susann; Grönlund, Marita Andersson

2014-11-01

The purpose was to characterize normal growth patterns of ocular and optical components and to relate them to auxological data in a sample of Swedish children aged 4-15 years. A prospective cross-sectional study was carried out in 143 Swedish children with a mean age of 9.8 years. Variables including gestational age (GA), weight, length and head circumference (HCF) at birth and at the time of assessment were registered. Visual acuity (VA), cycloplegic refraction and biometric measures were obtained. Palpebral fissure length and inner canthal distance were measured. Optic disc morphology as seen on fundus photographs was analysed. Children born more mature, with male predilection, were found to have deeper anterior and vitreous chamber depths, longer axial lengths and thinner crystalline lens thickness. No correlations were found between ocular biometric measurements and VA or refraction after adjustment for confounding variables. Inner canthal distance was significantly correlated with birth length (p = 0.03), height, weight, BMI and HCF (p = 0.0008, p = 0.0007, p = 0.037, and p = 0.04, respectively) at time of assessment. Total axial length was found to be significantly correlated with GA (p = 0.0226) and length at assessment in girls (p = 0.0084). Right optic disc and rim areas decreased with increasing age (p = 0.0078 and p = 0.0107, respectively); however, optic disc parameters were not dependent on any other variable. These normative values may serve as a basis for the ocular findings and their relationship to auxological data in Caucasian children aged 4-15 years, as well as for future comparison in patients with paediatric ocular pathologies. © 2014 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Enlivening Physics, a Local Video Disc Project.

ERIC Educational Resources Information Center

McInerney, M.

1989-01-01

Describes how to make and use an inexpensive video disc of physics demonstrations. Discusses the background, production of the disc, subject of the disc including angular momentum, "monkey and the hunter" experiment, Doppler shift, pressure of a constant volume of gas thermometer, and wave effects, and using the disc in classroom. (YP)

Dependence of optic disc parameters on disc area according to Heidelberg Retina Tomograph: Part II.

NASA Astrophysics Data System (ADS)

Machekhin, V.; Manaenkova, G.; Bondarenko, O.

2007-05-01

With the help of Heidelberg Retina Tomograph (HRT-II) optic disc parameters in 211 eyes of 115 healthy patients with refraction Em +/- 3,0 D and 96 eyes of 72 patients with myopia 3,5-14,0 D without any signs of glaucoma were studied. Analysis of optic disc parameters were carried out in 5 groups of patients according to disc area: less than 1,5 mm2, 1,5- 2,5 mm2, 2,5-3,0 mm2, 3,0-3,5 mm2 and more than 3,5 mm2. An accurate depending on disc area was revealed for all optic disc parameters in all sectors, which was manifested by increasing cup disc and rim disc (area and volume) and other parameters. We consider it is necessary to use the proper tables for right interpretation of received data for early diagnosis of glaucoma.

Automated volumetric evaluation of stereoscopic disc photography

PubMed Central

Xu, Juan; Ishikawa, Hiroshi; Wollstein, Gadi; Bilonick, Richard A; Kagemann, Larry; Craig, Jamie E; Mackey, David A; Hewitt, Alex W; Schuman, Joel S

2010-01-01

PURPOSE: To develop a fully automated algorithm (AP) to perform a volumetric measure of the optic disc using conventional stereoscopic optic nerve head (ONH) photographs, and to compare algorithm-produced parameters with manual photogrammetry (MP), scanning laser ophthalmoscope (SLO) and optical coherence tomography (OCT) measurements. METHODS: One hundred twenty-two stereoscopic optic disc photographs (61 subjects) were analyzed. Disc area, rim area, cup area, cup/disc area ratio, vertical cup/disc ratio, rim volume and cup volume were automatically computed by the algorithm. Latent variable measurement error models were used to assess measurement reproducibility for the four techniques. RESULTS: AP had better reproducibility for disc area and cup volume and worse reproducibility for cup/disc area ratio and vertical cup/disc ratio, when the measurements were compared to the MP, SLO and OCT methods. CONCLUSION: AP provides a useful technique for an objective quantitative assessment of 3D ONH structures. PMID:20588996

Composite flywheels with rim and hub

NASA Astrophysics Data System (ADS)

Ikegami, K.; Igarashi, J.-I.; Shiratori, E.

The possibility of obtaining a flywheel of high energy density by increasing both rotating speed and moment of inertia of the disc is investigated. As the starting point of the search process for such a flywheel, a glass cloth-laminated disc with a hole at the center is considered. The rotating speed of the disc is improved by reinforcing the central hole of the disc with the same material as that of the disc. The large moment of inertia is obtained by attaching a rim around the disc. The rim is moulded by winding carbon fiber around it. This rim also has the usual 'hoop' effect which prevents a reduction of the rotating speed of the disc because of the additional moment of inertia of the rim. The shape of the disc having a high energy density is numerically sought by varying the dimensions of the hub and the rim of the disc, and an optimal shape is proposed.

[The Autocad system for planimetric study of the optic disc in glaucoma: technique and reproducibility study].

PubMed

Sánchez Pérez, A; Honrubia López, F M; Larrosa Poves, J M; Polo Llorens, V; Melcon Sánchez-Frieras, B

2001-09-01

To develop a lens planimetry technique for the optic disc using AutoCAD. To determine variability magnitude of the optic disc morphological measurements. We employed AutoCAD R.14.0 Autodesk: image acquisition, contour delimitation by multiple lines fitting or ellipse adjustment, image sectorialization and measurements quantification (optic disc and excavation, vertical diameters, optic disc area, excavation area, neuroretinal sector area and Beta atrophy area). Intraimage or operator and interimage o total reproducibility was studied by coefficient of variability (CV) (n=10) in normal and myopic optic discs. This technique allows to obtain optic disc measurement in 5 to 10 minutes time. Total or interimage variability of measurements introduced by one observer presents CV range from 1.18-4.42. Operator or intraimage measurement presents CV range from 0.30-4.21. Optic disc contour delimitation by ellipse adjustment achieved better reproducibility results than multiple lines adjustment in all measurements. Computer assisted AutoCAD planimetry is an interactive method to analyse the optic disc, feasible to incorporate to clinical practice. Reproducibility results are comparable to other analyzers in quantification optic disc morphology. Ellipse adjustment improves results in optic disc contours delimitation.

Protoplanetary disc `isochrones' and the evolution of discs in the M˙-Md plane

NASA Astrophysics Data System (ADS)

Lodato, Giuseppe; Scardoni, Chiara E.; Manara, Carlo F.; Testi, Leonardo

2017-12-01

In this paper, we compare simple viscous diffusion models for the disc evolution with the results of recent surveys of the properties of young protoplanetary discs. We introduce the useful concept of 'disc isochrones' in the accretion rate-disc mass plane and explore a set of Monte Carlo realization of disc initial conditions. We find that such simple viscous models can provide a remarkable agreement with the available data in the Lupus star forming region, with the key requirement that the average viscous evolutionary time-scale of the discs is comparable to the cluster age. Our models produce naturally a correlation between mass accretion rate and disc mass that is shallower than linear, contrary to previous results and in agreement with observations. We also predict that a linear correlation, with a tighter scatter, should be found for more evolved disc populations. Finally, we find that such viscous models can reproduce the observations in the Lupus region only in the assumption that the efficiency of angular momentum transport is a growing function of radius, thus putting interesting constraints on the nature of the microscopic processes that lead to disc accretion.

BP Piscium: its flaring disc imaged with SPHERE/ZIMPOL★

NASA Astrophysics Data System (ADS)

de Boer, J.; Girard, J. H.; Canovas, H.; Min, M.; Sitko, M.; Ginski, C.; Jeffers, S. V.; Mawet, D.; Milli, J.; Rodenhuis, M.; Snik, F.; Keller, C. U.

2017-03-01

Whether BP Piscium (BP Psc) is either a pre-main sequence T Tauri star at d ≈ 80 pc, or a post-main sequence G giant at d ≈ 300 pc is still not clear. As a first-ascent giant, it is the first to be observed with a molecular and dust disc. Alternatively, BP Psc would be among the nearest T Tauri stars with a protoplanetary disc (PPD). We investigate whether the disc geometry resembles typical PPDs, by comparing polarimetric images with radiative transfer models. Our Very Large Telescope/Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE)/Zurich IMaging Polarimeter (ZIMPOL) observations allow us to perform polarimetric differential imaging, reference star differential imaging, and Richardson-Lucy deconvolution. We present the first visible light polarization and intensity images of the disc of BP Psc. Our deconvolution confirms the disc shape as detected before, mainly showing the southern side of the disc. In polarized intensity the disc is imaged at larger detail and also shows the northern side, giving it the typical shape of high-inclination flared discs. We explain the observed disc features by retrieving the large-scale geometry with MCMAX radiative transfer modelling, which yields a strongly flared model, atypical for discs of T Tauri stars.

The activL® Artificial Disc: a next-generation motion-preserving implant for chronic lumbar discogenic pain

PubMed Central

Yue, James J; Garcia, Rolando; Miller, Larry E

2016-01-01

Degeneration of the lumbar intervertebral discs is a leading cause of chronic low back pain in adults. Treatment options for patients with chronic lumbar discogenic pain unresponsive to conservative management include total disc replacement (TDR) or lumbar fusion. Until recently, only two lumbar TDRs had been approved by the US Food and Drug Administration − the Charité Artificial Disc in 2004 and the ProDisc-L Total Disc Replacement in 2006. In June 2015, a next-generation lumbar TDR received Food and Drug Administration approval − the activL® Artificial Disc (Aesculap Implant Systems). Compared to previous-generation lumbar TDRs, the activL® Artificial Disc incorporates specific design enhancements that result in a more precise anatomical match and allow a range of motion that better mimics the healthy spine. The results of mechanical and clinical studies demonstrate that the activL® Artificial Disc results in improved mechanical and clinical outcomes versus earlier-generation artificial discs and compares favorably to lumbar fusion. The purpose of this report is to describe the activL® Artificial Disc including implant characteristics, intended use, surgical technique, postoperative care, mechanical testing, and clinical experience to date. PMID:27274317

On the illumination of neutron star accretion discs

NASA Astrophysics Data System (ADS)

Wilkins, D. R.

2018-03-01

The illumination of the accretion disc in a neutron star X-ray binary by X-rays emitted from (or close to) the neutron star surface is explored through general relativistic ray tracing simulations. The applicability of the canonical suite of relativistically broadened emission line models (developed for black holes) to discs around neutron stars is evaluated. These models were found to describe well emission lines from neutron star accretion discs unless the neutron star radius is larger than the innermost stable orbit of the accretion disc at 6 rg or the disc is viewed at high inclination, above 60° where shadowing of the back side of the disc becomes important. Theoretical emissivity profiles were computed for accretion discs illuminated by hotspots on the neutron star surfaces, bands of emission and emission by the entirety of the hot, spherical star surface and in all cases, the emissivity profile of the accretion disc was found to be well represented by a single power law falling off slightly steeper than r-3. Steepening of the emissivity index was found where the emission is close to the disc plane and the disc can appear truncated when illuminated by a hotspot at high latitude. The emissivity profile of the accretion disc in Serpens X-1 was measured and found to be consistent with a single unbroken power law with index q=3.5_{-0.4}^{+0.3}, suggestive of illumination by the boundary layer between the disc and neutron star surface.

In vivo biofunctional evaluation of hydrogels for disc regeneration.

PubMed

Reitmaier, Sandra; Kreja, Ludwika; Gruchenberg, Katharina; Kanter, Britta; Silva-Correia, Joana; Oliveira, Joaquim Miguel; Reis, Rui Luís; Perugini, Valeria; Santin, Matteo; Ignatius, Anita; Wilke, Hans-Joachim

2014-01-01

Regenerative strategies aim to restore the original biofunctionality of the intervertebral disc. Different biomaterials are available, which might support disc regeneration. In the present study, the prospects of success of two hydrogels functionalized with anti-angiogenic peptides and seeded with bone marrow derived mononuclear cells (BMC), respectively, were investigated in an ovine nucleotomy model. In a one-step procedure iliac crest aspirates were harvested and, subsequently, separated BMC were seeded on hydrogels and implanted into the ovine disc. For the cell-seeded approach a hyaluronic acid-based hydrogel was used. The anti-angiogenic potential of newly developed VEGF-blockers was investigated on ionically crosslinked metacrylated gellan gum hydrogels. Untreated discs served as nucleotomy controls. 24 adult merino sheep were used. After 6 weeks histological, after 12 weeks histological and biomechanical analyses were conducted. Biomechanical tests revealed no differences between any of the implanted and nucleotomized discs. All implanted discs significantly degenerated compared to intact discs. In contrast, there was no marked difference between implanted and nucleotomized discs. In tendency, albeit not significant, degeneration score and disc height index deteriorated for all but not for the cell-seeded hydrogels from 6 to 12 weeks. Cell-seeded hydrogels slightly decelerated degeneration. None of the hydrogel configurations was able to regenerate biofunctionality of the intervertebral disc. This might presumably be caused by hydrogel extrusion. Great importance should be given to the development of annulus sealants, which effectively exploit the potential of (cell-seeded) hydrogels for biological disc regeneration and restoration of intervertebral disc functioning.

New Brown Dwarf Discs in Upper Scorpius Observed with WISE

NASA Technical Reports Server (NTRS)

Dawson, P.; Scholz, A.; Ray, T. P.; Natta, A.; Marsh, K. A.; Padgett, D.; Ressler, M. E.

2013-01-01

We present a census of the disc population for UKIDSS selected brown dwarfs in the 5-10 Myr old Upper Scorpius OB association. For 116 objects originally identified in UKIDSS, the majority of them not studied in previous publications, we obtain photometry from the Wide-Field Infrared Survey Explorer data base. The resulting colour magnitude and colour colour plots clearly show two separate populations of objects, interpreted as brown dwarfs with discs (class II) and without discs (class III). We identify 27 class II brown dwarfs, 14 of them not previously known. This disc fraction (27 out of 116, or 23%) among brown dwarfs was found to be similar to results for K/M stars in Upper Scorpius, suggesting that the lifetimes of discs are independent of the mass of the central object for low-mass stars and brown dwarfs. 5 out of 27 discs (19 per cent) lack excess at 3.4 and 4.6 microns and are potential transition discs (i.e. are in transition from class II to class III). The transition disc fraction is comparable to low-mass stars.We estimate that the time-scale for a typical transition from class II to class III is less than 0.4 Myr for brown dwarfs. These results suggest that the evolution of brown dwarf discs mirrors the behaviour of discs around low-mass stars, with disc lifetimes of the order of 5 10 Myr and a disc clearing time-scale significantly shorter than 1 Myr.

Posterior epidural disc fragment masquerading as spinal tumor: Review of the literature.

PubMed

Park, Taejune; Lee, Ho Jun; Kim, Jae Seong; Nam, Kiyeun

2018-03-09

Posterior epidural lumbar disc fragment is infrequent because of anatomical barriers, and it is difficult to diagnose posterior epidural lumbar disc fragment because of its rare incidence and the ambiguity of radiologic evaluations. And it is difficult to differentiate it from other diseases such as spinal tumors. Differential diagnosis of posterior epidural lumbar disc fragment is clinically important because its diagnosis can affect treatment and prognosis. To investigate the incidence, anatomical concern, etiology, symptom, diagnostic tool, management and prognosis of posterior epidural lumbar disc fragment, we reviewed articles including case report. We performed a search of all clinical studies of posterior epidural lumbar disc fragment published to date. The following keywords were searched: Posterior epidural lumbar disc fragment, disc migration, posterior epidural disc, extradural migration, dorsal epidural migration, sequestrated disc, and disc fragment. We identified 40 patients of posterior epidural lumbar disc fragment from 28 studies. The most common presentation of posterior epidural lumbar disc fragment was sudden onset radiculopathy (70.0%), followed by cauda equina syndrome (27.5%). The most frequently used diagnostic modality was magnetic resonance imaging (MRI), conducted in 36 cases (90.0%), and followed by computed tomography in 14 cases (35.0%). After the imaging studies, the preoperative diagnoses were 45.0% masses, 20.0% lesions, and 12.5% tumors. Characteristic MRI findings in posterior epidural lumbar disc fragment are helpful for diagnosis; it typically displays low signals on T1-weighted images and high signals on T2-weighted images with respect to the parent disc. In addition, most of the disc fragments show peripheral rim enhancement on MRI with gadolinium administration. Electrodiagnostic testing is useful for verifying nerve damage. Surgical treatment was performed in all cases, and neurologic complications were observed in 12.5%. As posterior epidural lumbar disc fragment could be masqueraded as spinal tumor, if rim enhancement is observed in MRI scans with sudden symptoms of radiculopathy or cauda equina syndrome, it should be taken into consideration. Early diagnosis can lead to early surgery, which can reduce complications.

A fully relativistic twisted disc around a slowly rotating Kerr black hole: derivation of dynamical equations and the shape of stationary configurations

NASA Astrophysics Data System (ADS)

Zhuravlev, V. V.; Ivanov, P. B.

2011-08-01

In this paper we derive equations describing the dynamics and stationary configurations of a twisted fully relativistic thin accretion disc around a slowly rotating black hole. We assume that the inclination angle of the disc is small and that the standard relativistic generalization of the α model of accretion discs is valid when the disc is flat. We find that similar to the case of non-relativistic twisted discs the disc dynamics and stationary shapes can be determined by a pair of equations formulated for two complex variables describing the orientation of the disc rings and velocity perturbations induced by the twist. We analyse analytically and numerically the shapes of stationary twisted configurations of accretion discs having non-zero inclinations with respect to the black hole equatorial plane at large distances r from the black hole. It is shown that the stationary configurations depend on two parameters - the viscosity parameter α and the parameter ?, where δ* is the opening angle (δ*˜h/r, where h is the disc half-thickness and r is large) of a flat disc and a is the black hole rotational parameter. When a > 0 and ? the shapes depend drastically on the value of α. When α is small the disc inclination angle oscillates with radius with amplitude and radial frequency of the oscillations dramatically increasing towards the last stable orbit, Rms. When α has a moderately small value the oscillations do not take place but the disc does not align with the equatorial plane at small radii. The disc inclination angle either is increasing towards Rms or exhibits a non-monotonic dependence on the radial coordinate. Finally, when α is sufficiently large the disc aligns with the equatorial plane at small radii. When a < 0 the disc aligns with the equatorial plane for all values of α. The results reported here may have implications for determining the structure and variability of accretion discs close to Rms as well as for modelling of emission spectra coming from different sources, which are supposed to contain black holes.

Vortex stretching in self-gravitating protoplanetary discs

NASA Astrophysics Data System (ADS)

Regály, Zs.; Vorobyov, E.

2017-10-01

Horseshoe-shaped brightness asymmetries of several transitional discs are thought to be caused by large-scale vortices. Anticyclonic vortices efficiently collect dust particles, therefore they can play a major role in planet formation. Former studies suggest that the disc self-gravity weakens vortices formed at the edge of the gap opened by a massive planet in discs whose masses are in the range of 0.01 ≤ Mdisc/M* ≤ 0.1. Here, we present an investigation on the long-term evolution of the large-scale vortices formed at the viscosity transition of the discs' dead zone outer edge by means of two-dimensional hydrodynamic simulations taking disc self-gravity into account. We perform a numerical study of low-mass, 0.001 ≤ Mdisc/M* ≤ 0.01, discs, for which cases disc self-gravity was previously neglected. The large-scale vortices are found to be stretched due to disc self-gravity even for low-mass discs with Mdisc/M* ≳ 0.005, where initially the Toomre Q-parameter was ≲ 50 at the vortex distance. As a result of stretching, the vortex aspect ratio increases and a weaker azimuthal density contrast develops. The strength of the vortex stretching is proportional to the disc mass. The vortex stretching can be explained by a combined action of a non-vanishing gravitational torque caused by the vortex and the Keplerian shear of the disc. Self-gravitating vortices are subject to significantly faster decay than non-self-gravitating ones. We found that vortices developed at sharp viscosity transitions of self-gravitating discs can be described by a Goodman - Narayan - Goldreich (GNG) model as long as the disc viscosity is low, I.e. αdz ≤ 10-5.

Intradiscal pressure study of percutaneous disc decompression with nucleoplasty in human cadavers.

PubMed

Chen, Yung C; Lee, Sang-heon; Chen, Darwin

2003-04-01

Intradiscal pressure was measured after percutaneous disc decompression by nucleoplasty in human cadavers with different degrees of disc degeneration. To assess intradiscal pressure change after disc decompression, and to analyze the influence of degeneration on the intradiscal pressure change. Partial removal of the nucleus has been shown to decompress herniated discs, relieving pressure on nerve roots and, in some cases, offering relief from disc pain. Nucleoplasty, a new minimally invasive procedure using patented Coblation technology, combines coagulation and ablation for partial removal of the nucleus. Coblated channels remove the tissue volume and may decrease the disc pressure. Three fresh human cadaver spinal specimens (T8-L5; age, 54-84 years; mean age, 70.7 years) were used in this investigation. The intradiscal pressure was measured at three points: before treatment, after each channel was created, and after treatment using a 25-guage 6-inch needle connected to a Merit Medical Systems Intellisystem Inflation Monitor. The needles were calibrated initially to approximately 30 pounds per square inch. For the control, the change in disc pressure was recorded by the same procedure without using Coblation energy. To evaluate the effectiveness of nucleoplasty, disc pressure changes were compared between treatment with and without Coblation energy. Intradiscal pressure was markedly reduced in the younger, healthy disc cadaver. In the older, degenerative disc cadavers, the change in intradiscal pressure after nucleoplasty was very small. There was an inverse correlation between the degree of disc degeneration and the change in intradiscal pressure. Pressure reduction through nucleoplasty is highly dependent on the degree of spine degeneration. Nucleoplasty markedly reduced intradiscal pressure in nondegenerative discs, but had a negligible effect on highly degenerative discs.

Engineered disc-like angle-ply structures for intervertebral disc replacement.

PubMed

Nerurkar, Nandan L; Sen, Sounok; Huang, Alice H; Elliott, Dawn M; Mauck, Robert L

2010-04-15

To develop a construction algorithm in which electrospun nanofibrous scaffolds are coupled with a biocompatible hydrogel to engineer a mesenchymal stem cell (MSC)-based disc replacement. To engineer a disc-like angle-ply structure (DAPS) that replicates the multiscale architecture of the intervertebral disc. Successful engineering of a replacement for the intervertebral disc requires replication of its mechanical function and anatomic form. Despite many attempts to engineer a replacement for ailing and degenerated discs, no prior study has replicated the multiscale hierarchical architecture of the native disc, and very few have assessed the mechanical function of formed neo-tissues. A new algorithm for the construction of a disc analogue was developed, using agarose to form a central nucleus pulposus (NP) and oriented electrospun nanofibrous scaffolds to form the anulus fibrosus region (AF). Bovine MSCs were seeded into both regions and biochemical, histologic, and mechanical maturation were evaluated with in vitro culture. We show that mechanical testing in compression and torsion, loading methods commonly used to assess disc mechanics, reveal equilibrium and time-dependent behaviors that are qualitatively similar to native tissue, although lesser in magnitude. Further, we demonstrate that cells seeded into both AF and NP regions adopt distinct morphologies that mirror those seen in native tissue, and that, in the AF region, this ordered community of cells deposit matrix that is organized in an angle-ply configuration. Finally, constructs demonstrate functional development with long-term in vitro culture. These findings provide a new approach for disc tissue engineering that replicates multi-scale form and function of the intervertebral disc, providing a foundation from which to build a multi-scale, biologic, anatomically and hierarchically relevant composite disc analogue for eventual disc replacement.

Mechanoreceptors in Diseased Cervical Intervertebral Disc and Vertigo.

PubMed

Yang, Liang; Yang, Cheng; Pang, Xiaodong; Li, Duanming; Yang, Hong; Zhang, Xinwu; Yang, Yi; Peng, Baogan

2017-04-15

We collected the samples of cervical intervertebral discs from patients with vertigo to examine the distribution and types of mechanoreceptors in diseased cervical disc. The aim of this study was to determine whether mechanoreceptors are distributed more abundantly in cervical discs from patients with cervical spondylosis, and whether they are related to vertigo. Previous limited studies have found that normal cervical intervertebral discs are supplied with mechanoreceptors that have been considered responsible for proprioceptive functions. Several clinical studies have indicated that the patients with cervical spondylosis manifested significantly impaired postural control and subjective balance disturbance. We collected 77 samples of cervical discs from 62 cervical spondylosis patients without vertigo, 61 samples from 54 patients with vertigo, and 40 control samples from 8 cadaveric donors to investigate distribution of mechanoreceptors containing neurofilament (NF200) and S-100 protein immunoreactive nerve endings. The immunohistochemical investigation revealed that the most frequently encountered mechanoreceptors were the Ruffini corpuscles in all groups of cervical disc samples. They were obviously increased in the number and deeply ingrown into inner annulus fibrosus and even into nucleus pulposus in the diseased cervical discs from patients with vertigo in comparison with the discs from patients without vertigo and control discs. Only three Golgi endings were seen in the three samples from patients with vertigo. No Pacinian corpuscles were found in any samples of cervical discs. The diseased cervical discs from patients with vertigo had more abundant distribution of Ruffini corpuscles than other discs. A positive association between the increased number and ingrowth of Ruffini corpuscles in the diseased cervical disc and the incidence of vertigo in the patients with cervical spondylosis was found, which may indicate a key role of Ruffini corpuscles in the pathogenesis of vertigo of cervical origin. 1.

