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1

In-air fluence profiles and water depth dose for uncollimated electron beams  

PubMed Central

Advanced electron beam dose calculation models for radiation treatment planning systems require the input of a phase space beam model to configure a clinical electron beam in a computer. This beam model is a distribution in position, energy, and direction of electrons and photons in a plane in front of the patient. The phase space beam model can be determined by Monte Carlo simulation of the treatment head or from a limited set of measurements. In the latter case, parameters of the electron phase space beam model are obtained by fitting measured to calculated dosimetric data. In the present work, data for air fluence profiles and water depth doses have been presented for electron beams without an applicator for a medical linear accelerator. These data are used to parameterize the electron phase space beam model to a Monte Carlo dose calculation module available in the first commercial (MDS Nordion, now Nucletron) Monte Carlo treatment planning for electron beams.

Toutaoui, Abedelkadar; Aichouche, Amar Nassim; Adjidir, Kenza Adjidir; Chami, Ahmed Chafik

2008-01-01

2

Calculated depth-dose distributions for H+ and He+ beams in liquid water  

NASA Astrophysics Data System (ADS)

We have calculated the dose distribution delivered by proton and helium beams in liquid water as a function of the target-depth, for incident energies in the range 0.5-10 MeV/u. The motion of the projectiles through the stopping medium is simulated by a code that combines Monte Carlo and a finite differences algorithm to consider the electronic stopping power, evaluated in the dielectric framework, and the multiple nuclear scattering with the target nuclei. Changes in projectile charge-state are taken into account dynamically as it moves through the target. We use the MELF-GOS model to describe the energy loss function of liquid water, obtaining a value of 79.4 eV for its mean excitation energy. Our calculated stopping powers and depth-dose distributions are compared with those obtained using other methods to describe the energy loss function of liquid water, such as the extended Drude and the Penn models, as well as with the prediction of the SRIM code and the tables of ICRU.

Garcia-Molina, Rafael; Abril, Isabel; Denton, Cristian D.; Heredia-Avalos, Santiago; Kyriakou, Ioanna; Emfietzoglou, Dimitris

2009-08-01

3

Practical methods of electron depth-dose measurement compared to use of the NACP design chamber in water  

Microsoft Academic Search

Central axis relative dose versus depth measurements were performed using two different small volume thimble ionization chambers and a p-type silicon diode in a water phantom and with two parallel-plate ionization chambers, thermoluminescent dosimeters, and radiographic film in a popular clear polystyrene phantom. Values obtained were compared to the results of similar measurements in a water phantom performed with a

Randall K. Ten Haken; B. A. Fraass; R. J. Jost

1987-01-01

4

The LNE-LNHB water calorimeter for primary measurement of absorbed dose at low depth in water: application to medium-energy x-rays  

NASA Astrophysics Data System (ADS)

Water calorimeters are used to establish absorbed dose standards in several national metrology laboratories involved in ionizing radiation dosimetry. These calorimeters have been first used in high-energy photons of 60Co or accelerator beams, where the depth of measurement in water is large (5 or 10 cm). The LNE-LNHB laboratory has developed a specific calorimeter which makes measurements at low depth in water (down to 0.5 cm) easier, in order to fulfil the reference conditions required by the international dosimetry protocols for medium-energy x-rays. This new calorimeter was first used to measure the absorbed dose rate in water at a depth of 2 cm for six medium-energy x-ray reference beams with a tube potential from 80 to 300 kV. The relative combined standard uncertainty obtained on the absorbed dose rate to water is lower than 0.8%. An overview of the design of the calorimeter is given, followed by a detailed description of the calculation of the correction factors and the calorimetric measurements.

Rapp, B.; Perichon, N.; Denoziere, M.; Daures, J.; Ostrowsky, A.; Bordy, J.-M.

2013-05-01

5

Absolute depth-dose-rate measurements for an {sup 192}Ir HDR brachytherapy source in water using MOSFET detectors  

SciTech Connect

Reported MOSFET measurements concern mostly external radiotherapy and in vivo dosimetry. In this paper, we apply the technique for absolute dosimetry in the context of HDR brachytherapy using an {sup 192}Ir source. Measured radial dose rate distributions in water for different planes perpendicular to the source axis are presented and special attention is paid to the calibration of the R and K type detectors, and to the determination of appropriate correction factors for the sensitivity variation with the increase of the threshold voltage and the energy dependence. The experimental results are compared with Monte Carlo simulated dose rate distributions. The experimental results show a good agreement with the Monte Carlo simulations: the discrepancy between experimental and Monte Carlo results being within 5% for 82% of the points and within 10% for 95% of the points. Moreover, all points except two are found to lie within the experimental uncertainties, confirming thereby the quality of the results obtained.

