[Analysis on professor WANG Juyi's crevice theory from Tao Teh King].

PubMed

Luo, Lu; Wang, Juyi

2015-10-01

The crevice theory proposed by professor WANG Juyi is analyzed in this article. In the crevice theory, it is believed that the meridians are located among "skin, pulse, flesh, tendon and bone", and the crevice is the path for the transportation of qi-blood and body fluid in the body, which is the essential condition for vital movement. This is in agreement with the idea of "action through inaction" from Tao Teh King. Based on crevice theory, the abnormalities of meridians can reflex the deficiency and excess of diseases, and regulating meridians is a significant way to treat diseases, and maintaining smooth meridian is important for healthcare.

Earthquakes Promote Bacterial Genetic Exchange in Serpentinite Crevices

NASA Astrophysics Data System (ADS)

Naoto, Yoshida; Fujiura, Nori

2009-04-01

We report the results of our efforts to study the effects of seismic shaking on simulated biofilms within serpentinite fissures. A colloidal solution consisting of recipient bacterial cells (Pseudomonas sp. or Bacillus subtilis), donor plasmid DNA encoded for antibiotic resistance, and chrysotile (an acicular clay mineral that forms in crevices of serpentinite layers) were placed onto an elastic body made from gellan gum, which acted as the biofilm matrix. Silica beads, as rock analogues (i.e., chemically inert mechanical serpentinite), were placed on the gellan surface, which was coated with the colloidal solution. A rolling vibration similar to vibrations generated by earthquakes was applied, and the silica beads moved randomly across the surface of the gellan. This resulted in the recipient cells' acquiring plasmid DNA and thus becoming genetically transformed to demonstrate marked antibiotic resistance. Neither Pseudomonas sp. nor B. subtilis were transformed by plasmid DNA when chrysotile was substituted for by kaolinite or bentonite in the colloidal solution. Tough gellan (1.0%) promoted the introduction of plasmid DNA into Pseudomonas sp., but soft gellan (0.3%) had no such effect. Genetic transformation of bacteria on the surface of gellan by exposure to exogenous plasmid DNA required seismic shaking and exposure to the acicular clay mineral chrysotile. These experimental results suggest that bacterial genetic exchange readily occurs when biofilms that form in crevices of serpentinite are exposed to seismic shaking. Seismic activity may be a key factor in bacterial evolution along with the formation of biofilms within crevices of serpentinite.

POST-APPLICATION EXPOSURE POTENTIAL TO PESTICIDES IN THE RESIDENTIAL ENVIRONMENT

EPA Science Inventory

A study to investigate the temporal and spatial distributions of pesticides applied by homeowners and commercial applicators for indoor crack and crevice treatments was initiated by the U.S. EPA in 1999. In participating households, pre- and post-application samples of indoor ...

Spatial refugia mediate juvenile coral survival during coral-predator interactions

NASA Astrophysics Data System (ADS)

Gallagher, Clare; Doropoulos, Christopher

2017-03-01

Coral recruitment and juvenile growth are essential processes for coral population maintenance and recovery. A growing body of research has evaluated the influence of reef microstructure on coral settlement and post-settlement survival, showing that physical refugia enhance recruitment. These studies have evaluated coral recruit morality from competition with macroalgae and indirect predation by grazing organisms, but the impact of direct predation by corallivorous piscine species on juvenile corals and how this interacts with reef microstructure is relatively unknown. This study examined whether refugia provided by micro-crevices enhance juvenile coral survival from corallivory. Juvenile corals from two different functional groups, the slow-growing massive Porites lobata and fast-growing branching Pocillopora damicornis, with average nubbin sizes of 1.4 cm × 0.3 cm and 0.5 cm × 1.0 cm (diameter × height), respectively, were attached to experimental tiles using small (1.44 cm3) and large (8.0 cm3) crevice sizes and were monitored for 29 d on a forereef in Palau. Full crevices (four sided) enhanced coral survival compared to exposed microhabitats in both coral taxa, but crevice size did not alter survival rates. Corallivores targeted recruits within crevices regardless of crevice size; dominant predators included small triggerfish (Balistidae), butterflyfish ( Chaetodon), and wrasse ( Cheilinus). Overall, Pocillopora suffered much higher rates of mortality than Porites. All Pocillopora were consumed by day 8 of the experiment, but mortality was significantly delayed in full crevices compared to exposed and partial crevice (three sided) microhabitats. In contrast, Por. lobata located in all microhabitats survived the entire experiment up to 29 d, with high survival in full (>90%) and partial crevices (70%), but only 28% survival in exposed microhabitats. These findings show the importance of crevices as spatial refugia from predators for juvenile corals and highlight the importance of structural complexity for juvenile coral growth and survival that enhances reef recovery.

Self-organization of intertidal snails facilitates evolution of aggregation behavior.

PubMed

Stafford, Richard; Davies, Mark S; Williams, Gray A

2008-01-01

Many intertidal snails form aggregations during emersion to minimize desiccation stress. Here we investigate possible mechanisms for the evolution of such behavior. Two behavioral traits (following of mucus trails, and crevice occupation), which both provide selective advantages to individuals that possess the traits over individuals that do not, result in self-organization of aggregations in crevices in the rock surface. We suggest that the existence of self-organizing aggregations provides a mechanism by which aggregation behavior can evolve. The inclusion of an explicitly coded third behavior, aggregation, in a simulated population produces patterns statistically similar to those found on real rocky shores. Allowing these three behaviors to evolve using an evolutionary algorithm, however, results in aggregation behavior being selected against on shores with high crevice density. The inclusion of broadcast spawning dispersal mechanisms in the simulation, however, results in aggregation behavior evolving as predicted on shores with both high crevice density and low crevice density (evolving in crevices first, and then both in crevices and on flat rock), indicating the importance of environmental interactions in understanding evolutionary processes. We propose that self-organization can be an important factor in the evolution of group behaviors.

Characterisation of Crevice and Pit Solution Chemistries Using Capillary Electrophoresis with Contactless Conductivity Detector

PubMed Central

Nie, Mengyan; Wharton, Julian A.; Cranny, Andy; Harris, Nick R.; Wood, Robert J.K.; Stokes, Keith R.

2013-01-01

The ability to predict structural degradation in-service is often limited by a lack of understanding of the evolving chemical species occurring within a range of different microenvironments associated with corrosion sites. Capillary electrophoresis (CE) is capable of analysing nanolitre solution volumes with widely disparate concentrations of ionic species, thereby producing accurate and reliable results for the analysis of the chemical compositions found within microenvironment corrosion solutions, such as those found at crevice and pit corrosion sites. In this study, CE with contactless conductivity detection (CCD) has been used to characterize pitting and crevice corrosion solution chemistries for the first time. By using the capillary electrophoresis with contactless conductivity detection (CE-CCD) system, direct and simultaneous detection of seven metal cations (Cu2+, Ni2+, Fe3+, Fe2+, Cr3+, Mn2+, and Al3+) and chloride anions was achieved with a buffer solution of 10 mM 2,6-pyridinedicarboxylic acid and 0.5 mM cetyltrimethylammonium hydroxide at pH 4 using a pre-column complexation method. The detection limits obtained for the metal cations and chloride anions were 100 and 10 ppb, respectively. The CE-CCD methodology has been demonstrated to be a versatile technique capable of speciation and quantifying the ionic species generated within artificial pit (a pencil electrode) and crevice corrosion geometries for carbon steels and nickel-aluminium bronze, thus allowing the evolution of the solution chemistry to be assessed with time and the identification of the key corrosion analyte targets for structural health monitoring. PMID:28788335

Roosting ecology of the pallid bat, Antrozous pallidus

USGS Publications Warehouse

Vaughan, Terry A.; O'Shea, Thomas J.

1976-01-01

Daytime roosting behavior of pallid bats (Antrozous pallidus) was studied in central Arizona. Bats were present in the area from March or April until November and roosted in cliffs in colonies generally including 20 or more individuals. Pallid bats were highly selective in their choice of roost sites and minimized diurnal energy output by adaptive hypothermia and behavioral thermo-regulation. In spring and autumn the bats roosted in vertical crevices responsive to changes in ambient temperatures. Here temperatures remained low and the bats were torpid for much of the day, but when the crevices became heated in the late afternoon the bats were passively warmed prior to emergence. Deep, horizontal crevices were preferred in summer; cliffs function as massive heat sinks, and in summer crevice temperatures remained moderate and relatively stable. Throughout most of the day both the deep parts of the crevices and the body temperatures of the bats remained close to 30ºC; at this body temperature pallid bats have unexpectedly low metabolic rates (Trune, 1974). By adjusting their positions and closeness to other bats in the thermal gradient within the crevice, bats dissipate heat early in the day, maintain a low metabolic rate through most of the fat and elevate the body temperature prior to emergence in the evening. Of vital important to pallid bats in the summer are social behaviors that promote communal roosting at "traditional" crevices.

Niche partitioning of feeding microhabitats produces a unique function for herbivorous rabbitfishes (Perciformes, Siganidae) on coral reefs

NASA Astrophysics Data System (ADS)

Fox, R. J.; Bellwood, D. R.

2013-03-01

Niche theory predicts that coexisting species minimise competition by evolving morphological or behavioural specialisations that allow them to spread out along resource axes such as space, diet and temporal activity. These specialisations define how a species interacts with its environment and, by extension, determine its functional role. Here, we examine the feeding niche of three species of coral reef-dwelling rabbitfishes (Siganidae, Siganus). By comparing aspects of their feeding behaviour (bite location, bite rate, foraging distance) with that of representative species from two other abundant herbivorous fish families, the parrotfishes (Labridae, Scarus) and surgeonfishes (Acanthuridae, Acanthurus), we examine whether rabbitfishes have a feeding niche distinct from other members of the herbivore guild. Measurements of the penetration of the fishes' snouts and bodies into reef concavities when feeding revealed that rabbitfish fed to a greater degree from reef crevices and interstices than other herbivores. There was just a 40 % overlap in the penetration-depth niche between rabbitfish and surgeonfish and a 45 % overlap between rabbitfish and parrotfish, compared with the almost complete niche overlap (95 %) recorded for parrotfish and surgeonfish along this spatial niche axis. Aspects of the morphology of rabbitfish which may contribute to this niche segregation include a comparatively longer, narrower snout and narrower head. Our results suggest that sympatric coexistence of rabbitfish and other reef herbivores is facilitated by segregation along a spatial (and potentially dietary) axis. This segregation results in a unique functional role for rabbitfishes among roving herbivores that of "crevice-browser": a group that specifically feeds on crevice-dwelling algal or benthic organisms. This functional trait may have implications for reef ecosystem processes in terms of controlling the successional development of crevice-based algal communities, reducing their potential to trigger macroalgal outbreaks.

Nonequilibrium Synthesis of Highly Porous Single-Crystalline Oxide Nanostructures

DOE PAGES

Lee, Dongkyu; Gao, Xiang; Fan, Lisha; ...

2017-01-20

A novel synthesis route to the formation of vertically aligned single–crystalline oxide nanostructures is found by precisely controlling the nonequilibrium pulsed laser deposition process. Here, the columnar nanostructures with deep crevices offering a large surface area are generated owing to the diffusion limited geometric shadowing effect.

Corrosion inhibition of steam generator tubesheet by Alloy 690 cladding in secondary side environments

NASA Astrophysics Data System (ADS)

Hur, Do Haeng; Choi, Myung Sik; Lee, Deok Hyun; Han, Jung Ho; Shim, Hee Sang

2013-11-01

Denting is a phenomenon that a steam generator tube is distorted by a volume expansion of corrosion products of the tube support and tubesheet materials adjacent to the tube. Although denting has been mitigated by a modification of the design and material of the tube support structures, it has been an inevitable concern in the crevice region of the top of tubesheet. This paper provides a new technology to prevent denting by cladding the secondary surface of the tubesheet with a corrosion resistant material. In this study, Alloy 690 material was cladded onto the surface of an SA508 tubesheet to a thickness of about 9 mm. The corrosion rates of the original SA508 tubesheet and the Alloy 690 clad material were measured in acidic and alkaline simulated environments. Using Alloy 690 cladding, the corrosion rate of the tubesheet within a magnetite sludge pile decreased by a factor of 680 in 0.1 M NiCl2 solution at 300 °C, and by a factor of 58 in 2 M NaOH solution at 315 °C. This means that denting can drastically be prevented by cladding the secondary tubesheet surface with corrosion resistant materials.

Measurements and mechanisms of localized aqueous corrosion in aluminum-lithium alloys

NASA Technical Reports Server (NTRS)

Buchheit, Rudolph G., Jr.; Stoner, Glenn E.

1990-01-01

Like most heat treatable aluminum alloys, localized corrosion and stress corrosion of Al-Li-Cu alloys is strongly dependent on the nature and distribution of second phase particles. To develop a mechanistic understanding of the role of localized corrosion in the stress corrosion process, bulk samples of T(sub 1) (Al2CuLi) and a range of Al-Cu-Fe impurity phases were prepared for electrochemical experiments. Potentiodynamic polarization and galvanic couple experiments were performed in standard 0.6 M NaCl and in simulated crevice solutions to assess corrosion behavior of these particles with respect to the alpha-Al matrix. A comparison of time to failure versus applied potential using a constant load, smooth bar SCC test technique in Cl(-), Cl(-)/CrO4(2-), and Cl(-)/CO3(2-) environments shows that rapid failures are to be expected when applied potentials are more positive than the breakaway potential (E sub br) of T(sub 1) (crack tip) but less than E(sub br) of alpha-Al (crack walls). It is shown that this criterion is not satisfied in aerated Cl(-) solutions. Accordingly, SCC resistance is good. This criterion is satisfied, however, in an alkaline isolated fissure exposed to a CO2 containing atmosphere. Rapid failure induced by these fissures was recently termed preexposure embrittlement. Anodic polarization shows that the corrosion behavior of T(sub 1) is relatively unaffected in alkaline CO3(2-) environments but the alpha-Al phase is rapidly passivated. X ray diffraction of crevice walls from artificial crevices suggests that passivation of alpha-Al occurs as hydrotalcite-type compound (LiAl2(OH)6)2(+) - CO3(2-) - nH2O.

Western crevice and cavity-roosting bats

USGS Publications Warehouse

Bogan, Michael A.; Cryan, Paul M.; Valdez, Ernest W.; Ellison, Laura E.; O'Shea, Thomas J.

2003-01-01

Among the 45 species of bats that occur in the United States (U.S.), 34 species regularly occur in western regions of the country. Many of these “western” species choose roost sites in crevices or cavities. Herein we provide an introduction to the biology of bats that roost in cavities and crevices and assess the challenges and opportunities associated with monitoring their populations. We reviewed recent studies and examined the U.S. Geological Survey Bat Population Database (BPD) for records of western bats using crevice and cavity roosts. We found records of 25 species of western bats that use crevice or cavity roosts for at least part of their annual cycle. There were relatively few (n = 92) observations or counts for these species in the BPD, representing only 6% of the observations in the database. This paucity of records likely reflects the difficulty of observing bats in such situations rather than actual use. We found no long-term data adequate for population trend analysis among this group of bats. Since the development of miniaturized radio transmitters, our knowledge about bats that roost in cavities and crevices has increased. Future challenges associated with monitoring these species will include understanding variability in the types of roosts used as well as the roost-switching behavior exhibited by many species.

CFD simulations of Rapid Compression Machines using detailed chemistry: Evaluation of the ‘crevice containment’ concept

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

Bourgeois, Nicolas; Goldsborough, S. Scott; Jeanmart, Herve

The use of creviced pistons in Rapid Compression Machines (RCMs) has proven to be very effcient in making the temperature homogeneous inside the reaction chamber but has the disadvantage of inducing a mass transfer from the reaction chamber to the crevice, especially during the preliminary heat release of two- stage ignition processes. Aiming to mitigate this mass transfer, the technique of `crevice containment' (CC) has been proposed. It consists of a physical separa- tion between the reaction chamber and the crevice region that is engaged at the end of the compression, physically preventing any mass transfer between both parts ofmore » the geometry. In order to numerically assess this novel design concept across a broader range of conditions than previously investigated, reactive simu- lations using detailed chemical kinetic mechanisms are performed for n-heptane and iso-octane. For compressed temperatures outside of the NTC (negative temperature coeffcient) region, the CC approach is very effective in suppress- ing the influence of the crevice mass transfer and thus increases the validity of the widely-used 0-D model based on the adiabatic core assumption. Still, for most of the temperature cases inside the NTC region, the ignition appears to be precipitately initiated in the residual vortex region formed after the seal engagement, possibly inducing very significant differences with the 0-D model. The benefits of eliminating the post-compression crevice mass transfer appear to be counter-balanced by effects that have not been previously investigated in detail.« less

CFD simulations of Rapid Compression Machines using detailed chemistry: Evaluation of the ‘crevice containment’ concept

DOE PAGES

Bourgeois, Nicolas; Goldsborough, S. Scott; Jeanmart, Herve; ...

2018-01-17

The use of creviced pistons in Rapid Compression Machines (RCMs) has proven to be very effcient in making the temperature homogeneous inside the reaction chamber but has the disadvantage of inducing a mass transfer from the reaction chamber to the crevice, especially during the preliminary heat release of two- stage ignition processes. Aiming to mitigate this mass transfer, the technique of `crevice containment' (CC) has been proposed. It consists of a physical separa- tion between the reaction chamber and the crevice region that is engaged at the end of the compression, physically preventing any mass transfer between both parts ofmore » the geometry. In order to numerically assess this novel design concept across a broader range of conditions than previously investigated, reactive simu- lations using detailed chemical kinetic mechanisms are performed for n-heptane and iso-octane. For compressed temperatures outside of the NTC (negative temperature coeffcient) region, the CC approach is very effective in suppress- ing the influence of the crevice mass transfer and thus increases the validity of the widely-used 0-D model based on the adiabatic core assumption. Still, for most of the temperature cases inside the NTC region, the ignition appears to be precipitately initiated in the residual vortex region formed after the seal engagement, possibly inducing very significant differences with the 0-D model. The benefits of eliminating the post-compression crevice mass transfer appear to be counter-balanced by effects that have not been previously investigated in detail.« less

Boulder Clusters as Flow Refugia for Juvenile Salmonids and Aquatic Invertebrates in Steep Mountain Streams, Klamath Mountains, Northern California

NASA Astrophysics Data System (ADS)

Cover, M. R.; May, C. L.; Dietrich, W. E.; Resh, V. H.

2005-12-01

The availability of flow refugia and cover is an important factor affecting habitat suitability for fish and invertebrates, especially in steep, turbulent streams. In some channels, crevices beneath and between large rocks may be the only available flow refugia that allow rainbow trout (Oncorhynchus mykiss) to conserve energy and escape from high velocity flow during large storm events. Many aquatic invertebrates, especially large or crawling taxa, require cover that is provided by unembedded crevice space underneath large stones. To investigate the influence of channel type on habitat availability, we performed intensive surveys of crevice habitat for salmonids and benthic invertebrates in 12 reaches in Walker Creek, a 25 square km basin in the Klamath Mountains of Northern California. We identified four reaches in each of three channel types: plane bed (3.1% - 3.7% slope), step-pool (5.4% - 6.5% slope), and cascade (6.3% - 8.5% slope). We used 4 realistic fish models (5, 10, 15, and 20 cm length) to assess the size of crevices and presence of flow refugia associated with all cobble (64 - 256 mm) and boulder (> 256 mm) grains within five 0.5 m-wide diagonal transects. The total abundance of crevices was similar among plane bed (6.3 +/- 1.1 m-2) (Mean +/- SD), step-pool (6.2 +/- 0.25 m-2), and cascade (6.7 +/- 1.2 m-2) reaches. Small (5 cm) crevices made up the majority of crevices in all three reach types. While the presence of 5 cm and 10 cm crevices was not significantly different between the three channel types, there were significantly more large (20 cm) crevices in cascade (0.73 +/- 0.33 m-2) and step-pool (0.68 +/- 0.1 m-2) reaches than in plane bed (0.26 +/- 0.14 m-2) reaches (AVOVA, p < 0.05). Moderately sized (15 cm) crevices were more common in step-pool reaches (0.91 +/- 0.13 m-2) than either cascade (0.54 +/- 0.15 m-2) or plane bed (0.42 +/- 0.13 m-2) reaches. Based on these results we conclude that step-pool reaches provide the most favorable habitat for larger (15 to 20 cm) fish, probably due to the channel-spawning clusters of large cobbles and boulders that define this channel type. Understanding the processes that develop and maintain these open-framework clusters is important for basin-scale assessment of potential aquatic habitat.

Grand Marais Harbor, Cook County, Minnesota, Operation and Maintenance Activities, Environment Assessment Report.

DTIC Science & Technology

1974-12-01

34 - . .. .. . . . . . . -.. 2.523 In rocky crevices along the shore walls there are a variety of sedges, rushes, grasses, mosses, lichens ...our dre~tinn anid d!’aonal planu ~ for 1rand ’N r~ls Hxariors ihe a1tcrrat.v.e deacrit’,ed In’ tti..i; le.tter ealicatn. dipoa plans for l𔃺tii pollato-4

Feeding behaviour: hydrothermal vent crabs feast on sea 'snow'.

PubMed

Jeng, M-S; Ng, N K; Ng, P K L

2004-12-23

The crab Xenograpsus testudinatus lives at enormously high densities around the sulphur-rich hydrothermal vents found in shallow waters off Taiwan, even though this acidic environment is low in nutrients. Here we show that these crabs swarm out of their crevices at slack water and feed on the vast numbers of zooplankton that are killed by the vents' sulphurous plumes, and that rain down like marine 'snow'. This opportunistic feeding behaviour explains how the crabs are able to survive in the adverse toxic environment of these shallow hydrothermal vents.

Gimme shelter: The importance of crevices to some fish species inhabiting a deeper-water rocky outcrop in Southern California

USGS Publications Warehouse

Love, M.S.; Schroeder, D.M.; Lenarz, B.; Cochrane, G.R.

2006-01-01

Federal law governing fisheries management recognizes the role habitat plays in structuring fish assemblages and achieving sustainable fisheries. However, in most instances it is not known which aspects of habitat are important to the lives of fish species. In 2004, we examined the importance of sheltering sites (crevices) to fishes living along low ledges in deeper waters off Anacapa Island, southern California. We found that patterns of fish-habitat relationships varied among the eight most abundant species. Three species, bocaccio (Sebastes paucispinis), vermilion (S. miniatus), and flag (S. rubrivinctus) rockfishes, had densities one to three orders of magnitude greater in the deep crevice habitat compared to low relief rock or shallow crevice habitats. Density and mean size of the two most abundant fishes, halfbanded (S. semicinctus) and squarespot (S. hopkinsi) rockfishes, generally increased as complexity of rock habitat increased. Not all species had the highest densities in deep crevice habitat. Greenspotted rockfish (S. chlorostictus) and blackeye goby (Rhinogobiops nicholsii) showed no significant difference in density among rock habitats. Pink seaperch (Zalembius rosaceus) were absent in the deep crevice habitat and abundant only in low relief rock habitats. Our study implies that it is not sufficient to distinguish only between soft and hard bottom types when using habitat to guide fisheries management strategies. Finer-scale investigations of fish-habitat relationships, paired with habitat mapping and groundtruthing, aid in the design and positioning of Marine Park Areas (MPAs) and are necessary to facilitate understanding of how a particular MPA may contribute to fisheries management.

Autumn migration and selection of rock crevices as hibernacula by big brown bats in Colorado

USGS Publications Warehouse

Neubaum, D.J.; O'Shea, T.J.; Wilson, K.R.

2006-01-01

Movements, distribution, and roosting requirements of most species of temperate-zone bats in autumn are poorly understood. We conducted the 1st radiotelemetry study of autumn migrations and prehibernation roost selection of bats in western North America. Big brown bats (Eptesicus fuscus, n = 55) in the Poudre River watershed, Colorado, moved from low-elevation summer ranges to high-elevation locations in autumn, where they roosted in rock crevices during the period leading up to winter hibernation. We characterized rock crevices used as roosts in autumn at these higher elevations at microhabitat and landscape scales. We used logistic regression combined with an information theoretic approach to determine which variables were most important in roost selection. At the microhabitat scale, autumn roosts were higher to the ground above and below the exit point and were in deeper crevices that had more constant temperatures than randomly selected crevices. At the landscape scale, aspect of the hillside was important, with autumn roosts typically facing north-northwest. Autumn roosts fell into 2 categories: those used for a few days (transient roosts) and those used for ≥7 days and presumed to be hibernacula. Temperature regimes in the presumed hibernacula appear to provide optimal conditions for use of winter torpor, whereas transient roosts may offer passive rewarming and energy savings for bats still active in early autumn. Elevational segregation of sexes also was documented in our region, with a preponderance of females found at lower elevations and males at higher elevations in summer. Sex ratios at higher elevations became even in autumn. Use of short elevational migrations and selection of hibernation sites in rock crevices may be a common overwintering strategy of insectivorous bats of western North America.

Visualization and Analysis of Biomaterial-Centered Thrombus Formation within a Defined Crevice Under Flow

PubMed Central

Jamiolkowski, Megan A.; Pedersen, Drake D.; Wu, Wei-Tao; Antaki, James F.; Wagner, William R.

2016-01-01

The blood flow pathway within a device, together with the biomaterial surfaces and status of the patient’s blood, are well-recognized factors in the development of thrombotic deposition and subsequent embolization. Blood flow patterns are of particular concern for devices such as blood pumps (i.e. ventricular assist devices, VADs) where shearing forces can be high, volumes are relatively large, and the flow fields can be complex. However, few studies have examined the effect of geometric irregularities on thrombus formation on clinically relevant opaque materials under flow. The objective of this study was to quantify human platelet deposition onto Ti6Al4V alloys, as well as positive and negative control surfaces, in the region of defined crevices (~50–150 µm in width) that might be encountered in many VADs or other cardiovascular devices. To achieve this, reconstituted fresh human blood with hemoglobin-depleted red blood cells (to achieve optical clarity while maintaining relevant rheology), long working optics, and a custom designed parallel plate flow chamber were employed. The results showed that the least amount of platelet deposition occurred in the largest crevice size examined, which was counterintuitive. The greatest levels of deposition occurred in the 90 µm and 53 µm crevices at the lower wall shear rate. The results suggest that while crevices may be unavoidable in device manufacturing, the crevice size might be tailored, depending on the flow conditions, to reduce the risk of thromboembolic events. Further, these data might be used to improve the accuracy of predictive models of thrombotic deposition in cardiovascular devices to help optimize the blood flow path and reduce device thrombogenicity. PMID:27156141

Chlorpyrifos accumulation patterns for child-accessible surfaces and objects and urinary metabolite excretion by children for 2 weeks after crack-and-crevice application.

PubMed

Hore, Paromita; Robson, Mark; Freeman, Natalie; Zhang, Jim; Wartenberg, Daniel; Ozkaynak, Halûk; Tulve, Nicolle; Sheldon, Linda; Needham, Larry; Barr, Dana; Lioy, Paul J

2005-02-01

The Children's Post-Pesticide Application Exposure Study (CPPAES) was conducted to look at the distribution of chlorpyrifos within a home environment for 2 weeks after a routine professional crack-and-crevice application and to determine the amount of the chlorpyrifos that is absorbed by a child living within the home. Ten residential homes with a 2- to 5-year-old child in each were selected for study, and the homes were treated with chlorpyrifos. Pesticide measurements were made from the indoor air, indoor surfaces, and plush toys. In addition, periodic morning urine samples were collected from each of the children throughout the 2-week period. We analyzed the urine samples for 3,5,6-trichloropyridinol, the primary urinary metabolite of chlorpyrifos, and used the results to estimate the children's absorbed dose. Average chlorpyrifos levels in the indoor air and surfaces were 26 (pretreatment)/120 (posttreatment) ng/m3 and 0.48 (pretreatment)/2.8 (posttreatment) ng/cm2, respectively, reaching peak levels between days 0 and 2; subsequently, concentrations decreased throughout the 2-week period. Chlorpyrifos in/on the plush toys ranged from 7.3 to 1,949 ng/toy postapplication, with concentrations increasing throughout the 2-week period, demonstrating a cumulative adsorption/absorption process indoors. The daily amount of chlorpyrifos estimated to be absorbed by the CPPAES children postapplication ranged from 0.04 to 4.8 microg/kg/day. During the 2 weeks after the crack-and-crevice application, there was no significant increase in the amount of chlorpyrifos absorbed by the CPPAES children.

Results from Alloy 600 And Alloy 690 Caustic SCC Model Boiler Tests

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

Miller, Frederick D.; Thomas, Larry E.

2009-08-03

A versatile model boiler test methodology was developed and used to compare caustic stress corrosion cracking (SCC) of mill annealed Alloy 600 and thermally treated Alloy 690. The model boiler included simulated crevice devices that efficiently and consistently concentrated Na2CO3, resulting in volatilization of CO2 with the steam and concentration of NaOH at the tube surfaces. The test methodology also included variation in tube stress, either produced by the primary to secondary side pressure differential, or by a novel method that reproducibly yields a higher stress condition on the tube. The significant effect of residual stress on tube SCC wasmore » also considered. SCC of both Alloy 600 and Alloy 690 were evaluated as a function of temperature and stress. Analytical transmission electron microscopy (ATEM) evaluations of the cracks and the grain boundaries ahead of the cracks were performed, providing insight into the SCC mechanism. This model boiler test methodology may be applicable to a range of bulkwater secondary chemistries that concentrate to produce aggressive crevice environments.« less

Crevice corrosion - NaCl concentration map for grade-2 titanium at elevated temperature

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

Tsujikawa, Shigeo; Kojima, Yoichi

1993-12-31

The repassivation potential, ER, for metal/metal-crevice of Commercially Pure Titanium, C.P.Ti, was determined in NaCl solutions at temperatures up to 250C. The ER has its least noble value near 100C and becomes more noble as the temperature increases. As shown in previous research, the shrinkage of the repassivation region should continue with increasing temperatures. However, in conducting this same experiment at temperatures higher than 100C, an examination of the NaCl concentration - temperature - crevice corrosion map verifies that the repassivation region began to expand again when the temperature exceeded 140C. This expansion continued as the temperature continued to increase.

The role of trapped bubbles in kidney stone detection with the color Doppler ultrasound twinkling artifact.

PubMed

Simon, Julianna C; Sapozhnikov, Oleg A; Kreider, Wayne; Breshock, Michael; Williams, James C; Bailey, Michael R

2018-01-09

The color Doppler ultrasound twinkling artifact, which highlights kidney stones with rapidly changing color, has the potential to improve stone detection; however, its inconsistent appearance has limited its clinical utility. Recently, it was proposed stable crevice bubbles on the kidney stone surface cause twinkling; however, the hypothesis is not fully accepted because the bubbles have not been directly observed. In this paper, the micron or submicron-sized bubbles predicted by the crevice bubble hypothesis are enlarged in kidney stones of five primary compositions by exposure to acoustic rarefaction pulses or hypobaric static pressures in order to simultaneously capture their appearance by high-speed photography and ultrasound imaging. On filming stones that twinkle, consecutive rarefaction pulses from a lithotripter caused some bubbles to reproducibly grow from specific locations on the stone surface, suggesting the presence of pre-existing crevice bubbles. Hyperbaric and hypobaric static pressures were found to modify the twinkling artifact; however, the simple expectation that hyperbaric exposures reduce and hypobaric pressures increase twinkling by shrinking and enlarging bubbles, respectively, largely held for rough-surfaced stones but was inadequate for smoother stones. Twinkling was found to increase or decrease in response to elevated static pressure on smooth stones, perhaps because of the compression of internal voids. These results support the crevice bubble hypothesis of twinkling and suggest the kidney stone crevices that give rise to the twinkling phenomenon may be internal as well as external.

The role of trapped bubbles in kidney stone detection with the color Doppler ultrasound twinkling artifact

NASA Astrophysics Data System (ADS)

Simon, Julianna C.; Sapozhnikov, Oleg A.; Kreider, Wayne; Breshock, Michael; Williams, James C., Jr.; Bailey, Michael R.

2018-01-01

The color Doppler ultrasound twinkling artifact, which highlights kidney stones with rapidly changing color, has the potential to improve stone detection; however, its inconsistent appearance has limited its clinical utility. Recently, it was proposed stable crevice bubbles on the kidney stone surface cause twinkling; however, the hypothesis is not fully accepted because the bubbles have not been directly observed. In this paper, the micron or submicron-sized bubbles predicted by the crevice bubble hypothesis are enlarged in kidney stones of five primary compositions by exposure to acoustic rarefaction pulses or hypobaric static pressures in order to simultaneously capture their appearance by high-speed photography and ultrasound imaging. On filming stones that twinkle, consecutive rarefaction pulses from a lithotripter caused some bubbles to reproducibly grow from specific locations on the stone surface, suggesting the presence of pre-existing crevice bubbles. Hyperbaric and hypobaric static pressures were found to modify the twinkling artifact; however, the simple expectation that hyperbaric exposures reduce and hypobaric pressures increase twinkling by shrinking and enlarging bubbles, respectively, largely held for rough-surfaced stones but was inadequate for smoother stones. Twinkling was found to increase or decrease in response to elevated static pressure on smooth stones, perhaps because of the compression of internal voids. These results support the crevice bubble hypothesis of twinkling and suggest the kidney stone crevices that give rise to the twinkling phenomenon may be internal as well as external.

Corrosion of titanium: Part 1: aggressive environments and main forms of degradation.

PubMed

Prando, Davide; Brenna, Andrea; Diamanti, Maria Vittoria; Beretta, Silvia; Bolzoni, Fabio; Ormellese, Marco; Pedeferri, MariaPia

2017-11-11

Titanium has outstanding corrosion resistance due to the external natural oxide protective layer formed when it is exposed to an aerated environment. Despite this, titanium may suffer different forms of corrosion in severe environments: uniform corrosion, pitting and crevice corrosion, hydrogen embrittlement, stress-corrosion cracking, fretting corrosion and erosion. In this first review, forms of corrosion affecting titanium are analyzed based on a wide literature review. For each form of corrosion, the mechanism and most severe environment are reported according to the current understanding.In the second part, this review will address the possible surface treatments that can increase corrosion resistance on commercially pure titanium: Electrochemical anodizing, thermal oxidation, chemical oxidation and bulk treatments such as alloying will be considered, highlighting the advantages of each technique.

Chlorpyrifos Accumulation Patterns for Child-Accessible Surfaces and Objects and Urinary Metabolite Excretion by Children for 2 Weeks after Crack-and-Crevice Application

PubMed Central

Hore, Paromita; Robson, Mark; Freeman, Natalie; Zhang, Jim; Wartenberg, Daniel; Özkaynak, Halûk; Tulve, Nicolle; Sheldon, Linda; Needham, Larry; Barr, Dana; Lioy, Paul J.

2005-01-01

The Children’s Post-Pesticide Application Exposure Study (CPPAES) was conducted to look at the distribution of chlorpyrifos within a home environment for 2 weeks after a routine professional crack-and-crevice application and to determine the amount of the chlorpyrifos that is absorbed by a child living within the home. Ten residential homes with a 2- to 5-year-old child in each were selected for study, and the homes were treated with chlorpyrifos. Pesticide measurements were made from the indoor air, indoor surfaces, and plush toys. In addition, periodic morning urine samples were collected from each of the children throughout the 2-week period. We analyzed the urine samples for 3,5,6-trichloropyridinol, the primary urinary metabolite of chlorpyrifos, and used the results to estimate the children’s absorbed dose. Average chlorpyrifos levels in the indoor air and surfaces were 26 (pretreatment)/120 (posttreatment) ng/m3 and 0.48 (pretreatment)/2.8 (posttreatment) ng/cm2, respectively, reaching peak levels between days 0 and 2; subsequently, concentrations decreased throughout the 2-week period. Chlorpyrifos in/on the plush toys ranged from 7.3 to 1,949 ng/toy postapplication, with concentrations increasing throughout the 2-week period, demonstrating a cumulative adsorption/absorption process indoors. The daily amount of chlorpyrifos estimated to be absorbed by the CPPAES children postapplication ranged from 0.04 to 4.8 μg/kg/day. During the 2 weeks after the crack-and-crevice application, there was no significant increase in the amount of chlorpyrifos absorbed by the CPPAES children. PMID:15687060

Does the extracorporeal circulation worsen anemia in hemodialysis patients? Investigation with advanced microscopes of red blood cells drawn at the beginning and end of dialysis.

PubMed

Stamopoulos, Dimosthenis; Bakirtzi, Nerantzoula; Manios, Efthymios; Grapsa, Eirini

2013-01-01

In hemodialysis (HD) patients, anemia relates to three main factors: insufficient production of erythropoietin; impaired management of iron; and decreased lifespan of red blood cells (RBCs). The third factor can relate to structural deterioration of RBCs due to extrinsic (extracorporeal circuit; biochemical activation and/or mechanical stress during dialysis) and intrinsic (uremic milieu; biochemical interference of the RBC membrane constituents with toxins) mechanisms. Herein, we evaluate information accessed with advanced imaging techniques at the cellular level. Atomic force and scanning electron microscopes were employed to survey intact RBCs (iRBCs) of seven HD patients in comparison to seven healthy donors. The extrinsic factor was investigated by contrasting pre- and post-HD samples. The intrinsic environment was investigated by comparing the microscopy data with the clinical ones. The iRBC membranes of the enrolled HD patients were overpopulated with orifice-like (high incidence; typical size within 100-1,000 nm) and crevice-like (low incidence; typical size within 500-4,000 nm) defects that exhibited a statistically significant (P < 0.05) relative increase (+55% and +350%, respectively) in respect to healthy donors. The relative variation of the orifice and crevice indices (mean population of orifices and crevices per top membrane surface) between pre- and post-HD was not statistically significant (-3.3% and +4.5%, respectively). The orifice index correlates with the concentrations of urea, calcium, and phosphorus, but not, however, with that of creatinine. Extracorporeal circulation is not detrimental to the structural integrity of RBC membranes. Uremic milieu is a candidate cause of RBC membrane deterioration, which possibly worsens anemia.

Does the extracorporeal circulation worsen anemia in hemodialysis patients? Investigation with advanced microscopes of red blood cells drawn at the beginning and end of dialysis

PubMed Central

Stamopoulos, Dimosthenis; Bakirtzi, Nerantzoula; Manios, Efthymios; Grapsa, Eirini

2013-01-01

Background In hemodialysis (HD) patients, anemia relates to three main factors: insufficient production of erythropoietin; impaired management of iron; and decreased lifespan of red blood cells (RBCs). The third factor can relate to structural deterioration of RBCs due to extrinsic (extracorporeal circuit; biochemical activation and/or mechanical stress during dialysis) and intrinsic (uremic milieu; biochemical interference of the RBC membrane constituents with toxins) mechanisms. Herein, we evaluate information accessed with advanced imaging techniques at the cellular level. Methods Atomic force and scanning electron microscopes were employed to survey intact RBCs (iRBCs) of seven HD patients in comparison to seven healthy donors. The extrinsic factor was investigated by contrasting pre- and post-HD samples. The intrinsic environment was investigated by comparing the microscopy data with the clinical ones. Results The iRBC membranes of the enrolled HD patients were overpopulated with orifice-like (high incidence; typical size within 100–1,000 nm) and crevice-like (low incidence; typical size within 500–4,000 nm) defects that exhibited a statistically significant (P < 0.05) relative increase (+55% and +350%, respectively) in respect to healthy donors. The relative variation of the orifice and crevice indices (mean population of orifices and crevices per top membrane surface) between pre- and post-HD was not statistically significant (−3.3% and +4.5%, respectively). The orifice index correlates with the concentrations of urea, calcium, and phosphorus, but not, however, with that of creatinine. Conclusion Extracorporeal circulation is not detrimental to the structural integrity of RBC membranes. Uremic milieu is a candidate cause of RBC membrane deterioration, which possibly worsens anemia. PMID:24143093

THE DISTRIBUTION OF CHLORPYRIFOS FOLLOWING A CRACK AND CREVICE TYPE APPLICATION IN THE U.S. EPA INDOOR AIR QUALITY RESEARCH HOUSE

EPA Science Inventory

A study was conducted in the U.S. EPA Indoor Air Quality Research House to determine the spatial and temporal distribution of chlorpyrifos following a professional crack and crevice application in the kitchen. Following the application, measurements were made in the kitchen, de...

THE DISTRIBUTION OF CHLORPYRIFOS FOLLOWING A CRACK AND CREVICE TYPE APPLICATION IN THE U.S. EPA INDOOR AIR QUALITY RESEARCH HOUSE

EPA Science Inventory

The paper gives results of a study to determine the spatial and temporal distribution of chlorpyrifos following a professional crack-and-crevice application in the kitchen of the U.S. EPA's indoor air quality research house in North Carolina. Following the application, measuremen...

THE DISTRIBUTION OF CHLORPYRIFOS FOLLOWING A CRACK AND CREVICE TYPE APPLICATION IN THE U.S. EPA INDOOR AIR QUALITY TEST HOUSE

EPA Science Inventory

A study was conducted in the U.S. EPA Indoor Air Quality Test House to determine the spatial and temporal distribution of chlorpyrifos following a professional crack and crevice application in the kitchen. Following the application, measurements were made in the kitchen, den a...

Disruption of a hydrogen bond network in human versus spider monkey cytochrome c affects heme crevice stability.

PubMed

Goldes, Matthew E; Jeakins-Cooley, Margaret E; McClelland, Levi J; Mou, Tung-Chung; Bowler, Bruce E

2016-05-01

The hypothesis that the recent rapid evolution of primate cytochromes c, which primarily involves residues in the least stable Ω-loop (Ω-loop C, residues 40-57), stabilizes the heme crevice of cytochrome c relative to other mammals, is tested. To accomplish this goal, we have compared the properties of human and spider monkey cytochrome c and a set of four variants produced in the process of converting human cytochrome c into spider monkey cytochrome c. The global stability of all variants has been measured by guanidine hydrochloride denaturation. The stability of the heme crevice has been assessed with the alkaline conformational transition. Structural insight into the effects of the five amino acid substitutions needed to convert human cytochrome c into spider monkey cytochrome c is provided by a 1.15Å resolution structure of spider monkey cytochrome c. The global stability for all variants is near 9.0kcal/mol at 25°C and pH7, which is higher than that observed for other mammalian cytochromes c. The heme crevice stability is more sensitive to the substitutions required to produce spider monkey cytochrome c with decreases of up to 0.5 units in the apparent pKa of the alkaline conformational transition relative to human cytochrome c. The structure of spider monkey cytochrome c indicates that the Y46F substitution destabilizes the heme crevice by disrupting an extensive hydrogen bond network that connects three surface loops including Ω-loop D (residues 70-85), which contains the Met80 heme ligand. Copyright © 2015 Elsevier Inc. All rights reserved.

Marine Corrosion.

DTIC Science & Technology

1985-04-24

cor- rosion resistant alloys such as molybdenum -containing stainless steels. For the latter the high degree of aeration in the splashing water...imposed by marine technology, such as elevated temperatures , tensile stresses, cyclic stresses, severe (tight) crevices, galvanic coupling and high ...corrosion in seawater in tight metal-to-non-metal crevices are titanium alloys 4, the high molybdenum nickel base alloys Hastelloy alloy C-276 and

Basking and torpor in a rock-dwelling desert marsupial: survival strategies in a resource-poor environment.

PubMed

Geiser, Fritz; Pavey, Chris R

2007-11-01

Australian deserts are characterized by unpredictability, low primary productivity, and high temperature fluctuations. Despite these adverse conditions the diversity of small insectivorous marsupials of the family Dasyuridae is surprisingly high. We quantified the thermal biology of the dasyurid Pseudantechinus madonnellensis (body mass approximately 30 g) in the wild to gain some understanding of whether the success of dasyurids in the arid zone may be related to some extent to their use of energy conservation strategies. In winter, most free-ranging Pseudantechinus frequently (58.3% of 131 animal days) entered daily torpor after midnight (mean 0157 hours) in rock crevices when outside ambient temperatures (T (a)) were low. Most animals remained torpid until the next morning when they moved while still torpid from rock crevices to sun-exposed basking sites. We visually observed basking during rewarming from torpor (mean commencement at 0943 hours) at body temperatures (T (b)) as low as 19.3 degrees C when radiant heat was high and T (a) was rising. Basking continued for the rest of the day. Torpor use was not strongly correlated with T (a), but the temporal organization of daily torpor and activity were apparently linked to the thermal characteristics of basking sites. Our study suggests that by frequently employing daily torpor and basking and by appropriately coordinating their thermal biology with that of specific locations in their environment, Pseudantechinus can reduce daily energy expenditure and thus can live and reproduce in a challenging environment. It is likely that the success of other small dasyurids and perhaps many other small mammals living in deserts is linked to employment of torpor and basking for energy conservation.

Roost selection by western long-eared myotis (Myotis evotis) in burned and unburned piñon–juniper woodlands of southwestern Colorado

USGS Publications Warehouse

Snider, E. Apple; Cryan, Paul M.; Wilson, Kenneth R.

2013-01-01

All 16 species of bats known to occur in western Colorado are found at Mesa Verde National Park (MVNP) in the southwestern United States. Since 1996, wildfires have burned more than 70% of MVNP (> 15,000 ha), potentially altering food and roosting resources for bats. During the summers of 2006–2007, we investigated roost use by reproductive female western long-eared myotis (Myotis evotis). We located 33 bat roosts in rock crevices and 1 in a juniper snag. All but 2 of the roosts were in unburned habitat. Bats roosted alone or in small groups (≤3 individuals) and switched roosts frequently (1–7 roosts per bat, median = 1.5 roosts per bat, SE = 0.5 roosts per bat). We compared occupied roosts with randomly selected unoccupied crevices and used an information theoretic approach to determine which variables were most important in determining roost use at microhabitat and landscape scales. At the microhabitat scale, maternity roosts were higher above the ground and deeper than random, unoccupied rock crevices. At the landscape scale, roosts were closer to water and farther from burned habitat than random crevices, providing reproductive female M. evotis with the best opportunities to drink and forage for insects. Tree roosts are apparently not a vital resource for reproductive female M. evotis during the summer months at our study site, presumably because of the extensive availability of rock crevices. Understanding site-specific roosting behavior is important for proper management of bat populations because differences can exist between geographic regions, even among areas with similar plant communities.

Characterization of the corrosion protection mechanism of cerium-based conversion coatings on high strength aluminum alloys

NASA Astrophysics Data System (ADS)

Pinc, William Ross

The aim of the work presented in this dissertation is to investigate the corrosion protection mechanism of cerium-based conversion coatings (CeCCs) used in the corrosion protection of high strength aluminum alloys. The corrosion resistance of CeCCs involves two general mechanisms; barrier and active. The barrier protection mechanism was influenced by processing parameters, specifically surface preparation, post-treatment, and the use of gelatin. Post-treatment and the addition of gelatin to the coating solution resulted in fewer cracks and transformation of the coating to CePO4, which increased the corrosion resistance by improving the barrier aspect of CeCCs. CeCCs were found to best act as barriers when crack size was limited and CePO4 was present in the coating. CeCCs were found to protect areas of the substrate that were exposed in the coating, indicating that the coatings were more than simple barriers. CeCCs contained large cracks, underneath which subsurface crevices were connected to the surface by the cracks. Despite the observation that no cerium was present in crevices, coatings with crevices exhibited significant corrosion protection. The impedance of post-treated coatings with crevices increased during salt spray exposure. The increase in impedance was associated with the formation of protective oxides / hydroxides; however, crevice-free coatings also exhibited active protection leading to the conclusion that the formation of interfacial layers between the CeCC and the substrate also contributed to the active protection. Based on the overall results of the study, the optimal corrosion protection of CeCCs occurred when processing conditions produced coatings with morphologies and compositions that facilitated both the barrier and active protection mechanisms.

Influence of Chloride Ion and Temperature on the Corrosion Behavior of Ni-Fe-Cr Alloy 028

NASA Astrophysics Data System (ADS)

Zhang, L. N.; Dong, J. X.; Szpunar, J. A.; Zhang, M. C.; Basu, R.

Recently, the working condition of tubing systems used in oil and natural gas industries are severer than before with the increasing exploitation of acidic gas fields. The corrosion problems induced from the corrosive environment with chloride ion medium and high temperature have been much more concerned. The presence of chloride ion can accelerate the dissolution of metals. The corrosion performance is also sensitive to the operating temperature. Classic localized corrosions such as the pitting or the crevice type due to environmental temperature and chloride ion.

Great Lakes Regional Phase 3 Commercialization Conference, Held in Detroit, Michigan on May 23 - 25, 1994

DTIC Science & Technology

1994-05-25

small highly efficient power systems to provide electricity for space applications. These converters are solar heated for near earth orbit applications...processing in NASA’s Wake Shield Facility. AMPS plans to complete product development in each of these specific technology areas utilizing SBIR...Corrosion: Crevice corrosion is a form of localized corrosion that occurs within crevices or shielded surfaces where stagnant solution is present

Laboratory Investigation of a Leaking Type 316 Socket Weld in a Boron Injection Tank Sampling Line

NASA Astrophysics Data System (ADS)

Xu, Hongqing; Fyfitch, Steve; Hosier, Ryan; Hyres, James

A leak was discovered in a Type 316 stainless steel socket weld in the sampling line for the boron injection tank. A section of the pipeline containing the leaking weld was removed for laboratory investigation that included visual and Stereovisual inspections, liquid penetrant (PT) testing, metallography, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and ferrite content determinations. The leak path was a through-wall transgranular crack in the socket weld. Cracking initiated along the weld-metal-to-base-metal interface at the tip of the crevice between the socket and pipe. The crevice was exposed to oxygenated boron solution at <180°F. Shallow intergranular attack (IGA) was found in the exposed base metal inside the crevice. Based on the investigation results, it was concluded that transgranular stress corrosion cracking (TGSCC) is the primary cracking mechanism.

Sensitivity of coral recruitment to subtle shifts in early community succession.

PubMed

Doropoulos, Christopher; Roff, George; Visser, Mart-Simone; Mumby, Peter J

2017-02-01

Community succession following disturbance depends on positive and negative interactions, the strength of which change along environmental gradients. To investigate how early succession affects coral reef recovery, we conducted an 18-month experiment in Palau, using recruitment tiles and herbivore exclusion cages. One set of reefs has higher wave exposure and had previously undergone a phase shift to macroalgae following a major typhoon, whereas the other set of reefs have lower wave exposure and did not undergo a macroalgal phase shift. Similar successional trajectories were observed at all sites when herbivores were excluded: turf algae dominated early succession, followed by shifts to foliose macroalgae and heterotrophic invertebrates. However, trajectories differed in the presence of herbivores. At low wave exposure reefs, herbivores promoted coralline algae and limited turf and encrusting fleshy algae in crevice microhabitats, facilitating optimal coral recruitment. Under medium wave exposure, relatively higher but still low coverage of turf and encrusting fleshy algae (15-25%) found in crevice microhabitats inhibited coral recruitment, persisting throughout multiple recruitment events. Our results indicate that altered interaction strength in different wave environments following disturbance can drive subtle changes in early succession that cascade to alter secondary succession to coral recruitment and system recovery. © 2016 by the Ecological Society of America.

Monitoring planktivorous seabird populations: Validating surface counts of crevice-nesting auklets using mark-resight techniques

USGS Publications Warehouse

Sheffield, L.M.; Gall, Adrian E.; Roby, D.D.; Irons, D.B.; Dugger, K.M.

2006-01-01

Least Auklets (Aethia pusilla (Pallas, 1811)) are the most abundant species of seabird in the Bering Sea and offer a relatively efficient means of monitoring secondary productivity in the marine environment. Counting auklets on surface plots is the primary method used to track changes in numbers of these crevice-nesters, but counts can be highly variable and may not be representative of the number of nesting individuals. We compared average maximum counts of Least Auklets on surface plots with density estimates based on mark–resight data at a colony on St. Lawrence Island, Alaska, during 2001–2004. Estimates of breeding auklet abundance from mark–resight averaged 8 times greater than those from maximum surface counts. Our results also indicate that average maximum surface counts are poor indicators of breeding auklet abundance and do not vary consistently with auklet nesting density across the breeding colony. Estimates of Least Auklet abundance from mark–resight were sufficiently precise to meet management goals for tracking changes in seabird populations. We recommend establishing multiple permanent banding plots for mark–resight studies on colonies selected for intensive long-term monitoring. Mark–resight is more likely to detect biologically significant changes in size of auklet breeding colonies than traditional surface count techniques.

Anode for a secondary, high-temperature electrochemical cell

DOEpatents

Vissers, Donald R.; Tani, Benjamin S.

1976-01-01

A high-temperature, secondary electrochemical cell includes an anode containing lithium, an electrolyte containing lithium ions and a cathode containing a chalcogen material such as sulfur or a metallic sulfide. The anode includes a porous substrate formed of, for instance, a compacted mass of entangled metallic fibers providing interstitial crevices for receiving molten lithium metal. The surfaces of the interstitial crevices are provided with a coating of cobalt metal to enhance the retention of the molten lithium metal within the substrate.

Aerodynamics inside a rapid compression machine

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

Mittal, Gaurav; Sung, Chih-Jen

2006-04-15

The aerodynamics inside a rapid compression machine after the end of compression is investigated using planar laser-induced fluorescence (PLIF) of acetone. To study the effect of reaction chamber configuration on the resulting aerodynamics and temperature field, experiments are conducted and compared using a creviced piston and a flat piston under varying conditions. Results show that the flat piston design leads to significant mixing of the cold vortex with the hot core region, which causes alternate hot and cold regions inside the combustion chamber. At higher pressures, the effect of the vortex is reduced. The creviced piston head configuration is demonstratedmore » to result in drastic reduction of the effect of the vortex. Experimental conditions are also simulated using the Star-CD computational fluid dynamics package. Computed results closely match with experimental observation. Numerical results indicate that with a flat piston design, gas velocity after compression is very high and the core region shrinks quickly due to rapid entrainment of cold gases. Whereas, for a creviced piston head design, gas velocity after compression is significantly lower and the core region remains unaffected for a long duration. As a consequence, for the flat piston, adiabatic core assumption can significantly overpredict the maximum temperature after the end of compression. For the creviced piston, the adiabatic core assumption is found to be valid even up to 100 ms after compression. This work therefore experimentally and numerically substantiates the importance of piston head design for achieving a homogeneous core region inside a rapid compression machine. (author)« less

Investigation of Stainless Steel Corrosion in Ultrahigh-Purity Water and Steam Systems by Surface Analytical Techniques

NASA Astrophysics Data System (ADS)

Dong, Xia; Iacocca, Ronald G.; Bustard, Bethany L.; Kemp, Craig A. J.

2010-02-01

Stainless steel pipes with different degrees of rouging and a Teflon®-coated rupture disc with severe corrosion were thoroughly investigated by combining multiple surface analytical techniques. The surface roughness and iron oxide layer thickness increase with increasing rouge severity, and the chromium oxide layer coexists with the iron oxide layer in samples with various degrees of rouging. Unlike the rouging observed for stainless steel pipes, the fast degradation of the rupture disc was caused by a crevice corrosion environment created by perforations in the protective Teflon coating. This failure analysis clearly shows the highly corrosive nature of ultrapure water used in the manufacture of pharmaceutical products, and demonstrates some of the unexpected corrosion mechanisms that can be encountered in these environments.

Selectable-Tip Corrosion-Testing Electrochemical Cell

NASA Technical Reports Server (NTRS)

Lomness, Janice; Hintze, Paul

2008-01-01

The figure depicts aspects of an electrochemical cell for pitting- corrosion tests of material specimens. The cell is designed to generate a region of corrosion having a pit diameter determined by the diameter of a selectable tip. The average depth of corrosion is controlled by controlling the total electric charge passing through the cell in a test. The cell is also designed to produce minimal artifacts associated with crevice corrosion. There are three selectable tips, having diameters of 0.1 in. (0.254 cm), 0.3 in. (0.762 cm), and 0.6 in. (1.524 cm), respectively.

Socket welds in nuclear facilities

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

Anderson, P.A.; Torres, L.L.

1995-12-31

Socket welds are easier and faster to make than are butt welds. However, they are often not used in nuclear facilities because the crevices between the pipes and the socket sleeves may be subject to crevice corrosion. If socket welds can be qualified for wider use in facilities that process nuclear materials, the radiation exposures to welders can be significantly reduced. The current tests at the Idaho Chemical Processing Plant (ICPP) are designed to determine if socket welds can be qualified for use in the waste processing system at a nuclear fuel processing plant.

Investigation of Local Hydrogen Uptake in Rescaled Model Occluded Sites Using Crevice Scaling Laws

DTIC Science & Technology

2005-04-01

13- 8 Mo . Under anodic polarization, there is a combination of x and G in a crevice or crack where the stainless steel would be passive and remain...2004). 8 . G.A. Young, Jr., J.R. Scully, "The Effects of Test Temperature , Temper and Alloyed Copper on Hydrogen Controlled Crack Growth of an A1-Zn-Mg...sharp crack tip.[16] Precipitation-aged hardened martensitic stainless steels (i.e., Fe-Cr-Ni- Mo alloys) that release hydrolysable Cr and Fe cations

PWR steam generator chemical cleaning, Phase I. Final report

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

Rothstein, S.

1978-07-01

United Nuclear Industries (UNI) entered into a subcontract with Consolidated Edison Company of New York (Con Ed) on August 8, 1977, for the purpose of developing methods to chemically clean the secondary side tube to tube support crevices of the steam generators of Indian Point Nos. 1 and 2 PWR plants. This document represents the first reporting on activities performed for Phase I of this effort. Specifically, this report contains the results of a literature search performed by UNI for the purpose of determining state-of-the-art chemical solvents and methods for decontaminating nuclear reactor steam generators. The results of the searchmore » sought to accomplish two objectives: (1) identify solvents beyond those proposed at present by UNI and Con Ed for the test program, and (2) confirm the appropriateness of solvents and methods of decontamination currently in use by UNI.« less

Consequences of volcanic ash deposition on the locomotor performance of the Phymaturus spectabilis lizard from Patagonia, Argentina.

PubMed

Cabezas-Cartes, Facundo; Kubisch, Erika Leticia; Ibargüengoytía, Nora Ruth

2014-03-01

The locomotor performance of lizards depends on their morphological and physiological adaptations to the habitat. However, when the habitat changes dramatically, for example, by a volcanic eruption, the performance of lizards may be affected. We registered the vegetation cover, the surface covered by ash, the presence of crevices suitable for Phymaturus and the rocks slopes to analyze the effects of ash accumulation produced by the eruption of Puyehue-Cordon Caulle volcanic complex on microhabitat use and availability of the Phymaturus spectabilis lizard. In addition, we studied the effect of ashes and slope on the locomotor performance of P. spectabilis by registering the maximum speed in sprint runs and long runs under four different treatments (cork and on the level, ashes and on the level, cork and slope, and ashes and slope). P. spectabilis selected microhabitats unvegetated, with crevices and steep slopes. Regarding locomotor performance, the speed of lizards was negatively affected by the presence of ash only in sprint runs on the level and in long runs with slope. The slope had a negative impact on the speed in all the treatments. These results show that the presence of volcanic ashes in the substrate might have affected the locomotor performance of the lizards, especially in long runs, and hence, the interaction of individuals with the environment, that is, escaping from predators and social behavior. © 2013 Wiley Periodicals, Inc.

Micro-topography mediates interactions between corals, algae, and herbivorous fishes on coral reefs

NASA Astrophysics Data System (ADS)

Brandl, S. J.; Hoey, A. S.; Bellwood, D. R.

2014-06-01

Processes occurring during the early life stages of corals are important for the replenishment of coral assemblages and the resilience of coral reefs. However, the factors influencing early life stages of corals are not well understood, and the role of micro-topographic complexity for habitat associations of juvenile corals is largely unexplored. This study investigated the microhabitat distribution patterns of early life stages of corals and a potential macroalgal competitor ( Turbinaria ornata) across two reef zones (reef crest and outer reef flat) on Lizard Island, Great Barrier Reef. In both reef zones, both corals and T. ornata were significantly more abundant in concealed microhabitats than in semi-concealed or open microhabitats (GLMM: P < 0.001). The prevalence of juvenile corals and T. ornata within concealed environments suggests that they might be effective refuges from grazing by herbivorous fishes. The density of juvenile corals was positively related, and density of T. ornata negatively related to the abundance of two groups of herbivorous fishes, pairing rabbitfishes, and surgeonfishes in the genus Zebrasoma (BEST ENV-BIO: r s = 0.72, P < 0.01), which feed in concealed microhabitats. This correlative evidence suggests that crevices may be important for early life stages of both coral and macroalgae, and that a specific suite of crevice-feeding fishes may influence benthic community dynamics in these microhabitats.

Technological capabilities of surface layers formation on implant made of Ti-6Al-4V ELI alloy.

PubMed

Kiel-Jamrozik, Marta; Szewczenko, Janusz; Basiaga, Marcin; Nowińska, Katarzyna

2015-01-01

The aim of the presented research was to find a combination of surface modification methods of implants made of the Ti-6Al-4V ELI alloy, that lead to formation of effective barrier for metallic ions that may infiltrate into solution. To this end, the following tests were carried out: roughness measurement, the voltamperometric tests (potentiodynamic and potentiostatic), and the ion infiltration test. The electropolishing process resulted in the lowering of surface roughness in comparison with mechanical treatment of the surface layer. The anodization process and steam sterilization increased corrosion resistance regardless of the mechanical treatment or electropolishing. The crevice corrosion tests revealed that independent of the modification method applied, the Ti-6Al-4V ELI alloy has excellent crevice corrosion resistance. The smallest quantity of ions infiltrated to the solution was observed for surface modification consisting in the mechanical treatment and anodization with the potential of 97 V. Electric parameters deter- mined during studies were the basis for effectiveness estimation of particular surface treatment methods. The research has shown that the anodization process significantly influences the pitting corrosion resistance of the Ti-6Al-4V ELI alloy independent of the previous surface treatment methods (mechanical and electrochemical). The surface layer after such modification is a protective barrier for metallic ions infiltrated to solution and protects titanium alloy against corrosive environment influence.

Initiation criteria for crevice corrosion of titanium alloys used for HLW disposal overpack

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

Akashi, Masatsune; Nakayama, Guen; Fukuda, Takanori

1998-12-31

The overpack that geologically stores the canisters containing vitrified high-level radioactive waste (HLW) for super-long term disposal is demanded of being able to hold the canisters securely for at least 1,000 years. For such a service, the greatest as well as essentially the sole factor that can mar the overpack`s working is corrosion by the groundwater. This paper discusses the notion and the methodology to prove for overpacks made of titanium (Ti) alloys that they are capable of stably maintaining the state of passivity indefinitely long time so as to be immune to the initiation of localized corrosion. it ismore » shown that (1) the critical potential for corrosion-crevice initiation, V{sub C,CREV}, can be substituted rationally by the corrosion-crevice repassivation potential, E{sub R,CREV}, which can be determined by the cyclic polarization test, and (2) the limits of safety usage of Ti alloys can be determined quantitatively by comparing E{sub R,CREV} and E{sub SP}, the steady-state corrosion potential.« less

Partial-Vacuum-Gasketed Electrochemical Corrosion Cell

NASA Technical Reports Server (NTRS)

Bonifas, Andrew P.; Calle, Luz M.; Hintze, Paul E.

2006-01-01

An electrochemical cell for making corrosion measurements has been designed to prevent or reduce crevice corrosion, which is a common source of error in prior such cells. The present cell (see figure) includes an electrolyte reservoir with O-ring-edged opening at the bottom. In preparation for a test, the reservoir, while empty, is pressed down against a horizontal specimen surface to form an O-ring seal. A purge of air or other suitable gas is begun in the reservoir, and the pressure in the reservoir is regulated to maintain a partial vacuum. While maintaining the purge and partial vacuum, and without opening the interior of the reservoir to the atmosphere, the electrolyte is pumped into the reservoir. The reservoir is then slowly lifted a short distance off the specimen. The level of the partial vacuum is chosen such that the differential pressure is just sufficient to keep the electrolyte from flowing out of the reservoir through the small O-ring/specimen gap. Electrochemical measurements are then made. Because there is no gasket (and, hence, no crevice between the specimen and the gasket), crevice corrosion is unlikely to occur.

Review of corrosion in 10- and 14-ton mild steel depleted UF{sub 6} storage cylinders

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

Lykins, M.L.

1995-08-01

A literature review was conducted to determine the type, extent and severity of corrosion found in the 10- and 14-ton mild steel depleted UF{sub 6} storage cylinders. Also discussed in this review is corrosion found in the valves and plugs used in the cylinders. Corrosion of the cylinders is a gradual process which occurs slowly over time. Understanding corrosion of the cylinders is an important concern for long term storage of the UF{sub 6} in the cylinder yards, as well as the final disposition of the depleted UF{sub 6} tails inventory in the future. The following conclusions are made frommore » the literature review: (1) The general external corrosion rate of the cylinders is about 1 to 2 mils per year (1 mil = 0.001{double_prime}). The highest general external corrosion rate was over 5 mpy on the 48G type cylinders. (2) General internal corrosion from the depleted UF{sub 6} is negligible under normal storage conditions. Crevice corrosion can occur at the cylinder/saddle interface from the retention of water in this area. Crevice corrosion can occur at the cylinder/skirt interface on the older skirted cylinders due to the lack of water drainage in this area. Crevice corrosion can occur on cylinders that have been in ground contact. Crevice corrosion and galvanic corrosion can occur where the stainless steel I.D. nameplates are attached to the cylinder. The packing nuts on the bronze one-inch valves used in the cylinders are susceptible to stress corrosion cracking (SCC). Mechanical damage from routine handling can lead to a breach in a cylinder with subsequent accelerated corrosion of the mild steel due to attack from HF and other UF{sub 6} hydrolysis by-products.« less

Nonuniform Grain Boundary Corrosion and the Local Electrode Potential in Crevicing. Types and Models of Precipitation Induced Nonuniform Grain Boundary Corrosion. Investigation of Sensitization and Grain Boundary Corrosion in Ferritic Stainless Steel. The Local Electrode Potential in Cavities, Crevices and Cracks and Its Role in Causing Degradation of Structural Materials.

DTIC Science & Technology

1987-02-01

J.R. Pickens Dept. of Metallurgy & Mining Eng. Martin Marietta Laboratories % University of Illinois 1450 South Rolling Rd. Urbana, EIl 61801...AND MINERAL DEPARTMENT OF MATERIALS SCIENCE SCIENCES METALLURGY PROGRAM 00 00 TECHNICAL REPORT February 1987 OFFICE OF NAVAL RESEARCH IContract No...725 % ~ ~ ’. -~ ~AS~~jX.%......... !1CUlnITY CLASSIFICATION OF THIS PAGE (When n#e& Entered) REPORT DOCUMENTATION PAGE READ INSTRUCTIONS

ECLSS Universal Waste Management System (UWMS) Metal Materials Compatibility Study- Electrochemical and Crevice Corrosion Evaluation

NASA Technical Reports Server (NTRS)

Lee, R. E.

2017-01-01

Electrochemical and crevice corrosion laboratory test results are presented for three noble metal candidates with possible application on the Universal Waste Management System (UWMS) in support of the Environmental Control and Life Support System (ECLSS) aboard the International Space Station (ISS). The three metal candidates, which included Inconel 625, Hastelloy C276 and Titanium 6Al-4V, were evaluated in two solutions representative of the acidic pretreatment formulations utilized during processing of waste liquids within the ECLSS. Final test results and data analysis indicated that the passive layer on all three metals provides excellent corrosion protection in both solutions under standard test conditions.