Star-disc interaction in galactic nuclei: formation of a central stellar disc

NASA Astrophysics Data System (ADS)

Panamarev, Taras; Shukirgaliyev, Bekdaulet; Meiron, Yohai; Berczik, Peter; Just, Andreas; Spurzem, Rainer; Omarov, Chingis; Vilkoviskij, Emmanuil

2018-05-01

We perform high-resolution direct N-body simulations to study the effect of an accretion disc on stellar dynamics in an active galactic nucleus (AGN). We show that the interaction of the nuclear stellar cluster (NSC) with the gaseous accretion disc (AD) leads to formation of a stellar disc in the central part of the NSC. The accretion of stars from the stellar disc on to the super-massive black hole is balanced by the capture of stars from the NSC into the stellar disc, yielding a stationary density profile. We derive the migration time through the AD to be 3 per cent of the half-mass relaxation time of the NSC. The mass and size of the stellar disc are 0.7 per cent of the mass and 5 per cent of the influence radius of the super-massive black hole. An AD lifetime shorter than the migration time would result in a less massive nuclear stellar disc. The detection of such a stellar disc could point to past activity of the hosting galactic nucleus.

Does T2 mapping of the posterior annulus fibrosus indicate the presence of lumbar intervertebral disc herniation? A 3.0 Tesla magnetic resonance study.

PubMed

Messner, Alina; Stelzeneder, David; Trattnig, Stefan; Welsch, Götz H; Schinhan, Martina; Apprich, Sebastian; Brix, Martin; Windhager, Reinhard; Trattnig, Siegfried

2017-03-01

Indicating lumbar disc herniation via magnetic resonance imaging (MRI) T2 mapping in the posterior annulus fibrosus (AF). Sagittal T2 maps of 313 lumbar discs of 64 patients with low back pain were acquired at 3.0 Tesla (3T). The discs were rated according to disc herniation and bulging. Region of interest (ROI) analysis was performed on median, sagittal T2 maps. T2 values of the AF, in the most posterior 10% (PAF-10) and 20% of the disc (PAF-20), were compared. A significant increase in the T2 values of discs with herniations affecting the imaged area, compared to bulging discs and discs with lateral herniation, was shown in the PAF-10, where no association to the NP was apparent. The PAF-20 exhibited a moderate correlation to the nucleus pulposus (NP). High T2 values in the PAF-10 suggest the presence of disc herniation (DH). The results indicate that T2 values in the PAF-20 correspond more to changes in the NP.

Segmentation of optic disc and optic cup in retinal fundus images using shape regression.

PubMed

Sedai, Suman; Roy, Pallab K; Mahapatra, Dwarikanath; Garnavi, Rahil

2016-08-01

Glaucoma is one of the leading cause of blindness. The manual examination of optic cup and disc is a standard procedure used for detecting glaucoma. This paper presents a fully automatic regression based method which accurately segments optic cup and disc in retinal colour fundus image. First, we roughly segment optic disc using circular hough transform. The approximated optic disc is then used to compute the initial optic disc and cup shapes. We propose a robust and efficient cascaded shape regression method which iteratively learns the final shape of the optic cup and disc from a given initial shape. Gradient boosted regression trees are employed to learn each regressor in the cascade. A novel data augmentation approach is proposed to improve the regressors performance by generating synthetic training data. The proposed optic cup and disc segmentation method is applied on an image set of 50 patients and demonstrate high segmentation accuracy for optic cup and disc with dice metric of 0.95 and 0.85 respectively. Comparative study shows that our proposed method outperforms state of the art optic cup and disc segmentation methods.

Vertebral Augmentation can Induce Early Signs of Degeneration in the Adjacent Intervertebral Disc: Evidence from a Rabbit Model.

PubMed

Feng, Zhiyun; Chen, Lunhao; Hu, Xiaojian; Yang, Ge; Wang, Yue; Chen, Zhong

2018-04-11

An experimental study. The aim of this study was to determine the effect of polymethylmethacrylate (PMMA) augmentation on the adjacent disc. Vertebral augmentation with PMMA reportedly may predispose the adjacent vertebra to fracture. The influence of PMMA augmentation on the adjacent disc, however, remains unclear. Using a retroperitoneal approach, PMMA augmentation was performed for 23 rabbits. For each animal, at least one vertebra was augmented with 0.2 to 0.3 mL PMMA. The disc adjacent to the augmented vertebra and a proximal control disc were studied using magnetic resonance (MR) imaging, histological and molecular level evaluation at 1, 3, and 6 months postoperatively. Marrow contact channels in the endplate were quantified in histological slices and number of invalid channels (those without erythrocytes inside) was rated. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) was performed to determine disc cell apoptosis. On MR images, the signal and height of the adjacent disc did not change 6 months after vertebral augmentation. Histological scores of the adjacent disc increased over time, particularly for the nucleus pulposus. The adjacent disc had greater nucleus degeneration score than the control disc at 3 months (5.7 vs. 4.5, P < 0.01) and 6 months (6.9 vs. 4.4, P < 0.001). There were more invalid marrow contact channels in the endplate of augmented vertebra than the control (43.3% vs. 11.1%, P < 0.01). mRNA of ADAMTS-5, MMP-13, HIF-1α, and caspase-3 were significantly upregulated in the adjacent disc at 3 and 6 months (P < 0.05 for all). In addition, there were more TUNEL-positive cells in the adjacent disc than in the control disc (43.4% vs. 24.0%, P < 0.05) at 6 months postoperatively. Vertebral augmentation can induce early degenerative signs in the adjacent disc, which may be due to impaired nutrient supply to the disc. N/A.

First results of the SONS survey: submillimetre detections of debris discs

NASA Astrophysics Data System (ADS)

Panić, O.; Holland, W. S.; Wyatt, M. C.; Kennedy, G. M.; Matthews, B. C.; Lestrade, J. F.; Sibthorpe, B.; Greaves, J. S.; Marshall, J. P.; Phillips, N. M.; Tottle, J.

2013-10-01

New detections of debris discs at submillimetre wavelengths present highly valuable complementary information to prior observations of these sources at shorter wavelengths. Characterization of discs through spectral energy distribution modelling including the submillimetre fluxes is essential for our basic understanding of disc mass and temperature, and presents a starting point for further studies using millimetre interferometric observations. In the framework of the ongoing SCUBA-2 Observations of Nearby Stars, the instrument SCUBA-2 on the James Clerk Maxwell Telescope was used to provide measurements of 450 and 850 μm fluxes towards a large sample of nearby main-sequence stars with debris discs detected previously at shorter wavelengths. We present the first results from the ongoing survey, concerning 850 μm detections and 450 μm upper limits towards 10 stars, the majority of which are detected at submillimetre wavelengths for the first time. One, or possibly two, of these new detections is likely a background source. We fit the spectral energy distributions of the star+disc systems with a blackbody emission approach and derive characteristic disc temperatures. We use these temperatures to convert the observed fluxes to disc masses. We obtain a range of disc masses from 0.001 to 0.1 M⊕, values similar to the prior dust mass measurements towards debris discs. There is no evidence for evolution in dust mass with age on the main sequence, and indeed the upper envelope remains relatively flat at ≈0.5 M⊕ at all ages. The inferred disc masses are lower than those from disc detections around pre-main-sequence stars, which may indicate a depletion of solid mass. This may also be due to a change in disc opacity, though limited sensitivity means that it is not yet known what fraction of pre-main-sequence stars have discs with dust masses similar to debris disc levels. New, high-sensitivity detections are a path towards investigating the trends in dust mass evolution.

Comparison of Ripening Processes in Intact Tomato Fruit and Excised Pericarp Discs 1

PubMed Central

Campbell, Alan D.; Huysamer, Marius; Stotz, Henrik U.; Greve, L. Carl; Labavitch, John M.

1990-01-01

Physiological processes characteristic of ripening in tissues of intact tomato fruit (Lycopersicon esculentum Mill.) were examined in excised pericarp discs. Pericarp discs were prepared from mature-green tomato fruit and stored in 24-well culture plates, in which individual discs could be monitored for color change, ethylene biosynthesis, and respiration, and selected for cell wall analysis. Within the context of these preparation and handling procedures, most whole fruit ripening processes were maintained in pericarp discs. Pericarp discs and matched intact fruit passed through the same skin color stages at similar rates, as expressed in the L*a*b* color space, changing from green (a* < −5) to red (a* > 15) in about 6 days. Individual tissues of the pericarp discs changed color in the same sequence seen in intact fruit (exocarp, endocarp, then vascular parenchyma). Discs from different areas changed in the same spatial sequence seen in intact fruit (bottom, middle, top). Pericarp discs exhibited climacteric increases in ethylene biosynthesis and CO2 production comparable with those seen in intact fruit, but these were more tightly linked to rate of color change, reaching a peak around a* = 5. Tomato pericarp discs decreased in firmness as color changed. Cell wall carbohydrate composition changed with color as in intact fruit: the quantity of water-soluble pectin eluted from the starch-free alcohol insoluble substances steadily increased and more tightly bound, water-insoluble, pectin decreased in inverse relationship. The cell wall content of the neutral sugars arabinose, rhamnose, and galactose steadily decreased as color changed. The extractable activity of specific cell wall hydrolases changed as in intact fruit: polygalacturonase activity, not detectable in green discs (a* = −5), appeared as discs turned yellow-red (a* = 5), and increased another eight-fold as discs became full red (a* value +20). Carboxymethyl-cellulase activity, low in extracts from green discs, increased about six-fold as discs changed from yellow (a* = 0) to red. PMID:16667893

Patterns of lumbar disc degeneration are different in degenerative disc disease and disc prolapse magnetic resonance imaging analysis of 224 patients.

PubMed

Kanna, Rishi M; Shetty, Ajoy Prasad; Rajasekaran, S

2014-02-01

Existing research on lumbar disc degeneration has remained inconclusive regarding its etiology, pathogenesis, symptomatology, prevention, and management. Degenerative disc disease (DDD) and disc prolapse (DP) are common diseases affecting the lumbar discs. Although they manifest clinically differently, existing studies on disc degeneration have included patients with both these features, leading to wide variations in observations. The possible relationship or disaffect between DDD and DP is not fully evaluated. To analyze the patterns of lumbar disc degeneration in patients with chronic back pain and DDD and those with acute DP. Prospective, magnetic resonance imaging-based radiological study. Two groups of patients (aged 20-50 years) were prospectively studied. Group 1 included patients requiring a single level microdiscectomy for acute DP. Group 2 included patients with chronic low back pain and DDD. Discs were assessed by magnetic resonance imaging through Pfirmann grading, Schmorl nodes, Modic changes, and the total end-plate damage score for all the five lumbar discs. Group 1 (DP) had 91 patients and group 2 (DDD) had 133 patients. DP and DDD patients differed significantly in the number, extent, and severity of degeneration. DDD patients had a significantly higher number of degenerated discs than DP patients (p<.000). The incidence of multilevel and pan-lumbar degeneration was also significantly higher in DDD group. The pattern of degeneration also differed in both the groups. DDD patients had predominant upper lumbar involvement, whereas DP patients had mainly lower lumbar degeneration. Modic changes were more common in DP patients, especially at the prolapsed level. Modic changes were present in 37% of prolapsed levels compared with 9.9% of normal discs (p<.00). The total end-plate damage score had a positive correlation with disc degeneration in both the groups. Further the mean total end-plate damage score at prolapsed level was also significantly higher. The results suggest that patients with disc prolapse, and those with back pain with DDD are clinically and radiologically different groups of patients with varying patterns, severity, and extent of disc degeneration. This is the first study in literature to compare and identify significant differences in these two commonly encountered patient groups. In patients with single-level DP, the majority of the other discs are nondegenerate, the lower lumbar spine is predominantly involved and the end-plate damage is higher. Patients with back pain and DDD have larger number of degenerate discs, early multilevel degeneration, and predominant upper lumbar degeneration. The knowledge that these two groups of patients are different clinically and radiologically is critical for our improved understanding of the disease and for future studies on disc degeneration and disc prolapse. Copyright © 2014 Elsevier Inc. All rights reserved.

Signatures of broken protoplanetary discs in scattered light and in sub-millimetre observations

NASA Astrophysics Data System (ADS)

Facchini, Stefano; Juhász, Attila; Lodato, Giuseppe

2018-02-01

Spatially resolved observations of protoplanetary discs are revealing that their inner regions can be warped or broken from the outer disc. A few mechanisms are known to lead to such 3D structures; among them, the interaction with a stellar companion. We perform a 3D SPH simulation of a circumbinary disc misaligned by 60° with respect to the binary orbital plane. The inner disc breaks from the outer regions, precessing as a rigid body and leading to a complex evolution. As the inner disc precesses, the misalignment angle between the inner and outer discs varies by more than 100°. Different snapshots of the evolution are post-processed with a radiative transfer code, in order to produce observational diagnostics of the process. Even though the simulation was produced for the specific case of a circumbinary disc, most of the observational predictions hold for any disc hosting a precessing inner rim. Synthetic scattered light observations show strong azimuthal asymmetries, where the pattern depends strongly on the misalignment angle between the inner and outer discs. The asymmetric illumination of the outer disc leads to azimuthal variations of the temperature structure, in particular in the upper layers, where the cooling time is short. These variations are reflected in asymmetric surface brightness maps of optically thick lines, as CO J = 3-2. The kinematical information obtained from the gas lines is unique in determining the disc structure. The combination of scattered light images and (sub-)mm lines can distinguish between radial inflow and misaligned inner disc scenarios.

Radiologic study of disc behavior following compression fracture of the thoracolumbar hinge managed by kyphoplasty: A 52-case series.

PubMed

Teyssédou, S; Saget, M; Gayet, L E; Pries, P; Brèque, C; Vendeuvre, T

2016-02-01

Kyphoplasty has proved effective for durable correction of traumatic vertebral deformity following Magerl A fracture, but subsequent behavior of the adjacent discs is unclear. The objective of the present study was to analyze evolution according to severity of initial kyphosis and quality of fracture reduction. A single-center prospective study included cases of single compression fracture of the thoracolumbar hinge managed by Kyphon Balloon Kyphoplasty with polymethylmethacrylate bone cement. Radiology focused on traumatic vertebral kyphosis (VK), disc angulation (DA) and disc height index (DHI) in the adjacent discs. Linear regression assessed the correlation between superior disc height index (SupDHI) and postoperative VK on the one hand and correction gain on the other, using the Student t test for matched pairs and Pearson correlation coefficient. Fifty-two young patients were included, with mean follow-up of 18.6 months. VK fell from 13.9° preoperatively to 8.2° at last follow-up. DHI found significant superior disc subsidence (P=0.0001) and non-significant inferior disc subsidence (P=0.116). DA showed significantly reduced superior disc lordosis (P=4*10(-5)). SupDHI correlated with VK correction (r=0.32). Preoperative VK did not correlate with radiologic degeneration of the adjacent discs. Correction of traumatic vertebral deformity avoids subsidence and loss of mechanical function in the superior adjacent disc. The underlying disc compensates for residual deformity. Balloon kyphoplasty is useful in compression fracture, providing significant reduction of traumatic vertebral deformity while conserving free and healthy adjacent discs. IV. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

Rat disc torsional mechanics: effect of lumbar and caudal levels and axial compression load.

PubMed

Espinoza Orías, Alejandro A; Malhotra, Neil R; Elliott, Dawn M

2009-03-01

Rat models with altered loading are used to study disc degeneration and mechano-transduction. Given the prominent role of mechanics in disc function and degeneration, it is critical to measure mechanical behavior to evaluate changes after model interventions. Axial compression mechanics of the rat disc are representative of the human disc when normalized by geometry, and differences between the lumbar and caudal disc have been quantified in axial compression. No study has quantified rat disc torsional mechanics. Compare the torsional mechanical behavior of rat lumbar and caudal discs, determine the contribution of combined axial load on torsional mechanics, and compare the torsional properties of rat discs to human lumbar discs. Cadaveric biomechanical study. Cyclic torsion without compressive load followed by cyclic torsion with a fixed compressive load was applied to rat lumbar and caudal disc levels. The apparent torsional modulus was higher in the lumbar region than in the caudal region: 0.081+/-0.026 (MPa/degrees, mean+/-SD) for lumbar axially loaded; 0.066+/-0.028 for caudal axially loaded; 0.091+/-0.033 for lumbar in pure torsion; and 0.056+/-0.035 for caudal in pure torsion. These values were similar to human disc properties reported in the literature ranging from 0.024 to 0.21 MPa/degrees. Use of the caudal disc as a model may be appropriate if the mechanical focus is within the linear region of the loading regime. These results provide support for use of this animal model in basic science studies with respect to torsional mechanics.

Eccentricity evolution during planet-disc interaction

NASA Astrophysics Data System (ADS)

Ragusa, Enrico; Rosotti, Giovanni; Teyssandier, Jean; Booth, Richard; Clarke, Cathie J.; Lodato, Giuseppe

2018-03-01

During the process of planet formation, the planet-disc interactions might excite (or damp) the orbital eccentricity of the planet. In this paper, we present two long (t ˜ 3 × 105 orbits) numerical simulations: (a) one (with a relatively light disc, Md/Mp = 0.2), where the eccentricity initially stalls before growing at later times and (b) one (with a more massive disc, Md/Mp = 0.65) with fast growth and a late decrease of the eccentricity. We recover the well-known result that a more massive disc promotes a faster initial growth of the planet eccentricity. However, at late times the planet eccentricity decreases in the massive disc case, but increases in the light disc case. Both simulations show periodic eccentricity oscillations superimposed on a growing/decreasing trend and a rapid transition between fast and slow pericentre precession. The peculiar and contrasting evolution of the eccentricity of both planet and disc in the two simulations can be understood by invoking a simple toy model where the disc is treated as a second point-like gravitating body, subject to secular planet-planet interaction and eccentricity pumping/damping provided by the disc. We show how the counterintuitive result that the more massive simulation produces a lower planet eccentricity at late times can be understood in terms of the different ratios of the disc-to-planet angular momentum in the two simulations. In our interpretation, at late times the planet eccentricity can increase more in low-mass discs rather than in high-mass discs, contrary to previous claims in the literature.

Novel Human Intervertebral Disc Strain Template to Quantify Regional Three-Dimensional Strains in a Population and Compare to Internal Strains Predicted by a Finite Element Model

PubMed Central

Showalter, Brent L.; DeLucca, John F.; Peloquin, John M.; Cortes, Daniel H.; Yoder, Jonathon H.; Jacobs, Nathan T.; Wright, Alexander C.; Gee, James C.; Vresilovic, Edward J.; Elliott, Dawn M.

2017-01-01

Tissue strain is an important indicator of mechanical function, but is difficult to noninvasively measure in the intervertebral disc. The objective of this study was to generate a disc strain template, a 3D average of disc strain, of a group of human L4–L5 discs loaded in axial compression. To do so, magnetic resonance images of uncompressed discs were used to create an average disc shape. Next, the strain tensors were calculated pixel-wise by using a previously developed registration algorithm. Individual disc strain tensor components were then transformed to the template space and averaged to create the disc strain template. The strain template reduced individual variability while highlighting group trends. For example, higher axial and circumferential strains were present in the lateral and posterolateral regions of the disc, which may lead to annular tears. This quantification of group-level trends in local 3D strain is a significant step forward in the study of disc biomechanics. These trends were compared to a finite element model that had been previously validated against the disc-level mechanical response. Depending on the strain component, 81–99% of the regions within the finite element model had calculated strains within one standard deviation of the template strain results. The template creation technique provides a new measurement technique useful for a wide range of studies, including more complex loading conditions, the effect of disc pathologies and degeneration, damage mechanisms, and design and evaluation of treatments. PMID:26694516

Lumbar Disc Degenerative Disease: Disc Degeneration Symptoms and Magnetic Resonance Image Findings

PubMed Central

Saleem, Shafaq; Rehmani, Muhammad Asim Khan; Raees, Aisha; Alvi, Arsalan Ahmad; Ashraf, Junaid

2013-01-01

Study Design Cross sectional and observational. Purpose To evaluate the different aspects of lumbar disc degenerative disc disease and relate them with magnetic resonance image (MRI) findings and symptoms. Overview of Literature Lumbar disc degenerative disease has now been proven as the most common cause of low back pain throughout the world. It may present as disc herniation, lumbar spinal stenosis, facet joint arthropathy or any combination. Presenting symptoms of lumbar disc degeneration are lower back pain and sciatica which may be aggravated by standing, walking, bending, straining and coughing. Methods This study was conducted from January 2012 to June 2012. Study was conducted on the diagnosed patients of lumbar disc degeneration. Diagnostic criteria were based upon abnormal findings in MRI. Patients with prior back surgery, spine fractures, sacroiliac arthritis, metabolic bone disease, spinal infection, rheumatoid arthritis, active malignancy, and pregnancy were excluded. Results During the targeted months, 163 patients of lumbar disc degeneration with mean age of 43.92±11.76 years, came into Neurosurgery department. Disc degeneration was most commonly present at the level of L4/L5 105 (64.4%).Commonest types of disc degeneration were disc herniation 109 (66.9%) and lumbar spinal stenosis 37 (22.7%). Spondylolisthesis was commonly present at L5/S1 10 (6.1%) and associated mostly with lumbar spinal stenosis 7 (18.9%). Conclusions Results reported the frequent occurrence of lumbar disc degenerative disease in advance age. Research efforts should endeavor to reduce risk factors and improve the quality of life. PMID:24353850

Forming disc galaxies in major mergers - III. The effect of angular momentum on the radial density profiles of disc galaxies

NASA Astrophysics Data System (ADS)

Peschken, N.; Athanassoula, E.; Rodionov, S. A.

2017-06-01

We study the effect of angular momentum on the surface density profiles of disc galaxies, using high-resolution simulations of major mergers whose remnants have downbending radial density profiles (type II). As described in the previous papers of this series, in this scenario, most of the disc mass is acquired after the collision via accretion from a hot gaseous halo. We find that the inner and outer disc scalelengths, as well as the break radius, correlate with the total angular momentum of the initial merging system, and are larger for high-angular momentum systems. We follow the angular momentum redistribution in our simulated galaxies, and find that like the mass, the disc angular momentum is acquired via accretion, I.e. to the detriment of the gaseous halo. Furthermore, high-angular momentum systems give more angular momentum to their discs, which directly affects their radial density profile. Adding simulations of isolated galaxies to our sample, we find that the correlations are valid also for disc galaxies evolved in isolation. We show that the outer part of the disc at the end of the simulation is populated mainly by inside-out stellar migration, and that in galaxies with higher angular momentum, stars travel radially further out. This, however, does not mean that outer disc stars (in type II discs) were mostly born in the inner disc. Indeed, generally the break radius increases over time, and not taking this into account leads to overestimating the number of stars born in the inner disc.

The role of disc self-gravity in circumbinary planet systems - I. Disc structure and evolution

NASA Astrophysics Data System (ADS)

Mutter, Matthew M.; Pierens, Arnaud; Nelson, Richard P.

2017-03-01

We present the results of two-dimensional hydrodynamic simulations of self-gravitating circumbinary discs around binaries whose parameters match those of the circumbinary planet-hosting systems Kepler-16, Kepler-34 and Kepler-35. Previous work has shown that non-self-gravitating discs in these systems form an eccentric precessing inner cavity due to tidal truncation by the binary, and planets which form at large radii migrate until stalling at this cavity. Whilst this scenario appears to provide a natural explanation for the observed orbital locations of the circumbinary planets, previous simulations have failed to match the observed planet orbital parameters. The aim of this work is to examine the role of self-gravity in modifying circumbinary disc structure as a function of disc mass, prior to considering the evolution of embedded circumbinary planets. In agreement with previous work, we find that for disc masses between one and five times the minimum mass solar nebula (MMSN), disc self-gravity affects modest changes in the structure and evolution of circumbinary discs. Increasing the disc mass to 10 or 20 MMSN leads to two dramatic changes in disc structure. First, the scale of the inner cavity shrinks substantially, bringing its outer edge closer to the binary. Secondly, in addition to the eccentric inner cavity, additional precessing eccentric ring-like features develop in the outer regions of the discs. If planet formation starts early in the disc lifetime, these changes will have a significant impact on the formation and evolution of planets and precursor material.

Radial modes of laterally stiffened piezoelectric disc transducers for ultrasonic collimated beam generation

DOE PAGES

Chillara, Vamshi Krishna; Pantea, Cristian; Sinha, Dipen N.

2017-07-15

Here, we numerically investigate the resonance and vibration characteristics of radial modes of laterally stiffened piezoelectric disc transducers. Lateral stiffening is modeled using a spring and vibration characteristics of the piezo-disc are investigated with increasing lateral stiffness. It is found that the resonant frequency response of the radial modes follows an asymptotic behavior approaching that of a clamped disc with increasing lateral stiffness. The radial mode vibration pattern of the discs is also found to be affected by lateral stiffness. While the vibration pattern of a free disc corresponds to a Bessel function, laterally stiffened discs show edge-effects where theymore » depart from the Bessel-like behavior. In addition, a fully clamped piezo-disc is found to have an extra side-lobe when compared to a free disc. Ultrasonic beam profiles generated from radial modes of laterally stiffened discs are numerically investigated. It is found that the free piezo-disc generates a Bessel beam that has multiple side-lobes. Increasing the lateral stiffness results in a significant reduction of side-lobes in the beam profile. This technique of generating a collimated beam with side-lobe reduction finds significant applications in imaging through concrete, drilling mud, and other highly attenuating materials.« less

Construction Strategy and Progress of Whole Intervertebral Disc Tissue Engineering.