Zilio, Valery Olivier; Joneja, Om Parkash; Popowski, Youri; Rosenfeld, Anatoly; Chawla, Rakesh [Ecole Polytechnique Federale de Lausanne (EPFL), Laboratoire de Physique des Reacteurs et de Comportement des Systemes, CH-1015, Lausanne (Switzerland); Ecole Polytechnique Federale de Lausanne (EPFL), Laboratoire de Physique des Reacteurs et de Comportement des Systemes, CH-1015, Lausanne, Switzerland and Paul Scherrer Institute (PSI), Laboratory of Reactor Physics and Systems Behaviour, CH-5232 Villigen (Switzerland); Radio-oncology Division, University of Geneva Hospital, CH-1211, Geneva (Switzerland); Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, 2522 Australia (Australia); Ecole Polytechnique Federale de Lausanne (EPFL), Laboratoire de Physique des Reacteurs et de Comportement des Systemes, CH-1015, Lausanne, Switzerland and Paul Scherrer Institute (PSI), Laboratory of Reactor Physics and Systems Behaviour, CH-5232 Villigen (Switzerland)

2006-06-15

6

Variability of water content and of depth profiles of global fallout 137Cs in grassland soils and the resulting external gamma-dose rates.  

PubMed

137Cs from global fallout of nuclear weapon testings in the 1950s and 1960s was determined in successive layers (0-30 cm) of eight undisturbed grassland soils in Bavaria, Germany. The maximum activity concentration was found in soil layers between 4 and 15 cm below the surface. Using the vertical distribution of the cesium activity, which varied considerably from site to site, the mean residence half-time of 137Cs from global fallout in each soil layer was evaluated with a compartment model. These values ranged from 1.0 to 6.3 years/cm. The mean residence half-time averaged over all soil layers and all sites was 2.7 +/- 1.4 years/cm and, thus, about twice the corresponding residence half-time of the Chernobyl-derived 137Cs as determined in the same soil layers (also in 1993). The dose rate of the external gamma-radiation due to 137Cs from global fallout in the soil determined from the depth distributions varied between 0.34 and 0.57 (mean: 0.45 +/- 0.07) nGy/h per kBq/m2. The effect of soil water content on the dose rate was studied by considering four states of the soil, from water content zero to complete water saturation of the total pore volume. It was shown that the difference between the dose rates at the permanent wilting point and the field capacity, which both represent the most relevant water contents of soils, was only 10% of the dose rate at the permanent wilting point for all sites. PMID:9615340

Schimmack, W; Steindl, H; Bunzl, K

1998-04-01

7

Percentage depth doses for high energy X-rays  

Microsoft Academic Search

Percentage depth doses for 34 MV betatron X-rays were measured ionometrically for a number of square fields of side 5-20 cm. Significant differences in the depth doses for different field sizes were found in the build-up region and in the depth of maximum dose. A systematic change with depth was also indicated in the exponential region of these curves. These

D J Dawson

1976-01-01

8

Technology opens new water depth limits  

Microsoft Academic Search

This article reports on technology that has increased the water depth limits of deep water drilling. Riser-handling systems, deep-water tools, subsea stacks and marine risers have contributed to the development of technology of drilling at increased depths. Technological innovations have increased drilling depths to 10,000-13,000 feet, where drilling depth limits used to be 10,000-13,000 feet. The article also discusses the

1982-01-01

9

Technology opens new water depth limits  

SciTech Connect

This article reports on technology that has increased the water depth limits of deep water drilling. Riser-handling systems, deep-water tools, subsea stacks and marine risers have contributed to the development of technology of drilling at increased depths. Technological innovations have increased drilling depths to 10,000-13,000 feet, where drilling depth limits used to be 10,000-13,000 feet. The article also discusses the necessity of increasing technology for deepwater drilling; sighting higher operator costs, the importance of deepwater drilling at increased depths is discussed.

Smith, G.D.