Prediction of Failure Due to Thermal Aging, Corrosion and Environmental Fracture in Amorphous and Titanium Alloys

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

Farmer, J C

2003-04-15

DARPA is exploring a number of advanced materials for military applications, including amorphous metals and titanium-based alloys. Equipment made from these materials can undergo degradation due to thermal aging, uniform corrosion, pitting, crevice corrosion, denting, stress corrosion cracking, corrosion fatigue, hydrogen induced cracking and microbial influenced corrosion. Amorphous alloys have exceptional resistance to corrosion, due in part to the absence of grain boundaries, but can undergo crystallization and other phase instabilities during heating and welding. Titanium alloys are extremely corrosion resistant due to the formation of a tenacious passive film of titanium oxide, but is prone to hydrogen absorption inmore » crevices, and hydrogen induced cracking after hydrogen absorption. Accurate predictions of equipment reliability, necessary for strategic planning, requires integrated models that account for all relevant modes of attack, and that can make probabilistic predictions. Once developed, model parameters must be determined experimentally, and the validity of models must be established through careful laboratory and field tests. Such validation testing requires state-of-the-art surface analytical techniques, as well as electrochemical and fracture mechanics tests. The interaction between those processes that perturb the local environment on a surface and those that alter metallurgical condition must be integrated in predictive models. The material and environment come together to drive various modes of corrosive attack (Figure 1). Models must be supported through comprehensive materials testing capabilities. Such capabilities are available at LLNL and include: the Long Term Corrosion Test Facility (LTCTF) where large numbers of standard samples can be exposed to realistic test media at several temperature levels; a reverse DC machine that can be used to monitor the propagation of stress corrosion cracking (SCC) in situ; and banks of potentiostats with temperature controlled cells for potentiostatic and potentiodynamic testing (Figure 2).« less

Periodontitis and periimplantitis: one and the same?

PubMed

Meffert, R M

1993-12-01

Research shows that the same anaerobic, gram-negative pathogens are present in the periodontal and implant pocket or crevice. The implants in a partially edentulous case are probably more at risk due to the bacteria being more pathogenic and a seeding mechanism from the tooth pocket to the implant crevice. In the face of a normal microbial flora, retrograde periimplantitis or radiographic bone loss without gingival changes may be due to trauma because of overloading, loading too soon, and/or loading in a lateral direction. Finally, the combination of an infective process (periimplantitis) and noninfective or traumatic process (retrograde periimplantitis) will result in rapid osseous destruction and, possibly, loss of the implant fixture(s).

A Composite Depth Scale for Sediments from Crevice Lake, Montana

USGS Publications Warehouse

Rosenbaum, J.G.; Skipp, G.; Honke, J.; Chapman, C.

2010-01-01

As part of a study to derive records of past environmental change from lake sediments in the western United States, a set of cores was collected from Crevice Lake, Montana, in late February and early March 2001. Crevice Lake (latitude 45.000N, longitude 110.578W, elevation 1,713 meters) lies adjacent to the Yellowstone River at the north edge of Yellowstone National Park. The lake is more than 31 meters deep and has a surface area of 7.76 hectares. The combination of small surface area and significant depth promote anoxic bottom-water conditions that preserve annual laminations (varves) in the sediment. Three types of cores were collected through the ice. The uppermost sediments were obtained in freeze cores that preserved the sediment water interface. Two sites were cored with a 5-centimeter diameter corer. Five cores were taken with a 2-meter-long percussion piston corer. The percussion core uses a plastic core liner with an inside diameter of 9 centimeters. Coring was done at two sites. Because of the relatively large diameter of the percussion cores, samples from these cores were used for a variety of analyses including pollen, charcoal, diatoms, stable isotopes, organic and inorganic carbon, elemental analyses, and magnetic properties.

Density-dependent coral recruitment displays divergent responses during distinct early life-history stages

PubMed Central

Evensen, Nicolas R.; Gómez-Lemos, Luis A.; Babcock, Russell C.

2017-01-01

Population growth involves demographic bottlenecks that regulate recruitment success during various early life-history stages. The success of each early life-history stage can vary in response to population density, interacting with intrinsic (e.g. behavioural) and environmental (e.g. competition, predation) factors. Here, we used the common reef-building coral Acropora millepora to investigate how density-dependence influences larval survival and settlement in laboratory experiments that isolated intrinsic effects, and post-settlement survival in a field experiment that examined interactions with environmental factors. Larval survival was exceptionally high (greater than 80%) and density-independent from 2.5 to 12 days following spawning. By contrast, there was a weak positive effect of larval density on settlement, driven by gregarious behaviour at the highest density. When larval supply was saturated, settlement was three times higher in crevices compared with exposed microhabitats, but a negative relationship between settler density and post-settlement survival in crevices and density-independent survival on exposed surfaces resulted in similar recruit densities just one month following settlement. Moreover, a negative relationship was found between turf algae and settler survival in crevices, whereas gregarious settlement improved settler survival on exposed surfaces. Overall, our findings reveal divergent responses by coral larvae and newly settled recruits to density-dependent regulation, mediated by intrinsic and environmental interactions. PMID:28573015

Mitigating Localized Corrosion Using Thermally Sprayed Aluminum (TSA) Coatings on Welded 25% Cr Superduplex Stainless Steel

NASA Astrophysics Data System (ADS)

Paul, S.; Lu, Q.; Harvey, M. D. F.

2015-04-01

Thermally sprayed aluminum (TSA) coating has been increasingly used for the protection of carbon steel offshore structures, topside equipment, and flowlines/pipelines exposed to both marine atmospheres and seawater immersion conditions. In this paper, the effectiveness of TSA coatings in preventing localized corrosion, such as pitting and crevice corrosion of 25% Cr superduplex stainless steel (SDSS) in subsea applications, has been investigated. Welded 25% Cr SDSS (coated and uncoated) with and without defects, and surfaces coated with epoxy paint were also examined. Pitting and crevice corrosion tests, on welded 25% Cr SDSS specimens with and without TSA/epoxy coatings, were conducted in recirculated, aerated, and synthetic seawater at 90 °C for 90 days. The tests were carried out at both the free corrosion potentials and an applied cathodic potential of -1100 mV saturated calomel electrode. The acidity (pH) of the test solution was monitored daily and adjusted to between pH 7.5 and 8.1, using dilute HCl solution or dilute NaOH, depending on the pH of the solution measured during the test. The test results demonstrated that TSA prevented pitting and crevice corrosion of 25% Cr SDSS in artificial seawater at 90 °C, even when 10-mm-diameter coating defect exposing the underlying steel was present.

Wave field features of shallow vertical discontinuity and their application in non-destructive detection

USGS Publications Warehouse

Liu, J.; Xia, J.; Luo, Y.; Chen, C.; Li, X.; Huang, Y.

2007-01-01

The geotechnical integrity of critical infrastructure can be seriously compromised by the presence of fractures or crevices. Non-destructive techniques to accurately detect fractures in critical infrastructure such as dams and highways could be of significant benefit to the geotechnical industry. This paper investigates the application of shallow seismic and georadar methods to the detection of a vertical discontinuity using numerical simulations. The objective is to address the kinematical analysis of a vertical discontinuity, determine the resulting wave field characteristics, and provide the basis for determining the existence of vertical discontinuities based on the recorded signals. Simulation results demonstrate that: (1) A reflection from a vertical discontinuity produces a hyperbolic feature on a seismic or georadar profile; (2) In order for a reflection from a vertical discontinuity to be produced, a reflecting horizon below the discontinuity must exist, the offset between source and receiver (x0) must be non-zero, on the same side of the vertical discontinuity; (3) The range of distances from the vertical discontinuity where a reflection event is observed is proportional to its length and to x0; (4) Should the vertical crevice (or fracture) pass through a reflecting horizon, dual hyperbolic features can be observed on the records, and this can be used as a determining factor that the vertical crevice passes through the interface; and (5) diffractions from the edges of the discontinuity can be recorded with relatively smaller amplitude than reflections and their ranges are not constrained by the length of discontinuity. If the length of discontinuity is short enough, diffractions are the dominant feature. Real-world examples show that the shallow seismic reflection method and the georadar method are capable of recording the hyperbolic feature, which can be interpreted as vertical discontinuity. Thus, these methods show some promise as effective non-destructive detection methods for locating vertical discontinuities (e.g., fractures or crevices) in infrastructure such as dams and highway pavement. ?? 2007 Elsevier B.V. All rights reserved.

The A-chain of insulin contacts the insert domain of the insulin receptor. Photo-cross-linking and mutagenesis of a diabetes-related crevice.

PubMed

Huang, Kun; Chan, Shu Jin; Hua, Qing-xin; Chu, Ying-Chi; Wang, Run-ying; Klaproth, Birgit; Jia, Wenhua; Whittaker, Jonathan; De Meyts, Pierre; Nakagawa, Satoe H; Steiner, Donald F; Katsoyannis, Panayotis G; Weiss, Michael A

2007-11-30

The contribution of the insulin A-chain to receptor binding is investigated by photo-cross-linking and nonstandard mutagenesis. Studies focus on the role of Val(A3), which projects within a crevice between the A- and B-chains. Engineered receptor alpha-subunits containing specific protease sites ("midi-receptors") are employed to map the site of photo-cross-linking by an analog containing a photoactivable A3 side chain (para-azido-Phe (Pap)). The probe cross-links to a C-terminal peptide (residues 703-719 of the receptor A isoform, KTFEDYLHNVVFVPRPS) containing side chains critical for hormone binding (underlined); the corresponding segment of the holoreceptor was shown previously to cross-link to a Pap(B25)-insulin analog. Because Pap is larger than Val and so may protrude beyond the A3-associated crevice, we investigated analogs containing A3 substitutions comparable in size to Val as follows: Thr, allo-Thr, and alpha-aminobutyric acid (Aba). Substitutions were introduced within an engineered monomer. Whereas previous studies of smaller substitutions (Gly(A3) and Ser(A3)) encountered nonlocal conformational perturbations, NMR structures of the present analogs are similar to wild-type insulin; the variant side chains are accommodated within a native-like crevice with minimal distortion. Receptor binding activities of Aba(A3) and allo-Thr(A3) analogs are reduced at least 10-fold; the activity of Thr(A3)-DKP-insulin is reduced 5-fold. The hormone-receptor interface is presumably destabilized either by a packing defect (Aba(A3)) or by altered polarity (allo-Thr(A3) and Thr(A3)). Our results provide evidence that Val(A3), a site of mutation causing diabetes mellitus, contacts the insert domain-derived tail of the alpha-subunit in a hormone-receptor complex.

Thermoregulatory challenges in the habitat of the world's smallest tortoise, Chersobius signatus.

PubMed

Loehr, Victor J T

2018-01-01

Ectotherms have various means of dealing with low environmental temperatures, but relatively few species have been rigorously investigated. Consequently, we have little information to predict how ectotherm populations might respond to global temperature changes. Tortoises from temperate and subtropical regions often overcome periodically cool conditions by hibernation, but speckled dwarf tortoises (Chersobius signatus) need to remain active to exploit ephemeral resources in their arid winter-rainfall habitat. This study investigated how dwarf tortoises cope with low temperatures in winter and spring, by measuring thermal habitat quality and thermoregulation based on differently-sized operative temperature models in sun, shade, and in deep crevices. Investigations continued in summer and autumn to obtain a year-round picture of thermoregulatory challenges. Although large models (i.e., larger than dwarf tortoises) were expected to have lower operative temperatures than smaller models, due to the former's larger thermal inertia, all model sizes had similar temperatures. Hence, the species' small body size does not appear constrained by obtainable body temperatures in cool seasons. Nevertheless, low operative temperatures in winter posed a challenge for the tortoises, which reached their field-preferred body temperature for an average of only 0.8-0.9h per day. Moreover, a low thermoregulation effectiveness suggested that tortoises traded-off physiological benefits of favourable body temperatures against predation risk. Spring and autumn provided higher temperatures, but summer caused the greatest thermoregulatory challenge. Although summer body temperatures were closer to field-preferred body temperature than in any other season, tortoises required rock crevices to avoid overheating. The small size of dwarf tortoises might help them utilise crevices. In summer, maximum operative temperatures in crevices were similar to field-preferred body temperature, indicating that an increase in environmental temperatures might be detrimental to dwarf tortoises. In light of projected temperature rises, future studies should assess if dwarf tortoises can cope with higher environmental temperatures in summer. Copyright © 2017 Elsevier Ltd. All rights reserved.

Possibilities of fish passage through the block ramp: Model-based estimation of permeability.

PubMed

Plesiński, Karol; Bylak, Aneta; Radecki-Pawlik, Artur; Mikołajczyk, Tomasz; Kukuła, Krzysztof

2018-08-01

Block ramps offer an opportunity to combine hydrotechnical structures with fish passages. The primary study objective was to evaluate the effectiveness of a block ramp for upstream fish movement in a mountain stream. Geodetic measurements of the bottom surface and water level were taken for three cross-sections. The description of the geometric and hydrodynamic parameters of the block ramp was supplemented with information on the width and length of crevices between boulders. Measurements of the geometric and hydrodynamic parameters of the block ramp were performed at 76 measurement sites, at three different types of discharge. Ichthyological data were collected in the analyzed stream. Measurements covered among others total length, width, and height of caught fish. Salmonid, cottid, balitorid, and cyprinid fish were studied. The determination of the main effects of the geometric and hydrodynamic parameters of the block ramp on the possibilities of use by target fish species employed generalized linear models (GLMs). The study shows that the block ramp cannot provide longitudinal connectivity and migration of fish occurring in the mountain stream. According to estimates, the block ramp did not meet the permeability expectations. The reason for low usefulness of the ramp for fish is particularly excessively strong water current. The stream concentration constituted an unsurmountable velocity barrier for fish moving upstream for each of the analyzed discharges. The developed model suggests that some crevices in the side zones of the ramp could be parts of the migration corridor, but only for small and medium-sized fish. At medium and high water stages, movement of fish in crevices was difficult due to fast water current, and at low and very low discharges, some crevices lost their permeability, and could become ecological traps for fish. The necessity of estimation of ramp permeability during pre-construction phase was emphasized. Copyright © 2018 Elsevier B.V. All rights reserved.

Corrosion Performance of Inconel 625 in High Sulphate Content

NASA Astrophysics Data System (ADS)

Ismail, Azzura

2016-05-01

Inconel 625 (UNS N06625) is a type of nickel-chromium-molybdenum alloy with excellent corrosion resistance in a wide range of corrosive media, being especially resistant to pitting and crevice corrosion. However, in aggressive environment, Inconel 625 will suffer corrosion attack like other metals. This research compared the corrosion performance of Inconel 625 when exposed to higher sulphate content compared to real seawater. The results reveal that Inconel 625 is excellent in resist the corrosion attack in seawater. However, at increasing temperature, the corrosion resistance of this metal decrease. The performance is same in seawater with high sulphate content at increasing temperature. It can be concluded that sulphate promote perforation on Inconel 625 and become aggressive agents that accelerate the corrosion attack.

Production of intergranular attack of alloy 600, alloy 690, and alloy 800 tubing in tubesheet crevices: Topical report

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

Scott, D.B.; Glaves, C.L.,

1987-07-01

Three model boilers, manufactured to simulate full-size tube sheet crevices, were tested with various secondary side environments. The first was faulted with organics representative of the decomposition of humic acid. The second was faulted with sodium carbonate and sodium hydroxide, while the third was faulted with sodium sulfate and sodium hydroxide. Each model contained seven tubes, which included Alloy 600 in the mill-annealed (MA) and thermally-treated (TT) conditions and Alloy 690 in the thermally-treated condition. Two models contained Alloy 800 tubes in the mill-annealed condition and one had Alloy 800 in the mill-annealed/cold-worked/glass-bead-peened condition. Two different sizes of tubesheet crevicesmore » were used in all model boilers. In the organics-faulted boiler, tubes of Alloy 600MA, Alloy 690TT and Alloy 800MA experienced no significant intergranular attack (IGA); however, the Alloy 600TT had intergranular attack (IGA) three to four grains deep. The carbonate-caustic faulted boiler experienced throughwall stress corrosion cracking (SCC) in all tubes of Alloy 600 MA and Alloy 800 MA. Eddy current indications were present in Alloy 690TT, Alloy 600TT and Alloy 800 in the mill-annealed/cold worked/glass-bead-peened condition. Metallographic examination of tubes from the third model boiler, faulted with sodium sulfate and caustic, revealed IGA in the mill-annealed Alloy 600 tubes. The IGA was more extensive in an Alloy 600 tube annealed at 1700/sup 0/F than an Alloy 600 tube annealed at 1875/sup 0/F.« less

Analysis of in vivo corrosion of 316L stainless steel posterior thoracolumbar plate systems: a retrieval study.

PubMed

Majid, Kamran; Crowder, Terence; Baker, Erin; Baker, Kevin; Koueiter, Denise; Shields, Edward; Herkowitz, Harry N

2011-12-01

One hundred eighteen patients retrieved 316L stainless steel thoracolumbar plates, of 3 different designs, used for fusion in 60 patients were examined for evidence of corrosion. A medical record review and statistical analysis were also carried out. This study aims to identify types of corrosion and examine preferential metal ion release and the possibility of statistical correlation to clinical effects. Earlier studies have found that stainless steel spine devices showed evidence of mild-to-severe corrosion; fretting and crevice corrosion were the most commonly reported types. Studies have also shown the toxicity of metal ions released from stainless steel corrosion and how the ions may adversely affect bone formation and/or induce granulomatous foreign body responses. The retrieved plates were visually inspected and graded based on the degree of corrosion. The plates were then analyzed with optical microscopy, scanning electron microscopy, and energy dispersive x-ray spectroscopy. A retrospective medical record review was performed and statistical analysis was carried out to determine any correlations between experimental findings and patient data. More than 70% of the plates exhibited some degree of corrosion. Both fretting and crevice corrosion mechanisms were observed, primarily at the screw plate interface. Energy dispersive x-ray spectroscopy analysis indicated reductions in nickel content in corroded areas, suggestive of nickel ion release to the surrounding biological environment. The incidence and severity of corrosion was significantly correlated with the design of the implant. Stainless steel thoracolumbar plates show a high incidence of corrosion, with statistical dependence on device design.

Structure of the Minor Pseudopilin EpsH From the Type 2 Secretion System of Vibrio Cholerae

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

Yanez, M.E.; Korotkov, K.V.; Abendroth, J.

2009-05-28

Many Gram-negative bacteria use the multi-protein type II secretion system (T2SS) to selectively translocate virulence factors from the periplasmic space into the extracellular environment. In Vibrio cholerae the T2SS is called the extracellular protein secretion (Eps) system, which translocates cholera toxin and several enzymes in their folded state across the outer membrane. Five proteins of the T2SS, the pseudopilins, are thought to assemble into a pseudopilus, which may control the outer membrane pore EpsD, and participate in the active export of proteins in a 'piston-like' manner. We report here the 2.0 {angstrom} resolution crystal structure of an N-terminally truncated variantmore » of EpsH, a minor pseudopilin from Vibrio cholerae. While EpsH maintains an N-terminal {alpha}-helix and C-terminal {beta}-sheet consistent with the type 4a pilin fold, structural comparisons reveal major differences between the minor pseudopilin EpsH and the major pseudopilin GspG from Klebsiella oxytoca: EpsH contains a large {beta}-sheet in the variable domain, where GspG contains an {alpha}-helix. Most importantly, EpsH contains at its surface a hydrophobic crevice between its variable and conserved {beta}-sheets, wherein a majority of the conserved residues within the EpsH family are clustered. In a tentative model of a T2SS pseudopilus with EpsH at its tip, the conserved crevice faces away from the helix axis. This conserved surface region may be critical for interacting with other proteins from the T2SS machinery.« less

A new finding on the in-vivo crevice corrosion damage in a CoCrMo hip implant.

PubMed

Oskouei, Reza H; Barati, Mohammad Reza; Farhoudi, Hamidreza; Taylor, Mark; Solomon, Lucian Bogdan

2017-10-01

A detailed investigation was performed to characterize the fretting wear and corrosion damage to the neck component of a CoCrMo stem from a metal-on-polyethylene implant retrieved after 99months. The stem was a low-carbon (0.07wt%) wrought Co-28Cr-6Mo alloy with no secondary carbide phases in the matrix (γ-phase). The original design of the neck surface contained an intentionally fabricated knurled profile with a valley-to-peak range of approximately 11μm. Roughness measurements indicated that the tip of the knurled profile was significantly damaged, especially in the distal medial region of the neck, with up to a 22% reduction in the mean peak-to-valley height (R a ) compared to the original profile. As a new finding, the channels between the peaks of the profile created an additional crevice site in the presence of stagnant body fluid within the head-neck taper junction. These channels were observed to contain the most severe corroded areas and surface oxide layers with micro-cracks. SEM/EDS, XRD and XPS evaluations identified the formation of Cr 2 O 3 as a corrosion product. Also, decobaltification was found to occur in these corroded areas. The findings of this work indicate the important role of the knurled profile in inducing additional crevice corrosion. Copyright © 2017 Elsevier B.V. All rights reserved.

Performance of (UNS 8028) production tubing material in sour service environment of Khuff gas formation

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

Al-Maslamani, M.

Khuff gas formation is one of the largest reservoirs of non-associated gas in the world. Recent developments in exploration and production from Khuff gas formation at the Qatar North Field required materials of construction with long periods of production without work over and chemical inhibition. Gas produced contains corrosive constituents such as 1% H{sub 2}S, 4% CO{sub 2} and brine at pressures exceeding 300 barg (CITHP). For operational reasons, two of the 16 wells drilled were needed to work over after 2 years of service and showed evidence of crevice pitting corrosion and thread galling on the Corrosion Resistance Alloymore » (CRA) tubing material. Full inspection and analysis of the problem are addressed in this paper.« less

40 CFR 144.3 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-07-01

... facility” Improved sinkhole means a naturally occurring karst depression or other natural crevice found in... the Administrator under the “appropriate Act and regulations.” Major facility means any UIC “facility...

In situ nano- to microscopic imaging and growth mechanism of electrochemical dissolution (e.g., corrosion) of a confined metal surface

PubMed Central

Merola, C.; Cheng, H.-W.; Schwenzfeier, K.; Kristiansen, K.; Chen, Y.-J.; Dobbs, H. A.; Valtiner, M.

2017-01-01

Reactivity in confinement is central to a wide range of applications and systems, yet it is notoriously difficult to probe reactions in confined spaces in real time. Using a modified electrochemical surface forces apparatus (EC-SFA) on confined metallic surfaces, we observe in situ nano- to microscale dissolution and pit formation (qualitatively similar to previous observation on nonmetallic surfaces, e.g., silica) in well-defined geometries in environments relevant to corrosion processes. We follow “crevice corrosion” processes in real time in different pH-neutral NaCl solutions and applied surface potentials of nickel (vs. Ag|AgCl electrode in solution) for the mica–nickel confined interface of total area ∼0.03 mm2. The initial corrosion proceeds as self-catalyzed pitting, visualized by the sudden appearance of circular pits with uniform diameters of 6–7 μm and depth ∼2–3 nm. At concentrations above 10 mM NaCl, pitting is initiated at the outer rim of the confined zone, while below 10 mM NaCl, pitting is initiated inside the confined zone. We compare statistical analysis of growth kinetics and shape evolution of individual nanoscale deep pits with estimates from macroscopic experiments to study initial pit growth and propagation. Our data and experimental techniques reveal a mechanism that suggests initial corrosion results in formation of an aggressive interfacial electrolyte that rapidly accelerates pitting, similar to crack initiation and propagation within the confined area. These results support a general mechanism for nanoscale material degradation and dissolution (e.g., crevice corrosion) of polycrystalline nonnoble metals, alloys, and inorganic materials within confined interfaces. PMID:28827338

Mapping the membrane-aqueous border for the voltage-sensing domain of a potassium channel.

PubMed

Neale, Edward J; Rong, Honglin; Cockcroft, Christopher J; Sivaprasadarao, Asipu

2007-12-28

Voltage-sensing domains (VSDs) play diverse roles in biology. As integral components, they can detect changes in the membrane potential of a cell and couple these changes to activity of ion channels and enzymes. As independent proteins, homologues of the VSD can function as voltage-dependent proton channels. To sense voltage changes, the positively charged fourth transmembrane segment, S4, must move across the energetically unfavorable hydrophobic core of the bilayer, which presents a barrier to movement of both charged species and protons. To reduce the barrier to S4 movement, it has been suggested that aqueous crevices may penetrate the protein, reducing the extent of total movement. To investigate this hypothesis in a system containing fully functional channels in a native environment with an intact membrane potential, we have determined the contour of the membrane-aqueous border of the VSD of KvAP in Escherichia coli by examining the chemical accessibility of introduced cysteines. The results revealed the contour of the membrane-aqueous border of the VSD in its activated conformation. The water-inaccessible regions of S1 and S2 correspond to the standard width of the membrane bilayer (~28 A), but those of S3 and S4 are considerably shorter (> or = 40%), consistent with aqueous crevices pervading both the extracellular and intracellular ends. One face of S3b and the entire S3a were water-accessible, reducing the water-inaccessible region of S3 to just 10 residues, significantly shorter than for S4. The results suggest a key role for S3 in reducing the distance S4 needs to move to elicit gating.

Corrosion resistance of cast irons and titanium alloys as reference engineered metal barriers for use in basalt geologic storage: a literature assessment

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

Charlot, L.A.; Westerman, R.E.

A survey and assessment of the literature on the corrosion resistance of cast irons and low-alloy titanium are presented. Selected engineering properties of cast iron and titanium are briefly described; however, the corrosion resistance of cast iron and titanium in aqueous solutions or in soils and their use in a basalt repository are emphasized. In evaluating the potential use of cast iron and titanium as structural barrier materials for long-lived nuclear waste packages, it is assumed that titanium has the general corrosion resistance to be used in relatively thin cross sections whereas the cost and availability of cast iron allowsmore » its use even in very thick cross sections. Based on this assumption, the survey showed that: The uniform corrosion of low-alloy titanium in a basalt environment is expected to be extremely low. A linear extrapolation of general corrosion rates with an added corrosion allowance suggests that a 3.2- to 6.4-mm-thick wall may have a life of 1000 yr. Pitting and crevice corrosion are not likely corrosion modes in basalt ground waters. It is also unlikely that stress corrosion cracking (SCC) will occur in the commercially pure (CP) titanium alloy or in palladiumor molybdenum-alloyed titanium materials. Low-alloy cast irons may be used as barrier metals if the environment surrounding the metal keeps the alloy in the passive range. The solubility of the corrosion product and the semipermeable nature of the oxide film allow significant uniform corrosion over long time periods. A linear extrapolation of high-temperature corrosion rates on carbon steels and corrosion rates of cast irons in soils gives an estimated metal penetration of 51 to 64 mm after 1000 yr. A corrosion allowance of 3 to 5 times that suggests that an acceptable cast iron wall may be from 178 to 305 mm thick. Although they cannot be fully assessed, pitting and crevice corrosion should not affect cast iron due to the ground-water chemistry of basalt.« less

How Dangerous Can Localized Corrosion Be? An Experiment that Studies Its Effects.

ERIC Educational Resources Information Center

Celdran, R.; Gonzalo, P.

1988-01-01

Considers three common cases of localized corrosion of metals: pitting, crevice, and stress corrosion. Provides experimental methods for studying all three methods. Includes a discussion of expected results. (ML)

NATURE'S WAY HS

EPA Pesticide Factsheets

Technical product bulletin: aka MICRO CLEAN or POWERCLEAN, this surface washing agent used in oil spill cleanups should be applied full strength to surfaces such as shorelines and beaches, pressure sprayed into cracks/crevices, and scrubbed well.

FINAL ANALYTICAL RESULTS FROM THE EXAMINATION OF CORROSION ON SECTIONS OF CORROSION PROBE REMOVED FROM TANK 241-AN-107 ON 08/10/2006

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

DUNCAN JB; COOKE GA

2007-03-22

Tank Farms Operations removed an electrochemical noise probe from Tank 241-AN-107. In the field, the probe was cut into four sections, wrapped, and placed in a 55-gallon drum, This drum was delivered to the 222-S Laboratory. The 222 S Laboratory unpackaged the sections of the AN-107 electrochemical noise probe and examined the material for evidence of corrosion. Each of the four sections contained three C-ring and three bullet specimens. The specimens were examined for pitting corrosion, crevice corrosion, and stress corrosion cracking. No evidence of stress corrosion cracking was found in the stressed C-ring specimens. Minor pitting was evident onmore » some surfaces. Crevice corrosion was the dominant type of corrosion observed.« less

Colony mapping: A new technique for monitoring crevice-nesting seabirds

USGS Publications Warehouse

Renner, H.M.; Renner, M.; Reynolds, J.H.; Harping, A.M.A.; Jones, I.L.; Irons, D.B.; Byrd, G.V.

2006-01-01

Monitoring populations of auklets and other crevice-nesting seabirds remains problematic, although numerous methods have been attempted since the mid-1960s. Anecdotal evidence suggests several large auklet colonies have recently decreased in both abundance and extent, concurrently with vegetation encroachment and succession. Quantifying changes in the geographical extent of auklet colonies may be a useful alternative to monitoring population size directly. We propose a standardized method for colony mapping using a randomized systematic grid survey with two components: a simple presence/absence survey and an auklet evidence density survey. A quantitative auklet evidence density index was derived from the frequency of droppings and feathers. This new method was used to map the colony on St. George Island in the southeastern Bering Sea and results were compared to previous colony mapping efforts. Auklet presence was detected in 62 of 201 grid cells (each grid cell = 2500 m2) by sampling a randomly placed 16 m2 plot in each cell; estimated colony area = 155 000 m2. The auklet evidence density index varied by two orders of magnitude across the colony and was strongly correlated with means of replicated counts of birds socializing on the colony surface. Quantitatively mapping all large auklet colonies is logistically feasible using this method and would provide an important baseline for monitoring colony status. Regularly monitoring select colonies using this method may be the best means of detecting changes in distribution and population size of crevice-nesting seabirds. ?? The Cooper Ornithological Society 2006.

Corrosion behavior of 2205 duplex stainless steel.

PubMed

Platt, J A; Guzman, A; Zuccari, A; Thornburg, D W; Rhodes, B F; Oshida, Y; Moore, B K

1997-07-01

The corrosion of 2205 duplex stainless steel was compared with that of AISI type 316L stainless steel. The 2205 stainless steel is a potential orthodontic bracket material with low nickel content (4 to 6 wt%), whereas the 316L stainless steel (nickel content: 10 to 14 wt%) is a currently used bracket material. Both stainless steels were subjected to electrochemical and immersion (crevice) corrosion tests in 37 degrees C, 0.9 wt% sodium chloride solution. Electrochemical testing indicates that 2205 has a longer passivation range than 316L. The corrosion rate of 2205 was 0.416 MPY (milli-inch per year), whereas 316L exhibited 0.647 MPY. When 2205 was coupled to 316L with equal surface area ratio, the corrosion rate of 2205 reduced to 0.260 MPY, indicating that 316L stainless steel behaved like a sacrificial anode. When 316L is coupled with NiTi, TMA, or stainless steel arch wire and was subjected to the immersion corrosion test, it was found that 316L suffered from crevice corrosion. On the other hand, 2205 stainless steel did not show any localized crevice corrosion, although the surface of 2205 was covered with corrosion products, formed when coupled to NiTi and stainless steel wires. This study indicates that considering corrosion resistance, 2205 duplex stainless steel is an improved alternative to 316L for orthodontic bracket fabrication when used in conjunction with titanium, its alloys, or stainless steel arch wires.

40 CFR 180.513 - Chlorfenapyr; tolerances for residues.

Code of Federal Regulations, 2011 CFR

2011-07-01

... greater than a 0.5% active ingredient solution for spot crack and crevice use in food/feed handling.... Application excludes any direct application to any food, food packaging, or any food contact surfaces. (v) To...

Tandem mobile robot system

DOEpatents

Buttz, James H.; Shirey, David L.; Hayward, David R.

2003-01-01

A robotic vehicle system for terrain navigation mobility provides a way to climb stairs, cross crevices, and navigate across difficult terrain by coupling two or more mobile robots with a coupling device and controlling the robots cooperatively in tandem.

Maintenance of human adipose derived stem cell (hASC) differentiation capabilities using a 3D culture.

PubMed

Lin, Ching-Yu; Huang, Chi-Hui; Wu, Yuan-Kun; Cheng, Nai-Chen; Yu, Jiashing

2014-07-01

In this study, 3D culture system for human adipose-derived stem cell (hASC) using a BioLevitator as the bioreactor for microcarrier-based cultures was established. During the culturing period, hASCs preferred to grow in crevices between microcarriers and a high viability was maintained even when reaching confluency. Adipogenic or osteogenic differential medium was used to induce hASCs and differential potentials of these cells were compared between 2D and 3D environments via RT-PCR and staining quantifications. CEBP/α gene expression was significant higher in 3D condition at day 21 (P < 0.05). Staining quantification indicates that cells cultured in 3D condition have significant better differentiation potential from day 14 to 21 for both adipogenic and osteogenic lineages (P < 0.01).

33 CFR 159.121 - Sewage processing test.

Code of Federal Regulations, 2010 CFR

2010-07-01

... crevices that could come in contact with a person using the device or servicing the device in accordance..., the device must be tilted to the maximum angles specified by the manufacturer under §§ 159.55 and 159...

Friction enhancement in concertina locomotion of snakes

PubMed Central

Marvi, Hamidreza; Hu, David L.

2012-01-01

Narrow crevices are challenging terrain for most organisms and biomimetic robots. Snakes move through crevices using sequential folding and unfolding of their bodies in the manner of an accordion or concertina. In this combined experimental and theoretical investigation, we elucidate this effective means of moving through channels. We measure the frictional properties of corn snakes, their body kinematics and the transverse forces they apply to channels of varying width and inclination. To climb channels inclined at 60°, we find snakes use a combination of ingenious friction-enhancing techniques, including digging their ventral scales to double their frictional coefficient and pushing channel walls transversely with up to nine times body weight. Theoretical modelling of a one-dimensional n-linked crawler is used to calculate the transverse force factor of safety: we find snakes push up to four times more than required to prevent sliding backwards, presumably trading metabolic energy for an assurance of wall stability. PMID:22728386

Corrosion of simulated bearing components of three bearing steels in the presence of chloride-contaminated lubricant

NASA Technical Reports Server (NTRS)

Parker, R. J.; Bamberger, E. N.; Nahm, A. H.

1983-01-01

Corrosion tests were run with AISI 52100, AISI M-50 and AMS 5794 under conditions that simulate the crevice corrosion found in aircraft ball and roller bearings rejected at overhaul for corrosion. Test specimens were fabricated that simulated the contacts of balls or rollers and the raceways. Corrosion cells were assembled in the presence of a lubricant contaminated with water and chloride ions. The cell was then thermally cycled between 339 K (150 F) and 276 K (37 F). The corrosion observed after 14 cycles was that of crevice and pitting corrosion typically found in aircraft bearings. AMS 5749 showed a very slight amount of corrosion. No appreciable differences were noted between AISI 52100 and AISI M-50, but both showed much greater corrosion than AMS 5749. The corrosion pits observed in AISI M-50 appeared to be fewer in number but generally deeper and larger than in AISI 52100.

Friction enhancement in concertina locomotion of snakes.

PubMed

Marvi, Hamidreza; Hu, David L

2012-11-07

Narrow crevices are challenging terrain for most organisms and biomimetic robots. Snakes move through crevices using sequential folding and unfolding of their bodies in the manner of an accordion or concertina. In this combined experimental and theoretical investigation, we elucidate this effective means of moving through channels. We measure the frictional properties of corn snakes, their body kinematics and the transverse forces they apply to channels of varying width and inclination. To climb channels inclined at 60°, we find snakes use a combination of ingenious friction-enhancing techniques, including digging their ventral scales to double their frictional coefficient and pushing channel walls transversely with up to nine times body weight. Theoretical modelling of a one-dimensional n-linked crawler is used to calculate the transverse force factor of safety: we find snakes push up to four times more than required to prevent sliding backwards, presumably trading metabolic energy for an assurance of wall stability.

Halogen-Enriched Fragment Libraries as Leads for Drug Rescue of Mutant p53

PubMed Central

2012-01-01

The destabilizing p53 cancer mutation Y220C creates a druggable surface crevice. We developed a strategy exploiting halogen bonding for lead discovery to stabilize the mutant with small molecules. We designed halogen-enriched fragment libraries (HEFLibs) as starting points to complement classical approaches. From screening of HEFLibs and subsequent structure-guided design, we developed substituted 2-(aminomethyl)-4-ethynyl-6-iodophenols as p53-Y220C stabilizers. Crystal structures of their complexes highlight two key features: (i) a central scaffold with a robust binding mode anchored by halogen bonding of an iodine with a main-chain carbonyl and (ii) an acetylene linker, enabling the targeting of an additional subsite in the crevice. The best binders showed induction of apoptosis in a human cancer cell line with homozygous Y220C mutation. Our structural and biophysical data suggest a more widespread applicability of HEFLibs in drug discovery. PMID:22439615

Rail assembly for use in a radioactive environment

DOEpatents

Watts, Ralph E.

1989-01-01

An improved rail assembly and method of construction thereof is disclosed herein that is particularly adapted for use with a crane trolley in a hot cell environment which is exposed to airborne and liquidborne radioactive contaminants. The rail assembly is generally comprised of a support wall having an elongated, rail-housing recess having a floor, side wall and ceiling. The floor of the recess is defined at least in part by the load-bearing surface of a rail, and is substantially flat, level and crevice-free to facilitate the drainage of liquids out of the recess. The ceiling of the recess overhangs and thereby captures trolley wheels within the recess to prevent them from becoming dislodged from the recess during a seismic disturbance. Finally, the interior of the recess includes a power track having a slot for receiving a sliding electrical connector from the crane trolley. The power track is mounted in an upper corner of the recess with its connector-receiving groove oriented downwardly to facilitate the drainage of liquidborne contaminants and to discourage the collection of airborne contaminants within the track.

Physiological Intracellular Crowdedness is Defined by the Perimeter-to-Area Ratio of Sub-Cellular Compartments

PubMed Central

Hiroi, Noriko; Okuhara, Takahiro; Kubojima, Takeshi; Iba, Keisuke; Tabira, Akito; Yamashita, Shuji; Okada, Yasunori; Kobayashi, Tetsuya J.; Funahashi, Akira

2012-01-01

The intracellular environment is known to be a crowded and inhomogeneous space. Such an in vivo environment differs from a well-diluted, homogeneous environment for biochemical reactions. However, the effects of both crowdedness and the inhomogeneity of environment on the behavior of a mobile particle have not yet been investigated sufficiently. As described in this paper, we constructed artificial reaction spaces with fractal models, which are assumed to be non-reactive solid obstacles in a reaction space with crevices that function as operating ranges for mobile particles threading the space. Because of the homogeneity of the structures of artificial reaction spaces, the models succeeded in reproducing the physiological fractal dimension of solid structures with a smaller number of non-reactive obstacles than in the physiological condition. This incomplete compatibility was mitigated when we chose a suitable condition of a perimeter-to-area ratio of the operating range to our model. Our results also show that a simulation space is partitioned into convenient reaction compartments as an in vivo environment with the exact amount of solid structures estimated from TEM images. The characteristics of these compartments engender larger mean square displacement of a mobile particle than that of particles in smaller compartments. Subsequently, the particles start to show confined particle-like behavior. These results are compatible with our previously presented results, which predicted that a physiological environment would produce quick response and slow exhaustion reactions. PMID:22936917

Application of ANS fluorescent probes to identify hydrophobic sites on the surface of DREAM.

PubMed

Gonzalez, Walter G; Miksovska, Jaroslava

2014-09-01

DREAM (calsenilin or KChIP-3) is a calcium sensor involved in regulation of diverse physiological processes by interactions with multiple intracellular partners including DNA, Kv4 channels, and presenilin, however the detailed mechanism of the recognition of the intracellular partners remains unclear. To identify the surface hydrophobic surfaces on apo and Ca(2+)DREAM as a possible interaction sites for target proteins and/or specific regulators of DREAM function the binding interactions of 1,8-ANS and 2,6-ANS with DREAM were characterized by fluorescence and docking studies. Emission intensity of ANS-DREAM complexes increases upon Ca(2+) association which is consistent with an overall decrease in surface polarity. The dissociation constants for ANS binding to apoDREAM and Ca(2+)DREAM were determined to be 195±20μM and 62±4μM, respectively. Fluorescence lifetime measurements indicate that two ANS molecules bind in two independent binding sites on DREAM monomer. One site is near the exiting helix of EF-4 and the second site is located in the hydrophobic crevice between EF-3 and EF-4. 1,8-ANS displacement studies using arachidonic acid demonstrate that the hydrophobic crevice between EF-3 and EF-4 serves as a binding site for fatty acids that modulate functional properties of Kv4 channel:KChIP complexes. Thus, the C-terminal hydrophobic crevice may be involved in DREAM interactions with small hydrophobic ligands as well as other intracellular proteins. Copyright © 2014 Elsevier B.V. All rights reserved.

Potentiodynamic polarization study of the in vitro corrosion behavior of 3 high-palladium alloys and a gold-palladium alloy in 5 media.

PubMed

Sun, Desheng; Monaghan, Peter; Brantley, William A; Johnston, William M

2002-01-01

Corrosion of cast alloy restorations may lead to their failure or adversely affect their biocompatibility. Although some documentation of the corrosion behavior of the high-palladium dental alloys exists, questions remain about their corrosion resistance and mechanisms. This study compared the in vitro corrosion characteristics of 3 high-palladium alloys and 1 gold-palladium alloy in simulated body fluid and oral environments. Two Pd-Cu-Ga alloys and 1 Pd-Ga alloy were selected; an Au-Pd alloy served as the control. The corrosion behavior for the as-cast and simulated porcelain-firing (heat-treated) conditions of each alloy (N = 5) was evaluated in 0.9% NaCl, 0.09% NaCl, and Fusayama solutions. Heat-treated specimens of each alloy (N = 5) were also tested in N(2)-deaerated 0.09% NaCl and Fusayama solutions (pH 4). After immersion in the electrolyte for 24 hours, the open-circuit potential (OCP) was measured, and linear polarization was performed from -20 mV to +20 mV (vs. OCP) at a scanning rate of 0.125 mV/s. Cyclic polarization was performed from -300 mV to +1000 mV and back to -300 mV (vs. OCP) at a scanning rate of 1 mV/s. Data were evaluated with analysis of variance and the Ryan-Einot-Gabriel-Welsch multiple-range test (alpha=.05). The OCP of each alloy varied with the condition (as-cast or heat-treated) and electrolyte used. Corrosion resistance was similar for the 4 alloys tested. For cyclic polarization, all alloys showed active-passive or spontaneous passive behavior in nearly all electrolytes. During some reverse scans, the 3 high-palladium alloys displayed 3 or 5 anodic peaks. No positive hysteresis was observed for any of the alloy/electrolyte combinations evaluated. The corrosion resistances of the 3 high-palladium alloys in simulated body fluid and oral environments were comparable to that of the gold-palladium alloy. The similar corrosion resistance for the 3 high-palladium alloys was attributed to their high noble metal content and theorized stable structure at the submicron level. Selective corrosion of different phases and elements, surface enrichment of palladium, and adsorption of species are possible corrosion mechanisms. The cyclic polarization results suggest that none of the 4 alloys would be prone to pitting or crevice corrosion under in vivo conditions, but crevice conditions should nonetheless be avoided for these alloys in the oral environment.

Investigation of passive films on nickel Alloy 690 in lead-containing environments

NASA Astrophysics Data System (ADS)

Peng, B.; Lu, B. T.; Luo, J. L.; Lu, Y. C.; Ma, H. Y.

2008-09-01

Passive films formed on Alloy UNS N06690 were investigated in simulated crevice chemistries. It was found the role of lead in corrosion processes is strongly dependent on the pH value of the testing solutions. At pH 1.5 the effect of lead is narrowly noticeable; while at pH 12.7, lead has a significant influence on the electrochemical performance of alloy UNS N06690. The lead alters the surface morphologies at both pH and account for higher hydroxide content in the surface film at pH 12.7. The lead incorporation hinders the formation of spinel oxides during the passivation in alkaline solution. Nanoindentation tests indicate a significant lead-induced degradation in the mechanical properties of passive films. The passivation degradation is attributed to detrimental effects of lead via interrupting the dehydration process and hindering the formation of protective layers on the alloy surface.

MOVEMENT AND DEPOSITION OF PESTICIDES WITHIN RESIDENCES AFTER INTERIOR AND EXTERIOR APPLICATIONS

EPA Science Inventory

In a study begun in 1999, the Environmental Protection Agency (EPA) investigated the temporal and spatial distributions of pesticides applied by homeowners and commercial applicators for indoor crack and crevice and exterior perimeter treatments. In each participating househol...

Effects of Corrosion and Fatigue on the Load-Carrying Capacity of Structural and Reinforcing Steel

DOT National Transportation Integrated Search

1994-03-01

Pitting and crevice corrosion have profound effects on the fatigue life of structural and reinforcing steels used in bridge construction. Stress concentration factors were measured on actual corroded plates with strain gage instrumentation. Using cor...

Inhibition of dog and human gastric lipases by enantiomeric phosphonate inhibitors: a structure-activity study.

PubMed

Miled, Nabil; Roussel, Alain; Bussetta, Cécile; Berti-Dupuis, Liliane; Rivière, Mireille; Buono, Gérard; Verger, Robert; Cambillau, Christian; Canaan, Stéphane

2003-10-14

The crystal structures of gastric lipases in the apo form [Roussel, A., et al. (1999) J. Biol. Chem. 274, 16995-17002] or in complex with the (R(P))-undecyl butyl phosphonate [C(11)Y(4)(+)] [Roussel, A., et al. (2002) J. Biol. Chem. 277, 2266-2274] have improved our understanding of the structure-activity relationships of acid lipases. In this report, we have performed a kinetic study with dog and human gastric lipases (DGL and HGL, respectively) using several phosphonate inhibitors by varying the absolute configuration of the phosphorus atom and the chain length of the alkyl/alkoxy substituents. Using the two previously determined structures and that of a new crystal structure obtained with the other (S(P))-phosphonate enantiomer [C(11)Y(4)(-)], we constructed models of phosphonate inhibitors fitting into the active site crevices of DGL and HGL. All inhibitors with a chain length of fewer than 12 carbon atoms were found to be completely buried in the catalytic crevice, whereas longer alkyl/alkoxy chains were found to point out of the cavity. The main stereospecific determinant explaining the stronger inhibition of the S(P) enantiomers is the presence of a hydrogen bond involving the catalytic histidine as found in the DGL-C(11)Y(4)(-) complex. On the basis of these results, we have built a model of the first tetrahedral intermediate corresponding to the tristearoyl-lipase complex. The triglyceride molecule completely fills the active site crevice of DGL, in contrast with what is observed with other lipases such as pancreatic lipases which have a shallower and narrower active site. For substrate hydrolysis, the supply of water molecules to the active site might be achieved through a lateral channel identified in the protein core.

General and crevice corrosion study of the in-wall shielding materials for ITER vacuum vessel

NASA Astrophysics Data System (ADS)

Joshi, K. S.; Pathak, H. A.; Dayal, R. K.; Bafna, V. K.; Kimihiro, Ioki; Barabash, V.

2012-11-01

Vacuum vessel In-Wall Shield (IWS) will be inserted between the inner and outer shells of the ITER vacuum vessel. The behaviour of IWS in the vacuum vessel especially concerning the susceptibility to crevice of shielding block assemblies could cause rapid and extensive corrosion attacks. Even galvanic corrosion may be due to different metals in same electrolyte. IWS blocks are not accessible until life of the machine after closing of vacuum vessel. Hence, it is necessary to study the susceptibility of IWS materials to general corrosion and crevice corrosion under operations of ITER vacuum vessel. Corrosion properties of IWS materials were studied by using (i) Immersion technique and (ii) Electro-chemical Polarization techniques. All the sample materials were subjected to a series of examinations before and after immersion test, like Loss/Gain weight measurement, SEM analysis, and Optical stereo microscopy, measurement of surface profile and hardness of materials. After immersion test, SS 304B4 and SS 304B7 showed slight weight gain which indicate oxide layer formation on the surface of coupons. The SS 430 material showed negligible weight loss which indicates mild general corrosion effect. On visual observation with SEM and Metallography, all material showed pitting corrosion attack. All sample materials were subjected to series of measurements like Open Circuit potential, Cyclic polarization, Pitting potential, protection potential, Critical anodic current and SEM examination. All materials show pitting loop in OC2 operating condition. However, its absence in OC1 operating condition clearly indicates the activity of chloride ion to penetrate oxide layer on the sample surface, at higher temperature. The critical pitting temperature of all samples remains between 100° and 200°C.

40 CFR 180.530 - 2,2-Dimethyl-1,3-benzodioxol-4-ol methylcarbamate; tolerances for residues.

Code of Federal Regulations, 2010 CFR

2010-07-01

... used in spot and/or crack and crevice treatments in animal feed handling establishments, including feed... insecticide 2,2-dimethyl-1,3-benzodioxol-4-yl methylcarbamate may be safely used in spot and/or crack and...

Elastomer-induced crevice corrosion and stress corrosion cracking of stainless steel heat exchanger plates in sour amine service

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

Hay, M.G.; Baron, J.J.; Moffat, T.A.

1996-08-01

Types S31600 and S31254 stainless steel heat exchanger plates have suffered crevice corrosion and stress corrosion cracking under gaskets in rich amine service in a sour gas plant. The gasket material, ethylene-propylene-diene monomer (EPDM), has been used successfully for many years at other sour gas plants. Laboratory testing has duplicated the corrosion observed and shown that the mechanism is synergistic sulfide-halide attack. The use of a bromine plus chlorine-activated curing system for the EPDM rubber gaskets provided the necessary halides. Laboratory testing identified some nickel-based superalloys which were resistant to this corrosion and also demonstrated that essentially halogen-free, peroxide-cured EPDMmore » gaskets do not cause attack of S31600 or S31254. The heat exchanger packs were replaced with S31600 plates and peroxide-cured EPDM gaskets having a specified total halogen concentration of 200 ppm maximum. Field operating experience has been excellent.« less

Applying Uncertainty Analysis to a Risk Assessment for the Pesticide Permethrin

EPA Science Inventory

We discuss the application of methods of uncertainty analysis from our previous poster to the problem of a risk assessment for exposure to the food-use pesticide permethrin resulting from residential pesticide crack and crevice application. Exposures are simulated by the SHEDS (S...

Using airborne laser altimetry to estimate Sabellaria alveolata (Polychaeta: Sabellariidae) reefs volume in tidal flat environments

NASA Astrophysics Data System (ADS)

Noernberg, Mauricio Almeida; Fournier, Jérôme; Dubois, Stanislas; Populus, Jacques

2010-12-01

This study has exploited aerial photographs and LiDAR digital elevation model to quantify intertidal complex landforms volume. A first volume estimation of the main sabellariid polychaete reef complex of the Bay of Mont-Saint-Michel - France is presented. The Sabellaria alveolata is an engineering species that heavily modifies its environment. This gregarious tube-building annelid forms dense and solid reefs of bioclastic coarse sand which can reach several km 2. Since 1970 a very strong decline of reefs has been observed. The authorities have curbed fishing activities without any noticeable changes in reef health status. The S. alveolata reef volume is estimated to be 132 048 m 3 (96 301 m 3 for Sainte-Anne reef and 35 747 m 3 for Champeaux reef). Further LiDAR data surveys will be needed to be able to understand and quantify the accretion/erosion processes in play in the reef dynamic. Because of the internal variability of topographic complexity of the reef, characterized by crevices, cracks, and holes rather than whole blocks, further studies are needed to calculate more accurately the volume of the reef.

76 FR 31471 - Ethylene Glycol; Exemption From the Requirement of a Tolerance

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-01

... production (NAICS code 112). Food manufacturing (NAICS code 311). Pesticide manufacturing (NAICS code 32532..., submitted a petition to EPA under the Federal Food, Drug, and Cosmetic Act (FFDCA), requesting an... residual, and crack and crevice sprays in and around food and nonfood areas of residential and...

Magnetic force micropiston: an integrated force/microfluidic device for the application of compressive forces in a confined environment.

PubMed

Fisher, J K; Kleckner, N

2014-02-01

Cellular biology takes place inside confining spaces. For example, bacteria grow in crevices, red blood cells squeeze through capillaries, and chromosomes replicate inside the nucleus. Frequently, the extent of this confinement varies. Bacteria grow longer and divide, red blood cells move through smaller and smaller passages as they travel to capillary beds, and replication doubles the amount of DNA inside the nucleus. This increase in confinement, either due to a decrease in the available space or an increase in the amount of material contained in a constant volume, has the potential to squeeze and stress objects in ways that may lead to changes in morphology, dynamics, and ultimately biological function. Here, we describe a device developed to probe the interplay between confinement and the mechanical properties of cells and cellular structures, and forces that arise due to changes in a structure's state. In this system, the manipulation of a magnetic bead exerts a compressive force upon a target contained in the confining space of a microfluidic channel. This magnetic force microfluidic piston is constructed in such a way that we can measure (a) target compliance and changes in compliance as induced by changes in buffer, extract, or biochemical composition, (b) target expansion force generated by changes in the same parameters, and (c) the effects of compression stress on a target's structure and function. Beyond these issues, our system has general applicability to a variety of questions requiring the combination of mechanical forces, confinement, and optical imaging.

Magnetic force micropiston: An integrated force/microfluidic device for the application of compressive forces in a confined environment

NASA Astrophysics Data System (ADS)

Fisher, J. K.; Kleckner, N.

2014-02-01

Cellular biology takes place inside confining spaces. For example, bacteria grow in crevices, red blood cells squeeze through capillaries, and chromosomes replicate inside the nucleus. Frequently, the extent of this confinement varies. Bacteria grow longer and divide, red blood cells move through smaller and smaller passages as they travel to capillary beds, and replication doubles the amount of DNA inside the nucleus. This increase in confinement, either due to a decrease in the available space or an increase in the amount of material contained in a constant volume, has the potential to squeeze and stress objects in ways that may lead to changes in morphology, dynamics, and ultimately biological function. Here, we describe a device developed to probe the interplay between confinement and the mechanical properties of cells and cellular structures, and forces that arise due to changes in a structure's state. In this system, the manipulation of a magnetic bead exerts a compressive force upon a target contained in the confining space of a microfluidic channel. This magnetic force microfluidic piston is constructed in such a way that we can measure (a) target compliance and changes in compliance as induced by changes in buffer, extract, or biochemical composition, (b) target expansion force generated by changes in the same parameters, and (c) the effects of compression stress on a target's structure and function. Beyond these issues, our system has general applicability to a variety of questions requiring the combination of mechanical forces, confinement, and optical imaging.

83. Photographic copy of historic photo, December 16, 1929 (original ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

83. Photographic copy of historic photo, December 16, 1929 (original print filed in Record Group 115, National Archives, Washington, D.C.). OWYHEE DAM-LOOKING DOWNSTREAM FROM UPPER COFFERDAM (POINT #15) SHOWING CREVICE AND KEYWAY CUTOFF; ALSO CABLEWAY CONTROL HOUSE AND ENTRANCE ADIT. - Owyhee Dam, Across Owyhee River, Nyssa, Malheur County, OR

THE DISTRIBUTION OF CHLORPYRIFOS FOLLOWING A CRACK AND CREVICE TYPE APPLICAITON IN THE U.S. EPA INDOOR AIR QUALITY (IAQ) TEST HOUSE

EPA Science Inventory

Pesticides found in homes may result from indoor applications to control household pests or by translocation from outdoor sources. Pesticides disperse according to their physical properties and other factors such as human activity, residential air exchange, temperature and humi...

THE SPATIAL AND TEMPORAL DISTRIBUTION OF CHLORPYRIFOS IN THE U.S. EPA INDOOR AIR QUALITY (IAQ) TEST HOUSE FOLLOWING CRACK AND CREVICE TYPE APPLICATIONS

EPA Science Inventory

Pesticides found in homes may result from indoor applications to control household pests or by translocation from outdoor sources. Pesticides disperse according to their physical properties and other factors such as human activity, air exchange, temperature and humidity. Insect...

Effect of temperature on the passivation behavior of steel rebar

NASA Astrophysics Data System (ADS)

Chen, Shan-meng; Cao, Bei; Wu, Yin-shun; Ma, Ke

2014-05-01

Steel rebar normally forms an oxide or rusty skin before it is embedded into concrete and the passivation properties of this skin will be heavily influenced by temperature. To study the effect of temperature on the passivation properties of steel rebar under different surface conditions, we conducted scanning electron microscopy (SEM) observations and electrochemical measurements, such as measurements of the free corrosion potential and polarization curves of HPB235 steel rebar. These measurements identified three kinds of surfaces: polished, oxide skin, and rusty skin. Our results show that the passivation properties of all the surface types decrease with the increase of temperature. Temperature has the greatest effect on the rusty-skin rebar and least effect on the polished steel rebar, because of cracks and crevices on the mill scale on the steel rebar's surface. The rusty-skin rebar exhibits the highest corrosion rate because crevice corrosion can accelerate the corrosion of the steel rebar, particularly at high temperature. The results also indicate that the threshold temperatures of passivation for the oxide-skin rebar and the rusty-skin rebar are 37°C and 20°C, respectively.

Effect of pH on Structural Changes in Perch Hemoglobin that Can Alter Redox Stability and Heme Affinity

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

Richards, Mark P.; Aranda, IV, Roman; He, Cai

2010-01-07

pH can be manipulated to alter the oxidative stability of fish-based foods during storage. X-ray diffraction was used to investigate the ability of reduced pH to cause structural changes in fish hemoglobins that lead to enhanced oxidative degradation. Decreasing pH from 8.0 to 6.3 and 5.7 created a large channel for solvent entry into the heme crevice of perch hemoglobin beta chains. The proton-induced opening of this channel occurred between site CD3 and the heme-6-propionate. Solvent entry into the heme crevice can enhance metHb formation and hemin loss, processes that accelerate lipid oxidation. Reduced pH also decreased the distance betweenmore » Ile at E11 in one of the alpha chains and the ligand above the heme iron atom. This sterically displaces O{sub 2} and protonated O{sub 2} which increases metHb formation. These studies demonstrate that pH reduction causes structural changes in perch hemoglobin which increase oxidative degradation of the heme pigment.« less

Electrostatic field of the large fragment of Escherichia coli DNA polymerase I.

PubMed

Warwicker, J; Ollis, D; Richards, F M; Steitz, T A

1985-12-05

The electrostatic field of the large fragment of Escherichia coli DNA polymerase I (Klenow fragment) has been calculated by the finite difference procedure on a 2 A grid. The potential field is substantially negative at physiological pH (reflecting the net negative charge at this pH). The largest regions of positive potential are in the deep crevice of the C-terminal domain, which is the proposed binding site for the DNA substrate. Within the crevice, the electrostatic potential has a partly helical form. If the DNA is positioned to fulfil stereochemical requirements, then the positive potential generally follows the major groove and (to a lesser extent) the negative potential is in the minor groove. Such an arrangement could stabilize DNA configurations related by screw symmetry. The histidine residues of the Klenow fragment give the positive field of the groove a sensitivity to relatively small pH changes around neutrality. We suggest that the histidine residues could change their ionization states in response to DNA binding, and that this effect could contribute to the protein-DNA binding energy.

Electrochemical Testing of Ni-Cr-Mo-Gd Alloys

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

T. E. Lister; R. E. Mizia; H. Tian

2005-10-01

The waste package site recommendation design specified a boron-containing stainless steel, Neutronit 976/978, for fabrication of the internal baskets that will be used as a corrosion-resistant neutron-absorbing material. Recent corrosion test results gave higher-than-expected corrosion rates for this material. The material callout for these components has been changed to a Ni-Cr-Mo-Gd alloy (ASTM-B 932-04, UNS N06464) that is being developed at the Idaho National Laboratory. This report discusses the results of initial corrosion testing of this material in simulated in-package environments that could contact the fuel baskets after breach of the waste package outer barrier. The corrosion test matrix wasmore » executed using the potentiodynamic and potentiostatic electrochemical test techniques. The alloy performance shows low rates of general corrosion after initial removal of a gadolinium-rich second phase that intersects the surface. The high halide-containing test solutions exhibited greater tendencies toward initiation of crevice corrosion.« less

Classification of acoustic emission signals using wavelets and Random Forests : Application to localized corrosion

NASA Astrophysics Data System (ADS)

Morizet, N.; Godin, N.; Tang, J.; Maillet, E.; Fregonese, M.; Normand, B.

2016-03-01

This paper aims to propose a novel approach to classify acoustic emission (AE) signals deriving from corrosion experiments, even if embedded into a noisy environment. To validate this new methodology, synthetic data are first used throughout an in-depth analysis, comparing Random Forests (RF) to the k-Nearest Neighbor (k-NN) algorithm. Moreover, a new evaluation tool called the alter-class matrix (ACM) is introduced to simulate different degrees of uncertainty on labeled data for supervised classification. Then, tests on real cases involving noise and crevice corrosion are conducted, by preprocessing the waveforms including wavelet denoising and extracting a rich set of features as input of the RF algorithm. To this end, a software called RF-CAM has been developed. Results show that this approach is very efficient on ground truth data and is also very promising on real data, especially for its reliability, performance and speed, which are serious criteria for the chemical industry.

Durable bonds at the adhesive/dentin interface: an impossible mission or simply a moving target?

PubMed Central

SPENCER, Paulette; Jonggu PARK, Qiang YE; MISRA, Anil; BOHATY, Brenda S.; SINGH, Viraj; PARTHASARATHY, Ranga; SENE, Fábio; de Paiva GONÇALVES, Sérgio Eduardo; LAURENCE, Jennifer

2013-01-01

Composite restorations have higher failure rates, more recurrent caries and increased frequency of replacement as compared to dental amalgam. Penetration of bacterial enzymes, oral fluids, and bacteria into the crevices between the tooth and composite undermines the restoration and leads to recurrent decay and failure. The gingival margin of composite restora tions is particularly vulnerable to decay and at this margin, the adhesive and its seal to dentin provides the primary barrier between the prepared tooth and the environment. The intent of this article is to examine physico-chemical factors that affect the integrity and durability of the adhesive/dentin interfacial bond; and to explore how these factors act synergistically with mechanical forces to undermine the composite restoration. The article will examine the various avenues that have been pursued to address these problems and it will explore how alterations in material chemistry could address the detrimental impact of physico-chemical stresses on the bond formed at the adhesive/dentin interface. PMID:24855586

Dynamics of the His79-heme alkaline transition of yeast iso-1-cytochrome c probed by conformationally gated electron transfer with Co(II)bis(terpyridine).

PubMed

Cherney, Melisa M; Junior, Carolyn C; Bergquist, Bryan B; Bowler, Bruce E

2013-08-28

Alkaline conformers of cytochrome c may be involved in both its electron transport and apoptotic functions. We use cobalt(II)bis(terpyridine), Co(terpy)2(2+), as a reagent for conformationally gated electron-transfer (gated ET) experiments to study the alkaline conformational transition of K79H variants of yeast iso-1-cytochrome c expressed in Escherichia coli , WT*K79H, with alanine at position 72 and Saccharomyces cerevisiae , yK79H, with trimethyllysine (Tml) at position 72. Co(terpy)2(2+) is well-suited to the 100 ms to 1 s time scale of the His79-mediated alkaline conformational transition of these variants. Reduction of the His79-heme alkaline conformer by Co(terpy)2(2+) occurs primarily by gated ET, which involves conversion to the native state followed by reduction, with a small fraction of the His79-heme alkaline conformer directly reduced by Co(terpy)2(2+). The gated ET experiments show that the mechanism of formation of the His79-heme alkaline conformer involves only two ionizable groups. In previous work, we showed that the mechanism of the His73-mediated alkaline conformational transition requires three ionizable groups. Thus, the mechanism of heme crevice opening depends upon the position of the ligand mediating the process. The microscopic rate constants provided by gated ET studies show that mutation of Tml72 (yK79H variant) in the heme crevice loop to Ala72 (WT*K79H variant) affects the dynamics of heme crevice opening through a small destabilization of both the native conformer and the transition state relative to the His79-heme alkaline conformer. Previous pH jump data had indicated that the Tml72→Ala mutation primarily stabilized the transition state for the His79-mediated alkaline conformational transition.

Enhancement of juvenile Caribbean spiny lobsters: an evaluation of changes in multiple response variables with the addition of large artificial shelters.

PubMed

Briones-Fourzán, Patricia; Lozano-Alvarez, Enrique; Negrete-Soto, Fernando; Barradas-Ortiz, Cecilia

2007-03-01

Shortage of natural crevice shelters may produce population bottlenecks in juvenile Caribbean spiny lobsters (Panulirus argus), a socially gregarious species. We conducted a field experiment to test enhancement of a local population of juvenile P. argus with the addition of artificial shelters ("casitas") that mimic large crevices (1.1 m(2) in surface area and 3.8 cm in height). Changes in density and biomass of juvenile lobsters 15-50 mm carapace length (CL) were assessed with a multiple before-after control-impact (MBACI) analysis. Separate analyses were also conducted on small (15-35 mm CL) and large (35.1-50 mm CL) juveniles to assess size-related effects. First, we carried out 13 lobster surveys on nine fixed 1-ha sites over a shallow reef lagoon ("before" period). Then, we deployed ten casitas in each of five sites and left four sites as controls, and conducted 22 further surveys ("after" period). Deployment of casitas resulted in a sixfold increase in juvenile density (76% contributed by small and 24% by large juveniles) and a sevenfold increase in biomass (40 and 60%, respectively). Capture-recapture results revealed that enhancement was achieved not by promoting individual growth but by increasing survival, persistence, and foraging ranges of small and large juveniles. Casitas both mitigated shortage of natural shelter and increased sociality, allowing for cohabitation of smaller, more vulnerable juveniles with larger conspecifics that have greater defensive abilities. Casitas may help enhance local populations of juvenile P. argus in Caribbean seagrass habitats, typically poor in natural crevice shelters. The use of MBACI and the simultaneous assessment of multiple interrelated response variables may be a powerful analytical approach to test shelter limitation in other species and to examine the function of structural habitat in other systems.

Structure–function characterization of three human antibodies targeting the vaccinia virus adhesion molecule D8

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

Matho, Michael H.; Schlossman, Andrew; Gilchuk, Iuliia M.

Vaccinia virus (VACV) envelope protein D8 is one of three glycosaminoglycan adhesion molecules and binds to the linear polysaccharide chondroitin sulfate (CS). D8 is also a target for neutralizing antibody responses that are elicited by the smallpox vaccine, which has enabled the first eradication of a human viral pathogen and is a useful model for studying antibody responses. However, to date, VACV epitopes targeted by human antibodies have not been characterized at atomic resolution. Here in this paper, we characterized the binding properties of several human anti-D8 antibodies and determined the crystal structures of three VACV-mAb variants, VACV-66, VACV-138, andmore » VACV-304, separately bound to D8. Although all these antibodies bound D8 with high affinity and were moderately neutralizing in the presence of complement, VACV-138 and VACV-304 also fully blocked D8 binding to CS-A, the low affinity ligand for D8. VACV-138 also abrogated D8 binding to the high-affinity ligand CS-E, but we observed residual CS-E binding was observed in the presence of VACV-304. Analysis of the VACV-138– and VACV-304–binding sites along the CS-binding crevice of D8, combined with different efficiencies of blocking D8 adhesion to CS-A and CS-E allowed us to propose that D8 has a high- and low-affinity CS-binding region within its central crevice. The crevice is amenable to protein engineering to further enhance both specificity and affinity of binding to CS-E. Finally, a wild-type D8 tetramer specifically bound to structures within the developing glomeruli of the kidney, which express CS-E. We propose that through structure-based protein engineering, an improved D8 tetramer could be used as a potential diagnostic tool to detect expression of CS-E, which is a possible biomarker for ovarian cancer.« less

Structure–function characterization of three human antibodies targeting the vaccinia virus adhesion molecule D8

DOE PAGES

Matho, Michael H.; Schlossman, Andrew; Gilchuk, Iuliia M.; ...