PubMed

Yang, Qiang; Xu, Hai-wei; Hurday, Sookesh; Xu, Bao-shan

2016-02-01

Degenerative disc disease (DDD) is the major cause of low back pain, which usually leads to work absenteeism, medical visits and hospitalization. Because the current conservative procedures and surgical approaches to treatment of DDD only aim to relieve the symptoms of disease but not to regenerate the diseased disc, their long-term efficiency is limited. With the rapid developments in medical science, tissue engineering techniques have progressed markedly in recent years, providing a novel regenerative strategy for managing intervertebral disc disease. However, there are as yet no ideal methods for constructing tissue-engineered intervertebral discs. This paper reviews published reports pertaining to intervertebral disc tissue engineering and summarizes data concerning the seed cells and scaffold materials for tissue-engineered intervertebral discs, construction of tissue-engineered whole intervertebral discs, relevant animal experiments and effects of mechanics on the construction of tissue-engineered intervertebral disc and outlines the existing problems and future directions. Although the perfect regenerative strategy for treating DDD has not yet been developed, great progress has been achieved in the construction of tissue-engineered intervertebral discs. It is believed that ongoing research on intervertebral disc tissue engineering will result in revolutionary progress in the treatment of DDD. © 2016 Chinese Orthopaedic Association and John Wiley & Sons Australia, Ltd.

Formation of precessing jets by tilted black hole discs in 3D general relativistic MHD simulations

NASA Astrophysics Data System (ADS)

Liska, M.; Hesp, C.; Tchekhovskoy, A.; Ingram, A.; van der Klis, M.; Markoff, S.

2018-02-01

Gas falling into a black hole (BH) from large distances is unaware of BH spin direction, and misalignment between the accretion disc and BH spin is expected to be common. However, the physics of tilted discs (e.g. angular momentum transport and jet formation) is poorly understood. Using our new GPU-accelerated code H-AMR, we performed 3D general relativistic magnetohydrodynamic simulations of tilted thick accretion discs around rapidly spinning BHs, at the highest resolution to date. We explored the limit where disc thermal pressure dominates magnetic pressure, and showed for the first time that, for different magnetic field strengths on the BH, these flows launch magnetized relativistic jets propagating along the rotation axis of the tilted disc (rather than of the BH). If strong large-scale magnetic flux reaches the BH, it bends the inner few gravitational radii of the disc and jets into partial alignment with the BH spin. On longer time-scales, the simulated disc-jet system as a whole undergoes Lense-Thirring precession and approaches alignment, demonstrating for the first time that jets can be used as probes of disc precession. When the disc turbulence is well resolved, our isolated discs spread out, causing both the alignment and precession to slow down.

Extended transiting discs and rings around planets and brown dwarfs: theoretical constraints

NASA Astrophysics Data System (ADS)

Zanazzi, J. J.; Lai, Dong

2017-02-01

Newly formed planets (or brown dwarfs) may possess discs or rings which occupy an appreciable fraction of the planet's Hill sphere and extend beyond the Laplace radius, where the tidal torque from the host star dominates over the torque from the oblate planet. Such a disc/ring can exhibit unique, detectable transit signatures, provided that the disc/ring is significantly misaligned with the orbital plane of the planet. There exists tentative evidence for an extended ring system around the young K5 star 1 SWASP J140747-354542. We present a general theoretical study of the inclination (warp) profile of circumplanetary discs under the combined influences of the tidal torque from the central star, the torque from the oblate planet, and the self-gravity of the disc. We calculate the equilibrium warp profile (`generalized Laplace surface') and investigate the condition for coherent precession of the disc. We find that to maintain a non-negligible misalignment between the extended outer disc and the planet's orbital plane, and to ensure coherent disc precession, the disc surface density must be sufficiently large so that the self-gravity torque overcomes the tidal torque from the central star. Our analysis and quantitative results can be used to constrain the parameters of transiting circumplanetary discs which may be detected in the future.

The Diversity of Assembly Histories Leading to Disc Galaxy Formation in a ΛCDM Model

NASA Astrophysics Data System (ADS)

Font, Andreea S.; McCarthy, Ian G.; Le Brun, Amandine M. C.; Crain, Robert A.; Kelvin, Lee S.

2017-11-01

Disc galaxies forming in a LambdaCDM cosmology often experience violent mergers. The fact that disc galaxies are ubiquitous suggests that quiescent histories are not necessary. Modern cosmological simulations can now obtain realistic populations of disc galaxies, but it is still unclear how discs manage to survive massive mergers. Here we use a suite of hydrodynamical cosmological simulations to elucidate the fate of discs encountering massive mergers. We follow the changes in the post-merger disc-to-total ratios (D/T) of simulated galaxies and examine the relations between their present-day morphology, assembly history and gas fractions. We find that approximately half of present-day disc galaxies underwent at least one merger with a satellite more massive the host's stellar component and a third had mergers with satellites three times as massive. These mergers lead to a sharp, but often temporary, decrease in the D/T of the hosts, implying that discs are usually disrupted but then quickly re-grow. To do so, high cold gas fractions are required post-merger, as well as a relatively quiescent recent history (over a few Gyrs before z = 0). Our results show that discs can form via diverse merger pathways and that quiescent histories are not the dominant mode of disc formation.

Senescent intervertebral disc cells exhibit perturbed matrix homeostasis phenotype.

PubMed

Ngo, Kevin; Patil, Prashanti; McGowan, Sara J; Niedernhofer, Laura J; Robbins, Paul D; Kang, James; Sowa, Gwendolyn; Vo, Nam

2017-09-01

Aging greatly increases the risk for intervertebral disc degeneration (IDD) as a result of proteoglycan loss due to reduced synthesis and enhanced degradation of the disc matrix proteoglycan (PG). How disc matrix PG homeostasis becomes perturbed with age is not known. The goal of this study is to determine whether cellular senescence is a source of this perturbation. We demonstrated that disc cellular senescence is dramatically increased in the DNA repair-deficient Ercc1 -/Δ mouse model of human progeria. In these accelerated aging mice, increased disc cellular senescence is closely associated with the rapid loss of disc PG. We also directly examine PG homeostasis in oxidative damage-induced senescent human cells using an in vitro cell culture model system. Senescence of human disc cells treated with hydrogen peroxide was confirmed by growth arrest, senescence-associated β-galactosidase activity, γH2AX foci, and acquisition of senescence-associated secretory phenotype. Senescent human disc cells also exhibited perturbed matrix PG homeostasis as evidenced by their decreased capacity to synthesize new matrix PG and enhanced degradation of aggrecan, a major matrix PG. of the disc. Our in vivo and in vitro findings altogether suggest that disc cellular senescence is an important driver of PG matrix homeostatic perturbation and PG loss. Published by Elsevier B.V.

26 CFR 1.921-1T - Temporary regulations providing transition rules for DISCs and FSCs.

Code of Federal Regulations, 2010 CFR

2010-04-01

... a DISC's taxable year? A-1: Without regard to the annual accounting period of the DISC, the last... distribution of previously taxed income have on the earnings and profits of corporate shareholders of the former DISC? A-8: The earnings and profits of the corporate shareholders of the former DISC will be...

Trapping of low-mass planets outside the truncated inner edges of protoplanetary discs

NASA Astrophysics Data System (ADS)

Miranda, Ryan; Lai, Dong

2018-02-01

We investigate the migration of a low-mass (≲10 M⊕) planet near the inner edge of a protoplanetary disc using two-dimensional viscous hydrodynamics simulations. We employ an inner boundary condition representing the truncation of the disc at the stellar corotation radius. As described by Tsang, wave reflection at the inner disc boundary modifies the Type I migration torque on the planet, allowing migration to be halted before the planet reaches the inner edge of the disc. For low-viscosity discs (α ≲ 10-3), planets may be trapped with semi-major axes as large as three to five times the inner disc radius. In general, planets are trapped closer to the inner edge as either the planet mass or the disc viscosity parameter α increases, and farther from the inner edge as the disc thickness is increased. This planet trapping mechanism may impact the formation and migration history of close-in compact multiplanet systems.

Correlation between direction and severity of temporomandibular joint disc displacement and reduction ability during mouth opening.

PubMed

Litko, M; Berger, M; Szkutnik, J; Różyło-Kalinowska, I

2017-12-01

The most common temporomandibular joint (TMJ) internal derangement is an abnormal relationship of the disc with respect to the mandibular condyle, articular eminence and glenoid fossa-disc displacement. The aim of our study was to analyse the correlation between partial/complete disc displacement in the intercuspal position (IP) and its reduction in the open-mouth position (OMP) in both oblique sagittal and coronal planes on magnetic resonance imaging (MRI) in patients with temporomandibular disorders. Multisection MRI analysis of 382 TMJs was conducted in 191 patients with disc displacement according to the RDC/TMD criteria (148 women, 43 men; aged 14-60 years). The disc position was evaluated on all oblique sagittal and coronal images in the IP and the OMP. Univariate logistic regression analysis showed that the severity of disc displacement in the sagittal plane is a statistically significant predictor of reduction ability during mouth opening (B = 3.118; P < .001). Moreover, the severity of disc displacement in both planes is also a significant predictor of disc reduction in OMP (B = 2.200; P < .05). In conclusion, reduction ability during mouth opening is associated with the severity of disc displacement in IP, in both sagittal and coronal planes. Multisection analysis of all MR images allows distinguishing the correct disc position from disc displacement and can improve the ability to distinguish between various stages of TMJ internal derangement. © 2017 John Wiley & Sons Ltd.

Comparison of Optic Disc Margin Identified by Color Disc Photography and High-Speed Ultrahigh-Resolution Optical Coherence Tomography

PubMed Central

Manassakorn, Anita; Ishikawa, Hiroshi; Kim, Jong S.; Wollstein, Gadi; Bilonick, Richard A.; Kagemann, Larry; Gabriele, Michelle L.; Sung, Kyung Rim; Mumcuoglu, Tarkan; Duker, Jay S.; Fujimoto, James G.; Schuman, Joel S.

2009-01-01

Objective To determine the correspondence between optic disc margins evaluated using disc photography (DP) and optical coherence tomography (OCT). Methods From May 1, 2005, through November 10, 2005, 17 healthy volunteers (17 eyes) had raster scans (180 frames, 501 samplings per frame) centered on the optic disc taken with stereo-optic DP and high-speed ultrahigh-resolution OCT (hsUHR-OCT). Two image outputs were derived from the hsUHR-OCT data set: an en face hsUHR-OCT fundus image and a set of 180 frames of cross-sectional images. Three ophthalmologists independently and in a masked, randomized fashion marked the disc margin on the DP, hsUHR-OCT fundus, and cross-sectional images using custom software. Disc size (area and horizontal and vertical diameters) and location of the geometric disc center were compared among the 3 types of images. Results The hsUHR-OCT fundus image definition showed a significantly smaller disc size than the DP definition (P<.001, mixed-effects analysis). The hsUHR-OCT cross-sectional image definition showed a significantly larger disc size than the DP definition (P<.001). The geometric disc center location was similar among the 3 types of images except for the y-coordinate, which was significantly smaller in the hsUHR-OCT fundus images than in the DP images. Conclusion The optic disc margin as defined by hsUHR-OCT was significantly different than the margin defined by DP. PMID:18195219

Instability of warped discs

NASA Astrophysics Data System (ADS)

Doǧan, S.; Nixon, C. J.; King, A. R.; Pringle, J. E.

2018-05-01

Accretion discs are generally warped. If a warp in a disc is too large, the disc can `break' apart into two or more distinct planes, with only tenuous connections between them. Further, if an initially planar disc is subject to a strong differential precession, then it can be torn apart into discrete annuli that precess effectively independently. In previous investigations, torque-balance formulae have been used to predict where and when the disc breaks into distinct parts. In this work, focusing on discs with Keplerian rotation and where the shearing motions driving the radial communication of the warp are damped locally by turbulence (the `diffusive' regime), we investigate the stability of warped discs to determine the precise criterion for an isolated warped disc to break. We find and solve the dispersion relation, which, in general, yields three roots. We provide a comprehensive analysis of this viscous-warp instability and the emergent growth rates and their dependence on disc parameters. The physics of the instability can be understood as a combination of (1) a term that would generally encapsulate the classical Lightman-Eardley instability in planar discs (given by ∂(νΣ)/∂Σ < 0) but is here modified by the warp to include ∂(ν1|ψ|)/∂|ψ| < 0, and (2) a similar condition acting on the diffusion of the warp amplitude given in simplified form by ∂(ν2|ψ|)/∂|ψ| < 0. We discuss our findings in the context of discs with an imposed precession, and comment on the implications for different astrophysical systems.

DISC1 Protein Regulates γ-Aminobutyric Acid, Type A (GABAA) Receptor Trafficking and Inhibitory Synaptic Transmission in Cortical Neurons.

PubMed

Wei, Jing; Graziane, Nicholas M; Gu, Zhenglin; Yan, Zhen

2015-11-13

Association studies have suggested that Disrupted-in-Schizophrenia 1 (DISC1) confers a genetic risk at the level of endophenotypes that underlies many major mental disorders. Despite the progress in understanding the significance of DISC1 at neural development, the mechanisms underlying DISC1 regulation of synaptic functions remain elusive. Because alterations in the cortical GABA system have been strongly linked to the pathophysiology of schizophrenia, one potential target of DISC1 that is critically involved in the regulation of cognition and emotion is the GABAA receptor (GABAAR). We found that cellular knockdown of DISC1 significantly reduced GABAAR-mediated synaptic and whole-cell current, whereas overexpression of wild-type DISC1, but not the C-terminal-truncated DISC1 (a schizophrenia-related mutant), significantly increased GABAAR currents in pyramidal neurons of the prefrontal cortex. These effects were accompanied by DISC1-induced changes in surface GABAAR expression. Moreover, the regulation of GABAARs by DISC1 knockdown or overexpression depends on the microtubule motor protein kinesin 1 (KIF5). Our results suggest that DISC1 exerts an important effect on GABAergic inhibitory transmission by regulating KIF5/microtubule-based GABAAR trafficking in the cortex. The knowledge gained from this study would shed light on how DISC1 and the GABA system are linked mechanistically and how their interactions are critical for maintaining a normal mental state. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

STEREOSCOPIC DETERMINATION OF HEIGHTS OF EXTREME ULTRAVIOLET BRIGHT POINTS USING DATA TAKEN BY SECCHI/EUVI ABOARD STEREO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kwon, Ryun-Young; Chae, Jongchul; Zhang Jie

2010-05-01

We measure the heights of EUV bright points (BPs) above the solar surface by applying a stereoscopic method to the data taken by the Solar TErrestrial RElations Observatory/SECCHI/Extreme UltraViolet Imager (EUVI). We have developed a three-dimensional reconstruction method for point-like features such as BPs using the simple principle that the position of a point in the three-dimensional space is specified as the intersection of two lines of sight. From a set of data consisting of EUVI 171 A, 195 A, 284 A, and 304 A images taken on 11 days arbitrarily selected during a period of 14 months, we havemore » identified and analyzed 210 individual BPs that were visible on all four passband images and smaller than 30 Mm. The BPs seen in the 304 A images have an average height of 4.4 Mm, and are often associated with the legs of coronal loops. In the 171 A, 195 A, and 284 A images the BPs appear loop-shaped, and have average heights of 5.1, 6.7, and 6.1 Mm, respectively. Moreover, there is a tendency that overlying loops are filled with hotter plasmas. The average heights of BPs in 171 A, 195 A, and 284 A passbands are roughly twice the corresponding average lengths. Our results support the notion that an EUV BP represents a system of small loops with temperature stratification like flaring loops, being consistent with the magnetic reconnection origin.« less

Predicting water quality by relating secchi-disk transparency and chlorophyll a measurements to Landsat satellite imagery for Michigan inland lakes, 2001-2006

USGS Publications Warehouse

Fuller, L.M.; Minnerick, R.J.

2007-01-01

The State of Michigan has more than 11,000 inland lakes; approximately 3,500 of these lakes are greater than 25 acres. The USGS, in cooperation with the Michigan Department of Environmental Quality (MDEQ), has been monitoring the quality of inland lakes in Michigan through the Lake Water Quality Assessment monitoring program. Approximately 100 inland lakes will be sampled per year from 2001 to 2015. Volunteers coordinated by MDEQ started sampling lakes in 1974, and continue to sample to date approximately 250 inland lakes each year through the Cooperative Lakes Monitoring Program (CLMP), Michigan’s volunteer lakes monitoring program. Despite this sampling effort, it is still impossible to physically collect the necessary water-quality measurements for all 3,500 Michigan inland lakes. Therefore, a technique was used by USGS, modeled after Olmanson and others (2001), in cooperation with MDEQ that uses satellite remote sensing to predict water quality in unsampled inland lakes greater than 25 acres. Water-quality characteristics that are associated with water clarity can be predicted for Michigan inland lakes by relating sampled measurements of secchi-disk transparency (SDT) and chlorophyll a concentrations (Chl-a), to satellite imagery. The trophic state index (TSI) which is an indicator of the biological productivity can be calculated based on SDT measurements, Chl-a concentrations, and total phosphorus (TP) concentrations measured near the lake’s surface. Through this process, unsampled inland lakes within the fourteen Landsat satellite scenes encompassing Michigan can be translated into estimated TSI from either predicted SDT or Chl-a (fig. 1).

Periodic Density Structures and the Origin of the Slow Solar Wind

NASA Technical Reports Server (NTRS)

Viall-Kepko, Nicholeen M.; Vourlidas, Angelos

2015-01-01

The source of the slow solar wind has challenged scientists for years. Periodic density structures (PDSs), observed regularly in the solar wind at 1 AU (Astronomical Unit), can be used to address this challenge. These structures have length scales of hundreds to several thousands of megameters and frequencies of tens to hundreds of minutes. Two lines of evidence indicate that PDSs are formed in the solar corona as part of the slow solar wind release and/or acceleration processes. The first is corresponding changes in compositional data in situ, and the second is PDSs observed in the inner Heliospheric Imaging data on board the Solar Terrestrial Relations Observatory (STEREO)/Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) suite. The periodic nature of these density structures is both a useful identifier as well as an important physical constraint on their origin. In this paper, we present the results of tracking periodic structures identified in the inner Heliospheric Imager in SECCHI back in time through the corresponding outer coronagraph (COR2) images. We demonstrate that the PDSs are formed around or below 2.5 solar radii-the inner edge of the COR2 field of view. We compute the occurrence rates of PDSs in 10 days of COR2 images both as a function of their periodicity and location in the solar corona, and we find that this set of PDSs occurs preferentially with a periodicity of approximately 90 minutes and occurs near streamers. Lastly, we show that their acceleration and expansion through COR2 is self-similar, thus their frequency is constant at distances beyond 2.5 solar radii.

Revolution evolution: tracing angular momentum during star and planetary system formation

NASA Astrophysics Data System (ADS)

Davies, Claire Louise

2015-04-01

Stars form via the gravitational collapse of molecular clouds during which time the protostellar object contracts by over seven orders of magnitude. If all the angular momentum present in the natal cloud was conserved during collapse, stars would approach rotational velocities rapid enough to tear themselves apart within just a few Myr. In contrast to this, observations of pre-main sequence rotation rates are relatively slow (∼ 1 - 15 days) indicating that significant quantities of angular momentum must be removed from the star. I use observations of fully convective pre-main sequence stars in two well-studied, nearby regions of star formation (namely the Orion Nebula Cluster and Taurus-Auriga) to determine the removal rate of stellar angular momentum. I find the accretion disc-hosting stars to be rotating at a slower rate and contain less specific angular momentum than the disc-less stars. I interpret this as indicating a period of accretion disc-regulated angular momentum evolution followed by near-constant rotational evolution following disc dispersal. Furthermore, assuming that the age spread inferred from the Hertzsprung-Russell diagram constructed for the star forming region is real, I find that the removal rate of angular momentum during the accretion-disc hosting phase to be more rapid than that expected from simple disc-locking theory whereby contraction occurs at a fixed rotation period. This indicates a more efficient process of angular momentum removal must operate, most likely in the form of an accretion-driven stellar wind or outflow emanating from the star-disc interaction. The initial circumstellar envelope that surrounds a protostellar object during the earliest stages of star formation is rotationally flattened into a disc as the star contracts. An effective viscosity, present within the disc, enables the disc to evolve: mass accretes inwards through the disc and onto the star while momentum migrates outwards, forcing the outer regions of the disc to expand. I used spatially resolved submillimetre detections of the dust and gas components of protoplanetary discs, gathered from the literature, to measure the radial extent of discs around low-mass pre-main sequence stars of ∼ 1-10 Myr and probe their viscous evolution. I find no clear observational evidence for the radial expansion of the dust component. However, I find tentative evidence for the expansion ofthe gas component. This suggests that the evolution of the gas and dust components of protoplanetary discs are likely governed by different astrophysical processes. Observations of jets and outflows emanating from protostars and pre-main sequence stars highlight that it may also be possible to remove angular momentum from the circumstellar material. Using the sample of spatially resolved protoplanetary discs, I find no evidence for angular momentum removal during disc evolution. I also use the spatially resolved debris discs from the Submillimetre Common-User Bolometer Array-2 Observations of Nearby Stars survey to constrain the amount of angular momentum retained within planetary systems. This sample is compared to the protoplanetary disc angular momenta and to the angular momentum contained within pre-stellar cores. I find that significant quantities of angular momentum must be removed during disc formation and disc dispersal. This likely occurs via magnetic braking during the formation of the disc, via the launching of a disc or photo-evaporative wind, and/or via ejection of planetary material following dynamical interactions.

Rossby wave instability in astrophysical discs

NASA Astrophysics Data System (ADS)

Lovelace, R. V. E.; Romanova, M. M.

2014-08-01

A brief review is given of the Rossby wave instability in astrophysical discs. In non-self-gravitating discs, around for example a newly forming stars, the instability can be triggered by an axisymmetric bump at some radius r0 in the disc surface mass-density. It gives rise to exponentially growing non-axisymmetric perturbation (\\propto \\exp \\,({ { i}}m\\phi ) , m = 1,2,…) in the vicinity of r0 consisting of anticyclonic vortices. These vortices are regions of high pressure and consequently act to trap dust particles which in turn can facilitate planetesimal growth in proto-planetary discs. The Rossby vortices in the discs around stars and black holes may cause the observed quasi-periodic modulations of the disc's thermal emission.

Disc Golf: Teaching a Lifetime Activity

ERIC Educational Resources Information Center

Eastham, Susan L.

2015-01-01

Disc golf is a lifetime activity that can be enjoyed by students of varying skill levels and abilities. Disc golf follows the principles of ball golf but is generally easier for students to play and enjoy success. The object of disc golf is similar to ball golf and involves throwing a disc from the teeing area to the target in as few throws as…

26 CFR 1.995-1 - Taxation of DISC income to shareholders.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 26 Internal Revenue 10 2011-04-01 2011-04-01 false Taxation of DISC income to shareholders. 1.995... Taxation of DISC income to shareholders. (a) In general. (1) Under § 1.991-1(a), a corporation which is a... DISC, are subject to taxation on the earnings and profits of the DISC in accordance with the provisions...

Modeling and optimization of an elastic arthroplastic disc for a degenerated disc

NASA Astrophysics Data System (ADS)

Ghouchani, Azadeh; Ravari, Mohammad; Mahmoudi, Farid

2011-10-01

A three-dimensional finite element model (FEM) of the L3-L4 motion segment using ABAQUS v 6.9 has been developed. The model took into account the material nonlinearities and is imposed different loading conditions. In this study, we validated the model by comparison of its predictions with several sets of experimental data. Disc deformation under compression and segmental rotational motions under moment loads for the normal disc model agreed well with the corresponding in vivo studies. By linking ABAQUS with MATLAB 2010.a, we determined the optimal Young s modulus as well as the Poisson's ratio for the artificial disc under different physiologic loading conditions. The results of the present study confirmed that a well-designed elastic arthroplastic disc preferably has an annulus modulus of 19.1 MPa and 1.24 MPa for nucleus section and Poisson ratio of 0.41 and 0.47 respectively. Elastic artificial disc with such properties can then achieve the goal of restoring the disc height and mechanical function of intact disc under different loading conditions and so can reduce low back pain which is mostly caused due to disc degeneration.

Evaluation of Electrospun Nanofiber-Anchored Silicone for the Degenerative Intervertebral Disc

PubMed Central

Riahanizad, S.

2017-01-01

The nucleus pulposus (NP) substitution by polymeric gel is one of the promising techniques for the repair of the degenerative intervertebral disc (IVD). Silicone gel is one of the potential candidates for a NP replacement material. Electrospun fiber anchorage to silicone disc, referred as ENAS disc, may not only improve the biomechanical performances of the gel but it can also improve restoration capability of the gel, which is unknown. This study successfully produced a novel process to anchor any size and shape of NP gel with electrospun fiber mesh. Viscoelastic properties of silicone and ENAS disc were measured using standard experimental techniques and compared with the native tissue properties. Ex vivo mechanical tests were conducted on ENAS disc-implanted rabbit tails to the compare the mechanical stability between intact and ENAS implanted spines. This study found that viscoelastic properties of ENAS disc are higher than silicone disc and comparable to the viscoelastic properties of human NP. The ex vivo studies found that the ENAS disc restore the mechanical functionality of rabbit tail spine, after discectomy of native NP and replacing the NP by ENAS disc. Therefore, the PCL ENF mesh anchoring technique to a NP implant can have clinical potential. PMID:29181144

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chillara, Vamshi Krishna; Pantea, Cristian; Sinha, Dipen N.