2017-11-09

Vaccinia virus (VACV) envelope protein D8 is one of three glycosaminoglycan adhesion molecules and binds to the linear polysaccharide chondroitin sulfate (CS). D8 is also a target for neutralizing antibody responses that are elicited by the smallpox vaccine, which has enabled the first eradication of a human viral pathogen and is a useful model for studying antibody responses. However, to date, VACV epitopes targeted by human antibodies have not been characterized at atomic resolution. Here in this paper, we characterized the binding properties of several human anti-D8 antibodies and determined the crystal structures of three VACV-mAb variants, VACV-66, VACV-138, andmore » VACV-304, separately bound to D8. Although all these antibodies bound D8 with high affinity and were moderately neutralizing in the presence of complement, VACV-138 and VACV-304 also fully blocked D8 binding to CS-A, the low affinity ligand for D8. VACV-138 also abrogated D8 binding to the high-affinity ligand CS-E, but we observed residual CS-E binding was observed in the presence of VACV-304. Analysis of the VACV-138– and VACV-304–binding sites along the CS-binding crevice of D8, combined with different efficiencies of blocking D8 adhesion to CS-A and CS-E allowed us to propose that D8 has a high- and low-affinity CS-binding region within its central crevice. The crevice is amenable to protein engineering to further enhance both specificity and affinity of binding to CS-E. Finally, a wild-type D8 tetramer specifically bound to structures within the developing glomeruli of the kidney, which express CS-E. We propose that through structure-based protein engineering, an improved D8 tetramer could be used as a potential diagnostic tool to detect expression of CS-E, which is a possible biomarker for ovarian cancer.« less

Dynamics of the His79-heme Alkaline Transition of Yeast Iso-1-cytochrome c Probed by Conformationally-gated Electron Transfer with Co(II)bis(terpyridine)†

PubMed Central

Cherney, Melisa M.; Junior, Carolyn C.; Bergquist, Bryan B.; Bowler, Bruce E.

2013-01-01

Alkaline conformers of cytochrome c may be involved in both its electron transport and apoptotic functions. We use cobalt(II)bis(terpyridine), Co(terpy)22+, as a reagent for conformationally-gated electron transfer (gated ET) experiments to study the alkaline conformational transition of K79H variants of yeast iso-1-cytochrome c expressed in Escherichia coli, WT*K79H, with alanine at position 72, and Saccharomyces cerevisiae, yK79H, with trimethyllysine (Tml) at position 72. Co(terpy)22+ is well-suited to the 100 ms to 1 s time scale of the His79-mediated alkaline conformational transition of these variants. Reduction of the His79-heme alkaline conformer by Co(terpy)22+ occurs primarily by gated ET, which involves conversion to the native state followed by reduction, with a small fraction of the His79- heme alkaline conformer directly reduced by Co(terpy)22+. The gated ET experiments show that the mechanism of formation of the His79-heme alkaline conformer involves only two ionizable groups. In previous work, we showed that the mechanism of the His73-mediated alkaline conformational transition requires three ionizable groups. Thus, the mechanism of heme crevice opening depends upon the position of the ligand mediating the process. The microscopic rate constants provided by gated ET studies show that mutation of Tml72 (yK79H variant) in the heme crevice loop to Ala72 (WT*K79H variant) affects the dynamics of heme crevice opening through a small destabilization of both the native conformer and the transition state relative to the His79-heme alkaline conformer. Previous pH jump data had indicated that the Tml72→Ala mutation primarily stabilized the transition state for the His79-mediated alkaline conformational transition. PMID:23899348

Interspecific Competition for Shelters in Territorial and Gregarious Intertidal Grazers: Consequences for Individual Behaviour

PubMed Central

Aguilera, Moisés A.; Navarrete, Sergio A.

2012-01-01

Experiments have shown that interspecific interactions within consumer guilds can alter patterns of distribution, abundance and size of species. Plastic behavioural responses can be modulated by agonistic interactions. In many cases, consumers compete for space and shelters, and these interactions change the manner in which they exploit food. This study investigates the consequences of competition in the spatial and temporal organization of behaviour of intertidal grazers, which share algal resources and the use of rock crevices while resting, but exhibit different body sizes, spatial behaviour and foraging modes. We evaluate interaction strength between small gregarious Siphonaria lessoni and the larger territorial keyhole limpet Fissurella crassa and between S. lessoni and the medium-size gregarious chiton Chiton granosus. Using field manipulations and artificial arenas in the laboratory, we tested whether the use of crevices, micro-spatial distribution and activity are modified by the density of conspecifics and the presence of heterospecifics. Our results show that small-scale spatial segregation observed in the field between S. lessoni and C. granosus result from species-specific differences in habitat use. In turn, we found evidence that spatial segregation between F. crassa and S. lessoni results from highly asymmetric interference competition in the use of shelters. The presence of F. crassa reduced the use of crevices and growth rates of S. lessoni. Effects on growth rates are assumed to result from exposure to harsh environmental conditions rather than food limitation. Thus, neither gregarious behaviour nor differences in activity were sufficient to prevent competition with the larger grazer. Our study illustrates the importance of competition for shelters, which results in behavioural changes of the smaller-sized species, and how these plastic responses can translate into differences in growth rates. Use of shelters can thus be modulated by environmental conditions in a species-specific as well as an interactive manner within consumers’ guilds. PMID:23049980

Biology of bats in Douglas-fir forests.

Treesearch

Robin E. Christy; Stephen D. West

1993-01-01

Twelve species of bats occur in Douglas-fir forests of the Pacific Northwest, of which nine are known to roost in tree cavities, bark crevices, or foliage, and several are closely associated with old-growth forests. Thus bat populations may be detrimentally affected by forest management practices involving the removal of large, old trees and snags. We review the life...

Working the Crevices: Granting Students Authority in Authoritarian Schools

ERIC Educational Resources Information Center

Goodman, Joan F.; Hoagland, Jessica; Pierre-Toussaint, Nadel; Rodriguez, Celeste; Sanabria, Christina

2011-01-01

Schools are beset with a serious "alienation gap" between teachers and students that is no less a problem than the "achievement gap." Increasing student voice is thought to be one means to fill the gap, for it activates agency and thereby decreases passivity. The extent of agency ranges from attentive adult listening to strong student leadership.…

Status of ash (Fraxinus spp.) species in Alabama, Arkansas, Mississippi, and Louisiana, 2013

Treesearch

S.N. Oswalt

2015-01-01

The emerald ash borer (EAB; Agrilus planipennis) is an introduced Asian beetle species that was first detected in trees in the Fraxinus (ash) genus in the United States in 2002. Female EAB beetles lay between 40 to 70 eggs in cracks, crevices, and beneath bark flakes. The eggs hatch within about 2 weeks, larvae bore through the...

ATLAS 60’ Fording Study

DTIC Science & Technology

1992-03-03

crack. Carbon steel stress cracks in the presence of sodium hydroxide (" caustic embrittlement"), whereas austenitic stainless steels stress crack in...transmission life. - Outboard planetary axle design reduces stresses on differential, drive shafts and axle shaft U-joints. . Enclosed oil disc brakes on... Stress Corrosion Crevice Pitting Erosion Corrosion Uniform Corrosion Intergranular Selective Leaching Page 19 Caterpflar Inc. ATLAS Fording Study Q The

Office of Naval Research Overview of Corrosion S&T Program

DTIC Science & Technology

2010-12-02

a carbon induced passivity for LTCSS treated austenitic stainless steels - Low temp. allows interstitial C diffusion, but not substitutional...paraequilibrium carburization mechanism(s) that lead to the enhanced corrosion resistance seaw ater crevice corrosion on 316 Stainless Steel LTC...Treated 316 untreated LTC process TTT diagram LTCSS Surface Modification: • Carbon concentrations > 12 at. % in 316 stainless steel while maintaining

Structural variability and species diversity of a dwarf Caribbean dry forest

Treesearch

E. Medina; E. Cuevas; S. Molina; A.E. Lugo; O. Ramos

2010-01-01

Low stature woody vegetation of the south-west coast of Puerto Rico grows on a rocky calcareous substrate where plants can only root in holes, cracks, and crevices accumulating water and sediments that allow seed germination and seedling development. Being in a coastal location these communities are influenced by steady onshore winds, high solar radiation, and salt...

Coordinated vigilance provides evidence for direct reciprocity in coral reef fishes.

PubMed

Brandl, Simon J; Bellwood, David R

2015-09-25

Reciprocity is frequently assumed to require complex cognitive abilities. Therefore, it has been argued that reciprocity may be restricted to animals that can meet these demands. Here, we provide evidence for the potential presence of direct reciprocity in teleost fishes. We demonstrate that in pairs of coral reef rabbitfishes (f. Siganidae), one fish frequently assumes an upright vigilance position in the water column, while the partner forages in small crevices in the reef substratum. Both behaviours are strongly coordinated and partners regularly alternate their positions, resulting in a balanced distribution of foraging activity. Compared to solitary individuals, fishes in pairs exhibit longer vigilance bouts, suggesting that the help provided to the partner is costly. In turn, fishes in pairs take more consecutive bites and penetrate deeper into crevices than solitary individuals, suggesting that the safety provided by a vigilant partner may outweigh initial costs by increasing foraging efficiency. Thus, the described system appears to meet all of the requirements for direct reciprocity. We argue that the nature of rabbitfish pairs provides favourable conditions for the establishment of direct reciprocity, as continuous interaction with the same partner, simultaneous needs, interdependence, and communication relax the cognitive demands of reciprocal cooperation.

Using Aerogel-Based Insulation Material To Prevent Foam Loss on the Liquid-Hydrogen Intertank

NASA Technical Reports Server (NTRS)

2008-01-01

Uninsulated areas on cryogenic propellant tanks and feedlines cause moisture in the air to condense or ice to form. Flange joints, bracket supports, expansion bellows, and other cavities are uninsulated by design. These areas cannot be sealed because conventional thermal insulation materials would restrict mechanical articulations. Aerogel-based thermal insulation systems are able to seal critical locations such as the liquid-oxygen (LO2) feedline bellows. A new thermal insulation system was also necessary between the intertank wall, flange, and the liquid-hydrogen (LH2) tank dome, where there is a cavity (or crevice) with an exposed 20-K surface. When nitrogen gas is used for purging within the intertank volume, it condenses on this cold surface. Some solid nitrogen may also form on the colder side of the crevice. Voids or discontinuities within the foam can pressurize and cause areas of foam to weaken and break off, reducing thermal efficiency and creating potentially dangerous debris. To prevent this foam loss, we developed a thermal insulation system using bulk-fill aerogel material and demonstrated it with a one-tenth-scale model of the LH2 intertank flange area

Experimental tooth pain elevates substance P and matrix metalloproteinase-8 levels in human gingival crevice fluid.

PubMed

Avellán, Nina-Li; Sorsa, Timo; Tervahartiala, Taina; Forster, Clemens; Kemppainen, Pentti

2008-02-01

Tooth pain can induce a neurogenic inflammatory reaction in gingiva in association with local elevations of matrix metalloproteinase (MMP)-8, which is considered the major tissue destructive protease in gingival crevice fluid (GCF). The pro-inflammatory neuropeptides released by sensory nerves coordinate the activities of the immuno-effector cells and may influence the secretion of MMP-8. With this background, we studied whether experimental tooth pain can trigger changes in GCF levels of the neuropeptide substance P (SP) and MMP-8. The GCF SP levels of stimulated and non-stimulated teeth were analyzed for SP using a competitive enzyme immunoassay (EIA). The GCF MMP-8 levels were determined by quantitative immunofluorometric assay (IFMA). Painful stimulation of the upper central incisor caused significant elevations in GCF SP and MMP-8 levels of the stimulated tooth. At the same time, the GCF SP and MMP-8 levels of non-stimulated control teeth were unchanged. These data indicate that experimental tooth pain can induce local elevations of SP and MMP-8 levels in GCF simultaneously. This supports the possibility of a local neurogenic spread of inflammatory reactions from intrapulpal to surrounding periodontal tissues.

Planar multi-electrode array sensor for localized electrochemical corrosion detection

DOEpatents

Tormoen, Garth William; Brossia, Christopher Sean

2014-01-07

A planarized type of coupled multi-electrode corrosion sensing device. Electrode pads are fabricated on a thin backing, such as a thin film. Each pad has an associated electrical lead for connection to auxiliary electronic circuitry, which may include a resistor associated with each electrical pad. The design permits the device to be easily placed in small crevices or under coatings such as paint.

Corrosion Fatigue

DTIC Science & Technology

1981-10-01

particularly under conditions of cathodic polarization. Sul- fate ion , while less damaging under free corrosion conditions, is equally aggressive at...Editing and Reproduction Ltd Harford 11ouse, 7-9 Charlotte St, London, WIP 1HD I I - PREFACE Failure by fatigue and degradation by corrosion continue to...of halide ions . In the unstressed state, this degrada- tion may be manifested by localized corrosion such as pitting, crevice corrosion or ex

Multi-Scale Investigation of the Formation and Breakdown of Passive Films on Carbon Steel Rebar in Concrete

NASA Astrophysics Data System (ADS)

Ghods, Pouria

The multi-scale investigation presented in this thesis was carried out to understand better the mechanisms of passivation and chloride-induced depassivation of carbon steel reinforcement in concrete. The study consisted of electrochemical experiments (electrochemical impedance spectroscopy, linear polarization resistance, free corrosion potential, anodic polarization), microscopic examinations (scanning electron microscopy, transmission electron microscopy, selected area diffraction, convergent beam electron diffraction), numerical modeling (finite element method), and spectroscopic studies (x-ray photoelectron, energy dispersed x-ray, electron energy loss). Electrochemical and microscopic studies showed that the composition of the pore solution and the surface conditions of the rebar affect the passivity and depassivation of carbon steel in concrete. It was demonstrated that crevices between mill scale and steel may become potential sites for depassivation and pit nucleation. The numerical investigation that was carried out to test this hypothesis confirmed that the ratio of chloride to hydroxide concentrations, Cl-/OH-, in crevices increased to levels higher than that of the bulk pore solution, making crevices more vulnerable to depassivation. Therefore, it was concluded that the variability associated with reported chloride thresholds might be attributed, at least in part, to the variability in mill scale properties resulting from the variability in manufacturing. The nano-scale microscopic and spectroscopic studies indicated the formation of 4-10 nm-thick passive oxide films on carbon steel in simulated concrete pore solutions, and these films consisted of two layers separated with an indistinct border. The inner layer was mainly composed of protective Fe2+-rich oxides that are in epitaxial relationship with the underlying steel surface; while the outer layer mostly consisted of (possibly porous) Fe3+-rich oxides, through which chlorides can penetrate. It was proposed that, in the presence of chlorides, Fe+2-rich oxides in the inner layer transform into Fe+3-rich oxides and potentially become un-protective. Although how this transformation occurs is still subject of future research, there are evidences showing that the process most likely leads to the formation of local anodic and cathodic sites on the steel surface.

[In vitro anti-Trichomonas vaginalis effects of a mixture of dihydroartemisinin and metronidazole].

PubMed

Tang, Zi-Hao; Liu, Ke-Yue; Mei, Jun; Gao, Xing-Zheng

2010-12-30

To observe the effect of a mixture of dihydroartemisinin and metronidazole on ultrastructure of Trichomonas vaginalis trophozoites in vitro for exploring trichomonacidal mechanism of the drug mixture. The trophozoites were cultivated with liver extract solution medium that contained 2.5 x 10(6) parasites/ml. There were dihydroartemisinin 0.5 mg/ml and metronidazole 0.002 mg/ml in the experimental tubes of the drug mixture group. Groups of control (without drug), dihydroartemisinin (1 mg/ml) and metronidazole (5 mg/ml) were established and performed in the same experimental conditions. The parasites were observed by scanning and transmission electron microscopes after having treated with the drugs at 37 degrees for 3.5-5 h. Under scanning electron microscope, the cell membrane of T. vaginalis treated only with dihydroartemisinin for 35 h was damaged, part of pellicle peeled off. Although the surface of the trophozoites treated only with metronidazole for 5 h showed many small bubbles and hollows, the cell membrane looked integral. However, surface of the parasite exposed to the drug mixture for 3.5-4.2 h showed deep folds and cracks, the cell membrane was damaged and even peeled off. When the cell ruptured, the nucleus, axostyle, pelta and hydrogenosomes were exposed, and the cytoplasm spilled out. Transmission electron microscopy showed that the membrane system of the trophozoites treated only with dihydroartemisinin for 3.5 h was damaged considerably. The cytoplasm of damaged parasite spilled out. The cytoplasm of the parasite treated only with metronidazole for 3.5-5 h was damaged seriously. Vacuoles and crevices were visible in the cytoplasm. The cell membrane and the content of the parasites treated with the drug mixture for 3.5-4.5 h were damaged seriously. There were some vacuoles and crevices, dilated endoplasmic reticulum, injured and deformed hydrogenosomes in the cytoplasm. The cell organelles mostly disappeared. Crevices also existed in the nucleus. The nuclear membrane fractured and even disappeared. The acting targets of dihydroartemisinin and metronidazole to T. vaginalis trophozoite were different, and a combination of the two drugs shows stronger effect in killing the parasites.

A complex of cardiac cytochrome c1 and cytochrome c.

PubMed

Chiang, Y L; Kaminsky, L S; King, T E

1976-01-10

The interactions of cytochrome c1 and cytochrome c from bovine cardiac mitochondria were investigated. Cytochrome c1 and cytochrome c formed a 1:1 molecular complex in aqueous solutions of low ionic strength. The complex was stable to Sephadex G-75 chromatography. The formation and stability of the complex were independent of the oxidation state of the cytochrome components as far as those reactions studied were concerned. The complex was dissociated in solutions of ionic strength higher than 0.07 or pH exceeding 10 and only partially dissociated in 8 M urea. No complexation occurred when cytochrome c was acetylated on 64% of its lysine residues or photooxidized on its 2 methionine residues. Complexes with molecular ratios of less than 1:1 (i.e. more cytochrome c) were obtained when polymerized cytochrome c, or cytochrome c with all lysine residues guanidinated, or a "1-65 heme peptide" from cyanogen bromide cleavage of cytochrome c was used. These results were interpreted to imply that the complex was predominantly maintained by ionic interactions probably involving some of the lysine residues of cytochrome c but with major stabilization dependent on the native conformations of both cytochromes. The reduced complex was autooxidizable with biphasic kinetics with first order rate constants of 6 X 10(-5) and 5 X U0(-5) s-1 but did not react with carbon monoxide. The complex reacted with cyanide and was reduced by ascorbate at about 32% and 40% respectively, of the rates of reaction with cytochrome c alone. The complex was less photoreducible than cytochrome c1 alone. The complex exhibited remarkably different circular dichroic behavior from that of the summation of cytochrome c1 plus cytochrome c. We concluded that when cytochromes c1 and c interacted they underwent dramatic conformational changes resulting in weakening of their heme crevices. All results available would indicate that in the complex cytochrome c1 was bound at the entrance to the heme crevice of cytochrome c on the methionine-80 side of the heme crevice.

Variability in colony attendance of crevice-nesting horned puffins: Implications for population monitoring

USGS Publications Warehouse

Harding, A.M.A.; Piatt, John F.; Byrd, G.V.; Hatch, Shyla A.; Konyukhov, N.B.; Golubova, E.U.; Williams, J.C.

2005-01-01

It is difficult to survey crevice-nesting seabirds because nest-sites are hard to identify and count, and the number of adult birds attending a colony can be extremely variable within and between days. There is no standardized method for surveying crevice-nesting horned puffins (Fratercula corniculata), and consequently little is known about abundance or changes in their numbers. We examined the variability in colony attendance of horned puffins at 5 breeding colonies in the North Pacific to assess whether variation in count data can be reduced to a level that would allow us to detect changes in the number of birds attending a colony. We used within-year measures of variation in attendance to examine the power to detect a change in numbers between 2 years, and we used measures of among-year variation to examine the power to detect trends over multiple years. Diurnal patterns of attendance differed among colonies, and among-day variation in attendance was generally lowest from mid- to late-incubation to early chick rearing. Within-year variation in water counts was lower than in land counts, and variation was lower using a daily index based on 5 counts per day than it was using 1 count per day. Measures of among-year variation in attendance also were higher for land-based than water-based counts, and they were higher when we used a 10-day survey period than when we used a 30-day period. The use of either 1 or 5 counts a day during the colony-specific diurnal peak of attendance had little influence on levels of among-year variation. Overall, our study suggests that variation in count data may be reduced to a level that allows detection of trends in numbers. However, more studies of interannual variability in horned puffin attendance are needed. Further, the relationship between count data and breeding population size needs more study before the number of birds present at the colony can be used with confidence as an index of population trend.

First in vitro cycle of the chicken mite, Dermanyssus gallinae (DeGeer 1778), utilizing an artificial feeding device.

PubMed

Bruneau, A; Dernburg, A; Chauve, C; Zenner, L

2001-12-01

The red poultry mite, Dermanyssus gallinae, is one of the most economically deleterious ecto-parasites of layer hens worldwide. D. gallinae is difficult to eliminate from infested poultry farms, and even to study, because it resides on the host only during the bloodmeal at night, and hides in the crevices of poultry houses during the day. Here, the life-cycle of D. gallinae was reproduced entirely in vitro. Mites were incubated in a glass pipette at 30 degrees C, 60-95 degrees relative humidity and total darkness. A feeding apparatus, composed of a membrane, reservoir and blood was fitted on the pipette during bloodmeals. We tested feeding rates on blood mixed with 1 of 3 anti-coagulants (EDTA, heparin and trisodium citrate) at different concentrations, and biological and artificial membranes. The best engorgement and survival rates for all 3 haematophagous life-stages of the parasite were observed in 1-day-old chick membranes and heparinized (0.02 mmo/ml) blood. We then describe the steps in developing a complete self-sustaining in vitro life-cycle. A colony of mites was maintained in vitro for 7 generations. Losses in the first generation were heavy, but survival had multiplied 5-fold by the fifth generation. We hypothesize that heavy mortality rates during the first life-cycle correspond to selective pressure: only the mites which fed and survived in vitro were able to reproduce.

KSC-98pc418

NASA Image and Video Library

1998-02-27

KENNEDY SPACE CENTER, FLA. -- An oyster toadfish (Opsanus tau), like those that are part of the Neurolab payload on Space Shuttle Mission STS-90, is shown in its holding tank in the Space Station Processing Facility. Each fish is between eight and 14 inches long. Toadfish live in an estuarine environment and are native to areas along the Northeast coast of the United States. Since they are bottom dwellers that live in cracks and crevices, a tube is provided in its tank to give it a place to retreat and hide. Investigations during the Neurolab mission will focus on the effects of microgravity on the nervous system. This fish is an excellent model for looking at vestibular function because the architecture of its inner and middle ear are similar to those of mammals with respect to the vestibular apparatus. The crew of STS-90, slated for launch April 16 at 2:19 p.m. EDT, includes Commander Richard Searfoss, Pilot Scott Altman, Mission Specialists Richard Linnehan, Dafydd (Dave) Williams, M.D., and Kathryn (Kay) Hire, and Payload Specialists Jay Buckey, M.D., and James Pawelczyk, Ph.D

KSC-98PC417

NASA Image and Video Library

1998-02-27

KENNEDY SPACE CENTER, FLA. -- Oyster toadfish (Opsanus tau), like those that are part of the Neurolab payload on Space Shuttle Mission STS-90, are shown in their holding tank in the Space Station Processing Facility. Each fish is between 8 and 14 inches long. Toadfish live in an estuarine environment and are native to areas along the Northeast coast of the United States. Since they are bottom dwellers that live in cracks and crevices, tubes are provided in their tank to give them a place to retreat and hide. Investigations during the Neurolab mission will focus on the effects of microgravity on the nervous system. The toadfish fish is an excellent model for looking at vestibular function because the architecture of its inner and middle ear are similar to those of mammals with respect to the vestibular apparatus. The crew of STS-90, slated for launch April 16 at 2:19 p.m. EDT, includes Commander Richard Searfoss, Pilot Scott Altman, Mission Specialists Richard Linnehan, Dafydd (Dave) Williams, M.D., and Kathryn (Kay) Hire, and Payload Specialists Jay Buckey, M.D., and James Pawelczyk, Ph.D

Survival of biofilm-forming Salmonella on stainless steel bolt threads under dry conditions.

PubMed

Morita, Yukio; Komoda, Emiko; Ono, Kazuaki; Kumagai, Susumu

2011-01-01

We examined the survival of two biofilm-forming strains and two biofilm-deficient strains of non typhoid Salmonella (NTS) on stainless steel bolt threads under dry conditions. Five µL of tryptone soya broth or egg yolke mulsion containing NTS strains at a concentration of 9 log cfu/mL was dropped onto the thread surfaces of hexagonal bolts. After inoculation, the bolts were screwed into the nuts, and then removed (Separate type) or not removed (Unit type). The two types of samples were kept in a dry environment (20.0-25.0°C, 2-15% humidity) and bacteria on the surfaces were periodically counted. Biofilm-forming strains were recovered from all samples after 336 days of incubation, but biofilm-deficient strains were isolated from only two of 8 samples after 336 days. This finding demonstrates that NTS can survive for approximately one year on bolt threads, providing direct evidence of the potential risk of constructions having crevices or uneven surfaces as possible contamination sources. The risk of cross-contamination may be higher for biofilm-forming strains than for biofilm-deficient strains.

Chlorpyrifos: an unwelcome pesticide in our homes.

PubMed

Lemus, R; Abdelghani, A

2000-01-01

Chlorpyrifos is an extensively used organophosphate insecticide having many urban and agricultural crop pest control uses. Studies conducted in indoor environments after termiticide, crack-and-crevice, broadcast, or fogger applications have shown that chlorpyrifos exposure can occur via inhalation of residual air concentrations, dermal or oral exposure from residues on floors and carpets, children toys, food, and dust. Not long ago the weight of scientific evidence supported safe indoor use, but recent studies support the possibility that when pregnant female rats are given the pesticide, chlorpyrifos causes brain damage in fetal rats. Moreover, the exposure of young rats to chlorpyrifos impairs early nervous system development. After finding that chlorpyrifos is an exposure risk especially to children, in June 2000 the United States Environmental Protection Agency and manufacturers agreed to voluntary measures that will reduce the exposure of children to chlorpyrifos-containing products. This action implies a search for less harmful new products to replace it and/or safer ways to control pests through basic hygiene. Whichever pest control method is selected, one should keep in mind that preventing environmental pesticide exposure in children is always better than treating the resulting disease.

Reliability evaluation of oil pipelines operating in aggressive environment

NASA Astrophysics Data System (ADS)

Magomedov, R. M.; Paizulaev, M. M.; Gebel, E. S.

2017-08-01

In connection with modern increased requirements for ecology and safety, the development of diagnostic services complex is obligatory and necessary enabling to ensure the reliable operation of the gas transportation infrastructure. Estimation of oil pipelines technical condition should be carried out not only to establish the current values of the equipment technological parameters in operation, but also to predict the dynamics of changes in the physical and mechanical characteristics of the material, the appearance of defects, etc. to ensure reliable and safe operation. In the paper, existing Russian and foreign methods for evaluation of the oil pipelines reliability are considered, taking into account one of the main factors leading to the appearance of crevice in the pipeline material, i.e. change the shape of its cross-section, - corrosion. Without compromising the generality of the reasoning, the assumption of uniform corrosion wear for the initial rectangular cross section has been made. As a result a formula for calculation the probability of failure-free operation was formulated. The proposed mathematical model makes it possible to predict emergency situations, as well as to determine optimal operating conditions for oil pipelines.

Spatially resolved, in-situ monitoring of crack growth via the coupling current in aluminum alloy 5083

NASA Astrophysics Data System (ADS)

Williams, Krystaufeux D.

The work discussed in this dissertation is an experimental validation of a body of research that was created to model stress corrosion cracking phenomenon for 304 stainless steels in boiling water reactors. This coupled environment fracture model (CEFM) incorporates the natural laws of the conservation of charge and the differential aeration hypothesis to predict the amount of stress corrosion crack growth as a function of many external environmental variables, including potential, stress intensity, solution conductivity, oxidizer concentrations, and various other environmental parameters. Out of this approach came the concept of the coupling current; a local corrosion current that flows from within cracks, crevices, pits, etc... of a metal or alloy to the external surface. Because of the deterministic approach taken in the mentioned research, the coupling current analysis and CEFM model can be applied to the specific problem of SCC in aluminum alloy 5083 (the alloy of interest for this dissertation that is highly sought after today because of its corrosion resistance and high strength to weight ratio). This dissertation research is specifically devoted to the experimental verification of the coupling current, which results from a coupling between the crack's internal and external environments, by spatially resolving them using the scanning vibrating probe (SVP) as a tool. Hence, through the use of a unique fracture mechanics setup, simultaneous mechanical and local electrochemical data may be obtained, in situ..

Mechanical Rope and Cable

DTIC Science & Technology

1975-04-01

seawater. The principal effect of crevices on the corrosion of zinc- or aluminum - coated or uncoated steel rope is to entrap corrosive liquids and...visual inspection of the rope surface. j 5. The effect of stresses, such as tensile, bending, torsion , and comn- pression, upon rope in service is not...questionable A value. d. The effect of stresses, such as tensile, bending, torsion , and compressive contact, on rope is not understood well. 2

Truncated Dual-Cap Nucleation Site Development

NASA Technical Reports Server (NTRS)

Matson, Douglas M.; Sander, Paul J.

2012-01-01

During heterogeneous nucleation within a metastable mushy-zone, several geometries for nucleation site development must be considered. Traditional spherical dual cap and crevice models are compared to a truncated dual cap to determine the activation energy and critical cluster growth kinetics in ternary Fe-Cr-Ni steel alloys. Results of activation energy results indicate that nucleation is more probable at grain boundaries within the solid than at the solid-liquid interface.

METHOD OF IMPROVING CORROSION RESISTANCE OF ZIRCONIUM

DOEpatents

Shannon, D.W.

1961-03-28

An improved intermediate rinse for zirconium counteracts an anomalous deposit that often results in crevices and outof-the-way places when ordinary water is used to rinse away a strong fluoride etching solution designed to promote passivation of the metal. The intermediate rinse, which is used after the etching solution and before the water, is characterized by a complexing agent for fluoride ions such as aluminum or zirconium nitrates or chlorides.

Linear shaped charge

DOEpatents

Peterson, David; Stofleth, Jerome H.; Saul, Venner W.

2017-07-11

Linear shaped charges are described herein. In a general embodiment, the linear shaped charge has an explosive with an elongated arrowhead-shaped profile. The linear shaped charge also has and an elongated v-shaped liner that is inset into a recess of the explosive. Another linear shaped charge includes an explosive that is shaped as a star-shaped prism. Liners are inset into crevices of the explosive, where the explosive acts as a tamper.

Thrips domiciles protect larvae from desiccation in an arid environment

PubMed Central

2014-01-01

Desiccation is a particular risk for small animals in arid environments. In response, many organisms “construct niches,” favorable microenvironments where they spend part or all of their life cycle. Some maintain such environments for their offspring via parental care. Insect eggs are often protected from desiccation by parentally derived gels, casings, or cocoons, but active parental protection of offspring from desiccation has never been demonstrated. Most free-living thrips (Thysanoptera) alleviate water loss via thigmotaxis (crevice seeking). In arid Australia, Acacia thrips (Phlaeothripidae) construct many kinds of niche. Some thrips induce galls; others, like Dunatothrips aneurae, live and breed within “domiciles” made from loosely glued phyllodes. The function of domiciles is unknown; like other constructed niches, they may 1) create favorable microenvironments, 2) facilitate feeding, 3) protect from enemies, or a combination. To test the first 2 alternatives experimentally, field-collected domiciles were destroyed or left intact. Seven-day survival of feeding and nonfeeding larval stages was monitored at high (70–80%) or low (8–10%, approximately ambient) humidity. Regardless of humidity, most individuals survived in intact domiciles, whereas for destroyed domiciles, survival depended on humidity, suggesting parents construct and maintain domiciles to prevent offspring desiccating. Feeding and nonfeeding larvae had similar survival patterns, suggesting the domicile’s role is not nutritional. Outside domiciles, survival at “high” humidity was intermediate, suggesting very high humidity requirements, or energetic costs of wandering outside domiciles. D. aneurae commonly cofound domiciles; cofoundresses may benefit both from shared nestbuilding costs, and from “deferred byproduct mutualism,” that is, backup parental care in case of mortality. PMID:25419084

Part I. Corrosion studies of continuous alumina fiber reinforced aluminum-matrix composites. Part II. Galvanic corrosion between continuous alumina fiber reinforced aluminum-matrix composites and 4340 steel

NASA Astrophysics Data System (ADS)

Zhu, Jun

Part I. The corrosion performance of continuous alumina fiber reinforced aluminum-matrix composites (CF-AMCs) was investigated in both the laboratory and field environments by comparing them with their respective monolithic matrix alloys, i.e., pure Al, A1-2wt%Cu T6, and Al 6061 T6. The corrosion initiation sites were identified by monitoring the changes in the surface morphology. Corrosion current densities and pH profiles at localized corrosion sites were measured using the scanning-vibrating electrode technique and the scanning ion-selective electrode technique, respectively. The corrosion damage of the materials immersed in various electrolytes, as well as those exposed in a humidity chamber and outdoor environments, was evaluated. Potentiodynamic polarization behavior was also studied. The corrosion initiation for the composites in 3.15 wt% NaCl occurred primarily around the Fe-rich intermetallic particles, which preferentially existed around the fiber/matrix interface on the composites. The corrosion initiation sites were also caused by physical damage (e.g., localized deformation) to the composite surface. At localized corrosion sites, the buildup of acidity was enhanced by the formation of micro-crevices resulting from fibers left in relief as the matrix corroded. The composites that were tested in exposure experiments exhibited higher corrosion rates than their monolithic alloys. The composites and their monolithic alloys were subjected to pitting corrosion when anodically polarized in the 3.15 wt% NaCl, while they passivated when anodically polarized in 0.5 M Na2SO4. The experimental results indicated that the composites exhibited inferior corrosion resistance compared to their monolithic matrix alloys. Part II. Galvanic corrosion studies were conducted on CF-AMCs coupled to 4340 steel since CF-AMCs have low density and excellent mechanical properties and are being considered as potential jacketing materials for reinforcing steel gun barrels. Coupled and uncoupled coupons were immersed in various electrolytes, exposed to a humidity chamber, and exposed at outdoor test sites. Results showed that the corrosion rates of the CF-AMCs increased, while those of the 4340 steel decreased after being coupled together, in most cases. Crevice corrosion was also observed in these exposure experiments. Zero resistance ammeter (ZRA) experiments were conducted to record the galvanic-corrosion rates and potentials of the couples. The CF-AMCs were found to serve as anodes, while the steel was cathodic, in most test conditions. Galvanic performance predicted by polarization experiments was in close agreement with the ZRA results. Key words. Aluminum, metal-matrix composites, alumina fiber, pitting corrosion, galvanic corrosion.

Can gingival crevicular blood be relied upon for assessment of blood glucose level?

PubMed

Dwivedi, Shivani; Verma, Sharmila J; Shah, Monali; Jain, Kapil

2014-11-01

Diabetes mellitus (DM) is undiagnosed in approximately half of the patients actually suffering from the disease. In addition, the prevalence of DM is more than twice as high as in patients with periodontitis when compared to periodontally healthy subjects. Thus, a high number of patients with periodontitis may have undiagnosed DM. The purpose of the present study was to evaluate whether blood oozing from a gingival crevice during routine periodontal examination can be used for determining glucose levels. Observational cross-sectional studies were carried out in 75 patients (43 males and 32 females) with chronic periodontitis who were divided into two groups: Group I and Group II, respectively. Blood oozing from the gingival crevices of anterior teeth following periodontal probing was collected with the stick of glucose self-monitoring device, and the blood glucose levels were measured. At the same time, finger-prick blood was taken for glucometric analysis and subsequent readings were recorded. The patient's blood glucose values ranged from 74 to 256 mg/dl. The comparison between gingival crevicular blood and finger-prick blood showed a very strong correlation, with a t value of 3.97 (at P value = 0.001). The data from this study has shown that GCB collected during diagnostic periodontal examination can be an excellent source of blood for glucometric analysis.

Corrosion at the head-neck interface of current designs of modular femoral components: essential questions and answers relating to corrosion in modular head-neck junctions.

PubMed

Osman, K; Panagiotidou, A P; Khan, M; Blunn, G; Haddad, F S

2016-05-01

There is increasing global awareness of adverse reactions to metal debris and elevated serum metal ion concentrations following the use of second generation metal-on-metal total hip arthroplasties. The high incidence of these complications can be largely attributed to corrosion at the head-neck interface. Severe corrosion of the taper is identified most commonly in association with larger diameter femoral heads. However, there is emerging evidence of varying levels of corrosion observed in retrieved components with smaller diameter femoral heads. This same mechanism of galvanic and mechanically-assisted crevice corrosion has been observed in metal-on-polyethylene and ceramic components, suggesting an inherent biomechanical problem with current designs of the head-neck interface. We provide a review of the fundamental questions and answers clinicians and researchers must understand regarding corrosion of the taper, and its relevance to current orthopaedic practice. Cite this article: Bone Joint J 2016;98-B:579-84. ©2016 The British Editorial Society of Bone & Joint Surgery.

Corrosion and fatigue of surgical implants

NASA Technical Reports Server (NTRS)

Lisagor, W. B.

1975-01-01

Implants for the treatment of femoral fractures, mechanisms leading to the failure or degradation of such structures, and current perspectives on surgical implants are discussed. Under the first heading, general usage, materials and procedures, environmental conditions, and laboratory analyses of implants after service are considered. Corrosion, crevice corrosion, stress corrosion cracking, intergranular corrosion, pitting corrosion, fatigue, and corrosion fatigue are the principal degradation mechanisms described. The need for improvement in the reliability of implants is emphasized.

[Developmental radicular groove as a cause of endodontic failure].

PubMed

Fabra Campos, H; Millet Part, J

1989-01-01

A clinical case of apical injury on an upper lateral incisor with endodontical and surgical failures in its treatment is presented. Extraction of the incisor and its study at the stereoscopic microscope showed the existence of a developmental groove running from the cingulum to the end of the root, establishing a communication between the crevice and the apical part of the tooth. Bacterial infection through the groove could provide an explanation for treatment failure.

Crevice Corrosion Behavior of 45 Molybdenum-Containing Stainless Steels in Seawater.

DTIC Science & Technology

1981-12-01

Armco, Avesta Jernverks, Cabot, Carpenter Technology, Crucible, Eastern, Firth-Brown, Huntington, Jessup, Langley Alloys, and Uddeholm. 16...Department of Energy, Report ANL/OTEC-BCM-022. 7. Wallen, B., and M. Liljas, " Avesta 254 SMO - A New, High Molybdenum Stainless Steel," presented at NKM8...1977).; 11. Wallen, B., " Avesta 254 SMO - A Stainless Steel for Seawater Service," presented at the Advanced Stainless Steels for Turbine Condensors

Three-dimensional interstitial space mediates predator foraging success in different spatial arrangements.

PubMed

Hesterberg, Stephen G; Duckett, C Cole; Salewski, Elizabeth A; Bell, Susan S

2017-04-01

Identifying and quantifying the relevant properties of habitat structure that mediate predator-prey interactions remains a persistent challenge. Most previous studies investigate effects of structural density on trophic interactions and typically quantify refuge quality using one or two-dimensional metrics. Few consider spatial arrangement of components (i.e., orientation and shape) and often neglect to measure the total three-dimensional (3D) space available as refuge. This study tests whether the three-dimensionality of interstitial space, an attribute produced by the spatial arrangement of oyster (Crassostrea virginica) shells, impacts the foraging success of nektonic predators (primary blue crab, Callinectes sapidus) on mud crab prey (Eurypanopeus depressus) in field and mesocosm experiments. Interstices of 3D-printed shell mimics were manipulated by changing either their orientation (angle) or internal shape (crevice or channel). In both field and mesocosm experiments, under conditions of constant structural density, predator foraging success was influenced by 3D aspects of interstitial space. Proportional survivorship of tethered mud crabs differed significantly as 3D interstitial space varied by orientation, displaying decreasing prey survivorship as angle of orientation increased (0° = 0.76, 22.5° = 0.13, 45° = 0.0). Tethered prey survivorship was high when 3D interstitial space of mimics was modified by internal shape (crevice survivorship = 0.89, channel survivorship = 0.96) and these values did not differ significantly. In mesocosms, foraging success of blue crabs varied with 3D interstitial space as mean proportional survivorship (± SE) of mud crabs was significantly lower in 45° (0.27 ± 0.06) vs. 0° (0.86 ± 0.04) orientations and for crevice (0.52 ± 0.11) vs. channel shapes (0.95 ± 0.02). These results suggest that 3D aspects of interstitial space, which have direct relevance to refuge quality, can strongly influence foraging success in our oyster reef habitat. Our findings highlight the importance of spatial arrangement in mediating consumptive pathways in hard-structured habitats and demonstrate how quantifying the three-dimensionality of living space captures aspects of habitat structure that have been missing from previous empirical studies of trophic interactions and structural complexity. © 2017 by the Ecological Society of America.

Passive Films, Surface Structure and Stress Corrosion and Crevice Corrosion Susceptibility.

DTIC Science & Technology

1980-08-01

with pure titanium ( 4 ], it is of interest to pursue the effects on titanium -palladium alloys, to evaluate their susceptibility to stress corrosion...cracking due to hydrogen embrittlement with the field ion microscope, and to compare the results with those previously obtained with pure titanium [ 4 ...characterized as 99.99+ percent pure, and was used in the previous field ion microscopy study of titanium [ 4 ], where it was found that strain annealing titanium

Effect of chlorides on solution corrosivity of methyldiethanolamine (MDEA) solutions

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

Rooney, P.C.; Bacon, T.R.; DuPart, M.S.

1997-08-01

Solution corrosivity of MDEA/water solutions containing added HCl or NaCl have been measured by weight loss coupons at 250 F and by linear polarization resistance (LPR) at 208 F using carbon steel, 304SS, 316SS and 410SS. General corrosion as well as pitting or crevice corrosion tendencies were recorded for each species. Based on these results, recommendations are made for chlorides in MDEA that minimizes corrosion in gas treating operations.

Passive Films, Surface Structure and Stress Corrosion and Crevice Corrosion Susceptibility.

DTIC Science & Technology

1983-11-01

thiadiazole ( DMTDA ), when dispersed in the coating were observed to delay the onset of delamifnation. Catechol was found to be an ineffective inhibitor. A...similar beneficial effect was noted with a two-layer system employing a zinc chromate primer. However, when 8-HQ and DMTDA were applied by an anodic...shows the ellipsometric responses for the iron/acrylic system with DMTDA dispersed in the coating. The pre-puncture signals suggest changes in surface

Seawater Corrosion of Fasteners in Various Structural Materials

DTIC Science & Technology

1976-04-01

17 - 4PH stainless steel. The seven bolt materials were: 2024 aluminum, anodized ASTM grade 5 steel, 304 and 316 stainless steels, A286 stain- less...performed well in titanium structures. Use of MP35N, A286, and 304 stainless steel fasteners for constantly immersed 17 - 4PH stainless steel structures...would have been satisfactory only if sealant was not used and if protection had been provided to the 17 - 4PH to minimize crevice corrosion. Additional

Predation cues rather than resource availability promote cryptic behaviour in a habitat-forming sea urchin.

PubMed

Spyksma, Arie J P; Taylor, Richard B; Shears, Nick T

2017-03-01

It is well known that predators often influence the foraging behaviour of prey through the so-called "fear effect". However, it is also possible that predators could change prey behaviour indirectly by altering the prey's food supply through a trophic cascade. The predator-sea urchin-kelp trophic cascade is widely assumed to be driven by the removal of sea urchins by predators, but changes in sea urchin behaviour in response to predators or increased food availability could also play an important role. We tested whether increased crevice occupancy by herbivorous sea urchins in the presence of abundant predatory fishes and lobsters is a response to the increased risk of predation, or an indirect response to higher kelp abundances. Inside two New Zealand marine reserves with abundant predators and kelp, individuals of the sea urchin Evechinus chloroticus were rarer and remained cryptic (i.e. found in crevices) to larger sizes than on adjacent fished coasts where predators and kelp are rare. In a mesocosm experiment, cryptic behaviour was induced by simulated predation (the addition of crushed conspecifics), but the addition of food in the form of drift kelp did not induce cryptic behaviour. These findings demonstrate that the 'fear' of predators is more important than food availability in promoting sea urchin cryptic behaviour and suggest that both density- and behaviourally mediated interactions are important in the predator-sea urchin-kelp trophic cascade.

Stereo imaging and cytocompatibility of a model dental implant surface formed by direct laser fabrication.

PubMed

Mangano, Carlo; Raspanti, Mario; Traini, Tonino; Piattelli, Adriano; Sammons, Rachel

2009-03-01

Direct laser fabrication (DLF) allows solids with complex geometry to be produced by sintering metal powder particles in a focused laser beam. In this study, 10 Ti6Al4V alloy model dental root implants were obtained by DLF, and surface characterization was carried out using stereo scanning electron microscopy to produce 3D reconstructions. The surfaces were extremely irregular, with approximately 100 microm deep, narrow intercommunicating crevices, shallow depressions and deep, rounded pits of widely variable shape and size, showing ample scope for interlocking with the host bone. Roughness parameters were as follows: R(t), 360.8 microm; R(z), 358.4 microm; R(a), 67.4 microm; and R(q), 78.0 microm. Disc specimens produced by DLF with an identically prepared surface were used for biocompatibility studies with rat calvarial osteoblasts: After 9 days, cells had attached and spread on the DLF surface, spanning across the crevices, and voids. Cell density was similar to that on a commercial rough microtextured surface but lower than on commercial smooth machined and smooth-textured grit-blasted, acid-etched surfaces. Human fibrin clot extension on the DLF surface was slightly improved by inorganic acid etching to increase the microroughness. With further refinements, DLF could be an economical means of manufacturing implants from titanium alloys. (c) 2008 Wiley Periodicals, Inc.

Geochemical evidence for hydroclimatic variability over the last 2460 years from Crevice Lake in Yellowstone National Park, USA

USGS Publications Warehouse

Stevens, L.R.; Dean, W.E.

2008-01-01

A 2460-year-long hydroclimatic record for Crevice Lake, Yellowstone National Park, Montana was constructed from the ??18O values of endogenic carbonates. The ??18O record is compared to the Palmer Hydrologic Drought Index (PHDI) and Pacific Decadal Oscillation (PDO) indices, as well as inferred discharge of the Yellowstone River. During the last century, high ??18O values coincide with drought conditions and the warm phase of the PDO index. Low ??18O values coincide with wet years and a negative PDO index. Comparison of tree-ring inferred discharge of the Yellowstone River with the ??18O record over the last 300 years indicates that periods of high discharge (i.e., wet winters with significant snow pack) correspond with low ??18O values. Extrapolating this relationship we infer wet winters and high river discharge for the periods of 1090-1030, 970-870, 670-620, and 500-430 cal years BP. The wet intervals at 670 and 500 cal BP are synchronous with similar events in Banff, Canada and Walker Lake, Nevada. The wet intervals at 970 and 670 cal BP overlap with wet intervals at Walker Lake and major drought events identified in the western Great Basin. These results suggest that the northern border of Yellowstone National Park straddles the boundary between Northern Rocky Mountains and Great Basin climate regimes. ?? 2007 Elsevier Ltd and INQUA.

Anodized titanium and stainless steel in contact with CFRP: an electrochemical approach considering galvanic corrosion.

PubMed

Mueller, Yves; Tognini, Roger; Mayer, Joerg; Virtanen, Sannakaisa

2007-09-15

The combination of different materials in an implant gives the opportunity to better fulfill the requirements that are needed to improve the healing process. However, using different materials increases the risk of galvanic coupling corrosion. In this study, coupling effects of gold-anodized titanium, stainless steel for biomedical applications, carbon fiber reinforced polyetheretherketone (CFRP), and CFRP containing tantalum fibers are investigated electrochemically and by long-term immersion experiments in simulated body fluid (SBF). Potentiodynamic polarization experiments (i/E curves) and electrochemical impedance spectroscopy (EIS) of the separated materials showed a passive behavior of the metallic samples. Anodized titanium showed no corrosion attacks, whereas stainless steel is highly susceptibility for localized corrosion. On the other side, an active dissolution behavior of both of the CFRPs in the given environment could be determined, leading to delaminating of the carbon fibers from the matrix. Long-term immersion experiments were carried out using a set-up especially developed to simulate coupling conditions of a point contact fixator system (PC-Fix) in a biological environment. Electrochemical data were acquired in situ during the whole immersion time. The results of the immersion experiments correlate with the findings of the electrochemical investigation. Localized corrosion attacks were found on stainless steel, whereas anodized titanium showed no corrosion attacks. No significant differences between the two CFRP types could be found. Galvanic coupling corrosion in combination with crevice conditions and possible corrosion mechanisms are discussed. Copyright 2007 Wiley Periodicals, Inc.

Ants learn to rely on more informative attributes during decision-making.

PubMed

Sasaki, Takao; Pratt, Stephen C

2013-01-01

Evolutionary theory predicts that animals act to maximize their fitness when choosing among a set of options, such as what to eat or where to live. Making the best choice is challenging when options vary in multiple attributes, and animals have evolved a variety of heuristics to simplify the task. Many of these involve ranking or weighting attributes according to their importance. Because the importance of attributes can vary across time and place, animals might benefit by adjusting weights accordingly. Here, we show that colonies of the ant Temnothorax rugatulus use their experience during nest site selection to increase weights on more informative nest attributes. These ants choose their rock crevice nests on the basis of multiple features. After exposure to an environment where only one attribute differentiated options, colonies increased their reliance on this attribute relative to a second attribute. Although many species show experience-based changes in selectivity based on a single feature, this is the first evidence in animals for adaptive changes in the weighting of multiple attributes. These results show that animal collectives, like individuals, change decision-making strategies according to experience. We discuss how these colony-level changes might emerge from individual behaviour.

Morphological characterization of as-received and in vivo orthodontic stainless steel archwires.

PubMed

Daems, Julie; Celis, Jean-Pierre; Willems, Guy

2009-06-01

This study was undertaken to evaluate the material degradation of clinical bracket-archwire-contacting surfaces after in vivo orthodontic use. Twenty-four stainless steel multiloop edgewise archwires with two different cross sections (0.016 x 0.016 and 0.016 x 0.022 inches) were used for at least 6 months in the mouths of 14 patients. The surfaces of both as-received (cross-section of 0.016 x 0.016, 0.016 x 0.022, and 0.017 x 0.025 inches) and the in vivo wires were examined using scanning electron microscopy. The as-received wires exhibited an inhomogeneous surface with different surface irregularities resulting from the manufacturing process. For the in vivo archwires, an increase in the variety, type, and number of surface irregularities were observed. Crevice corrosion occurred not only at surface irregularities formed during manufacturing and orthodontic handling but also at the bracket-archwire-contacting surfaces and at the archwire surfaces coated with plaque and food remnants. This corrosion may be linked to the formation of a micro-environment at these locations. In addition, a limited number of signs of degradation induced during in vivo testing due to wear and friction were observed.

Effect of cloric acid concentration on corrosion behavior of Ni/Cr coated on carbon steel

NASA Astrophysics Data System (ADS)

Desiati, Resetiana Dwi; Sugiarti, Eni; Thosin, K. A. Zaini

2018-05-01

Corrosion is one of the causes of metal degradation. Carbon steel (Fe) is easy to corrode in the extreme environment. Coating on carbon steel is required to improve corrosion resistance owing to protection or hindrance to extreme environmental conditions. In this present work, carbon steel was coated by electroplating techniques for nickel and pack cementation for chrome. The corrosion rate test was performed by Weight Loss method on FeNiCr, FeNi, FeCr and uncoated Fe as comparator which was dyed in 37% HCl and 25% HCl which had previously been measured dimension and mass. The immersion test result of FeNiCr and FeNi specimen were better than FeCr and uncoated Fe in terms of increasing corrosion resistance. The corrosion rate for 56 hours in 37% HCl for FeNiCr was 1.592 mm/y and FeNi was 3.208 mm/y, FeCr only lasted within 32 hours with corrosion rate was 6.494 mm/y. Surface of the sample after the corrosion test there was pitting, crevice corrosion and alloy cracking caused by chloride. The higher the concentration of HCl the faster the corrosion rate.

An analytical investigation of NO sub x control techniques for methanol fueled spark ignition engines

NASA Technical Reports Server (NTRS)

Browning, L. H.; Argenbright, L. A.

1983-01-01

A thermokinetic SI engine simulation was used to study the effects of simple nitrogen oxide control techniques on performance and emissions of a methanol fueled engine. As part of this simulation, a ring crevice storage model was formulated to predict UBF emissions. The study included spark retard, two methods of compression ratio increase and EGR. The study concludes that use of EGR in high turbulence, high compression engines will both maximize power and thermal efficiency while minimizing harmful exhaust pollutants.

Attachment Levels and Crevicular Depths at the Distal of Mandibular Second Molars Following Removal of Adjacent Third Molars.

DTIC Science & Technology

1981-02-01

attachment by determining the distance between the bottom of the crevice and the cemento -enamel junction prior to surgery were unsuccessful, but they were...measuring from the tips of the distolingual and distobuccal cusps and the midpoint of the distal marginal ridge (the cemento -enamel junction could not be...The cemento -enamel junction, usually used as a refer- ence point for determining attachment level, could not be visualized on the distal of the

Ultrasound-induced inertial cavitation from gas-stabilizing nanoparticles.

PubMed

Kwan, J J; Graham, S; Myers, R; Carlisle, R; Stride, E; Coussios, C C

2015-08-01

The understanding of cavitation from nanoparticles has been hindered by the inability to control nanobubble size. We present a method to manufacture nanoparticles with a tunable single hemispherical depression (nanocups) of mean diameter 90, 260, or 650 nm entrapping a nanobubble. A modified Rayleigh-Plesset crevice model predicts the inertial cavitation threshold as a function of cavity size and frequency, and is verified experimentally. The ability to tune cavitation nanonuclei and predict their behavior will be useful for applications ranging from cancer therapy to ultrasonic cleaning.

Cavitation Inception Scale Effects. 1. Nuclei Distributions in Natural Waters. 2. Cavitation Inception in a Turbulent Shear Flow.

DTIC Science & Technology

1987-05-01

ratio of specific heats for the gas and an adiabatic bubble pressure- volume relation has been assumed (Plesset & Prosperetti 1977). When viscosity...pressure because of surface tension at the gas -liquid interface , so the gas is stabilized in the crevice and will not dissolve into the liquid. The concave... interface toward the gas is estab- lished by the hydrophobic nature of the particle, and results in surface tension acting to oppose the liquid

Evaluation of Pad 18 Spent Mercury Gold Trap Stainless Steel Container Failure

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

Skidmore, E.

Failure of the Pad 18 spent mercury gold trap stainless steel waste container is principally attributed to corrosion induced by degradation of plasticized polyvinyl chloride (pPVC) waste packaging material. Dehydrochlorination of pPVC polymer by thermal and/or radiolytic degradation is well-known to evolve HCl gas, which is highly corrosive to stainless steel and other metals in the presence of moisture. Degradation of the pPVC packaging material was likely caused by radiolysis in the presence of tritium gas within the waste container, though other degradation mechanisms (aging, thermo-oxidation, plasticizer migration) over 30 years storage may have contributed. Corrosion was also likely enhancedmore » by the crevice in the container weld design, and may have been enhanced by the presence of tritiated water. Similar non-failed spent mercury gold trap waste containers did not show radiographic evidence of plastic packaging or trapped free liquid within the container. Therefore, those containers are not expected to exhibit similar failures. Halogenated polymers such as pPVC subject to degradation can evolve halide gases such as HCl, which is corrosive in the presence of moisture and can generate pressure in sealed systems.« less

The formation of floor-fractured craters in Xanthe Terra

NASA Astrophysics Data System (ADS)

Sato, Hiroyuki; Kurita, Kei; Baratoux, David

2010-05-01

Floor-fractured craters (FFC) are a peculiar form of degradation of impact craters defined by the presence of crevice networks and mesas affecting crater floors. They are preferentially distributed near chaotic terrains and outflow channels. The scope of this paper is to present a detailed systematic analysis of FFC at Xanthe Terra. FFC morphologies in this region are classified into five types making a picture of different stages of the same degradation process. FFC are geographically intermixed with un-fractured normal craters (non-FFC). Young craters are less prone to show this type of degradation, as suggested by fresh ejecta layer with preserved crater floor. Size distributions of FFC and non-FFC indicate that larger craters are preferentially fractured. Careful examinations of the crater floor elevations reveal that the crevices often extend deeper than the original crater cavity. Furthermore, an onset depth for the formation of FFC is evidenced from the difference of spatial distributions between FFC and non-FFC. Roof-collapsed depressions observed in the same region have been also documented and their characteristics suggest the removal of subsurface material at depth from about 1200 to 4000 m. These observations taken together suggest a subsurface zone of volume deficit at depth from 1 to 2 km down to several kilometers responsible for FFC formation. Then a scenario of FFC formations is presented in the context of groundwater discharge events at the late Hesperian. This scenario involves two key processes, Earth fissuring and piping erosion, known to occur with rapid groundwater migrations on Earth.

Revised methods for estimating potential reentry exposure associated with indoor crack and crevice and perimeter application.

PubMed

Driver, Jeffrey H; Ross, John H; Pandian, Muhilan; Selim, Sami; Sharp, Janice K

2013-01-01

Surface deposition of insecticides applied as indoor residential foggers, baseboard or perimeter sprays, spot sprays, and crack-and-crevice (C&C) sprays represent pathways of unintentional, postapplication exposure for children and adults. Estimation of the magnitude of this exposure following an application event is associated with uncertainty due to many factors, including (1) surface residue deposition and distribution, (2) access to and the nature of contact with treated surfaces based on time-activity patterns of residents, and (3) the role of residue removal mechanisms such as cleaning treated surfaces, pesticide degradation or redistribution, and hand washing and bathing following contact. A comparative spatial deposition study was conducted involving broadcast, perimeter, and C&C application methods. Residues measured using a spatial grid of deposition dosimeters on floor surfaces demonstrated significantly lower residue concentrations in readily accessible areas following C&C and perimeter applications, versus broadcast treatment. Analyses of other monitoring studies support this finding. The implications of these findings are discussed for both screening-level and higher tier probabilistic postapplication, residential exposure assessment. The U.S. Environmental Protection Agency (EPA) current guidance on interpretation of deposition following C&C application is supported by data in this study and others that indicate a ratio of 10:1 for deposition for broadcast versus C&C application. However, the perimeter deposition data are quite similar to C&C deposition and do not support a 70/30 default relative to broadcast recommended by the U.S. EPA (2012).

Holocene seasonal variability inferred from multiple proxy records from Crevice Lake, Yellowstone National Park, USA

USGS Publications Warehouse

Whitlock, Cathy; Dean, Walter E.; Fritz, Sherilyn C.; Stevens, Lora R.; Stone, Jeffery R.; Power, Mitchell J.; Rosenbaum, Joseph R.; Pierce, Kenneth L.; Bracht-Flyr, Brandi B.

2012-01-01

A 9400-yr-old record from Crevice Lake, a semi-closed alkaline lake in northern Yellowstone National Park, was analyzed for pollen, charcoal, geochemistry, mineralogy, diatoms, and stable isotopes to develop a nuanced understanding of Holocene environmental history in a region of northern Rocky Mountains that receives both summer and winter precipitation. The limited surface area, conical bathymetry, and deep water (> 31 m) of Crevice Lake create oxygen-deficient conditions in the hypolimnion and preserve annually laminated sediment (varves) for much of the record. Pollen data indicate that the watershed supported a closed Pinus-dominated forest and low fire frequency prior to 8200 cal yr BP, followed by open parkland until 2600 cal yr BP, and open mixed-conifer forest thereafter. Fire activity shifted from infrequent stand-replacing fires initially to frequent surface fires in the middle Holocene and stand-replacing events in recent centuries. Low values of δ18O suggest high winter precipitation in the early Holocene, followed by steadily drier conditions after 8500 cal yr BP. Carbonate-rich sediments before 5000 cal yr BP imply warmer summer conditions than after 5000 cal yr BP. High values of molybdenum (Mo), uranium (U), and sulfur (S) indicate anoxic bottom-waters before 8000 cal yr BP, between 4400 and 3900 cal yr BP, and after 2400 cal yr BP. The diatom record indicates extensive water-column mixing in spring and early summer through much of the Holocene, but a period between 2200 and 800 cal yr BP had strong summer stratification, phosphate limitation, and oxygen-deficient bottom waters. Together, the proxy data suggest wet winters, protracted springs, and warm effectively wet summers in the early Holocene and less snowpack, cool springs, warm dry summers in the middle Holocene. In the late Holocene, the region and lake experienced extreme changes in winter, spring, and summer conditions, with particularly short springs and dry summers and winters during the Roman Warm Period (~ 2000 cal yr BP) and Medieval Climate Anomaly (1200–800 cal yr BP). Long springs and mild summers occurred during the Little Ice Age, and these conditions persist to the present. Although the proxy data indicate effectively wet summer conditions in the early Holocene and drier conditions in the middle and late Holocene, none point specifically to changes in summer precipitation as the cause. Instead, summer conditions were governed by multi-seasonal controls on effective moisture that operated over multiple time scales.

Enhancement Of Water-Jet Stripping Of Foam

NASA Technical Reports Server (NTRS)

Cosby, Steven A.; Shockney, Charles H.; Bates, Keith E.; Shalala, John P.; Daniels, Larry S.

1995-01-01

Improved robotic high-pressure-water-jet system strips foam insulation from parts without removing adjacent coating materials like paints, primers, and sealants. Even injects water into crevices and blind holes to clean out foam, without harming adjacent areas. Eliminates both cost of full stripping and recoating and problem of disposing of toxic solutions used in preparation for coating. Developed for postflight refurbishing of aft skirts of booster rockets. System includes six-axis robot provided with special end effector and specially written control software, called Aftfoam. Adaptable to cleaning and stripping in other industrial settings.

Seasonal patterns in body temperature of free-living rock hyrax (Procavia capensis).

PubMed

Brown, Kelly J; Downs, Colleen T

2006-01-01

Rock hyrax (Procavia capensis) are faced with large daily fluctuations in ambient temperature during summer and winter. In this study, peritoneal body temperature of free-living rock hyrax was investigated. During winter, when low ambient temperatures and food supply prevail, rock hyrax maintained a lower core body temperature relative to summer. In winter body temperatures during the day were more variable than at night. This daytime variability is likely a result of body temperatures being raised from basking in the sun. Body temperatures recorded during winter never fell to low levels recorded in previous laboratory studies. During summer ambient temperatures exceeded the thermoneutral zone of the rock hyrax throughout most of the day, while crevice temperatures remained within the thermoneutral zone of rock hyrax. However, in summer variation in core body temperature was small. Minimum and maximum body temperatures did not coincide with minimum and maximum ambient temperatures. Constant body temperatures were also recorded when ambient temperatures reached lethal limits. During summer it is likely that rock hyrax select cooler refugia to escape lethal temperatures and to prevent excessive water loss. Body temperature of rock hyrax recorded in this study reflects the adaptability of this animal to the wide range of ambient temperatures experienced in its natural environment.

Susceptibility of nitinol to localized corrosion.

PubMed

Pound, Bruce G

2006-04-01

The effect of different conditions on the susceptibility of nitinol to localized corrosion was examined using the cyclic potentiodynamic polarization technique. Tests were performed on mechanically polished (MP) and electropolished (EP) nitinol wire in 0.9 wt % NaCl and phosphate-buffered saline (PBS). A polarization curve was also obtained for an EP stent in the NaCl. Differences between the breakdown potential and the corrosion potential (E(corr)) and between the protection potential and E(corr) were used to evaluate the susceptibility to pitting corrosion and crevice corrosion, respectively. The type of solution and, particularly, the surface condition affected the resistance of nitinol to pitting corrosion. Both EP and MP nitinol were more susceptible to breakdown in the NaCl than in PBS, indicating that the NaCl provides a more severe test environment than does PBS. Electropolishing increased the breakdown resistance of nitinol in PBS and the NaCl, as found in previous studies with Hank's solution. Surface condition, however, did not have a significant effect on the repassivation behavior of nitinol, as is also the case with titanium. The EP wire and stent showed similar breakdown and repassivation behavior in the NaCl, suggesting that the nature of the EP surface was similar in both cases. (c) 2005 Wiley Periodicals, Inc.

Multi-Constituent Simulation of Thrombus Deposition

NASA Astrophysics Data System (ADS)

Wu, Wei-Tao; Jamiolkowski, Megan A.; Wagner, William R.; Aubry, Nadine; Massoudi, Mehrdad; Antaki, James F.

2017-02-01

In this paper, we present a spatio-temporal mathematical model for simulating the formation and growth of a thrombus. Blood is treated as a multi-constituent mixture comprised of a linear fluid phase and a thrombus (solid) phase. The transport and reactions of 10 chemical and biological species are incorporated using a system of coupled convection-reaction-diffusion (CRD) equations to represent three processes in thrombus formation: initiation, propagation and stabilization. Computational fluid dynamic (CFD) simulations using the libraries of OpenFOAM were performed for two illustrative benchmark problems: in vivo thrombus growth in an injured blood vessel and in vitro thrombus deposition in micro-channels (1.5 mm × 1.6 mm × 0.1 mm) with small crevices (125 μm × 75 μm and 125 μm × 137 μm). For both problems, the simulated thrombus deposition agreed very well with experimental observations, both spatially and temporally. Based on the success with these two benchmark problems, which have very different flow conditions and biological environments, we believe that the current model will provide useful insight into the genesis of thrombosis in blood-wetted devices, and provide a tool for the design of less thrombogenic devices.

Effects of simulated inflammation on the corrosion of 316L stainless steel.

PubMed

Brooks, Emily K; Brooks, Richard P; Ehrensberger, Mark T

2017-02-01

Stainless steel alloys, including 316L, find use in orthopaedics, commonly as fracture fixation devices. Invasive procedures involved in the placement of these devices will provoke a local inflammatory response that produces hydrogen peroxide (H 2 O 2 ) and an acidic environment surrounding the implant. This study assessed the influence of a simulated inflammatory response on the corrosion of 316L stainless steel. Samples were immersed in an electrolyte representing either normal or inflammatory physiological conditions. After 24h of exposure, electrochemical impedance spectroscopy (EIS) and inductively coupled plasma mass spectroscopy (ICPMS) were used to evaluate differences in corrosion behavior and ion release induced by the inflammatory conditions. Scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDX) were used to evaluate surface morphology and corrosion products formed on the sample surface. Inflammatory conditions, involving the presence of H 2 O 2 and an acidic pH, significantly alter the corrosion processes of 316L stainless steel, promoting aggressive and localized corrosion. It is demonstrated that particular consideration should be given to 316L stainless steel implants with crevice susceptible areas (ex. screw-head/plate interface), as those areas may have an increased probability of rapid and aggressive corrosion when exposed to inflammatory conditions. Copyright © 2016 Elsevier B.V. All rights reserved.

Femtosecond studies of protein-ligand hydrophobic binding and dynamics: human serum albumin.

PubMed

Zhong, D; Douhal, A; Zewail, A H

2000-12-19

In this contribution, we report studies of the nature of the dynamics and hydrophobic binding in protein-ligand complexes of human serum albumin with 2-(2'-hydroxyphenyl)-4-methyloxazole. With femtosecond time resolution, we examined the orientational motion of the ligand, its intrinsic nuclear motions, and the lifetime changes in the hydrophobic phase. For comparisons, with similar but chemical nanocavities, we also studied the same ligand in micelles and cyclodextrins. The hydrophobic interactions in the binding crevice are much stronger than those observed in cyclodextrins and micelles. The confined geometry restrains the nonradiative decay and significantly lengthens the excited-state lifetime. The observed dynamics over the femtosecond-to-nanosecond time scale indicate that the binding structure is rigid and the local motions of the ligand are nearly "frozen" in the protein. Another major finding is the elucidation of the directed dynamics by the protein. Proton transfer and intramolecular twisting of 2-(2'-hydroxyphenyl)-4-methyloxazole were observed to evolve along two routes: one involves the direct stretching motion in the molecular plane (approximately 200 fs) and is not sensitive to the environment; the second, less dominant, is related to the twisting motion (approximately 3 ps) of the two heterocyclic rings and drastically slows down in the protein hydrophobic pocket.

Multi-Constituent Simulation of Thrombus Deposition

PubMed Central

Wu, Wei-Tao; Jamiolkowski, Megan A.; Wagner, William R.; Aubry, Nadine; Massoudi, Mehrdad; Antaki, James F.

2017-01-01

In this paper, we present a spatio-temporal mathematical model for simulating the formation and growth of a thrombus. Blood is treated as a multi-constituent mixture comprised of a linear fluid phase and a thrombus (solid) phase. The transport and reactions of 10 chemical and biological species are incorporated using a system of coupled convection-reaction-diffusion (CRD) equations to represent three processes in thrombus formation: initiation, propagation and stabilization. Computational fluid dynamic (CFD) simulations using the libraries of OpenFOAM were performed for two illustrative benchmark problems: in vivo thrombus growth in an injured blood vessel and in vitro thrombus deposition in micro-channels (1.5 mm × 1.6 mm × 0.1 mm) with small crevices (125 μm × 75 μm and 125 μm × 137 μm). For both problems, the simulated thrombus deposition agreed very well with experimental observations, both spatially and temporally. Based on the success with these two benchmark problems, which have very different flow conditions and biological environments, we believe that the current model will provide useful insight into the genesis of thrombosis in blood-wetted devices, and provide a tool for the design of less thrombogenic devices. PMID:28218279

Multi-Constituent Simulation of Thrombus Deposition.

PubMed

Wu, Wei-Tao; Jamiolkowski, Megan A; Wagner, William R; Aubry, Nadine; Massoudi, Mehrdad; Antaki, James F

2017-02-20

In this paper, we present a spatio-temporal mathematical model for simulating the formation and growth of a thrombus. Blood is treated as a multi-constituent mixture comprised of a linear fluid phase and a thrombus (solid) phase. The transport and reactions of 10 chemical and biological species are incorporated using a system of coupled convection-reaction-diffusion (CRD) equations to represent three processes in thrombus formation: initiation, propagation and stabilization. Computational fluid dynamic (CFD) simulations using the libraries of OpenFOAM were performed for two illustrative benchmark problems: in vivo thrombus growth in an injured blood vessel and in vitro thrombus deposition in micro-channels (1.5 mm × 1.6 mm × 0.1 mm) with small crevices (125 μm × 75 μm and 125 μm × 137 μm). For both problems, the simulated thrombus deposition agreed very well with experimental observations, both spatially and temporally. Based on the success with these two benchmark problems, which have very different flow conditions and biological environments, we believe that the current model will provide useful insight into the genesis of thrombosis in blood-wetted devices, and provide a tool for the design of less thrombogenic devices.

Phylogeographical patterns of an alpine plant, Rhodiola dumulosa (Crassulaceae), inferred from chloroplast DNA sequences.

PubMed

Hou, Yan; Lou, Anru

2014-01-01

The phylogeographical patterns of Rhodiola dumulosa, an alpine plant species restrictedly growing in the crevices of rock piles, were investigated based on 4 fragments of the chloroplast genome. To cover the full distribution of R. dumulosa in China, 19 populations from 3 major disjunct distribution areas (northern, central, and northwestern China) were sampled. A total of 5881bp (after alignment) of chloroplast DNA (cpDNA) from 100 individuals were sequenced. The combined cpDNA data set yielded 36 haplotypes. The total genetic diversity of R. dumulosa was remarkably high (H(T) = 0.981). The interpopulation genetic differentiation was significantly large (F(ST) = 0.8537, P < 0.001), possibly due to the long-term isolation of the natural populations. N(ST) was significantly larger than G(ST) (P < 0.001), indicating the presence of phylogeographical structure among the R. dumulosa populations. We propose 2 migration steps to explain the current distribution of R. dumulosa in China. First, this species migrated from refugia in the Qinghai-Tibetan Plateau to northern areas via the intervening highlands when temperatures increased; second, the highland populations migrated toward the mountaintops when temperatures increased further because R. dumulosa is adapted to cold environments. During the second migration step, the common ancestral haplotypes may have been gradually lost.

An anti-hapten camelid antibody reveals a cryptic binding site with significant energetic contributions from a nonhypervariable loop

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

Fanning, Sean W.; Horn, James R.

2014-03-05

Conventional anti-hapten antibodies typically bind low-molecular weight compounds (haptens) in the crevice between the variable heavy and light chains. Conversely, heavy chain-only camelid antibodies, which lack a light chain, must rely entirely on a single variable domain to recognize haptens. While several anti-hapten VHHs have been generated, little is known regarding the underlying structural and thermodynamic basis for hapten recognition. Here, an anti-methotrexate VHH (anti-MTX VHH) was generated using grafting methods whereby the three complementarity determining regions (CDRs) were inserted onto an existing VHH framework. Thermodynamic analysis of the anti-MTX VHH CDR1-3 Graft revealed a micromolar binding affinity, while themore » crystal structure of the complex revealed a somewhat surprising noncanonical binding site which involved MTX tunneling under the CDR1 loop. Due to the close proximity of MTX to CDR4, a nonhypervariable loop, the CDR4 loop sequence was subsequently introduced into the CDR1-3 graft, which resulted in a dramatic 1000-fold increase in the binding affinity. Crystal structure analysis of both the free and complex anti-MTX CDR1-4 graft revealed CDR4 plays a significant role in both intermolecular contacts and binding site conformation that appear to contribute toward high affinity binding. Additionally, the anti-MTX VHH possessed relatively high specificity for MTX over closely related compounds aminopterin and folate, demonstrating that VHH domains are capable of binding low-molecular weight ligands with high affinity and specificity, despite their reduced interface.« less

Corrosion resistance characteristics of a Ti-6Al-4V alloy scaffold that is fabricated by electron beam melting and selective laser melting for implantation in vivo.

PubMed

Zhao, Bingjing; Wang, Hong; Qiao, Ning; Wang, Chao; Hu, Min

2017-01-01

The purpose of this study is to determine the corrosion resistance of Ti-6Al-4V alloy fabricated with electron beam melting and selective laser melting for implantation in vivo. Ti-6Al-4V alloy specimens were fabricated with electron beam melting (EBM) and selective laser melting (SLM). A wrought form of Ti-6Al-4V alloy was used as a control. Surface morphology observation, component analysis, corrosion resistance experimental results, electrochemical impedance spectroscopy, crevice corrosion resistance experimental results, immersion test and metal ions precipitation analysis were processed, respectively. The thermal stability of EBM specimen was the worst, based on the result of open circuit potential (OCP) result. The result of electrochemical impedance spectroscopy indicated that the corrosion resistance of the SLM specimen was the best under the low electric potential. The result of potentiodynamic polarization suggested that the corrosion resistance of the SLM specimen was the best under the low electric potential (<1.5V) and EBM specimen was the best under the high electric potential (>1.5V).The crevice corrosion resistance of the EBM specimen was the best. The corrosion resistance of SLM specimen was the best, based on the result of immersion test. The content of Ti, Al and V ions of EBM, SLM and wrought specimens was very low. In general, the scaffolds that were fabricated with EBM and SLM had good corrosion resistance, and were suitable for implantation in vivo. Copyright © 2016 Elsevier B.V. All rights reserved.

Botulinum neurotoxin B recognizes its protein receptor with high affinity and specificity.

PubMed

Jin, Rongsheng; Rummel, Andreas; Binz, Thomas; Brunger, Axel T

2006-12-21

Botulinum neurotoxins (BoNTs) are produced by Clostridium botulinum and cause the neuroparalytic syndrome of botulism. With a lethal dose of 1 ng kg(-1), they pose a biological hazard to humans and a serious potential bioweapon threat. BoNTs bind with high specificity at neuromuscular junctions and they impair exocytosis of synaptic vesicles containing acetylcholine through specific proteolysis of SNAREs (soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptors), which constitute part of the synaptic vesicle fusion machinery. The molecular details of the toxin-cell recognition have been elusive. Here we report the structure of a BoNT in complex with its protein receptor: the receptor-binding domain of botulinum neurotoxin serotype B (BoNT/B) bound to the luminal domain of synaptotagmin II, determined at 2.15 A resolution. On binding, a helix is induced in the luminal domain which binds to a saddle-shaped crevice on a distal tip of BoNT/B. This crevice is adjacent to the non-overlapping ganglioside-binding site of BoNT/B. Synaptotagmin II interacts with BoNT/B with nanomolar affinity, at both neutral and acidic endosomal pH. Biochemical and neuronal ex vivo studies of structure-based mutations indicate high specificity and affinity of the interaction, and high selectivity of BoNT/B among synaptotagmin I and II isoforms. Synergistic binding of both synaptotagmin and ganglioside imposes geometric restrictions on the initiation of BoNT/B translocation after endocytosis. Our results provide the basis for the rational development of preventive vaccines or inhibitors against these neurotoxins.

Electrochemical, Polarization, and Crevice Corrosion Testing of Nitinol 60, A Supplement to the ECLSS Sustaining Materials Compatibility Study

NASA Technical Reports Server (NTRS)

Lee, R. E.

2016-01-01

In earlier trials, electrochemical test results were presented for six noble metals evaluated in test solutions representative of waste liquids processed in the Environmental Control and Life Support System (ECLSS) aboard the International Space Station (ISS). Subsequently, a seventh metal, Nitinol 60, was added for evaluation and subjected to the same test routines, data analysis, and theoretical methodologies. The previous six test metals included three titanium grades, (commercially pure, 6Al-4V alloy and 6Al-4V low interstitial alloy), two nickel-chromium alloys (Inconel(RegisteredTrademark) 625 and Hastelloy(RegisteredTrademark) C276), and one high-tier stainless steel (Cronidur(RegisteredTrademark) 30). The three titanium alloys gave the best results of all the metals, indicating superior corrosive nobility and galvanic protection properties. For this current effort, the results have clearly shown that Nitinol 60 is almost as noble as titanium, being very corrosion-resistant and galvanically compatible with the other six metals electrochemically and during long-term exposure. is also quite noble as it is very corrosion resistant and galvanically compatible with the other six metals from both an electrochemical perspective and long-term crevice corrosion scenario. This was clearly demonstrated utilizing the same techniques for linear, Tafel and cyclic polarization, and galvanic coupling of the metal candidate as was done for the previous study. The high nobility and low corrosion susceptibility for Nitinol 60 appear to be intermediate to the nickel/chromium alloys and the titanium metals with indications that are more reflective of the titanium metals in terms of general corrosion and pitting behavior.

Mechanical Design Engineering Enabler Project wheel and wheel drives

NASA Technical Reports Server (NTRS)

Nutt, Richard E.; Couch, Britt K.; Holley, John L., Jr.; Garris, Eric S.; Staut, Paul V.

1992-01-01

Our group was assigned the responsibility of designing the wheel and wheel drive system for a proof-of-concept model of the lunar-based ENABLER. ENABLER is a multi-purpose, six wheeled vehicle designed to lift and transport heavy objects associated with the construction of a lunar base. The resulting design was based on the performance criteria of the ENABLER. The drive system was designed to enable the vehicle to achieve a speed of 7 mph on a level surface, climb a 30 percent grade, and surpass a one meter high object and one meter wide crevice. The wheel assemblies were designed to support the entire weight of the vehicle on two wheels. The wheels were designed to serve as the main component of the vehicle's suspension and will provide suitable traction for lunar-type surfaces. The expected performance of the drive system for the ENABLER was influenced by many mechanical factors. The expected top speed on a level sandy surface is 4 mph instead of the desired 7 mph. This is due to a lack of necessary power at the wheels. The lack of power resulted from dimension considerations that allowed only an eight horsepower engine and also from mechanical inefficiencies of the hydraulic system. However, the vehicle will be able to climb a 30 percent grade, surpass a one meter high object and one meter wide crevice. The wheel assemblies will be able to support the entire weight of the vehicle on two wheels. The wheels will also provide adequate suspension for the vehicle and sufficient traction for lunar-type surfaces.

Entropic depletion in colloidal suspensions and polymer liquids: Role of nanoparticle surface topography

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

Banerjee, Debapriya; Yang, Jian; Schweizer, Kenneth S.

2015-01-01

Here, we employ a hybrid Monte Carlo plus integral equation theory approach to study how dense fluids of small nanoparticles or polymer chains mediate entropic depletion interactions between topographically rough particles where all interaction potentials are hard core repulsion. The corrugated particle surfaces are composed of densely packed beads which present variable degrees of controlled topographic roughness and free volume associated with their geometric crevices. This pure entropy problem is characterized by competing ideal translational and (favorable and unfavorable) excess entropic contributions. Surface roughness generically reduces particle depletion aggregation relative to the smooth hard sphere case. However, the competition betweenmore » ideal and excess packing entropy effects in the bulk, near the particle surface and in the crevices, results in a non-monotonic variation of the particle-monomer packing correlation function as a function of the two dimensionless length scale ratios that quantify the effective surface roughness. As a result, the inter-particle potential of mean force (PMF), second virial coefficient, and spinodal miscibility volume fraction vary non-monotonically with the surface bead to monomer diameter and particle core to surface bead diameter ratios. A miscibility window is predicted corresponding to an optimum degree of surface roughness that completely destroys depletion attraction resulting in a repulsive PMF. Variation of the (dense) matrix packing fraction can enhance or suppress particle miscibility depending upon the amount of surface roughness. Connecting the monomers into polymer chains destabilizes the system via enhanced contact depletion attraction, but the non-monotonic variations with surface roughness metrics persist.« less

Micromorphology of two prehistoric ritual burials from Yemen, and considerations on methodological aspects of sampling the burial matrix - work in progress

NASA Astrophysics Data System (ADS)

Usai, Maria-Raimonda; Brothwell, Don; Buckley, Stephen; Ai-Thour, Kalid; Canti, Matthew

2010-05-01

Introduction In the central area of Yemen, two burial sites placed high in the crevices of vertical cliff face of Cretaceous sandstone (Tawilah Group) provided evidence of human remains and yielded burial soils. Radiocarbon dating indicated c.2500-2900 years BP for the burials. In other local comparable sites the deep horizontal crevices yielded Bronze Age human remains, in exceptional state of preservation Questions: What was the nature of the burial matrix? Are other human influences superimposed on the soils derived from it? Is it simply decomposed crevice rock, scraped together at the time of burial, or the result of a more complex burial practice? Such questions are also relevant to a variety of other burials of different periods and world regions. Methods Seven matrix samples from Cliff Burials (A) Talan (Layers 4,10,12,14,18,20 and 22, from top to bottom) and (B) Shiban Kawkaban (Layer 1 and 9) were analysed with micromorphology, supplemented by SEM microprobe, X-ray diffraction, gas chromatography/mass spectrometry. Results Cliff Burial Site Talan. The presence of cholesterol was confirmed in the lower sample. The second layer contained darker earth with fibrous plant material. A hard calcareous upper capping contrasted with the other levels of matrix, and it displayed a highly birefingent material with a significant component of uric acid. The other levels had variable organic content and plant inclusions, and possibly pollen. In Layer 10, aromatic acids indicative of balsam and sugar markers suggested plant gum. Cholesterol was the major sterol in Layers 10 and 22, but whilst in Layer 10 its oxidation products were present and cholestanol was abundant as normally in soils, it was only a minor component of Layer 22 where, rather, a significant amount of coprostanol indicated faecal input, and cholesterol oxidation products were absent. Cliff Burial Site Shiban Kawkaban. Although no stratification was visible to the naked eye, variation was observed at a micromorphological level. Layer 1 included mineral, bone, plant and soil-like fragments, with leaf and woody tissue, including vascular parts and seeds. Layer 9 included plant tissue, hair, seeds and some fly puparia. Comments Layering of the burial matrix in the Yemeni burials was unexpected and the burial matrix in one case was very clearly not the result of natural soil forming processes within the rock crevice. In Burial Site A the hard upper capping contained uric acid-rich deposits embedding organic tissue. This sample could possibly represent an intentional ‘plaster layer' including plant, hair and seed fragments. The abundant cholesterol confirms an animal/human origin within the matrix of Layers 10 and 22, and the stanol and bile acid distributions unequivocally confirm a human origin, despite the lack of any physical human remains. Microprobe analysis indicated that the hard cup of Burial 1 contained K, Si, Al, Cu, Mg, S, Fe and Na with amounts fluctuating relatively to depth. No special significance can be placed on the differences. This study calls attention to a neglected aspect of burial archaeology: grave infillings can no longer be assumed to be simply the return of material removed for the burial, but may be influenced by other factors. Through micromorphology, decomposed wood, shroud or other textiles or skins and hair can be detected and, if local rituals influenced the way materials were returned into the grave, then this also deserves investigation. A new ERC-funded project (Title: "Interred with their bones", acronym: "InterArChive") tackles these issues (please see separate poster). Acknowledgments We thank Allan Hall, Brendan Keely, Trevor Dransfield, Andrea Vacca and Cagliari University

In vitro simulation of fretting-corrosion in hip implant modular junctions: The influence of pH.

PubMed

Royhman, Dmitry; Patel, Megha; Jacobs, Joshua J; Wimmer, Markus A; Hallab, Nadim J; Mathew, Mathew T

2018-02-01

The fretting-corrosion behavior of mixed metal contacts is affected by various mechanical and electrochemical parameters. Crevice conditions at the junction and patient-specific pathologies can affect the pH of the prosthetic environment. The main objective of this study is to understand the effect of pH variation at the stem/head junction of the hip implant under fretting corrosion exposure. We hypothesized that pH will have a significant influence on the fretting-corrosion behavior hip implant modular junctions. A custom-made setup was used to evaluate the fretting corrosion behavior of hip implant modular junctions. A Newborn calf serum solution (30 g/L protein content) was used to simulate the synovial fluid environment. A sinusoidal fretting motion, with a displacement amplitude of +50 µm, was applied to the Ti alloy rod. The effects of pathology driven, periprosthetic pH variation were simulated at four different pH levels (3.0, 4.5, 6.0 and 7.6). Electrochemical and mechanical properties were evaluated before, during, and after the applied fretting motion. The impedance of the system was increased in response to the fretting motion. The hysteresis tangential load/displacement behavior was not affected by pH level. The worn surfaces of CoCrMo pins exhibited the presence of tribolayer or organic deposits, in the pH 4.5 group, which may explain the lower drop in potential and mass loss observed in that group. Mechanically dominated wear mechanisms, namely, adhesive wear was shown in the pH 7.6 group, which may account for a higher potential drop and metal content loss. This study suggests that the fretting-corrosion mechanisms in hip implant are affected by the pH levels of the surrounding environment and patient-specific factors. Copyright © 2017. Published by Elsevier Ltd.

The Role of Passive Film Growth Kinetics and Properties in Stress Corrosion and Crevice Corrosion Susceptibility

DTIC Science & Technology

1975-10-01

Kleinzack-Mathieu Cl. Mertens, J. Meunier, Cl. Vanlengenhaghe, L. de Munck, L. Laureys , L. N. Nellmans, and M . Warzu, Corrosion Science, 3, 239 (1963). 10) H...312O448 DEPARTMENT OF COMMERCE 11. CoMfact/Grat No. WASHINGTON. D.C. 20234 M 1 mRO36-082 12. Spoasoring Organizstion N~me and Complete Address (Street...Ill. Undw Swnay Dr. 111"y Alu-Juhws. AsnluaM ScWaty fr Salome and T0e@* M /WY NATIONAL UMAU OF STANDAWS. Ernest Ambler. Acting Dimwt PART I (To be

Performance and combustion characteristics of direct-injection stratified-charge rotary engines

NASA Technical Reports Server (NTRS)

Nguyen, Hung Lee

1987-01-01

Computer simulations of the direct-injection stratified-charge (DISC) Wankel engine have been used to calculate heat release rates and performance and efficiency characteristics of the 1007R engine. Engine pressure data have been used in a heat release analysis to study the effects of heat transfer, leakage, and crevice flows. Predicted engine performance data are compared with experimental test data over a range of engine speeds and loads. An examination of methods to improve the performance of the Wankel engine with faster combustion, reduced leakage, higher compression ratio, and turbocharging is presented.

Book review of Littler DM. Littler MM (2000) Caribbean Reef Plants An Identification Guide to the Reef Plants of the Caribbean, Bahamas, Florida and Gulf of Mexico

NASA Astrophysics Data System (ADS)

Zuschin, M.; Hohenegger, J.; Steininger, F.

2001-09-01

Information on spatial variability and distribution patterns of organisms in coral reef environments is necessary to evaluate the increasing anthropogenic disturbance of marine environments (Richmond 1993; Wilkinson 1993; Dayton 1994). Therefore different types of subtidal, reef-associated hard substrata (reef flats, reef slopes, coral carpets, coral patches, rock grounds), each with different coral associations, were investigated to determine the distribution pattern of molluscs and their life habits (feeding strategies and substrate relations). The molluscs were strongly dominated by taxa with distinct relations to corals, and five assemblages were differentiated. The Dendropoma maxima assemblage on reef flats is a discrete entity, strongly dominated by this encrusting and suspension-feeding gastropod. All other assemblages are arranged along a substrate gradient of changing coral associations and potential molluscan habitats. The Coralliophila neritoidea- Barbatia foliata assemblage depends on the presence of Porites and shows a dominance of gastropods feeding on corals and of bivalves associated with living corals. The Chamoidea- Cerithium spp. assemblage on rock grounds is strongly dominated by encrusting bivalves. The Drupella cornus-Pteriidae assemblage occurs on Millepora- Acropora reef slopes and is strongly dominated by bivalves associated with living corals. The Barbatia setigera- Ctenoides annulata assemblage includes a broad variety of taxa, molluscan life habits and bottom types, but occurs mainly on faviid carpets and is transitional among the other three assemblages. A predicted degradation of coral coverage to rock bottoms due to increasing eutrophication and physical damage in the study area (Riegl and Piller 2000) will result in a loss of coral-associated molluscs in favor of bivalve crevice dwellers in dead coral heads and of encrusters on dead hard substrata.

Molluscan assemblages on coral reefs and associated hard substrata in the northern Red Sea

NASA Astrophysics Data System (ADS)

Zuschin, M.; Hohenegger, J.; Steininger, F.

2001-09-01

Information on spatial variability and distribution patterns of organisms in coral reef environments is necessary to evaluate the increasing anthropogenic disturbance of marine environments (Richmond 1993; Wilkinson 1993; Dayton 1994). Therefore different types of subtidal, reef-associated hard substrata (reef flats, reef slopes, coral carpets, coral patches, rock grounds), each with different coral associations, were investigated to determine the distribution pattern of molluscs and their life habits (feeding strategies and substrate relations). The molluscs were strongly dominated by taxa with distinct relations to corals, and five assemblages were differentiated. The Dendropoma maxima assemblage on reef flats is a discrete entity, strongly dominated by this encrusting and suspension-feeding gastropod. All other assemblages are arranged along a substrate gradient of changing coral associations and potential molluscan habitats. The Coralliophila neritoidea- Barbatia foliata assemblage depends on the presence of Porites and shows a dominance of gastropods feeding on corals and of bivalves associated with living corals. The Chamoidea- Cerithium spp. assemblage on rock grounds is strongly dominated by encrusting bivalves. The Drupella cornus-Pteriidae assemblage occurs on Millepora- Acropora reef slopes and is strongly dominated by bivalves associated with living corals. The Barbatia setigera- Ctenoides annulata assemblage includes a broad variety of taxa, molluscan life habits and bottom types, but occurs mainly on faviid carpets and is transitional among the other three assemblages. A predicted degradation of coral coverage to rock bottoms due to increasing eutrophication and physical damage in the study area (Riegl and Piller 2000) will result in a loss of coral-associated molluscs in favor of bivalve crevice dwellers in dead coral heads and of encrusters on dead hard substrata.

Plasma inactivation of microorganisms on sprout seeds in a dielectric barrier discharge.

PubMed

Butscher, Denis; Van Loon, Hanne; Waskow, Alexandra; Rudolf von Rohr, Philipp; Schuppler, Markus

2016-12-05

Fresh produce is frequently contaminated by microorganisms, which may lead to spoilage or even pose a threat to human health. In particular sprouts are considered to be among the most risky foods sold at retail since they are grown in an environment practically ideal for growth of bacteria and usually consumed raw. Because heat treatment has a detrimental effect on the germination abilities of sprout seeds, alternative treatment technologies need to be developed for microbial inactivation purposes. In this study, non-thermal plasma decontamination of sprout seeds is evaluated as a promising option to enhance food safety while maintaining the seed germination capabilities. In detail, investigations focus on understanding the efficiency of non-thermal plasma inactivation of microorganisms as influenced by the type of microbial contamination, substrate surface properties and moisture content, as well as variations in the power input to the plasma device. To evaluate the impact of these parameters, we studied the reduction of native microbiota or artificially applied E. coli on alfalfa, onion, radish and cress seeds exposed to non-thermal plasma in an atmospheric pressure pulsed dielectric barrier discharge streamed with argon. Plasma treatment resulted in a maximum reduction of 3.4 logarithmic units for E. coli on cress seeds. A major challenge in plasma decontamination of granular food products turned out to be the complex surface topology, where the rough surface with cracks and crevices can shield microorganisms from plasma-generated reactive species, thus reducing the treatment efficiency. However, improvement of the inactivation efficiency was possible by optimizing substrate characteristics such as the moisture level and by tuning the power supply settings (voltage, frequency) to increase the production of reactive species. While the germination ability of alfalfa seeds was considerably decreased by harsh plasma treatment, enhanced germination was observed under mild conditions. In conclusion, the results from this study indicate that cold plasma treatment represents a promising technology for inactivation of bacteria on seeds used for sprout production while preserving their germination properties. Copyright © 2016 Elsevier B.V. All rights reserved.

Crystal structure of the human cytosolic sialidase Neu2. Evidence for the dynamic nature of substrate recognition.

PubMed

Chavas, Leonard M G; Tringali, Cristina; Fusi, Paola; Venerando, Bruno; Tettamanti, Guido; Kato, Ryuichi; Monti, Eugenio; Wakatsuki, Soichi

2005-01-07

Gangliosides play key roles in cell differentiation, cell-cell interactions, and transmembrane signaling. Sialidases hydrolyze sialic acids to produce asialo compounds, which is the first step of degradation processes of glycoproteins and gangliosides. Sialidase involvement has been implicated in some lysosomal storage disorders such as sialidosis and galactosialidosis. Neu2 is a recently identified human cytosolic sialidase. Here we report the first high resolution x-ray structures of mammalian sialidase, human Neu2, in its apo form and in complex with an inhibitor, 2-deoxy-2,3-dehydro-N-acetylneuraminic acid (DANA). The structure shows the canonical six-blade beta-propeller observed in viral and bacterial sialidases with its active site in a shallow crevice. In the complex structure, the inhibitor lies in the catalytic crevice surrounded by ten amino acids. In particular, the arginine triad, conserved among sialidases, aids in the proper positioning of the carboxylate group of DANA within the active site region. The tyrosine residue, Tyr(334), conserved among mammalian and bacterial sialidases as well as in viral neuraminidases, facilitates the enzymatic reaction by stabilizing a putative carbonium ion in the transition state. The loops containing Glu(111) and the catalytic aspartate Asp(46) are disordered in the apo form but upon binding of DANA become ordered to adopt two short alpha-helices to cover the inhibitor, illustrating the dynamic nature of substrate recognition. The N-acetyl and glycerol moieties of DANA are recognized by Neu2 residues not shared by bacterial sialidases and viral neuraminidases, which can be regarded as a key structural difference for potential drug design against bacteria, influenza, and other viruses.

Biological responses of Crested and Least auklets to volcanic destruction of nesting habitat in the Aleutian Islands, Alaska

USGS Publications Warehouse

Drew, Gary S.; Piatt, John F.; Williams, Jeffrey C.

2018-01-01

Crested Auklets (Aethia cristatella) and Least Auklets (A. pusilla) are crevice-nesting birds that breed in large mixed colonies at relatively few sites in the Aleutian Island archipelago, Bering Sea, Gulf of Alaska, and Sea of Okhotsk. Many of these colonies are located on active volcanic islands. The eruption of Kasatochi volcano, in the central Aleutians, on August 7, 2008, completely buried all crevice-nesting seabird habitat on the island. This provided an opportunity to examine the response of a large, mixed auklet colony to a major geological disturbance. Time-lapse imagery of nesting habitat indicated that both species returned to the largest pre-eruption colony site for several years, but subsequently abandoned it within 5 yr after the eruption. In 2010, a rockfall site in a cove north of the old colony site began to accumulate talus, and groups of auklets were observed using the site in 2011. Use of the new colony appeared to coincide with the abandonment of the old colony site by both species, though surface counts suggested that Least Auklets shifted to the new colony sooner than Crested Auklets. At-sea surveys of seabirds before and after the eruption indicated that both Crested and Least auklets shifted their at-sea distributions from the waters around Kasatochi Island to nearby Koniuji Island. In combination, at-sea counts and colony time-lapse imagery indicated that Crested and Least auklets using Kasatochi responded to the volcanic disturbance and complete loss of nesting habitat at the main colony on Kasatochi with dispersal either to newly created habitat on Kasatochi or to an alternate colony on a nearby island.

Comparative skull anatomy of terrestrial and crevice-dwelling Trachylepis skinks (Squamata: Scincidae) with a survey of resources in scincid cranial osteology.

PubMed

Paluh, Daniel J; Bauer, Aaron M

2017-01-01

Skinks account for more than 25% of all lizard species; however, representatives of fewer than a quarter of all species have been characterized osteologically. All but a few of the available cranial descriptions concentrate solely on characters that can be seen externally on the intact skull. Mabuyid skinks of the genus Trachylepis are the dominant, fully limbed skinks in Sub-Saharan Africa, and nearly all species have the same generalized body plan. Although a few rock crevice-dwelling species possess slight body depression, extreme dorsoventral depression is observed only in Trachylepis laevis. We investigated the detailed skull anatomy of three Trachylepis skinks (T. laevis, T. sulcata, and T. gonwouoi, a recently described species allied to T. affinis) using high-resolution X-ray micro-computed tomography. Our goals were to review the scincid cranial osteology literature in a phylogenetic context, provide a detailed anatomical atlas for the mabuyid lineage, and investigate the morphological adaptations of the highly modified T. laevis. Our results demonstrate that there is significant morphological variation between these three taxa, including the loss and fusion of structures, as well as changes in the shape, scale, and relationship between individual elements. Trachylepis laevis possesses several osteological modifications that have produced a reducton in head depth that are likely functional consequences of extreme rupicolous habits, including a flat skull roof, many strongly recumbent elements, and a depressed neurocranium.We hypothesize these modifications may correspond to descreased bite force and increased capabilities of cranial kinesis. Our study is the first element-by-element description of a skink using computed tomography technology.

Total reflection X-ray fluorescence analysis of oral fluids of women affected by osteoporosis and osteopenia

NASA Astrophysics Data System (ADS)

Sánchez, Héctor Jorge; Valentinuzzi, María Cecilia; Grenón, Miram; Abraham, José

2008-12-01

Osteoporosis is a disease characterized by low bone mass and microarchitectural deterioration of bone tissue, leading to bone fragility and an increased susceptibility to fractures; the early stage of decreased bone density is called osteopenia. More than 200 million people are affected and about 50% of post-menopausic women are expected to develop the disease. Osteoporosis, osteopenia and periodontal disease have in common several risk factors, being hyperthyroidism and smoking habits the most important ones. There is scarce information in the literature about the association between periodontal disease and osteoporosis and/or osteopenia. Some works suggest that osteoporotic women are susceptible to a higher loss of periodontal insertion, alveolar bones, and teeth. Thirty adult post-menopausic women were studied; some of them were healthy (control group) and the rest of them were undergoing some stage of osteoporosis or osteopenia. All the subjects were healthy, non-smokers, not having dental implants, and with communitarian periodontal index higher than 1(CPI > 1). Samples of saliva and gingival crevice fluid were extracted with calibrated micro-capillaries and deposited on Si reflectors. Known amounts of Ga were added to the samples in order to act as internal standard for quantification by the total reflection x-ray fluorescence technique. Experimental concentrations of several elements (P, S, Cl, K, Ca, Cr, Fe, NI, Cu, and Zn) were determined. The concentration of some elements in saliva showed different behavior as compared to gingival crevice fluid. Some critical elements of bone composition, such as Ca and Zn, present very distinguishable behavior. Improvements in the statistics are required for a better assessment of a routine method and to establish some correlation with periodontal disease. TXRF seems to be a promising method to evaluate the evolution of osteoporosis.

Multi-locus DNA sequence data reveal a history of deep cryptic vicariance and habitat-driven convergence in the desert night lizard Xantusia vigilis species complex (Squamata: Xantusiidae).

PubMed

Leavitt, Dean H; Bezy, Robert L; Crandall, Keith A; Sites, Jack W

2007-11-01

The lizard genus Xantusia of southwestern North America has received recent attention in relation to delimiting species. Using more than 500 lizards from 156 localities, we further test hypothesized species boundaries and clarify phylogeographical patterns, particularly in regions of potential secondary contact. We sequenced the entire mitochondrial cytochrome b gene for every lizard in the study, plus a second mitochondrial DNA (mtDNA) region and two nuclear introns for subsets of the total sample. Phylogenetic analyses of the mtDNA recover a well-resolved, novel hypothesis for species in the Xantusia vigilis complex. The nuclear DNA (nDNA) data provide independent support for the recognition of X. arizonae, X. bezyi and X. wigginsi. Differences between the respective mtDNA and nDNA topologies result from either the effects of lineage sorting or ancient introgression. Nuclear data confirm the inference that some populations of X. vigilis in northwestern Arizona converged on rock-crevice-dwelling morphology and are not X. arizonae with an introgressed X. vigilis mtDNA genome. The historical independence of ancient cryptic lineages of Xantusia in southern California is also corroborated, though limited introgression is detected. Our proposed biogeographical scenario indicates that diversification of this group was driven by vicariance beginning in the late Miocene. Additionally, Pleistocene climatical changes influenced Xantusia distribution, and the now inhospitable Colorado Desert previously supported night lizard presence. The current taxonomy of the group likely underestimates species diversity within the group, and our results collectively show that while convergence on the rock-crevice-dwelling morphology is one hallmark of Xantusia evolution, morphological stasis is paradoxically another.

Comparative skull anatomy of terrestrial and crevice-dwelling Trachylepis skinks (Squamata: Scincidae) with a survey of resources in scincid cranial osteology

PubMed Central

Bauer, Aaron M.

2017-01-01

Skinks account for more than 25% of all lizard species; however, representatives of fewer than a quarter of all species have been characterized osteologically. All but a few of the available cranial descriptions concentrate solely on characters that can be seen externally on the intact skull. Mabuyid skinks of the genus Trachylepis are the dominant, fully limbed skinks in Sub-Saharan Africa, and nearly all species have the same generalized body plan. Although a few rock crevice-dwelling species possess slight body depression, extreme dorsoventral depression is observed only in Trachylepis laevis. We investigated the detailed skull anatomy of three Trachylepis skinks (T. laevis, T. sulcata, and T. gonwouoi, a recently described species allied to T. affinis) using high-resolution X-ray micro-computed tomography. Our goals were to review the scincid cranial osteology literature in a phylogenetic context, provide a detailed anatomical atlas for the mabuyid lineage, and investigate the morphological adaptations of the highly modified T. laevis. Our results demonstrate that there is significant morphological variation between these three taxa, including the loss and fusion of structures, as well as changes in the shape, scale, and relationship between individual elements. Trachylepis laevis possesses several osteological modifications that have produced a reducton in head depth that are likely functional consequences of extreme rupicolous habits, including a flat skull roof, many strongly recumbent elements, and a depressed neurocranium.We hypothesize these modifications may correspond to descreased bite force and increased capabilities of cranial kinesis. Our study is the first element-by-element description of a skink using computed tomography technology. PMID:28902864

The distribution of chlorpyrifos following a crack and crevice type application in the US EPA Indoor Air Quality Research House

NASA Astrophysics Data System (ADS)

Stout, D. M.; Mason, M. A.

A study was conducted in the US EPA Indoor Air Quality (IAQ) Research House to determine the spatial and temporal distribution of chlorpyrifos following a professional crack and crevice application in the kitchen. Following the application, measurements were made in the kitchen, den and master bedroom over 21 days. Airborne concentrations were collected using both polyurethane foam (PUF) and the OSHA versatile sampler composed of XAD and PUF media located in tandem. Measured airborne concentrations were similar for the two samplers and were higher in the three rooms following the application. The highest measured concentrations were reached during the initial 24-h following application; concentrations subsequently declined over the 21-day study period to levels slightly above background. Spatial and temporal distributions onto surfaces were measured using 10-cm 2 rayon deposition coupons located on the floor. Sections were cut from existing carpet to determine the total extractable residues. Chlorpyrifos was measured from all matrixes in the kitchen, den and bedroom and the data shows the transport of airborne residues from the point of application to remote locations in the house. The findings are compared and discussed relative to another study conducted in which total release aerosols containing chlorpyrifos were activated in the IAQ research house and the resulting distributions evaluated. For both studies dose estimates were constructed for the exposure pathways using the Stochastic Human Exposure and Dose Estimation Model for pesticides. The United States Environmental Protection Agency has been mandated to examine children's exposure to environmental pollutants such as pesticides. This research specifically reduces uncertainties associated with estimating children's potential exposures to residentially applied pesticides and provides inputs to further evaluate and validate residential exposure models which might be used to reduce exposures and perform risk assessments.

Insight into the binding modes of Lassa nucleoprotein complexed with ssRNA by molecular dynamic simulations and free energy calculations.

PubMed

Zhang, Ying; Chen, Hang; Han, Ju-Guang

2015-01-01

Lassa virus (LASV), an arenavirus known to be responsible for a severe hemorrhagic fever, causes thousands of deaths annually and there is no effective vaccine for it so far. The nucleoprotein (NP) of LASV plays an essential role in the replication and transcription of the viral genome. Recent research shows that viral RNA binds in a deep crevice located within the N-terminal domain of NP and suggests a gating mechanism in which NP transforms from a "closed" position to an "open" position to bind RNA. To characterize the molecular mechanisms of how RNA binds to N-terminal domain of NP, two molecular dynamic (MD) simulations of RNA-binding structure and RNA-free structure have been performed. The simulation results show that an important helix α6 interacts with RNA in the "open" conformation, while helix α6 rotates toward the binding crevice and reduces the space of RNA-binding pocket in the "closed" conformation; it appears that helix α6 would clash with RNA while NP is in a "closed" state. In addition, to characterize the role of residues involved in the binding of RNA, the MD simulations of the double-mutant (W164A/F176A) and the single-mutant (G243P) RNA-binding NP complexes have been performed. Our MD simulations and molecular mechanics-generalized born surface area (MM-GBSA) energy calculations exhibit that the three mutant residues increase the binding affinity. Furthermore, we infer that the defect of the replication and transcription of viral genome is possibly due to the change of structural integrity rather than the reduction of RNA-binding affinity.

Development of sustained release antipsychotic tablets using novel polysaccharide isolated from Delonix regia seeds and its pharmacokinetic studies

PubMed Central

Krishnaraj, Kaliaperumal; Chandrasekar, Mulla Joghi Nanjan; Nanjan, Mulla Joghi; Muralidharan, Selvadurai; Manikandan, Duraikannu

2011-01-01

A natural polysaccharide was isolated from the seeds of Delonix regia. The isolated polysaccharide could maintain aqueous equilibrium between the dosage form and the surrounding medium due to its massive competence of water absorption (80.72%) and swelling index (266.7%). The Scanning Electron Micrograph of a polysaccharide exhibits rough surface with pores and crevices, hence, the drug release will be retarded because of the drug particles entrapment in the pores and crevices. Further, the surface tension of polysaccharide is higher than that of water, which may facilitate sustained release of drugs from dosage forms. An antipsychotic drug, quetiapine fumarate has a short half-life of 6 h and administered multiple times per day. Hence the quetiapine fumarate oral sustained release tablets were formulated using this polysaccharide in the concentration of 5–30% to avoid the side effects and increase patient compliance. Dissolution of the developed tablets with 25% polysaccharide content showed a better release profile than the other batches (5–20%) at the end of 12 h. The strong matrix complex has low solubility in water, it does not dissolve rapidly and the drug continues to diffuse through the gel layer at a consistent rate. Drug release from the matrix tablets follows matrix type except F-4 and F-5 which follow first order and Hix.crow type. The bioavailability study was carried out using healthy male New Zealand white rabbits that show the AUC(0–inf) value for developed SR tablets is 1.44 times higher than the reference thus, indicating more efficient and sustained drug delivery capable of maintaining plasma drug levels better. PMID:24115903

SCC analysis of Alloy 600 tubes from a retired steam generator

NASA Astrophysics Data System (ADS)

Hwang, Seong Sik; Kim, Hong Pyo

2013-09-01

Steam generators (SG) equipped with Alloy 600 tubes of a Korean nuclear power plants were replaced with a new one having Alloy 690 tubes in 1998 after 20 years of operation. To set up a guide line for an examination of the other SG tubes, a metallographic examination of the defected tubes was carried out. A destructive analysis on 71 tubes was addressed, and a relation among the stress corrosion crack (SCC) defect location, defect depth, and location of the sludge pile was obtained. Tubes extracted from the retired SG were transferred to a hot laboratory. Detailed nondestructive analysis examinations were taken again at the laboratory, and the tubes were then destructively examined. The types and sizes of the cracks were characterized. The location and depth of the SCC were evaluated in terms of the location and height of the sludge. Most axial cracks were in the sludge pile, whereas the circumferential ones were around the top of the tube sheet (TTS) or below the TTS. Average defect depth of the axial cracks was deeper than that of the circumferential ones. Axial cracks at tube support plate (TSP) seem to be related with corrosion/sludge in crevice like at the TTS region. Circumferential cracks at TSP seem to be caused by tube denting at the upper part of the TSP. Tubes not having clear ECT signals for quantifying an ECT data-base. Tubes having no ECT signal. Tubes with a large ECT signal. Tubes with various types and sizes of flaws (primary water stress corrosion cracking (PWSCC), outside diameter stress corrosion cracking (ODSCC), Pit). Tubes with distinct PWSCC or ODSCC. Tubes were extracted from the RSG based on the field ECT with the criteria, and transferred to a hot laboratory at the Korea Atomic Energy Research Institute (KAERI) for destructive examination. A comprehensive ECT inspection was performed again at the hot laboratory to confirm the location of the cracks obtained from a field inspection. These exact locations of the defects were marked on the tube specimens for subsequent destructive examinations.Metallography on a tube section was examined by standard metallographic techniques. The mounted specimens were ground and polished. For a chemical activation of the polished surface, the samples were soaked in hydrochloric acid for 20 s then followed by cleaning in methanol. Chemical etching in a bromine etchant (98% Methanol + 2% Bromine) was applied for 3 to 4 s in an ultrasound cleaner.Destructive examinations were carried out using the procedures in accordance with the Electric Power Research Institute (EPRI) tube examination guidelines [2]. The types of defects were characterized and their sizes were measured using a high magnification contact camera and a scanning electron microscope (SEM). The surface deposit compositions on the outer diameter of the tubes were also analyzed using energy dispersive X-ray spectroscopy (EDS). The relation among the SCC defect location, defect depth, and sludge height was explored. Denting, pitting, PWSCC and ODSCC were observed on the RSG tubes as time went on. The analyzed Alloy 600 tube showed a typical LTMA microstructure, and the severe SCC of the RSG was attributed to the microstructure and slightly alkaline crevice environment in some respects. Most axial cracks were observed inside the sludge pile up region, which suggests that sludge may have a role in accelerating the growth of the axial cracks. No correlation was seen in the circumferential cracks and sludge pile, and dents in the tube sheet and phosphate chemistry might cause OD circumferential cracks at the TTS region. The average depth of the axial cracks was higher than that of the circumferential cracks. Axial ID cracks 4 mm long or over at the TTS showed 90%-100% tube wall penetration. On the contrary, the length of the axial OD cracks was not closely related with the depth OD axial cracks around the TSP appeared to be much shallower than those of the TTS region. This implies that the same length of TSP region cracks may have higher structural safety than that of cracks of the TTS region.

Encrustation of inarticulate brachiopods on scaphitid ammonites and inoceramid bivalves from the Upper Cretaceous U. S. Western Interior

NASA Astrophysics Data System (ADS)

Landman, Neil H.; Slattery, Joshua S.; Harries, Peter J.

2016-12-01

The inarticulate brachiopod Discinisca is a rare faunal element in the Upper Cretaceous of the U.S. Western Interior. We report two occurrences of encrustation of Discinisca on a scaphitid ammonite (scaphite) and several inoceramids from the lower Maastrichtian Baculites baculus/Endocostea typica Biozones of the Pierre Shale at two localities. Six specimens of Discinisca are present on a single specimen of Hoploscaphites crassus from east-central Montana. They occur along the furrow at the mature apertural margin. Because the brachiopods are restricted to the margin and do not occur on the rest of the shell, it is likely that they encrusted the ammonite during its lifetime. If so, this implies that the soft body of the scaphite did not cover the outside surface of the aperture, leaving this area vulnerable to epizoan attachment. A total of 13 specimens of Discinisca are also present on four specimens of Cataceramus? barabini from east-central Wyoming. The brachiopods occur in crevices on the outside of the shells and may have encrusted the inoceramids after their death as the shells began to break down and delaminate, resulting from the decomposition of the organic matrix holding them together. Based on the faunal assemblages at both localities, the presence of Discinisca may indicate environments with either low oxygen levels and/or few predators or competitors.

Species-specific differences in adaptive phenotypic plasticity in an ecologically relevant trophic trait: hypertrophic lips in Midas cichlid fishes.

PubMed

Machado-Schiaffino, Gonzalo; Henning, Frederico; Meyer, Axel

2014-07-01

The spectacular species richness of cichlids and their diversity in morphology, coloration, and behavior have made them an ideal model for the study of speciation and adaptive evolution. Hypertrophic lips evolved repeatedly and independently in African and Neotropical cichlid radiations. Cichlids with hypertrophic lips forage predominantly in rocky crevices and it has been hypothesized that mechanical stress caused by friction could result in larger lips through phenotypic plasticity. To test the influence of the environment on the size and development of lips, we conducted a series of breeding and feeding experiments on Midas cichlids. Full-sibs of Amphilophus labiatus (thick-lipped) and Amphilophus citrinellus (thin-lipped) each were split into a control group which was fed food from the water column and a treatment group whose food was fixed to substrates. We found strong evidence for phenotypic plasticity on lip area in the thick-lipped species, but not in the thin-lipped species. Intermediate phenotypic values were observed in hybrids from thick- and thin-lipped species reared under "control" conditions. Thus, both a genetic, but also a phenotypic plastic component is involved in the development of hypertrophic lips in Neotropical cichlids. Moreover, species-specific adaptive phenotypic plasticity was found, suggesting that plasticity is selected for in recent thick-lipped species. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

Hunting behavior of a marine mammal beneath the antarctic fast Ice

PubMed

Davis; Fuiman; Williams; Collier; Hagey; Kanatous; Kohin; Horning

1999-02-12

The hunting behavior of a marine mammal was studied beneath the Antarctic fast ice with an animal-borne video system and data recorder. Weddell seals stalked large Antarctic cod and the smaller subice fish Pagothenia borchgrevinki, often with the under-ice surface for backlighting, which implies that vision is important for hunting. They approached to within centimeters of cod without startling the fish. Seals flushed P. borchgrevinki by blowing air into subice crevices or pursued them into the platelet ice. These observations highlight the broad range of insights that are possible with simultaneous recordings of video, audio, three-dimensional dive paths, and locomotor effort.

Method and apparatus for remote tube crevice detection by current and voltage probe resistance measurement

DOEpatents

Kikta, Thomas J.; Mitchell, Ronald D.

1992-01-01

A method and apparatus for determining the extent of contact between an electrically conducting tube and an electrically conductive tubesheet surrounding the tube, based upon the electrical resistance of the tube and tubesheet. A constant current source is applied to the interior of the electrically conducting tube by probes and a voltmeter is connected between other probes to measure the voltage at the point of current injection, which is inversely proportional to the amount of contact between the tube and tubesheet. Namely, the higher the voltage measured by the voltmeter, the less contact between the tube and tubesheet.

Method and apparatus for remote tube crevice detection by current and voltage probe resistance measurement

DOEpatents

Kikta, T.J.; Mitchell, R.D.

1992-11-24

A method and apparatus for determining the extent of contact between an electrically conducting tube and an electrically conductive tubesheet surrounding the tube, based upon the electrical resistance of the tube and tubesheet. A constant current source is applied to the interior of the electrically conducting tube by probes and a voltmeter is connected between other probes to measure the voltage at the point of current injection, which is inversely proportional to the amount of contact between the tube and tubesheet. Namely, the higher the voltage measured by the voltmeter, the less contact between the tube and tubesheet. 4 figs.

The design of superhydrophobic stainless steel surfaces by controlling nanostructures: A key parameter to reduce the implantation of pathogenic bacteria.

PubMed

Bruzaud, Jérôme; Tarrade, Jeanne; Celia, Elena; Darmanin, Thierry; Taffin de Givenchy, Elisabeth; Guittard, Frédéric; Herry, Jean-Marie; Guilbaud, Morgan; Bellon-Fontaine, Marie-Noëlle

2017-04-01

Reducing bacterial adhesion on substrates is fundamental for various industries. In this work, new superhydrophobic surfaces are created by electrodeposition of hydrophobic polymers (PEDOT-F 4 or PEDOT-H 8 ) on stainless steel with controlled topographical features, especially at a nano-scale. Results show that anti-bioadhesive and anti-biofilm properties require the control of the surface topographical features, and should be associated with a low adhesion of water onto the surface (Cassie-Baxter state) with limited crevice features at the scale of bacterial cells (nano-scale structures). Copyright © 2016. Published by Elsevier B.V.

ECLSS Sustaining Metal Materials Compatibility Final Report, Electrochemical and Crevice Corrosion Test Results

NASA Technical Reports Server (NTRS)

Lee, R. E.

2015-01-01

Electrochemical test results are presented for six noble metals evaluated in two acidic test solutions which are representative of waste liquids processed in the Environmental Control and Life Support System (ECLSS) aboard the International Space Station (ISS). The two test solutions consisted of fresh waste liquid which had been modified with a proposed or alternate pretreatment formulation and its associated brine concentrate. The six test metals included three titanium grades, (Commercially Pure, 6Al-4V alloy and 6Al-4V Low Interstitial alloy), two nickel-chromium alloys (Inconel® 625 and Hastelloy® C276), and one high tier stainless steel (Cronidur® 30).

Life expectancy of modular Ti6Al4V hip implants: influence of stress and environment.

PubMed

Chandra, A; Ryu, J J; Karra, P; Shrotriya, P; Tvergaard, V; Gaisser, M; Weik, T

2011-11-01

Stress dependent electrochemical dissolution is identified as one of the key mechanisms governing surface degradation in fretting and crevice corrosion of biomedical implants. The present study focuses on delineating the roles of mechanical stress and chemical conditions on the life expectancy of modular hip implants. First, material removal on a stressed surface of Ti6Al4V subjected to single asperity contact is investigated experimentally to identify the influence of contact load, in-plane stress and chemical environment on mean wear rates. A range of known stress levels are applied to the specimen while its surface is mechanically stimulated in different non-reactive to oxidizing aqueous environments. Evolution of surface degradation is monitored, and its mechanism is elucidated. This phase allows estimation of Preston Constant which is later used in the analysis. Second phase of the work is semi-analytical and computational, where, based on the estimated Preston constant and other material and process parameters, the scratch propensity (consisting of magnitude of scratch depth and their frequency per unit area) due to micro-motion in modular hip implants is estimated. The third phase views these scratches as initial notches and utilizes a mixed-mode fatigue crack propagation model to estimate the critical crack length for onset of instability. The number of loading cycles needed to reach this critical crack length is then labeled as the expected life of the implant under given mechanical and chemical conditions. Implications of different material and process conditions to life expectancy of orthopedic implants are discussed. It is observed that transverse micro-motion, compared to longitudinal micro-motion, plays a far more critical role in determining the implant life. Patient body weight, as well as proximity of the joint fluid to its iso-electric point play key roles in determining wear rates and associated life expectancies of modular hip implants. Sustained aeration of joint fluid, as well as proper tolerancing of mating surfaces, along with a proper choice of material microstructure may be utilized to extend implant life. Copyright © 2011 Elsevier Ltd. All rights reserved.

Performance and efficiency evaluation and heat release study of a direct-injection stratified-charge rotary engine

NASA Technical Reports Server (NTRS)

Nguyen, H. L.; Addy, H. E.; Bond, T. H.; Lee, C. M.; Chun, K. S.

1987-01-01

A computer simulation which models engine performance of the Direct Injection Stratified Charge (DISC) rotary engines was used to study the effect of variations in engine design and operating parameters on engine performance and efficiency of an Outboard Marine Corporation (OMC) experimental rotary combustion engine. Engine pressure data were used in a heat release analysis to study the effects of heat transfer, leakage, and crevice flows. Predicted engine data were compared with experimental test data over a range of engine speeds and loads. An examination of methods to improve the performance of the rotary engine using advanced heat engine concepts such as faster combustion, reduced leakage, and turbocharging is also presented.

Cracks and crevices: globalization discourse and medical education.

PubMed

Hodges, Brian David; Maniate, Jerry M; Martimianakis, Maria Athina Tina; Alsuwaidan, Mohammad; Segouin, Christophe

2009-10-01

Globalization discourse, and its promises of a 'flat world', 'borderless economy' and 'mobility of ideas and people', has become very widespread in all fields. In medical education this discourse is underpinned by assumptions that medical competence has universal elements and that medical education can therefore develop 'global standards' for accreditation, curricula and examinations. Yet writers in the field other than medicine have raised a number of concerns about an overemphasis on the economic aspects of globalization. This article explores the notion that it is time to study and embrace differences and discontinuities in goals, practices and values that underpin medical competence in different countries and to critically examine the promises-realized or broken-of globalization discourse in medical education.

Recognition and inference of crevice processing on digitized paintings

NASA Astrophysics Data System (ADS)

Karuppiah, S. P.; Srivatsa, S. K.

2013-03-01

This paper is designed to detect and removal of cracks on digitized paintings. The cracks are detected by threshold. Afterwards, the thin dark brush strokes which have been misidentified as cracks are removed using Median radial basis function neural network on hue and saturation data, Semi-automatic procedure based on region growing. Finally, crack is filled using wiener filter. The paper is well designed in such a way that most of the cracks on digitized paintings have identified and removed. The paper % of betterment is 90%. This paper helps us to perform not only on digitized paintings but also the medical images and bmp images. This paper is implemented by Mat Lab.

Physiological and ecological consequences of sleeping-site selection by the Galapagos land iguana (Conolophus pallidus)

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

Christian, K.A.; Tracy, C.R.

1984-01-01

Field observations and biophysical models were combined to analyze sleeping-site selection by Galapagos land iguanas (Conolophus pallidus). Iguanas slept in different kinds of sleeping sites during different seasons. In the coolest season (garua), adult land iguanas were found in sleeping sites that were warmer than the coolest sites available. This may be because the garua season (cool, overcast, and foggy) is a time when environmental conditions mitigate against rapid warm-up in the mornings, so lizards may regulate nighttime body temperatures so that it is easier to warm up to preferred daytime body temperatures. In the warmest season, adult iguanas weremore » found in the coolest sleeping sites available. This observation is consistent with hypotheses of voluntary hypothermia, which can be advantageous in energy conservation and in avoiding detrimental effects associated with maintenance of constant body temperatures throughout the day and night. Juvenile iguanas were found sleeping in rock crevices regardless of the ambient thermal environments. Such sites are likely to be important as refugia for this life stage, which, unlike the adult stage, is vulnerable to predation. It was concluded that selection of sleeping sites is a process that may help in avoidance of predation, optimization of body temperature at the end of the sleeping period, and reduction of metabolic costs during sleeping. The importance of some of these factors may change with the thermal milieu (e.g., season).« less

Hypoxia tolerance in coral-reef triggerfishes (Balistidae)

NASA Astrophysics Data System (ADS)

Wong, Corrie C.; Drazen, Jeffrey C.; Callan, Chatham K.; Korsmeyer, Keith E.

2018-03-01

Despite high rates of photosynthetic oxygen production during the day, the warm waters of coral reefs are susceptible to hypoxia at night due to elevated respiration rates at higher temperatures that also reduce the solubility of oxygen. Hypoxia may be a challenge for coral-reef fish that hide in the reef to avoid predators at night. Triggerfishes (Balistidae) are found in a variety of reef habitats, but they also are known to find refuge in reef crevices and holes at night, which may expose them to hypoxic conditions. The critical oxygen tension ( P crit) was determined as the point below which oxygen uptake could not be maintained to support standard metabolic rate (SMR) for five species of triggerfish. The triggerfishes exhibited similar levels of hypoxia tolerance as other coral-reef and coastal marine fishes that encounter low oxygen levels in their environment. Two species, Rhinecanthus rectangulus and R. aculeatus, had the lowest P crit ( 3.0 kPa O2), comparable to the most hypoxia-tolerant obligate coral-dwelling gobies, while Odonus niger and Sufflamen bursa were moderately tolerant to hypoxia ( P crit 4.5 kPa), and Xanthichthys auromarginatus was intermediate ( P crit 3.7 kPa). These differences in P crit were not due to differences in oxygen demand, as all the species had a similar SMR once mass differences were taken into account. The results suggest that triggerfish species are adapted for different levels of hypoxia exposure during nocturnal sheltering within the reef.

Ten-Year Cross-Sectional Study of Mechanically Assisted Crevice Corrosion in 1352 Consecutive Patients With Metal-on-Polyethylene Total Hip Arthroplasty.

PubMed

Hussey, Daniel K; McGrory, Brian J

2017-08-01

Mechanically assisted crevice corrosion (MACC) in metal-on-polyethylene total hip arthroplasty (THA) is of concern, but its prevalence, etiology, and natural history are incompletely understood. From January 2003 to December 2012, 1352 consecutive THA surgeries using a titanium stem, cobalt-chromium alloy femoral head, and highly cross-linked polyethylene liner from a single manufacturer were performed. Patients were followed at 1-year and 5-year intervals for surveillance, but also seen earlier if they had symptoms. Any patient with osteolysis >1 cm (n = 3) or unexplained pain (n = 85) underwent examination, radiographs, complete blood count, erythrocyte sedimentation rate, and C-reactive protein, as well as tests for serum cobalt and chromium levels. Symptomatic MACC was present in 43 of 1352 patients (3.2%). Prevalence of MACC by year of implant ranged from 0% (0 of 61, 2003; 0 of 138, 2005) to 10.5% (17 of 162; 2009). The M/L Taper stem had a greater prevalence (4.9%) of MACC than all other Zimmer (Zimmer, Inc, Warsaw, IN) 12/14 trunnion stem types combined (1.2%; P < .001). Twenty-seven of 43 (62.8%) patients have undergone revision surgery, and 16 of 43 (37.2%) patients have opted for ongoing surveillance. Comparing symptomatic THA patients with and without MACC, no demographic, clinical, or radiographic differences were found. MACC was significantly more common in 0 length femoral heads (compared with both -3.5 mm and +3.5 mm heads). The prevalence of MACC in metal-on-polyethylene hips is higher in this cross-sectional study than previously reported. A significantly higher prevalence was found in patients with M/L Taper style stem and THA performed both in 2009 and also between 2009 and 2012 with this manufacturer. Copyright © 2017 Elsevier Inc. All rights reserved.

Outcompeted by an invader? Interference and exploitative competition between tropical house gecko (Hemidactylus mabouia) and Barbados leaf-toed gecko (Phyllodactylus pulcher) for diurnal refuges in anthropogenic coastal habitats.

PubMed

Williams, Robert; Pernetta, Angelo P; Horrocks, Julia A

2016-05-01

House geckos in the genus Hemidactylus are highly successful colonizers of regions beyond their native range, with colonization often resulting in displacement of native gecko species through competitive interactions for daytime refuge (crevices) and prey resources. We report on data collected from nighttime surveys undertaken in April-May 2014 on Barbados, West Indies, that focused on the distribution and abundance of the endemic Barbados leaf-toed gecko (Phyllodactylus pulcher) and the introduced tropical house gecko (Hemidactylus mabouia) along unlit coastal walls and among boulders in the grounds of a hotel resort. In contrast to patterns of displacement of native species by H. mabouia seen elsewhere, P. pulcher was more abundant than H. mabouia on coastal walls, whereas the latter was found in greater numbers using boulders at this site. Walls and boulders differed with regard to availability of diurnal refugia suitable for geckos, with the walls having high frequency of small crevices with openings <20 mm, and boulders offering very little cover other than the underside of the boulder itself. To investigate whether this niche separation was a result of differences in diurnal refuge use between the species, we conducted experimental trials in which geckos were allowed to select between refugia with different characteristics. Both species selected for narrower and warmer refugia, and refugia that had been previously occupied by the other species. These shared preferences for refugia type suggest that other factors underlie the niche separation observed in the field. In supporting high densities of P. pulcher, coastal walls could offer important secondary habitat by augmenting the natural cliff side habitat of this endemic gecko, a finding that could be exploited for the conservation of this candidate species for Critically Endangered classification. © 2016 International Society of Zoological Sciences, Institute of Zoology/Chinese Academy of Sciences and John Wiley & Sons Australia, Ltd.

On the relative importance of pool morphology and woody debris to distributions of shrimp in a Puerto Rican headwater stream

USGS Publications Warehouse

Pyron, M.; Covich, A.P.; Black, R.W.

1999-01-01

In this paper, we report the sizes and distributional orientation of woody debris in a headwater rainforest stream in the Luquillo Experimental Forest (LEF), Puerto Rico. We also provide results of a 4-month study of a wood addition experiment designed to increase cover for benthic macroinvertebrates (freshwater shrimp). We added branch-sized woody debris to 20 pools in three streams. We trapped four species of freshwater shrimp (two species of benthic detritivores and two predatory shrimp species) during each of the 4 months following wood additions. An analysis of pool morphology (maximum depth, surface area and volume) provided a useful predictor of shrimp abundances. In general, numbers of shrimps increased with sizes of stream pools. A repeated measures ANOVA demonstrated no effect of woody debris additions on total numbers of shrimp per pool area. Two detritivore species (Atya lanipes, a filter feeder and Xiphocaris elongata, a shredder) decreased in abundance with increased woody debris and there was no statistical relationship between woody debris additions and predators (Macrobrachium carcinus and M. crenulatum). Small woody debris additions may have altered flow velocities that were important to filter-feeding Atya at the microhabitat scale, although the overall velocities within pools were not altered by wood additions. Lower numbers of Atya and Xiphocaris in two of the three streams may result from the occurrence of two predaceous fishes (American eel and mountain mullet) and more predatory Macrobrachium in these streams. One likely interpretation of the results of this study is that the stream pools in these study reaches had sufficient habitat structure provided by numerous rock crevices (among large rocks and boulders) to provide refuge from predators. Addition of woody debris did not add significantly to the existing structure. These results may not apply to stream channels with sand and gravel substrata where crevices and undercut banks are lacking and where woody debris often plays a major role by providing structure and refuge.

A 2650-year-long record of environmental change from northern Yellowstone National Park based on a comparison of multiple proxy data

USGS Publications Warehouse

Whitlock, C.; Dean, W.; Rosenbaum, J.; Stevens, L.; Fritz, S.; Bracht, B.; Power, M.

2008-01-01

Geochemical, stable-isotope, pollen, charcoal, and diatom records were analyzed at high-resolution in cores obtained from Crevice Lake, a varved-sediment lake in northern Yellowstone National Park. The objective was to reconstruct the ecohydrologic, vegetation, and fire history of the watershed for the last 2650 years to better understand past climate variations at the forest-steppe transition. The data suggest a period of limited bottom-water anoxia, relatively wet winters, and cool springs and summers from 2650 to 2100 cal yr BP (700-150 BC). Dry warm conditions occurred between 2100 and 850-800 cal yr BP (150 BC and AD 1100-1150), when the lake was anoxic, winter precipitation was low, and summer stratification was protracted. The data are consistent with overall warmer/drier conditions during the Medieval Climate Anomaly, although they suggest a shift towards wetter winters within that period. The period from 850 to 800 cal yr BP (AD 1100-1150) to 250 cal yr BP (AD 1700) was characterized by greater water-column mixing and cooler spring/summer conditions than before. In addition, fire activity shifted towards infrequent large events and pollen production was low. From 250 to 150 cal yr BP (AD 1700-1800), winter precipitation was moderate compared to previous conditions, and the lake was again stratified, suggesting warm summers. Between 150 and 42 cal yr BP (AD 1800-1908), winter precipitation increased and spring and summer conditions became moderate. Metal pollution, probably from regional mining operations, is evident in the 1870s. Large fires occurred between ca. 1800-1880, but in general the forests were more closed than before. The Crevice Lake record suggests that the last 150 years of Yellowstone's environmental history were characterized by intermediate conditions when compared with the previous 2500 years. ?? 2007 Elsevier Ltd and INQUA.

Coastal cliffs, rock-slope failures and Late Quaternary transgressions of the Black Sea along southern Crimea

NASA Astrophysics Data System (ADS)

Pánek, Tomáš; Lenart, Jan; Hradecký, Jan; Hercman, Helena; Braucher, Règis; Šilhán, Karel; Škarpich, Václav

2018-02-01

Rock-slope failures represent a significant hazard along global coastlines, but their chronology remains poorly documented. Here, we focus on the geomorphology and chronology of giant rockslides affecting the Crimean Mountains along the Black Sea coast. Geomorphic evidence suggests that high (>100 m) limestone cliffs flanking the southern slopes of the Crimean Mountains are scarps of rockslides nested within larger deep-seated gravitational slope deformations (DSGSDs). Such pervasive slope failures originated due to lateral spreading of intensively faulted Late Jurassic carbonate blocks moving atop weak/plastic Late Triassic flysch and tuff layers. By introducing a dating strategy relying on the combination of the uranium-thorium dating (U-Th) of exposed calcareous speleothems covering the landslide scarps with the 36Cl exposure dating of rock walls, we are able to approximate the time interval between the origin of incipient crevices and the final collapse of limestone blocks that exposed the cliff faces. For the three representative large-scale rockslides between the towns of Foros and Yalta, the initiation of the DSGSDs as evidenced by the widening of crevices and the onset of speleothem accumulation was >300 ka BP, but the recent cliff morphology along the coast is the result of Late Pleistocene/Holocene failures spanning ∼20-0.5 ka BP. The exposures of rockslide scarps occurred mostly at ∼20-15, ∼8, ∼5-4 and ∼2-0.5 ka, which substantially coincide with the last major Black Sea transgressions and/or more humid Holocene intervals. Our study suggests that before ultimate fast and/or catastrophic slope failures, the relaxation of rock massifs correlative with karstification, cracks opening, and incipient sliding lasted on the order of 104-105 years. Rapid Late Glacial/Holocene transgressions of the Black Sea likely represented the last impulse for the collapse of limestone blocks and the origin of giant rockslides, simultaneously affecting the majority of the SW coast of the Crimean Peninsula.

Corrosion Damage and Wear Mechanisms in Long-Term Retrieved CoCr Femoral Components for Total Knee Arthroplasty.