Here, we numerically investigate the resonance and vibration characteristics of radial modes of laterally stiffened piezoelectric disc transducers. Lateral stiffening is modeled using a spring and vibration characteristics of the piezo-disc are investigated with increasing lateral stiffness. It is found that the resonant frequency response of the radial modes follows an asymptotic behavior approaching that of a clamped disc with increasing lateral stiffness. The radial mode vibration pattern of the discs is also found to be affected by lateral stiffness. While the vibration pattern of a free disc corresponds to a Bessel function, laterally stiffened discs show edge-effects where theymore » depart from the Bessel-like behavior. In addition, a fully clamped piezo-disc is found to have an extra side-lobe when compared to a free disc. Ultrasonic beam profiles generated from radial modes of laterally stiffened discs are numerically investigated. It is found that the free piezo-disc generates a Bessel beam that has multiple side-lobes. Increasing the lateral stiffness results in a significant reduction of side-lobes in the beam profile. This technique of generating a collimated beam with side-lobe reduction finds significant applications in imaging through concrete, drilling mud, and other highly attenuating materials.« less

Fragmentation of protoplanetary discs around M-dwarfs

NASA Astrophysics Data System (ADS)

Backus, Isaac; Quinn, Thomas

2016-12-01

We investigate the conditions required for planet formation via gravitational instability (GI) and protoplanetary disc (PPD) fragmentation around M-dwarfs. Using a suite of 64 SPH simulations with 106 particles, the parameter space of disc mass, temperature, and radius is explored, bracketing reasonable values based on theory and observation. Our model consists of an equilibrium, gaseous, and locally isothermal disc orbiting a central star of mass M* = M⊙/3. Discs with a minimum Toomre Q of Qmin ≲ 0.9 will fragment and form gravitationally bound clumps. Some previous literature has found Qmin < 1.3-1.5 to be sufficient for fragmentation. Increasing disc height tends to stabilize discs, and when incorporated into Q as Qeff ∝ Q(H/R)α for α = 0.18 is sufficient to predict fragmentation. Some discrepancies in the literature regarding Qcrit may be due to different methods of generating initial conditions (ICs). A series of 15 simulations demonstrates that perturbing ICs slightly out of equilibrium can cause discs to fragment for higher Q. Our method for generating ICs is presented in detail. We argue that GI likely plays a role in PPDs around M-dwarfs and that disc fragmentation at large radii is a plausible outcome for these discs.

Spontaneous regression of posterior epidural migrated lumbar disc fragments: case series.

PubMed

Tarukado, Kiyoshi; Ikuta, Ko; Fukutoku, Yoshiaki; Tono, Osamu; Doi, Toshio

2015-06-01

Posterior epidural migrated lumbar disc fragments is an extremely rare disorder. Surgical treatment was performed in all reported cases. To the best of our knowledge, there are no reported cases of the use of conservative treatment for posterior epidural migrated lumbar disc fragments. To report the possibility of a spontaneous regression of posterior epidural migrated lumbar disc fragments. Case series. Four patients with posterior epidural migrated lumbar disc fragments were treated at Karatsu Red Cross Hospital between April 2008 and August 2010. Spontaneous regression of the posterior epidural migrated lumbar disc fragments with relief of symptoms was observed on magnetic resonance imaging (MRI) in three cases. Another patient underwent surgical treatment. The present and previously reported cases of posterior epidural migrated lumbar disc fragments were analyzed with respect to patient age, imaging features on MRI, the level of the lesion, clinical symptoms, treatment, and outcomes. Conservative treatment was successful, and spontaneous lesion regression was seen on MRI with symptom relief in three cases. Although posterior epidural migrated lumbar disc fragment cases are generally treated surgically, the condition can regress spontaneously over time, as do sequestrated disc fragments. Spontaneous regression of lumbar disc herniations is a widely accepted observation at present. Posterior epidural migrated lumbar disc fragments fall under the sequestrated type of disc herniation. In fact, the course of treatment for posterior epidural migrated lumbar disc fragments should be determined based on the symptoms and examination findings, as in cases of ordinary herniation. However, providing early surgical treatment is important if the patient has acute cauda equina syndrome or the neurologic symptoms worsen over time. Copyright © 2015 Elsevier Inc. All rights reserved.

Disrupted-in-Schizophrenia-1 Attenuates Amyloid-β Generation and Cognitive Deficits in APP/PS1 Transgenic Mice by Reduction of β-Site APP-Cleaving Enzyme 1 Levels

PubMed Central

Deng, Qing-Shan; Dong, Xing-Yu; Wu, Hao; Wang, Wang; Wang, Zhao-Tao; Zhu, Jian-Wei; Liu, Chun-Feng; Jia, Wei-Qiang; Zhang, Yan; Schachner, Melitta; Ma, Quan-Hong; Xu, Ru-Xiang

2016-01-01

Disrupted-in-Schizophrenia-1 (DISC1) is a genetic risk factor for a wide range of major mental disorders, including schizophrenia, major depression, and bipolar disorders. Recent reports suggest a potential role of DISC1 in the pathogenesis of Alzheimer's disease (AD), by referring to an interaction between DISC1 and amyloid precursor protein (APP), and to an association of a single-nucleotide polymorphism in a DISC1 intron and late onset of AD. However, the function of DISC1 in AD remains unknown. In this study, decreased levels of DISC1 were observed in the cortex and hippocampus of 8-month-old APP/PS1 transgenic mice, an animal model of AD. Overexpression of DISC1 reduced, whereas knockdown of DISC1 increased protein levels, but not mRNA levels of β-site APP-Cleaving Enzyme 1 (BACE1), a key enzyme in amyloid-β (Aβ) generation. Reduction of BACE1 protein levels by overexpression of DISC1 was accompanied by an accelerating decline rate of BACE1, and was blocked by the lysosomal inhibitor chloroquine, rather than proteasome inhibitor MG-132. Moreover, overexpression of DISC1 in the hippocampus with an adeno-associated virus reduced the levels of BACE1, soluble Aβ40/42, amyloid plaque density, and rescued cognitive deficits of APP/PS1 transgenic mice. These results indicate that DISC1 attenuates Aβ generation and cognitive deficits of APP/PS1 transgenic mice through promoting lysosomal degradation of BACE1. Our findings provide new insights into the role of DISC1 in AD pathogenesis and link a potential function of DISC1 to the psychiatric symptoms of AD. PMID:26062786

Rat Disc Torsional Mechanics: Effect of Lumbar and Caudal Levels and Axial Compression Load

PubMed Central

Elliott, Dawn M; Espinoza Orías, Alejandro A; Malhotra, Neil R

2009-01-01

Background Context Rat models with altered loading are used to study disc degeneration and mechano-transduction. Given the prominent role of mechanics in disc function and degeneration, it is critical to measure mechanical behavior in order to evaluate changes following model interventions. Axial compression mechanics of the rat disc are representative of the human disc when normalized by geometry, and differences between the lumbar and caudal disc have been quantified in axial compression. No study has quantified rat disc torsional mechanics. Purpose Compare the torsional mechanical behavior of rat lumbar and caudal discs, determine the contribution of combined axial load on torsional mechanics, and compare the torsional properties of rat discs to human lumbar discs. Study Design Cadaveric biomechanical study. Methods Cyclic torsion without compressive load followed by cyclic torsion with a fixed compressive load was applied to rat lumbar and caudal disc levels. Results The apparent torsional modulus was higher in the lumbar region than in the caudal region,: 0.081±0.026 (MPa/°, Mean±SD) for lumbar axially loaded; 0.066±0.028 caudal axially loaded; 0.091±0.033 for lumbar in pure torsion; and 0.056±0.035 for caudal in pure torsion. These values were similar to human disc properties reported in the literature ranging from 0.024 to 0.21 MPa/°. Conclusions Use of the caudal disc as a model may be appropriate if the mechanical focus is within the linear region of the loading regime. These results provide support for use of this animal model in basic science studies with respect to torsional mechanics. PMID:18495544

Adjacent level effects of bi level disc replacement, bi level fusion and disc replacement plus fusion in cervical spine--a finite element based study.

PubMed

Faizan, Ahmad; Goel, Vijay K; Biyani, Ashok; Garfin, Steven R; Bono, Christopher M

2012-03-01

Studies delineating the adjacent level effect of single level disc replacement systems have been reported in literature. The aim of this study was to compare the adjacent level biomechanics of bi-level disc replacement, bi-level fusion and a construct having adjoining level disc replacement and fusion system. In total, biomechanics of four models- intact, bi level disc replacement, bi level fusion and fusion plus disc replacement at adjoining levels- was studied to gain insight into the effects of various instrumentation systems on cranial and caudal adjacent levels using finite element analysis (73.6N+varying moment). The bi-level fusion models are more than twice as stiff as compared to the intact model during flexion-extension, lateral bending and axial rotation. Bi-level disc replacement model required moments lower than intact model (1.5Nm). Fusion plus disc replacement model required moment 10-25% more than intact model, except in extension. Adjacent level motions, facet loads and endplate stresses increased substantially in the bi-level fusion model. On the other hand, adjacent level motions, facet loads and endplate stresses were similar to intact for the bi-level disc replacement model. For the fusion plus disc replacement model, adjacent level motions, facet loads and endplate stresses were closer to intact model rather than the bi-level fusion model, except in extension. Based on our finite element analysis, fusion plus disc replacement procedure has less severe biomechanical effects on adjacent levels when compared to bi-level fusion procedure. Bi-level disc replacement procedure did not have any adverse mechanical effects on adjacent levels. Copyright © 2011 Elsevier Ltd. All rights reserved.

Changes in intervertebral disc cross-sectional area with bed rest and space flight

NASA Technical Reports Server (NTRS)

LeBlanc, A. D.; Evans, H. J.; Schneider, V. S.; Wendt, R. E. 3rd; Hedrick, T. D.

1994-01-01

STUDY DESIGN. We measured the cross-sectional area of the intervertebral discs of normal volunteers after an overnight rest; before, during, and after 5 or 17 weeks of bed rest; and before and after 8 days of weightlessness. OBJECTIVES. This study sought to determine the degree of expansion of the lumbar discs resulting from bed rest and space flight. SUMMARY OF BACKGROUND DATA. Weightlessness and bed rest, an analog for weightlessness, reduce the mechanical loading on the musculoskeletal system. When unloaded, intervertebral discs will expand, increasing the nutritional diffusion distance and altering the mechanical properties of the spine. METHODS. Magnetic resonance imaging was used to measure the cross-sectional area and transverse relaxation time (T2) of the intervertebral discs. RESULTS. Overnight or longer bed rest causes expansion of the disc area, which reaches an equilibrium value of about 22% (range 10-40%) above baseline within 4 days. Increases in disc area were associated with modest increases in disc T2. During bed rest, disc height increased approximately 1 mm, about one-half of previous estimates based on body height measurements. After 5 weeks of bed rest, disc area returned to baseline within a few days of ambulation, whereas after 17 weeks, disc area remained above baseline 6 weeks after reambulation. After 8 days of weightlessness, T2, disc area, and lumbar length were not significantly different from baseline values 24 hours after landing. CONCLUSIONS. Significant adaptive changes in the intervertebral discs can be expected during weightlessness. These changes, which are rapidly reversible after short-duration flights, may be an important factor during and after long-duration missions.

The comparative analysis of rocks' resistance to forward-slanting disc cutters and traditionally installed disc cutters

NASA Astrophysics Data System (ADS)

Zhang, Zhao-Huang; Fei, Sun; Liang, Meng

2016-08-01

At present, disc cutters of a full face rock tunnel boring machine are mostly mounted in the traditional way. Practical use in engineering projects reveals that this installation method not only heavily affects the operation life of disc cutters, but also increases the energy consumption of a full face rock tunnel boring machine. To straighten out this issue, therefore, a rock-breaking model is developed for disc cutters' movement after the research on the rock breaking of forward-slanting disc cutters. Equations of its displacement are established based on the analysis of velocity vector of a disc cutter's rock-breaking point. The functional relations then are brought forward between the displacement parameters of a rock-breaking point and its coordinate through the analysis of micro displacement of a rock-breaking point. Thus, the geometric equations of rock deformation are derived for the forward-slanting installation of disc cutters. With a linear relationship remaining between the acting force and its deformation either before or after the leap breaking, the constitutive relation of rock deformation can be expressed in the form of generalized Hooke law, hence the comparative analysis of the variation in the resistance of rock to the disc cutters mounted in the forward-slanting way with that in the traditional way. It is discovered that with the same penetration, strain of the rock in contact with forward-slanting disc cutters is apparently on the decline, in other words, the resistance of rock to disc cutters is reduced. Thus wear of disc cutters resulted from friction is lowered and energy consumption is correspondingly decreased. It will be useful for the development of installation and design theory of disc cutters, and significant for the breakthrough in the design of full face rock tunnel boring machine.

The vertical structure of gaseous galaxy discs in cold dark matter haloes

NASA Astrophysics Data System (ADS)

Benítez-Llambay, Alejandro; Navarro, Julio F.; Frenk, Carlos S.; Ludlow, Aaron D.

2018-01-01

We study the vertical structure of polytropic centrifugally supported gaseous discs embedded in cold dark matter (CDM) haloes. At fixed radius, R, the shape of the vertical density profile depends weakly on whether the disc is self-gravitating (SG) or non-self-gravitating (NSG). The disc 'characteristic' thickness, zH, set by the midplane sound speed and circular velocity, zNSG = (cs/Vc)R, in the NSG case, and by the sound speed and surface density, z_SG = c_s^2/GΣ, in SG discs, is smaller than zSG and zNSG. SG discs are typically Toomre unstable, NSG discs are stable. Exponential discs in CDM haloes with roughly flat circular velocity curves 'flare' outwards. Flares in mono abundance or coeval populations in galaxies like the Milky Way are thus not necessarily due to radial migration. For the polytropic equation of state of the Evolution and Assembly of GaLaxies and their Environments (EAGLE) simulations, discs that match observational constraints are NSG for Md < 3 × 109 M⊙ and SG at higher masses, if fully gaseous. We test these analytic results using a set of idealized smoothed particle hydrodynamic simulations and find excellent agreement. Our results clarify the role of the gravitational softening on the thickness of simulated discs, and on the onset of radial instabilities. EAGLE low-mass discs are NSG so the softening plays no role in their vertical structure. High-mass discs are expected to be SG and unstable, and may be artificially thickened and stabilized unless gravity is well resolved. Simulations with spatial resolution high enough to not compromise the vertical structure of a disc also resolve the onset of their instabilities, but the converse is not true.

Modelling the chemistry of a gravitationally unstable protoplanetary disc

NASA Astrophysics Data System (ADS)

Ilee, J. D.; Boley, A. C.; Caselli, P.; Durisen, R. H.; Hartquist, T. W.; Rawlings, J. M. C.

2011-05-01

Until now, axisymmetric, α-disc simulations have been adopted to describe the dynamics used in the construction of chemical models of protoplanetary discs. While this approach is reasonable for many discs, it is not appropriate for young, massive discs in which self-gravity is important. Spiral waves and shocks cause significant temperature and density variations which affect the chemistry. We have used a dynamical model of solar mass star surrounded by a massive (0.39 M⊙), self-gravitating disc to model the chemistry of one of these objects.

[In situ analysis of pathomechanisms of human intervertebral disc degeneration].

PubMed

Weiler, C

2013-11-01

Low back pain is one of the major causes of pain and disability in the western world, with a constantly rising life-time prevalence of approximately 60-85 %. Degeneration of the intervertebral disc is believed to be a major cause of low back pain. Semiquantitative macroscopic and microscopic changes of the intervertebral disc were assessed and classified. Furthermore additional methods, such as immunohistochemistry, in situ hybridization and in situ zymography were used to analyze phenotypic cellular and matrix changes. We have developed and tested a practicable, valid and reliable histological classification system for lumbar discs which can serve as a morphological reference framework to allow more sophisticated molecular biological studies on the pathogenesis of ageing and degeneration of discs. Secondly, we were able to demonstrate that intrinsic (genetic) and extrinsic (e.g. overweight) factors have a profound effect on the process of disc degeneration. Cells with a notochord-like phenotype are present in a considerable fraction of adult lumbar intervertebral discs. The presence of these cells is associated with distinct features of (early) age-related disc degeneration. During the process of disc degeneration, the intervertebral disc shows a progressive and significant reduction in height due to tissue resorption. This matrix loss is related to an imbalance between matrix synthesis and degradation. During this process an inflammatory reaction takes place and resident disc cells are causatively involved. In summary, disc degeneration is a multifactorial disease with a strong intrinsic (hereditary) and extrinsic (e.g. mechanical factors) background. The process starts as early as in the second decade of life and shows high interindividual differences. The loss of regenerative capacity in the intervertebral disc is probably related to the loss of stem cells, e.g. notochord-like cells. Resident disc cells are involved in the inflammatory reaction with increased matrix degradation, resorption and reduced matrix synthesis.

Structure and function of the temporomandibular joint disc: implications for tissue engineering.

PubMed

Detamore, Michael S; Athanasiou, Kyriacos A

2003-04-01

The temporomandibular joint (TMJ) disc is a little understood structure that, unfortunately, exhibits a plethora of pathologic disorders. Tissue engineering approaches may be warranted to address TMJ disc pathophysiology, but first a clear understanding of structure-function relationships needs to be developed, especially as they relate to the regenerative potential of the tissue. In this review, we correlate the biochemical content of the TMJ disc to its mechanical behavior and discuss what this correlation infers for tissue engineering studies of the TMJ disc. The disc of the TMJ exhibits a somewhat biconcave shape, being thicker in the anterior and posterior bands and thinner in the intermediate zone. The disc, which is certainly an anisotropic and nonhomogeneous tissue, consists almost entirely of type I collagen with trace amounts of type II and other types. In general, collagen fibers in the intermediate zone appear to run primarily in an anteroposterior direction and in a ringlike fashion around the periphery. Collagen orientation is reflected in higher tensile stiffness and strength in the center anteroposteriorly than mediolaterally and in the anterior and posterior bands than the intermediate zone mediolaterally. Tensile tests have shown the disc is stiffer and stronger in the direction of the collagen fibers. Elastin fibers in general appear along the collagen fibers and most likely function in restoring and retaining disc form after loading. The 2 primary glycosaminoglycans of the disc by far are chondroitin sulfate and dermatan sulfate, although their distribution is not clear. Compression studies are conflicting, but evidence suggests the disc is compressively stiffest in the center. Only a few tissue engineering studies of the TMJ disc have been performed to date. Tissue engineering studies must take advantage of existing information for experimental design and construct validation, and more research is necessary to characterize the disc to create a clearer picture of our goals in tissue engineering the TMJ disc. Copyright 2003 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg 61:494-506, 2003

Optical Coherence Tomography Angiography of Optic Disc Perfusion in Glaucoma

PubMed Central

Jia, Yali; Wei, Eric; Wang, Xiaogang; Zhang, Xinbo; Morrison, John C.; Parikh, Mansi; Lombardi, Lori H.; Gattey, Devin M.; Armour, Rebecca L.; Edmunds, Beth; Kraus, Martin F.; Fujimoto, James G.; Huang, David

2014-01-01

Purpose To compare optic disc perfusion between normal and glaucoma subjects using optical coherence tomography (OCT) angiography and detect optic disc perfusion changes in glaucoma. Design Observational, cross-sectional study. Participants Twenty-four normal subjects and 11 glaucoma patients were included. Methods One eye of each subject was scanned by a high-speed 1050 nm wavelength swept-source OCT instrument. The split-spectrum amplitude-decorrelation angiography algorithm (SSADA) was used to compute three-dimensional optic disc angiography. A disc flow index was computed from four registered scans. Confocal scanning laser ophthalmoscopy (cSLO) was used to measure disc rim area, and stereo photography was used to evaluate cup/disc ratios. Wide field OCT scans over the discs were used to measure retinal nerve fiber layer (NFL) thickness. Main Outcome Measurements Variability was assessed by coefficient of variation (CV). Diagnostic accuracy was assessed by sensitivity and specificity. Comparisons between glaucoma and normal groups were analyzed by Wilcoxon rank-sum test. Correlations between disc flow index, structural assessments, and visual field (VF) parameters were assessed by linear regression. Results In normal discs, a dense microvascular network was visible on OCT angiography. This network was visibly attenuated in glaucoma subjects. The intra-visit repeatability, inter-visit reproducibility, and normal population variability of the optic disc flow index were 1.2%, 4.2%, and 5.0% CV respectively. The disc flow index was reduced by 25% in the glaucoma group (p = 0.003). Sensitivity and specificity were both 100% using an optimized cutoff. The flow index was highly correlated with VF pattern standard deviation (R2 = 0.752, p = 0.001). These correlations were significant even after accounting for age, cup/disc area ratio, NFL, and rim area. Conclusions OCT angiography, generated by the new SSADA algorithm, repeatably measures optic disc perfusion. OCT angiography could be useful in the evaluation of glaucoma and glaucoma progression. PMID:24629312

Counter-rotating accretion discs

NASA Astrophysics Data System (ADS)

Dyda, S.; Lovelace, R. V. E.; Ustyugova, G. V.; Romanova, M. M.; Koldoba, A. V.

2015-01-01

Counter-rotating discs can arise from the accretion of a counter-rotating gas cloud on to the surface of an existing corotating disc or from the counter-rotating gas moving radially inwards to the outer edge of an existing disc. At the interface, the two components mix to produce gas or plasma with zero net angular momentum which tends to free-fall towards the disc centre. We discuss high-resolution axisymmetric hydrodynamic simulations of viscous counter-rotating discs for the cases where the two components are vertically separated and radially separated. The viscosity is described by an isotropic α-viscosity including all terms in the viscous stress tensor. For the vertically separated components, a shear layer forms between them and the middle part of this layer free-falls to the disc centre. The accretion rates are increased by factors of ˜102-104 over that for a conventional disc rotating in one direction with the same viscosity. The vertical width of the shear layer and the accretion rate are strongly dependent on the viscosity and the mass fraction of the counter-rotating gas. In the case of radially separated components where the inner disc corotates and the outer disc rotates in the opposite direction, a gap between the two components opens and closes quasi-periodically. The accretion rates are ≳25 times larger than those for a disc rotating in one direction with the same viscosity.

Effect of Air-Polishing on Titanium Surfaces, Biofilm Removal, and Biocompatibility: A Pilot Study

PubMed Central

Bennani, Vincent; Hwang, Linda; Tawse-Smith, Andrew; Dias, George J.; Cannon, Richard D.

2015-01-01

Purpose. The aims of this in vitro study were to evaluate morphological changes induced by glycine powder air-polishing on titanium surfaces, biofilm removal, and biocompatibility. Material and Methods. Titanium grade IV discs were allocated into two groups: (1) discs without biofilm and (2) discs for Streptococcus mutans biofilm formation. Discs in each group were further subdivided into (a) no treatment and (b) air-polishing treatment with glycine powder. Discs were characterized by scanning electron microscopy (SEM), electron-dispersive spectroscopy (EDS), and confocal microscopy. Bacterial biofilms were quantified using a crystal violet dye-binding assay. Biocompatibility was evaluated by measuring the coverage and viability of L929 fibroblast cells cultured on the discs. Results. Air-polishing increased the roughness of treated discs (P < 0.05). EDS analysis did not show significant differences in the chemical composition of treated and nontreated discs. The amount of residual biofilm on treated discs was 8.6-fold lower than untreated controls (P < 0.05). Coverage of treated discs by fibroblasts was half that of untreated discs (P < 0.05) although both groups had the same cell viability. Conclusions. Air-polishing removed a significant amount of biofilm from titanium surfaces. The “polishing” was accompanied by increased surface roughness, but there were no changes in chemical and elemental compositions, nor the biocompatibility. PMID:26881198

Use NASA GES DISC Data in ArcGIS

NASA Technical Reports Server (NTRS)

Yang, Wenli; Pham, Long B.; Kempler, Steve

2015-01-01

This presentation describes GIS relevant data at NASA Goddard Earth Sciences Data and Information Services Center (GES DISC), GES DISC Services and Support for GIS Users, and use cases of GES DISC data in ArcGIS.

Accretion disc wind variability in the states of the microquasar GRS 1915+105

NASA Astrophysics Data System (ADS)

Neilsen, Joseph; Petschek, Andrew J.; Lee, Julia C.

2012-03-01

Continuing our study of the role and evolution of accretion disc winds in the microquasar GRS 1915+105, we present high-resolution spectral variability analysis of the β and γ states with the Chandra High-Energy Transmission Grating Spectrometer. By tracking changes in the absorption lines from the accretion disc wind, we find new evidence that radiation links the inner and outer accretion discs on a range of time-scales. As the central X-ray flux rises during the high-luminosity γ state, we observe the progressive overionization of the wind. In the β state, we argue that changes in the inner disc leading to the ejection of a transient 'baby jet' also quench the highly ionized wind from the outer disc. Our analysis reveals how the state, structure and X-ray luminosity of the inner accretion disc all conspire to drive the formation and variability of highly ionized accretion disc winds.

Non-Axisymmetric Line Driven Disc Winds II - Full Velocity Gradient

NASA Astrophysics Data System (ADS)

Dyda, Sergei; Proga, Daniel

2018-05-01

We study non-axisymetric features of 3D line driven winds in the Sobolev approximation, where the optical depth is calculated using the full velocity gradient. We find that non-axisymmetric density features, so called clumps, form primarily at the base of the wind on super-Sobolev length scales. The density of clumps differs by a factor of ˜3 from the azimuthal average, the magnitude of their velocity dispersion is comparable to the flow velocity and they produce ˜20% variations in the column density. Clumps may be observable because differences in density produce enhancements in emission and absorption profiles or through their velocity dispersion which enhances line broadening.

[Diagnostic imaging of changes of the canine intervertebral disc].

PubMed

Harder, Lisa K

2016-10-12

Intervertebral disc degeneration can cause intervertebral disc herniation. Diagnostic imaging, including radiography, computed tomography and magnetic resonance imaging, is the most important tool in diagnosis. Firstly, an overview of macroscopic and biochemical physiology and pathology of the intervertebral disc will be given. Subsequently, the physics of diagnostic imaging and the appearance of intervertebral disc degeneration and displacement in several imaging methods are described.

108. DETAIL OF DENVER DISC FILTER IN CO91107, SUCTION END. ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

108. DETAIL OF DENVER DISC FILTER IN CO-91-107, SUCTION END. NOTE BEARING HOUSING WITH CAST LOGO, SUCTION PIPE GOING OFF TO THE RIGHT, AND FILTER DISC IN BACKGROUND. VACUUM INSIDE DISCS FURTHER DEWATERED CONCENTRATE. AS DISC SLOWLY ROTATED A BAR SCRAPED DRIED CONCENTRATE FROM OUTSIDE OF FILTER CLOTH. - Shenandoah-Dives Mill, 135 County Road 2, Silverton, San Juan County, CO

Line-driven ablation of circumstellar discs - I. Optically thin decretion discs of classical Oe/Be stars.