PubMed

Arnholt, Christina M; MacDonald, Daniel W; Malkani, Arthur L; Klein, Gregg R; Rimnac, Clare M; Kurtz, Steven M; Kocagoz, Sevi B; Gilbert, Jeremy L

2016-12-01

Metal debris and ion release has raised concerns in joint arthroplasty. The purpose of this study was to characterize the sources of metallic ions and particulate debris released from long-term (in vivo >15 years) total knee arthroplasty femoral components. A total of 52 CoCr femoral condyles were identified as having been implanted for more than 15 years. The femoral components were examined for incidence of 5 types of damage (metal-on-metal wear due to historical polyethylene insert failure, mechanically assisted crevice corrosion at taper interfaces, cement interface corrosion, third-body abrasive wear, and inflammatory cell-induced corrosion [ICIC]). Third-body abrasive wear was evaluated using the Hood method for polyethylene components and a similar method quantifying surface damage of the femoral condyle was used. The total area damaged by ICIC was quantified using digital photogrammetry. Surface damage associated with corrosion and/or CoCr debris release was identified in 51 (98%) CoCr femoral components. Five types of damage were identified: 98% of femoral components exhibited third-body abrasive wear (mostly observed as scratching, n = 51/52), 29% of femoral components exhibited ICIC damage (n = 15/52), 41% exhibited cement interface damage (n = 11/27), 17% exhibited metal-on-metal wear after wear-through of the polyethylene insert (n = 9/52), and 50% of the modular femoral components exhibited mechanically assisted crevice corrosion taper damage (n = 2/4). The total ICIC-damaged area was an average of 0.11 ± 0.12 mm 2 (range: 0.01-0.46 mm 2 ). Although implant damage in total knee arthroplasty is typically reported with regard to the polyethylene insert, the results of this study demonstrate that abrasive and corrosive damage occurs on the CoCr femoral condyle in vivo. Copyright © 2016 Elsevier Inc. All rights reserved.

The seating mechanics of head-neck modular tapers in vitro: Load-displacement measurements, moisture, and rate effects.

PubMed

Ouellette, Eric S; Shenoy, Aarti A; Gilbert, Jeremy L

2018-04-01

The mechanically assisted crevice corrosion performance of head-neck modular tapers is a significant concern in orthopedic biomaterials. Fretting crevice corrosion processes in modular tapers are thought to be influenced by a wide array of factors including seating mechanics of the junction, hence there is a need for in vitro test methods that can assess their performance. This study presented a test method to directly measure the load-displacement seating mechanics of modular tapers and used this method to compare the seating mechanics for different tapers, moisture, seating loads and seating rates. Seating mechanics were explored whereby the instantaneous load-displacement behavior of the head seating onto the neck is captured and used to define the mechanics of seating. Two distinct taper design/material combinations were assembled wet or dry using axially applied loads (500, 1,000, 2,000, and 4,000 N) at two loading rates of 100 and 10 4  N/s (n = 5 for each condition) using a servohydraulic test frame. The results showed that pull-off strength scaled with seating load and ranged between 43% and 68% of seating load depending on sample and wetness. Tapers seated wet had higher pull-off strengths (2,200 ± 300 N) than those seated dry (1,800 ± 200 N, p < 0.05). Seating mechanics (load-displacement plots) varied due to sample type and due to wetness with differences in seating energy, seating stiffness, and seating displacement. These results show the detailed mechanics of seating during assembly and provide significant insight into the complex interplay of factors associated with even "ideal" seating (axial, quasistatic) loading. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1164-1172, 2018. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Ground Penetrating Radar, a Method for Exploration and Monitoring of Coal Fires in China

NASA Astrophysics Data System (ADS)

Gundelach, Volker

2010-05-01

Due to the climate change it is a global task to fight against gas emission of coal fires. In China exists many burning coal seams which should be extinguished. A Chinese-German initiative tries to find new technologies and solutions to control these fires. Most of the fires are close to the surface in arid areas. In that case GPR is a possible geophysical method to get detailed information about the structure of the soil. Mining activities and the burning coal are leaving voids which collapse or still exist as dangerous areas. With GPR it is possible to detect voids and clefts. Crevices are potential paths for oxygen transport from the surface to the fire. The knowledge of these structures would help to extinguish the fire. The heat of the burning coal changes the permittivity and the conductivity of the rock. This affects the radar signal and makes it possible to separate burning zones from intact zones. Monitoring of the burning zones helps to find optimal solutions for fire extinguishing strategies. Several field campaigns were made in China. One campaign was in the province Xinjiang with a 50 MHz system from Mala on a steep dipping coal seam. Other campaigns were in the Inner Mongolia with 40 MHz to 200 MHz antennae from GSSI on shallow dipping coal seams. The experiences from these measurements will be shown. The surveys were collected in rough terrain. The data from the unshielded antennae contained a lot of effects coming through the air. The limits of detecting crevices with GPR will be demonstrated. Some parts of the measurements over burning coal were influenced by strong anomalies of the magnetization. Modeling of the radar signal helps at the interpretation. Parts of the interpretation from the surveys can be validated by the outcrop of the investigated structures. A spatial visualization of the results is the basis for discussions.

R102Q mutation shifts the salt-bridge network and reduces the structural flexibility of human neuronal calcium sensor-1 protein.

PubMed

Zhu, Yuzhen; Wu, Ying; Luo, Yin; Zou, Yu; Ma, Buyong; Zhang, Qingwen

2014-11-20

Neuronal calcium sensor-1 (NCS-1) protein has a variety of different neuronal functions and interacts with multiple binding partners mostly through a large solvent-exposed hydrophobic crevice (HC). A single R102Q mutation in human NCS-1 protein was demonstrated to be associated with autism disease. Solution NMR study reported that this R102Q mutant had long-range chemical shift effects on the HC and the C-terminal tail (L3). To understand the influence of the R102Q mutation on the HC and L3 of NCS-1, we have investigated the conformational dynamics and the structural flexibility of wild type (WT) NCS-1 and its R102Q mutant by conducting extensive all-atom molecular dynamics (MD) simulations. On the basis of six independent 450 ns MD simulations, we have found that the R102Q mutation in NCS-1 protein (1) dramatically reduces the flexibility of loops L2 and L3, (2) facilitates L3 in a more extended state to occupy the hydrophobic crevice to a larger extent, (3) significantly affects the intersegment salt bridges, and (4) changes the subspace of the free energy landscape of NCS-1 protein. Analysis of the salt bridge network in both WT and the R102Q variant demonstrates that the R102Q-mutation-induced salt bridge alternations play a critical role on the reduced flexibility of L2 and L3. These results reveal the important role of salt bridges on the structural properties of NCS-1 protein and that R102Q mutation disables the dynamic relocation of C-terminus, which may block the binding of NCS-1 protein to its receptors. This study may provide structural insights into the autistic spectrum disorder associated with R102Q mutation.

Squamation and ecology of thelodonts.

PubMed

Ferrón, Humberto G; Botella, Héctor

2017-01-01

Thelodonts are an enigmatic group of Paleozoic jawless vertebrates that have been well studied from taxonomical, biostratigraphic and paleogeographic points of view, although our knowledge of their ecology and mode of life is still scant. Their bodies were covered by micrometric scales whose morphology, histology and the developmental process are extremely similar to those of extant sharks. Based on these similarities and on the well-recognized relationship between squamation and ecology in sharks, here we explore the ecological diversity and lifestyles of thelodonts. For this we use classic morphometrics and discriminant analysis to characterize the squamation patterns of a significant number of extant shark species whose ecology is well known. Multivariate analyses have defined a characteristic squamation pattern for each ecological group, thus establishing a comparative framework for inferring lifestyles in thelodonts. We then use this information to study the squamation of the currently described 147 species of thelodonts, known from both articulated and disarticulated remains. Discriminant analysis has allowed recognizing squamation patterns comparable to those of sharks and links them to specific ecological groups. Our results suggest a remarkable ecological diversity in thelodonts. A large number of them were probably demersal species inhabiting hard substrates, within caves and crevices in rocky environments or reefs, taking advantage of the flexibility provided by their micromeric squamations. Contrary to classical interpretations, only few thelodonts were placed among demersal species inhabiting sandy and muddy substrates. Schooling species with defensive scales against ectoparasites could be also abundant suggesting that social interactions and pressure of ectoparasites were present in vertebrates as early the Silurian. The presence of species showing scales suggestive of low to moderate speed and a lifestyle presumably associated with open water environments indicates adaptation of thelodonts to deep water habitats. Scale morphology suggests that some other thelodonts were strong-swimming pelagic species, most of them radiating during the Early Devonian in association with the Nekton Revolution.

Squamation and ecology of thelodonts

PubMed Central

Botella, Héctor

2017-01-01

Thelodonts are an enigmatic group of Paleozoic jawless vertebrates that have been well studied from taxonomical, biostratigraphic and paleogeographic points of view, although our knowledge of their ecology and mode of life is still scant. Their bodies were covered by micrometric scales whose morphology, histology and the developmental process are extremely similar to those of extant sharks. Based on these similarities and on the well-recognized relationship between squamation and ecology in sharks, here we explore the ecological diversity and lifestyles of thelodonts. For this we use classic morphometrics and discriminant analysis to characterize the squamation patterns of a significant number of extant shark species whose ecology is well known. Multivariate analyses have defined a characteristic squamation pattern for each ecological group, thus establishing a comparative framework for inferring lifestyles in thelodonts. We then use this information to study the squamation of the currently described 147 species of thelodonts, known from both articulated and disarticulated remains. Discriminant analysis has allowed recognizing squamation patterns comparable to those of sharks and links them to specific ecological groups. Our results suggest a remarkable ecological diversity in thelodonts. A large number of them were probably demersal species inhabiting hard substrates, within caves and crevices in rocky environments or reefs, taking advantage of the flexibility provided by their micromeric squamations. Contrary to classical interpretations, only few thelodonts were placed among demersal species inhabiting sandy and muddy substrates. Schooling species with defensive scales against ectoparasites could be also abundant suggesting that social interactions and pressure of ectoparasites were present in vertebrates as early the Silurian. The presence of species showing scales suggestive of low to moderate speed and a lifestyle presumably associated with open water environments indicates adaptation of thelodonts to deep water habitats. Scale morphology suggests that some other thelodonts were strong-swimming pelagic species, most of them radiating during the Early Devonian in association with the Nekton Revolution. PMID:28241029

Ubiquinol-binding site in the alternative oxidase: mutagenesis reveals features important for substrate binding and inhibition.

PubMed

Albury, Mary S; Elliott, Catherine; Moore, Anthony L

2010-12-01

The alternative oxidase (AOX) is a non-protonmotive ubiquinol oxidase that is found in all plants, some fungi, green algae, bacteria and pathogenic protozoa. The lack of AOX in the mammalian host renders this protein an important potential therapeutic target in the treatment of pathogenic protozoan infections. Bioinformatic searches revealed that, within a putative ubiquinol-binding crevice in AOX, Gln242, Asn247, Tyr253, Ser256, His261 and Arg262 were highly conserved. To confirm that these amino-acid residues are important for ubiquinol-binding and hence activity substitution mutations were generated and characterised. Assessment of AOX activity in isolated Schizosaccharomyces pombe mitochondria revealed that mutation of either Gln242, Ser256, His261 and Arg262 resulted in >90% inhibition of antimycin A-insensitive respiration suggesting that hydroxyl, guanidino, imidazole groups, polar and charged residues in addition to the size of the amino-acid chain are important for ubiquinone-binding. Substitution of Asn247 with glutamine or Tyr253 with phenylalanine had little effect upon the respiratory rate indicating that these residues are not critical for AOX activity. However replacement of Tyr253 by alanine resulted in a 72% loss of activity suggesting that the benzoquinone group and not hydroxyl group is important for quinol binding. These results provide important new insights into the ubiquinol-binding site of the alternative oxidase, the identity of which maybe important for future rational drug design. Copyright © 2010 Elsevier B.V. All rights reserved.

Emotional environments retune the valence of appetitive versus fearful functions in nucleus accumbens

PubMed Central

Reynolds, Sheila M; Berridge, Kent C

2009-01-01

The nucleus accumbens mediates both appetitive motivation for rewards and fearful motivation toward threats, which are generated in part by glutamate-related circuits organized in a keyboard fashion. At rostral sites of the medial shell, localized glutamate disruptions typically generate intense appetitive behaviors in rats, but the disruption incrementally generates fearful behaviors as microinjection sites move more caudally. We found that exposure to stressful environments caused caudal fear-generating zones to expand rostrally, filling ~90% of the shell. Conversely, a preferred home environment caused fear-generating zones to shrink and appetitive-generating zones to expand caudally, filling ~90% of the shell. Thus, the emotional environments retuned the generation of motivation in corticolimbic circuits. PMID:18344996

PFC Decontamination of a Metal Surface and the Recycling of a Spent PFC Solution

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

Jung, C.H.; Won, H.J.; Oh, W.Z.

2006-07-01

PFC (per-fluorocarbon) ultrasonic decontamination behavior of loosely contaminated metal specimens such as a plate, pipe, welding and a crevice specimen in a mixed solution of PFC and an anionic surfactant was investigated. Perfluoroheptane (C{sub 7}F{sub 16}) was used as a PFC ultrasonic media. The contaminants were completely removed for almost all of the tested specimens except for the longest pipe length specimen. For the 6-cm long specimen, 98.5 % of the contaminants were removed. For the recycling of the PFC solution, a distillation test for the spent PFC solution was also performed. The results show that 97.5 % of themore » PFC was recycled without a loss of the decontamination efficiency. (authors)« less

Dynamics and distribution of black abalone populations at San Nicolas Island

USGS Publications Warehouse

VanBlaricom, Glenn R.; Hochberg, F.G.

1993-01-01

Dense populations of black abalones (Haliotis cracherodii Leach) were monitored in permanent intertidal plots at nine sites on San Nicolas Island from 1981 through 1990. Densities were essentially constant at all four sites along the north shore of the island throughout the study period. Densities at five sites along the south shore were more variable, possibly reflecting asynchronous variation in recruitment, mortality resulting from wave disturbance, and removal by people. Temporal variation of abalone densities apparently was not influenced by sea otters or abalone withering syndrome during this study. Abalones were strongly aggregated in space. Highest densities occurred in areas of irregular substrata, apparently as a result of preference for crevices and vertical faces. The locations of dense patches were persistent in time.

Passive Films, Surface Structure and Stress Corrosion and Crevice Corrosion Susceptibility. Part I. A Qualitative Ellipsometric-Electrochemical Approach for the Study of Film Growth under Organic Coatings. Part II. Hydrogen Interactions with Stressed Titanium-Palladium Alloys and Stressed Vanadium Explored with Field Ion Microscopy.

DTIC Science & Technology

1980-08-01

vs. time for Fe with collodion in 0.05 N NaCl. 8. A, 6 p, pH and 0Fe vs. time for Fe with collodion and CrO 4 " 2 islands in 0.05 N NaCl. REFERENCES...hydrogen embrittlement with the field ion microscope, and to compare the results with those previously obtained with pure titanium [ 4 ]. 2.2. Specimen...percent pure, and was used in the previous field ion microscopy study of titanium [ 4 ], where it was found that strain annealing titanium wire markedly

Generation of development environments for the Arden Syntax.

PubMed Central

Bång, M.; Eriksson, H.

1997-01-01

Providing appropriate development environments for specialized languages requires a significant development and maintenance effort. Specialized environments are therefore expensive when compared to their general-language counterparts. The Arden Syntax for Medical Logic Modules (MLM) is a standardized language for representing medical knowledge. We have used PROTEGE-II, a knowledge-engineering environment, to generate a number of experimental development environments for the Arden Syntax. MEDAILLE is the resulting MLM editor, which provides a user-friendly environment that allows users to create and modify MLM definitions. Although MEDAILLE is a generated editor, it has similar functionality, while reducing the programming effort, as compared to other MLM editors developed using traditional programming techniques. We discuss how developers can use PROTEGE-II to generate development environments for other standardized languages and for general programming languages. PMID:9357639

Mobile e-Learning for Next Generation Communication Environment

ERIC Educational Resources Information Center

Wu, Tin-Yu; Chao, Han-Chieh

2008-01-01

This article develops an environment for mobile e-learning that includes an interactive course, virtual online labs, an interactive online test, and lab-exercise training platform on the fourth generation mobile communication system. The Next Generation Learning Environment (NeGL) promotes the term "knowledge economy." Inter-networking…

Generating realistic environments for cyber operations development, testing, and training

NASA Astrophysics Data System (ADS)

Berk, Vincent H.; Gregorio-de Souza, Ian; Murphy, John P.

2012-06-01

Training eective cyber operatives requires realistic network environments that incorporate the structural and social complexities representative of the real world. Network trac generators facilitate repeatable experiments for the development, training and testing of cyber operations. However, current network trac generators, ranging from simple load testers to complex frameworks, fail to capture the realism inherent in actual environments. In order to improve the realism of network trac generated by these systems, it is necessary to quantitatively measure the level of realism in generated trac with respect to the environment being mimicked. We categorize realism measures into statistical, content, and behavioral measurements, and propose various metrics that can be applied at each level to indicate how eectively the generated trac mimics the real world.

GRIFFIN: A versatile methodology for optimization of protein-lipid interfaces for membrane protein simulations

PubMed Central

Staritzbichler, René; Anselmi, Claudio; Forrest, Lucy R.; Faraldo-Gómez, José D.

2014-01-01

As new atomic structures of membrane proteins are resolved, they reveal increasingly complex transmembrane topologies, and highly irregular surfaces with crevices and pores. In many cases, specific interactions formed with the lipid membrane are functionally crucial, as is the overall lipid composition. Compounded with increasing protein size, these characteristics pose a challenge for the construction of simulation models of membrane proteins in lipid environments; clearly, that these models are sufficiently realistic bears upon the reliability of simulation-based studies of these systems. Here, we introduce GRIFFIN, which uses a versatile framework to automate and improve a widely-used membrane-embedding protocol. Initially, GRIFFIN carves out lipid and water molecules from a volume equivalent to that of the protein, so as to conserve the system density. In the subsequent optimization phase GRIFFIN adds an implicit grid-based protein force-field to a molecular dynamics simulation of the pre-carved membrane. In this force-field, atoms inside the implicit protein volume experience an outward force that will expel them from that volume, whereas those outside are subject to electrostatic and van-der-Waals interactions with the implicit protein. At each step of the simulation, these forces are updated by GRIFFIN and combined with the intermolecular forces of the explicit lipid-water system. This procedure enables the construction of realistic and reproducible starting configurations of the protein-membrane interface within a reasonable timeframe and with minimal intervention. GRIFFIN is a standalone tool designed to work alongside any existing molecular dynamics package, such as NAMD or GROMACS. PMID:24707227

Microbial diversity and interactions in subgingival biofilm communities.

PubMed

Diaz, Patricia I

2012-01-01

The human subgingival environment is a complex environmental niche where microorganisms from the three domains of life meet to form diverse biofilm communities that exist in close proximity to the host. Bacteria constitute the most abundant, diverse and ultimately well-studied component of these communities with about 500 bacterial taxa reported to occur in this niche. Cultivation and molecular approaches are revealing the breadth and depth of subgingival biofilm diversity as part of an effort to understand the subgingival microbiome, the collection of microorganisms that inhabit the gingival crevices. Although these investigations are constructing a pretty detailed taxonomical census of subgingival microbial communities, including inter-subject and temporal variability in community structure, as well as differences according to periodontal health status, we are still at the front steps in terms of understanding community function. Clinical studies that evaluate community structure need to be coupled with biologically relevant models that allow evaluation of the ecological determinants of subgingival biofilm maturation. Functional characteristics of subgingival biofilm communities that still need to be clarified include main metabolic processes that support microbial communities, identification of keystone species, microbial interactions and signaling events that lead to community maturation and the relationship of different communities with the host. This manuscript presents a summary of our current understanding of subgingival microbial diversity and an overview of experimental models used to dissect the functional characteristics of subgingival communities. Future coupling of 'omics'-based approaches with such models will facilitate a better understanding of subgingival ecology opening opportunities for community manipulation. Copyright © 2012 S. Karger AG, Basel.

Morphology, sociality, and ecology: can morphology predict pairing behavior in coral reef fishes?

NASA Astrophysics Data System (ADS)

Brandl, S. J.; Bellwood, D. R.

2013-09-01

Morphology can contain valuable information about the ecological performance of reef fishes, but it has rarely been used in combination with social traits. Social behavior is known to influence the ecological role of fishes; however, the ecological basis for pairing in reef fishes is not well understood. Field observations of 2,753 individuals, in 47 species in six families of biting reef fishes (Acanthuridae, Chaetodontidae, Kyphosidae, Labridae, Pomacanthidae, Siganidae), were used in combination with six morphological measurements, to examine the morphology of fishes in different social systems. A principal components analysis of morphological traits segregated species with high proportions of pairing individuals from non-pairing species along principal component 1, explaining 40.8 % of the variation. Pairing species were characterized by large eyes, concave foreheads, pointed snouts, deep bodies, and small maximum sizes. There was a significant positive relationship between these morphological traits (i.e., scores on PC1) and the prevalence of pairing within the Chaetodontidae ( r 2 = 0.59; P = 0.026), Siganidae ( r 2 = 0.72; P = 0.004), and Acanthuridae ( r 2 = 0.82; P < 0.001). This was consistent when traits were corrected for phylogenetic effects. No pattern was evident in the scarine Labridae ( r 2 = 0.15; P = 0.17). The morphological characteristics found among pairing species suggest that pairing species share common ecological traits, including foraging for small prey items in micro-topographically complex environments such as reef crevices. These ecological traits may have played a role in the evolution of pairing behavior and subsequently led to the development of reproductive patterns based on monogamy.

Relative Panoramic Camera Position Estimation for Image-Based Virtual Reality Networks in Indoor Environments

NASA Astrophysics Data System (ADS)

Nakagawa, M.; Akano, K.; Kobayashi, T.; Sekiguchi, Y.

2017-09-01

Image-based virtual reality (VR) is a virtual space generated with panoramic images projected onto a primitive model. In imagebased VR, realistic VR scenes can be generated with lower rendering cost, and network data can be described as relationships among VR scenes. The camera network data are generated manually or by an automated procedure using camera position and rotation data. When panoramic images are acquired in indoor environments, network data should be generated without Global Navigation Satellite Systems (GNSS) positioning data. Thus, we focused on image-based VR generation using a panoramic camera in indoor environments. We propose a methodology to automate network data generation using panoramic images for an image-based VR space. We verified and evaluated our methodology through five experiments in indoor environments, including a corridor, elevator hall, room, and stairs. We confirmed that our methodology can automatically reconstruct network data using panoramic images for image-based VR in indoor environments without GNSS position data.

Effect of thermal-convection-induced defects on the performance of perovskite solar cells

NASA Astrophysics Data System (ADS)

Ye, Fei; Xie, Fengxian; Yin, Maoshu; He, Jinjin; Wang, Yanbo; Tang, Wentao; Chen, Han; Yang, Xudong; Han, Liyuan

2017-07-01

Thermal-convection-induced defects can cause huge loss in the power conversion efficiency of solution-processed perovskite solar cells. We investigated two types of convection in perovskite solution during the formation of perovskite films. By balancing the convection via special configurations of surface tension and boiling point in mixed γ-butyrolactone (GBL) and dimethylsulfoxide (DMSO), we removed microscopic defects such as rings, bumps, and crevices. The deposited perovskite films were smooth and dense, which enabled a high power conversion efficiency of 17.7% in a 1 cm2 cell area. We believe that the present strategy for controlling the convection can be helpful in improving the perovskite film quality for solvent-rich scalable solution processes of solar cells such as doctor blading, soft-cover deposition, printing, and slot-die coating.

Anarbylus switaki Murphy: an addition to the herpetofauna of the United States with comments on relationships with Coleonyx

USGS Publications Warehouse

Fritts, T.H.; Snell, H.L.; Martin, R.L.

1982-01-01

Anarbys switaki, a species previously known only from Baja California Sur, Mexico, occurs in eastern San Diego and southwestern Imperial Counties in California. In California, specimens tend to have continuous transverse bars on the body, are lighter in color, and more slender in body form than in southern Baja California. California populations appear to be confined to extremely rocky habitats in desert foothill situations between 200 and 600 m. The species appears to be secretive, and occurs in low densities within rock crevices and subterranean cavities. The morphological gap between Anarbylus and Coleonyx species may not warrant generic recognition. Anarbylus is part of a diverse lizard fauna in southern California and occurs in sympatry with 15 lizard species in a small area of southern California.

Comparative study on corrosion behaviour of Nitinol and stainless steel orthodontic wires in simulated saliva solution in presence of fluoride ions.

PubMed

Mirjalili, M; Momeni, M; Ebrahimi, N; Moayed, M H

2013-05-01

Localized corrosion and effects of pre-passivation treatment of Nitinol and SS304 orthodontic wires in simulated saliva solution in the presence and absence of fluoride ions were investigated by means of potentiodynamic and potentiostatic polarisations. Results revealed that Nitinol does not show pitting corrosion in saliva solution however, SS304 shows pitting corrosion. Meanwhile fluoride ion has deteriorative effect on pitting corrosion of Nitinol, while its effect on SS304 was marginally constructive. Additionally, the presence of artificial crevice has no effect on corrosion behaviour in the presence of fluoride. Pre-passivation treatment has positive influence on pitting corrosion of both alloys in the presence of F(-) ions. Copyright © 2012 Elsevier B.V. All rights reserved.

A contemporary perspective on techniques for the clinical assessment of alveolar bone

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

Hausmann, E.

1990-03-01

Radiographic techniques, traditional ones as well as newer ones under development, for clinically assessing alveolar bone are critically assessed. Traditional intraoral radiography is reexamined, in particular with regard to the accuracy with which the alveolar crest is seen. Evidence is presented for a more accurate representation of the alveolar crest on bitewings rather than periapical films. Application in periodontics of newer radiographic techniques, subtraction radiography, and single and dual photon aborptiometry presently under clinical development are discussed in regard to their potential and limitations. Similarly, radiopharmaceuticals to evaluate the metabolic status of alveolar bone are discussed as well as themore » potential for using analyses of gingival crevice fluid as a window for assessment of alveolar crest metabolism. 46 references.« less

Topography-specific isotropic tunneling in nanoparticle monolayer with sub-nm scale crevices.

PubMed

Wang, Guisheng; Jiao, Weihong; Yi, Lizhi; Zhang, Yuejiao; Wu, Ke; Zhang, Chao; Lv, Xianglong; Qian, Lihua; Li, Jianfeng; Yuan, Songliu; Chen, Liang

2016-10-07

Material used in flexible devices may experience anisotropic strain with identical magnitude, outputting coherent signals that tend to have a serious impact on device reliability. In this work, the surface topography of the nanoparticles (NPs) is proposed to be a parameter to control the performance of strain gauge based on tunneling behavior. In contrast to anisotropic tunneling in a monolayer of spherical NPs, electron tunneling in a monolayer of urchin-like NPs actually exhibits a nearly isotropic response to strain with different loading orientations. Isotropic tunneling of the urchin-like NPs is caused by the interlocked pikes of these urchin-like NPs in a random manner during external mechanical stimulus. Topography-dependent isotropic tunneling in two dimensions reported here opens a new opportunity to create highly reliable electronics with superior performance.

Novel high explosive compositions

DOEpatents

Perry, D.D.; Fein, M.M.; Schoenfelder, C.W.

1968-04-16

This is a technique of preparing explosive compositions by the in-situ reaction of polynitroaliphatic compounds with one or more carboranes or carborane derivatives. One or more polynitroaliphatic reactants are combined with one or more carborane reactants in a suitable container and mixed to a homogeneous reaction mixture using a stream of inert gas or conventional mixing means. Ordinarily the container is a fissure, crack, or crevice in which the explosive is to be implanted. The ratio of reactants will determine not only the stoichiometry of the system, but will effect the quality and quantity of combustion products, the explosive force obtained as well as the impact sensitivity. The test values can shift with even relatively slight changes or modifications in the reaction conditions. Eighteen illustrative examples accompany the disclosure. (46 claims)

Cellulose as an Architectural Element in Spatially Structured Escherichia coli Biofilms

PubMed Central

Serra, Diego O.; Richter, Anja M.

2013-01-01

Morphological form in multicellular aggregates emerges from the interplay of genetic constitution and environmental signals. Bacterial macrocolony biofilms, which form intricate three-dimensional structures, such as large and often radially oriented ridges, concentric rings, and elaborate wrinkles, provide a unique opportunity to understand this interplay of “nature and nurture” in morphogenesis at the molecular level. Macrocolony morphology depends on self-produced extracellular matrix components. In Escherichia coli, these are stationary phase-induced amyloid curli fibers and cellulose. While the widely used “domesticated” E. coli K-12 laboratory strains are unable to generate cellulose, we could restore cellulose production and macrocolony morphology of E. coli K-12 strain W3110 by “repairing” a single chromosomal SNP in the bcs operon. Using scanning electron and fluorescence microscopy, cellulose filaments, sheets and nanocomposites with curli fibers were localized in situ at cellular resolution within the physiologically two-layered macrocolony biofilms of this “de-domesticated” strain. As an architectural element, cellulose confers cohesion and elasticity, i.e., tissue-like properties that—together with the cell-encasing curli fiber network and geometrical constraints in a growing colony—explain the formation of long and high ridges and elaborate wrinkles of wild-type macrocolonies. In contrast, a biofilm matrix consisting of the curli fiber network only is brittle and breaks into a pattern of concentric dome-shaped rings separated by deep crevices. These studies now set the stage for clarifying how regulatory networks and in particular c-di-GMP signaling operate in the three-dimensional space of highly structured and “tissue-like” bacterial biofilms. PMID:24097954

Relationship between enhanced dewaterability and structural properties of hydrothermal sludge after hydrothermal treatment of excess sludge.

PubMed

Wang, Liping; Li, Aimin; Chang, Yuzhi

2017-04-01

Hydrothermal treatment is an effective method to enhance the deep dewaterability of excess sludge with low energy consumption. In this study, an insight into the relationship between enhanced dewaterability and structural properties of the produced hydrothermal sludge was presented, aiming at better understanding the effect of hydrothermal process on excess sludge dewatering performance. The results indicated that hydrothermal effect induced the transformation of surface water to interstitial and free water by lowering the binding strength between adjacent water and solid particles and that free water became the main form for moisture existence in hydrothermal sludge as temperature was higher than 180 °C. Increase in temperature of hydrothermal treatment generated a significant size reduction of sludge flocs but treated sludge with a higher rigidity, which not only strengthened the network of hydrothermal sludge but also destroyed the binding of EPS with water. Hydrothermal process caused crevice and pore structures of excess sludge to disappear gradually, which was a main driving force of water removal as temperature was below 150 °C. With the temperature of hydrothermal treatment exceeding 180 °C, the morphology of hydrothermal sludge became rough which linked closely to the solid precipitation of condensation polymerization, and further became smooth at higher temperature (210 °C) due to the coal-like structures with higher aromaticities, indicating that hydrothermal reaction pathways began to play a main role in enhanced dewaterability. Hydrothermal treatment led to more alkyl and aromatic carbon, but lower O-alkyl, carboxyl and carbonyl carbon. Copyright © 2017 Elsevier Ltd. All rights reserved.

Cellulose as an architectural element in spatially structured Escherichia coli biofilms.

PubMed

Serra, Diego O; Richter, Anja M; Hengge, Regine

2013-12-01

Morphological form in multicellular aggregates emerges from the interplay of genetic constitution and environmental signals. Bacterial macrocolony biofilms, which form intricate three-dimensional structures, such as large and often radially oriented ridges, concentric rings, and elaborate wrinkles, provide a unique opportunity to understand this interplay of "nature and nurture" in morphogenesis at the molecular level. Macrocolony morphology depends on self-produced extracellular matrix components. In Escherichia coli, these are stationary phase-induced amyloid curli fibers and cellulose. While the widely used "domesticated" E. coli K-12 laboratory strains are unable to generate cellulose, we could restore cellulose production and macrocolony morphology of E. coli K-12 strain W3110 by "repairing" a single chromosomal SNP in the bcs operon. Using scanning electron and fluorescence microscopy, cellulose filaments, sheets and nanocomposites with curli fibers were localized in situ at cellular resolution within the physiologically two-layered macrocolony biofilms of this "de-domesticated" strain. As an architectural element, cellulose confers cohesion and elasticity, i.e., tissue-like properties that-together with the cell-encasing curli fiber network and geometrical constraints in a growing colony-explain the formation of long and high ridges and elaborate wrinkles of wild-type macrocolonies. In contrast, a biofilm matrix consisting of the curli fiber network only is brittle and breaks into a pattern of concentric dome-shaped rings separated by deep crevices. These studies now set the stage for clarifying how regulatory networks and in particular c-di-GMP signaling operate in the three-dimensional space of highly structured and "tissue-like" bacterial biofilms.

Shock Experiments on Basalt - Ferric Sulfate Mixes at 21 GPa & 49 GPa and their Relevance to Martian Meteorite Impact Glasses

NASA Technical Reports Server (NTRS)

Rao, M. N.; Ross, D. K.; See, T. H.; Nyquist, L. E.; Sutton, S.; Asimow, P.

2013-01-01

Large abundance of Martian atmospheric gases and neutron-induced isotopic excesses as well as Rb-Sr isotopic variations determined in some impact glasses in basaltic shergottites (e.g., Shergotty #DBS, Zagami #H1 and EET79001 #27, #8 and #104) provide definitive evidence for the occurrence of a Martian regolith component in their constituent mineral assemblages. Some of these glass-es, known as gas-rich impact-melts (GRIM), contain numerous micron-sized iron sulfide blebs along with minor amounts of iron sulfate particulates. As these GRIM glasses contain a Martian regolith component and as iron sulfates (but not sulfides) are found to occur abundantly on the Mars surface, we suggested that the sulfide blebs in GRIMs were likely generated by shock-reduction of the parental iron sulfate bearing regolith material that had been incorporated into the cavities/crevices of basaltic host rock prior to the impact event on Mars. To test whether the sulfates could be reduced to sulfides by impact shock, we carried out laboratory shock experiments on a basalt plus ferric sulfate mixture at 49 GPa at the Caltech Shock Wave Laboratory and at 21 GPa at Johnson Space Center (JSC) Experimental Impact Laboratory. The experimental details and the preliminary results for the Caltech 49 GPa experiment were presented at LPSC last year. Here, we report the results for the 21 GPa experiment at JSC and compare these results to obtain further insight into the mechanism of the bleb formation in the GRIM glasses.

Results of stainless steel canister corrosion studies and environmental sample investigations

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

Bryan, Charles R.; Enos, David

2014-12-01

This progress report describes work being done at Sandia National Laboratories (SNL) to assess the localized corrosion performance of container/cask materials used in the interim storage of used nuclear fuel. The work involves both characterization of the potential physical and chemical environment on the surface of the storage canisters and how it might evolve through time, and testing to evaluate performance of the canister materials under anticipated storage conditions. To evaluate the potential environment on the surface of the canisters, SNL is working with the Electric Power Research Institute (EPRI) to collect and analyze dust samples from the surface ofmore » in-service SNF storage canisters. In FY 13, SNL analyzed samples from the Calvert Cliffs Independent Spent Fuel Storage Installation (ISFSI); here, results are presented for samples collected from two additional near-marine ISFSI sites, Hope Creek NJ, and Diablo Canyon CA. The Hope Creek site is located on the shores of the Delaware River within the tidal zone; the water is brackish and wave action is normally minor. The Diablo Canyon site is located on a rocky Pacific Ocean shoreline with breaking waves. Two types of samples were collected: SaltSmart™ samples, which leach the soluble salts from a known surface area of the canister, and dry pad samples, which collected a surface salt and dust using a swipe method with a mildly abrasive ScotchBrite™ pad. The dry samples were used to characterize the mineralogy and texture of the soluble and insoluble components in the dust via microanalytical techniques, including mapping X-ray Fluorescence spectroscopy and Scanning Electron Microscopy. For both Hope Creek and Diablo Canyon canisters, dust loadings were much higher on the flat upper surfaces of the canisters than on the vertical sides. Maximum dust sizes collected at both sites were slightly larger than 20 μm, but Phragmites grass seeds ~1 mm in size, were observed on the tops of the Hope Creek canisters. At both sites, the surface dust could be divided into fractions generated by manufacturing processes and by natural processes. The fraction from manufacturing processes consisted of variably-oxidized angular and spherical particles of stainless steel and iron, generated by machining and welding/cutting processes, respectively. Dust from natural sources consisted largely of detrital quartz and aluminosilicates (feldspars and clays) at both sites. At Hope Creek, soluble salts were dominated by sulfates and nitrates, mostly of calcium. Chloride was a trace component and the only chloride mineral observed by SEM was NaCl. Chloride surface loads measured by the Saltsmart™ sensors were very low, less than 60 mg m –2 on the canister top, and less than 10 mg m –2 on the canister sides. At Diablo Canyon, sea-salt aggregates of NaCl and Mg-SO 4, with minor K and Ca, were abundant in the dust, in some cases dominating the observed dust assemblage. Measured Saltsmart™ chloride surface loads were very low (<5 mg m –2); however, high canister surface temperatures damaged the Saltsmart™ sensors, and, in view of the SEM observations of abundant sea-salts on the package surfaces, the measured surface loads may not be valid. Moreover, the more heavily-loaded canister tops at Diablo Canyon were not sampled with the Saltsmart™ sensors. The observed low surface loads do not preclude chloride-induced stress corrosion cracking (CISCC) at either site, because (1) the measured data may not be valid for the Diablo Canyon canisters; (2) the surface coverage was not complete (for instance, the 45º offset between the outlet and inlet vents means that near-inlet areas, likely to have heavier dust and salt loads, were not sampled); and (3) CISCC has been experimentally been observed at salt loads as low as 5-8 mg/m 2. Experimental efforts at SNL to assess corrosion of interim storage canister materials include three tasks in FY14. First, a full-diameter canister mockup, made using materials and techniques identical to those used to make interim storage canisters, was designed and ordered from Ranor Inc., a cask vendor for Areva/TN. The mockup will be delivered prior to the end of FY14, and will be used for evaluating weld residual stresses and degrees of sensitization for typical interim storage canister welds. Following weld characterization, the mockup will be sectioned and provided to participating organizations for corrosion testing purposes. A test plan is being developed for these efforts. In a second task, experimental work was carried out to evaluate crevice corrosion of 304SS in the presence of limited reactants, as would be present on a dustcovered storage canister. This work tests the theory that limited salt loads will limit corrosion penetration over time, and is a continuation of work carried out in FY13. Laser confocal microscopy was utilized to assess the volume and depth of corrosion pits formed during the crevice corrosion tests. Results indicate that for the duration of the current experiments (100 days), no stifling of corrosion occurred due to limitations in the amount of reactants present at three different salt loadings. Finally, work has been carried out this year perfecting an instrument for depositing sea-salts onto metal surfaces for atmospheric corrosion testing purposes. The system uses an X-Y plotter system with a commercial airbrush, and deposition is monitored with a quartz crystal microbalance. The system is capable of depositing very even salt loadings, even at very low total deposition rates.« less

Increased Melting of Glaciers during Cotopaxi volcano awakening in 2015

NASA Astrophysics Data System (ADS)

Ramon, Patricio; Vallejo, Silvia; Almeida, Marco; Gomez, Juan Pablo; Caceres, Bolivar

2016-04-01

Cotopaxi (5897 m), located about 50 km south of Quito (Ecuador), is one of the most active volcanoes in the Andes and its historical eruptions have caused a great impact on the population by the generation of lahars along its three main drainages (N, S, E). Starting on April 2015 the seismic monitoring networks and the SO2 gas detection network in May 2015 showed a significant increase from their background values, in June a geodetic instrument located in the NE flank started to record inflation; all this indicated the beginning of a new period of unrest. On August 14, five small phreatic explosions occurred, accompanied by large gas and ash emissions, ash falls were reported to the W of the volcano and to the S of Quito capital city. Three new episodes of ash and gas emissions occurred afterwards and towards the end of November 2015, the different monitoring parameters indicated a progressive reduction in the activity of the volcano. Since August 18 almost weekly overflights were made in order to conduct thermal (FLIR camera), visual and SO2 gas monitoring. Towards the end of August thermal measurements showed for the first time the presence of new thermal anomalies (13.5 to 16.3 °C) located in the crevices of the N glaciers, at the same time fumarolic gases were observed coming out from those fractures. On a flight made on September 3, the presence of water coming out from the basal fronts of the northern glaciers was clearly observed and the formation of narrow streams of water running downslope, while it was evident the appearance of countless new crevices in the majority of glacier ends, but also new cracks and rockslides on the upper flanks. All this led to the conclusion that an abnormal process was producing the melting of the glaciers around the volcano. Starting on September it was possible to observe the presence of small secondary lahars descending several streams and we estimated that many of them are due to increased glacier melting. Later observations made until the end of last year showed an increase of the phenomena already described. Thanks to the collaboration of the Military Geographic Institute of Ecuador (IGM), orthophotos of the volcano made on August 18 and then again on October 8, shows a decrease in the area covered by glaciers of about 0.49 km2 (annual projection of 3.51 km2), this value compared to the decrease of glacier areas since 1976, shows a very high rate of glacier melting, not explained exclusively by climate change phenomena. It is estimated that small volumes of magma reached surface levels through the volcano conduits causing increased circulation of hot fluids inside the edifice, which are apparently reaching the basal area of the glaciers and producing a major melting thereof. It is necessary to further investigate hazard due to the instability in the melting glaciers of Cotopaxi and their eventual collapse which could lead to greater secondary lahars.

Four Ca2+ Ions Activate TRPM2 Channels by Binding in Deep Crevices near the Pore but Intracellularly of the Gate

PubMed Central

Törőcsik, Beáta

2009-01-01

TRPM2 is a tetrameric Ca2+-permeable channel involved in immunocyte respiratory burst and in postischaemic neuronal death. In whole cells, TRPM2 activity requires intracellular ADP ribose (ADPR) and intra- or extracellular Ca2+, but the mechanism and the binding sites for Ca2+ activation remain unknown. Here we study TRPM2 gating in inside-out patches while directly controlling intracellular ligand concentrations. Concentration jump experiments at various voltages and Ca2+ dependence of steady-state single-channel gating kinetics provide unprecedented insight into the molecular mechanism of Ca2+ activation. In patches excised from Xenopus laevis oocytes expressing human TRPM2, coapplication of intracellular ADPR and Ca2+ activated ∼50-pS nonselective cation channels; K1/2 for ADPR was ∼1 µM at saturating Ca2+. Intracellular Ca2+ dependence of TRPM2 steady-state opening and closing rates (at saturating [ADPR] and low extracellular Ca2+) reveals that Ca2+ activation is a consequence of tighter binding of Ca2+ in the open rather than in the closed channel conformation. Four Ca2+ ions activate TRPM2 with a Monod-Wymann-Changeux mechanism: each binding event increases the open-closed equilibrium constant ∼33-fold, producing altogether 106-fold activation. Experiments in the presence of 1 mM of free Ca2+ on the extracellular side clearly show that closed channels do not sense extracellular Ca2+, but once channels have opened Ca2+ entering passively through the pore slows channel closure by keeping the “activating sites” saturated, despite rapid continuous Ca2+-free wash of the intracellular channel surface. This effect of extracellular Ca2+ on gating is gradually lost at progressively depolarized membrane potentials, where the driving force for Ca2+ influx is diminished. Thus, the activating sites lie intracellularly from the gate, but in a shielded crevice near the pore entrance. Our results suggest that in intact cells that contain micromolar ADPR a single brief puff of Ca2+ likely triggers prolonged, self-sustained TRPM2 activity. PMID:19171771

Horse heart ferricytochrome c: conformation and heme configuration of high ionic strength acidic forms.

PubMed

Myer, Y P; Saturno, A F

1991-10-01

The absorption, circular dichroism, and resonance Raman spectra of horse heart ferricytochrome c in the presence of 0.2 M KCl, 0.1 M NaClO4, and 0.2 M KNO3, in the pH region 7 to 0.5, have been investigated to determine the nature and the course of the processes involved. As in the absence of salts (Myer, Y., and Saturno, A. F. (1990) J. Protein Chem, 9, 379-387), the change from neutral to low acidic pH's in the presence of salts is a three-step process: state IIIs----state IIIS,a----state IIS----state IS, with pKa's of 3.5 +/- 0.2, 2.2 +/- 0.2, and 1.1 +/- 0.2, and with two, one, and one number of protons, respectively. The addition of salts at neutral pH's has little or no effect on the protein conformation and the heme-iron configuration (i.e., they remain the same, low-spin hexacoordinated heme iron with a Met-80-Fe-His-18 axial coordination), but such addition does cause a slight tightening of the heme crevice and the enlargement of the porphyrin core. State IIIS,a is a folded state with about the same degree of folding and with a similar spin state and coordination configuration of iron, but the heme crevice is loosened and the porphyrin core is smaller. Both states IIS and IS are also essentially folded forms, but with a smaller degree of protein secondary structure. State IIS has a high-spin hexacoordinated heme iron with a water molecular and a protonated and/or hydrogen-bonded imidazole of his-18 as the two axial ligates; and state IS has a high-spin pentacoordinated heme iron, which is about 0.49 A out of the porphyrin plane, with a protonated and/or hydrogen-bonded imidazole nitrogen as the only axial ligate. The addition of anions causes the stabilization of the protein secondary structures and the state IIIa----state II transition. The mode of effectiveness of anions appears to be nonspecific (i.e., because of electrostatic shielding and/or disruption of salt bridges).

OCSEGen: Open Components and Systems Environment Generator

NASA Technical Reports Server (NTRS)

Tkachuk, Oksana

2014-01-01

To analyze a large system, one often needs to break it into smaller components.To analyze a component or unit under analysis, one needs to model its context of execution, called environment, which represents the components with which the unit interacts. Environment generation is a challenging problem, because the environment needs to be general enough to uncover unit errors, yet precise enough to make the analysis tractable. In this paper, we present a tool for automated environment generation for open components and systems. The tool, called OCSEGen, is implemented on top of the Soot framework. We present the tool's current support and discuss its possible future extensions.

Environmental and alloying effects on corrosion of metals and alloys

NASA Astrophysics Data System (ADS)

Liang, Dong

2009-12-01

In the first part of this project, corrosion studies were carried out on 304L stainless steel samples welded with Cr-free consumables, which were developed to minimize the concentration of chromate species in the weld fume. The corrosion properties of Ni-Cu and Ni-Cu-Pd Gas Tungsten Arc (GTA) welds and Shielded Metal Arc (SMA) welds are comparable to those of welds fabricated with SS308L consumable, which is the standard consumable for welding 304L. Although the breakdown potentials of the new welds from both welding processes are lower than that of the SS308L weld, the repassivation potential of these new welds is much higher. Generally, the repassivation potential is a more conservative measure of susceptibility to localized corrosion. Our studies showed that the Ni-Cu and Ni-Cu-Pd welds are more resistant to crevice corrosion than SS308L welds, which is related to the high repassivation potential. Also, addition of Pd improved the corrosion resistance of the new welds, which is consistent with previous studies from button samples and bead-on-plate samples. Other corrosion studies such as creviced and uncreviced long time immersion, atmospheric exposure, and slow strain rate testing suggest that Ni-Cu-Pd welds can be a qualified substitute for SS308 weld. In the second part of this project, efforts are put on the connection between lab and field exposure tests because sometimes the correspondence between lab atmospheric corrosion tests (ASTM B117) and field exposures is poor as a result of differences in the critical conditions controlling chemical and electrochemical reactions on surfaces. Recent studies in atmospheric chemistry revealed the formation of extremely reactive species from interactions between UV light, chloride aerosols above oceans and oxidizing agents such as ozone or peroxide. Atmospheric corrosion of metals can be affected by these species which might be transported long distances in the atmosphere to locations far from oceans. However, these species could be missed in standard laboratory exposures such as ASTM B117. Initial efforts focused on the effects UV radiation, O3, relative humidity on the atmospheric corrosion of bare silver. Later work addressed the corrosion of silver samples deposited with NaCl particles. An exposure chamber that can simulate various environmental effects was built. The effects of UV radiation, O3, and relative humidity were varied separately while keeping the other factors the same level. The corrosion products were analyzed by the galvanostatic reduction method and characterization techniques such as SEM and EDS. It was found that both UV and O3 are necessary for fast corrosion on bare silver and this fast corrosion reaction results from atomic oxygen generated photodegradation of O3. In the presence of UV and O3, relative humidity has little effect on the atmospheric corrosion of bare silver in contrast to conventional atmospheric corrosion. The degree of corrosion is found to increase with O3 concentration. Moreover, a kinetic study of atmospheric corrosion of bare silver found that an incubation time for the atmospheric corrosion attack is needed. This incubation time is related to the chemisorption process of atomic oxygen. Though UV radiation can form reactive atomic oxygen which is more reactive than O3 alone as shown in the last chapter, the enhancement of corrosion by UV is limited for Ag with NaCl particles at low ozone concentration and high RH. The corrosion rate of silver with NaCl particles is found to increase with relative humidity, which is different than the case of bare silver. This indicates that different mechanisms control the atmospheric corrosion of silver. The incubation time for corrosion of silver with NaCl particles is shorter than for bare silver. This result from chemisorption of Cl 2 is favored over that of atomic oxygen. Interestingly, the total corrosion product of silver with NaCl particles is less than that of bare silver. This could be due to limited amount of NaCl and also higher oxidizing power of atomic oxygen. Finally, bare silver samples were exposed in salt spray chamber according to ASTM B117 up to 4 months. Very little corrosion products were detected after exposure, which is attributed to the lack of reactive species such as O and O3 in the environment. (Abstract shortened by UMI.)

EMERGE: Engineered Materials that Create Environments for ReGeneration via Electric Field

DTIC Science & Technology

2016-10-01

Recruitment of multiple cell lines by collagen-synthetic copolymer matrices in corneal regeneration ,” Biomaterials (2004). A) B) REDD-2016-537...AWARD NUMBER: W81XWH-14-1-0542 TITLE: EMERGE: Engineered Materials that Create Environments for ReGeneration via Electric Field PRINCIPAL...23 Sep 2016 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER EMERGE: Engineered Materials that Create Environments for ReGeneration via Electric Field

Automated Environment Generation for Software Model Checking

NASA Technical Reports Server (NTRS)

Tkachuk, Oksana; Dwyer, Matthew B.; Pasareanu, Corina S.

2003-01-01

A key problem in model checking open systems is environment modeling (i.e., representing the behavior of the execution context of the system under analysis). Software systems are fundamentally open since their behavior is dependent on patterns of invocation of system components and values defined outside the system but referenced within the system. Whether reasoning about the behavior of whole programs or about program components, an abstract model of the environment can be essential in enabling sufficiently precise yet tractable verification. In this paper, we describe an approach to generating environments of Java program fragments. This approach integrates formally specified assumptions about environment behavior with sound abstractions of environment implementations to form a model of the environment. The approach is implemented in the Bandera Environment Generator (BEG) which we describe along with our experience using BEG to reason about properties of several non-trivial concurrent Java programs.

First description of the nest, eggs, and breeding behavior of the Mérida Tapaculo (Scytalopus meridanus)

USGS Publications Warehouse

Decker, Karie L.; Niklison, Alina M.; Martin, Thomas E.

2007-01-01

We provide the first description of the nest, eggs, and breeding behavior of the Mérida Tapaculo (Scytalopus meridanus). Data are from one pair in the moist cloud forest of Yacambu National Park, Venezuela during April–May 2004. Two nests, constructed by the same pair, were globular in structure and consisted of mossy material placed in a rock crevice of a muddy rock wall. The eggs were cream colored with an average mass of 4.19 g. Clutch sizes were one in the first nest and two in the second. The species showed bi-parental care in nest building and incubation. Nest attentiveness (percent time spent on the nest incubating) averaged 83.4 ± 14% (SD). Average on and off bouts were 33.24 and 6.34 min, respectively.

Corrosion on the acetabular liner taper from retrieved modular metal-on-metal total hip replacements.

PubMed

Gascoyne, Trevor C; Dyrkacz, Richard M; Turgeon, Thomas R; Burnell, Colin D; Wyss, Urs P; Brandt, Jan-M

2014-10-01

Eight retrieved metal-on-metal total hip replacements displayed corrosion damage along the cobalt-chromium alloy liner taper junction with the Ti alloy acetabular shell. Scanning electron microscopy indicated the primary mechanism of corrosion to be grain boundary and associated crevice corrosion, which was likely accelerated through mechanical micromotion and galvanic corrosion resulting from dissimilar alloys. Coordinate measurements revealed up to 4.3mm(3) of the cobalt-chromium alloy taper surface was removed due to corrosion, which is comparable to previous reports of corrosion damage on head-neck tapers. The acetabular liner-shell taper appears to be an additional source of metal corrosion products in modular total hip replacements. Patients with these prostheses should be closely monitored for signs of adverse reaction towards corrosion by-products. Copyright © 2014 Elsevier Inc. All rights reserved.

Ctenocheloides almeidai sp. nov., a new ghost shrimp from Brazil (Decapoda, Ctenochelidae).

PubMed

Anker, Arthur; Pachelle, Paulo P G

2013-02-13

A second species of the ctenochelid genus Ctenocheloides Anker, 2010 is described based on a single female specimen collected on a rocky reef in front of Maceió, Alagoas, northeastern Brazil. Ctenocheloides almeidai sp. nov. represents the first record of Ctenocheloides in the Atlantic Ocean. The new species differs from C. attenboroughi Anker, 2010, the type species from Madagascar, in the number of teeth in the crista dentata of the third maxilliped, the proportions and armature of the major and minor chelipeds, and several other characters. The microhabitats of C. almeidai sp. nov. and C. attenboroughi are remarkably similar: both species inhabit burrows made in rock crevices cemented by compact clay-like silt, at very shallow depths (1-1.5 m). A key to the western Atlantic species of the family Ctenochelidae is provided.

A method for the imbibition and germination of wheat seeds in space

NASA Technical Reports Server (NTRS)

Levine, H. G.; Piastuch, W. C.; Sager, J. C. (Principal Investigator)

1999-01-01

A method was developed for the reliable germination in space of wheat seeds on porous tube nutrient delivery systems. Germination paper strips were loosely rolled into cylinders and two seeds inserted close to the outer edges of each cylinder. This configuration: 1) directed the emerging shoots upward and roots downward, 2) was efficient in wicking moisture from the porous tubes, and 3) provided open areas for oxygen diffusion. Cotton tufts were inserted into the bottom crevices of the cylinders to fix the seeds in a mid-level position and cylinders were then storable (indefinitely) prior to the preprogrammed (on-orbit) initiation of imbibition. This method extends both the upper and lower ends of acceptable moisture levels for successful seed germination, increasing the probability of success for spaceflight applications where moisture availability is more variable than on Earth.

Gene Regulation, Two Component Regulatory Systems, and Adaptive Responses in Treponema Denticola.

PubMed

Marconi, Richard T

2017-10-13

The oral microbiome consists of a remarkably diverse group of 500-700 bacterial species. The microbial etiology of periodontal disease is similarly complex. Of the ~400 bacterial species identified in subgingival plaque, at least 50 belong to the genus Treponema. As periodontal disease develops and progresses, T. denticola transitions from a low to high abundance species in the subgingival crevice. Changes in the overall composition of the bacterial population trigger significant changes in the local physical, immunological and physiochemical conditions. For T. denticola to thrive in periodontal pockets, it must be nimble and adapt to rapidly changing environmental conditions. The purpose of this chapter is to review the current understanding of the molecular basis of these essential adaptive responses, with a focus on the role of two component regulatory systems with global regulatory potential.

Dissecting biological “dark matter” with single-cell genetic analysis of rare and uncultivated TM7 microbes from the human mouth

PubMed Central

Marcy, Yann; Ouverney, Cleber; Bik, Elisabeth M.; Lösekann, Tina; Ivanova, Natalia; Martin, Hector Garcia; Szeto, Ernest; Platt, Darren; Hugenholtz, Philip; Relman, David A.; Quake, Stephen R.

2007-01-01

We have developed a microfluidic device that allows the isolation and genome amplification of individual microbial cells, thereby enabling organism-level genomic analysis of complex microbial ecosystems without the need for culture. This device was used to perform a directed survey of the human subgingival crevice and to isolate bacteria having rod-like morphology. Several isolated microbes had a 16S rRNA sequence that placed them in candidate phylum TM7, which has no cultivated or sequenced members. Genome amplification from individual TM7 cells allowed us to sequence and assemble >1,000 genes, providing insight into the physiology of members of this phylum. This approach enables single-cell genetic analysis of any uncultivated minority member of a microbial community. PMID:17620602

Generational diversity: what nurse managers need to know.

PubMed

Hendricks, Joyce M; Cope, Vicki C

2013-03-01

This article presents a discussion of generational differences and their impact on the nursing workforce and how this impact affects the work environment. The global nursing workforce represents four generations of nurses. This generational diversity frames attitudes, beliefs, work habits and expectations associated with the role of the nurse in the provision of care and in the way the nurse manages their day-to-day activities. An electronic search of MEDLINE, PubMed and Cinahl databases was performed using the words generational diversity, nurse managers and workforce. The search was limited to 2000-2012. Generational differences present challenges to contemporary nurse managers working in a healthcare environment which is complex and dynamic, in terms of managing nurses who think and behave in a different way because of disparate core personal and generational values, namely, the three Cs of communication, commitment and compensation. An acceptance of generational diversity in the workplace allows a richer scope for practice as the experiences and knowledge of each generation in the nursing environment creates an environment of acceptance and harmony facilitating retention of nurses. Acknowledgement of generational characteristics provides the nurse manager with strategies which focus on mentoring and motivation; communication, the increased use of technology and the ethics of nursing, to bridge the gap between generations of nurses and to increase nursing workforce cohesion. © 2012 Blackwell Publishing Ltd.

The Millennial Generation: Developing Leaders for the Future Security Environment

DTIC Science & Technology

2011-02-15

Dumbest Generation (Penguin Group, New York, New York: 2009) p 8, 10. 19 National Academy of Sciences, “Generation Y : The Millennials …Ready or Not, Here...St ra te gy R es ea rc h Pr oj ec t THE MILLENNIAL GENERATION: DEVELOPING LEADERS FOR THE FUTURE SECURITY ENVIRONMENT BY COLONEL LANCE...Strategy Research Project 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE The Millennial Generation: Developing Leaders for the Future

Ontogenetic scaling of burrowing forces in the earthworm Lumbricus terrestris.

PubMed

Quillin, K J

2000-09-01

In hydrostatic skeletons, it is the internal fluid under pressure surrounded by a body wall in tension (rather than a rigid lever) that enables the stiffening of the organism, the antagonism of muscles and the transmission of force from the muscles to the environment. This study examined the ontogenetic effects of body size on force production by an organism supported with a hydrostatic skeleton. The earthworm Lumbricus terrestris burrows by forcefully enlarging crevices in the soil. I built a force-measuring apparatus that measured the radial forces as earthworms of different sizes crawled through and enlarged pre-formed soil burrows. I also built an apparatus that measured the radial and axial forces as earthworms of different sizes attempted to elongate a dead-end burrow. Earthworms ranging in body mass m(b) from hatchlings (0.012 g) to adults (8.9 g) exerted maximum forces (F, in N) during active radial expansion of their burrows (F=0.32 m(b)(0.43)) and comparable forces during axial elongation of the burrow (F=0.26 m(b)(0.47)). Both these forces were almost an order of magnitude greater than the radial anchoring forces during normal peristalsis within burrows (F=0.04 m(b)(0.45)). All radial and axial forces scaled as body mass raised to the 2/5 power rather than to the 2/3 power expected by geometric similarity, indicating that large worms exert greater forces than small worms on an absolute scale, but the difference was less than predicted by scaling considerations. When forces were normalized by body weight, hatchlings could push 500 times their own body weight, while large adults could push only 10 times their own body weight.

Multiscale molecular dynamics simulations of lipid interactions with P-glycoprotein in a complex membrane.

PubMed

Domicevica, Laura; Koldsø, Heidi; Biggin, Philip C

2018-03-01

P-glycoprotein (P-gp) can transport a wide range of very different hydrophobic organic molecules across the membrane. Its ability to extrude molecules from the cell creates delivery problems for drugs that target proteins in the central nervous system (CNS) and also causes drug-resistance in many forms of cancer. Whether a drug will be susceptible to export by P-gp is difficult to predict and currently this is usually assessed with empirical and/or animal models. Thus, there is a need to better understand how P-gp works at the molecular level in order to fulfil the 3Rs: Refinement, reduction and replacement of animals in research. As structural information increasingly becomes available, our understanding at the molecular level improves. Proteins like P-gp are however very dynamic entities and thus one of the most appropriate ways to study them is with molecular dynamics simulations, especially as this can capture the influence of the surrounding environment. Recent parameterization developments have meant that it is now possible to simulate lipid bilayers that more closely resemble in vivo membranes in terms of their composition. In this report we construct a complex lipid bilayer that mimics the composition of brain epithelial cells and examine the interactions of it with P-gp. We find that the negatively charged phosphatidylserine lipids in the inner leaflet of the membrane tend to form an annulus around P-gp. We also observed the interaction of cholesterol with three distinct areas of the P-gp. Potential of mean force (PMF) calculations suggest that a crevice between transmembrane helices 10 and 12 has particularly favourable interaction energy for cholesterol. Copyright © 2018 Elsevier Inc. All rights reserved.

Multiscale molecular dynamics simulations of lipid interactions with P-glycoprotein in a complex membrane.

PubMed

Domicevica, Laura; Koldsø, Heidi; Biggin, Philip C

2017-09-02

P-glycoprotein (P-gp) can transport a wide range of very different hydrophobic organic molecules across the membrane. Its ability to extrude molecules from the cell creates delivery problems for drugs that target proteins in the central nervous system (CNS) and also causes drug-resistance in many forms of cancer. Whether a drug will be susceptible to export by P-gp is difficult to predict and currently this is usually assessed with empirical and/or animal models. Thus, there is a need to better understand how P-gp works at the molecular level in order to fulfil the 3Rs: Refinement, reduction and replacement of animals in research. As structural information increasingly becomes available, our understanding at the molecular level improves. Proteins like P-gp are however very dynamic entities and thus one of the most appropriate ways to study them is with molecular dynamics simulations, especially as this can capture the influence of the surrounding environment. Recent parameterization developments have meant that it is now possible to simulate lipid bilayers that more closely resemble in vivo membranes in terms of their composition. In this report we construct a complex lipid bilayer that mimics the composition of brain epithelial cells and examine the interactions of it with P-gp. We find that the negatively charged phosphatidylserine lipids in the inner leaflet of the membrane tend to form an annulus around P-gp. We also observed the interaction of cholesterol with three distinct areas of the P-gp. Potential of mean force (PMF) calculations suggest that a crevice between transmembrane helices 10 and 12 has particularly favourable interaction energy for cholesterol. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Tutorial on Atomic Oxygen Effects and Contamination

NASA Technical Reports Server (NTRS)

Miller, Sharon K.

2017-01-01

Atomic oxygen is the most predominant specie in low Earth orbit (LEO) and is contained in the upper atmosphere of many other planetary bodies. Formed by photo-dissociation of molecular oxygen, it is highly reactive and energetic enough to break chemical bonds on the surface of many materials and react with them to form either stable or volatile oxides. The extent of the damage for spacecraft depends a lot on how much atomic oxygen arrives at the surface, the energy of the atoms, and the reactivity of the material that is exposed to it. Oxide formation can result in shrinkage, cracking, or erosion which can also result in changes in optical, thermal, or mechanical properties of the materials exposed. The extent of the reaction can be affected by mechanical loading, temperature, and other environmental components such as ultraviolet radiation or charged particles. Atomic oxygen generally causes a surface reaction, but it can scatter under coatings and into crevices causing oxidation much farther into a spacecraft surface or structure than would be expected. Contamination can also affect system performance. Contamination is generally caused by arrival of volatile species that condense on spacecraft surfaces. The volatiles are typically a result of outgassing of materials that are on the spacecraft. Once the volatiles are condensed on a surface, they can then be fixed on the surface by ultraviolet radiation andor atomic oxygen reaction to form stable surface contaminants that can change optical and thermal properties of materials in power systems, thermal systems, and sensors. This tutorial discusses atomic oxygen erosion and contaminate formation, and the effect they have on typical spacecraft materials. Scattering of atomic oxygen, some effects of combined environments and examples of effects of atomic oxygen and contamination on spacecraft systems and components will also be presented.

Effect of Glucose Concentration on Electrochemical Corrosion Behavior of Pure Titanium TA2 in Hanks’ Simulated Body Fluid

PubMed Central

Liu, Shuyue; Wang, Bing; Zhang, Peirong

2016-01-01

Titanium and its alloys have been widely used as implant materials due to their excellent mechanical property and biocompatibility. In the present study, the effect of glucose concentration on corrosion behavior of pure titanium TA2 in Hanks’ simulated body fluid is investigated by the electrochemical impedance spectrum (EIS) and potentiodynamic polarization methods. The range of glucose concentrations investigated in this research includes 5 mmol/L (limosis for healthy people), 7 mmol/L (after diet for healthy people), 10 mmol/L (limosis for hyperglycemia patient), and 12 mmol/L (after diet for hyperglycemia patient), as well as, 15 mmol/L and 20 mmol/L, which represent different body fluid environments. The results indicate that the pure titanium TA2 demonstrates the best corrosion resistance when the glucose concentration is less than 10 mmol/L, which shows that the pure titanium TA2 as implant material can play an effective role in the body fluids with normal and slight high glucose concentrations. Comparatively, the corrosion for the pure titanium implant is more probable when the glucose concentration is over 10 mmol/L due to the premature penetration through passive film on the material surface. Corrosion defects of pitting and crevice exist on the corroded surface, and the depth of corrosion is limited to three microns with a low corrosion rate. The oxidation film on the surface of pure titanium TA2 has a protective effect on the corrosion behavior of the implant inner material. The corrosion behavior of pure titanium TA2 will happen easily once the passive film has been penetrated through. The corrosion rate for TA2 implant will accelerate quickly and a pure titanium implant cannot be used. PMID:28773993

Summary of miscellaneous hazard environments for hypothetical Space Shuttle and Titan IV launch abort accidents

NASA Technical Reports Server (NTRS)

Eck, M.; Mukunda, M.

1989-01-01

The various analyses described here were aimed at obtaining a more comprehensive understanding and definition of the environments in the vicinity of the Radioisotope Thermal Generator (RTG) during certain Space Transportation System (STS) and Titan IV launch abort accidents. Addressed here are a number of issues covering explosion environments and General Purpose Heat Source Radioisotope Thermoelectric Generator (GPHS-RTG) responses to those environments.

Tobacco environment for Southeast Asian American youth: Results from a participatory research project

PubMed Central

Lee, Juliet P.; Lipperman-Kreda, Sharon; Saephan, Sang; Kirkpatrick, Sean

2013-01-01

Despite reports of high rates of smoking among Southeast Asian refugees in the U.S., few studies have described environmental aspects of tobacco use among this population, particularly for the second generation of youths. This absence is notable, as the social environment within which second-generation youths are exposed to tobacco products differs radically from the natal environment of their parents. We describe results of a youth-led community participatory research project for Southeast Asians in Northern California. Using multiple data sources, second-generation youths documented the salience of tobacco products in their social environment, notably products such as “blunts” and mentholated cigarettes. PMID:23480210

Creating Next Generation Blended Learning Environments Using Mixed Reality, Video Games and Simulations

ERIC Educational Resources Information Center

Kirkley, Sonny E.; Kirkley, Jamie R.

2005-01-01

In this article, the challenges and issues of designing next generation learning environments using current and emerging technologies are addressed. An overview of the issues is provided as well as design principles that support the design of instruction and the overall learning environment. Specific methods for creating cognitively complex,…

The legacy of disadvantage: multigenerational neighborhood effects on cognitive ability.