PubMed

Kee, Nathaniel Dylan; Owocki, Stanley; Sundqvist, J O

2016-05-21

The extreme luminosities of massive, hot OB stars drive strong stellar winds through line-scattering of the star's UV continuum radiation. For OB stars with an orbiting circumstellar disc, we explore here the effect of such line-scattering in driving an ablation of material from the disc's surface layers, with initial focus on the marginally optically thin decretion discs of classical Oe and Be stars. For this we apply a multidimensional radiation-hydrodynamics code that assumes simple optically thin ray tracing for the stellar continuum, but uses a multiray Sobolev treatment of the line transfer; this fully accounts for the efficient driving by non-radial rays, due to desaturation of line-absorption by velocity gradients associated with the Keplerian shear in the disc. Results show a dense, intermediate-speed surface ablation, consistent with the strong, blueshifted absorption of UV wind lines seen in Be shell stars that are observed from near the disc plane. A key overall result is that, after an initial adjustment to the introduction of the disc, the asymptotic disc destruction rate is typically just an order-unity factor times the stellar wind mass-loss rate. For optically thin Be discs, this leads to a disc destruction time of order months to years, consistent with observationally inferred disc decay times. The much stronger radiative forces of O stars reduce this time to order days, making it more difficult for decretion processes to sustain a disc in earlier spectral types, and so providing a natural explanation for the relative rarity of Oe stars in the Galaxy. Moreover, the decrease in line-driving at lower metallicity implies both a reduction in the winds that help spin-down stars from near-critical rotation, and a reduction in the ablation of any decretion disc; together these provide a natural explanation for the higher fraction of classical Be stars, as well as the presence of Oe stars, in the lower metallicity Magellanic Clouds. We conclude with a discussion of future extensions to study line-driven ablation of denser, optically thick, accretion discs of pre-main-sequence massive stars.

Genome-wide analysis of pain-, nerve- and neurotrophin -related gene expression in the degenerating human annulus

PubMed Central

2012-01-01

Background In spite of its high clinical relevance, the relationship between disc degeneration and low back pain is still not well understood. Recent studies have shown that genome-wide gene expression studies utilizing ontology searches provide an efficient and valuable methodology for identification of clinically relevant genes. Here we use this approach in analysis of pain-, nerve-, and neurotrophin-related gene expression patterns in specimens of human disc tissue. Control, non-herniated clinical, and herniated clinical specimens of human annulus tissue were studied following Institutional Review Board approval. Results Analyses were performed on more generated (Thompson grade IV and V) discs vs. less degenerated discs (grades I-III), on surgically operated discs vs. control discs, and on herniated vs. control discs. Analyses of more degenerated vs. less degenerated discs identified significant upregulation of well-recognized pain-related genes (bradykinin receptor B1, calcitonin gene-related peptide and catechol-0-methyltransferase). Nerve growth factor was significantly upregulated in surgical vs. control and in herniated vs. control discs. All three analyses also found significant changes in numerous proinflammatory cytokine- and chemokine-related genes. Nerve, neurotrophin and pain-ontology searches identified many matrix, signaling and functional genes which have known importance in the disc. Immunohistochemistry was utilized to confirm the presence of calcitonin gene-related peptide, catechol-0-methyltransferase and bradykinin receptor B1 at the protein level in the human annulus. Conclusions Findings point to the utility of microarray analyses in identification of pain-, neurotrophin and nerve-related genes in the disc, and point to the importance of future work exploring functional interactions between nerve and disc cells in vitro and in vivo. Nerve, pain and neurotrophin ontology searches identified numerous changes in proinflammatory cytokines and chemokines which also have significant relevance to disc biology. Since the degenerating human disc is primarily an avascular tissue site into which disc cells have contributed high levels of proinflammatory cytokines, these substances are not cleared from the tissue and remain there over time. We hypothesize that as nerves grow into the human annulus, they encounter a proinflammatory cytokine-rich milieu which may sensitize nociceptors and exacerbate pain production. PMID:22963171

Line-driven ablation of circumstellar discs – I. Optically thin decretion discs of classical Oe/Be stars

PubMed Central

Kee, Nathaniel Dylan; Owocki, Stanley; Sundqvist, J. O.

2016-01-01

The extreme luminosities of massive, hot OB stars drive strong stellar winds through line-scattering of the star's UV continuum radiation. For OB stars with an orbiting circumstellar disc, we explore here the effect of such line-scattering in driving an ablation of material from the disc's surface layers, with initial focus on the marginally optically thin decretion discs of classical Oe and Be stars. For this we apply a multidimensional radiation-hydrodynamics code that assumes simple optically thin ray tracing for the stellar continuum, but uses a multiray Sobolev treatment of the line transfer; this fully accounts for the efficient driving by non-radial rays, due to desaturation of line-absorption by velocity gradients associated with the Keplerian shear in the disc. Results show a dense, intermediate-speed surface ablation, consistent with the strong, blueshifted absorption of UV wind lines seen in Be shell stars that are observed from near the disc plane. A key overall result is that, after an initial adjustment to the introduction of the disc, the asymptotic disc destruction rate is typically just an order-unity factor times the stellar wind mass-loss rate. For optically thin Be discs, this leads to a disc destruction time of order months to years, consistent with observationally inferred disc decay times. The much stronger radiative forces of O stars reduce this time to order days, making it more difficult for decretion processes to sustain a disc in earlier spectral types, and so providing a natural explanation for the relative rarity of Oe stars in the Galaxy. Moreover, the decrease in line-driving at lower metallicity implies both a reduction in the winds that help spin-down stars from near-critical rotation, and a reduction in the ablation of any decretion disc; together these provide a natural explanation for the higher fraction of classical Be stars, as well as the presence of Oe stars, in the lower metallicity Magellanic Clouds. We conclude with a discussion of future extensions to study line-driven ablation of denser, optically thick, accretion discs of pre-main-sequence massive stars. PMID:27346978

A t(1;11) translocation linked to schizophrenia and affective disorders gives rise to aberrant chimeric DISC1 transcripts that encode structurally altered, deleterious mitochondrial proteins

PubMed Central

Eykelenboom, Jennifer E.; Briggs, Gareth J.; Bradshaw, Nicholas J.; Soares, Dinesh C.; Ogawa, Fumiaki; Christie, Sheila; Malavasi, Elise L.V.; Makedonopoulou, Paraskevi; Mackie, Shaun; Malloy, Mary P.; Wear, Martin A.; Blackburn, Elizabeth A.; Bramham, Janice; McIntosh, Andrew M.; Blackwood, Douglas H.; Muir, Walter J.; Porteous, David J.; Millar, J. Kirsty

2012-01-01

Disrupted-In-Schizophrenia 1 (DISC1) was identified as a risk factor for psychiatric illness through its disruption by a balanced chromosomal translocation, t(1;11)(q42.1;q14.3), that co-segregates with schizophrenia, bipolar disorder and depression. We previously reported that the translocation reduces DISC1 expression, consistent with a haploinsufficiency disease model. Here we report that, in lymphoblastoid cell lines, the translocation additionally results in the production of abnormal transcripts due to the fusion of DISC1 with a disrupted gene on chromosome 11 (DISC1FP1/Boymaw). These chimeric transcripts encode abnormal proteins, designated CP1, CP60 and CP69, consisting of DISC1 amino acids 1–597 plus 1, 60 or 69 amino acids, respectively. The novel 69 amino acids in CP69 induce increased α-helical content and formation of large stable protein assemblies. The same is predicted for CP60. Both CP60 and CP69 exhibit profoundly altered functional properties within cell lines and neurons. Both are predominantly targeted to mitochondria, where they induce clustering and loss of membrane potential, indicative of severe mitochondrial dysfunction. There is currently no access to neural material from translocation carriers to confirm these findings, but there is no reason to suppose that these chimeric transcripts will not also be expressed in the brain. There is thus potential for the production of abnormal chimeric proteins in the brains of translocation carriers, although at substantially lower levels than for native DISC1. The mechanism by which inheritance of the translocation increases risk of psychiatric illness may therefore involve both DISC1 haploinsufficiency and mitochondrial deficiency due to the effects of abnormal chimeric protein expression. GenBank accession numbers: DISC1FP1 (EU302123), Boymaw (GU134617), der 11 chimeric transcript DISC1FP1 exon 2 to DISC1 exon 9 (JQ650115), der 1 chimeric transcript DISC1 exon 4 to DISC1FP1 exon 4 (JQ650116), der 1 chimeric transcript DISC1 exon 6 to DISC1FP1 exon 3a (JQ650117). PMID:22547224

A study of the effect of bulges on bar formation in disc galaxies

NASA Astrophysics Data System (ADS)

Kataria, Sandeep Kumar; Das, Mousumi

2018-04-01

We use N-body simulations of bar formation in isolated galaxies to study the effect of bulge mass and bulge concentration on bar formation. Bars are global disc instabilities that evolve by transferring angular momentum from the inner to outer discs and to the dark matter halo. It is well known that a massive spherical component such as halo in a disc galaxy can make it bar stable. In this study, we explore the effect of another spherical component, the bulge, on bar formation in disc galaxies. In our models, we vary both the bulge mass and concentration. We have used two sets of models: one that has a dense bulge and high surface density disc, and the other model has a less concentrated bulge and a lighter disc. In both models, we vary the bulge to disc mass fraction from 0 to 0.7. Simulations of both the models show that there is an upper cut-off in bulge-to-disc mass ratio Mb/Md above which bars cannot form; the cut-off is smaller for denser bulges (Mb/Md = 0.2) compared to less denser ones (Mb/Md = 0.5). We define a new criterion for bar formation in terms of the ratio of bulge to total radial force (Fb/Ftot) at the disc scale lengths above which bars cannot form. We find that if Fb/Ftot > 0.35, a disc is stable and a bar cannot form. Our results indicate that early-type disc galaxies can still form strong bars in spite of having massive bulges.

A tilted and warped inner accretion disc around a spinning black hole: an analytical solution

NASA Astrophysics Data System (ADS)

Chakraborty, Chandrachur; Bhattacharyya, Sudip

2017-08-01

Inner accretion disc around a black hole provides a rare, natural probe to understand the fundamental physics of the strong gravity regime. A possible tilt of such a disc, with respect to the black hole spin equator, is important. This is because such a tilt affects the observed spectral and timing properties of the disc X-ray emission via Lense-Thirring precession, which could be used to test the theoretical predictions regarding the strong gravity. Here, we analytically solve the steady, warped accretion disc equation of Scheurer and Feiler, and find an expression of the radial profile of the disc tilt angle. In our exact solution, considering a prograde disc around a slowly spinning black hole, we include the inner part of the disc, which was not done earlier in this formalism. Such a solution is timely, as a tilted inner disc has recently been inferred from X-ray spectral and timing features of the accreting black hole H1743-322. Our tilt angle radial profile expression includes observationally measurable parameters, such as black hole mass and Kerr parameter, and the disc inner edge tilt angle Win, and hence can be ideal to confront observations. Our solution shows that the disc tilt angle in 10-100 gravitational radii is a significant fraction of the disc outer edge tilt angle, even for Win = 0. Moreover, tilt angle radial profiles have humps in ˜10-1000 gravitational radii for some sets of parameter values, which should have implications for observed X-ray features.

Disc-halo interactions in ΛCDM

NASA Astrophysics Data System (ADS)

Bauer, Jacob S.; Widrow, Lawrence M.; Erkal, Denis

2018-05-01

We present a new method for embedding a stellar disc in a cosmological dark matter halo and provide a worked example from a Λ cold dark matter zoom-in simulation. The disc is inserted into the halo at a redshift z = 3 as a zero-mass rigid body. Its mass and size are then increased adiabatically while its position, velocity, and orientation are determined from rigid-body dynamics. At z = 1, the rigid disc (RD) is replaced by an N-body disc whose particles sample a three-integral distribution function (DF). The simulation then proceeds to z = 0 with live disc (LD) and halo particles. By comparison, other methods assume one or more of the following: the centre of the RD during the growth phase is pinned to the minimum of the halo potential, the orientation of the RD is fixed, or the live N-body disc is constructed from a two rather than three-integral DF. In general, the presence of a disc makes the halo rounder, more centrally concentrated, and smoother, especially in the innermost regions. We find that methods in which the disc is pinned to the minimum of the halo potential tend to overestimate the amount of adiabatic contraction. Additionally, the effect of the disc on the subhalo distribution appears to be rather insensitive to the disc insertion method. The LD in our simulation develops a bar that is consistent with the bars seen in late-type spiral galaxies. In addition, particles from the disc are launched or `kicked up' to high galactic latitudes.

Water and Salt Stresses, Kinetin and Protein Synthesis in Tobacco Leaves 1

PubMed Central

Ben-Zioni, Aliza; Itai, C.; Vaadia, Y.

1967-01-01

The capacity of tobacco (Nicotiana rustica) leaf discs to incorporate l-leucine 14C into proteins was measured. Leaf discs were obtained from plants which experienced soil water depletion, or which were exposed to a saline or osmotic stress in the root medium. The stresses were brief of relatively short duration and water potential did not decrease below 4 bars in the root media. Leaf discs were sampled 2 hours after stress removal, achieved by reirrigation, or replacement of saline and osmotic solutions with normal nutrient solution. Plants were always turgid when leaves were sampled. All stressed tissues showed reduced capacity to incorporate l-leucine 14C into protein. The reduction was about 50% and could not be attributed either to reduced uptake into the discs, or to possible isotopic dilution. Incorporation decreased progressively with leaf age in control discs as well as in stressed leaf discs. At all ages tested, incorporation in stressed discs was lower than that of the control. Full recovery of incorporation capacity in stressed discs was obtained when discs were sampled 72 hours after stress removal but not earlier. Kinetin pretreatment prior to incubation with labelled leucine partially restored incorporation in stressed discs. The differences in response to kinetin of stressed and control discs suggest a lower endogenous level of cytokinins in the stressed discs. The results were qualitatively similar regardless of the kind of stress given to the plants during pretreatment. This supports the hypothesis that the normal supply of root cytokinins is important in shoot metabolism. PMID:16656515

Correlating Corneal Biomechanics and Ocular Biometric Properties with Lamina Cribrosa Measurements in Healthy Subjects.

PubMed

Pérez Bartolomé, Francisco; Martínez de la Casa, Jose María; Camacho Bosca, Irene; Sáenz-Francés, Federico; Aguilar Munoa, Soledad; Martín Juan, Alberto; Garcia-Feijoo, Julian

2018-01-01

To examine interrelations between corneal biomechanics, ocular biometric variables and optic disc size (ODS), lamina cribosa depth (LCD) or thickness (LCT) in a healthy population. In a cross-sectional case-control study, the following measurements were made in 81 eyes of 81 participants: axial length, anterior chamber depth, lens thickness, and central corneal thickness using the optical biometer Lenstar LS900; and corneal hysteresis (CH), corneal resistance factor (CRF), Goldman-correlated intraocular pressure (IOPg), and corneal-compensated IOP (IOPcc) using the Ocular Response Analyzer. Serial horizontal enhanced depth imaging optical coherence tomography (EDI OCT) B-scans of the optic nerve head were obtained in each participant. Mean ODS, mean LCD, and mean LCT were measured in 11 equally spaced horizontal B-scans, excluding the LC insertion area under Bruch's membrane and scleral rim. LCD was measured in 74 of 81 eyes (91.36%); LCT in 60/81 (75.3%); ODS in 81/81 (100%). CRF was poorly, but significantly, correlated with LCT (Pearson's R = 0.264; P = 0.045). IOPcc, IOPg, CH, and ocular biometrics variables were poorly (non-significantly) correlated with LCD, LCT, and ODS. CRF was poorly but directly correlated with LCT. No association was detected between CH or ocular biometric variables and ODS, LCD, or LCT.

Thermophysical modelling for high-resolution digital terrain models

NASA Astrophysics Data System (ADS)

Pelivan, I.

2018-07-01

A method is presented for efficiently calculating surface temperatures for highly resolved celestial body shapes. A thorough investigation of the necessary conditions leading to reach model convergence shows that the speed of surface temperature convergence depends on factors such as the quality of initial boundary conditions, thermal inertia, illumination conditions, and resolution of the numerical depth grid. The optimization process to shorten the simulation time while increasing or maintaining the accuracy of model results includes the introduction of facet-specific boundary conditions such as pre-computed temperature estimates and pre-evaluated simulation times. The individual facet treatment also allows for assigning other facet-specific properties such as local thermal inertia. The approach outlined in this paper is particularly useful for very detailed digital terrain models in combination with unfavourable illumination conditions such as little-to-no sunlight at all for a period of time as experienced locally on comet 67P/Churyumov-Gerasimenko. Possible science applications include thermal analysis of highly resolved local (landing) sites experiencing seasonal, environment, and lander shadowing. In combination with an appropriate roughness model, the method is very suitable for application to disc-integrated and disc-resolved data. Further applications are seen where the complexity of the task has led to severe shape or thermophysical model simplifications such as in studying surface activity or thermal cracking.

Multiple Ion Implantation Effects on Wear and Wet Ability of Polyethylene Based Polymers

NASA Astrophysics Data System (ADS)

Torrisi, L.; Visco, A. M.; Campo, N.

2004-10-01

Polyethylene based polymers were ion implanted with multiple irradiations of different ions (N+, Ar+ and Kr+) at energies between 30 keV and 300 keV and doses ranging between 1013 and 1016 ions/cm2. The ion implantation dehydrogenises the polyethylene inducing cross-link effects in the residual polymer carbons. At high doses the irradiated surface show properties similar to graphite surfaces. The depth of the modified layers depends on the ion range in polyethylene at the incident ion energy. The chemical modification depends on the implanted doses and on the specie of the incident ions. A "pin-on-disc" machine was employed to measure the polymer wear against AISI-316 L stainless steel. A "contact-angle-test" machine was employed to measure the wet ability of the polymer surface for 1 μl pure water drop. Measurements demonstrate that the multiple ion implantation treatments decrease the surface wear and the surface wetting and produce a more resistant polymer surface. The properties of the treated surfaces improves the polymer functionality for many bio-medical applications, such as those relative to the polyethylene friction discs employed in knee and hip prosthesis joints. The possibility to use multiply ion implantations of polymers with traditional ion implanters and with laser ion sources producing plasmas is investigated.

Optic Disc Drusen in Children

PubMed Central

Chang, Melinda Y.; Pineles, Stacy L.

2016-01-01

Optic disc drusen occur in 0.4% of children and consist of acellular intracellular and extracellular deposits that often become calcified over time. They are typically buried early in life and generally become superficial, and therefore visible, later in childhood, at the average age of 12 years. Their main clinical significance lies in the ability of optic disc drusen, particularly when buried, to simulate true optic disc edema. Misdiagnosing drusen as true disc edema may lead to an invasive and unnecessary workup for elevated intracranial pressure. Ancillary testing, including ultrasonography, fluorescein angiography, fundus autofluorescence, and optical coherence tomography, may aid in the correct diagnosis of optic disc drusen. Complications of optic disc drusen in children include visual field defects, hemorrhages, choroidal neovascular membrane, non-arteritic anterior ischemic optic neuropathy, and retinal vascular occlusions. Treatment options for these complications include ocular hypotensive agents for visual field defects and intravitreal anti-vascular endothelial growth factor (anti-VEGF) agents for choroidal neovascular membranes. In most cases, however, children with optic disc drusen can be managed by observation with serial examinations and visual field testing, once true optic disc edema has been excluded. PMID:27033945

The reports of thick discs' deaths are greatly exaggerated. Thick discs are NOT artefacts caused by diffuse scattered light

NASA Astrophysics Data System (ADS)

Comerón, S.; Salo, H.; Knapen, J. H.

2018-02-01

Recent studies have made the community aware of the importance of accounting for scattered light when examining low-surface-brightness galaxy features such as thick discs. In our past studies of the thick discs of edge-on galaxies in the Spitzer Survey of Stellar Structure in Galaxies - the S4G - we modelled the point spread function as a Gaussian. In this paper we re-examine our results using a revised point spread function model that accounts for extended wings out to more than 2\\farcm5. We study the 3.6 μm images of 141 edge-on galaxies from the S4G and its early-type galaxy extension. Thus, we more than double the samples examined in our past studies. We decompose the surface-brightness profiles of the galaxies perpendicular to their mid-planes assuming that discs are made of two stellar discs in hydrostatic equilibrium. We decompose the axial surface-brightness profiles of galaxies to model the central mass concentration - described by a Sérsic function - and the disc - described by a broken exponential disc seen edge-on. Our improved treatment fully confirms the ubiquitous occurrence of thick discs. The main difference between our current fits and those presented in our previous papers is that now the scattered light from the thin disc dominates the surface brightness at levels below μ 26 mag arcsec-2. We stress that those extended thin disc tails are not physical, but pure scattered light. This change, however, does not drastically affect any of our previously presented results: 1) Thick discs are nearly ubiquitous. They are not an artefact caused by scattered light as has been suggested elsewhere. 2) Thick discs have masses comparable to those of thin discs in low-mass galaxies - with circular velocities vc< 120 km s-1 - whereas they are typically less massive than the thin discs in high-mass galaxies. 3) Thick discs and central mass concentrations seem to have formed at the same epoch from a common material reservoir. 4) Approximately 50% of the up-bending breaks in face-on galaxies are caused by the superposition of a thin and a thick disc where the scale-length of the latter is the largest. Data of Figs. B.1 and C.1 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/610/A5

Physicochemical and biological factors controlling water column metabolism in Sundarbans estuary, India

PubMed Central

2012-01-01

Background Sundarbans is the single largest deltaic mangrove forest in the world, formed at estuarine phase of the Ganges - Brahmaputra river system. Primary productivity of marine and coastal phytoplankton contributes to 15% of global oceanic production. But unfortunately estuarine dynamics of tropical and subtropical estuaries have not yet received proper attention in spite of the fact that they experience considerable anthropogenic interventions and a baseline data is required for any future comparison. This study is an endeavor to this end to estimate the primary productivity (gross and net), community respiration and nitrification rates in different rivers and tidal creeks around Jharkhali island, a part of Sundarbans estuary surrounded by the mangrove forest during a period of three years starting from November’08 to October’11. Results Various physical and chemical parameters of water column like pH, temperature, conductivity, dissolved oxygen, turbidity, suspended particulate matter, secchi disc index, tidal fluctuation and tidal current velocity, standing crop and nutrients were measured along with water column productivity. Relationship of net water column productivity with algal biomass (standing crop), nutrient loading and turbidity were determined experimentally. Correlations of bacterial abundance with community respiration and nitrification rates were also explored. Annual integrated phytoplankton production rate of this tidal estuary was estimated to be 151.07 gC m-2 y-1. Gross primary productivity showed marked inter annual variation being lowest in monsoon and highest in postmonsoon period. Conclusion Average primary production was a function of nutrient loading and light penetration in the water column. High aquatic turbidity, conductivity and suspended particulate matter were the limiting factors to attenuate light penetration with negative influence on primary production. Community respiration and nitrification rates of the estuary were influenced by the bacterial abundance. The estuary was phosphorus limited in postmonsoon whereas nitrogen-limited in premonsoon and monsoon period. High algal biomass and primary productivity indicated the estuary to be in eutrophic state in most of the time throughout the year. Our study also indicated a seasonal shifting between autotrophic and heterotrophic conditions in Sundarban estuarine ecosystem and it is a tropical, well mixed (high tidal influx) and marine dominated (no fresh water connection) system. PMID:23083531

Physicochemical and biological factors controlling water column metabolism in Sundarbans estuary, India.

PubMed

Chaudhuri, Kaberi; Manna, Suman; Sarma, Kakoli Sen; Naskar, Pankaj; Bhattacharyya, Somenath; Bhattacharyya, Maitree

2012-10-19

Sundarbans is the single largest deltaic mangrove forest in the world, formed at estuarine phase of the Ganges - Brahmaputra river system. Primary productivity of marine and coastal phytoplankton contributes to 15% of global oceanic production. But unfortunately estuarine dynamics of tropical and subtropical estuaries have not yet received proper attention in spite of the fact that they experience considerable anthropogenic interventions and a baseline data is required for any future comparison. This study is an endeavor to this end to estimate the primary productivity (gross and net), community respiration and nitrification rates in different rivers and tidal creeks around Jharkhali island, a part of Sundarbans estuary surrounded by the mangrove forest during a period of three years starting from November'08 to October'11. Various physical and chemical parameters of water column like pH, temperature, conductivity, dissolved oxygen, turbidity, suspended particulate matter, secchi disc index, tidal fluctuation and tidal current velocity, standing crop and nutrients were measured along with water column productivity. Relationship of net water column productivity with algal biomass (standing crop), nutrient loading and turbidity were determined experimentally. Correlations of bacterial abundance with community respiration and nitrification rates were also explored. Annual integrated phytoplankton production rate of this tidal estuary was estimated to be 151.07 gC m-2 y-1. Gross primary productivity showed marked inter annual variation being lowest in monsoon and highest in postmonsoon period. Average primary production was a function of nutrient loading and light penetration in the water column. High aquatic turbidity, conductivity and suspended particulate matter were the limiting factors to attenuate light penetration with negative influence on primary production. Community respiration and nitrification rates of the estuary were influenced by the bacterial abundance. The estuary was phosphorus limited in postmonsoon whereas nitrogen-limited in premonsoon and monsoon period. High algal biomass and primary productivity indicated the estuary to be in eutrophic state in most of the time throughout the year. Our study also indicated a seasonal shifting between autotrophic and heterotrophic conditions in Sundarban estuarine ecosystem and it is a tropical, well mixed (high tidal influx) and marine dominated (no fresh water connection) system.