PubMed

Sharkey, Patrick; Elwert, Felix

2011-05-01

This study examines how the neighborhood environments experienced over multiple generations of a family influence children's cognitive ability. Building on recent research showing strong continuity in neighborhood environments across generations of family members, the authors argue for a revised perspective on "neighborhood effects" that considers the ways in which the neighborhood environment in one generation may have a lingering impact on the next generation. To analyze multigenerational effects, the authors use newly developed methods designed to estimate unbiased treatment effects when treatments and confounders vary over time. The results confirm a powerful link between neighborhoods and cognitive ability that extends across generations. A family's exposure to neighborhood poverty across two consecutive generations reduces child cognitive ability by more than half a standard deviation. A formal sensitivity analysis suggests that results are robust to unobserved selection bias.

Adaptive Practice: Next Generation Evidence-Based Practice in Digital Environments.

PubMed

Kennedy, Margaret Ann

2016-01-01

Evidence-based practice in nursing is considered foundational to safe, competent care. To date, rigid traditional perceptions of what constitutes 'evidence' have constrained the recognition and use of practice-based evidence and the exploitation of novel forms of evidence from data rich environments. Advancements such as the conceptualization of clinical intelligence, the prevalence of increasingly sophisticated digital health information systems, and the advancement of the Big Data phenomenon have converged to generate a new contemporary context. In today's dynamic data-rich environments, clinicians have new sources of valid evidence, and need a new paradigm supporting clinical practice that is adaptive to information generated by diverse electronic sources. This opinion paper presents adaptive practice as the next generation of evidence-based practice in contemporary evidence-rich environments and provides recommendations for the next phase of evolution.

A qualitative study of factors influencing different generations of Newfoundland and Saskatchewan trained physicians to leave a work location.

PubMed

Mathews, Maria; Seguin, Maureen; Chowdhury, Nurun; Card, Robert T

2012-07-25

Some studies have suggested that young physicians may have different expectations and practice behaviours than their older generational counterparts, including their reasons for wanting to remain or leave a community. This study examined the factors associated with a physician's decision to leave a work location. We compared different generations of physicians to assess whether these factors have changed over generations. We conducted semi-structured, qualitative interviews with 48 physicians who graduated from two Canadian medical schools. We asked each physician about the number and nature of work location changes and the factors related to their decisions to leave each location. Interview transcripts and notes were analysed using a thematic analysis approach. Dissatisfaction with the working environment was the most frequently cited reason for leaving a location for physicians of all generations. Elements which contributed to the quality of the work environment included the collaborative nature of the practice, the relationship with administrators, and access to resources and personnel. For younger physicians, the work environment had to meet their personal expectations for work-life balance. While remuneration level was given by some physicians as the key reason for leaving a location, for others it was the "last straw" if the work environment was poor. A small number of older generation physicians moved in response to political events and/or policies We documented generational differences in physicians' reasons for choosing a work location. We found that a poor work environment was universally the most important reason why a physician chose to leave a location. A few physicians who were unsatisfied with their work location identified level of remuneration as an additional reason for leaving. Some older generation physicians cited political climate as a reason for leaving a work location. While economic factors have largely been the focus of recruitment and retention initiatives, our findings highlight the importance of the work environment and organizational culture on the retention of physicians of all generations.

Phosphorylation of Cytochrome c Threonine 28 Regulates Electron Transport Chain Activity in Kidney: IMPLICATIONS FOR AMP KINASE

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

Mahapatra, Gargi; Varughese, Ashwathy; Ji, Qinqin

Mammalian cytochrome c (Cytc) plays a key role in cellular life and death decisions, functioning as an electron carrier in the electron transport chain and as a trigger of apoptosis when released from the mitochondria. However, its regulation is not well understood. We show that the major fraction of Cytc isolated from kidneys is phosphorylated on Thr28, leading to a partial inhibition of respiration in the reaction with cytochrome c oxidase. To further study the effect of Cytc phosphorylation in vitro, we generated T28E phosphomimetic Cytc, revealing superior behavior regarding protein stability and its ability to degrade reactive oxygen speciesmore » compared with wild-type unphosphorylated Cytc. Introduction of T28E phosphomimetic Cytc into Cytc knock-out cells shows that intact cell respiration, mitochondrial membrane potential (ΔΨm), and ROS levels are reduced compared with wild type. As we show by high resolution crystallography of wild-type and T28E Cytc in combination with molecular dynamics simulations, Thr28 is located at a central position near the heme crevice, the most flexible epitope of the protein apart from the N and C termini. Finally, in silico prediction and our experimental data suggest that AMP kinase, which phosphorylates Cytc on Thr28 in vitro and colocalizes with Cytc to the mitochondrial intermembrane space in the kidney, is the most likely candidate to phosphorylate Thr28 in vivo. We conclude that Cytc phosphorylation is mediated in a tissue-specific manner and leads to regulation of electron transport chain flux via “controlled respiration,” preventing ΔΨm hyperpolarization, a known cause of ROS and trigger of apoptosis.« less

Plurigon: three dimensional visualization and classification of high-dimensionality data

PubMed Central

Martin, Bronwen; Chen, Hongyu; Daimon, Caitlin M.; Chadwick, Wayne; Siddiqui, Sana; Maudsley, Stuart

2013-01-01

High-dimensionality data is rapidly becoming the norm for biomedical sciences and many other analytical disciplines. Not only is the collection and processing time for such data becoming problematic, but it has become increasingly difficult to form a comprehensive appreciation of high-dimensionality data. Though data analysis methods for coping with multivariate data are well-documented in technical fields such as computer science, little effort is currently being expended to condense data vectors that exist beyond the realm of physical space into an easily interpretable and aesthetic form. To address this important need, we have developed Plurigon, a data visualization and classification tool for the integration of high-dimensionality visualization algorithms with a user-friendly, interactive graphical interface. Unlike existing data visualization methods, which are focused on an ensemble of data points, Plurigon places a strong emphasis upon the visualization of a single data point and its determining characteristics. Multivariate data vectors are represented in the form of a deformed sphere with a distinct topology of hills, valleys, plateaus, peaks, and crevices. The gestalt structure of the resultant Plurigon object generates an easily-appreciable model. User interaction with the Plurigon is extensive; zoom, rotation, axial and vector display, feature extraction, and anaglyph stereoscopy are currently supported. With Plurigon and its ability to analyze high-complexity data, we hope to see a unification of biomedical and computational sciences as well as practical applications in a wide array of scientific disciplines. Increased accessibility to the analysis of high-dimensionality data may increase the number of new discoveries and breakthroughs, ranging from drug screening to disease diagnosis to medical literature mining. PMID:23885241

Evaluation of micro-GPS receivers for tracking small-bodied mammals

PubMed Central

Shipley, Lisa A.; Forbey, Jennifer S.; Olsoy, Peter J.

2017-01-01

GPS telemetry markedly enhances the temporal and spatial resolution of animal location data, and recent advances in micro-GPS receivers permit their deployment on small mammals. One such technological advance, snapshot technology, allows for improved battery life by reducing the time to first fix via postponing recovery of satellite ephemeris (satellite location) data and processing of locations. However, no previous work has employed snapshot technology for small, terrestrial mammals. We evaluated performance of two types of micro-GPS (< 20 g) receivers (traditional and snapshot) on a small, semi-fossorial lagomorph, the pygmy rabbit (Brachylagus idahoensis), to understand how GPS errors might influence fine-scale assessments of space use and habitat selection. During stationary tests, microtopography (i.e., burrows) and satellite geometry had the largest influence on GPS fix success rate (FSR) and location error (LE). There was no difference between FSR while animals wore the GPS collars above ground (determined via light sensors) and FSR generated during stationary, above-ground trials, suggesting that animal behavior other than burrowing did not markedly influence micro-GPS errors. In our study, traditional micro-GPS receivers demonstrated similar FSR and LE to snapshot receivers, however, snapshot receivers operated inconsistently due to battery and software failures. In contrast, the initial traditional receivers deployed on animals experienced some breakages, but a modified collar design consistently functioned as expected. If such problems were resolved, snapshot technology could reduce the tradeoff between fix interval and battery life that occurs with traditional micro-GPS receivers. Our results suggest that micro-GPS receivers are capable of addressing questions about space use and resource selection by small mammals, but that additional techniques might be needed to identify use of habitat structures (e.g., burrows, tree cavities, rock crevices) that could affect micro-GPS performance and bias study results. PMID:28301495

Effects of season, sex and body size on the feeding ecology of turtle-headed sea snakes ( Emydocephalus annulatus) on IndoPacific inshore coral reefs

NASA Astrophysics Data System (ADS)

Goiran, C.; Dubey, S.; Shine, R.

2013-06-01

In terrestrial snakes, many cases of intraspecific shifts in dietary habits as a function of predator sex and body size are driven by gape limitation and hence are most common in species that feed on relatively large prey and exhibit a wide body-size range. Our data on sea snakes reveal an alternative mechanism for intraspecific niche partitioning, based on sex-specific seasonal anorexia induced by reproductive activities. Turtle-headed sea snakes ( Emydocephalus annulatus) on coral reefs in the New Caledonian Lagoon feed entirely on the eggs of demersal-spawning fishes. DNA sequence data (cytochrome b gene) on eggs that we palpated from stomachs of 37 snakes showed that despite this ontogenetic stage specialization, the prey comes from a taxonomically diverse array of species including damselfish (41 % of samples, at least 5 species), blennies (41 %, 4 species) and gobies (19 %, 5 species). The composition of snake diets shifted seasonally (with damselfish dominating in winter but not summer), presumably reflecting seasonality of fish reproduction. That seasonal shift affects male and female snakes differently, because reproduction is incompatible with foraging. Adult female sea snakes ceased feeding when they became heavily distended with developing embryos in late summer, and males ceased feeding while they were mate searching in winter. The sex divergence in foraging habits may be amplified by sexual size dimorphism; females grow larger than males, and larger snakes (of both sexes) feed more on damselfish (which often lay their eggs in exposed sites) than on blennies and gobies (whose eggs are hidden within narrow crevices). Specific features of reproductive biology of coral reef fish (seasonality and nest type) have generated intraspecific niche partitioning in these sea snakes, by mechanisms different from those that apply to terrestrial snakes.

Phosphorylation of Cytochrome c Threonine 28 Regulates Electron Transport Chain Activity in Kidney

PubMed Central

Mahapatra, Gargi; Varughese, Ashwathy; Ji, Qinqin; Lee, Icksoo; Liu, Jenney; Vaishnav, Asmita; Sinkler, Christopher; Kapralov, Alexandr A.; Moraes, Carlos T.; Sanderson, Thomas H.; Stemmler, Timothy L.; Grossman, Lawrence I.; Kagan, Valerian E.; Brunzelle, Joseph S.; Salomon, Arthur R.; Edwards, Brian F. P.; Hüttemann, Maik

2017-01-01

Mammalian cytochrome c (Cytc) plays a key role in cellular life and death decisions, functioning as an electron carrier in the electron transport chain and as a trigger of apoptosis when released from the mitochondria. However, its regulation is not well understood. We show that the major fraction of Cytc isolated from kidneys is phosphorylated on Thr28, leading to a partial inhibition of respiration in the reaction with cytochrome c oxidase. To further study the effect of Cytc phosphorylation in vitro, we generated T28E phosphomimetic Cytc, revealing superior behavior regarding protein stability and its ability to degrade reactive oxygen species compared with wild-type unphosphorylated Cytc. Introduction of T28E phosphomimetic Cytc into Cytc knock-out cells shows that intact cell respiration, mitochondrial membrane potential (ΔΨm), and ROS levels are reduced compared with wild type. As we show by high resolution crystallography of wild-type and T28E Cytc in combination with molecular dynamics simulations, Thr28 is located at a central position near the heme crevice, the most flexible epitope of the protein apart from the N and C termini. Finally, in silico prediction and our experimental data suggest that AMP kinase, which phosphorylates Cytc on Thr28 in vitro and colocalizes with Cytc to the mitochondrial intermembrane space in the kidney, is the most likely candidate to phosphorylate Thr28 in vivo. We conclude that Cytc phosphorylation is mediated in a tissue-specific manner and leads to regulation of electron transport chain flux via “controlled respiration,” preventing ΔΨm hyperpolarization, a known cause of ROS and trigger of apoptosis. PMID:27758862

Phosphorylation of Cytochrome c Threonine 28 Regulates Electron Transport Chain Activity in Kidney: IMPLICATIONS FOR AMP KINASE.

PubMed

Mahapatra, Gargi; Varughese, Ashwathy; Ji, Qinqin; Lee, Icksoo; Liu, Jenney; Vaishnav, Asmita; Sinkler, Christopher; Kapralov, Alexandr A; Moraes, Carlos T; Sanderson, Thomas H; Stemmler, Timothy L; Grossman, Lawrence I; Kagan, Valerian E; Brunzelle, Joseph S; Salomon, Arthur R; Edwards, Brian F P; Hüttemann, Maik

2017-01-06

Mammalian cytochrome c (Cytc) plays a key role in cellular life and death decisions, functioning as an electron carrier in the electron transport chain and as a trigger of apoptosis when released from the mitochondria. However, its regulation is not well understood. We show that the major fraction of Cytc isolated from kidneys is phosphorylated on Thr 28 , leading to a partial inhibition of respiration in the reaction with cytochrome c oxidase. To further study the effect of Cytc phosphorylation in vitro, we generated T28E phosphomimetic Cytc, revealing superior behavior regarding protein stability and its ability to degrade reactive oxygen species compared with wild-type unphosphorylated Cytc Introduction of T28E phosphomimetic Cytc into Cytc knock-out cells shows that intact cell respiration, mitochondrial membrane potential (ΔΨ m ), and ROS levels are reduced compared with wild type. As we show by high resolution crystallography of wild-type and T28E Cytc in combination with molecular dynamics simulations, Thr 28 is located at a central position near the heme crevice, the most flexible epitope of the protein apart from the N and C termini. Finally, in silico prediction and our experimental data suggest that AMP kinase, which phosphorylates Cytc on Thr 28 in vitro and colocalizes with Cytc to the mitochondrial intermembrane space in the kidney, is the most likely candidate to phosphorylate Thr 28 in vivo We conclude that Cytc phosphorylation is mediated in a tissue-specific manner and leads to regulation of electron transport chain flux via "controlled respiration," preventing ΔΨ m hyperpolarization, a known cause of ROS and trigger of apoptosis. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Dynamics and genetic diversification of Escherichia coli during experimental adaptation to an anaerobic environment

PubMed Central

Finn, Thomas J.; Shewaramani, Sonal; Leahy, Sinead C.; Janssen, Peter H.

2017-01-01

Background Many bacteria are facultative anaerobes, and can proliferate in both anoxic and oxic environments. Under anaerobic conditions, fermentation is the primary means of energy generation in contrast to respiration. Furthermore, the rates and spectra of spontaneous mutations that arise during anaerobic growth differ to those under aerobic growth. A long-term selection experiment was undertaken to investigate the genetic changes that underpin how the facultative anaerobe, Escherichia coli, adapts to anaerobic environments. Methods Twenty-one populations of E. coli REL4536, an aerobically evolved 10,000th generation descendent of the E. coli B strain, REL606, were established from a clonal ancestral culture. These were serially sub-cultured for 2,000 generations in a defined minimal glucose medium in strict aerobic and strict anaerobic environments, as well as in a treatment that fluctuated between the two environments. The competitive fitness of the evolving lineages was assessed at approximately 0, 1,000 and 2,000 generations, in both the environment of selection and the alternative environment. Whole genome re-sequencing was performed on random colonies from all lineages after 2,000-generations. Mutations were identified relative to the ancestral genome, and based on the extent of parallelism, traits that were likely to have contributed towards adaptation were inferred. Results There were increases in fitness relative to the ancestor among anaerobically evolved lineages when tested in the anaerobic environment, but no increases were found in the aerobic environment. For lineages that had evolved under the fluctuating regime, relative fitness increased significantly in the anaerobic environment, but did not increase in the aerobic environment. The aerobically-evolved lineages did not increase in fitness when tested in either the aerobic or anaerobic environments. The strictly anaerobic lineages adapted more rapidly to the anaerobic environment than did the fluctuating lineages. Two main strategies appeared to predominate during adaptation to the anaerobic environment: modification of energy generation pathways, and inactivation of non-essential functions. Fermentation pathways appeared to alter through selection for mutations in genes such as nadR, adhE, dcuS/R, and pflB. Mutations were frequently identified in genes for presumably dispensable functions such as toxin-antitoxin systems, prophages, virulence and amino acid transport. Adaptation of the fluctuating lineages to the anaerobic environments involved mutations affecting traits similar to those observed in the anaerobically evolved lineages. Discussion There appeared to be strong selective pressure for activities that conferred cell yield advantages during anaerobic growth, which include restoring activities that had previously been inactivated under long-term continuous aerobic evolution of the ancestor. PMID:28480139

THE LEGACY OF DISADVANTAGE: MULTIGENERATIONAL NEIGHBORHOOD EFFECTS ON COGNITIVE ABILITY1

PubMed Central

Sharkey, Patrick; Elwert, Felix

2012-01-01

This study examines how the neighborhood environments experienced over multiple generations of a family influence children’s cognitive ability. Building on recent research showing strong continuity in neighborhood environments across generations of family members, we argue for a revised perspective on “neighborhood effects” that considers the ways in which the neighborhood environment in one generation may have a lingering impact on the next generation. To specify such multigenerational effects is not simply a theoretical problem, but poses considerable methodological challenges. Instead of traditional regression techniques that may obscure multigenerational effects of neighborhood disadvantage, we utilize newly developed methods designed to generate unbiased treatment effects when treatments and confounders vary over time. The results confirm a powerful link between neighborhoods and cognitive ability that extends across generations. Being raised in a high-poverty neighborhood in one generation has a substantial negative effect on child cognitive ability in the next generation. A family’s exposure to neighborhood poverty across two consecutive generations reduces child cognitive ability by more than half a standard deviation. A formal sensitivity analysis suggests that results are robust to unobserved selection bias. PMID:21932471

Characterization of 316L(N)-IG SS joint produced by hot isostatic pressing technique

NASA Astrophysics Data System (ADS)

Nakano, J.; Miwa, Y.; Tsukada, T.; Kikuchi, M.; Kita, S.; Nemoto, Y.; Tsuji, H.; Jitsukawa, S.

2002-12-01

Type 316L(N) stainless steel of the international thermonuclear experimental reactor grade (316L(N)-IG SS) is being considered for the first wall/blanket module. Hot isostatic pressing (HIP) technique is expected for the fabrication of the module. To evaluate the integrity and susceptibility to stress corrosion cracking (SCC) of HIPed 316L(N)-IG SS, tensile tests in vacuum and slow strain rate tests in high temperature water were performed. Specimen with the HIPed joint had similar tensile properties to specimens of 316L(N)-IG SS, and did not show susceptibility to SCC in oxygenated water at 423 K. Thermally sensitized specimen was low susceptible to SCC even in the creviced condition. It is concluded that the tensile properties of HIPed SS are as high as those of the base alloy and the HIP process caused no deleterious effects.

Effect of nickel and chromium on gingival tissues during orthodontic treatment: a longitudinal study.

PubMed

Ramadan, Ahmed Abdel-Fattah

2004-01-01

To determine the influence of chromium and nickel concentrations in saliva and their effects on gingival tissues during orthodontic treatment. Twenty orthodontic patients (10 males and 10 females), 17 to 20 years of age, were treated with fixed orthodontic appliances in the maxillary arch. Using atomic absorption spectrophotometer, the concentration of both metals was recorded during pretreatment, at 3 and 12 months into treatment, and 1 month after debonding. The depth of gingival crevice was recorded as well. After 3 months, 20% of females and 10% of males in this study showed allergic reaction in a form of gingivitis. This had disappeared by 1 month after appliance removal. While allergy to either nickel or chromium is not a serious medical problem, oral hygiene measures in at-risk patients should be optimal, with use of fluoride-free toothpaste and mouthrinse.

Epoxy resin

DOEpatents

Wilson, Glenn R.; Salyer, Ival O.; Ball, III, George L.

1976-07-13

By mixing one part of a prepolymer containing a polyamine partially polymerized with an organic epoxide and subsequently reacted with a fatty acid containing from 8 to 32 carbon atoms, and then reacting this prepolymer mixture with 3 parts of an organic epoxide, a composition was obtained which made a gas frothable, shear-stable, room temperature curing, low density foam. A particularly advantageous prepolymer was prepared using a polyamine selected from the group consisting of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine, partially polymerized with an organic epoxide having an average molecular weight of about 350 and having an epoxide equivalent of 185 to 192, and reacted with 2-10 weight percent linoleic acid. When one part of this prepolymer was reacted with about three parts of epoxy, and frothed by whipping in air or nitrogen an epoxy foam was produced which could be troweled onto surfaces and into corners or crevices, and subsequently cured, at near ambient temperature, to a strong dimensionally stable foam product.

Effect of Hydrogen Addition on Methane HCCI Engine Ignition Timing and Emissions Using a Multi-zone Model

NASA Astrophysics Data System (ADS)

Wang, Zi-han; Wang, Chun-mei; Tang, Hua-xin; Zuo, Cheng-ji; Xu, Hong-ming

2009-06-01

Ignition timing control is of great importance in homogeneous charge compression ignition engines. The effect of hydrogen addition on methane combustion was investigated using a CHEMKIN multi-zone model. Results show that hydrogen addition advances ignition timing and enhances peak pressure and temperature. A brief analysis of chemical kinetics of methane blending hydrogen is also performed in order to investigate the scope of its application, and the analysis suggests that OH radical plays an important role in the oxidation. Hydrogen addition increases NOx while decreasing HC and CO emissions. Exhaust gas recirculation (EGR) also advances ignition timing; however, its effects on emissions are generally the opposite. By adjusting the hydrogen addition and EGR rate, the ignition timing can be regulated with a low emission level. Investigation into zones suggests that NOx is mostly formed in core zones while HC and CO mostly originate in the crevice and the quench layer.

Localized corrosion of 316L stainless steel in tritiated water containing aggressive radiolytic and decomposition products at different temperatures

NASA Astrophysics Data System (ADS)

Bellanger, G.

2008-02-01

Tritium is one of the more important radionuclides used in nuclear industry as plutonium and uranium. The tritium in tritiated water always causes difficulties in nuclear installations, including equipment corrosion. Moreover, with tritiated water there are, in addition, the radiolytic and decomposition products such as hydrogen peroxide formed during decay, chloride ions produced by degradation of organic seals and oils used for tightness and pumping, and acid pH produced by excitation of nitrogen in air by the β - particle. Highly concentrated tritiated water releases energy and its temperature is about 80 °C, moreover heating is necessary in the tritium processes. These conditions highly facilitate the corrosion of stainless steels by pitting and crevice attack. Corrosion tests were performed by electrochemical analysis methods and by visual inspection of the surface of stainless steel.

Study of blood flow in several benchmark micro-channels using a two-fluid approach.

PubMed

Wu, Wei-Tao; Yang, Fang; Antaki, James F; Aubry, Nadine; Massoudi, Mehrdad

2015-10-01

It is known that in a vessel whose characteristic dimension (e.g., its diameter) is in the range of 20 to 500 microns, blood behaves as a non-Newtonian fluid, exhibiting complex phenomena, such as shear-thinning, stress relaxation, and also multi-component behaviors, such as the Fahraeus effect, plasma-skimming, etc. For describing these non-Newtonian and multi-component characteristics of blood, using the framework of mixture theory, a two-fluid model is applied, where the plasma is treated as a Newtonian fluid and the red blood cells (RBCs) are treated as shear-thinning fluid. A computational fluid dynamic (CFD) simulation incorporating the constitutive model was implemented using OpenFOAM® in which benchmark problems including a sudden expansion and various driven slots and crevices were studied numerically. The numerical results exhibited good agreement with the experimental observations with respect to both the velocity field and the volume fraction distribution of RBCs.

Great tits search for, capture, kill and eat hibernating bats

PubMed Central

Estók, Péter; Zsebők, Sándor; Siemers, Björn M.

2010-01-01

Ecological pressure paired with opportunism can lead to surprising innovations in animal behaviour. Here, we report predation of great tits (Parus major) on hibernating pipistrelle bats (Pipistrellus pipistrellus) at a Hungarian cave. Over two winters, we directly observed 18 predation events. The tits specifically and systematically searched for and killed bats for food. A substantial decrease in predation on bats after experimental provisioning of food to the tits further supports the hypothesis that bat-killing serves a foraging purpose in times of food scarcity. We finally conducted a playback experiment to test whether tits would eavesdrop on calls of awakening bats to find them in rock crevices. The tits could clearly hear the calls and were attracted to the loudspeaker. Records for tit predation on bats at this cave now span more than ten years and thus raise the question of whether cultural transmission plays a role for the spread of this foraging innovation. PMID:19740892

Effect of nitric acid treatment on activated carbon derived from oil palm shell

NASA Astrophysics Data System (ADS)

Allwar, Allwar; Hartati, Retno; Fatimah, Is

2017-03-01

The primary object of this work is to study the effect of nitric acid on the porous and morphology structure of activated carbon. Production of activated carbon from oil palm shell was prepared with pyrolysis process at temperature 900°C and by introduction of 10 M nitric acid. Determination of surface area, pore volume and pore size distribution of activated carbon was conducted by the N2 adsorption-desorption isotherm at 77 K. Morphology structure and elemental micro-analysis of activated carbon were estimated by Scanning Electron Microscopy (SEM) and energy dispersive X-ray (EDX), respectively. The result shows that activated carbon after treating with nitric acid proved an increasing porous characteristics involving surface area, pore volume and pore size distribution. It also could remove the contaminants including metals and exhibit an increasing of pores and crevices all over the surface.

Disinfection of bacteria attached to granular activated carbon.

PubMed Central

LeChevallier, M W; Hassenauer, T S; Camper, A K; McFeters, G A

1984-01-01

Heterotrophic plate count bacteria, coliform organisms, and pathogenic microorganisms attached to granular activated carbon particles were examined for their susceptibility to chlorine disinfection. When these bacteria were grown on carbon particles and then disinfected with 2.0 mg of chlorine per liter (1.4 to 1.6 mg of free chlorine residual per liter after 1 h) for 1 h, no significant decrease in viable counts was observed. Washed cells attached to the surface of granular activated carbon particles showed similar resistance to chlorine, but a progressive increase in sublethal injury was found. Observations made by scanning electron microscope indicated that granular activated carbon was colonized by bacteria which grow in cracks and crevices and are coated by an extracellular slime layer. These data suggest a possible mechanism by which treatment and disinfection barriers can be penetrated and pathogenic bacteria may enter drinking water supplies. Images PMID:6508306

Structural basis of lipid-driven conformational transitions in the KvAP voltage-sensing domain.

PubMed

Li, Qufei; Wanderling, Sherry; Sompornpisut, Pornthep; Perozo, Eduardo

2014-02-01

Voltage-gated ion channels respond to transmembrane electric fields through reorientations of the positively charged S4 helix within the voltage-sensing domain (VSD). Despite a wealth of structural and functional data, the details of this conformational change remain controversial. Recent electrophysiological evidence showed that equilibrium between the resting ('down') and activated ('up') conformations of the KvAP VSD from Aeropyrum pernix can be biased through reconstitution in lipids with or without phosphate groups. We investigated the structural transition between these functional states, using site-directed spin-labeling and EPR spectroscopic methods. Solvent accessibility and interhelical distance determinations suggest that KvAP gates through S4 movements involving an ∼3-Å upward tilt and simultaneous ∼2-Å axial shift. This motion leads to large accessibly changes in the intracellular water-filled crevice and supports a new model of gating that combines structural rearrangements and electric-field remodeling.

The Impact of Solid Surface Features on Fluid-Fluid Interface Configuration

NASA Astrophysics Data System (ADS)

Araujo, J. B.; Brusseau, M. L. L.

2017-12-01

Pore-scale fluid processes in geological media are critical for a broad range of applications such as radioactive waste disposal, carbon sequestration, soil moisture distribution, subsurface pollution, land stability, and oil and gas recovery. The continued improvement of high-resolution image acquisition and processing have provided a means to test the usefulness of theoretical models developed to simulate pore-scale fluid processes, through the direct quantification of interfaces. High-resolution synchrotron X-ray microtomography is used in combination with advanced visualization tools to characterize fluid distributions in natural geologic media. The studies revealed the presence of fluid-fluid interface associated with macroscopic features on the surfaces of the solids such as pits and crevices. These features and respective fluid interfaces, which are not included in current theoretical or computational models, may have a significant impact on accurate simulation and understanding of multi-phase flow, energy, heat and mass transfer processes.

A Model of Generating Visual Place Cells Based on Environment Perception and Similar Measure.

PubMed

Zhou, Yang; Wu, Dewei

2016-01-01

It is an important content to generate visual place cells (VPCs) in the field of bioinspired navigation. By analyzing the firing characteristic of biological place cells and the existing methods for generating VPCs, a model of generating visual place cells based on environment perception and similar measure is abstracted in this paper. VPCs' generation process is divided into three phases, including environment perception, similar measure, and recruiting of a new place cell. According to this process, a specific method for generating VPCs is presented. External reference landmarks are obtained based on local invariant characteristics of image and a similar measure function is designed based on Euclidean distance and Gaussian function. Simulation validates the proposed method is available. The firing characteristic of the generated VPCs is similar to that of biological place cells, and VPCs' firing fields can be adjusted flexibly by changing the adjustment factor of firing field (AFFF) and firing rate's threshold (FRT).

A Model of Generating Visual Place Cells Based on Environment Perception and Similar Measure

PubMed Central

2016-01-01

It is an important content to generate visual place cells (VPCs) in the field of bioinspired navigation. By analyzing the firing characteristic of biological place cells and the existing methods for generating VPCs, a model of generating visual place cells based on environment perception and similar measure is abstracted in this paper. VPCs' generation process is divided into three phases, including environment perception, similar measure, and recruiting of a new place cell. According to this process, a specific method for generating VPCs is presented. External reference landmarks are obtained based on local invariant characteristics of image and a similar measure function is designed based on Euclidean distance and Gaussian function. Simulation validates the proposed method is available. The firing characteristic of the generated VPCs is similar to that of biological place cells, and VPCs' firing fields can be adjusted flexibly by changing the adjustment factor of firing field (AFFF) and firing rate's threshold (FRT). PMID:27597859

RN work engagement in generational cohorts: the view from rural US hospitals.

PubMed

Sullivan Havens, Donna; Warshawsky, Nora E; Vasey, Joseph

2013-10-01

To describe staff nurse work engagement, identify predictors by generational cohort, present implications for nurse managers and suggest future research. A global nurse shortage looms. While an adequate supply of nurses is needed to ensure access to care, access to quality care may be enhanced by an adequate supply of highly engaged nurses-those who are dedicated, energized, and absorbed. Nurses have long reported the presence of energy depleting practice environments. Nurses practicing in professional practice environments may be more engaged. A non-experimental survey design was executed. Direct care Registered Nurses (n = 747) working in five rural acute care hospitals completed questionnaires to assess work engagement (Utrecht Work Engagement Scale-9), decisional involvement (Decisional Involvement Scale), relational coordination (Relational Coordination Survey) and the nursing practice environment (Practice Environment Scale of the Nursing Work Index). Descriptive, correlational and regression analyses examined work engagement and predictors by generational cohort. With the exception of the absorption component, no statistically significant differences in engagement emerged across generational cohorts. Predictors of engagement differed by cohort, however across all cohorts, professional nursing practice environments predicted nurse work engagement. Professional nursing practice environments are significantly associated with nurse work engagement. Enhancing nurse work engagement is a complex challenge. Generational cohorts may respond to different strategies to enhance engagement. © 2013 John Wiley & Sons Ltd.

Light environment change induces differential expression of guppy opsins in a multi-generational evolution experiment.

PubMed

Kranz, Alexandrea M; Forgan, Leonard G; Cole, Gemma L; Endler, John A

2018-06-19

Light environments critically impact species that rely on vision to survive and reproduce. Animal visual systems must accommodate changes in light that occur from minutes to years, yet the mechanistic basis of their response to spectral (color) changes is largely unknown. Here we used a laboratory experiment where replicate guppy populations were kept under three different light environments for up to 8-12 generations to explore possible differences in the expression levels of nine guppy opsin genes. Previous evidence for opsin expression-light environment 'tuning' has been either correlative or focused exclusively on the relationship between the light environment and opsin expression over one or two generations. In our multi-generation experiment, the relative expression levels of nine different guppy opsin genes responded differently to light environment changes: some did not respond, while others differed due to phenotypic plasticity. Moreover, for the LWS-1 opsin we found that, while we observed a wide range of plastic responses under different light conditions, common plastic responses (where the population replicates all followed the same trajectory) occurred only after multigenerational exposure to different light environments. Taken together this suggests that opsin expression plasticity plays an important role in light environment 'tuning' in different light environments on different time scales, and, in turn, has important implications for both visual system function and evolution. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

How the Environment Is Positioned in the "Next Generation Science Standards": A Critical Discourse Analysis

ERIC Educational Resources Information Center

Hufnagel, Elizabeth; Kelly, Gregory J.; Henderson, Joseph A.

2018-01-01

The purpose of this paper is to describe how the environment and environmental issues are conceptualized and positioned in the Next Generation Science Standards (NGSS) to examine underlying assumptions about the environment. The NGSS are a recent set of science standards in the USA, organized and led by Achieve Inc., that propose science education…

Evaluation of the Dornier Gmbh interactive grid generation system

NASA Technical Reports Server (NTRS)

Brown, Robert L.

1989-01-01

An interactive grid generation program, INGRID, is investigated and evaluated. A description of the task and work performed, a description and evaluation of INGRID, and a discussion of the possibilities for bringing INGRID into the NASA and Numerical Aerodynamic Simulator (NAS) computing environments is included. The interactive grid generation program was found to be a viable approach for grid generation and determined that it could be converted to work in the NAS environment but that INGRID does not solve the fundamentally hard problems associated with grid generation, specifically, domain decomposition.

Learn about Energy and its Impact on the Environment

EPA Pesticide Factsheets

Find answers to questions about clean energy, the impact of energy on the environment, and U.S. electricity generation. Clean energy includes renewable energy, energy efficiency and efficient combined heat and power. All forms of electricity generation hav

Computational Tools and Facilities for the Next-Generation Analysis and Design Environment

NASA Technical Reports Server (NTRS)

Noor, Ahmed K. (Compiler); Malone, John B. (Compiler)

1997-01-01

This document contains presentations from the joint UVA/NASA Workshop on Computational Tools and Facilities for the Next-Generation Analysis and Design Environment held at the Virginia Consortium of Engineering and Science Universities in Hampton, Virginia on September 17-18, 1996. The presentations focused on the computational tools and facilities for analysis and design of engineering systems, including, real-time simulations, immersive systems, collaborative engineering environment, Web-based tools and interactive media for technical training. Workshop attendees represented NASA, commercial software developers, the aerospace industry, government labs, and academia. The workshop objectives were to assess the level of maturity of a number of computational tools and facilities and their potential for application to the next-generation integrated design environment.

Tension zones of deep-seated rockslides revealed by thermal anomalies and airborne laser scan data

NASA Astrophysics Data System (ADS)

Baroň, Ivo; Bečkovský, David; Gajdošík, Juraj; Opálka, Filip; Plan, Lukas; Winkler, Gerhard

2015-04-01

Open cracks, tension fractures and crevice caves are important diagnostic features of gravitationally deformed slopes. When the cracks on the upper part of the slope open to the ground surface, they transfer relatively warm and buoyant air from the underground in cold seasons and thus could be detected by the infrared thermography (IRT) as warmer anomalies. Here we present two IRT surveys of deep-seated rockslides in Austria and the Czech Republic. We used thermal imaging cameras Flir and Optris, manipulated manually from the ground surface and also from unmanned aerial vehicle and piloted ultralight-plane platforms. The surveys were conducted during cold days of winter 2014/2015 and early in the morning to avoid the negative effect of direct sunshine. The first study site is the Bad Fischau rockslide in the southern part of the Vienna Basin (Austria). It was firstly identified by the morphostructural analysis of 1-m digital terrain model from the airborne laser scan data. The rockslide is superimposed on, and closely related to the active marginal faults of the Vienna basin, which is a pull apart structure. There is the 80-m-deep Eisenstein Show Cave situated in the southern lateral margin of the rockslide. The cave was originally considered to be purely of hydrothermal (hypogene) karstification; however its specific morphology and position within the detachment zone of the rockslide suggests its relation to gravitational slope-failure. The IRT survey revealed the Eisenstein Cave at the ground surface and also several other open cracks and possible cleft caves along the margins, headscarp, and also within the body of the rockslide. The second surveyed site was the Kněhyně rockslide in the flysch belt of the Outer Western Carpathians in the eastern Czech Republic. This deep-seated translational rockslide formed about eight known pseudokarst crevice caves, which reach up to 57 m in depth. The IRT survey recognized several warm anomalies indicating very deep deformation of the slope. When compared to digital terain model, some of these thermal anomalies suggest large unexplored crack systems deep in the rock-slope failure. As a conclusion we notice that especially when compared to topographic structures visualized on high accuracy digital terrain models, detecting the thermal anomalies could significantly contribute to understanding the subsurface occurrence of the tension fractures and voids within deep-seated rockslide bodies.

Crystal Structure of the Core Region of Hantavirus Nucleocapsid Protein Reveals the Mechanism for Ribonucleoprotein Complex Formation

PubMed Central

Guo, Yu; Wang, Wenming; Sun, Yuna; Ma, Chao; Wang, Xu; Wang, Xin; Liu, Pi; Shen, Shu; Li, Baobin; Lin, Jianping; Deng, Fei

2015-01-01

ABSTRACT Hantaviruses, which belong to the genus Hantavirus in the family Bunyaviridae, infect mammals, including humans, causing either hemorrhagic fever with renal syndrome (HFRS) or hantavirus cardiopulmonary syndrome (HCPS) in humans with high mortality. Hantavirus encodes a nucleocapsid protein (NP) to encapsidate the genome and form a ribonucleoprotein complex (RNP) together with viral polymerase. Here, we report the crystal structure of the core domains of NP (NPcore) encoded by Sin Nombre virus (SNV) and Andes virus (ANDV), which are two representative members that cause HCPS in the New World. The constructs of SNV and ANDV NPcore exclude the N- and C-terminal portions of full polypeptide to obtain stable proteins for crystallographic study. The structure features an N lobe and a C lobe to clamp RNA-binding crevice and exhibits two protruding extensions in both lobes. The positively charged residues located in the RNA-binding crevice play a key role in RNA binding and virus replication. We further demonstrated that the C-terminal helix and the linker region connecting the N-terminal coiled-coil domain and NPcore are essential for hantavirus NP oligomerization through contacts made with two adjacent protomers. Moreover, electron microscopy (EM) visualization of native RNPs extracted from the virions revealed that a monomer-sized NP-RNA complex is the building block of viral RNP. This work provides insight into the formation of hantavirus RNP and provides an understanding of the evolutionary connections that exist among bunyaviruses. IMPORTANCE Hantaviruses are distributed across a wide and increasing range of host reservoirs throughout the world. In particular, hantaviruses can be transmitted via aerosols of rodent excreta to humans or from human to human and cause HFRS and HCPS, with mortalities of 15% and 50%, respectively. Hantavirus is therefore listed as a category C pathogen. Hantavirus encodes an NP that plays essential roles both in RNP formation and in multiple biological functions. NP is also the exclusive target for the serological diagnoses. This work reveals the structure of hantavirus NP, furthering the knowledge of hantavirus RNP formation, revealing the relationship between hantavirus NP and serological specificity and raising the potential for the development of new diagnosis and therapeutics targeting hantavirus infection. PMID:26559827

Crystal Structure of the Core Region of Hantavirus Nucleocapsid Protein Reveals the Mechanism for Ribonucleoprotein Complex Formation.

PubMed

Guo, Yu; Wang, Wenming; Sun, Yuna; Ma, Chao; Wang, Xu; Wang, Xin; Liu, Pi; Shen, Shu; Li, Baobin; Lin, Jianping; Deng, Fei; Wang, Hualin; Lou, Zhiyong

2016-01-15

Hantaviruses, which belong to the genus Hantavirus in the family Bunyaviridae, infect mammals, including humans, causing either hemorrhagic fever with renal syndrome (HFRS) or hantavirus cardiopulmonary syndrome (HCPS) in humans with high mortality. Hantavirus encodes a nucleocapsid protein (NP) to encapsidate the genome and form a ribonucleoprotein complex (RNP) together with viral polymerase. Here, we report the crystal structure of the core domains of NP (NPcore) encoded by Sin Nombre virus (SNV) and Andes virus (ANDV), which are two representative members that cause HCPS in the New World. The constructs of SNV and ANDV NPcore exclude the N- and C-terminal portions of full polypeptide to obtain stable proteins for crystallographic study. The structure features an N lobe and a C lobe to clamp RNA-binding crevice and exhibits two protruding extensions in both lobes. The positively charged residues located in the RNA-binding crevice play a key role in RNA binding and virus replication. We further demonstrated that the C-terminal helix and the linker region connecting the N-terminal coiled-coil domain and NPcore are essential for hantavirus NP oligomerization through contacts made with two adjacent protomers. Moreover, electron microscopy (EM) visualization of native RNPs extracted from the virions revealed that a monomer-sized NP-RNA complex is the building block of viral RNP. This work provides insight into the formation of hantavirus RNP and provides an understanding of the evolutionary connections that exist among bunyaviruses. Hantaviruses are distributed across a wide and increasing range of host reservoirs throughout the world. In particular, hantaviruses can be transmitted via aerosols of rodent excreta to humans or from human to human and cause HFRS and HCPS, with mortalities of 15% and 50%, respectively. Hantavirus is therefore listed as a category C pathogen. Hantavirus encodes an NP that plays essential roles both in RNP formation and in multiple biological functions. NP is also the exclusive target for the serological diagnoses. This work reveals the structure of hantavirus NP, furthering the knowledge of hantavirus RNP formation, revealing the relationship between hantavirus NP and serological specificity and raising the potential for the development of new diagnosis and therapeutics targeting hantavirus infection. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Simulated microbe removal around finger rings using different hand sanitation methods.

PubMed

Alur, Archana A; Rane, Madhavi J; Scheetz, James P; Lorenz, Douglas J; Gettleman, Lawrence

2009-09-01

It is our opinion that the CDC and the WHO have underestimated cross-contamination under examination gloves in dental clinics while wearing jewelry, such as finger rings. These agencies only "recommend" removing jewelry, and only washing hands for 15 seconds with soap and warm water before donning gloves. This study examined several washing procedures and finger rings using simulated microbes. A gloved rubber hand manikin was made and fitted with a fresh disposable vinyl glove. Four fingers were fitted with rings or no ring, dusted with simulated microbes, and washed with a scrub brush for 5, 15, and 25 seconds under 20 degrees C and 40 degrees C water alone, or with liquid hand soap. Light levels (in lux) of fluorescent powder before and after washing were measured and delta scores calculated for changes in light levels, equivalent to effectiveness of hand washing procedures. A full-factorial, 3-factor analysis of variance (ANOVA) was used to test for differences among levels of the three study factors-time, temperature, and soap use. Tukey's post hoc honestly significant difference (HSD) test was applied to significant factors to examine pair-wise differences between factor levels. It was found that the longer the hands with rings were washed with a scrub brush under flowing water, the more simulated microbes were removed. By 25 seconds, all methods were essentially the same. Simulated microbes were more difficult to remove from the palm compared to the back of the hand. The liquid hand soap used in this study was more effective with warm water than cold. When given a choice of washing with cold water up to 15 seconds, it would be preferable not to use soap to remove simulated microbes. Qualitatively, the outer surface of finger rings were more effectively cleaned than the crevice below the ring, and the ring with a stone setting appeared to accumulate and retain simulated microbes more than other rings. The most effective treatment was washing with warm water and liquid soap. Longer times were more effective. Rings should not be worn under examination gloves due to difficulty cleaning in the crevice under the ring, and the well-known consequences of cross-contamination between the patient and the health care worker.

Chemical conversion of cisplatin and carboplatin with histidine in a model protein crystallized under sodium iodide conditions

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

Tanley, Simon W. M.; Helliwell, John R., E-mail: john.helliwell@manchester.ac.uk

Crystals of HEWL with cisplatin and HEWL with carboplatin grown in sodium iodide conditions both show a partial chemical transformation of cisplatin or carboplatin to a transiodoplatin (PtI{sub 2}X{sub 2}) form. The binding is only at the N{sup δ} atom of His15. A further Pt species (PtI{sub 3}X) is also seen, in both cases bound in a crevice between symmetry-related protein molecules. Cisplatin and carboplatin are platinum anticancer agents that are used to treat a variety of cancers. Previous X-ray crystallographic studies of carboplatin binding to histidine in hen egg-white lysozyme (HEWL) showed a partial chemical conversion of carboplatin tomore » cisplatin owing to the high sodium chloride concentration used in the crystallization conditions. Also, the co-crystallization of HEWL with carboplatin in sodium bromide conditions resulted in the partial conversion of carboplatin to the transbromoplatin form, with a portion of the cyclobutanedicarboxylate (CBDC) moiety still present. The results of the co-crystallization of HEWL with cisplatin or carboplatin in sodium iodide conditions are now reported in order to determine whether the cisplatin and carboplatin converted to the iodo form, and whether this took place in a similar way to the partial conversion of carboplatin to cisplatin in NaCl conditions or to transbromoplatin in NaBr conditions as seen previously. It is reported here that a partial chemical transformation has taken place to a transplatin form for both ligands. The NaI-grown crystals belonged to the monoclinic space group P2{sub 1} with two molecules in the asymmetric unit. The chemically transformed cisplatin and carboplatin bind to both His15 residues, i.e. in each asymmetric unit. The binding is only at the N{sup δ} atom of His15. A third platinum species is also seen in both conditions bound in a crevice between symmetry-related molecules. Here, the platinum is bound to three I atoms identified based on their anomalous difference electron densities and their refined occupancies, with the fourth bound atom being a Cl atom (in the cisplatin case) or a portion of the CBDC moiety (in the carboplatin case)« less

Corrosion of Continuous Fiber Reinforced Aluminum Metal Matrix Composites (CF-AMCs)

NASA Astrophysics Data System (ADS)

Tiwari, Shruti

The first objective of this research is to study the atmospheric corrosion behavior of continuous reinforced aluminum matrix composites (CF-AMCs). The materials used for this research were alumina (Al2O3) and nickel (Ni) coated carbon (C) fibers reinforced AMCs. The major focus is to identify the correlation between atmospheric parameters and the corrosion rates of CF-AMCs in the multitude of microclimates and environments in Hawai'i. The micro-structures of CF-AMCs were obtained to correlate the microstructures with their corrosion performances. Also electrochemical polarization experiments were conducted in the laboratory to explain the corrosion mechanism of CF-AMCs. In addition, CF-AMCs were exposed to seven different test sites for three exposure periods. The various climatic conditions like temperature (T), relative humidity (RH), rainfall (RF), time of wetness (TOW), chloride (Cl- ) and sulfate (SO42-) deposition rate, and pH were monitored for three exposure period. Likewise, mass losses of CF-AMCs at each test site for three exposure periods were determined. The microstructure of the CF-AMCS showed that Al/C/50f MMCs contained a Ni-rich phase in the matrix, indicating that the Ni coating on the C fiber dissolved in the matrix. The intermetallic phases obtained in Al-2wt% Cu/Al 2O3/50f-T6 MMC and Al-2wt%-T6 monolith were rich in Cu and Fe. The intermetallic phases obtained in Al 7075/Al2O3/50f-T6 MMC and Al 7075-T6 monolith also contained traces of Mg, Zn, Ni, and Si. Electrochemical polarization experiment indicated that the Al/Al 2O3/50f Al-2wt% Cu/Al2O3/50f-T6 and Al 7075/Al2O3/50f-T6 MMC showed similar corrosion trends as their respective monoliths pure Al, Al-2wt%-T6 and Al 7075-T6 in both aerated and deaerated condition. Al2O3 fiber, being an insulator, did not have a great effect on the polarization behavior of the composites. Al/C/50f MMCs corroded at a much faster rate as compared to pure Al monolith due to the galvanic effect between C and Al. According to the mass loss data of Al/C/50f MMCs, corrosion rate was high at marine environments (high Cl-) when compared to a tropical rainforest microclimate and low in a test site with a high SO2 and acid rain. Due to presence of conductive C fiber, the galvanic corrosion was a dominating corrosion mechanism. Due to high volume fraction of C, the corrosion phenomenon was cathodically controlled. The galvanic corrosion between C fiber and Al matrix showed a strong positive correlation with Cl - deposition rate. Lower corrosion rate at volcanic test site was attributed to dissolution of Ni rich phase, a potential cathodic site that promotes corrosion of Al/C/50f MMCs. Based on the mass loss data of Al2O3 based CF-AMCs and the monoliths showed maximum corrosion at volcanic test site when compared to any other test site. Due to the small volume fraction of intermetallic phases, the corrosion was anodically controlled. And hence the maximum anodic dissolution was found at volcanic test site (high SO2 and acid rain). The second objective of this thesis is to study the effect localized deformation on the corrosion of CF-AMCs. Corrosion initiation on Al (2 wt% Cu)/Al2O3/60f (60% fiber), Al 6061/Al2O 3/60f, and Al/Al2O3/60f CF-AMCs was studied in an aqueous environment The CF-AMCs and their monolithic alloys were deformed locally using a 1/16" diameter silicon nitride ball and 15-60 Kg load in a Rockwell hardness testing machine. Corrosion initiated at the deformed sites, and after longer exposures, spread over the entire region. Localized mechanical deformation resulted in micro-crevice formations at the fiber matrix interface. When deformed material is exposed to a corrosive solution, the crevices at the fiber matrix interface likely increased the hydrogen ion concentration lowering the pH at those regions, a process that leads to premature corrosion. The copper (Cu) rich CF-AMCs in aqueous solution resulted in dissolution of Cu rich phase and their subsequent deposition and redistribution as Cu over the deformed CF-AMCs surface. The corrosion rates of deformed CF-AMCs were higher than the non-deformed CF-AMCs.

Physical environment virtualization for human activities recognition

NASA Astrophysics Data System (ADS)

Poshtkar, Azin; Elangovan, Vinayak; Shirkhodaie, Amir; Chan, Alex; Hu, Shuowen

2015-05-01

Human activity recognition research relies heavily on extensive datasets to verify and validate performance of activity recognition algorithms. However, obtaining real datasets are expensive and highly time consuming. A physics-based virtual simulation can accelerate the development of context based human activity recognition algorithms and techniques by generating relevant training and testing videos simulating diverse operational scenarios. In this paper, we discuss in detail the requisite capabilities of a virtual environment to aid as a test bed for evaluating and enhancing activity recognition algorithms. To demonstrate the numerous advantages of virtual environment development, a newly developed virtual environment simulation modeling (VESM) environment is presented here to generate calibrated multisource imagery datasets suitable for development and testing of recognition algorithms for context-based human activities. The VESM environment serves as a versatile test bed to generate a vast amount of realistic data for training and testing of sensor processing algorithms. To demonstrate the effectiveness of VESM environment, we present various simulated scenarios and processed results to infer proper semantic annotations from the high fidelity imagery data for human-vehicle activity recognition under different operational contexts.

Knowledge environments representing molecular entities for the virtual physiological human.

PubMed

Hofmann-Apitius, Martin; Fluck, Juliane; Furlong, Laura; Fornes, Oriol; Kolárik, Corinna; Hanser, Susanne; Boeker, Martin; Schulz, Stefan; Sanz, Ferran; Klinger, Roman; Mevissen, Theo; Gattermayer, Tobias; Oliva, Baldo; Friedrich, Christoph M

2008-09-13

In essence, the virtual physiological human (VPH) is a multiscale representation of human physiology spanning from the molecular level via cellular processes and multicellular organization of tissues to complex organ function. The different scales of the VPH deal with different entities, relationships and processes, and in consequence the models used to describe and simulate biological functions vary significantly. Here, we describe methods and strategies to generate knowledge environments representing molecular entities that can be used for modelling the molecular scale of the VPH. Our strategy to generate knowledge environments representing molecular entities is based on the combination of information extraction from scientific text and the integration of information from biomolecular databases. We introduce @neuLink, a first prototype of an automatically generated, disease-specific knowledge environment combining biomolecular, chemical, genetic and medical information. Finally, we provide a perspective for the future implementation and use of knowledge environments representing molecular entities for the VPH.

Techniques for Unifying Disparate Elements in an EOS Instrument's Product Generation System Development Environment

NASA Technical Reports Server (NTRS)

Murray, Alex; Eng, Bjorn; Leff, Craig; Schwarz, Arnold

1997-01-01

In the development environment for ASTER level II product generation system, techniques have been incorporated to allow automated information sharing among all system elements, and to enable the use of sound software engineering techniques in the scripting languages.

Generation of large scale urban environments to support advanced sensor and seeker simulation

NASA Astrophysics Data System (ADS)

Giuliani, Joseph; Hershey, Daniel; McKeown, David, Jr.; Willis, Carla; Van, Tan

2009-05-01

One of the key aspects for the design of a next generation weapon system is the need to operate in cluttered and complex urban environments. Simulation systems rely on accurate representation of these environments and require automated software tools to construct the underlying 3D geometry and associated spectral and material properties that are then formatted for various objective seeker simulation systems. Under an Air Force Small Business Innovative Research (SBIR) contract, we have developed an automated process to generate 3D urban environments with user defined properties. These environments can be composed from a wide variety of source materials, including vector source data, pre-existing 3D models, and digital elevation models, and rapidly organized into a geo-specific visual simulation database. This intermediate representation can be easily inspected in the visible spectrum for content and organization and interactively queried for accuracy. Once the database contains the required contents, it can then be exported into specific synthetic scene generation runtime formats, preserving the relationship between geometry and material properties. To date an exporter for the Irma simulation system developed and maintained by AFRL/Eglin has been created and a second exporter to Real Time Composite Hardbody and Missile Plume (CHAMP) simulation system for real-time use is currently being developed. This process supports significantly more complex target environments than previous approaches to database generation. In this paper we describe the capabilities for content creation for advanced seeker processing algorithms simulation and sensor stimulation, including the overall database compilation process and sample databases produced and exported for the Irma runtime system. We also discuss the addition of object dynamics and viewer dynamics within the visual simulation into the Irma runtime environment.

Measurement Tools for the Immersive Visualization Environment: Steps Toward the Virtual Laboratory.

PubMed

Hagedorn, John G; Dunkers, Joy P; Satterfield, Steven G; Peskin, Adele P; Kelso, John T; Terrill, Judith E

2007-01-01

This paper describes a set of tools for performing measurements of objects in a virtual reality based immersive visualization environment. These tools enable the use of the immersive environment as an instrument for extracting quantitative information from data representations that hitherto had be used solely for qualitative examination. We provide, within the virtual environment, ways for the user to analyze and interact with the quantitative data generated. We describe results generated by these methods to obtain dimensional descriptors of tissue engineered medical products. We regard this toolbox as our first step in the implementation of a virtual measurement laboratory within an immersive visualization environment.

SRB ascent aerodynamic heating design criteria reduction study, volume 1

NASA Technical Reports Server (NTRS)

Crain, W. K.; Frost, C. L.; Engel, C. D.

1989-01-01

An independent set of solid rocket booster (SRB) convective ascent design environments were produced which would serve as a check on the Rockwell IVBC-3 environments used to design the ascent phase of flight. In addition, support was provided for lowering the design environments such that Thermal Protection System (TPS), based on conservative estimates, could be removed leading to a reduction in SRB refurbishment time and cost. Ascent convective heating rates and loads were generated at locations in the SRB where lowering the thermal environment would impact the TPS design. The ascent thermal environments are documented along with the wind tunnel/flight test data base used as well as the trajectory and environment generation methodology. Methodology, as well as, environment summaries compared to the 1980 Design and Rockwell IVBC-3 Design Environment are presented in this volume, 1.

Knowledge-based approach for generating target system specifications from a domain model

NASA Technical Reports Server (NTRS)

Gomaa, Hassan; Kerschberg, Larry; Sugumaran, Vijayan

1992-01-01

Several institutions in industry and academia are pursuing research efforts in domain modeling to address unresolved issues in software reuse. To demonstrate the concepts of domain modeling and software reuse, a prototype software engineering environment is being developed at George Mason University to support the creation of domain models and the generation of target system specifications. This prototype environment, which is application domain independent, consists of an integrated set of commercial off-the-shelf software tools and custom-developed software tools. This paper describes the knowledge-based tool that was developed as part of the environment to generate target system specifications from a domain model.

Remote sensing using MIMO systems

DOEpatents

Bikhazi, Nicolas; Young, William F; Nguyen, Hung D

2015-04-28

A technique for sensing a moving object within a physical environment using a MIMO communication link includes generating a channel matrix based upon channel state information of the MIMO communication link. The physical environment operates as a communication medium through which communication signals of the MIMO communication link propagate between a transmitter and a receiver. A spatial information variable is generated for the MIMO communication link based on the channel matrix. The spatial information variable includes spatial information about the moving object within the physical environment. A signature for the moving object is generated based on values of the spatial information variable accumulated over time. The moving object is identified based upon the signature.

Minimization and management of wastes from biomedical research.

PubMed Central

Rau, E H; Alaimo, R J; Ashbrook, P C; Austin, S M; Borenstein, N; Evans, M R; French, H M; Gilpin, R W; Hughes, J; Hummel, S J; Jacobsohn, A P; Lee, C Y; Merkle, S; Radzinski, T; Sloane, R; Wagner, K D; Weaner, L E

2000-01-01

Several committees were established by the National Association of Physicians for the Environment to investigate and report on various topics at the National Leadership Conference on Biomedical Research and the Environment held at the 1--2 November 1999 at the National Institutes of Health in Bethesda, Maryland. This is the report of the Committee on Minimization and Management of Wastes from Biomedical Research. Biomedical research facilities contribute a small fraction of the total amount of wastes generated in the United States, and the rate of generation appears to be decreasing. Significant reductions in generation of hazardous, radioactive, and mixed wastes have recently been reported, even at facilities with rapidly expanding research programs. Changes in the focus of research, improvements in laboratory techniques, and greater emphasis on waste minimization (volume and toxicity reduction) explain the declining trend in generation. The potential for uncontrolled releases of wastes from biomedical research facilities and adverse impacts on the general environment from these wastes appears to be low. Wastes are subject to numerous regulatory requirements and are contained and managed in a manner protective of the environment. Most biohazardous agents, chemicals, and radionuclides that find significant use in research are not likely to be persistent, bioaccumulative, or toxic if they are released. Today, the primary motivations for the ongoing efforts by facilities to improve minimization and management of wastes are regulatory compliance and avoidance of the high disposal costs and liabilities associated with generation of regulated wastes. The committee concluded that there was no evidence suggesting that the anticipated increases in biomedical research will significantly increase generation of hazardous wastes or have adverse impacts on the general environment. This conclusion assumes the positive, countervailing trends of enhanced pollution prevention efforts by facilities and reductions in waste generation resulting from improvements in research methods will continue. PMID:11121362

Idea Generating among Secondary School Teachers.

ERIC Educational Resources Information Center

Tomic, Welko; Brouwers, Andre

This study investigated where and how secondary school teachers generated ideas linked to their work environment. A group of 146 teachers from 20 secondary schools in the Netherlands completed an adapted version of Geschka's questionnaire, which focused on (1) teachers' preferred conditions, environments, media, people, and activities before the…

System and method of active vibration control for an electro-mechanically cooled device

DOEpatents

Lavietes, Anthony D.; Mauger, Joseph; Anderson, Eric H.

2000-01-01

A system and method of active vibration control of an electro-mechanically cooled device is disclosed. A cryogenic cooling system is located within an environment. The cooling system is characterized by a vibration transfer function, which requires vibration transfer function coefficients. A vibration controller generates the vibration transfer function coefficients in response to various triggering events. The environments may differ by mounting apparatus, by proximity to vibration generating devices, or by temperature. The triggering event may be powering on the cooling system, reaching an operating temperature, or a reset action. A counterbalance responds to a drive signal generated by the vibration controller, based on the vibration signal and the vibration transfer function, which adjusts vibrations. The method first places a cryogenic cooling system within a first environment and then generates a first set of vibration transfer function coefficients, for a vibration transfer function of the cooling system. Next, the cryogenic cooling system is placed within a second environment and a second set of vibration transfer function coefficients are generated. Then, a counterbalance is driven, based on the vibration transfer function, to reduce vibrations received by a vibration sensitive element.

Template Authoring Environment for the Automatic Generation of Narrative Content

ERIC Educational Resources Information Center

Caropreso, Maria Fernanda; Inkpen, Diana; Keshtkar, Fazel; Khan, Shahzad

2012-01-01

Natural Language Generation (NLG) systems can make data accessible in an easily digestible textual form; but using such systems requires sophisticated linguistic and sometimes even programming knowledge. We have designed and implemented an environment for creating and modifying NLG templates that requires no programming knowledge, and can operate…

40 CFR 262.41 - Biennial report.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 25 2010-07-01 2010-07-01 false Biennial report. 262.41 Section 262.41 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES (CONTINUED) STANDARDS APPLICABLE TO GENERATORS OF HAZARDOUS WASTE Recordkeeping and Reporting § 262.41 Biennial report. (a) A generator who ships any hazardous waste...

The Expression of Depressive Symptomatology in Korean American Undergraduates: Sex and Generational Differences

ERIC Educational Resources Information Center

Castellanos, Jeanett; Gloria, Alberta M.; Kim, Sara Cho; Park, Yong S.

2014-01-01

This study examined the influence of acculturation and perception of the university environment on the depressive symptomatology of 228 Korean American undergraduates, with a focus on sex and generational differences. Perceptions of the university environment and perceived barriers were positive predictors of depressive symptomatology in…

Learning Ecosystem Complexity: A Study on Small-Scale Fishers' Ecological Knowledge Generation

ERIC Educational Resources Information Center

Garavito-Bermúdez, Diana

2018-01-01

Small-scale fisheries are learning contexts of importance for generating, transferring and updating ecological knowledge of natural environments through everyday work practices. The rich knowledge fishers have of local ecosystems is the result of the intimate relationship fishing communities have had with their natural environments across…

Automated Tutoring in Interactive Environments: A Task-Centered Approach.

ERIC Educational Resources Information Center

Wolz, Ursula; And Others

1989-01-01

Discusses tutoring and consulting functions in interactive computer environments. Tutoring strategies are considered, the expert model and the user model are described, and GENIE (Generated Informative Explanations)--an answer generating system for the Berkeley Unix Mail system--is explained as an example of an automated consulting system. (33…

40 CFR 279.32 - Used oil aggregation points owned by the generator.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 28 2013-07-01 2013-07-01 false Used oil aggregation points owned by the generator. 279.32 Section 279.32 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES (CONTINUED) STANDARDS FOR THE MANAGEMENT OF USED OIL Standards for Used Oil...

40 CFR 279.32 - Used oil aggregation points owned by the generator.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 26 2010-07-01 2010-07-01 false Used oil aggregation points owned by the generator. 279.32 Section 279.32 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES (CONTINUED) STANDARDS FOR THE MANAGEMENT OF USED OIL Standards for Used Oil...

40 CFR 279.32 - Used oil aggregation points owned by the generator.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 27 2011-07-01 2011-07-01 false Used oil aggregation points owned by the generator. 279.32 Section 279.32 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES (CONTINUED) STANDARDS FOR THE MANAGEMENT OF USED OIL Standards for Used Oil...

40 CFR 279.32 - Used oil aggregation points owned by the generator.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 27 2014-07-01 2014-07-01 false Used oil aggregation points owned by the generator. 279.32 Section 279.32 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES (CONTINUED) STANDARDS FOR THE MANAGEMENT OF USED OIL Standards for Used Oil...

Intergenerational Efforts to Develop a Healthy Environment for Everyone: Sustainability as a Human Rights Issue.

PubMed

Kruger, Tina M; Savage, Caroline E; Newsham, Patrick

2014-12-01

As climate change proceeds at an unprecedented rate, concern for the natural environment has increased. The world's population aging also continues to rise at an unprecedented rate, giving greater attention to the implications of an older population. The two trends are linked through the fact that changes to the environment affect older adults, and older adults affect the environment. Sustainability is, therefore, an intergenerational phenomenon, and protecting resources today leaves a positive legacy and enhances quality of life for future generations. Older adults have much to share with younger generations about behaviors that promote sustainable living, yet few sustainability efforts are intergenerational in nature. As large numbers of people currently subsist without secure access to basic needs, ensuring equitable resource consumption for all generations is urgent and aligns with the Universal Declaration of Human Rights. Through exploring linkages between aging and sustainability, we identify intergenerational strategies to protect the environment and promote human rights and quality of life for older adults. © The Author(s) 2015.

Establishment of sustainable health science for future generations: from a hundred years ago to a hundred years in the future.

PubMed

Mori, Chisato; Todaka, Emiko

2009-01-01

Recently, we have investigated the relationship between environment and health from a scientific perspective and developed a new academic field, "Sustainable Health Science" that will contribute to creating a healthy environment for future generations. There are three key points in Sustainable Heath Science. The first key point is "focusing on future generations"-society should improve the environment and prevent possible adverse health effects on future generations (Environmental Preventive Medicine). The second key point is the "precautious principle". The third key point is "transdisciplinary science", which means that not only medical science but also other scientific fields, such as architectural and engineering science, should be involved. Here, we introduce our recent challenging project "Chemiless Town Project", in which a model town is under construction with fewer chemicals. In the project, a trial of an education program and a health-examination system of chemical exposure is going to be conducted. In the future, we are aiming to establish health examination of exposure to chemicals of women of reproductive age so that the risk of adverse health effects to future generations will decrease and they can enjoy a better quality of life. We hope that society will accept the importance of forming a sustainable society for future generations not only with regard to chemicals but also to the whole surrounding environment. As the proverb of American native people tells us, we should live considering the effects on seven generations in the future.

Fast, Automated, Scalable Generation of Textured 3D Models of Indoor Environments

DTIC Science & Technology

2014-12-18

expensive travel and on-site visits. Different applications require models of different complexities, both with and without furniture geometry. The...environment and to localize the system in the environment over time. The datasets shown in this paper were generated by a backpack -mounted system that uses 2D...voxel is found to intersect the line segment from a scanner to a corresponding scan point. If a laser passes through a voxel, that voxel is considered

Integrated Design Engineering Analysis (IDEA) Environment Automated Generation of Structured CFD Grids using Topology Methods

NASA Technical Reports Server (NTRS)

Kamhawi, Hilmi N.

2012-01-01

This report documents the work performed from March 2010 to March 2012. The Integrated Design and Engineering Analysis (IDEA) environment is a collaborative environment based on an object-oriented, multidisciplinary, distributed framework using the Adaptive Modeling Language (AML) as a framework and supporting the configuration design and parametric CFD grid generation. This report will focus on describing the work in the area of parametric CFD grid generation using novel concepts for defining the interaction between the mesh topology and the geometry in such a way as to separate the mesh topology from the geometric topology while maintaining the link between the mesh topology and the actual geometry.

A Curriculum Activities Guide to Electric Power Generation and the Environment.

ERIC Educational Resources Information Center

Tully, Randolph R., Jr., Ed.

This guide was developed by teachers involved in a workshop on "Electric Power Generation and the Environment." Activity topics are: (1) Energy and the Consumer; (2) Energy and Water Pollution; and (3) Energy and Air Pollution. Within these topics, the activities are classified as awareness level, transitional level, or operational…

452nd Brookhaven Lecture. Extreme Environments of Next-Generation Energy Systems and Materials: Can They Peacefully Co-Exist?

ScienceCinema

Simos, Nikolaos

2017-12-22

Nikolaos Simos of Brookhaven’s Energy Sciences and Technology Department and the National Synchrotron Light Source II Project presents, “Extreme Environments of Next-Generation Energy Systems and Materials: Can They Peacefully Co-Exist?”