Preparation of ormetoprim-sulfadimethoxine-medicated discs for disc diffusion assay

USDA-ARS?s Scientific Manuscript database

Romet ( a blend of ormetoprim and sulfadimethoxine) is a type A medicated article for the manufacture of medicated feed in the catfish industry. Recently, the commercial manufacture of ormetoprim-sulfadimethoxine susceptibility discs was discontinued. Ormetoprim-sulfadimethoxine discs were prepare...

What's NEW at the GES DISC: Evolution of Data Management and Services for Aura Mission and Beyond

NASA Technical Reports Server (NTRS)

Wei, Jennifer

2016-01-01

GES DISC world. Aura data usage and trend. Aura data users requests. GES DISC update (before/after); New Access method (ftp to http) with Earthdata Login System, New Website (DISC/Mirador to New Interface), New Giovanni (Giovanni to Now Federated). GES DISC support beyond Aura Mission; Multi-sensor coincident data subsets, Level 2 support (Sub-setter, Visualization), Data List.

Non-reclosing pressure relief device for vacuum systems

DOEpatents

Swansiger, William A.

1994-01-01

A non-reclosing overpressure protection device such as a rupture disc provides a non-reclosing opening upon forcible contact with a knife blade. A bellows, having an inlet capable of being sealably connected to a source of pressure (the vacuum system) and an outlet containing the rupture disc, transmits the pressure in the system to the disc. The bellows maintains the disc away from the knife when the pressure is below an overpressure amount, and carries the disc to a position when the pressure is above an overpressure amount where the disc is ruptured by the knife.

Non-reclosing pressure relief device for vacuum systems

DOEpatents

Swansiger, W.A.

1994-02-08

A non-reclosing overpressure protection device such as a rupture disc provides a non-reclosing opening upon forcible contact with a knife blade. A bellows, having an inlet capable of being sealably connected to a source of pressure (the vacuum system) and an outlet containing the rupture disc, transmits the pressure in the system to the disc. The bellows maintains the disc away from the knife when the pressure is below an overpressure amount, and carries the disc to a position when the pressure is above an overpressure amount where the disc is ruptured by the knife. 6 figures.

Developments in intervertebral disc disease research: pathophysiology, mechanobiology, and therapeutics.

PubMed

Weber, Kathryn T; Jacobsen, Timothy D; Maidhof, Robert; Virojanapa, Justin; Overby, Chris; Bloom, Ona; Quraishi, Shaheda; Levine, Mitchell; Chahine, Nadeen O

2015-03-01

Low back pain is a leading cause of disability worldwide and the second most common cause of physician visits. There are many causes of back pain, and among them, disc herniation and intervertebral disc degeneration are the most common diagnoses and targets for intervention. Currently, clinical treatment outcomes are not strongly correlated with diagnoses, emphasizing the importance for characterizing more completely the mechanisms of degeneration and their relationships with symptoms. This review covers recent studies elucidating cellular and molecular changes associated with disc mechanobiology, as it relates to degeneration and regeneration. Specifically, we review findings on the biochemical changes in disc diseases, including cytokines, chemokines, and proteases; advancements in disc disease diagnostics using imaging modalities; updates on studies examining the response of the intervertebral disc to injury; and recent developments in repair strategies, including cell-based repair, biomaterials, and tissue engineering. Findings on the effects of the omega-6 fatty acid, linoleic acid, on nucleus pulposus tissue engineering are presented. Studies described in this review provide greater insights into the pathogenesis of disc degeneration and may define new paradigms for early or differential diagnostics of degeneration using new techniques such as systemic biomarkers. In addition, research on the mechanobiology of disease enriches the development of therapeutics for disc repair, with potential to diminish pain and disability associated with disc degeneration.

MECHANICAL DESIGN CRITERIA FOR INTERVERTEBRAL DISC TISSUE ENGINEERING

PubMed Central

Nerurkar, Nandan L.; Elliott, Dawn M.; Mauck, Robert L.

2009-01-01

Due to the inability of current clinical practices to restore function to degenerated intervertebral discs, the arena of disc tissue engineering has received substantial attention in recent years. Despite tremendous growth and progress in this field, translation to clinical implementation has been hindered by a lack of well-defined functional benchmarks. Because successful replacement of the disc is contingent upon replication of some or all of its complex mechanical behaviour, it is critically important that disc mechanics be well characterized in order to establish discrete functional goals for tissue engineering. In this review, the key functional signatures of the intervertebral disc are discussed and used to propose a series of native tissue benchmarks to guide the development of engineered replacement tissues. These benchmarks include measures of mechanical function under tensile, compressive and shear deformations for the disc and its substructures. In some cases, important functional measures are identified that have yet to be measured in the native tissue. Ultimately, native tissue benchmark values are compared to measurements that have been made on engineered disc tissues, identifying measures where functional equivalence was achieved, and others where there remain opportunities for advancement. Several excellent reviews exist regarding disc composition and structure, as well as recent tissue engineering strategies; therefore this review will remain focused on the functional aspects of disc tissue engineering. PMID:20080239

On fragmentation of turbulent self-gravitating discs in the long cooling time regime

NASA Astrophysics Data System (ADS)

Rice, Ken; Nayakshin, Sergei

2018-03-01

It has recently been suggested that in the presence of driven turbulence discs may be much less stable against gravitational collapse than their non-turbulent analogues, due to stochastic density fluctuations in turbulent flows. This mode of fragmentation would be especially important for gas giant planet formation. Here, we argue, however, that stochastic density fluctuations due to turbulence do not enhance gravitational instability and disc fragmentation in the long cooling time limit appropriate for planet forming discs. These fluctuations evolve adiabatically and dissipate away by decompression faster than they could collapse. We investigate these issues numerically in two dimensions via shearing box simulations with driven turbulence and also in three dimensions with a model of instantaneously applied turbulent velocity kicks. In the former setting turbulent driving leads to additional disc heating that tends to make discs more, rather than less, stable to gravitational instability. In the latter setting, the formation of high-density regions due to convergent velocity kicks is found to be quickly followed by decompression, as expected. We therefore conclude that driven turbulence does not promote disc fragmentation in protoplanetary discs and instead tends to make the discs more stable. We also argue that sustaining supersonic turbulence is very difficult in discs that cool slowly.

Metallicity gradient of the thick disc progenitor at high redshift

NASA Astrophysics Data System (ADS)

Kawata, Daisuke; Allende Prieto, Carlos; Brook, Chris B.; Casagrande, Luca; Ciucă, Ioana; Gibson, Brad K.; Grand, Robert J. J.; Hayden, Michael R.; Hunt, Jason A. S.

2018-01-01

We have developed a novel Markov Chain Monte Carlo chemical 'painting' technique to explore possible radial and vertical metallicity gradients for the thick disc progenitor. In our analysis, we match an N-body simulation to the data from the Apache Point Observatory Galactic Evolution Experiment survey. We assume that the thick disc has a constant scaleheight and has completed its formation at an early epoch, after which time radial mixing of its stars has taken place. Under these assumptions, we find that the initial radial metallicity gradient of the thick disc progenitor should not be negative, but either flat or even positive, to explain the current negative vertical metallicity gradient of the thick disc. Our study suggests that the thick disc was built-up in an inside-out and upside-down fashion, and older, smaller and thicker populations are more metal poor. In this case, star-forming discs at different epochs of the thick disc formation are allowed to have different radial metallicity gradients, including a negative one, which helps to explain a variety of slopes observed in high-redshift disc galaxies. This scenario helps to explain the positive slope of the metallicity-rotation velocity relation observed for the Galactic thick disc. On the other hand, radial mixing flattens the slope of an existing gradient.

Physical and Chemical Limnology of the Abegondo-Cecebre reservoir, A Coruña, NW Spain

NASA Astrophysics Data System (ADS)

Delgado, Jordi; Cereijo-Arango, José Luis; García-Morrondo, David; Cillero-Castro, Carmen; Muñoz-Ibáñez, Andrea; Juncosa-Rivera, Ricardo

2016-04-01

The Abegondo-Cecebre reservoir was commissioned in 1976. It has a nominal capacity of ~23 hm3 and an actual regulation capacity of 20.6 hm3 (12.9 hm3 in rainy periods, when flood control is necessary). This reservoir constitutes the only source of drinking water for the city of A Coruña and its metropolitan area (~400.000 inhabitants). The reservoir, which is two-tailed, is located downstream the Barcés and Mero rivers (~250 km2) and belongs to the so-called Galician-Coast River Basin district (16,372 km2). The increasing water demand for human consumption and industrial purposes challenges the supply capacity of the system and this is especially acute when, in hydric-stress situations, the availability of water becomes reduced and the water quality is adversely affected by a number of hypolimnetic processes (anoxia, increased metal concentration, etc.) or by episodic algal blooms. Between May 2010 and May 2012, within the context of the LIFE07 ENV/E/000826 Aqua Plann Project, an in-depth study was commissioned by the local water supply managers (EMALCSA). The study encompassed a bathymetry and colmatation characterization as well as a systematic physico-chemical survey via monthly sampling and measurement in selected stations a series of relevant limnological parameters. Surface and bottom reservoir water was sampled in seven representative locations of the system while three of them were used for depth profiling. In addition, five stations were considered for collecting the top layer of the sediments of the reservoir (~20 cm) in two surveys developed in the spring and summer of 2012. The parameters determined, complemented with meteorological information and discharge flows, included temperature, Secchi's depth transparency, PAR radiation, pH, electrical conductivity, redox, dissolved oxygen, turbidity, alkalinity, chlorophyll, phycocyanin, Na, K, Ca, Mg, F, Cl, SO4, NH4, NO3, NO2, PO4, DIC, DOC, particulated organic carbon, Fe, Mn, Al, As, Ba, Be, B, Cd, Co, Cr, Cu, Hg, Ni, Pb, Se, Zn, total P and N, BOD5, 27 plaguicides, 8 HPAs, 23 COVs, 18 PCBs, phenols, detergents, and a 4 indicators of microbial water quality. Based on the previous studies, some relevant morphometric parameters are the following: maximum length: 3627 m; maximum width: 1525 m; maximum depth: 17.2 m; mean depth: 5.9 m; catchment to lake ratio: 64. Based on the bathymetric survey, the reservoir volume lost by sedimentation in its 35 years is about 9.3%. The Abegondo-Cecebre reservoir presents a mesotrophic-eutrophic state. Thermal stratification starts in March and an annual overturn occur in November (monomictic system). Hypolimnetic oxygen depletion is nearly complete (i.e. anoxia) from the beginning of June to mid-end October. Along this period, a number of redox reactions take place in the bottom waters that tend to increase metal and NH4 concentrations, reduce NO3 (and partly SO4) and release P from the sediments.

An unbiased study of debris discs around A-type stars with Herschel

NASA Astrophysics Data System (ADS)

Thureau, N. D.; Greaves, J. S.; Matthews, B. C.; Kennedy, G.; Phillips, N.; Booth, M.; Duchêne, G.; Horner, J.; Rodriguez, D. R.; Sibthorpe, B.; Wyatt, M. C.

2014-12-01

The Herschel DEBRIS (Disc Emission via a Bias-free Reconnaissance in the Infrared/Submillimetre) survey brings us a unique perspective on the study of debris discs around main-sequence A-type stars. Bias-free by design, the survey offers a remarkable data set with which to investigate the cold disc properties. The statistical analysis of the 100 and 160 μm data for 86 main-sequence A stars yields a lower than previously found debris disc rate. Considering better than 3σ excess sources, we find a detection rate ≥24 ± 5 per cent at 100 μm which is similar to the debris disc rate around main-sequence F/G/K-spectral type stars. While the 100 and 160 μm excesses slowly decline with time, debris discs with large excesses are found around some of the oldest A stars in our sample, evidence that the debris phenomenon can survive throughout the length of the main sequence (˜1 Gyr). Debris discs are predominantly detected around the youngest and hottest stars in our sample. Stellar properties such as metallicity are found to have no effect on the debris disc incidence. Debris discs are found around A stars in single systems and multiple systems at similar rates. While tight and wide binaries (<1 and >100 au, respectively) host debris discs with a similar frequency and global properties, no intermediate separation debris systems were detected in our sample.

The evolution of photoevaporating viscous discs in binaries

NASA Astrophysics Data System (ADS)

Rosotti, Giovanni P.; Clarke, Cathie J.

2018-02-01

A large fraction of stars are in binary systems, yet the evolution of protoplanetary discs in binaries has been little explored from the theoretical side. In this paper, we investigate the evolution of the discs surrounding the primary and secondary components of binary systems on the assumption that this is driven by photoevaporation induced by X-rays from the respective star. We show how for close enough separations (20-30 au for average X-ray luminosities) the tidal torque of the companion changes the qualitative behaviour of disc dispersal from inside out to outside in. Fewer transition discs created by photoevaporation are thus expected in binaries. We also demonstrate that in close binaries the reduction in viscous time leads to accelerated disc clearing around both components, consistent with unresolved observations. When looking at the differential disc evolution around the two components, in close binaries discs around the secondary clear first due to the shorter viscous time-scale associated with the smaller outer radius. In wide binaries instead the difference in photoevaporation rate makes the secondaries longer lived, though this is somewhat dependent on the assumed scaling of viscosity with stellar mass. We find that our models are broadly compatible with the growing sample of resolved observations of discs in binaries. We also predict that binaries have higher accretion rates than single stars for the same disc mass. Thus, binaries probably contribute to the observed scatter in the relationship between disc mass and accretion rate in young stars.

Self-gravity in thin discs and edge effects: an extension of Paczynski's approximation

NASA Astrophysics Data System (ADS)

Trova, Audrey; Huré, Jean-Marc; Hersant, Franck

2014-03-01

Because hydrostatic equilibrium of gaseous discs is partly governed by the gravity field, we have estimated the component caused by a vertically homogeneous disc with particular attention to the outer regions where self-gravity appears most often. The accuracy of the integral formula is better than 1% regardless of the disc thickness, radial extension and radial density profile. At order zero, the field is even algebraic for thin discs and reads -4πGΣ(R) × fedges(R) at disc surface, which means a correction of Paczynski's formula by a multiplying factor fedges ≲ ½, which depends on the relative distance to the edges and the local disc thickness. For very centrally condensed discs, however, this local contribution can be surpassed by the action of mass stored in the inner regions, possibly resulting in fedges ≫ 1. A criterion setting the limit between these two regimes is derived. These results are robust in the sense that the details of vertical stratification are not critical. We briefly discuss how hydrostatic equilibrium is affected. In particular, the disc flaring probably does not reverse in the self-gravitating region, which contradicts what is usually obtained from Paczynski's formula. This suggests that i) these outer regions are probably not fully shadowed by the inner ones (when the disc is illuminated by a central star); and ii) the flared shape of discs does not firmly prove the absence or weakness of self-gravity.

Lessons from the Auriga discs: the hunt for the Milky Way's ex situ disc is not yet over

NASA Astrophysics Data System (ADS)

Gómez, Facundo A.; Grand, Robert J. J.; Monachesi, Antonela; White, Simon D. M.; Bustamante, Sebastian; Marinacci, Federico; Pakmor, Rüdiger; Simpson, Christine M.; Springel, Volker; Frenk, Carlos S.

2017-12-01

We characterize the contribution from accreted material to the galactic discs of the Auriga Project, a set of high-resolution magnetohydrodynamic cosmological simulations of late-type galaxies performed with the moving-mesh code AREPO. Our goal is to explore whether a significant accreted (or ex situ) stellar component in the Milky Way disc could be hidden within the near-circular orbit population, which is strongly dominated by stars born in situ. One-third of our models shows a significant ex situ disc but this fraction would be larger if constraints on orbital circularity were relaxed. Most of the ex situ material (≳50 per cent) comes from single massive satellites (>6 × 1010 M⊙). These satellites are accreted with a wide range of infall times and inclination angles (up to 85°). Ex situ discs are thicker, older and more metal poor than their in situ counterparts. They show a flat median age profile, which differs from the negative gradient observed in the in situ component. As a result, the likelihood of identifying an ex situ disc in samples of old stars on near-circular orbits increases towards the outskirts of the disc. We show three examples that, in addition to ex situ discs, have a strongly rotating dark matter component. Interestingly, two of these ex situ stellar discs show an orbital circularity distribution that is consistent with that of the in situ disc. Thus, they would not be detected in typical kinematic studies.

Human disc degeneration is associated with increased MMP 7 expression.

PubMed

Le Maitre, C L; Freemont, A J; Hoyland, J A

2006-01-01

During intervertebral disc (IVD) degeneration, normal matrix synthesis decreases and degradation of disc matrix increases. A number of proteases that are increased during disc degeneration are thought to be involved in its pathogenesis. Matrix metalloproteinase 7 (MMP 7) (Matrilysin, PUMP-1) is known to cleave the major matrix molecules found within the IVD, i.e., the proteoglycan aggrecan and collagen type II. To date, however, it is not known how its expression changes with degeneration or its exact location. We investigated the localization of MMP 7 in human, histologically graded, nondegenerate, degenerated and prolapsed discs to ascertain whether MMP 7 is up-regulated during disc degeneration. Samples of human IVD tissue were fixed in neutral buffered formalin, embedded in paraffin, and sections stained with hematoxylin and eosin to score the degree of morphological degeneration. Immunohistochemistry was performed to localize MMP 7 in 41 human IVDs with varying degrees of degeneration. We found that the chondrocyte-like cells of the nucleus pulposus and inner annulus fibrosus were MMP 7 immunopositive; little immunopositivity was observed in the outer annulus. Nondegenerate discs showed few immunopositive cells. A significant increase in the proportion of MMP 7 immunopositive cells was seen in the nucleus pulposus of discs classified as showing intermediate levels of degeneration and a further increase was seen in discs with severe degeneration. Prolapsed discs showed more MMP 7 immunopositive cells compared to nondegenerated discs, but fewer than those seen in cases of severe degeneration.

Observations of warm molecular gas and kinematics in the disc around HD 100546

NASA Astrophysics Data System (ADS)

Panić, O.; van Dishoeck, E. F.; Hogerheijde, M. R.; Belloche, A.; Güsten, R.; Boland, W.; Baryshev, A.

2010-09-01

Context. The disc around the Herbig Ae/Be star HD 100546 is one of the most extensively studied discs in the southern sky. Although there is a wealth of information about its dust content and composition, not much is known about its gas and large-scale kinematics. Many recent results have stressed the importance of studying both the gas and dust in discs. 12CO is an excellent gas tracer in the submillimetre, and the intensity ratio between lines originating from low and high rotational levels probes the gas temperature. Emerging submillimetre facilities in the Southern hemisphere allow us to characterise the gas and dust content in objects like HD 100546 better. Aims: Our aim is to establish whether the disc is gas-rich and to study the disc temperature and kinematics. Methods: We detected and studied the molecular gas in the disc at spatial resolution from 7.7 arcsec to 18.9 arcsec using the Atacama Pathfinder Experiment telescope (This publication is based on data acquired with the Atacama Pathfinder Experiment (APEX). APEX is a collaboration between the Max-Planck-Institut für Radioastronomie, the European Southern Observatory, and the Onsala Space Observatory.). We observed the lines 12CO J = 7-6, J = 6-5, J = 3-2, 13CO J = 3-2 and [C I] 3P2-3P1, as diagnostics of disc temperature, size, chemistry, and kinematics. We use parametric disc models that reproduce the low-J 12CO emission from Herbig Ae stars and we vary the basic disc parameters - temperature, mass, and size. With the help of a molecular excitation and radiative transfer code we fit the observed spectral line profiles. Results: Our observations are consistent with more than 10-3 M⊙ of molecular gas in a disc of ≈400 AU radius in Keplerian rotation around a 2.5 M⊙ star, seen at an inclination of 50°. The detected 12CO lines are dominated by gas at 30-70 K. Not detecting the [C I] line indicates excess ultraviolet emission above that of a B9 type model stellar atmosphere. Asymmetry in the 12CO line emission suggests that one side of the outer disc is colder by 10-20 K than the other. A plausible scenario is a warped geometry in the inner disc casting a partial shaddow on the outer disc. We exclude pointing offsets, foreground cloud absorption, and asymmetry in the disc extent as possible causes of the observed line asymmetry. Conclusions: Efficient heating of the outer disc by the star HD 100546 ensures that low- and high-J 12CO lines are dominated by the outermost disc regions, indicating a 400 AU radius. The 12CO J = 6-5 line arises from a disc layer higher than disc midplane, and warmer by 15-20 K than the layer emitting the J = 3-2 line. The existing models of discs around Herbig Ae stars, asuming a B9.5 type model stellar atmosphere, overproduce the [CI] 3P2-3P1 line intensity from HD 100546 by an order of magnitude.

Preparation of ormetoprim sulfadimethoxine medicated discs for disc diffusion assay

USDA-ARS?s Scientific Manuscript database

Romet (a blend of ormetoprim and sulfadimethoxine) is a typeA medicated article for the manufacture of medicated feed in the catfish industry. Recently, the commercial manufacture of ormetoprim–sulfadimethoxine susceptibility discs was discontinued. Ormetoprim–sulfadimethoxine discs were prepared at...

Limnology of Sawtooth Valley Lakes in 1995

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luecke, C.; Slater, M.; Budy, P.

1996-05-01

Included in this section of the report on limnology of Lakes in the Snake River Plain are descriptions of the limnological characteristics of the four lakes in reference to their potential effect of growth and survival of juvenile sockeye salmon. Physical parameters included light penetration, Secchi transparency, and water temperature; chemical parameters included oxygen, and both dissolved and particulate forms of nitrogen and phosphorus. Phytoplankton parameters included chlorophyll concentration, biovolume of dominant taxa, and rates of primary production; zooplankton parameters included density and biomass estimate, length frequencies, and the number of eggs carried by female cladocerans. 11 figs., 5 tabs.

Biomaterials for intervertebral disc regeneration and repair.

PubMed

Bowles, Robert D; Setton, Lori A

2017-06-01

The intervertebral disc contributes to motion, weight bearing, and flexibility of the spine, but is susceptible to damage and morphological changes that contribute to pathology with age and injury. Engineering strategies that rely upon synthetic materials or composite implants that do not interface with the biological components of the disc have not met with widespread use or desirable outcomes in the treatment of intervertebral disc pathology. Here we review bioengineering advances to treat disc disorders, using cell-supplemented materials, or acellular, biologically based materials, that provide opportunity for cell-material interactions and remodeling in the treatment of intervertebral disc disorders. While a field still in early development, bioengineering-based strategies employing novel biomaterials are emerging as promising alternatives for clinical treatment of intervertebral disc disorders. Copyright © 2017 Elsevier Ltd. All rights reserved.

Anomalous optic discs in a patient with a Dandy-Walker cyst.

PubMed

Orcutt, J C; Bunt, A H

1982-03-01

A 19-month-old female infant with a Dandy-Walker cyst had anomalous optic discs, each of which appeared to divide to form an accessory optic nerve. The discs probably lie within the spectrum of anomalous discs including optic nerve aplasia and hypoplasia, megallopapillae, morning glory disc, optic disc dysplasia, and optic nerve colobomas. The association of anomalous optic discs with a Dandy-Walker cyst has not been previously recognized. The ocular and brain malformations in this patient likely occurred during the fourth to eighth week of gestation, when the retinal ganglion cell axons were penetrating the optic nerve, and the rhombic lips were enlarging in early cerebellar development. The etiology of these anomalies is not known; however, teratogens, sporadic events, and genetic disorders should be considered.

Enclosed rotary disc air pulser

DOEpatents

Olson, A. L.; Batcheller, Tom A.; Rindfleisch, J. A.; Morgan, John M.

1989-01-01

An enclosed rotary disc air pulser for use with a solvent extraction pulse olumn includes a housing having inlet, exhaust and pulse leg ports, a shaft mounted in the housing and adapted for axial rotation therein, first and second disc members secured to the shaft within the housing in spaced relation to each other to define a chamber therebetween, the chamber being in communication with the pulse leg port, the first disc member located adjacent the inlet port, the second disc member being located adjacent the exhaust port, each disc member having a milled out portion, the disc members positioned on the shaft so that as the shaft rotates, the milled out portions permit alternative cyclical communication between the inlet port and the chamber and the exhaust port and the chamber.

Circumstellar disc lifetimes in numerous galactic young stellar clusters

NASA Astrophysics Data System (ADS)

Richert, A. J. W.; Getman, K. V.; Feigelson, E. D.; Kuhn, M. A.; Broos, P. S.; Povich, M. S.; Bate, M. R.; Garmire, G. P.

2018-07-01

Photometric detections of dust circumstellar discs around pre-main sequence (PMS) stars, coupled with estimates of stellar ages, provide constraints on the time available for planet formation. Most previous studies on disc longevity, starting with Haisch, Lada & Lada, use star samples from PMS clusters but do not consider data sets with homogeneous photometric sensitivities and/or ages placed on a uniform time-scale. Here we conduct the largest study to date of the longevity of inner dust discs using X-ray and 1-8 µm infrared photometry from the MYStIX and SFiNCs projects for 69 young clusters in 32 nearby star-forming regions with ages t ≤ 5 Myr. Cluster ages are derived by combining the empirical AgeJX method with PMS evolutionary models, which treat dynamo-generated magnetic fields in different ways. Leveraging X-ray data to identify disc-free objects, we impose similar stellar mass sensitivity limits for disc-bearing and disc-free young stellar objects while extending the analysis to stellar masses as low as M ˜ 0.1 M⊙. We find that the disc longevity estimates are strongly affected by the choice of PMS evolutionary model. Assuming a disc fraction of 100 per cent at zero age, the inferred disc half-life changes significantly, from t1/2 ˜ 1.3-2 Myr to t1/2 ˜ 3.5 Myr when switching from non-magnetic to magnetic PMS models. In addition, we find no statistically significant evidence that disc fraction varies with stellar mass within the first few Myr of life for stars with masses <2 M⊙, but our samples may not be complete for more massive stars. The effects of initial disc fraction and star-forming environment are also explored.