Generation of Werner states and preservation of entanglement in a noisy environment [rapid communication

NASA Astrophysics Data System (ADS)

Jakóbczyk, Lech; Jamróz, Anna

2005-12-01

We study the influence of noisy environment on the evolution of two-atomic system in the presence of collective damping. Generation of Werner states as asymptotic stationary states of evolution is described. We also show that for some initial states the amount of entanglement is preserved during the evolution.

Effects of solar photovoltaic technology on the environment in China.

PubMed

Qi, Liqiang; Zhang, Yajuan

2017-10-01

Among the various types of renewable energy, solar photovoltaic has elicited the most attention because of its low pollution, abundant reserve, and endless supply. Solar photovoltaic technology generates both positive and negative effects on the environment. The environmental loss of 0.00666 yuan/kWh from solar photovoltaic technology is lower than that from coal-fired power generation (0.05216 yuan/kWh). The negative effects of solar photovoltaic system production include wastewater and waste gas pollutions, the representatives of which contain fluorine, chromium with wastewater and hydrogen fluoride, and silicon tetrachloride gas. Solar panels are also a source of light pollution. Improper disposal of solar cells that have reached the end of their service life harms the environment through the stench they produce and the damage they cause to the soil. So, the positive and negative effects of green energy photovoltaic power generation technology on the environment should be considered.

Experimental evidence needed to demonstrate inter- and trans-generational effects of ancestral experiences in mammals.

PubMed

Dias, Brian G; Ressler, Kerry J

2014-10-01

Environmental factors routinely influence an organism's biology. The inheritance or transmission of such influences to descendant generations would be an efficient mode of information transfer across generations. The developmental stage at which a specific environment is encountered by the ancestral generation, and the number of generations over which information about that environment is registered, determines an inter- vs. trans-generational effect of ancestral influence. This commentary will outline the distinction between these influences. While seductive in principle, inter- and trans-generational inheritance in mammals is a hotly debated area of research inquiry. We present constructive criticism of such inheritance, and suggest potential experimental avenues for reconciliation. Finally, epigenetic mechanisms present an avenue for gene regulation that is dynamic. We briefly discuss how such malleability affords the potential for a reversal of any detrimental environmental influences that might have adversely impacted ancestral or descendant generations. © 2014 WILEY Periodicals, Inc.

Computational modelling of the mechanics of trabecular bone and marrow using fluid structure interaction techniques.

PubMed

Birmingham, E; Grogan, J A; Niebur, G L; McNamara, L M; McHugh, P E

2013-04-01

Bone marrow found within the porous structure of trabecular bone provides a specialized environment for numerous cell types, including mesenchymal stem cells (MSCs). Studies have sought to characterize the mechanical environment imposed on MSCs, however, a particular challenge is that marrow displays the characteristics of a fluid, while surrounded by bone that is subject to deformation, and previous experimental and computational studies have been unable to fully capture the resulting complex mechanical environment. The objective of this study was to develop a fluid structure interaction (FSI) model of trabecular bone and marrow to predict the mechanical environment of MSCs in vivo and to examine how this environment changes during osteoporosis. An idealized repeating unit was used to compare FSI techniques to a computational fluid dynamics only approach. These techniques were used to determine the effect of lower bone mass and different marrow viscosities, representative of osteoporosis, on the shear stress generated within bone marrow. Results report that shear stresses generated within bone marrow under physiological loading conditions are within the range known to stimulate a mechanobiological response in MSCs in vitro. Additionally, lower bone mass leads to an increase in the shear stress generated within the marrow, while a decrease in bone marrow viscosity reduces this generated shear stress.

Interactive effects of genotype x environment on the live weight of GIFT Nile tilapias.

PubMed

Oliveira, Sheila N DE; Ribeiro, Ricardo P; Oliveira, Carlos A L DE; Alexandre, Luiz; Oliveira, Aline M S; Lopera-Barrero, Nelson M; Santander, Victor F A; Santana, Renan A C

2017-01-01

In this paper, the existence of a genotype x environment interaction for the average daily weight in GIFT Nile tilapia (Oreochromis niloticus) in different regions in the state of Paraná (Brazil) was analyzed. The heritability results were high in the uni-characteristic analysis: 0.71, 0.72 and 0.67 for the cities of Palotina (PL), Floriano (FL) and Diamond North (DN), respectively. Genetic correlations estimated in bivariate analyzes were weak with values between 0.12 for PL-FL, 0.06 for PL and 0.23 for DN-FL-DN. The Spearman correlation values were low, which indicated a change in ranking in the selection of animals in different environments in the study. There was heterogeneity in the phenotypic variance among the three regions and heterogeneity in the residual variance between PL and DN. The direct genetic gain was greater for the region with a DN value gain of 198.24 g/generation, followed by FL (98.73 g/generation) and finally PL (98.73 g/generation). The indirect genetic gains were lower than 0.37 and greater than 0.02 g/generation. The evidence of the genotype x environment interaction was verified, which indicated the phenotypic heterogeneity of the variances among the three regions, weak genetic correlation and modified rankings in the different environments.

Separating parental environment from seed size effects on next generation growth and development in Arabidopsis.

PubMed

Elwell, Angela L; Gronwall, David S; Miller, Nathan D; Spalding, Edgar P; Brooks, Tessa L Durham

2011-02-01

Plant growth and development is profoundly influenced by environmental conditions that laboratory experimentation typically attempts to control. However, growth conditions are not uniform between or even within laboratories and the extent to which these differences influence plant growth and development is unknown. Experiments with wild-type Arabidopsis thaliana were designed to quantify the influences of parental environment and seed size on growth and development in the next generation. A single lot of seed was planted in six environmental chambers and grown to maturity. The seed produced was mechanically sieved into small and large size classes then grown in a common environment and subjected to a set of assays spanning the life cycle. Analysis of variance demonstrated that seed size effects were particularly significant early in development, affecting primary root growth and gravitropism, but also flowering time. Parental environment affected progeny germination time, flowering and weight of seed the progeny produced. In some cases, the parental environment affected the magnitude of (interacted with) the observed seed size effects. These data indicate that life history circumstances of the parental generation can affect growth and development throughout the life cycle of the next generation to an extent that should be considered when performing genetic studies. © 2010 Blackwell Publishing Ltd.

Protection of ultrastructure in chilling-stressed banana leaves by salicylic acid*

PubMed Central

Kang, Guo-zhang; Wang, Zheng-xun; Xia, Kuai-fei; Sun, Gu-chou

2007-01-01

Objective: Chilling tolerance of salicylic acid (SA) in banana seedlings (Musa acuminata cv., Williams 8818) was investigated by changes in ultrastructure in this study. Methods: Light and electron microscope observation. Results: Pretreatment with 0.5 mmol/L SA under normal growth conditions (30/22 °C) by foliar spray and root irrigation resulted in many changes in ultrastructure of banana cells, such as cells separation from palisade parenchymas, the appearance of crevices in cell walls, the swelling of grana and stromal thylakoids, and a reduction in the number of starch granules. These results implied that SA treatment at 30/22 °C could be a type of stress. During 3 d of exposure to 7 °C chilling stress under low light, however, cell ultrastructure of SA-pretreated banana seedlings showed less deterioration than those of control seedlings (distilled water-pretreated). Conclusion: SA could provide some protection for cell structure of chilling-stressed banana seedling. PMID:17444604

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

Tolbert, Allison K.; Young, Jenna M.; Jung, Seokwon

Caldicellulosiruptor bescii is a thermophilic, anaerobic bacterium that is capable of utilizing unpretreated biomass in addition to breaking down cellulose and hemicellulose into simple sugars. Despite the fact that C. bescii must first bind to the surface of the biomass, there has been no analysis of the morphological or chemical changes to the biomass surface as a result of incubation with the micro-organism. To understand more about C. bescii growth, juvenile poplar stems were sectioned (80 μm thick) and incubated with C. bescii beyond the typical 24 h experiment length. Monitoring the cell counts during incubation revealed a biphasic growthmore » pattern. The impact the micro-organism had on the surface was determined by scanning electron microscopy (SEM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS), which showed physical crevices in the cell wall caused by the C. bescii along with a decrease of polysaccharide ions and an increase in lignin ions on the poplar surface. Employing infrared microspectroscopy, the decreasing trend was corroborated.« less

Development of an Accelerated Test Method for the Determination of Susceptibility to Atmospheric Corrosion

NASA Technical Reports Server (NTRS)

Ambrose, John R.

1991-01-01

The theoretical rationale is presented for use of a repetitive cyclic current reversal voltammetric technique for characterization of localized corrosion processes, including atmospheric corrosion. Applicability of this proposed experimental protocol is applied to characterization of susceptibility to crevice and pitting corrosion, atmospheric corrosion and stress corrosion cracking. Criteria upon which relative susceptibility is based were determined and tested using two iron based alloys commonly in use at NASA-Kennedy; A36 (a low carbon steel) and 4130 (a low alloy steel). Practicality of the procedure was demonstrated by measuring changes in anodic polarization behavior during high frequency current reversal cycles of 25 cycles per second with 1 mA/sq cm current density amplitude in solutions containing Cl anions. The results demonstrated that, due to excessive polarization which affects conductivity of barrier corrosion product layers, A36 was less resistant to atmospheric corrosion than its 4130 counterpart; behavior which was also demonstrated during exposure tests.

Spatial variability in community composition on a granite breakwater versus natural rocky shores: lack of microhabitats suppresses intertidal biodiversity.

PubMed

Aguilera, Moisés A; Broitman, Bernardo R; Thiel, Martin

2014-10-15

Strong differences have been observed between the assemblages on artificial reefs and on natural hard-bottom habitats worldwide, but little is known about the mechanisms that cause contrasting biodiversity patterns. We examined the influence of spatial attributes in relation to both biogenic and topographic microhabitats, in the distribution and composition of intertidal species on both artificial and natural reefs. We found higher small-scale spatial heterogeneity on the natural reef compared with the study breakwater. Species richness and diversity were associated with a higher availability of crevices, rock pools and mussels in natural habitats. Spatial distribution of certain grazers corresponded well with the spatial structure of microhabitats. In contrast, the lack of microhabitats on the breakwater resulted in the absence of several grazers reflected in lower species richness. Biogenic and topographic microhabitats can have interactive effects providing niche opportunities for multiple species, explaining differences in species diversity between artificial versus natural reefs. Copyright © 2014 Elsevier Ltd. All rights reserved.

The dynamic organization of fungal acetyl-CoA carboxylase

NASA Astrophysics Data System (ADS)

Hunkeler, Moritz; Stuttfeld, Edward; Hagmann, Anna; Imseng, Stefan; Maier, Timm

2016-04-01

Acetyl-CoA carboxylases (ACCs) catalyse the committed step in fatty-acid biosynthesis: the ATP-dependent carboxylation of acetyl-CoA to malonyl-CoA. They are important regulatory hubs for metabolic control and relevant drug targets for the treatment of the metabolic syndrome and cancer. Eukaryotic ACCs are single-chain multienzymes characterized by a large, non-catalytic central domain (CD), whose role in ACC regulation remains poorly characterized. Here we report the crystal structure of the yeast ACC CD, revealing a unique four-domain organization. A regulatory loop, which is phosphorylated at the key functional phosphorylation site of fungal ACC, wedges into a crevice between two domains of CD. Combining the yeast CD structure with intermediate and low-resolution data of larger fragments up to intact ACCs provides a comprehensive characterization of the dynamic fungal ACC architecture. In contrast to related carboxylases, large-scale conformational changes are required for substrate turnover, and are mediated by the CD under phosphorylation control.

Frequent water drinking by Zanzibar red colobus (Procolobus kirkii) in a mangrove forest refuge.

PubMed

Nowak, Katarzyna

2008-11-01

Isolated populations of Procolobus kirkii on Uzi Island, Zanzibar, use Rhizophora mucronata-dominated mangrove forest for refuge. Three groups, observed over 14 months, spent up to 85% of total observation time in mangroves with brief excursions to adjacent upland coral rag forest, habitat degraded by human cutting. A large proportion of monkeys' diets consisted of plant parts of five mangrove species. Water drinking was common and 326 water-drinking events were recorded at a rate of up to 0.87 drinks hr(-1). Groups used different strategies to obtain water including licking dew, drinking from treeholes, licking rain off leaves and tree trunks, and drinking from coral rock crevices with Cercopithecus mitis albogularis. Drinking frequency increased with time spent in and consumption of mangroves. Strategies for obtaining water were group-specific and likely the result of learning. Drinking appeared to be an acquired behavior in movement-restricted groups living in a habitat with low plant species diversity and limited salty foods. Copyright 2008 Wiley-Liss, Inc.

Study of blood flow in several benchmark micro-channels using a two-fluid approach

PubMed Central

Wu, Wei-Tao; Yang, Fang; Antaki, James F.; Aubry, Nadine; Massoudi, Mehrdad

2015-01-01

It is known that in a vessel whose characteristic dimension (e.g., its diameter) is in the range of 20 to 500 microns, blood behaves as a non-Newtonian fluid, exhibiting complex phenomena, such as shear-thinning, stress relaxation, and also multi-component behaviors, such as the Fahraeus effect, plasma-skimming, etc. For describing these non-Newtonian and multi-component characteristics of blood, using the framework of mixture theory, a two-fluid model is applied, where the plasma is treated as a Newtonian fluid and the red blood cells (RBCs) are treated as shear-thinning fluid. A computational fluid dynamic (CFD) simulation incorporating the constitutive model was implemented using OpenFOAM® in which benchmark problems including a sudden expansion and various driven slots and crevices were studied numerically. The numerical results exhibited good agreement with the experimental observations with respect to both the velocity field and the volume fraction distribution of RBCs. PMID:26240438

A Moist Crevice for Word Aversion: In Semantics Not Sounds

PubMed Central

Thibodeau, Paul H.

2016-01-01

Why do people self-report an aversion to words like “moist”? The present studies represent an initial scientific exploration into the phenomenon of word aversion by investigating its prevalence and cause. Results of five experiments indicate that about 10–20% of the population is averse to the word “moist.” This population often speculates that phonological properties of the word are the cause of their displeasure. However, data from the current studies point to semantic features of the word–namely, associations with disgusting bodily functions–as a more prominent source of peoples’ unpleasant experience. “Moist,” for averse participants, was notable for its valence and personal use, rather than imagery or arousal–a finding that was confirmed by an experiment designed to induce an aversion to the word. Analyses of individual difference measures suggest that word aversion is more prevalent among younger, more educated, and more neurotic people, and is more commonly reported by females than males. PMID:27119522

Small-Molecule-Based Self-Assembled Ligands for G-Quadruplex DNA Surface Recognition.

PubMed

Rivera-Sánchez, María Del C; García-Arriaga, Marilyn; Hobley, Gerard; Morales-de-Echegaray, Ana V; Rivera, José M

2017-10-31

Most drugs are small molecules because of their attractive pharmacokinetics, manageable development and manufacturing, and effective binding into the concave crevices of bio-macromolecules. Despite these features, they often fall short when it comes to effectively recognizing the surfaces of bio-macromolecules. One way to overcome the challenge of biomolecular surface recognition is to develop small molecules that become self-assembled ligands (SALs) prior to binding. Herein, we report SALs made from 8-aryl-2'-deoxyguanosine derivatives forming precise hydrophilic supramolecular G-quadruplexes (SGQs) with excellent size, shape, and charge complementarity to G-quadruplex DNA (QDNA). We show that only those compounds forming SGQs act as SALs, which in turn differentially stabilize QDNAs from selected oncogene promoters and the human telomeric regions. Fluorescence resonance energy-transfer melting assays are consistent with spectroscopic, calorimetric, and light scattering studies, showing the formation of a "sandwichlike" complex QDNA·SGQ·QDNA. These results open the door for the advent of SALs that recognize QDNAs and potentially the surfaces of other bio-macromolecules such as proteins.

Evolutionary morphology of the hemolymph vascular system of basal araneomorph spiders (Araneae: Araneomorphae).

PubMed

Huckstorf, Katarina; Michalik, Peter; Ramírez, Martín; Wirkner, Christian S

2015-11-01

The superfamily Austrochiloidea (Austrochilidae and Gradungulidae) take a pivotal position in araneomorph spider phylogeny. In this discussion crevice weaver spiders (Filistatidae) are of equal interest. Especially data from these phylogenetically uncertain yet basal off branching groups can enlighten our understanding on the evolution of organ systems. In the course of a survey on the evolutionary morphology of the circulatory system in spiders we therefore investigated the hemolymph vascular system in two austrochiloid and one filistatid species. Additionally some data on a hypochilid and a gradungulid species are included. Using up-to-date morphological methods, the vascular systems in these spiders are visualized three dimensionally. Ground pattern features of the circulatory systems in austrochiloid spiders are presented and the data discussed along recent lines of phylogenetic hypotheses. Special topics highlighted are the intraspecific variability of the origins of some prosomal arteries and the evolutionary correlation of respiratory and circulatory systems in spiders. Copyright © 2015 Elsevier Ltd. All rights reserved.

Rural housing for control of Chagas disease in Venezuela.

PubMed

Briceno-Leon, R

1987-12-01

The home is an important protective element for the health of its inhabitants - but these inhabitants often include not only the householders but also domestic pests and vectors of disease. This is particularly so in Latin America where domestic triatomine bugs thrive in many of the poorer quality rural houses, emerging from their crevices at night to feed and transmit Trypanosoma cruzi in their faeces. At the public health level, there is neither drug nor vaccine suitable for controlling T. cruzi - causative agent of Chagas disease - but transmission can be interrupted by control of the domestic vectors. Traditionally, vector control has involved spraying houses with residual insecticides, but a more long-term solution, with many colateral benefits, is to improve rural housing in such a way that colonization by triatomine bugs is inhibited. Such an approach involves development of low-cost techniques for house construction, and mobilization of rural communities to make use of them. In this, Venezuela has played a leading role, as Roberto Briceno-Leon reports.

ZM-21 magnesium alloy corrosion properties and cryogenic to elevated temperature mechanical properties

NASA Technical Reports Server (NTRS)

Montana, J. W.; Nelson, E. E.

1972-01-01

The mechanical properties of bare ZM-21 magnesium alloy flat tensile specimens were determined for test temperatures of +400 F, +300 F, +200 F, +80 F, 0 F, -100 F, -200 F, and -320 F. The ultimate tensile and yield strengths of the material increased with decreasing temperature with a corresponding reduction in elongation values. Stress corrosion tests performed under: (1) MSFC atmospheric conditions; (2) 95% relative humidity; and (3) submerged in 100 ppm chloride solution for 8 weeks indicated that the alloy is not susceptible to stress corrosion. The corrosion tests indicated that the material is susceptible to attack by crevice corrosion in high humidity and chemical type attack by chloride solution. Atmospheric conditions at MSFC did not produce any adverse effects on the material, probably due to the rapid formation of a protective oxide coating. In both the mechanical properties and the stress corrosion evaluations the test specimens which were cut transverse to the rolling direction had superior properties when compared to the longitudinal properties.

Emergency treatment of esophageal varix incarceration in the endoscope and ligation device during endoscopic variceal rubber band ligation

PubMed Central

Zhao, Hong; Cheng, Jilin; Xu, Yahong; Lu, Cuili; Huang, Shaoping; Fan, Zhenyu; Shi, Yuxin

2014-01-01

Sclerotherapy and endoscopic esophageal variceal ligation (EVL) are commonly used to treat and prevent variceal bleeding. As of today, there has been no report on an unexpected incarceration of a varix hooked on with the bands from the endoscopic EVL device. We recently experienced this emergency while using the 7-band ring endoscopic EVL device (Boston Scientific Corp., Boston, MA) for prophylaxis of variceal bleeding. In this case, the varix body itself was accidently incarcerated in the crevice of the esophageal endoscope after highly negative pressure of absorption was applied on the endoscope. In this situation, using force to take out the gastroscope was not an option as it would tear the vein and cause massive hemorrhage. We were managed to ligate the varix with rubber bands while releasing the incarceration. We observed that ligation of the varix at the same position using all seven ligation bands resulted in disappearance of the targeted varix. The surrounding esophageal mucosa became smooth after the treatment. PMID:25550983

Nowhere to run: the role of habitat openness and refuge use in defining patterns of morphological and performance evolution in tropical lizards.

PubMed

Goodman, Brett A

2009-07-01

For species from open habitats with little cover and few refugia, selection should favour morphologies that enhance performance at tasks that enable rapid movement across open areas. Similarly, selection should also favour traits that enable rapid access and movement within suitable refugia. This study examined the relationship between habitat openness, refuge use, morphology and performance of 19 species representing 23 populations of tropical Lygosomine skink. Species from this group occupy a wide array of habitats from open forest and open rocky intertidal zones to high-altitude heaths and dense, closed forests. Species that occupied open habitats were faster at sprinting, climbing and had better cling ability than species from more cluttered, closed habitats. In addition, species from habitats that used rock crevices as refuges had enhanced sprinting ability. This study shows the importance of both habitat openness and refuge type in the evolution of both the morphology and performance in lizards.

Development of Ren Qiou fractured carbonate oil pools by water injection

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

Yu, Z.; Li, G.

1982-01-01

This work gives a brief description on the geologic characteristics of Ren Qiou oil field and its development. Different methods have been used in its reservoir engineering study such as outcrop investigation, fracture and crevice description in tunnels, observation on core samples and their statistical data, thin section observation, casting section, fluorescence section, scanning electron microscope, mercury injection and withdrawal, down-hole television, and geophysical well logging. Physical modeling, 3-dimensional numeric simulation and reservoir performance analysis, and production profiles by production logging in an open hole, have been used to study mechanics of displacing oil by water and the movement ofmore » oil and water in reservoir pools production technologies with double-porosity. Pressure maintenance by bottomwater injection to keep producing wells flowing, acidization with emulsifying acid to penetrate deeply into the reservoir formation, and water plugging with chemical agent, have been used to maintain a consistent annual recovery rate. 11 references.« less

Corrosion of Ti6Al4V pins produced by direct metal laser sintering

NASA Astrophysics Data System (ADS)

de Damborenea, J. J.; Arenas, M. A.; Larosa, Maria Aparecida; Jardini, André Luiz; de Carvalho Zavaglia, Cecília Amélia; Conde, A.

2017-01-01

Direct Metal Laser Sintering (DMLS) technique allows the manufacturing a wide variety of medical devices for any type of prosthetic surgery (HIP, dental, cranial, maxillofacial) as well as for internal fixation devices (K-Wires or Steinmann Pins). There are a large number of research studies on DMLS, including microstructural characterization, mechanical properties and those based on production quality assurance but the influence of porosity in the corrosion behavior of these materials not been sufficiently considered. In the present paper, surgical pins of Ti6Al4V have been produced by DMLS. After testing in a phosphate buffered saline solution, the surface of the titanium alloy appeared locally covered by a voluminous white oxide. This unexpected behavior was presumably due to the existence of internal defects in the pins as result of the manufacturing process. The importance of these defects-that might act as crevice nucleation sites- has been revealed by electrochemical techniques and confirmed by computed tomography.

A combined cryo-EM and molecular dynamics approach reveals the mechanism of ErmBL-mediated translation arrest

NASA Astrophysics Data System (ADS)

Arenz, Stefan; Bock, Lars V.; Graf, Michael; Innis, C. Axel; Beckmann, Roland; Grubmüller, Helmut; Vaiana, Andrea C.; Wilson, Daniel N.

2016-07-01

Nascent polypeptides can induce ribosome stalling, regulating downstream genes. Stalling of ErmBL peptide translation in the presence of the macrolide antibiotic erythromycin leads to resistance in Streptococcus sanguis. To reveal this stalling mechanism we obtained 3.6-Å-resolution cryo-EM structures of ErmBL-stalled ribosomes with erythromycin. The nascent peptide adopts an unusual conformation with the C-terminal Asp10 side chain in a previously unseen rotated position. Together with molecular dynamics simulations, the structures indicate that peptide-bond formation is inhibited by displacement of the peptidyl-tRNA A76 ribose from its canonical position, and by non-productive interactions of the A-tRNA Lys11 side chain with the A-site crevice. These two effects combine to perturb peptide-bond formation by increasing the distance between the attacking Lys11 amine and the Asp10 carbonyl carbon. The interplay between drug, peptide and ribosome uncovered here also provides insight into the fundamental mechanism of peptide-bond formation.

Surgical implantation of intra-abdominal radiotransmitters in marine otters (Lontra felina) in central Chile.

PubMed

Soto-Azat, Claudio; Boher, Francisca; Fabry, Mauricio; Pascual, Paulo; Medina-Vogel, Gonzalo

2008-10-01

Six free-ranging marine otters (Lontra felina) were livetrapped on the central coast of Chile and implanted with specially designed radiotransmitters as part of a spatial ecology study. Marine otters frequent the rocky seashore, often squeezing their narrow bodies through cracks and crevices and grooming themselves on the rocks. They are also among the smallest of the otter species, weighing between 3.4 kg and 4.5 kg. For these reasons, the transmitter used was small, rectangular, and flat, measuring 3.5 x 3.2 x 1.0 cm. They were implanted using a ventral midline approach to minimize contact between the skin incision and sharp-edged rocks. Surgical incisions healed within 2 wk. The transmitters functioned well, but the duration varied from 62 days to 143 days instead of the 240 days predicted by the manufacturer. All six marine otters reestablished in their home ranges, and survey results suggest they survived well beyond the life of the transmitters.

The structure of neuronal calcium sensor-1 in solution revealed by molecular dynamics simulations.

PubMed

Bellucci, Luca; Corni, Stefano; Di Felice, Rosa; Paci, Emanuele

2013-01-01

Neuronal calcium sensor-1 (NCS-1) is a protein able to trigger signal transduction processes by binding a large number of substrates and re-shaping its structure depending on the environmental conditions. The X-ray crystal structure of the unmyristoilated NCS-1 shows a large solvent-exposed hydrophobic crevice (HC); this HC is partially occupied by the C-terminal tail and thus elusive to the surrounding solvent. We studied the native state of NCS-1 by performing room temperature molecular dynamics (MD) simulations starting from the crystal and the solution structures. We observe relaxation to a state independent of the initial structure, in which the C-terminal tail occupies the HC. We suggest that the C-terminal tail shields the HC binding pocket and modulates the affinity of NCS-1 for its natural targets. By analyzing the topology and nature of the inter-residue potential energy, we provide a compelling description of the interaction network that determines the three-dimensional organization of NCS-1.

Route Generation for a Synthetic Character (BOT) Using a Partial or Incomplete Knowledge Route Generation Algorithm in UT2004 Virtual Environment

NASA Technical Reports Server (NTRS)

Hanold, Gregg T.; Hanold, David T.

2010-01-01

This paper presents a new Route Generation Algorithm that accurately and realistically represents human route planning and navigation for Military Operations in Urban Terrain (MOUT). The accuracy of this algorithm in representing human behavior is measured using the Unreal Tournament(Trademark) 2004 (UT2004) Game Engine to provide the simulation environment in which the differences between the routes taken by the human player and those of a Synthetic Agent (BOT) executing the A-star algorithm and the new Route Generation Algorithm can be compared. The new Route Generation Algorithm computes the BOT route based on partial or incomplete knowledge received from the UT2004 game engine during game play. To allow BOT navigation to occur continuously throughout the game play with incomplete knowledge of the terrain, a spatial network model of the UT2004 MOUT terrain is captured and stored in an Oracle 11 9 Spatial Data Object (SOO). The SOO allows a partial data query to be executed to generate continuous route updates based on the terrain knowledge, and stored dynamic BOT, Player and environmental parameters returned by the query. The partial data query permits the dynamic adjustment of the planned routes by the Route Generation Algorithm based on the current state of the environment during a simulation. The dynamic nature of this algorithm more accurately allows the BOT to mimic the routes taken by the human executing under the same conditions thereby improving the realism of the BOT in a MOUT simulation environment.

Interactive Environment Design in Smart City

NASA Astrophysics Data System (ADS)

Deng, DeXiang; Chen, LanSha; Zhou, Xi

2017-08-01

The interactive environment design of smart city is not just an interactive progress or interactive mode design, rather than generate an environment such as the “organic” life entity as human beings through interactive design, forming a smart environment with perception, memory, thinking, and reaction.

The role of competition and seed production environment on the success of two perennial grass species in a roadside restoration

USDA-ARS?s Scientific Manuscript database

When large-scale restorations are undertaken using local genotypes, wild-collected sources often undergo a generation in an agronomic environment for seed increase. We have little information on how a single generation of agronomic production can alter seed success in restoration. In this study, we...

Effects of Self-Regulatory Status and Practice Type on Student Performance in the Mobile Learning Environment

ERIC Educational Resources Information Center

Tutty, Jeremy Ian

2013-01-01

The next generation of computer-based learning environments has arrived. This generation of technology is characterized by mobile and portable devices such as smartphones and tablet computers with wireless broadband access. With these devices comes the promise of extending the online learning revolution. The purpose of this study was to…

The Effects of Environment and Dwell on High Temperature Fatigue Crack Growth of 2 1/4 Cr - 1 Mo Steel.

DTIC Science & Technology

1983-06-01

frequency with a vacuum environment. In work concerning nuclear steam generator design ; Brinkman, et al. [Ref. 13], investigated time dependent...Nuclear Steam Generator Design ," Journal of Nuclear Materials, Vol. 62, pp. 181-204, 1976. 14. K. D. Challenger, A. K. Miller, C. R. Brinkman, "An

Automatic Sound Generation for Spherical Objects Hitting Straight Beams Based on Physical Models.

ERIC Educational Resources Information Center

Rauterberg, M.; And Others

Sounds are the result of one or several interactions between one or several objects at a certain place and in a certain environment; the attributes of every interaction influence the generated sound. The following factors influence users in human/computer interaction: the organization of the learning environment, the content of the learning tasks,…

60-Hz electric and magnetic fields generated by a distribution network.

PubMed

Héroux, P

1987-01-01

From a mobile unit, 60-Hz electric and magnetic fields generated by Hydro-Québec's distribution network were measured. Nine runs, representative of various human environments, were investigated. Typical values were 32 V/m and 0.16 microT. The electrical distribution networks investigated were major contributors to the electric and magnetic environments.

Structure and corrosion properties of PVD Cr-N coatings

NASA Astrophysics Data System (ADS)

Liu, C.; Bi, Q.; Ziegele, H.; Leyland, A.; Matthews, A.

2002-05-01

PVD Cr-N coatings produced by physical vapor deposition (PVD) are increasingly used for mechanical and tribological applications in various industrial sectors. These coatings are particularly attractive for their excellent corrosion resistance, which further enhances the lifetime and service quality of coated components. PVD Cr-N coated steels in an aqueous solution are usually corroded by galvanic attack via through-coating ``permeable'' defects (e.g., pores). Therefore, the corrosion performance of Cr-N coated steel is determined by a number of variables of the coating properties and corrosive environment. These variables include: (i) surface continuity and uniformity; (ii) through-coating porosity; (iii) film density and chemical stability; (iv) growth stresses; (v) interfacial and intermediate layers; (vi) coating thickness; (vii) coating composition; and (viii) substrate properties. In this article, PVD Cr-N coatings were prepared, by electron-beam PVD and sputter deposition, with different compositions, thicknesses, and surface roughnesses, by changing the N2 flow rate, applying multilayering techniques and changing the substrate finish prior to coating. The microstructure of such coatings is investigated by various analytical techniques such as glancing angle x-ray diffraction and scanning electron microscopy, which are also correlated with the corrosion performance of the coated steel. Both dc polarization and ac impedance spectroscopy were employed to investigate the corrosion resistance of Cr-N coated steel in a 0.5N NaCl solution. It has been found that the N2 flow rate during reactive deposition strongly determines the microstructure of Cr-N coatings (due to the changing nitrogen content in the film) and can thus affect the corrosion resistance of coated systems. The surface finish of the steel substrate also affects the uniformity and coverage of PVD coatings; grooves and inclusions on the original substrate can raise the susceptibility of coated systems to crevice corrosion. Increased coating thickness can also greatly reduce the incidence of through-coating porosity such that the improvement in corrosion performance of thicker Cr-N coatings is significant.

Characterization of Overwintering Sites of the Invasive Brown Marmorated Stink Bug in Natural Landscapes Using Human Surveyors and Detector Canines

PubMed Central

Lee, Doo-Hyung; Cullum, John P.; Anderson, Jennifer L.; Daugherty, Jodi L.; Beckett, Lisa M.; Leskey, Tracy C.

2014-01-01

Halyomorpha halys is an invasive species from Asia causing major economic losses in agricultural production in the mid-Atlantic region of the United States. Unlike other crop pests, H. halys is also well-known for nuisance problems in urban, suburban, and rural areas, as massive numbers of adults often invade human-made structures to overwinter inside protected environments. Research efforts have focused on populations in human-made structures while overwintering ecology of H. halys in natural landscapes is virtually unknown. We explored forested landscapes in the mid-Atlantic region to locate and characterize natural overwintering structures used by H. halys. We also evaluated the use of detector canines to locate overwintering H. halys to enhance the accuracy and efficiency of surveys. From these studies, we indentified shared characteristics of overwintering sites used by H. halys in natural landscapes. Overwintering H. halys were recovered from dry crevices in dead, standing trees with thick bark, particularly oak (Quercus spp.) and locust (Robinia spp.); these characteristics were shared by 11.8% of all dead trees in surveyed landscapes. For trees with favorable characteristics, we sampled ∼20% of the total above-ground tree area and recovered 5.9 adults per tree from the trees with H. halys present. Two detector canines were successfully trained to recognize and detect the odor of adult H. halys yielding >84% accuracy in laboratory and semi-field trials. Detector canines also found overwintering H. halys under field conditions. In particular, overwintering H. halys were recovered only from dead trees that yielded positive indications from the canines and shared key tree characteristics established by human surveyors. The identified characteristics of natural overwintering sites of H. halys will serve as baseline information to establish crop economic risk levels posed by overwintering populations, and accordingly develop sustainable management programs. PMID:24717734

Contamination Effects Due to Space Environmental Interactions

NASA Technical Reports Server (NTRS)

Chen, Philip T.; Paquin, Krista C. (Technical Monitor)

2001-01-01

Molecular and particulate contaminants are commonly generated from the orbital spacecraft operations that are under the influence of the space environment. Once generated, these contaminants may attach to the surfaces of the spacecraft or may remain in the vicinity of the spacecraft. In the event these contaminants come to rest on the surfaces of the spacecraft or situated in the line-of-sight of the observation path, they will create various degrees of contamination effect which may cause undesirable effects for normal spacecraft operations, There will be circumstances in which the spacecraft may be subjected to special space environment due to operational conditions. Interactions between contaminants and special space environment may alter or greatly increase the contamination effect due to the synergistic effect. This paper will address the various types of contamination generation on orbit, the general effects of the contamination on spacecraft systems, and the typical impacts on the spacecraft operations due to the contamination effect. In addition, this paper will explain the contamination effect induced by the space environment and will discuss the intensified contamination effect resulting from the synergistic effect with the special space environment.

40 CFR 271.10 - Requirements for generators of hazardous wastes.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 26 2010-07-01 2010-07-01 false Requirements for generators of... for Final Authorization § 271.10 Requirements for generators of hazardous wastes. (a) The State program must cover all generators covered by 40 CFR part 262. States must require new generators to...

Promoting Plasma Physics as a Career: A Generational Approach

NASA Astrophysics Data System (ADS)

Morgan, James

2005-10-01

A paradigm shift is occurring in education physics programs. Educators are shifting from the traditional teaching focus to concentrate on student learning. Students are unaware of physics as a career, plasma physics or the job opportunities afforded to them with a physics degree. The physics profession needs to promote itself to the younger generations, or specifically the millennial generation (Born in the 1980's-2000's). Learning styles preferred by ``Millennials'' include a technological environment that promotes learning through active task performance rather than passive attendance at lectures. Millennials respond well to anything experiential and will be motivated by opportunities for creativity and challenging learning environments. The open-ended access to information, the ability to tailor learning paths, and continuous and instantaneous performance assessment offer flexibility in the design of curricula as well as in the method of delivery. Educators need to understand the millennial generation, appeal to their motivations and offer a learning environment designed for their learning style. This poster suggests promoting a physics career by focusing on generational learning styles and preferences.

The Role of Gravity on the Reproduction of Arabidopsis Plants

NASA Technical Reports Server (NTRS)

Hoshizaki, T.

1985-01-01

The presence of gravity as a necessary environmental factor for higher plants to complete their life cycle was examined. Arabidopsis thalliana (L.) Heynh. Columbia strain plants were grown continuously for three generations in a simulated micro-g environment as induced by horizontal clinostats. Growth, development and reproduction were followed. The Arabidopsis plants were selected for three generations on clinostats because: (1) a short life cycle of around 35 days; (2) the cells of third generation plants would in theory be free of gravity imprint; and (3) a third generation plant would therefore more than likely grow and respond like a plant growing in a micro-g environment. It is found that gravity is not a required environmental factor for higher plants to complete their life cycle, at least as tested by a horizontal clinostat. Clinostatting does not prevent the completion of the plant life cycle. However, clinostatting does appear to slow down the reproductive process of Arabidopsis plants. Whether higher plants can continue to reproduce for many generations in a true micro-g environment of space can only be determined by long duration experiments in space.

Populations, productivity, and feeding habits of seabirds on St. Lawrence Island, Alaska: Final report

USGS Publications Warehouse

Piatt, John F.; Hatch, Scott A.; Roberts, Bay D.; Lidster, Wayne W.; Wells, John L.; Haney, J. Christopher

1988-01-01

A field camp was established at Kongkok Bay near the southwest cape of St. Lawrence Island and occupied continuously from 24 May to 2 September 1987. Permanent study plots were selected for both cliff and crevice-nesting species, and regular observations were made throughout the breeding season to document attendance patterns, breeding phenology, and success. Periodic collections of adults offshore and of chick meals in the colonies were used to determine the food habits of study species. Additional plots for population monitoring of murres and kittiwakes were established in colonies near Savoonga on the north side of the island, and counts were made there between 23 July and 1 August. Shore based work was supplemented with offshore studies of seabird foraging distribution from the USFWS vessel TIGLAX between 18 August and 3 September 1987.Populations of all study species in the Kongkok Bay area increased since the last study of seabirds there (murres 20, kittiwakes 87, Least Auklets 8, Crested Auklets 442). Pelagic Cormorants, Common Murres, and Thick-billed Murres exhibited average, or above average, breeding success at Kongkok in 1987. Black-legged Kittiwakes exhibited near-total reproductive failure. Crested and Least Auklets had high levels of breeding success after the effects of observer disturbance were taken into account. Predation by microtine rodents and foxes was a significant source of chick mortality on auklets.Feeding concentrations were found primarily north of Gambell in the Anadyr Strait or western Chirikof Basin. Kittiwakes were dispersed widely over the study area. Diets of all species studied were normal and, with the exception of kittiwakes, there was no evidence of problems in obtaining food.Current methods for assessing population changes in cliff-nesting species are considered adequate, but better techniques are needed for crevice-nesting auklets. Time-lapse photography offers the greatest potential for monitoring auklet numbers. A protocol is suggested for monitoring populations of murres, kittiwakes, and auklets at colonies in the Bering and Chukchi Seas. It calls for annual visits to selected colonies during two stages of the nesting cycle to assess numbers and breeding productivity.The breeding failure of Black-legged Kittiwakes on St. Lawrence Island in 1987 was part of a pervasive syndrome of failure in this species observed throughout the Bering Sea and Gulf of Alaska in recent years. The causes of recurrent, widespread breeding failure need to be identified if kittiwakes are to have a role in area-wide population monitoring during the period of Alaskan development by the oil and gas industry.

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

Marin, E.; Lekka, M., E-mail: maria.lekka@uniud.it; Andreatta, F.

In this paper, two different ASTM C 618 Class C fly ashes (FA) were used for the production of aluminum metal matrix composites (MMCs) using powder metallurgy (PM) technology. Calcareous FAs were sampled from the electrostatic precipitators of two different lignite-fired power stations: from Megalopolis, Southern Greece (MFA) and from Kardia, Northen Greece (KFA), under maximum electricity load. FAs were milled in order to reduce the mean particle diameter and Aluminum-FA composites containing 10% and 20% of FA were then prepared and compacted. The green products were sintered for 2 h at 600 Degree-Sign C. Sintered Al-FA MMCs showed increasedmore » hardness and wear resistance suggesting their possible use in industrial applications for example in covers, casings, brake rotors or engine blocks. As most possible industrial applications of MMCs not only require wear resistance, but also corrosion resistance in different mild aggressive medias, this paper aims to study the electrochemical behavior of FA MMCs in order to evaluate their corrosion resistance. The morphology and chemical composition of the phases in the Aluminum-FA composite samples were investigated using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDXS). Moreover, topographic and Volta potential maps were acquired by Scanning Kelvin Probe Force Microscopy (SKP-FM). Volta potential maps provide information about the electrochemical behavior of the different phases in absence of electrolyte. The electrochemical behavior was investigated by Open Circuit Potential measurements and potentiodynamic polarization, while the corrosion mechanisms were studied by SEM observations after different times of immersion in a mild corrosive medium. In all cases it could be stated that the addition of the FA particles into the Al matrix might cause an increase of the hardness and mechanical properties of the pure aluminum but deteriorates the corrosion resistance. The degradation phenomena occurring on the FA containing samples might be related to the following mechanisms: 1) Partial detachment or dissolution of the FA soluble phases, in particular based on Si, Fe and Ca; 2) dissolution of the Al matrix surrounding the FA particles due to crevice corrosion; 3) Al localized dissolution due to galvanic coupling between the Fe-rich intermetallics and the matrix. - Highlights: Black-Right-Pointing-Pointer Aluminum metal matrix composites containing two types of fly ashes have been characterized. Black-Right-Pointing-Pointer The microstructure and the electrochemical behavior have been studied using different techniques. Black-Right-Pointing-Pointer The addition of FA deteriorates the corrosion resistance of the aluminum. Black-Right-Pointing-Pointer Degradation mechanisms: galvanic coupling, crevice corrosion, detachment of FA particles.« less

Common approach to solving SGEMP, DEMP, and ESD survivability

NASA Technical Reports Server (NTRS)

Ling, D.

1977-01-01

System Generated Electromagnetic Pulse (SGEMP) and Dispersed Electromagnetic Pulse DEMP) are nuclear generated spacecraft environments. Electrostatic discharge (ESD) is a natural spacecraft environment resulting from differential charging in magnetic substorms. All three phenomena, though differing in origin, result in the same problem to the spacecraft and that is Electromagnetic Interference (EMI). A common design approach utilizing a spacecraft structural Faraday Cage is presented which helps solve the EMI problem. Also, other system design techniques are discussed which minimize the magnitude of these environments through control of materials and electrical grounding configuration.

Characterizing Microbe-Environment Interactions Through Experimental Evolution: The Autonomous Adaptive Directed Evolution Chamber

NASA Astrophysics Data System (ADS)

Ibanez, C. R.; Blaich, J.; Owyang, S.; Storrs, A.; Moffet, A.; Wong, N.; Zhou, J.; Gentry, D.

2015-12-01

We are developing a laboratory system for studying micro- to meso-scale interactions between microorganisms and their physicochemical environments. The Autonomous Adaptive Directed Evolution Chamber (AADEC) cultures microorganisms in controlled,small-scale geochemical environments. It observes corresponding microbial interactions to these environments and has the ability to adjust thermal, chemical, and other parameters in real time in response to these interactions. In addition to the sensed data, the system allows the generation of time-resolved ecological, genomic, etc. samples on the order of microbial generations. The AADEC currently houses cultures in liquid media and controls UVC radiation, heat exposure, and nutrient supply. In a proof-of-concept experimental evolution application, it can increase UVC radiation resistance of Escherichia coli cultures by iteratively exposing them to UVC and allowing the surviving cells to regrow. A baseline characterization generated a million fold resistance increase. This demonstration uses a single-well growth chamber prototype, but it was limited by scalability. We have expanded upon this system by implementing a microwell plate compatible fluidics system and sensor housing. This microwell plate system increases the diversity of microbial interactions seen in response to the geochemical environments generated by the system, allowing greater control over individual cultures' environments and detection of rarer events. The custom microfluidic card matches the footprint of a standard microwell plate. This card enables controllable fluid flow between wells and introduces multiple separate exposure and sensor chambers, increasing the variety of sensors compatible with the system. This gives the device control over scale and the interconnectedness of environments within the system. The increased controllability of the multiwell system provides a platform for implementing machine learning algorithms that will autonomously adjust geochemical environmental parameters.

Mission Critical Computer Resources Management Guide

DTIC Science & Technology

1988-09-01

Support Analyzers, Management, Generators Environments Word Workbench Processors Showroom System Structure HO Compilers IMath 1OperatingI Functions I...Simulated Automated, On-Line Generators Support Exercises Catalog, Function Environments Formal Spec Libraries Showroom System Structure I ADA Trackers I...shown in Figure 13-2. In this model, showrooms of larger more capable piecesare developed off-line for later integration and use in multiple systems

Voyager electronic parts radiation program, volume 1

NASA Technical Reports Server (NTRS)

Stanley, A. G.; Martin, K. E.; Price, W. E.

1977-01-01

The Voyager spacecraft is subject to radiation from external natural space, from radioisotope thermoelectric generators and heater units, and from the internal environment where penetrating electrons generate surface ionization effects in semiconductor devices. Methods for radiation hardening and tests for radiation sensitivity are described. Results of characterization testing and sample screening of over 200 semiconductor devices in a radiation environment are summarized.

A Typology of Agency in New Generation Learning Environments: Emerging Relational, Ecological and New Material Considerations

ERIC Educational Resources Information Center

Charteris, Jennifer; Smardon, Dianne

2018-01-01

The impetus to move to a new generation learning environments places a spotlight on the relational dynamics of classroom spaces. A key feature is the notion of learner agency. A complex notion, learner agency involves both compliance with and resistance to classroom norms and therefore is far more sophisticated than acting in acquiescence to…

Embryonic environment and transgenerational effects in quail.

PubMed

Leroux, Sophie; Gourichon, David; Leterrier, Christine; Labrune, Yann; Coustham, Vincent; Rivière, Sandrine; Zerjal, Tatiana; Coville, Jean-Luc; Morisson, Mireille; Minvielle, Francis; Pitel, Frédérique

2017-01-26

Environmental exposures, for instance to chemicals, are known to impact plant and animal phenotypes on the long term, sometimes across several generations. Such transgenerational phenotypes were shown to be promoted by epigenetic alterations such as DNA methylation, an epigenetic mark involved in the regulation of gene expression. However, it is yet unknown whether transgenerational epigenetic inheritance of altered phenotypes exists in birds. The purpose of this study was to develop an avian model to investigate whether changes to the embryonic environment had a transgenerational effect that could alter the phenotypes of third-generation offspring. Given its impact on the mammalian epigenome and the reproductive system in birds, genistein was used as an environment stressor. We compared several third-generation phenotypes of two quail "epilines", which were obtained from genistein-injected eggs (Epi+) or from untreated eggs (Epi-) from the same founders. A "mirrored" crossing strategy was used to minimize between-line genetic variability by maintaining similar ancestor contributions across generations in each line. Three generations after genistein treatment, a significant difference in the sexual maturity of the females, which, after three generations, could not be attributed to direct maternal effects, was observed between the lines, with Epi+ females starting to lay eggs later. Adult body weight was significantly affected by genistein treatment applied in a previous generation, and a significant interaction between line and sex was observed for body weight at 3 weeks. Behavioral traits, such as evaluating the birds' reaction to social isolation, were also significantly affected by genistein treatment. Yet, global methylation analyses revealed no significant difference between the epilines. These findings demonstrate that embryonic environment affects the phenotype of offspring three generations later in quail. While one cannot rule out the existence of some initial genetic variability between the lines, the mirrored animal design should have minimized its effects, and thus, the observed differences in animals of the third generation may be attributed, at least partly, to transgenerational epigenetic phenomena.

Self-evaluation on Motion Adaptation for Service Robots

NASA Astrophysics Data System (ADS)

Funabora, Yuki; Yano, Yoshikazu; Doki, Shinji; Okuma, Shigeru

We suggest self motion evaluation method to adapt to environmental changes for service robots. Several motions such as walking, dancing, demonstration and so on are described with time series patterns. These motions are optimized with the architecture of the robot and under certain surrounding environment. Under unknown operating environment, robots cannot accomplish their tasks. We propose autonomous motion generation techniques based on heuristic search with histories of internal sensor values. New motion patterns are explored under unknown operating environment based on self-evaluation. Robot has some prepared motions which realize the tasks under the designed environment. Internal sensor values observed under the designed environment with prepared motions show the interaction results with the environment. Self-evaluation is composed of difference of internal sensor values between designed environment and unknown operating environment. Proposed method modifies the motions to synchronize the interaction results on both environment. New motion patterns are generated to maximize self-evaluation function without external information, such as run length, global position of robot, human observation and so on. Experimental results show that the possibility to adapt autonomously patterned motions to environmental changes.

Application of advanced computing techniques to the analysis and display of space science measurements

NASA Technical Reports Server (NTRS)

Klumpar, D. M.; Lapolla, M. V.; Horblit, B.

1995-01-01

A prototype system has been developed to aid the experimental space scientist in the display and analysis of spaceborne data acquired from direct measurement sensors in orbit. We explored the implementation of a rule-based environment for semi-automatic generation of visualizations that assist the domain scientist in exploring one's data. The goal has been to enable rapid generation of visualizations which enhance the scientist's ability to thoroughly mine his data. Transferring the task of visualization generation from the human programmer to the computer produced a rapid prototyping environment for visualizations. The visualization and analysis environment has been tested against a set of data obtained from the Hot Plasma Composition Experiment on the AMPTE/CCE satellite creating new visualizations which provided new insight into the data.

Transgenerational developmental programming.

PubMed

Aiken, Catherine E; Ozanne, Susan E

2014-01-01

The concept of developmental programming suggests that the early life environment influences offspring characteristics in later life, including the propensity to develop diseases such as the metabolic syndrome. There is now growing evidence that the effects of developmental programming may also manifest in further generations without further suboptimal exposure. This review considers the evidence, primarily from rodent models, for effects persisting to subsequent generations, and evaluates the mechanisms by which developmental programming may be transmitted to further generations. In particular, we focus on the potential role of the intrauterine environment in contributing to a developmentally programmed phenotype in subsequent generations. The literature was systematically searched at http://pubmed.org and http://scholar.google.com to identify published findings regarding transgenerational (F2 and beyond) developmental programming effects in human populations and animal models. Transmission of programming effects is often viewed as a form of epigenetic inheritance, either via the maternal or paternal line. Evidence exists for both germline and somatic inheritance of epigenetic modifications which may be responsible for phenotypic changes in further generations. However, there is increasing evidence for the role of both extra-genomic components of the zygote and the interaction of the developing conceptus with the intrauterine environment in propagating programming effects. The contribution of a suboptimal reproductive tract environment or maternal adaptations to pregnancy may be critical to inheritance of programming effects via the maternal line. As the effects of age exacerbate the programmed metabolic phenotype, advancing maternal age may increase the likelihood of developmental programming effects being transmitted to further generations. We suggest that developmental programming effects could be propagated through the maternal line de novo in generations beyond F2 as a consequence of development in a suboptimally developed intrauterine tract and not necessarily though directly transmitted epigenetic mechanisms.

Improved control strategy for PI-R current of DFIG considering voltage and current harmonics compensation

NASA Astrophysics Data System (ADS)

Song, S. Y.; Liu, Q. H.; Zhao, Y. N.; Liu, S. Y.

2016-08-01

With the rapid development of wind power generation, the related research of wind power control and integration issues has attracted much attention, and the focus of the research are shifting away from the ideal power grid environment to the actual power grid environment. As the main stream wind turbine generator, a doubly-fed induction generator (DFIG) is connected to the power grid directly by its stator, so it is particularly sensitive to the power grid. This paper studies the improvement of DFIG control technology in the power grid harmonic environment. Based on the DFIG dynamic model considering the power grid harmonic environment, this paper introduces the shortcomings of the common control strategy of DFIG, and puts forward the enhanced method. The decoupling control of the system is realized by compensating the coupling between the rotor harmonic voltage and harmonic current, improving the control performance. In addition, the simulation experiments on PSCAD/EMTDC are carried out to verify the correctness and effectiveness of the improved scheme.

Neuronal Calcium Sensor-1 Binds the D2 Dopamine Receptor and G-protein-coupled Receptor Kinase 1 (GRK1) Peptides Using Different Modes of Interactions.

PubMed

Pandalaneni, Sravan; Karuppiah, Vijaykumar; Saleem, Muhammad; Haynes, Lee P; Burgoyne, Robert D; Mayans, Olga; Derrick, Jeremy P; Lian, Lu-Yun

2015-07-24

Neuronal calcium sensor-1 (NCS-1) is the primordial member of the neuronal calcium sensor family of EF-hand Ca(2+)-binding proteins. It interacts with both the G-protein-coupled receptor (GPCR) dopamine D2 receptor (D2R), regulating its internalization and surface expression, and the cognate kinases GRK1 and GRK2. Determination of the crystal structures of Ca(2+)/NCS-1 alone and in complex with peptides derived from D2R and GRK1 reveals that the differential recognition is facilitated by the conformational flexibility of the C-lobe-binding site. We find that two copies of the D2R peptide bind within the hydrophobic crevice on Ca(2+)/NCS-1, but only one copy of the GRK1 peptide binds. The different binding modes are made possible by the C-lobe-binding site of NCS-1, which adopts alternative conformations in each complex. C-terminal residues Ser-178-Val-190 act in concert with the flexible EF3/EF4 loop region to effectively form different peptide-binding sites. In the Ca(2+)/NCS-1·D2R peptide complex, the C-terminal region adopts a 310 helix-turn-310 helix, whereas in the GRK1 peptide complex it forms an α-helix. Removal of Ser-178-Val-190 generated a C-terminal truncation mutant that formed a dimer, indicating that the NCS-1 C-terminal region prevents NCS-1 oligomerization. We propose that the flexible nature of the C-terminal region is essential to allow it to modulate its protein-binding sites and adapt its conformation to accommodate both ligands. This appears to be driven by the variability of the conformation of the C-lobe-binding site, which has ramifications for the target specificity and diversity of NCS-1. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Neuronal Calcium Sensor-1 Binds the D2 Dopamine Receptor and G-protein-coupled Receptor Kinase 1 (GRK1) Peptides Using Different Modes of Interactions*

PubMed Central

Pandalaneni, Sravan; Karuppiah, Vijaykumar; Saleem, Muhammad; Haynes, Lee P.; Burgoyne, Robert D.; Mayans, Olga; Derrick, Jeremy P.; Lian, Lu-Yun

2015-01-01

Neuronal calcium sensor-1 (NCS-1) is the primordial member of the neuronal calcium sensor family of EF-hand Ca2+-binding proteins. It interacts with both the G-protein-coupled receptor (GPCR) dopamine D2 receptor (D2R), regulating its internalization and surface expression, and the cognate kinases GRK1 and GRK2. Determination of the crystal structures of Ca2+/NCS-1 alone and in complex with peptides derived from D2R and GRK1 reveals that the differential recognition is facilitated by the conformational flexibility of the C-lobe-binding site. We find that two copies of the D2R peptide bind within the hydrophobic crevice on Ca2+/NCS-1, but only one copy of the GRK1 peptide binds. The different binding modes are made possible by the C-lobe-binding site of NCS-1, which adopts alternative conformations in each complex. C-terminal residues Ser-178–Val-190 act in concert with the flexible EF3/EF4 loop region to effectively form different peptide-binding sites. In the Ca2+/NCS-1·D2R peptide complex, the C-terminal region adopts a 310 helix-turn-310 helix, whereas in the GRK1 peptide complex it forms an α-helix. Removal of Ser-178–Val-190 generated a C-terminal truncation mutant that formed a dimer, indicating that the NCS-1 C-terminal region prevents NCS-1 oligomerization. We propose that the flexible nature of the C-terminal region is essential to allow it to modulate its protein-binding sites and adapt its conformation to accommodate both ligands. This appears to be driven by the variability of the conformation of the C-lobe-binding site, which has ramifications for the target specificity and diversity of NCS-1. PMID:25979333

Homogeneity in Heterogeneous Environments? An Analysis of Generation Theory Applied to College Generations

ERIC Educational Resources Information Center

Eddleman, Donna M.

2010-01-01

The prescriptive characteristics that have been assigned to the entire Millennial generation, suggest that the student population inhabiting college campuses today is neither demographically or experientially diverse. Current generation theory ignores specific environmental and regional influences, like those acknowledged in Bronfenbrenner's…

40 CFR 1065.512 - Duty cycle generation.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Duty cycle generation. 1065.512... CONTROLS ENGINE-TESTING PROCEDURES Performing an Emission Test Over Specified Duty Cycles § 1065.512 Duty cycle generation. (a) Generate duty cycles according to this section if the standard-setting part...

40 CFR 1065.610 - Duty cycle generation.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Duty cycle generation. 1065.610... CONTROLS ENGINE-TESTING PROCEDURES Calculations and Data Requirements § 1065.610 Duty cycle generation. This section describes how to generate duty cycles that are specific to your engine, based on the...

Environment Modeling Using Runtime Values for JPF-Android

NASA Technical Reports Server (NTRS)

van der Merwe, Heila; Tkachuk, Oksana; Nel, Seal; van der Merwe, Brink; Visser, Willem

2015-01-01

Software applications are developed to be executed in a specific environment. This environment includes external native libraries to add functionality to the application and drivers to fire the application execution. For testing and verification, the environment of an application is simplified abstracted using models or stubs. Empty stubs, returning default values, are simple to generate automatically, but they do not perform well when the application expects specific return values. Symbolic execution is used to find input parameters for drivers and return values for library stubs, but it struggles to detect the values of complex objects. In this work-in-progress paper, we explore an approach to generate drivers and stubs based on values collected during runtime instead of using default values. Entry-points and methods that need to be modeled are instrumented to log their parameters and return values. The instrumented applications are then executed using a driver and instrumented libraries. The values collected during runtime are used to generate driver and stub values on- the-fly that improve coverage during verification by enabling the execution of code that previously crashed or was missed. We are implementing this approach to improve the environment model of JPF-Android, our model checking and analysis tool for Android applications.

40 CFR 86.1333-2010 - Transient test cycle generation.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 19 2010-07-01 2010-07-01 false Transient test cycle generation. 86... (CONTINUED) Emission Regulations for New Otto-Cycle and Diesel Heavy-Duty Engines; Gaseous and Particulate Exhaust Test Procedures § 86.1333-2010 Transient test cycle generation. (a) Generating transient test...

40 CFR 262.216 - Non-laboratory hazardous waste generated at an eligible academic entity.

Code of Federal Regulations, 2012 CFR

2012-07-01

... generated at an eligible academic entity. 262.216 Section 262.216 Protection of Environment ENVIRONMENTAL... Laboratories Owned by Eligible Academic Entities § 262.216 Non-laboratory hazardous waste generated at an eligible academic entity. An eligible academic entity that generates hazardous waste outside of a...

40 CFR 262.216 - Non-laboratory hazardous waste generated at an eligible academic entity.

Code of Federal Regulations, 2010 CFR

2010-07-01

... generated at an eligible academic entity. 262.216 Section 262.216 Protection of Environment ENVIRONMENTAL... Laboratories Owned by Eligible Academic Entities § 262.216 Non-laboratory hazardous waste generated at an eligible academic entity. An eligible academic entity that generates hazardous waste outside of a...

40 CFR 262.216 - Non-laboratory hazardous waste generated at an eligible academic entity.

Code of Federal Regulations, 2013 CFR

2013-07-01

... generated at an eligible academic entity. 262.216 Section 262.216 Protection of Environment ENVIRONMENTAL... Laboratories Owned by Eligible Academic Entities § 262.216 Non-laboratory hazardous waste generated at an eligible academic entity. An eligible academic entity that generates hazardous waste outside of a...

40 CFR 262.216 - Non-laboratory hazardous waste generated at an eligible academic entity.

Code of Federal Regulations, 2014 CFR

2014-07-01

... generated at an eligible academic entity. 262.216 Section 262.216 Protection of Environment ENVIRONMENTAL... Laboratories Owned by Eligible Academic Entities § 262.216 Non-laboratory hazardous waste generated at an eligible academic entity. An eligible academic entity that generates hazardous waste outside of a...

40 CFR 262.216 - Non-laboratory hazardous waste generated at an eligible academic entity.

Code of Federal Regulations, 2011 CFR

2011-07-01

... generated at an eligible academic entity. 262.216 Section 262.216 Protection of Environment ENVIRONMENTAL... Laboratories Owned by Eligible Academic Entities § 262.216 Non-laboratory hazardous waste generated at an eligible academic entity. An eligible academic entity that generates hazardous waste outside of a...

Spontaneous Contractility-Mediated Cortical Flow Generates Cell Migration in Three-Dimensional Environments

PubMed Central

Hawkins, Rhoda J.; Poincloux, Renaud; Bénichou, Olivier; Piel, Matthieu; Chavrier, Philippe; Voituriez, Raphaël

2011-01-01

We present a model of cell motility generated by actomyosin contraction of the cell cortex. We identify, analytically, dynamical instabilities of the cortex and show that they yield steady-state cortical flows, which, in turn, can induce cell migration in three-dimensional environments. This mechanism relies on the regulation of contractility by myosin, whose transport is explicitly taken into account in the model. Theoretical predictions are compared to experimental data of tumor cells migrating in three-dimensional matrigel and suggest that this mechanism could be a general mode of cell migration in three-dimensional environments. PMID:21889440

Attaining organizational commitment across different generations of nurses.

PubMed

Carver, Lara; Candela, Lori

2008-11-01

To inform nurse managers about the generational differences that exist among nurses, how it affects the work environment and how this information can be used to encourage organizational commitment. Every person is born into a generational cohort of peers who experience similar life experiences that go on to shape distinct generational characteristics. Thanks to delayed retirements, mid-life career changes, job re-entry and a small but significant group of younger graduates, the nursing profession is now experiencing four generations in the workforce: Veterans, Baby Boomers, Generation X and the Millennial Generation. At the same time, the literature on organizational commitment is expanding and can provide a compelling context through which to view generational differences among nurses. As part of an overall strategy to increase organizational commitment, consideration of generational differences in nurses can be helpful in leading to increased job satisfaction, increased productivity and decreased turnover among staff. In the face of the global nursing shortage, managers should increase their knowledge of generational diversity just as they have with ethnic and cultural diversity in the past. Understanding how to relate to the different generations and tap into their individual strengths can lead to improved nursing work environments.

Automatic generation of Web mining environments

NASA Astrophysics Data System (ADS)

Cibelli, Maurizio; Costagliola, Gennaro

1999-02-01

The main problem related to the retrieval of information from the world wide web is the enormous number of unstructured documents and resources, i.e., the difficulty of locating and tracking appropriate sources. This paper presents a web mining environment (WME), which is capable of finding, extracting and structuring information related to a particular domain from web documents, using general purpose indices. The WME architecture includes a web engine filter (WEF), to sort and reduce the answer set returned by a web engine, a data source pre-processor (DSP), which processes html layout cues in order to collect and qualify page segments, and a heuristic-based information extraction system (HIES), to finally retrieve the required data. Furthermore, we present a web mining environment generator, WMEG, that allows naive users to generate a WME specific to a given domain by providing a set of specifications.

PCG: A prototype incremental compilation facility for the SAGA environment, appendix F

NASA Technical Reports Server (NTRS)

Kimball, Joseph John

1985-01-01

A programming environment supports the activity of developing and maintaining software. New environments provide language-oriented tools such as syntax-directed editors, whose usefulness is enhanced because they embody language-specific knowledge. When syntactic and semantic analysis occur early in the cycle of program production, that is, during editing, the use of a standard compiler is inefficient, for it must re-analyze the program before generating code. Likewise, it is inefficient to recompile an entire file, when the editor can determine that only portions of it need updating. The pcg, or Pascal code generation, facility described here generates code directly from the syntax trees produced by the SAGA syntax directed Pascal editor. By preserving the intermediate code used in the previous compilation, it can limit recompilation to the routines actually modified by editing.

Motion Planning and Synthesis of Human-Like Characters in Constrained Environments

NASA Astrophysics Data System (ADS)

Zhang, Liangjun; Pan, Jia; Manocha, Dinesh

We give an overview of our recent work on generating naturally-looking human motion in constrained environments with multiple obstacles. This includes a whole-body motion planning algorithm for high DOF human-like characters. The planning problem is decomposed into a sequence of low dimensional sub-problems. We use a constrained coordination scheme to solve the sub-problems in an incremental manner and a local path refinement algorithm to compute collision-free paths in tight spaces and satisfy the statically stable constraint on CoM. We also present a hybrid algorithm to generate plausible motion by combing the motion computed by our planner with mocap data. We demonstrate the performance of our algorithm on a 40 DOF human-like character and generate efficient motion strategies for object placement, bending, walking, and lifting in complex environments.

Properties and Corrosion Performance of Self-reinforced Composite PEEK for Proposed Use as a Modular Taper Gasket.

PubMed

Ouellette, Eric S; Gilbert, Jeremy L

2016-11-01

Fretting corrosion in medical alloys is a persistent problem, and the need for biomaterials that can effectively suppress mechanically assisted crevice corrosion in modular taper junctions or otherwise insulate metal-on-metal interfaces in mechanically demanding environments is as yet unmet. The purpose of this study is to characterize a novel material, self-reinforced composite polyetheretherketone (SRC-PEEK) and to evaluate its ability to inhibit fretting corrosion in a pin-on-disk metal-on-metal interface test. SRC-PEEK was fabricated by hot compaction of in-house-made PEEK fibers by compacting uniaxial layups at 344°C under a load of 18,000 N for 10 minutes. SRC-PEEK, bulk isotropic PEEK, and the in-house-made PEEK fibers were analyzed for thermal transitions (T g , T m ) through differential scanning calorimetry, crystallinity, crystal size, crystalline orientation (Hermanns orientation parameter) through wide-angle x-ray scattering, and modulus, tensile strength, yield stress, and strain to failure through monotonic tensile testing. SRC-insulated pin-on-disk samples were compared with metal-on-metal control samples in pin-on-disk fretting corrosion experiments using fretting current and fretting mechanics measurements. Fifty-micron cyclic motion at 2.5 Hz was applied to the interface, first over a range of loads (0.5-35 N) while held at -0.05 V versus Ag/AgCl and then over a range of voltages (-0.5 to 0.5 V) at a constant contact stress of 73 ± 19 MPa for SRC-PEEK and 209 ± 41 MPa for metal-on-metal, which were different for each group as a result of changes in true contact area due to variations in modulus between sample groups. Pins, disks, and SRC samples were imaged for damage (on alloy and SRC surfaces) and evidence of corrosion (on alloy pin and disk surfaces). SRC specimens were analyzed for traces of alloy transferred to the surface using energy dispersive spectroscopy after pin-on-disk testing. SRC-PEEK showed improved mechanical properties to bulk PEEK (modulus = 5.0 ± 0.3 GPa, 2.8 ± 0.1 GPa, respectively, p < 0.001) and higher crystallinity to bulk PEEK (44.2% ± 3%, 39.5% ± 0.5%, respectively, p = 0.039), but had comparable crystalline orientation as compared with the initial PEEK fibers. SRC-PEEK reduced fretting currents compared with metal-on-metal controls by two to three orders of magnitude in both variable load (4.0E-5 ± 3.8E-5 μA versus 2.9E-3 ± 7.1E-4 μA, respectively, p = 0.018) and variable potential (7.5E-6 ± 4.7E-6 μA versus 5.3E-3 ± 1.4E-3 μA, respectively, p = 0.022) fretting corrosion testing. Minimal damage was observed on surfaces insulated with SRC-PEEK, whereas control surfaces showed considerable fretting corrosion damage and metal transfer. The SRC-PEEK gaskets in this study demonstrated higher crystallinity and crystalline orientation and improved monotonic tensile properties compared with bulk PEEK with the ability to effectively insulate Ti6Al4V and CoCrMo alloy surfaces and prevent the initiation of fretting corrosion under high contact-stress conditions. This novel SRC-PEEK material may offer potential as a thin film gasket material for modular tapers. Pending further in vitro and in vivo analyses, this approach may be able to preserve the advantages of modular junctions for surgeons while potentially limiting the downside risks associated with mechanically assisted crevice corrosion.