Evidence for the concurrent growth of thick discs and central mass concentrations from S4G imaging

NASA Astrophysics Data System (ADS)

Comerón, S.; Elmegreen, B. G.; Salo, H.; Laurikainen, E.; Holwerda, B. W.; Knapen, J. H.

2014-11-01

We have produced 3.6 μm + 4.5 μm vertically integrated radial luminosity profiles of 69 edge-on galaxies from the Spitzer Survey of Stellar Structure in Galaxies (S4G). We decomposed the luminosity profiles into a disc and a central mass concentration (CMC). These fits, combined with thin/thick disc decompositions from our previous studies, allow us to estimate the masses of the CMCs, the thick discs, and the thin discs (ℳCMC, ℳT, and ℳT). We obtained atomic disc masses (ℳg) from the literature. We then consider the CMC and the thick disc to be dynamically hot components and the thin disc and the gas disc to be dynamically cold components. We find that the ratio between the mass of the hot components and that of the cold components, (ℳCMC + ℳT)/(ℳt + ℳg), does not depend on the total galaxy mass as described by circular velocities (vc). We also find that the higher the vc, the more concentrated the hot component of a galaxy. We suggest that our results are compatible with having CMCs and thick discs built in a short and early high star forming intensity phase. These components were born thick because of the large scale height of the turbulent gas disc in which they originated. Our results indicate that the ratio between the star forming rate in the former phase and that of the formation of the thin disc is of the order of 10, but the value depends on the duration of the high star forming intensity phase. Appendix A is available in electronic form at http://www.aanda.org

Expression of DISC1-interactome members correlates with cognitive phenotypes related to schizophrenia.

PubMed

Rampino, Antonio; Walker, Rosie May; Torrance, Helen Scott; Anderson, Susan Maguire; Fazio, Leonardo; Di Giorgio, Annabella; Taurisano, Paolo; Gelao, Barbara; Romano, Raffaella; Masellis, Rita; Ursini, Gianluca; Caforio, Grazia; Blasi, Giuseppe; Millar, J Kirsty; Porteous, David John; Thomson, Pippa Ann; Bertolino, Alessandro; Evans, Kathryn Louise

2014-01-01

Cognitive dysfunction is central to the schizophrenia phenotype. Genetic and functional studies have implicated Disrupted-in-Schizophrenia 1 (DISC1), a leading candidate gene for schizophrenia and related psychiatric conditions, in cognitive function. Altered expression of DISC1 and DISC1-interactors has been identified in schizophrenia. Dysregulated expression of DISC1-interactome genes might, therefore, contribute to schizophrenia susceptibility via disruption of molecular systems required for normal cognitive function. Here, the blood RNA expression levels of DISC1 and DISC1-interacting proteins were measured in 63 control subjects. Cognitive function was assessed using neuropsychiatric tests and functional magnetic resonance imaging was used to assess the activity of prefrontal cortical regions during the N-back working memory task, which is abnormal in schizophrenia. Pairwise correlations between gene expression levels and the relationship between gene expression levels and cognitive function and N-back-elicited brain activity were assessed. Finally, the expression levels of DISC1, AKAP9, FEZ1, NDEL1 and PCM1 were compared between 63 controls and 69 schizophrenic subjects. We found that DISC1-interactome genes showed correlated expression in the blood of healthy individuals. The expression levels of several interactome members were correlated with cognitive performance and N-back-elicited activity in the prefrontal cortex. In addition, DISC1 and NDEL1 showed decreased expression in schizophrenic subjects compared to healthy controls. Our findings highlight the importance of the coordinated expression of DISC1-interactome genes for normal cognitive function and suggest that dysregulated DISC1 and NDEL1 expression might, in part, contribute to susceptibility for schizophrenia via disruption of prefrontal cortex-dependent cognitive functions.

Expression of DISC1-Interactome Members Correlates with Cognitive Phenotypes Related to Schizophrenia

PubMed Central

Rampino, Antonio; Walker, Rosie May; Torrance, Helen Scott; Anderson, Susan Maguire; Fazio, Leonardo; Di Giorgio, Annabella; Taurisano, Paolo; Gelao, Barbara; Romano, Raffaella; Masellis, Rita; Ursini, Gianluca; Caforio, Grazia; Blasi, Giuseppe; Millar, J. Kirsty; Porteous, David John; Thomson, Pippa Ann; Bertolino, Alessandro; Evans, Kathryn Louise

2014-01-01

Cognitive dysfunction is central to the schizophrenia phenotype. Genetic and functional studies have implicated Disrupted-in-Schizophrenia 1 (DISC1), a leading candidate gene for schizophrenia and related psychiatric conditions, in cognitive function. Altered expression of DISC1 and DISC1-interactors has been identified in schizophrenia. Dysregulated expression of DISC1-interactome genes might, therefore, contribute to schizophrenia susceptibility via disruption of molecular systems required for normal cognitive function. Here, the blood RNA expression levels of DISC1 and DISC1-interacting proteins were measured in 63 control subjects. Cognitive function was assessed using neuropsychiatric tests and functional magnetic resonance imaging was used to assess the activity of prefrontal cortical regions during the N-back working memory task, which is abnormal in schizophrenia. Pairwise correlations between gene expression levels and the relationship between gene expression levels and cognitive function and N-back-elicited brain activity were assessed. Finally, the expression levels of DISC1, AKAP9, FEZ1, NDEL1 and PCM1 were compared between 63 controls and 69 schizophrenic subjects. We found that DISC1-interactome genes showed correlated expression in the blood of healthy individuals. The expression levels of several interactome members were correlated with cognitive performance and N-back-elicited activity in the prefrontal cortex. In addition, DISC1 and NDEL1 showed decreased expression in schizophrenic subjects compared to healthy controls. Our findings highlight the importance of the coordinated expression of DISC1-interactome genes for normal cognitive function and suggest that dysregulated DISC1 and NDEL1 expression might, in part, contribute to susceptibility for schizophrenia via disruption of prefrontal cortex-dependent cognitive functions. PMID:24940743

Modelling and observations of molecules in discs around young stars

NASA Astrophysics Data System (ADS)

Ilee, John David

2013-04-01

This thesis contains a study of molecules within circumstellar discs around young stars. Firstly, the chemistry of a disc around a young, Class 0 protostar is modelled. Such discs are thought to be massive, and thus experience gravitational instabilities, which produce spiral density waves. These affect the chemistry in three ways; by desorbing molecules from dust grains, by providing extra energy for new reactions to take place, and by mixing the internal structure of the disc to provide a rich chemistry near the midplane. Secondly, high resolution near-infrared spectra of 20 massive young stellar objects are presented. The objects display CO first overtone bandhead emission, which is excited in the conditions expected within circumstellar discs. The emission is modelled using a simple analytic model of a Keplerian disc, and good fits are found to all spectra. On average, the discs correspond to being geometrically thin, spread across a wide range of inclinations. The discs are located within the dust sublimation radius, providing strong evidence that the CO emission originates in small gaseous discs, supporting the scenario in which massive stars form via disc accretion. Finally, medium resolution near-infrared spectra of 5 Herbig Ae/Be stars are presented. The spectra cover both CO bandhead and Br gamma emission. Accretion rates are derived from the measuring the Br gamma emission and through modelling the CO emission, however these accretion rates are found to be inconsistent. High resolution archival data of one of the targets is presented, and it is shown that this CO disc model is unable to fit the high resolution data. Therefore, it is concluded that to properly fit CO spectra, high resolution data are needed, and that previously published information determined from low resolution spectra should be treated with caution.

A Large Animal Model that Recapitulates the Spectrum of Human Intervertebral Disc Degeneration

PubMed Central

Gullbrand, Sarah E.; Malhotra, Neil R.; Schaer, Thomas P.; Zawacki, Zosia; Martin, John T.; Bendigo, Justin R.; Milby, Andrew H.; Dodge, George R.; Vresilovic, Edward J.; Elliott, Dawn M.; Mauck, Robert L.; Smith, Lachlan J.

2016-01-01

Objective The objective of this study was to establish a large animal model that recapitulates the spectrum of intervertebral disc degeneration that occurs in humans and which is suitable for pre-clinical evaluation of a wide range of experimental therapeutics. Design Degeneration was induced in the lumbar intervertebral discs of large frame goats by either intradiscal injection of chondroitinase ABC (ChABC) over a range of dosages (0.1U, 1U or 5U) or subtotal nucleotomy. Radiographs were used to assess disc height changes over 12 weeks. Degenerative changes to the discs and endplates were assessed via magnetic resonance imaging (MRI), semi-quantitative histological grading, micro-computed tomography (µCT), and measurement of disc biomechanical properties. Results Degenerative changes were observed for all interventions that ranged from mild (0.1U ChABC) to moderate (1U ChABC and nucleotomy) to severe (5U ChABC). All groups showed progressive reductions in disc height over 12 weeks. Histological scores were significantly increased in the 1U and 5U ChABC groups. Reductions in T2 and T1ρ, and increased Pfirrmann grade were observed on MRI. Resorption and remodeling of the cortical boney endplate adjacent to ChABC injected discs also occurred. Spine segment range of motion was greater and compressive modulus was lower in 1U ChABC and nucleotomy discs compared to intact. Conclusions A large animal model of disc degeneration was established that recapitulates the spectrum of structural, compositional and biomechanical features of human disc degeneration. This model may serve as a robust platform for evaluating the efficacy of therapeutics targeted towards varying degrees of disc degeneration. PMID:27568573

Global variation of the dust-to-gas ratio in evolving protoplanetary discs

NASA Astrophysics Data System (ADS)

Hughes, Anna L. H.; Armitage, Philip J.

2012-06-01

Recent theories suggest planetesimal formation via streaming and/or gravitational instabilities may be triggered by localized enhancements in the dust-to-gas ratio, and one hypothesis is that sufficient enhancements may be produced in the pile-up of small solid particles inspiralling under aerodynamic drag from the large mass reservoir in the outer disc. Studies of particle pile-up in static gas discs have provided partial support for this hypothesis. Here, we study the radial and temporal evolution of the dust-to-gas ratio in turbulent discs that evolve under the action of viscosity and photoevaporation. We find that particle pile-ups do not generically occur within evolving discs, particularly if the introduction of large grains is restricted to the inner, dense regions of a disc. Instead, radial drift results in depletion of solids from the outer disc, while the inner disc maintains a dust-to-gas ratio that is within a factor of ˜2 of the initial value. We attribute this result to the short time-scales for turbulent diffusion and radial advection (with the mean gas flow) in the inner disc. We show that the qualitative evolution of the dust-to-gas ratio depends only weakly upon the parameters of the disc model (the disc mass, size, viscosity and value of the Schmidt number), and discuss the implications for planetesimal formation via collective instabilities. Our results suggest that in discs where there is a significant level of midplane turbulence and accretion, planetesimal formation would need to be possible in the absence of large-scale enhancements. Instead, trapping and concentration of particles within local turbulent structures may be required as a first stage of planetesimal formation.

Gravitational instabilities in a protosolar-like disc - I. Dynamics and chemistry

NASA Astrophysics Data System (ADS)

Evans, M. G.; Ilee, J. D.; Boley, A. C.; Caselli, P.; Durisen, R. H.; Hartquist, T. W.; Rawlings, J. M. C.

2015-10-01

To date, most simulations of the chemistry in protoplanetary discs have used 1 + 1D or 2D axisymmetric α-disc models to determine chemical compositions within young systems. This assumption is inappropriate for non-axisymmetric, gravitationally unstable discs, which may be a significant stage in early protoplanetary disc evolution. Using 3D radiative hydrodynamics, we have modelled the physical and chemical evolution of a 0.17 M⊙ self-gravitating disc over a period of 2000 yr. The 0.8 M⊙ central protostar is likely to evolve into a solar-like star, and hence this Class 0 or early Class I young stellar object may be analogous to our early Solar system. Shocks driven by gravitational instabilities enhance the desorption rates, which dominate the changes in gas-phase fractional abundances for most species. We find that at the end of the simulation, a number of species distinctly trace the spiral structure of our relatively low-mass disc, particularly CN. We compare our simulation to that of a more massive disc, and conclude that mass differences between gravitationally unstable discs may not have a strong impact on the chemical composition. We find that over the duration of our simulation, successive shock heating has a permanent effect on the abundances of HNO, CN and NH3, which may have significant implications for both simulations and observations. We also find that HCO+ may be a useful tracer of disc mass. We conclude that gravitational instabilities induced in lower mass discs can significantly, and permanently, affect the chemical evolution, and that observations with high-resolution instruments such as Atacama Large Millimeter/submillimeter Array (ALMA) offer a promising means of characterizing gravitational instabilities in protosolar discs.

In vivo dynamic stiffness of the porcine lumbar spine exposed to cyclic loading: influence of load and degeneration.

PubMed

Kaigle, A; Ekström, L; Holm, S; Rostedt, M; Hansson, T

1998-02-01

The dynamic axial stiffness of the L2-3 motion segment subjected to vibratory loading under intact and injured states of the intervertebral disc was studied using an in vivo porcine model. Three groups of animals with the following states of the intervertebral discs were studied: intact disc, acutely injured disc, and degenerated disc. A miniaturized servo-hydraulic exciter was used to sinusoidally vibrate the motion segment from 0.05 to 25 Hz under a compressive load with a peak value of either 100 or 200 N. The dynamic axial stiffness of the intervertebral disc was calculated at 1-Hz intervals over the frequency range. The results showed that the dynamic axial stiffness was frequency dependent. A positive relationship was found between an increase in mean dynamic stiffness and load magnitude. An increase in mean stiffness with successive exposures at the same load magnitude was observed, despite the allowance of a recovery period between loading. The greatest difference was noted between the first and second load sets. No significant change in stiffness was found due to an acute disc injury, whereas a significant increase in mean stiffness was found for the degenerated disc group as compared with the intact group. The form of the frequency response curve, however, remained relatively unaltered regardless of the degenerated state of the disc. With heavier loads, repeated loading, and/or disc degeneration, the stiffness of the intervertebral disc increases. An increase in stiffness can mean a reduction in the amount of allowable motion within the motion segment or a potentially harmful increase in force to obtain the desired motion. This may locally result in greater stresses due to an altered ability of the disc to distribute loads.

A RCT comparing 7-year clinical outcomes of one level symptomatic cervical disc disease (SCDD) following ProDisc-C total disc arthroplasty (TDA) versus anterior cervical discectomy and fusion (ACDF).

PubMed

Loumeau, Thomas P; Darden, Bruce V; Kesman, Thomas J; Odum, Susan M; Van Doren, Bryce A; Laxer, Eric B; Murrey, Daniel B

2016-07-01

The objective of this trial was to compare the safety and efficacy of TDA using the ProDisc-C implant to ACDF in patients with single-level SCDD between C3 and C7. We report on the single-site results from a larger multicenter trial of 13 sites using an approved US Food and Drug Administration protocol (prospective, randomized controlled non-inferiority design). Patients were randomized one-to-one to either the ProDisc-C device or ACDF. All enrollees were evaluated pre- and post-operatively at regular intervals through month 84. Visual Analog Scale (VAS) for neck and arm pain/intensity, Neck Disability Index (NDI), Short-Form 36 (SF-36), and satisfaction were assessed. Twenty-two patients were randomized to each arm of the study. Nineteen additional patients received the ProDisc-C via continued access. NDI improved with the ProDisc-C more than with ACDF. Total range of motion was maintained with the ProDisc-C, but diminished with ACDF. Neck and arm pain improved more in the ProDisc-C than ACDF group. Patient satisfaction remained higher in the ProDisc-C group at 7 years. SF-36 scores were higher in the TDA group than ACDF group at 7 years; the difference was not clinically significant. Six additional operations (two at the same level; four at an adjacent level) were performed in the ACDF, but none in the ProDisc-C group. The ProDisc-C implant appears to be safe and effective for the treatment of SCDD. Patients with the implant retained motion at the involved segment and had a lower reoperation rate than those with an ACDF.

The Gas Content Of Protoplanetary Herbig Ae/be Discs As Seen With Herschel

NASA Astrophysics Data System (ADS)

Meeus, Gwendolyn; Herschel OTKP, GASPS; Dent, B.

2011-09-01

The mechanisms determining planet formation are not (yet) well-understood. Primordial protoplanetary discs consist 99% out of gas, and only 1% out of dust. With time, those discs are believed to evolve from a flaring geometry into a flat geometry, as the initially small dust grains grow to larger sizes and settle towards the mid-plane. In the mean time, the gas will disperse, until so little is left that giant planets no longer can form. As an important piece of the puzzle of planet formation, it is important to understand the influence of the gas heating/cooling processes on the young disc structure, its chemical composition and finally how fast gas gets dispersed. In this talk, we study the protoplanetary discs around Herbig Ae/Be stars, young objects of intermediate mass, in the context of its gas content. We present Herschel PACS spectroscopic observations for a sample that was obtained within the GASPS (Gas in Protoplanetary Systems) Open Time Key Project, concentrating on the detection and characterisation of emission lines of the [OI], [CII], and CO, tracing the disc between 5 and 500 AU. We look for correlations between the observed line fluxes and stellar properties such as effective temperature, Halpha emission, accretion rates and UV flux, as well as the disc properties: degree of flaring, presence and strength of PAH emission and disc mass. We will present a few cases to show how simultaneous modeling (using the thermo-chemical disc code ProDiMo) of the atomic fine structure lines and both molecular lines can constrain the disc gas mass, once the disc structure is derived. Finally, we compare our gas line observations with those of young debris disc stars, for which the HAEBE stars are thought to be progenitors.

Water-quality, phytoplankton, and trophic-status characteristics of Big Base and Little Base lakes, Little Rock Air Force Base, Arkansas, 2003-2004

USGS Publications Warehouse

Justus, B.G.

2005-01-01

Little Rock Air Force Base is the largest C-130 base in the Air Force and is the only C-130 training base in the Department of Defense. Little Rock Air Force Base is located in central Arkansas near the eastern edge of the Ouachita Mountains, near the Mississippi Alluvial Plain, and within the Arkansas Valley Ecoregion. Habitats include upland pine forests, upland deciduous forest, broad-leaved deciduous swamps, and two small freshwater lakes?Big Base Lake and Little Base Lake. Big Base and Little Base Lakes are used primarily for recreational fishing by base personnel and the civilian public. Under normal (rainfall) conditions, Big Base Lake has a surface area of approximately 39 acres while surface area of Little Base Lake is approximately 1 acre. Little Rock Air Force Base personnel are responsible for managing the fishery in these two lakes and since 1999 have started a nutrient enhancement program that involves sporadically adding fertilizer to Big Base Lake. As a means of determining the relations between water quality and primary production, Little Rock Air Force Base personnel have a need for biological (phytoplankton density), chemical (dissolved-oxygen and nutrient concentrations), and physical (water temperature and light transparency) data. To address these monitoring needs, the U.S. Geological Survey in cooperation with Little Rock Air Force Base, conducted a study to collect and analyze biological, chemical, and physical data. The U.S. Geological Survey sampled water quality in Big Base Lake and Little Base Lake on nine occasions from July 2003 through June 2004. Because of the difference in size, two sampling sites were established on Big Base Lake, while only one site was established on Little Base Lake. Lake profile data for Big Base Lake indicate that low dissolved- oxygen concentrations in the hypolimnion probably constrain most fish species to the upper 5-6 feet of depth during the summer stratification period. Dissolved-oxygen concentrations in Big Base Lake below a depth of 6 feet generally were less than 3 milligrams per liter for summer months that were sampled in 2003 and 2004. Some evidence indicates that phosphorus was limiting primary production during the sampling period. Dissolved nitrogen constituents frequently were detected in water samples (indicating availability) but dissolved phosphorus constituents-orthophosphorus and dissolved phosphorus-were not detected in any samples collected at the two lakes. The absence of dissolved phosphorus constituents and presence of total phosphorus indicates that all phosphorus was bound to suspended material (sediment particles and living organisms). Nitrogen:phosphorus ratios on most sampling occasions tended to be slightly higher than 16:1, which can be interpreted as further indication that phosphorus could be limiting primary production to some extent. An alkalinity of 20 milligrams per liter of calcium carbonate or higher is recommended to optimize nutrient availability and buffering capacity in recreational fishing lakes and ponds. Median values for water samples collected at the three sites ranged from 12-13 milligrams per liter of calcium carbonate. Alkalinities ranged from 9-60 milligrams per liter of calcium carbonate, but 13 of 17 samples collected at the deepest site had alkalinities less than 20 milligrams per liter of calcium carbonate. Results of three trophic-state indices, and a general trophic classification, as well as abundant green algae and large growths of blue-green algae indicate that Big Base Lake may be eutrophic. Trophic-state index values calculated using total phosphorus, chlorophyll a, and Secchi disc measurements from both lakes generally exceeded criteria at which lakes are considered to be eutrophic. A second method of determining lake trophic status-the general trophic classification-categorized the three sampling sites as mesotrophic or eutrophic. Green algae were found to be in abundance throughout mos

Water-quality characteristics of selected public recreational lakes and ponds in Connecticut

USGS Publications Warehouse

Healy, D.F.; Kulp, K.P.

1995-01-01

Reconnaissance limnological and lakebed-sediment surveys were conducted in Connecticut during 1989-91 by the U.S. Geological Survey, in cooperation with the Connecticut Department of Environmental Protec- tion, to evaluate water-quality characteristics of selected public recreational lakes and ponds in the State. Limnological surveys were conducted on 49 lakes and ponds selected from a list of 105 publicly owned waterbodies that qualified for water- quality assessments under Section 314 of the Federal Clean Water Act. Lakebed-sediment surveys were conducted in 9 river impoundments and 1 riverine lake below industrial areas and 2 headwater lakes in relatively pristine areas. The limnological surveys consisted of two sampling events--during spring turnover and during the summer stratifi- cation. Each sampling event included depth profiles of water temperature, specific conductance, hydrogen-ion activity, and dissolved oxygen concen- trations; measurements of Secchi disc transparency; and the collection of samples for the analyses of alkalinity, chlorophyll, phosphorus, and nitrogen concentrations. Areal extent and population density of the dominant aquatic macrophytes were qualita- tively noted during the summer sampling event. These water-quality data were used to determine the trophic classification and acidification status of the 49 lakes. The trophic classification yielded the following results: 2 oligotrophic, 8 early mesotrophic, 13 mesotrophic, 5 late mesotrophic, 10 eutrophic, and 11 highly eutrophic lakes. In terms of acidification status, 7 lakes were classified as acid threatened and 42 as not threatened. A Wilcoxon two-tailed signed rank test was used to compare data for 13 lakes and ponds from the present survey with data from the 1973-75 or 1978-79 surveys conducted by the Connecticut Agricultural Experiment Station and Connecticut Department of Environmental Protection. The test showed no significant difference at the 90 percent confidence level for spring nitrogen and summer chlorophyll-a concen- trations, a significant increase at the 90 percent confidence level in summer phosphorus concentra- tions, and a significant decrease at the 95 percent confidence level in summer transparency. For the lakebed-sediment surveys, composite-grab samples were collected from the deepest part of each lake. Samples were analyzed for arsenic, cyanide, organic and inorganic carbon, selected metals, and methylene-extractable, synthetic organic compounds classified by the U.S. Environmental Protection Agency as semi-volatile priority pollutants. Hanover Pond, Eagleville Lake, and West Thompson Lake had three of the four highest concentrations of cadmium, chromium, copper, lead, nickel, zinc, and cyanide. The four lakes with the highest concentrations of arsenic (Aspinook Pond, Fitchville Pond, Mashapaug Pond, and West Thompson Lake) are located in the eastern part of Connecticut. The three samples with the highest mercury concentrations were from Lake Lillinonah and Lake Zoar. There appears to be a positive correlation between the concentrations of cadmium, chromium, copper, lead, nickel, zinc, and cyanide. Only 15 of the 54 synthetic organic compounds analyzed for were detected in 9 of the 12 lakes sampled. Of these 15 compounds, 14 are polycyclic aromatic hydrocarbons and the 15th is a phthalate ester. Hanover Pond had the most compounds detected (9), and phenanthrene was the compound detected in the most lakes (8).

A SCUBA-2 850-μm survey of protoplanetary discs in the IC 348 cluster

NASA Astrophysics Data System (ADS)

Cieza, L.; Williams, J.; Kourkchi, E.; Andrews, S.; Casassus, S.; Graves, S.; Schreiber, M. R.

2015-12-01

We present 850-μm observations of the 2-3 Myr cluster IC 348 in the Perseus molecular cloud using the SCUBA-2 camera on the James Clerk Maxwell Telescope. Our SCUBA-2 map has a diameter of 30 arcmin and contains ˜370 cluster members, including ˜200 objects with IR excesses. We detect a total of 13 discs. Assuming standard dust properties and a gas-to-dust-mass ratio of 100, we derive disc masses ranging from 1.5 to 16 MJUP. We also detect six Class 0/I protostars. We find that the most massive discs (MD > 3 MJUP; 850-μm flux > 10 mJy) in IC 348 tend to be transition objects according to the characteristic `dip' in their infrared spectral energy distributions (SEDs). This trend is also seen in other regions. We speculate that this could be an initial conditions effect (e.g. more massive discs tend to form giant planets that result in transition disc SEDs) and/or a disc evolution effect (the formation of one or more massive planets results in both a transition disc SED and a reduction of the accretion rate, increasing the lifetime of the outer disc). A stacking analysis of the discs that remain undetected in our SCUBA-2 observations suggests that their median 850-μm flux should be ≲1 mJy, corresponding to a disc mass ≲0.3 MJUP (gas plus dust) or ≲1 M⊕ of dust. While the available data are not deep enough to allow a meaningful comparison of the disc luminosity functions between IC 348 and other young stellar clusters, our results imply that disc masses exceeding the minimum-mass solar nebula are very rare (≲1per cent) at the age of IC 348, especially around very low-mass stars.