Response of roseate tern to a shoreline protection project on Falkner Island, Connecticut

USGS Publications Warehouse

Rogers, C.J.; Spendelow, J.A.; Guilfoyle, Michael P.; Fischer, Richard A.; Pashley, David N.; Lott, Casey A.

2007-01-01

Construction was initiated following the 2000 tern breeding season for Phase 1 of a planned two-phase ?Shoreline Protection and Erosion Control Project? at the Falkner Island Unit of the USFWS Stewart B. McKinney National Wildlife Refuge located in Long Island Sound off the coast of Guilford, CT. When the Common Tern (Sterna hirundo) and federally endangered Roseate Tern (S. dougallii) arrived in spring 2001, they encountered several major habitat changes from what had existed in previous years. These changes included: a rock revetment covering most of the former nesting habitat on the beach from the northwestern section around the northern tip and covering about 60% of the eastern side; an elevated 60- ? 4-m shelf covering the beach and lower bank of the southwestern section; and about 2,000 sq m of devegetated areas on top of the island on the northeast side above the revetment, and about one-third of the southern half of the island. The southwest shelf was created by bulldozing and compacting extra construction fill and in situ materials. This shelf differed in internal structure from the main revetment on the north and eastern sections of the island because it lacked the deep internal crevices of the revetment. The deep internal crevices were created from the large stones and boulders (up to 2 tons) used in the construction of the main revetment. Small rock and gravel was used to fill the crevices to within 3 feet (0.9 m) of the surface of the revetment. Because half-buried tires and nest boxes for the six Roseate Tern (Sterna dougallii) sub-colony areas were deployed in similar patterns on the remaining beach, and nest boxes were placed on the newly elevated shelf areas several meters above previous locations on the now-covered beach areas, the distribution of Roseate Tern nests did not change much from 2000 to 2001. However, the movements of Roseate Tern chicks ? in many cases led by their parents towards traditional hiding places ? into the labyrinth of subterranean channels, especially in the main revetment area, made it difficult to measure chick growth and productivity as had been done for more than 12 years prior to construction. Also, observations of color-banded adults that were unable to locate and feed their young inside the main revetment, and of adults returning to courtship behavior and renesting after having hatched chicks from their initial clutches, indicated that a minimum of 20% of the chicks (mostly first hatched A-chicks, which usually have high rates of survival to fledging) that entered the main revetment died after doing so in 2001. The mortality rate of Roseate Tern chicks that entered the secondary revetment on the southwest shelf, however, was not unusually high in 2001. In an attempt to reduce the likelihood of nesting and chick losses in these sub-colonies, a research team led by the USGS in 2002-2003 did not put nest boxes on the northeast and east shelf areas where previous losses had been high. However, losses of tern eggs and young chicks to predatory Black-crowned Night Herons (Nycticorax nycticorax) were so great in 2002?2003 that few Roseate Tern chicks survived long enough to move into the main revetment area and little comparative survival data were collected. The USFWS continues to remove predatory night herons, to monitor the location and success of nesting Roseate Terns and to fill in some of problem areas near the tern nests in the main revetment. The extensive chick-searching fieldwork and observational procedures used by the USGS-led research team to determine the growth and survival of the Roseate Tern chicks at Falkner Island were not used in 2004?2005. The number of chicks lost in the revetment during these years is not known. Without additional fill, loss of chicks of this endangered species in the main revetment may rise again even though the night heron predation problem has been reduced.

Applications of sub-audible speech recognition based upon electromyographic signals

NASA Technical Reports Server (NTRS)

Jorgensen, C. Charles (Inventor); Betts, Bradley J. (Inventor)

2009-01-01

Method and system for generating electromyographic or sub-audible signals (''SAWPs'') and for transmitting and recognizing the SAWPs that represent the original words and/or phrases. The SAWPs may be generated in an environment that interferes excessively with normal speech or that requires stealth communications, and may be transmitted using encoded, enciphered or otherwise transformed signals that are less subject to signal distortion or degradation in the ambient environment.

Leveraging Environmental Correlations: The Thermodynamics of Requisite Variety

NASA Astrophysics Data System (ADS)

Boyd, Alexander B.; Mandal, Dibyendu; Crutchfield, James P.

2017-06-01

Key to biological success, the requisite variety that confronts an adaptive organism is the set of detectable, accessible, and controllable states in its environment. We analyze its role in the thermodynamic functioning of information ratchets—a form of autonomous Maxwellian Demon capable of exploiting fluctuations in an external information reservoir to harvest useful work from a thermal bath. This establishes a quantitative paradigm for understanding how adaptive agents leverage structured thermal environments for their own thermodynamic benefit. General ratchets behave as memoryful communication channels, interacting with their environment sequentially and storing results to an output. The bulk of thermal ratchets analyzed to date, however, assume memoryless environments that generate input signals without temporal correlations. Employing computational mechanics and a new information-processing Second Law of Thermodynamics (IPSL) we remove these restrictions, analyzing general finite-state ratchets interacting with structured environments that generate correlated input signals. On the one hand, we demonstrate that a ratchet need not have memory to exploit an uncorrelated environment. On the other, and more appropriate to biological adaptation, we show that a ratchet must have memory to most effectively leverage structure and correlation in its environment. The lesson is that to optimally harvest work a ratchet's memory must reflect the input generator's memory. Finally, we investigate achieving the IPSL bounds on the amount of work a ratchet can extract from its environment, discovering that finite-state, optimal ratchets are unable to reach these bounds. In contrast, we show that infinite-state ratchets can go well beyond these bounds by utilizing their own infinite "negentropy". We conclude with an outline of the collective thermodynamics of information-ratchet swarms.

Children and the Environment. The State of the Environment, 1990.

ERIC Educational Resources Information Center

United Nations Children's Fund, New York, NY.

This report summarizes the ways in which children in developing nations have been adversely affected by their environment and what changes could be made to mitigate these circumstances. Chapter 1 discusses the environment, children, and future generations, pointing out the special needs children have now and will have in the future, the role of…

An improved offset generator developed for Allan deviation measurement of ultra stable frequency standards

NASA Technical Reports Server (NTRS)

Hamell, Robert L.; Kuhnle, Paul F.; Sydnor, Richard L.

1992-01-01

Measuring the performance of ultra stable frequency standards such as the Superconducting Cavity Maser Oscillator (SCMO) necessitates improvement of some test instrumentation. The frequency stability test equipment used at JPL includes a 1 Hz Offset Generator to generate a beat frequency between a pair of 100 MHz signals that are being compared. The noise floor of the measurement system using the current Offset Generator is adequate to characterize stability of hydrogen masers, but it is not adequate for the SCMO. A new Offset Generator with improved stability was designed and tested at JPL. With this Offset Generator and a new Zero Crossing Detector, recently developed at JPL, the measurement flow was reduced by a factor of 5.5 at 1 second tau, 3.0 at 1000 seconds, and 9.4 at 10,000 seconds, compared against the previous design. In addition to the new circuit designs of the Offset Generator and Zero Crossing Detector, tighter control of the measurement equipment environment was required to achieve this improvement. The design of this new Offset Generator are described, along with details of the environment control methods used.

Evaluation on the Efficiency of Biomass Power Generation Industry in China

PubMed Central

Sun, Dong; Guo, Sen

2014-01-01

As a developing country with large population, China is facing the problems of energy resource shortage and growing environmental pollution arising from the coal-dominated energy structure. Biomass energy, as a kind of renewable energy with the characteristics of being easy to store and friendly to environment, has become the focus of China's energy development in the future. Affected by the advanced power generation technology and diversified geography environment, the biomass power generation projects show new features in recent years. Hence, it is necessary to evaluate the efficiency of biomass power generation industry by employing proper method with the consideration of new features. In this paper, the regional difference as a new feature of biomass power generation industry is taken into consideration, and the AR model is employed to modify the zero-weight issue when using data envelopment analysis (DEA) method to evaluate the efficiency of biomass power generation industry. 30 biomass power generation enterprises in China are selected as the sample, and the efficiency evaluation is performed. The result can provide some insights into the sustainable development of biomass power generation industry in China. PMID:25093209

Emerging Technologies, ISD, and Learning Environments: Critical Perspectives.

ERIC Educational Resources Information Center

Hannafin, Michael J.

1992-01-01

Reviews the evolution of instructional systems design and computer-based learning environments, focusing on the effects of technological advances. Classification of learning environments is discussed in the context of the dimensions of scope (macrolevel or microlevel), user activity (generative or mathemagenic), educational activity (goal-directed…

Map generation in unknown environments by AUKF-SLAM using line segment-type and point-type landmarks

NASA Astrophysics Data System (ADS)

Nishihta, Sho; Maeyama, Shoichi; Watanebe, Keigo

2018-02-01

Recently, autonomous mobile robots that collect information at disaster sites are being developed. Since it is difficult to obtain maps in advance in disaster sites, the robots being capable of autonomous movement under unknown environments are required. For this objective, the robots have to build maps, as well as the estimation of self-location. This is called a SLAM problem. In particular, AUKF-SLAM which uses corners in the environment as point-type landmarks has been developed as a solution method so far. However, when the robots move in an environment like a corridor consisting of few point-type features, the accuracy of self-location estimated by the landmark is decreased and it causes some distortions in the map. In this research, we propose AUKF-SLAM which uses walls in the environment as a line segment-type landmark. We demonstrate that the robot can generate maps in unknown environment by AUKF-SLAM, using line segment-type and point-type landmarks.

Experimental evolution: Assortative mating and sexual selection, independent of local adaptation, lead to reproductive isolation in the nematode Caenorhabditis remanei.

PubMed

Castillo, Dean M; Burger, Melissa K; Lively, Curtis M; Delph, Lynda F

2015-12-01

Using experimental evolution, we investigated the contributions of ecological divergence, sexual selection, and genetic drift to the evolution of reproductive isolation in Caenorhabditis remanei. The nematodes were reared on two different environments for 100 generations. They were assayed for fitness on both environments after 30, 64, and 100 generations, and hybrid fitness were analyzed after 64 and 100 generations. Mating propensity within and between populations was also analyzed. The design allowed us to determine whether local adaptation was synchronous with pre- and postzygotic reproductive isolation. Prezygotic isolation evolved quickly but was unconnected with adaptation to the divergent environments. Instead, prezygotic isolation was driven by mate preferences favoring individuals from the same replicate population. A bottleneck treatment, meant to enhance the opportunity for genetic drift, had no effect on prezygotic isolation. Postzygotic isolation occurred in crosses where at least one population had a large fitness advantage in its "home" environment. Taken together, our results suggest that prezygotic isolation did not depend on drift or adaptation to divergent environments, but instead resulted from differences in sexual interactions within individual replicates. Furthermore, our results suggest that postzygotic isolation can occur between populations even when only one population has greater fitness in its home environment. © 2015 The Author(s). Evolution © 2015 The Society for the Study of Evolution.

Comparative mapping of quantitative trait loci for tassel-related traits of maize in F2:3 and RIL populations.

PubMed

Yi, Qiang; Liu, Yinghong; Zhang, Xiangge; Hou, Xianbin; Zhang, Junjie; Liu, Hanmei; Hu, Yufeng; Yu, Guowu; Huang, Yubi

2018-03-01

Tassel architecture is an important trait in maize breeding and hybrid seed production. In this study, we investigated total tassel length (TTL) and tassel branch number (TBN) in 266 F 2:3 families across six environments and in 301 recombinant inbred lines (RILs) across three environments, where all the plants were derived from a cross between 08-641 and Ye478. We compared the genetic architecture of the two traits across two generations through combined analysis. In total, 27 quantitative trait loci (QTLs) (15 in F 2:3 ; 16 in RIL), two QTL × environment interactions (both in F 2:3 ), 11 pairs of epistatic interactions (seven in F 2:3 ; four in RIL) and four stable QTLs in both the F 2:3 and RILs were detected. The RIL population had higher detection power than the F 2:3 population. Nevertheless, QTL × environment interactions and epistatic interactions could be more easily detected in the F 2:3 population than in the RILs. Overall, the QTL mapping results in the F 2:3 and RILs were greatly influenced by genetic generations and environments. Finally, fine mapping for a novel and major QTL, qTTL-2-3 (bin 2.07), which accounted for over 8.49% of the phenotypic variation across different environments and generations, could be useful in marker-assisted breeding.

The influence of an uncertain force environment on reshaping trial-to-trial motor variability.

PubMed

Izawa, Jun; Yoshioka, Toshinori; Osu, Rieko

2014-09-10

Motor memory is updated to generate ideal movements in a novel environment. When the environment changes every trial randomly, how does the brain incorporate this uncertainty into motor memory? To investigate how the brain adapts to an uncertain environment, we considered a reach adaptation protocol where individuals practiced moving in a force field where a noise was injected. After they had adapted, we measured the trial-to-trial variability in the temporal profiles of the produced hand force. We found that the motor variability was significantly magnified by the adaptation to the random force field. Temporal profiles of the motor variance were significantly dissociable between two different types of random force fields experienced. A model-based analysis suggests that the variability is generated by noise in the gains of the internal model. It further suggests that the trial-to-trial motor variability magnified by the adaptation in a random force field is generated by the uncertainty of the internal model formed in the brain as a result of the adaptation.

Solar Power Generation in Extreme Space Environments

NASA Technical Reports Server (NTRS)

Elliott, Frederick W.; Piszczor, Michael F.

2016-01-01

The exploration of space requires power for guidance, navigation, and control; instrumentation; thermal control; communications and data handling; and many subsystems and activities. Generating sufficient and reliable power in deep space through the use of solar arrays becomes even more challenging as solar intensity decreases and high radiation levels begin to degrade the performance of photovoltaic devices. The Extreme Environments Solar Power (EESP) project goal is to develop advanced photovoltaic technology to address these challenges.

Tire wear particles in the aquatic environment - A review on generation, analysis, occurrence, fate and effects.

PubMed

Wagner, Stephan; Hüffer, Thorsten; Klöckner, Philipp; Wehrhahn, Maren; Hofmann, Thilo; Reemtsma, Thorsten

2018-08-01

Tire wear particles (TWP), generated from tire material during use on roads have gained increasing attention as part of organic particulate contaminants, such as microplastic, in aquatic environments. The available information on properties and generation of TWP, analytical techniques to determine TWP, emissions, occurrence and behavior and ecotoxicological effects of TWP are reviewed with a focus on surface water as a potential receptor. TWP emissions are traffic related and contribute 5-30% to non-exhaust emissions from traffic. The mass of TWP generated is estimated at 1,327,000 t/a for the European Union, 1,120,000 t/a for the United States and 133,000 t/a for Germany. For Germany, this is equivalent to four times the amount of pesticides used. The mass of TWP ultimately entering the aquatic environment strongly depends on the extent of collection and treatment of road runoff, which is highly variable. For the German highways it is estimated that up to 11,000 t/a of TWP reach surface waters. Data on TWP concentrations in the environment, including surface waters are fragmentary, which is also due to the lack of suitable analytical methods for their determination. Information on TWP properties such as density and size distribution are missing; this hampers assessing the fate of TWP in the aquatic environment. Effects in the aquatic environment may stem from TWP itself or from compounds released from TWP. It is concluded that reliable knowledge on transport mechanism to surface waters, concentrations in surface waters and sediments, effects of aging, environmental half-lives of TWP as well as effects on aquatic organisms are missing. These aspects need to be addressed to allow for the assessment of risk of TWP in an aquatic environment. Copyright © 2018 Elsevier Ltd. All rights reserved.

The Phoretic Motion Experiment (PME) definition phase

NASA Technical Reports Server (NTRS)

Eaton, L. R.; Neste, S. L. (Editor)

1982-01-01

The aerosol generator and the charge flow devices (CFD) chamber which were designed for zero-gravity operation was analyzed. Characteristics of the CFD chamber and aerosol generator which would be useful for cloud physics experimentation in a one-g as well as a zero-g environment are documented. The Collision type of aerosol generator is addressed. Relationships among the various input and output parameters are derived and subsequently used to determine the requirements on the controls of the input parameters to assure a given error budget of an output parameter. The CFD chamber operation in a zero-g environment is assessed utilizing a computer simulation program. Low nuclei critical supersaturation and high experiment accuracies are emphasized which lead to droplet growth times extending into hundreds of seconds. The analysis was extended to assess the performance constraints of the CFD chamber in a one-g environment operating in the horizontal mode.

Elastic parabolic equation solutions for oceanic T-wave generation and propagation from deep seismic sources.

PubMed

Frank, Scott D; Collis, Jon M; Odom, Robert I

2015-06-01

Oceanic T-waves are earthquake signals that originate when elastic waves interact with the fluid-elastic interface at the ocean bottom and are converted to acoustic waves in the ocean. These waves propagate long distances in the Sound Fixing and Ranging (SOFAR) channel and tend to be the largest observed arrivals from seismic events. Thus, an understanding of their generation is important for event detection, localization, and source-type discrimination. Recently benchmarked seismic self-starting fields are used to generate elastic parabolic equation solutions that demonstrate generation and propagation of oceanic T-waves in range-dependent underwater acoustic environments. Both downward sloping and abyssal ocean range-dependent environments are considered, and results demonstrate conversion of elastic waves into water-borne oceanic T-waves. Examples demonstrating long-range broadband T-wave propagation in range-dependent environments are shown. These results confirm that elastic parabolic equation solutions are valuable for characterization of the relationships between T-wave propagation and variations in range-dependent bathymetry or elastic material parameters, as well as for modeling T-wave receptions at hydrophone arrays or coastal receiving stations.

High temperature, harsh environment sensors for advanced power generation systems

NASA Astrophysics Data System (ADS)

Ohodnicki, P. R.; Credle, S.; Buric, M.; Lewis, R.; Seachman, S.

2015-05-01

One mission of the Crosscutting Technology Research program at the National Energy Technology Laboratory is to develop a suite of sensors and controls technologies that will ultimately increase efficiencies of existing fossil-fuel fired power plants and enable a new generation of more efficient and lower emission power generation technologies. The program seeks to accomplish this mission through soliciting, managing, and monitoring a broad range of projects both internal and external to the laboratory which span sensor material and device development, energy harvesting and wireless telemetry methodologies, and advanced controls algorithms and approaches. A particular emphasis is placed upon harsh environment sensing for compatibility with high temperature, erosive, corrosive, and highly reducing or oxidizing environments associated with large-scale centralized power generation. An overview of the full sensors and controls portfolio is presented and a selected set of current and recent research successes and on-going projects are highlighted. A more detailed emphasis will be placed on an overview of the current research thrusts and successes of the in-house sensor material and device research efforts that have been established to support the program.

Initial Flow Matching Results of MHD Energy Bypass on a Supersonic Turbojet Engine Using the Numerical Propulsion System Simulation (NPSS) Environment

NASA Technical Reports Server (NTRS)

Benyo, Theresa L.

2010-01-01

Preliminary flow matching has been demonstrated for a MHD energy bypass system on a supersonic turbojet engine. The Numerical Propulsion System Simulation (NPSS) environment was used to perform a thermodynamic cycle analysis to properly match the flows from an inlet to a MHD generator and from the exit of a supersonic turbojet to a MHD accelerator. Working with various operating conditions such as the enthalpy extraction ratio and isentropic efficiency of the MHD generator and MHD accelerator, interfacing studies were conducted between the pre-ionizers, the MHD generator, the turbojet engine, and the MHD accelerator. This paper briefly describes the NPSS environment used in this analysis and describes the NPSS analysis of a supersonic turbojet engine with a MHD generator/accelerator energy bypass system. Results from this study have shown that using MHD energy bypass in the flow path of a supersonic turbojet engine increases the useful Mach number operating range from 0 to 3.0 Mach (not using MHD) to an explored and desired range of 0 to 7.0 Mach.

Virtual Education: Guidelines for Using Games Technology

ERIC Educational Resources Information Center

Schofield, Damian

2014-01-01

Advanced three-dimensional virtual environment technology, similar to that used by the film and computer games industry, can allow educational developers to rapidly create realistic online virtual environments. This technology has been used to generate a range of interactive Virtual Reality (VR) learning environments across a spectrum of…

Generation of Adaptive Gait Patterns for Quadruped Robot with CPG Network including Motor Dynamic Model

NASA Astrophysics Data System (ADS)

Son, Yurak; Kamano, Takuya; Yasuno, Takashi; Suzuki, Takayuki; Harada, Hironobu

This paper describes the generation of adaptive gait patterns using new Central Pattern Generators (CPGs) including motor dynamic models for a quadruped robot under various environment. The CPGs act as the flexible oscillators of the joints and make the desired angle of the joints. The CPGs are mutually connected each other, and the sets of their coupling parameters are adjusted by genetic algorithm so that the quadruped robot can realize the stable and adequate gait patterns. As a result of generation, the suitable CPG networks for not only a walking straight gait pattern but also rotation gait patterns are obtained. Experimental results demonstrate that the proposed CPG networks are effective to automatically adjust the adaptive gait patterns for the tested quadruped robot under various environment. Furthermore, the target tracking control based on image processing is achieved by combining the generated gait patterns.

A spectral study of a radio-frequency plasma-generated flux of atomic oxygen

NASA Technical Reports Server (NTRS)

Batten, Carmen E.; Brown, Kenneth G.; Lewis, Beverley W.

1994-01-01

The active environment of a radio-frequency (RF) plasma generator, with and without low-pressure oxygen, has been characterized through the identification of emission lines in the spectral region from 250 to 900 nm. The environment is shown to be dependent on the partial pressure of oxygen and the power applied to the RF generator. Atomic oxygen has been found in significant amounts as well as atomic hydrogen and the molecular oxygen species O2((sup 1)Sigma). The only charged species observed was the singly charged molecular ion O2(+). With a polymer specimen in the plasma chamber, carbon monoxide was also observed. The significance of these observations with respect to previous studies using this type of generator to stimulate material degradation in space is discussed. The possibility of using these generators as atomic oxygen sources in the development of oxygen atom fluorescence sensors is explored.

Analysis of carbon dioxide emission of gas fuelled cogeneration plant

NASA Astrophysics Data System (ADS)

Nordin, Adzuieen; Amin, M.; Majid, A.

2013-12-01

Gas turbines are widely used for power generation. In cogeneration system, the gas turbine generates electricity and the exhaust heat from the gas turbine is used to generate steam or chilled water. Besides enhancing the efficiency of the system, the process assists in reducing the emission of CO2 to the environment. This study analyzes the amount of CO2 emission by Universiti Teknologi Petronas gas fuelled cogeneration system using energy balance equations. The results indicate that the cogeneration system reduces the CO2 emission to the environment by 60%. This finding could encourage the power plant owners to install heat recovery systems to their respective plants.

Wind Power: A Renewable Energy Source for Mars Transit Vehicle

NASA Technical Reports Server (NTRS)

Flynn, Michael; Kohout, Lisa; Kliss, Mark (Technical Monitor)

1998-01-01

The Martian environment presents significant design challenges for the development of power generation systems. Nuclear-based systems may not be available due to political and safety concerns. The output of photovoltaics are limited by a solar intensity of 580 W/sqm as compared to 1353 W/sqm on Earth. The presence of dust particles in the Mars atmosphere will further reduce the photovoltaic output. Also, energy storage for a 12-hour night period must be provided. In this challenging environment, wind power generation capabilities may provide a viable option as a Martian power generation system. This paper provides an analysis of the feasibility of such a system.

Why work in perioperative nursing? Baby boomers and Generation Xers tell all.

PubMed

Thompson, Julia A

2007-10-01

This quantitative and qualitative study explored factors that influence nurses of different age groups to choose to work in and remain in the specialty of OR nursing, including the effect of work environment perceptions. Baby boomer nurses (n = 130) and Generation X nurses (n = 117) were surveyed, and seven RNs from each group also participated in semistructured interviews. Results showed that nurses of both age groups were more alike than different in the factors that influence them to choose and remain in OR nursing and in their perceptions of their work environment. Baby Boomers indicated a higher level of commitment to their jobs than did Generation Xers.

40 CFR 73.81 - Qualified conservation measures and renewable energy generation.

Code of Federal Regulations, 2012 CFR

2012-07-01

... renewable energy generation. 73.81 Section 73.81 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) SULFUR DIOXIDE ALLOWANCE SYSTEM Energy Conservation and Renewable Energy Reserve § 73.81 Qualified conservation measures and renewable energy generation. (a) Qualified energy...

40 CFR 73.81 - Qualified conservation measures and renewable energy generation.

Code of Federal Regulations, 2014 CFR

2014-07-01

... renewable energy generation. 73.81 Section 73.81 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) SULFUR DIOXIDE ALLOWANCE SYSTEM Energy Conservation and Renewable Energy Reserve § 73.81 Qualified conservation measures and renewable energy generation. (a) Qualified energy...

40 CFR 73.81 - Qualified conservation measures and renewable energy generation.

Code of Federal Regulations, 2013 CFR

2013-07-01

... renewable energy generation. 73.81 Section 73.81 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) SULFUR DIOXIDE ALLOWANCE SYSTEM Energy Conservation and Renewable Energy Reserve § 73.81 Qualified conservation measures and renewable energy generation. (a) Qualified energy...

Can We Communicate with Other Generations?

ERIC Educational Resources Information Center

Mellert, Robert B.

Communicating with future generations is not merely a question of "how" to communicate, but also of "what." Our major moral responsibilities to future generations concern the size of future populations, conservation of nonrenewable resources, diversity of the gene pool, and quality of the environment. To determine our…

Albumin binds self-assembling dyes as specific polymolecular ligands.

PubMed

Stopa, Barbara; Rybarska, Janina; Drozd, Anna; Konieczny, Leszek; Król, Marcin; Lisowski, Marek; Piekarska, Barbara; Roterman, Irena; Spólnik, Paweł; Zemanek, Grzegorz

2006-12-15

Self-assembling dyes with a structure related to Congo red (e.g. Evans blue) form polymolecular complexes with albumin. The dyes, which are lacking a self-assembling property (Trypan blue, ANS) bind as single molecules. The supramolecular character of dye ligands bound to albumin was demonstrated by indicating the complexation of dye molecules outnumbering the binding sites in albumin and by measuring the hydrodynamic radius of albumin which is growing upon complexation of self-assembling dye in contrast to dyes lacking this property. The self-assembled character of Congo red was also proved using it as a carrier introducing to albumin the intercalated nonbonding foreign compounds. Supramolecular, ordered character of the dye in the complex with albumin was also revealed by finding that self-assembling dyes become chiral upon complexation. Congo red complexation makes albumin less resistant to low pH as concluded from the facilitated N-F transition, observed in studies based on the measurement of hydrodynamic radius. This particular interference with protein stability and the specific changes in digestion resulted from binding of Congo red suggest that the self-assembled dye penetrates the central crevice of albumin.

Structure zone diagram and particle incorporation of nickel brush plated composite coatings

PubMed Central

Isern, L.; Impey, S.; Almond, H.; Clouser, S. J.; Endrino, J. L.

2017-01-01

This work studies the deposition of aluminium-incorporated nickel coatings by brush electroplating, focusing on the electroplating setup and processing parameters. The setup was optimised in order to increase the volume of particle incorporation. The optimised design focused on increasing the plating solution flow to avoid sedimentation, and as a result the particle transport experienced a three-fold increase when compared with the traditional setup. The influence of bath load, current density and the brush material used was investigated. Both current density and brush material have a significant impact on the morphology and composition of the coatings. Higher current densities and non-abrasive brushes produce rough, particle-rich samples. Different combinations of these two parameters influence the surface characteristics differently, as illustrated in a Structure Zone Diagram. Finally, surfaces featuring crevices and peaks incorporate between 3.5 and 20 times more particles than smoother coatings. The presence of such features has been quantified using average surface roughness Ra and Abbott-Firestone curves. The combination of optimised setup and rough surface increased the particle content of the composite to 28 at.%. PMID:28300159

Wintering bats of the upper Snake River Plain: occurrence in lava-tube caves

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

Genter, D.L.

Distribution and habitat selection of hibernating bats at the Idaho National Engineering Laboratory (INEL) and adjacent area are reported. Exploration of over 30 lava-tube caves revealed that two species, Myotis leibii and Plecotus townsendii, hibernate in the upper Snake River Plain. Five species, M. lucifugus, M. evotis, Eptesicus fuscus, Lasionycteris noctivagans, and Lasiurus cinereus are considered migratory. Myotis leibii and P. townsendii hibernate throughout much of the area, occasionally in mixed-species groups. Myotis leibii uses the dark and protected regions of the cave, usually wedged into tiny pockets and crevices near or at the highest portion of the ceiling. Individualsmore » of P. townsendii may be found at any height or depth in the cave. Temperature appears to be primary limiting factor in habitat selection. Myotis leibii was found in significantly cooler air temperatures than P. townsendii. Neither species tolerated continuous temperatures below 1.5 C. Relative humidity does not seem to be a significant factor in the distribution or habitat selection of the two species in lava-tube caves. 18 references, 1 figure, 1 table.« less

Fifty million years of herbivory on coral reefs: fossils, fish and functional innovations

PubMed Central

Bellwood, D. R.; Goatley, C. H. R.; Brandl, S. J.; Bellwood, O.

2014-01-01

The evolution of ecological processes on coral reefs was examined based on Eocene fossil fishes from Monte Bolca, Italy and extant species from the Great Barrier Reef, Australia. Using ecologically relevant morphological metrics, we investigated the evolution of herbivory in surgeonfishes (Acanthuridae) and rabbitfishes (Siganidae). Eocene and Recent surgeonfishes showed remarkable similarities, with grazers, browsers and even specialized, long-snouted forms having Eocene analogues. These long-snouted Eocene species were probably pair-forming, crevice-feeding forms like their Recent counterparts. Although Eocene surgeonfishes likely played a critical role as herbivores during the origins of modern coral reefs, they lacked the novel morphologies seen in modern Acanthurus and Siganus (including eyes positioned high above their low-set mouths). Today, these forms dominate coral reefs in both abundance and species richness and are associated with feeding on shallow, exposed algal turfs. The radiation of these new forms, and their expansion into new habitats in the Oligocene–Miocene, reflects the second phase in the development of fish herbivory on coral reefs that is closely associated with the exploitation of highly productive short algal turfs. PMID:24573852

Anatomy of the left atrium for interventional electrophysiologists.

PubMed

Ho, Siew Yen; McCarthy, Karen P

2010-05-01

Increasingly, interventional procedures require accessing the left atrium from the inside of the heart as well as from the pericardial space. The right phrenic nerve running along the fibrous pericardium is close to the atrial insertion of the right superior pulmonary vein while the left phrenic nerve passes over the left atrial appendage. Posteriorly, the esophagus descends adjacent to the fibrous pericardium covering the posterior and postero-inferior walls of the left atrium. The component parts of the left atrium are reviewed with emphasis on the structure of the atrial septum, the left atrial ridge, the mitral isthmus, and the left atrial walls. Although the atrial walls are mainly smooth, pits and crevices are common in the region of the mitral isthmus and the vicinity of the os of the atrial appendage. The muscular rim around the valve of the oval fossa delimits the extent of the true atrial septum. Interatrial muscular connections exist at the septum, along Bachmann's bundle and also at the muscular sleeves of the coronary sinus and pulmonary veins. Anatomical features relevant to interventional electrophysiologists are highlighted.

Dust Accumulation on Mars

NASA Technical Reports Server (NTRS)

2005-01-01

Since landing on Mars a year ago, NASA's pair of six-wheeled geologists have been constantly exposed to martian winds and dust. As a result, the Spirit rover has gradually experienced a slight decline in power as a thin layer of dust has accumulated on the solar panels, blocking some of the sunlight that is converted to electricity. In this enlarged image of a postage-stamp-size (3-centimeter-square, 1.2-inch-square) portion of one of Spirit's solar panels, a fine layer of martian dust coats electrical connections and metal surfaces. Individual silt grains or clumps of dust are visible where sediment has accumulated in crevices between solar cells and circuits. The upper right half of the image shows the edge of one of the rover's solar cells. The lower left half shows electrical wires bonded with silicon adhesive to the underlying composite surface; the circular abrasions are the result of sanding by hand on Earth. The braided wire is connected to a thermocouple used to measure temperature based on electrical resistance. Spirit took this image with its microscopic imager on martian day, or sol, 350 (Dec. 26, 2004).

Particle-Film Plasmons on Periodic Silver Film over Nanosphere (AgFON): A Hybrid Plasmonic Nanoarchitecture for Surface-Enhanced Raman Spectroscopy.

PubMed

Lee, Jiwon; Zhang, Qianpeng; Park, Seungyoung; Choe, Ayoung; Fan, Zhiyong; Ko, Hyunhyub

2016-01-13

Plasmonic systems based on particle-film plasmonic couplings have recently attracted great attention because of the significantly enhanced electric field at the particle-film gaps. Here, we introduce a hybrid plasmonic architecture utilizing combined plasmonic effects of particle-film gap plasmons and silver film over nanosphere (AgFON) substrates. When gold nanoparticles (AuNPs) are assembled on AgFON substrates with controllable particle-film gap distances, the AuNP-AgFON system supports multiple plasmonic couplings from interparticle, particle-film, and crevice gaps, resulting in a huge surface-enhanced Raman spectroscopy (SERS) effect. We show that the periodicity of AgFON substrates and the particle-film gaps greatly affects the surface plasmon resonances, and thus, the SERS effects due to the interplay between multiple plasmonic couplings. The optimally designed AuNP-AgFON substrate shows a SERS enhancement of 233 times compared to the bare AgFON substrate. The ultrasensitive SERS sensing capability is also demonstrated by detecting glutathione, a neurochemical molecule that is an important antioxidant, down to the 10 pM level.

Surface Characterization of Populus during Caldicellulosiruptor bescii Growth by TOF-SIMS Analysis

DOE PAGES

Tolbert, Allison K.; Young, Jenna M.; Jung, Seokwon; ...

2017-01-30

Caldicellulosiruptor bescii is a thermophilic, anaerobic bacterium that is capable of utilizing unpretreated biomass in addition to breaking down cellulose and hemicellulose into simple sugars. Despite the fact that C. bescii must first bind to the surface of the biomass, there has been no analysis of the morphological or chemical changes to the biomass surface as a result of incubation with the micro-organism. To understand more about C. bescii growth, juvenile poplar stems were sectioned (80 μm thick) and incubated with C. bescii beyond the typical 24 h experiment length. Monitoring the cell counts during incubation revealed a biphasic growthmore » pattern. The impact the micro-organism had on the surface was determined by scanning electron microscopy (SEM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS), which showed physical crevices in the cell wall caused by the C. bescii along with a decrease of polysaccharide ions and an increase in lignin ions on the poplar surface. Employing infrared microspectroscopy, the decreasing trend was corroborated.« less

Structure and dynamics of protein waters revealed by radiolysis and mass spectrometry

PubMed Central

Gupta, Sayan; D’Mello, Rhijuta; Chance, Mark R.

2012-01-01

Water is critical for the structure, stability, and functions of macromolecules. Diffraction and NMR studies have revealed structure and dynamics of bound waters at atomic resolution. However, localizing the sites and measuring the dynamics of bound waters, particularly on timescales relevant to catalysis and macromolecular assembly, is quite challenging. Here we demonstrate two techniques: first, temperature-dependent radiolytic hydroxyl radical labeling with a mass spectrometry (MS)-based readout to identify sites of bulk and bound water interactions with surface and internal residue side chains, and second, H218O radiolytic exchange coupled MS to measure the millisecond dynamics of bound water interactions with various internal residue side chains. Through an application of the methods to cytochrome c and ubiquitin, we identify sites of water binding and measure the millisecond dynamics of bound waters in protein crevices. As these MS-based techniques are very sensitive and not protein size limited, they promise to provide unique insights into protein–water interactions and water dynamics for both small and large proteins and their complexes. PMID:22927377

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

Bae, Brian; Nayak, Dhananjaya; Ray, Ananya

RNA polymerase inhibitors like the CBR class that target the enzyme’s complex catalytic center are attractive leads for new antimicrobials. The catalysis by RNA polymerase involves multiple rearrangements of bridge helix, trigger loop, and active-center side chains that isomerize the triphosphate of bound NTP and two Mg 2+ ions from a preinsertion state to a reactive configuration. CBR inhibitors target a crevice between the N-terminal portion of the bridge helix and a surrounding cap region within which the bridge helix is thought to rearrange during the nucleotide addition cycle. Here, we report crystal structures of CBR inhibitor/Escherichia coli RNA polymerasemore » complexes as well as biochemical tests that establish two distinct effects of the inhibitors on the RNA polymerase catalytic site. One effect involves inhibition of trigger-loop folding via the F loop in the cap, which affects both nucleotide addition and hydrolysis of 3'-terminal dinucleotides in certain backtracked complexes. The second effect is trigger-loop independent, affects only nucleotide addition and pyrophosphorolysis, and may involve inhibition of bridge-helix movements that facilitate reactive triphosphate alignment.« less

Fretting and Corrosion Between a Metal Shell and Metal Liner May Explain the High Rate of Failure of R3 Modular Metal-on-Metal Hips.

PubMed

Ilo, Kevin C; Derby, Emma J; Whittaker, Robert K; Blunn, Gordon W; Skinner, John A; Hart, Alister J

2017-05-01

The R3 acetabular system used with its metal liner has higher revision rates when compared to its ceramic and polyethylene liner. In June 2012, the medical and healthcare products regulatory agency issued an alert regarding the metal liner of the R3 acetabular system. Six retrieved R3 acetabular systems with metal liners underwent detailed visual analysis using macroscopic and microscopic techniques. Visual analysis discovered corrosion on the backside of the metal liners. There was a distinct border to the areas of corrosion that conformed to antirotation tab insertions on the inner surface of the acetabular shell, which are for the polyethylene liner. Scanning electron microscopy indicated evidence of crevice corrosion, and energy-dispersive X-ray analysis confirmed corrosion debris rich in titanium. The high failure rate of the metal liner option of the R3 acetabular system may be attributed to corrosion on the backside of the liner which appear to result from geometry and design characteristics of the acetabular shell. Copyright © 2016 Elsevier Inc. All rights reserved.

Structure zone diagram and particle incorporation of nickel brush plated composite coatings

NASA Astrophysics Data System (ADS)

Isern, L.; Impey, S.; Almond, H.; Clouser, S. J.; Endrino, J. L.

2017-03-01

This work studies the deposition of aluminium-incorporated nickel coatings by brush electroplating, focusing on the electroplating setup and processing parameters. The setup was optimised in order to increase the volume of particle incorporation. The optimised design focused on increasing the plating solution flow to avoid sedimentation, and as a result the particle transport experienced a three-fold increase when compared with the traditional setup. The influence of bath load, current density and the brush material used was investigated. Both current density and brush material have a significant impact on the morphology and composition of the coatings. Higher current densities and non-abrasive brushes produce rough, particle-rich samples. Different combinations of these two parameters influence the surface characteristics differently, as illustrated in a Structure Zone Diagram. Finally, surfaces featuring crevices and peaks incorporate between 3.5 and 20 times more particles than smoother coatings. The presence of such features has been quantified using average surface roughness Ra and Abbott-Firestone curves. The combination of optimised setup and rough surface increased the particle content of the composite to 28 at.%.

Seasonal and Cyclical Changes in Genetic Composition of the Marine Intertidal Rock Pool Copepod Tigriopus brevicornis.

PubMed

Van Wormhoudt, Alain

2015-06-01

Tigriopus brevicornis is a marine rock pool copepod widely distributed along Atlantic coasts. Due to the absence of a known dispersal mechanism by free swimming stages, exchanges between populations over long distances are questionable. In order to analyse the evolution of an isolated supralittoral rock pool population, sampling of the copepod was performed monthly during 1 year and compared to samplings over 5 years in the same rock pool, as well as from other rock pools. Using ITS1 analysis, cyclical changes in genetic composition were detected. Our results give clear indications concerning the segregation of the rock pool population and a lack of gene flow among outside populations. A network analysis shows the presence of several shared dominant haplotypes and also singletons differing by one mutation point. F(st) analyses indicate that the main changes occur in autumn and winter. The few analogies of ITS1 sequences with nearby populations may indicate that new migrants must re-colonise the pools from surrounding rock crevices in the intertidal habitat where they may have found a refuge after bad weather conditions.

The role of habitat shift in the evolution of lizard morphology: evidence from tropical Tropidurus

PubMed Central

Vitt, Laurie J.; Caldwell, Janalee P.; Zani, Peter A.; Titus, Tom A.

1997-01-01

We compared morphology of two geographically close populations of the tropical lizard Tropidurus hispidus to test the hypothesis that habitat structure influences the evolution of morphology and ecology at the population level. T. hispidus isolated on a rock outcrop surrounded by tropical forest use rock crevices for refuge and appear dorsoventrally compressed compared with those in open savanna. A principal components analysis revealed that the populations were differentially distributed along an axis representing primarily three components of shape: body width, body height, and hind-leg length. Morphological divergence was supported by a principal components analysis of size-free morphological variables. Mitochondrial DNA sequences of ATPase 6 indicate that these populations are closely related relative to other T. hispidus, the rock outcrop morphology and ecology are derived within T. hispidus, and morphological and ecological divergence has occurred more rapidly than genetic divergence. This suggests that natural selection can rapidly adjust morphology and ecology in response to a recent history of exposure to habitats differing in structure, a result heretofore implied from comparative studies among lizard species. PMID:9108063

The role of habitat shift in the evolution of lizard morphology: evidence from tropical Tropidurus.

PubMed

Vitt, L J; Caldwell, J P; Zani, P A; Titus, T A

1997-04-15

We compared morphology of two geographically close populations of the tropical lizard Tropidurus hispidus to test the hypothesis that habitat structure influences the evolution of morphology and ecology at the population level. T. hispidus isolated on a rock outcrop surrounded by tropical forest use rock crevices for refuge and appear dorsoventrally compressed compared with those in open savanna. A principal components analysis revealed that the populations were differentially distributed along an axis representing primarily three components of shape: body width, body height, and hind-leg length. Morphological divergence was supported by a principal components analysis of size-free morphological variables. Mitochondrial DNA sequences of ATPase 6 indicate that these populations are closely related relative to other T. hispidus, the rock outcrop morphology and ecology are derived within T. hispidus, and morphological and ecological divergence has occurred more rapidly than genetic divergence. This suggests that natural selection can rapidly adjust morphology and ecology in response to a recent history of exposure to habitats differing in structure, a result heretofore implied from comparative studies among lizard species.

Fifty million years of herbivory on coral reefs: fossils, fish and functional innovations.

PubMed

Bellwood, D R; Goatley, C H R; Brandl, S J; Bellwood, O

2014-04-22

The evolution of ecological processes on coral reefs was examined based on Eocene fossil fishes from Monte Bolca, Italy and extant species from the Great Barrier Reef, Australia. Using ecologically relevant morphological metrics, we investigated the evolution of herbivory in surgeonfishes (Acanthuridae) and rabbitfishes (Siganidae). Eocene and Recent surgeonfishes showed remarkable similarities, with grazers, browsers and even specialized, long-snouted forms having Eocene analogues. These long-snouted Eocene species were probably pair-forming, crevice-feeding forms like their Recent counterparts. Although Eocene surgeonfishes likely played a critical role as herbivores during the origins of modern coral reefs, they lacked the novel morphologies seen in modern Acanthurus and Siganus (including eyes positioned high above their low-set mouths). Today, these forms dominate coral reefs in both abundance and species richness and are associated with feeding on shallow, exposed algal turfs. The radiation of these new forms, and their expansion into new habitats in the Oligocene-Miocene, reflects the second phase in the development of fish herbivory on coral reefs that is closely associated with the exploitation of highly productive short algal turfs.

Structure zone diagram and particle incorporation of nickel brush plated composite coatings.

PubMed

Isern, L; Impey, S; Almond, H; Clouser, S J; Endrino, J L

2017-03-16

This work studies the deposition of aluminium-incorporated nickel coatings by brush electroplating, focusing on the electroplating setup and processing parameters. The setup was optimised in order to increase the volume of particle incorporation. The optimised design focused on increasing the plating solution flow to avoid sedimentation, and as a result the particle transport experienced a three-fold increase when compared with the traditional setup. The influence of bath load, current density and the brush material used was investigated. Both current density and brush material have a significant impact on the morphology and composition of the coatings. Higher current densities and non-abrasive brushes produce rough, particle-rich samples. Different combinations of these two parameters influence the surface characteristics differently, as illustrated in a Structure Zone Diagram. Finally, surfaces featuring crevices and peaks incorporate between 3.5 and 20 times more particles than smoother coatings. The presence of such features has been quantified using average surface roughness Ra and Abbott-Firestone curves. The combination of optimised setup and rough surface increased the particle content of the composite to 28 at.%.

Effects of Invasive European Fire Ants (Myrmica rubra) on Herring Gull (Larus argentatus) Reproduction

PubMed Central

DeFisher, Luke E.; Bonter, David N.

2013-01-01

Various invasive ant species have negatively affected reproductive success in birds by disrupting nest site selection, incubation patterns, food supply, and by direct predation on nestlings. Impacts can be particularly severe when non-native ants colonize seabird nesting islands where thousands of birds may nest in high densities on the ground or in burrows or crevices. Here we report on the first documented effects of Myrmica rubra, the European fire ant, on the reproduction of birds in its non-native range. We documented herring gulls (Larus argentatus) on Appledore Island, Maine, engaging in more erratic incubation behaviors at nests infested by the ants. Newly-hatched chicks in some nests were swarmed by ants, leading to rapid chick death. Due to high overall rates of chick mortality, survival probabilities did not vary between nests with and without ant activity, however chick growth rates were slower at nests with ants than at ant-free nests. Ant infestation likely leads to longer-term fitness consequences because slower growth rates early in life may ultimately lead to lower post-fledging survival probabilities. PMID:23691168

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

Unneberg, L.

The main features of the 16 core grids (top guides) designed by ABB ATOM AB are briefly described and the evolution of the design is discussed. One important characteristic of the first nine grids is the existence of bolts securing guide bars to the core grid plates. These bolts are made of precipitation hardened or solution annealed stainless steel. During operation, bolts in all none grids have cracked. The failure analyses indicate that intergranular stress corrosion cracking (IGSCC), possibly accelerated by crevice conditions and/or irradiation, was the cause of failure. Fast neutron fluences approaching or exceeding the levels considered asmore » critical for irradiation assisted stress corrosion cracking (IASCC) will be reached in a few cases only. Temporary measures were taken immediately after the discovery of the cracking. For five of the nine reactors affected, it was decided to replace the complete grids. Two of these replacements have been successfully carried out to date. IASCC as a potential future problem is discussed and it is pointed out that, during their life times, the ABB ATOM core grids will be exposed to sufficiently high fast neutron fluences to cause some concern.« less

40 CFR 53.22 - Generation of test atmospheres.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 6 2012-07-01 2012-07-01 false Generation of test atmospheres. 53.22... Characteristics of Automated Methods for SO2, CO, O3, and NO2 § 53.22 Generation of test atmospheres. (a) Table B-2 to subpart B of part 53 specifies preferred methods for generating test atmospheres and suggested...

40 CFR 53.22 - Generation of test atmospheres.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 6 2014-07-01 2014-07-01 false Generation of test atmospheres. 53.22... Characteristics of Automated Methods for SO2, CO, O3, and NO2 § 53.22 Generation of test atmospheres. (a) Table B-2 to subpart B of part 53 specifies preferred methods for generating test atmospheres and suggested...

40 CFR 53.22 - Generation of test atmospheres.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 6 2013-07-01 2013-07-01 false Generation of test atmospheres. 53.22... Characteristics of Automated Methods for SO2, CO, O3, and NO2 § 53.22 Generation of test atmospheres. (a) Table B-2 to subpart B of part 53 specifies preferred methods for generating test atmospheres and suggested...

Effective Training for Millennial Students

ERIC Educational Resources Information Center

Werth, Eric P.; Werth, Loredana

2011-01-01

A generational shift is occurring in training environments worldwide, a shift that promises to bring with it a dramatic and long-lasting impact. Just as years ago, those of the Baby Boomer generation passed the torch to Generation X, today the process is starting anew with Generation X and those who have come to be known as the Millennials.…

Hazardous Waste Generators

EPA Pesticide Factsheets

Many industries generate hazardous waste. EPA regulates hazardous waste under the Resource Conservation and Recovery Act to ensure these wastes are managed in ways that are protective of human health and the environment.

Innovating Training through Immersive Environments: Generation Y, Exploratory Learning, and Serious Games

NASA Technical Reports Server (NTRS)

Gendron, Gerald

2012-01-01

Over the next decade, those entering Service and Joint Staff positions within the military will come from a different generation than the current leadership. They will come from Generation Y and have differing preferences for learning. Immersive learning environments like serious games and virtual world initiatives can complement traditional training methods to provide a better overall training program for staffs. Generation Y members desire learning methods which are relevant and interactive, regardless of whether they are delivered over the internet or in person. This paper focuses on a project undertaken to assess alternative training methods to teach special operations staffs. It provides a summary of the needs analysis used to consider alternatives and to better posture the Department of Defense for future training development.

Characteristics of electromagnetic interference generated by arc discharges. [in spacecraft

NASA Technical Reports Server (NTRS)

Leung, Philip

1986-01-01

Electromagnetic interference (EMI) signatures resulting from arc discharges are characterized, and the effects of electrostatic discharges (ESDs) on the design of spacecraft systems are investigated. EMI characterization experiments were performed on Mylar, Teflon, Kapton, fused silica, and fiberglass in a vacuum chamber with acrylic walls; the experimental design and procedures are described. Discharge current pulses and RF spectra generated by the sample materials are examined. The relation between the magnitude of EMI generated during an ESD event and the material, environment, and geometry is studied. The solar-array/plasma interaction is analyzed; particular attention is given to the rate of discharge as a function of plasma density. The physical mechanisms of ESD-generated EMI are discussed. The data reveal that ESD parameters are dependent on the test environment.

Effects of Early Literacy Environments on the Reading Attitudes, Behaviours and Values of Veteran Teachers

ERIC Educational Resources Information Center

Levitt, Roberta; Red Owl, R. H.

2013-01-01

Research has linked early literacy environments to the attitudes, behaviours and instructional values of reading teachers, but most prior research has addressed preservice or early inservice teachers. This mixed-methods, hypothesis-generating, "Q" methodology-based study explored the relationship between early literacy environments and…

A Virtual Education: Guidelines for Using Games Technology

ERIC Educational Resources Information Center

Schofield, Damian

2014-01-01

Advanced three-dimensional virtual environment technology, similar to that used by the film and computer games industry, can allow educational developers to rapidly create realistic online vir-tual environments. This technology has been used to generate a range of interactive Virtual Real-ity (VR) learning environments across a spectrum of…

Teaching Millennials to Engage THE Environment Instead of Their Environment: A Pedagogical Analysis

ERIC Educational Resources Information Center

Stevens, J. Richard; Crow, Deserai Anderson

2016-01-01

This article examines the difficulty in teaching contemporary students of journalism (those in the much-discussed Millennial Generation) to report on complex topics like science and the environment. After examining contemporary literature, the authors subjected 120 undergraduate students to a strategy that combined visual representations of…

Evolutionarily stable learning schedules and cumulative culture in discrete generation models.

PubMed

Aoki, Kenichi; Wakano, Joe Yuichiro; Lehmann, Laurent

2012-06-01

Individual learning (e.g., trial-and-error) and social learning (e.g., imitation) are alternative ways of acquiring and expressing the appropriate phenotype in an environment. The optimal choice between using individual learning and/or social learning may be dictated by the life-stage or age of an organism. Of special interest is a learning schedule in which social learning precedes individual learning, because such a schedule is apparently a necessary condition for cumulative culture. Assuming two obligatory learning stages per discrete generation, we obtain the evolutionarily stable learning schedules for the three situations where the environment is constant, fluctuates between generations, or fluctuates within generations. During each learning stage, we assume that an organism may target the optimal phenotype in the current environment by individual learning, and/or the mature phenotype of the previous generation by oblique social learning. In the absence of exogenous costs to learning, the evolutionarily stable learning schedules are predicted to be either pure social learning followed by pure individual learning ("bang-bang" control) or pure individual learning at both stages ("flat" control). Moreover, we find for each situation that the evolutionarily stable learning schedule is also the one that optimizes the learned phenotype at equilibrium. Copyright © 2012 Elsevier Inc. All rights reserved.

Speed breeding is a powerful tool to accelerate crop research and breeding.

PubMed

Watson, Amy; Ghosh, Sreya; Williams, Matthew J; Cuddy, William S; Simmonds, James; Rey, María-Dolores; Asyraf Md Hatta, M; Hinchliffe, Alison; Steed, Andrew; Reynolds, Daniel; Adamski, Nikolai M; Breakspear, Andy; Korolev, Andrey; Rayner, Tracey; Dixon, Laura E; Riaz, Adnan; Martin, William; Ryan, Merrill; Edwards, David; Batley, Jacqueline; Raman, Harsh; Carter, Jeremy; Rogers, Christian; Domoney, Claire; Moore, Graham; Harwood, Wendy; Nicholson, Paul; Dieters, Mark J; DeLacy, Ian H; Zhou, Ji; Uauy, Cristobal; Boden, Scott A; Park, Robert F; Wulff, Brande B H; Hickey, Lee T

2018-01-01

The growing human population and a changing environment have raised significant concern for global food security, with the current improvement rate of several important crops inadequate to meet future demand 1 . This slow improvement rate is attributed partly to the long generation times of crop plants. Here, we present a method called 'speed breeding', which greatly shortens generation time and accelerates breeding and research programmes. Speed breeding can be used to achieve up to 6 generations per year for spring wheat (Triticum aestivum), durum wheat (T. durum), barley (Hordeum vulgare), chickpea (Cicer arietinum) and pea (Pisum sativum), and 4 generations for canola (Brassica napus), instead of 2-3 under normal glasshouse conditions. We demonstrate that speed breeding in fully enclosed, controlled-environment growth chambers can accelerate plant development for research purposes, including phenotyping of adult plant traits, mutant studies and transformation. The use of supplemental lighting in a glasshouse environment allows rapid generation cycling through single seed descent (SSD) and potential for adaptation to larger-scale crop improvement programs. Cost saving through light-emitting diode (LED) supplemental lighting is also outlined. We envisage great potential for integrating speed breeding with other modern crop breeding technologies, including high-throughput genotyping, genome editing and genomic selection, accelerating the rate of crop improvement.

Adaptation to Temporally Fluctuating Environments by the Evolution of Maternal Effects.

PubMed

Dey, Snigdhadip; Proulx, Stephen R; Teotónio, Henrique

2016-02-01

All organisms live in temporally fluctuating environments. Theory predicts that the evolution of deterministic maternal effects (i.e., anticipatory maternal effects or transgenerational phenotypic plasticity) underlies adaptation to environments that fluctuate in a predictably alternating fashion over maternal-offspring generations. In contrast, randomizing maternal effects (i.e., diversifying and conservative bet-hedging), are expected to evolve in response to unpredictably fluctuating environments. Although maternal effects are common, evidence for their adaptive significance is equivocal since they can easily evolve as a correlated response to maternal selection and may or may not increase the future fitness of offspring. Using the hermaphroditic nematode Caenorhabditis elegans, we here show that the experimental evolution of maternal glycogen provisioning underlies adaptation to a fluctuating normoxia-anoxia hatching environment by increasing embryo survival under anoxia. In strictly alternating environments, we found that hermaphrodites evolved the ability to increase embryo glycogen provisioning when they experienced normoxia and to decrease embryo glycogen provisioning when they experienced anoxia. At odds with existing theory, however, populations facing irregularly fluctuating normoxia-anoxia hatching environments failed to evolve randomizing maternal effects. Instead, adaptation in these populations may have occurred through the evolution of fitness effects that percolate over multiple generations, as they maintained considerably high expected growth rates during experimental evolution despite evolving reduced fecundity and reduced embryo survival under one or two generations of anoxia. We develop theoretical models that explain why adaptation to a wide range of patterns of environmental fluctuations hinges on the existence of deterministic maternal effects, and that such deterministic maternal effects are more likely to contribute to adaptation than randomizing maternal effects.

Adaptation to Temporally Fluctuating Environments by the Evolution of Maternal Effects

PubMed Central

Dey, Snigdhadip; Proulx, Stephen R.; Teotónio, Henrique

2016-01-01

All organisms live in temporally fluctuating environments. Theory predicts that the evolution of deterministic maternal effects (i.e., anticipatory maternal effects or transgenerational phenotypic plasticity) underlies adaptation to environments that fluctuate in a predictably alternating fashion over maternal-offspring generations. In contrast, randomizing maternal effects (i.e., diversifying and conservative bet-hedging), are expected to evolve in response to unpredictably fluctuating environments. Although maternal effects are common, evidence for their adaptive significance is equivocal since they can easily evolve as a correlated response to maternal selection and may or may not increase the future fitness of offspring. Using the hermaphroditic nematode Caenorhabditis elegans, we here show that the experimental evolution of maternal glycogen provisioning underlies adaptation to a fluctuating normoxia–anoxia hatching environment by increasing embryo survival under anoxia. In strictly alternating environments, we found that hermaphrodites evolved the ability to increase embryo glycogen provisioning when they experienced normoxia and to decrease embryo glycogen provisioning when they experienced anoxia. At odds with existing theory, however, populations facing irregularly fluctuating normoxia–anoxia hatching environments failed to evolve randomizing maternal effects. Instead, adaptation in these populations may have occurred through the evolution of fitness effects that percolate over multiple generations, as they maintained considerably high expected growth rates during experimental evolution despite evolving reduced fecundity and reduced embryo survival under one or two generations of anoxia. We develop theoretical models that explain why adaptation to a wide range of patterns of environmental fluctuations hinges on the existence of deterministic maternal effects, and that such deterministic maternal effects are more likely to contribute to adaptation than randomizing maternal effects. PMID:26910440

"Chasing a Passion": First-Generation College Graduates at Work

ERIC Educational Resources Information Center

Olson, Joann S.

2016-01-01

Purpose: The purpose of this paper is to describe the college-to-work transition as experienced by first-generation college (FGC) graduates. First-generation graduates are often adjusting to workplaces that are significantly different from parents' work environments. Design/methodology/approach: This phenomenological study explored the…

An Overview of NASA's Integrated Design and Engineering Analysis (IDEA) Environment

NASA Technical Reports Server (NTRS)

Robinson, Jeffrey S.

2011-01-01

Historically, the design of subsonic and supersonic aircraft has been divided into separate technical disciplines (such as propulsion, aerodynamics and structures), each of which performs design and analysis in relative isolation from others. This is possible, in most cases, either because the amount of interdisciplinary coupling is minimal, or because the interactions can be treated as linear. The design of hypersonic airbreathing vehicles, like NASA's X-43, is quite the opposite. Such systems are dominated by strong non-linear interactions between disciplines. The design of these systems demands that a multi-disciplinary approach be taken. Furthermore, increased analytical fidelity at the conceptual design phase is highly desirable, as many of the non-linearities are not captured by lower fidelity tools. Only when these systems are designed from a true multi-disciplinary perspective, can the real performance benefits be achieved and complete vehicle systems be fielded. Toward this end, the Vehicle Analysis Branch at NASA Langley Research Center has been developing the Integrated Design and Engineering Analysis (IDEA) Environment. IDEA is a collaborative environment for parametrically modeling conceptual and preliminary designs for launch vehicle and high speed atmospheric flight configurations using the Adaptive Modeling Language (AML) as the underlying framework. The environment integrates geometry, packaging, propulsion, trajectory, aerodynamics, aerothermodynamics, engine and airframe subsystem design, thermal and structural analysis, and vehicle closure into a generative, parametric, unified computational model where data is shared seamlessly between the different disciplines. Plans are also in place to incorporate life cycle analysis tools into the environment which will estimate vehicle operability, reliability and cost. IDEA is currently being funded by NASA?s Hypersonics Project, a part of the Fundamental Aeronautics Program within the Aeronautics Research Mission Directorate. The environment is currently focused around a two-stage-to-orbit configuration with a turbine-based combined cycle (TBCC) first stage and a reusable rocket second stage. IDEA will be rolled out in generations, with each successive generation providing a significant increase in capability, either through increased analytic fidelity, expansion of vehicle classes considered, or by the inclusion of advanced modeling techniques. This paper provides the motivation behind the current effort, an overview of the development of the IDEA environment (including the contents and capabilities to be included in Generation 1 and Generation 2), and a description of the current status and detail of future plans.

Spontaneously Generating Life in Your Classroom? Pasteur, Spallanzani and Science Process.

ERIC Educational Resources Information Center

Byington, Scott

2001-01-01

Presents an experiment that tests for spontaneous generation, or abiogenesis. Observes microbial growth in nutrient broth under seven different flask environments. Includes instructions for the methods. (YDS)

40 CFR 761.64 - Disposal of wastes generated as a result of research and development activities authorized under...

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Disposal of wastes generated as a..., AND USE PROHIBITIONS Storage and Disposal § 761.64 Disposal of wastes generated as a result of... section provides disposal requirements for wastes generated during and as a result of research and...

40 CFR 761.64 - Disposal of wastes generated as a result of research and development activities authorized under...

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Disposal of wastes generated as a..., AND USE PROHIBITIONS Storage and Disposal § 761.64 Disposal of wastes generated as a result of... section provides disposal requirements for wastes generated during and as a result of research and...

40 CFR 761.64 - Disposal of wastes generated as a result of research and development activities authorized under...

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Disposal of wastes generated as a..., AND USE PROHIBITIONS Storage and Disposal § 761.64 Disposal of wastes generated as a result of... section provides disposal requirements for wastes generated during and as a result of research and...

40 CFR 761.64 - Disposal of wastes generated as a result of research and development activities authorized under...

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Disposal of wastes generated as a..., AND USE PROHIBITIONS Storage and Disposal § 761.64 Disposal of wastes generated as a result of... section provides disposal requirements for wastes generated during and as a result of research and...

Reconfigurable Image Generator

NASA Technical Reports Server (NTRS)

Archdeacon, John L. (Inventor); Iwai, Nelson H. (Inventor); Kato, Kenji H. (Inventor); Sweet, Barbara T. (Inventor)

2017-01-01

A RiG may simulate visual conditions of a real world environment, and generate the necessary amount of pixels in a visual simulation at rates up to 120 frames per second. RiG may also include a database generation system capable of producing visual databases suitable to drive the visual fidelity required by the RiG.

Engaging the Millennial Generation in Class Discussions

ERIC Educational Resources Information Center

Roehling, Patricia Vincent; Vander Kooi, Thomas Lee; Dykema, Stephanie; Quisenberry, Brooke; Vandlen, Chelsea

2011-01-01

Students in the Millennial Generation (late 20s and younger) have been raised in an environment in which individuality is highly valued and information, entertainment, and social interactions are unlimited and at their fingertips. As a result, these students may have different educational expectations and needs than previous generations. Class…

Computer-Generated, Three-Dimensional Character Animation: A Report and Analysis.

ERIC Educational Resources Information Center

Kingsbury, Douglas Lee

This master's thesis details the experience gathered in the production "Snoot and Muttly," a short character animation with 3-D computer generated images, and provides an analysis of the computer-generated 3-D character animation system capabilities. Descriptions are provided of the animation environment at the Ohio State University…

Intergenerational Continuity in High-Conflict Family Environments: Investigating a Mediating Depressive Pathway

ERIC Educational Resources Information Center

Rothenberg, W. Andrew; Hussong, Andrea M.; Chassin, Laurie

2018-01-01

Emerging evidence suggests that family conflict shows continuity across generations and that intergenerational family conflict can be more intense and deleterious than conflict experienced in a single generation. However, few investigations have identified etiological mechanisms by which family conflict is perpetuated across generations.…

SRG110 Stirling Generator Dynamic Simulator Vibration Test Results and Analysis Correlation

NASA Technical Reports Server (NTRS)

Suarez, Vicente J.; Lewandowski, Edward J.; Callahan, John

2006-01-01

The U.S. Department of Energy (DOE), Lockheed Martin (LM), and NASA Glenn Research Center (GRC) have been developing the Stirling Radioisotope Generator (SRG110) for use as a power system for space science missions. The launch environment enveloping potential missions results in a random input spectrum that is significantly higher than historical RPS launch levels and is a challenge for designers. Analysis presented in prior work predicted that tailoring the compliance at the generator-spacecraft interface reduced the dynamic response of the system thereby allowing higher launch load input levels and expanding the range of potential generator missions. To confirm analytical predictions, a dynamic simulator representing the generator structure, Stirling convertors and heat sources was designed and built for testing with and without a compliant interface. Finite element analysis was performed to guide the generator simulator and compliant interface design so that test modes and frequencies were representative of the SRG110 generator. This paper presents the dynamic simulator design, the test setup and methodology, test article modes and frequencies and dynamic responses, and post-test analysis results. With the compliant interface, component responses to an input environment exceeding the SRG110 qualification level spectrum were all within design allowables. Post-test analysis included finite element model tuning to match test frequencies and random response analysis using the test input spectrum. Analytical results were in good overall agreement with the test results and confirmed previous predictions that the SRG110 power system may be considered for a broad range of potential missions, including those with demanding launch environments.

SRG110 Stirling Generator Dynamic Simulator Vibration Test Results and Analysis Correlation

NASA Technical Reports Server (NTRS)

Lewandowski, Edward J.; Suarez, Vicente J.; Goodnight, Thomas W.; Callahan, John

2007-01-01

The U.S. Department of Energy (DOE), Lockheed Martin (LM), and NASA Glenn Research Center (GRC) have been developing the Stirling Radioisotope Generator (SRG110) for use as a power system for space science missions. The launch environment enveloping potential missions results in a random input spectrum that is significantly higher than historical radioisotope power system (RPS) launch levels and is a challenge for designers. Analysis presented in prior work predicted that tailoring the compliance at the generator-spacecraft interface reduced the dynamic response of the system thereby allowing higher launch load input levels and expanding the range of potential generator missions. To confirm analytical predictions, a dynamic simulator representing the generator structure, Stirling convertors and heat sources were designed and built for testing with and without a compliant interface. Finite element analysis was performed to guide the generator simulator and compliant interface design so that test modes and frequencies were representative of the SRG110 generator. This paper presents the dynamic simulator design, the test setup and methodology, test article modes and frequencies and dynamic responses, and post-test analysis results. With the compliant interface, component responses to an input environment exceeding the SRG110 qualification level spectrum were all within design allowables. Post-test analysis included finite element model tuning to match test frequencies and random response analysis using the test input spectrum. Analytical results were in good overall agreement with the test results and confirmed previous predictions that the SRG110 power system may be considered for a broad range of potential missions, including those with demanding launch environments.

Virtual Environments Supporting Learning and Communication in Special Needs Education

ERIC Educational Resources Information Center

Cobb, Sue V. G.

2007-01-01

Virtual reality (VR) describes a set of technologies that allow users to explore and experience 3-dimensional computer-generated "worlds" or "environments." These virtual environments can contain representations of real or imaginary objects on a small or large scale (from modeling of molecular structures to buildings, streets, and scenery of a…

Virtual Virtuosos: A Case Study in Learning Music in Virtual Learning Environments in Spain

ERIC Educational Resources Information Center

Alberich-Artal, Enric; Sangra, Albert

2012-01-01

In recent years, the development of Information and Communication Technologies (ICT) has contributed to the generation of a number of interesting initiatives in the field of music education and training in virtual learning environments. However, music education initiatives employing virtual learning environments have replicated and perpetuated the…