ProDisc-L total disc replacement: a comparison of 1-level versus 2-level arthroplasty patients with a minimum 2-year follow-up.

PubMed

Hannibal, Matthew; Thomas, Derek J; Low, Jeffrey; Hsu, Ken Y; Zucherman, James

2007-10-01

This is a retrospective analysis of data that was collected prospectively from 2 concurrent FDA IDE lumbar arthroplasty clinical trials performed at a single center. To determine if there is a clinical difference between the 1-level ProDisc patients versus the 2-level ProDisc patients at a minimum of 2 years of follow-up. Marnay's work with ProDisc I prompted the U.S. Clinical Trials of the ProDisc II under the direction of the FDA. Disc replacement surgery in the United States has shown promising results for all types of prostheses up to 6 months. Marnay and colleagues showed that their results at 10 years were still promising, and they saw no significant difference between 1-level and multilevel disc replacements. The findings of Ipsen and colleagues suggest that multilevel arthroplasty cases may be less successful than disc replacement at a single level. Patients were part of the FDA clinical trial for the Prodisc II versus circumferential fusion study at a single institution. We identified 27 patients who received ProDisc at 1 level and 32 who received it at 2 levels with at least a 2-year follow-up, for a total of 59 patients. Unpaired t tests were performed on the mean results of Visual Analog Scale, Oswestry Disability Index, SF-36 Healthy Survey Physical Component Summary, and satisfaction using 10-cm line visual scale scores to determine a clinical difference if any between the 2 populations. While patients receiving ProDisc at 2 levels scored marginally lower in all evaluation indexes, score differences in each category were also found to hold no statistical significance. This study was unable to identify a statistically significant difference in outcome between 1- and 2-level ProDisc arthroplasty patients in a cohort from a single center. The equality of clinical effectiveness between 1- and 2-level ProDisc has yet to be determined.

Thoracolumbar Intervertebral Disc Area Morphometry in Elderly Chinese Men and Women: Radiographic Quantifications at Baseline and Changes at Year-4 Follow-up.

PubMed

Wáng, Jùn-Qīng; Káplár, Zoltán; Deng, Min; Griffith, James F; Leung, Jason C S; Kwok, Anthony W L; Kwok, Timothy; Leung, Ping Chung; Wáng, Yì Xiáng J

2018-05-15

A population-based radiographic study with longitudinal follow-up. To develop a quantitative index for lumbar disc space narrowing (DSN) evaluation in elderly subjects; to determine how DSN in the elderly is influenced by osteoporosis and sex. There is paucity of research on quantitative classification of lumbar DSN based on disc areal morphometry. With the database of Osteoporotic Fractures in Men (Hong Kong) and Osteoporotic Fractures in Women (Hong Kong) Studies and those who attended the year-4 follow-up (n = 1519 for men and n = 1546 for women), data of 491 women and 592 men were randomly selected. The anterior, middle, and posterior heights; anteroposterior diameter; and area of intervertebral discs (T4T5 to L4L5) were measured on lateral radiographs. Disc area index for lumbar spine (DAIL, disc area divided by the mean of the sum of square of the adjacent upper and lower vertebrae mid-height anterior-posterior diameter) was developed and compared with semiquantitative DSN expert grading. DAIL correlated with semiquantitative grading, with sensitivity and specificity varying from 87.3% to 96.8% for grade 1 DSN (<30% reduction in disc height), and 92.9% to 100% for grade 3 DSN (>60% reduction in disc height). The thoracolumbar disc area loss among men and women during 4-years' follow-up period varied between 1.32% and 3.56%, and it was greater for women (mean: 2.44%) than for men (mean: 1.90%, P = 0.044). Majority of lumbar DSN progressions during 72 to 76 years old were progression from normal disc space to grade 1 DSN. Osteoporosis was associated with greater disc area decrease, both for thoracic and lumbar discs. Lumbar DSN can be quantified using DAIL. In elderly Chinese, intervertebral disc narrowing over a 4-year period was greater in women than men, and associated with the presence of osteoporosis. 3.

Low rate loading-induced convection enhances net transport into the intervertebral disc in vivo.

PubMed

Gullbrand, Sarah E; Peterson, Joshua; Mastropolo, Rosemarie; Roberts, Timothy T; Lawrence, James P; Glennon, Joseph C; DiRisio, Darryl J; Ledet, Eric H

2015-05-01

The intervertebral disc primarily relies on trans-endplate diffusion for the uptake of nutrients and the clearance of byproducts. In degenerative discs, diffusion is often diminished by endplate sclerosis and reduced proteoglycan content. Mechanical loading-induced convection has the potential to augment diffusion and enhance net transport into the disc. The ability of convection to augment disc transport is controversial and has not been demonstrated in vivo. To determine if loading-induced convection can enhance small molecule transport into the intervertebral disc in vivo. Net transport was quantified via postcontrast enhanced magnetic resonance imaging (MRI) into the discs of the New Zealand white rabbit lumbar spine subjected to in vivo cyclic low rate loading. Animals were administered the MRI contrast agent gadodiamide intravenously and subjected to in vivo low rate loading (0.5 Hz, 200 N) via a custom external loading apparatus for either 2.5, 5, 10, 15, or 20 minutes. Animals were then euthanized and the lumbar spines imaged using postcontrast enhanced MRI. The T1 constants in the nucleus, annulus, and cartilage endplates were quantified as a measure of gadodiamide transport into the loaded discs compared with the adjacent unloaded discs. Microcomputed tomography was used to quantify subchondral bone density. Low rate loading caused the rapid uptake and clearance of gadodiamide in the nucleus compared with unloaded discs, which exhibited a slower rate of uptake. Relative to unloaded discs, low rate loading caused a maximum increase in transport into the nucleus of 16.8% after 5 minutes of loading. Low rate loading increased the concentration of gadodiamide in the cartilage endplates at each time point compared with unloaded levels. Results from this study indicate that forced convection accelerated small molecule uptake and clearance in the disc induced by low rate mechanical loading. Low rate loading may, therefore, be therapeutic to the disc as it may enhance the nutrient uptake and waste product clearance. Copyright © 2015 Elsevier Inc. All rights reserved.

Biomechanical analysis of disc pressure and facet contact force after simulated two-level cervical surgeries (fusion and arthroplasty) and hybrid surgery.

PubMed

Park, Jon; Shin, Jun Jae; Lim, Jesse

2014-12-01

The objective of this study was designed to compare 2-level cervical disc surgery (2-level anterior cervical discectomy and fusion [ACDF] or disc arthroplasty) and hybrid surgery (ACDF/arthroplasty) in terms of postoperative adjacent-level intradiscal pressure (IDP) and facet contact force (FCF). Twenty-four cadaveric cervical spines (C3-T2) were tested in various modes, including extension, flexion, and bilateral axial rotation, to compare adjacent-level IDP and FCF after specified treatments as follows: 1) C5-C6 arthroplasty using ProDisc-C (Synthes Spine, West Chester, Pennsylvania, USA) and C6-C7 ACDF, 2) C5-C6 ACDF and C6-C7 arthroplasty using ProDisc-C, 3) 2-level C5-C6/C6-C7 disc arthroplasties, and 4) 2-level C5-C6/C6-C7 ACDF. IDPs were recorded at anterior, central, and posterior disc portions. After 2-level cervical arthrodesis (ACDF), IDP increased significantly at the anterior annulus of distal adjacent-level disc during flexion and axial rotation and at the center of proximal adjacent-level disc during flexion. In contrast, after cervical specified treatments, including disc arthroplasty (2-level disc arthroplasties and hybrid surgery), IDP decreased significantly at the anterior annulus of distal adjacent-level disc during flexion and extension and was unchanged at the center of proximal adjacent-level disc during flexion. Two-level cervical arthrodesis also tended to adversely impact facet loads, increasing distal rather than proximal adjacent-level FCF. Both hybrid surgery and 2-level arthroplasties seem to offer significant advantages over 2-level arthrodesis by reducing IDP at adjacent levels and approximating FCF of an intact spine. These findings suggest that cervical arthroplasties and hybrid surgery are an alternative to reduce IDP and facet loads at adjacent levels. Copyright © 2014 Elsevier Inc. All rights reserved.

X-ray and multiwavelength insights into the inner structure of high-luminosity disc-like emitters

NASA Astrophysics Data System (ADS)

Luo, B.; Brandt, W. N.; Eracleous, M.; Wu, Jian; Hall, P. B.; Rafiee, A.; Schneider, D. P.; Wu, Jianfeng

2013-02-01

We present X-ray and multiwavelength studies of a sample of eight high-luminosity active galactic nuclei (AGN) with disc-like Hβ emission-line profiles selected from the Sloan Digital Sky Survey Data Release 7. These sources have higher redshift (z ≈ 0.6) than the majority of the known disc-like emitters, and they occupy a largely unexplored space in the luminosity-redshift plane. Seven sources have typical AGN X-ray spectra with power-law photon indices of Γ ≈ 1.4-2.0; two of them show some X-ray absorption (column density NH ≈ 1021-1022 cm-2 for neutral gas). The other source, J0850+4451, has only three hard X-ray photons detected and is probably heavily obscured (NH ≳ 3 × 1023 cm-2). This object is also identified as a low-ionization broad absorption line (BAL) quasar based on Mg II λ2799 absorption; it is the first disc-like emitter reported that is also a BAL quasar. The infrared-to-ultraviolet (UV) spectral energy distributions (SEDs) of these eight sources are similar to the mean SEDs of typical quasars with a UV `bump', suggestive of standard accretion discs radiating with high efficiency, which differs from low-luminosity disc-like emitters. Studies of the X-ray-to-optical power-law slope parameters (αOX) indicate that there is no significant excess X-ray emission in these high-luminosity disc-like emitters. Energy budget analysis suggests that for disc-like emitters in general, the inner disc must illuminate and ionize the outer disc efficiently (≈15 per cent of the nuclear ionizing radiation is required on average) via direct illumination and/or scattering. Warped accretion discs are probably needed for direct illumination to work in high-luminosity objects, as their geometrically thin inner discs decrease the amount of direct illumination possible for a flat disc.

Which iodinated contrast media is the least cytotoxic to human disc cells?

PubMed

Kim, Kyung-Hyun; Park, Jeong-Yoon; Park, Hyo-Suk; Kuh, Sung-Uk; Chin, Dong-Kyu; Kim, Keun-Su; Cho, Yong-Eun

2015-05-01

Iodinated contrast media (CM) is commonly used for various intradiscal injections such as in discography and endoscopic spinal surgery. However, CM has been shown to be toxic to renal tissue due to its ionic strength and osmolarity and as a result of iodine-induced cytotoxicity, which has raised concern over whether there are similar negative effects on disc cells. This in vitro study was designed to identify the least cytotoxic iodinated CM to the human disc cell among four different physiochemical iodinated contrast dyes. In vitro laboratory study. Intervertebral disc tissue was obtained by discectomy from a total of 10 lumbar disc patients undergoing surgery and disc cells were isolated. The human disc cells were grown in 3D alginate bead culture with 0, 0.1, 10, and 100 mg/mL CM solutions (ionic dimer, ionic monomer, non-ionic dimer, and non-ionic monomer) and mannitol as a control for 2 days. The living cells were analyzed with trypan blue staining. Fluorescence-activated cell sorting analysis was performed using Annexin V and propidium iodide (PI) and 3D alginate bead immunostaining to identify live, apoptotic, and necrotic cells. Human disc cell death was time- and dose-dependent in response to CM and more necrosis was observed than apoptosis. In addition, non-ionic dimeric CM (iodixanol) showed the least toxic effect on human disc cells, followed by non-ionic monomeric (iopromide), ionic dimeric (ioxaglate), and ionic monomeric CM (ioxithalamate). Contrast media is cytotoxic to human disc cells in a dose- and time-dependent manner. This in vitro study revealed that, among four different CM preparations, non-ionic dimeric CM is the least detrimental to human disc cell viability. Careful attention should be paid to the type of CM chosen for discography and endoscopic spinal surgery. It is also necessary to investigate the detrimental effects of CM on disc cells and disc degeneration in further in vivo studies. Copyright © 2015 Elsevier Inc. All rights reserved.

Molecules in Protoplanetary HAEBE discs as seen with Herschel.

NASA Astrophysics Data System (ADS)

Meeus, G.

2011-05-01

The discovery of planets around other stars has revealed that planet formation is ubiquitous. However, the mechanisms determining planet formation are not (yet) well-understood. Primordial protoplanetary discs consist 99% out of gas, and only 1% out of dust. With time, those discs are believed to evolve from a flaring geometry into a flat geometry, as the initially small dust grains grow to larger sizes and settle towards the mid-plane. In the mean time, the gas will disperse, until so little is left that giant planets no longer can form. It is thus important to understand the chemical composition of the disc and the influence of the gas heating/cooling processes on the disc structure, and finally how gas gets dispersed as a pieces of the puzzle of planet formation. In this contribution, we study the protoplanetary discs around Herbig Ae/Be stars, young objects of intermediate mass, in the context of gas chemistry. We present Herschel PACS spectroscopic observations for a sample that was obtained within the GASPS (Gas in Protoplanetary Systems) Open Time Key Project, concentrating on the detection and characterisation of emission lines of the molecules H20, CO and CH+ (besides [OI] and [CII]), tracing the disc between 5 and 500 AU. We look for correlations between the observed line fluxes and stellar properties such as effective temperature, Halpha emission, accretion rates and UV flux, as well as the disc properties: degree of flaring, presence and strength of PAH emission and disc mass. We will present a few cases to show how simultaneous modeling (using the thermo-chemical disc code ProDiMo) of the atomic fine structure lines and both Space Telescope and ground-based molecular lines can constrain the disc gas mass, once the disc structure is derived (here with the radiative transfer code MCFost). Finally, we compare our gas line observations with those of young debris disc stars, for which the HAEBE stars are thought to be progenitors.

Optic disc size and other parameters from optical coherence tomography in Vietnamese-Americans.

PubMed

Peng, Pai-Huei; Fu, Sheena; Nguyen, Ngoc; Porco, Travis; Lin, Shan C

2011-08-01

To investigate the optic disc parameters by optical coherence tomography (OCT) in Vietnamese with various types of glaucoma. Medical charts of Vietnamese and White patients within a single practice were reviewed. Disc and rim areas by OCT were compared among nonglaucoma controls, different types of glaucoma, and glaucoma suspect. The association of these parameters with demographic and ocular features was evaluated. Data from 1416 Vietnamese and 57 White patients were included. A larger mean disc area was observed in eyes with primary angle-closure glaucoma than in eyes with primary angle-closure and primary angle-closure suspect (both P<0.001). There was no association between disc size with central corneal thickness (P=0.051) and sex (P=0.155). Vietnamese patients with glaucoma and glaucoma suspicion had larger discs than diagnosis-matched Whites (P=0.043 and 0.021, respectively). Vietnamese patients with glaucoma seem to have larger optic discs than White patients. Central corneal thickness had no association with disc area in this study population.

On the inner disc structure of MWC480: evidence for asymmetries?

NASA Astrophysics Data System (ADS)

Jamialahmadi, N.; Lopez, B.; Berio, Ph.; Matter, A.; Flament, S.; Fathivavsari, H.; Ratzka, T.; Sitko, M. L.; Spang, A.; Russell, R. W.

2018-01-01

Studying the physical conditions structuring the young circumstellar discs is required for understanding the onset of planet formation. Of particular interest is the protoplanetary disc surrounding the Herbig star MWC480. The structure and properties of the circumstellar disc of MWC480 are studied by infrared interferometry and interpreted from a modelling approach. New observations are driving this study, in particular, some recent Very Large Telescope Interferometer (VLTI)/MIDI data acquired in 2013 December. Our one-component disc model could not reproduce simultaneously all our data: the spectral energy distribution, the near-infrared Keck Interferometer data and the mid-infrared data obtained with the MIDI instrument. In order to explain all measurements, one possibility is to add an asymmetry in our one-component disc model with the assumption that the structure of the disc of MWC480 has not varied with time. Several scenarios are tested, and the one considering the presence of an azimuthal bright feature in the inner component of the disc model provides a better fit of the data.

[Epidemiology investigation and biomechanics analyses for the correlation between sacroiliac joint disorder and lumbar intervertebral disc degeneration].

PubMed

Shi, Ning-Ning; Shen, Guo-Quan; He, Shui-Yong; Guo, Ru-Bao

2014-07-01

To study the correlation between lumber disc degeneration and sacroiliac joint disorder, in order to provides a new understanding concepts and therapeutic approach for the prevention and treatment of chronic intractable low back pain. From August 2009 to October 2010,129 cases with lumbar disc herniation were studied with epidemiological methods. Among them, 61 patients with L4, disc herniation included 37 males and 24 females, ranging in aged from 20 to 75 years old, duration of the disease ranged from 1 to 144 months; The other 68 patients with L5S1 disc herniation included 32 males and 36 females,ranging in aged froml8 to 76 years old,duration of the disease ranged from 0.5 to 240 months. The clinical data, symptoms and signs,X-ray characteristics of lumbar spine and pelvis of the patients were investigated by epidemiological. The risk of lumbar disc herniation was calculated with case-control study; independent variables were screened with single factor analysis; the risk factors for lumbar disc herniation were determined with logistic regression analysis, and biomechanics analyses were taken. Among 129 patients with lumbar disc herniation, 88 cases associated with sacroiliac joint disorders, sacroiliac joint disorder was a risk factor of lumbar disc herniation (OR = 4.61, P = 0.00); 47 cases associated with sacroiliac joint disorders in 61 patients with L4,5 disc herniation, iliac crest uneven caused by iliac rotational displacement was a high risk factor of L4,5 disc herniation (OR = 11.27, P = 0.00); 41 cases associated with sacroiliac joint disorders in 68 patients with L5S1 disc herniation, lumbar sacral angle abnormalities caused by sacral tilt shift was a high risk factor L5S1 disc herniation (OR = 2.31, P = 0.03). Lumbar disc herniation and sacroiliac joint disorder are two of fallot, the two factors affect each other and there is a causal relationship. They are common exists in low back pain.

Bilateral optic disc drusen mimicking papilledema.

PubMed

Sahin, Alparslan; Cingü, Abdullah Kürşat; Ari, Seyhmus; Cinar, Yasin; Caça, Ihsan

2012-06-01

Optic disc drusen, which are calcified deposits that form anterior to the lamina cribrosa in the optic nerve, may mimic papilledema. We report herein three cases referred to us with suspicion of disc swelling and papilledema. Following ophthalmologic evaluation with B-scan ultrasound, red-free fundus photography, and computed tomography, the diagnosis of papilledema was excluded in all cases and optic disc drusen was diagnosed. Clinical suspicion of optic disc drusen in cases presenting with swelling of the optic nerve head is important in order to avoid unnecessary interventions and anxiety. The reported cases highlight the commonly encountered clinical presentations and the practical aspects of diagnosis and management of optic disc drusen.

Vertical cup-to-disc ratio measurement for diagnosis of glaucoma on fundus images

NASA Astrophysics Data System (ADS)

Hatanaka, Yuji; Noudo, Atsushi; Muramatsu, Chisako; Sawada, Akira; Hara, Takeshi; Yamamoto, Tetsuya; Fujita, Hiroshi

2010-03-01

Glaucoma is a leading cause of permanent blindness. Retinal fundus image examination is useful for early detection of glaucoma. In order to evaluate the presence of glaucoma, the ophthalmologists determine the cup and disc areas and they diagnose glaucoma using a vertical cup-to-disc ratio. However, determination of the cup area is very difficult, thus we propose a method to measure the cup-to-disc ratio using a vertical profile on the optic disc. First, the blood vessels were erased from the image and then the edge of optic disc was then detected by use of a canny edge detection filter. Twenty profiles were then obtained around the center of the optic disc in the vertical direction on blue channel of the color image, and the profile was smoothed by averaging these profiles. After that, the edge of the cup area on the vertical profile was determined by thresholding technique. Lastly, the vertical cup-to-disc ratio was calculated. Using seventy nine images, including twenty five glaucoma images, the sensitivity of 80% and a specificity of 85% were achieved with this method. These results indicated that this method can be useful for the analysis of the optic disc in glaucoma examinations.

Björk-Shiley strut fracture and disc escape: literature review and a method of disc retrieval.

PubMed

Hendel, P N

1989-03-01

Embolization of a prosthetic valve poppet is a rare but life-threatening event. It was reported sporadically before the introduction of the Björk-Shiley 70-degree convexoconcave prosthesis in 1980. Since that time, there have been a large number of reported mechanical failures with disc escape. The rate for the 29-mm to 33-mm mitral valves is estimated as 5.2%. In 29 of 35 patients (including the 2 presented here) in whom the site of disc lodgment could be determined, the disc was in the descending or abdominal aorta. Fifteen of these patients died. Six survivors had the disc removed at the same operation and 6 at a later operation. In 2 patients, the disc was not removed. In 2 patients in whom the disc was not removed initially, it was thought to contribute to postoperative complications. Two more cases of structural failure of the Björk-Shiley convexoconcave prosthesis are presented. A transpericardial approach to the descending aorta on bypass is described. It allows easy removal of the disc and eliminates the need for a second operation.

Molecular regulation of CCN2 in the intervertebral disc: lessons learned from other connective tissues.

PubMed

Tran, Cassie M; Shapiro, Irving M; Risbud, Makarand V

2013-08-08

Connective tissue growth factor (CCN2/CTGF) plays an important role in extracellular matrix synthesis, especially in skeletal tissues such as cartilage, bone, and the intervertebral disc. As a result there is a growing interest in examining the function and regulation of this important molecule in the disc. This review discusses the regulation of CCN2 by TGF-β and hypoxia, two critical determinants that characterize the disc microenvironment, and discusses known functions of CCN2 in the disc. The almost ubiquitous regulation of CCN2 by TGF-β, including that seen in the disc, emphasizes the importance of the TGF-β-CCN2 relationship, especially in terms of extracellular matrix synthesis. Likewise, the unique cross-talk between CCN2 and HIF-1 in the disc highlights the tissue and niche specific mode of regulation. Taken together the current literature supports an anabolic role for CCN2 in the disc and its involvement in the maintenance of tissue homeostasis during both health and disease. Further studies of CCN2 in this tissue may reveal valuable targets for the biological therapy of disc degeneration. © 2013 Elsevier B.V. All rights reserved.

Angiogenesis in the degeneration of the lumbar intervertebral disc

PubMed Central

David, Gh; Iencean, SM; Mohan, A

2010-01-01

The goal of the study is to show the histological and biochemical changes that indicate the angiogenesis of the intervertebral disc in lumbar intervertebral disc hernia and the existence of epidemiological correlations between these changes and the risk factors of lumbar intervertebral disc hernia, as well as the patient's quality of life (QOL). We have studied 50 patients aged between 18 and 73 years old, who have undergone lumbar intervertebral disc hernia surgery, making fibroblast growth factor and vascular endothelial growth factor level measurements, as elements in the process of appreciating the disc angiogenesis. Also, pre–surgery and post–surgery QOL has been measured, as well as the intensity of the pain syndrome. We have identified factors capable of stimulating vascular endothelial growth (VEGF, FGF–2) for the examined disc material, but histological examination did not show angiogenesis. The process of angiogenesis at the degenerated intervertebral disc level affects the patient's quality of life both pre and postoperatively, and may be a predictive factor for the post–operative results. Patients can prevent the appearance of angiogenesis type degenerative processes of the intervertebral disc by avoiding angiogenesis correlated factors (weight control, physical effort, and smoking). PMID:20968201

Simultaneous brightness contrast of foraging Papilio butterflies

PubMed Central

Kinoshita, Michiyo; Takahashi, Yuki; Arikawa, Kentaro

2012-01-01

This study focuses on the sense of brightness in the foraging Japanese yellow swallowtail butterfly, Papilio xuthus. We presented two red discs of different intensity on a grey background to butterflies, and trained them to select one of the discs. They were successfully trained to select either a high intensity or a low intensity disc. The trained butterflies were tested on their ability to perceive brightness in two different protocols: (i) two orange discs of different intensity presented on the same intensity grey background and (ii) two orange discs of the same intensity separately presented on a grey background that was either higher or lower in intensity than the training background. The butterflies trained to high intensity red selected the orange disc of high intensity in protocol 1, and the disc on the background of low intensity grey in protocol 2. We obtained similar results in another set of experiments with purple discs instead of orange discs. The choices of the butterflies trained to low intensity red were opposite to those just described. Taken together, we conclude that Papilio has the ability to learn brightness and darkness of targets independent of colour, and that they have the so-called simultaneous brightness contrast. PMID:22179808

Optic disc coloboma in two nigerian siblings: Case report and review of literature.

PubMed

Babalola, Y O; Olawoye, O O; Idam, P O

2017-11-01

We report two cases of bilateral asymmetric optic disc coloboma (ODC) in siblings. The index patient is a 9-year-old Nigerian girl with severe cognitive deficit who presented with a poor vision of 3 years' duration. She had a history of childhood febrile convulsions and delayed developmental milestones. Her visual acuity could not be assessed because she had a cognitive deficit and expressive aphasia. Ocular examination revealed a very large excavated right optic disc with only a strip of remnant neuro-retinal rim superiorly, and a smaller left optic disc with inferior disc excavation, superior wedge of the pink neuro-retinal rim as well as a temporal optic disc pit. No systemic features of syndromes associated with ODCs and intellectual disability were present in both patients. The younger sibling an 8-year-old girl later presented to the eye clinic with a 5-month history of poor vision in the left eye. Ocular examination revealed visual acuity of 6/6 in the right eye and counting fingers in the left eye. Dilated binocular indirect ophthalmoscopy revealed a right large excavated colobomatous disc and a left small disc with infero-temporal disc coloboma.