1982-06-05

10

TECHNICAL NOTE: Parametrisation of depth dose for electron beams  

Microsoft Academic Search

Knowledge of the central axis depth dose curve is essential for the development of an accurate electron beam treatment planning system. The equation introduced by Kawachi (1975) and modified by Steben et al. (1976) gave general agreement with experimental data but it required a complex set of equations to extract the central axis depth dose. Even though interpolation of experimental

A. S. Meigooni; I. J. Das

1987-01-01

11

Comparison of EGS4 and MCNP Monte Carlo codes when calculating radiotherapy depth doses  

NASA Astrophysics Data System (ADS)

The Monte Carlo codes EGS4 and MCNP have been compared when calculating radiotherapy depth doses in water. The aims of the work were to study (i) the differences between calculated depth doses in water for a range of monoenergetic photon energies and (ii) the relative efficiency of the two codes for different electron transport energy cut-offs. The depth doses from the two codes agree with each other within the statistical uncertainties of the calculations (1-2%). The relative depth doses also agree with data tabulated in the British Journal of Radiology Supplement 25. A discrepancy in the dose build-up region may by attributed to the different electron transport algorithims used by EGS4 and MCNP. This discrepancy is considerably reduced when the improved electron transport routines are used in the latest (4B) version of MCNP. Timing calculations show that EGS4 is at least 50% faster than MCNP for the geometries used in the simulations.

Love, P. A.; Lewis, D. G.; Al-Affan, I. A. M.; Smith, C. W.

1998-05-01

12

Depth of ionization chamber in water  

Microsoft Academic Search

The device developed by the authors and described here enables the user to measure the depth from the water surface to the point of measurement for a cylindrical ion chamber with a waterproof plastic cap in a water phantom, free of surface-tension error with a high precision. The device seeks vertical orientation and provides the convenience of hands-free operation. The

R. C. Tailor; V. M. Tello

1995-01-01

13

Depth of ionization chamber in water.  

PubMed

The device developed by the authors and described here enables the user to measure the depth from the water surface to the point of measurement for a cylindrical ion chamber with a waterproof plastic cap in a water phantom, free of surface-tension error with a high precision. The device seeks vertical orientation and provides the convenience of hands-free operation. The measurement process is simple and quick with a precision of 0.1 mm. (The device is currently available as a 'water phantom depth gauge' from Nuclear Associates, Division of Victoreen Inc., Clare Place, NY, USA.) PMID:7480120

Tailor, R C; Tello, V M

1995-08-01

14

High-energy neutron depth-dose distribution experiment.  

PubMed

A unique set of high-energy neutron depth-dose benchmark experiments were performed at the Los Alamos Neutron Science Center/Weapons Neutron Research (LANSCE/WNR) complex. The experiments consisted of filtered neutron beams with energies up to 800 MeV impinging on a 30 x 30 x 30 cm3 liquid, tissue-equivalent phantom. The absorbed dose was measured in the phantom at various depths with tissue-equivalent ion chambers. This experiment is intended to serve as a benchmark experiment for the testing of high-energy radiation transport codes for the international radiation protection community. PMID:14756177

Ferenci, M S; Hertel, N E

2003-01-01

15

Anchoring International sets new water depth record  

SciTech Connect

Santa Barbara Channel has a history steeped in firsts in techniques for the production of offshore oil. Landscaped drilling and production islands, production piers, and directional drilling from land rigs to production under the channel, to name a few. The latest such project was handled by Anchoring International, Inc., a pipe line anchoring company headquartered in Houston, Texas. Contracted by Healy Tibbets Construction Company, prime contractor, Anchoring was commissioned to handle a new deep water record breaking anchoring job. The job was to anchor J-tube extensions in 820 feet of water--the deepest pipe line anchoring job ever undertaken. In most shallow water pipe line anchoring jobs, anchors and anchor installation unit placement over the pipe line is handled from a crane topside with visual assist from divers. However, due to the extreme depth of this project, the installation unit with anchors had to be modified for submersible operator-assisted placement capability. Anchoring International handled the anchor design and installation equipment, and submersible operator assistance was furnished by Oceaneering, International. WASP and JIM atmospheric diving systems were used. All ocean bottom activities were monitored topside with the JERED video-equipped remote controlled vehicle. Since the weight of the anchor sets and power installation unit are minimum, the entire operation was conducted from a small boat sufficient to carry dive equipment and the anchor installation unit power supply. A small pedestal crane was used to lower and retrieve the anchor installation unit.

Noble, H.J.

1983-07-01

16

Initial beam size study for passive scatter proton therapy. II. Changes in delivered depth dose profiles  

SciTech Connect

In passively scattered proton radiotherapy, a clinically useful treatment beam is produced by spreading a small proton 'pencil beam' extracted from the accelerator to create both a uniform dose profile laterally and a uniform spread-out Bragg peak (SOBP) in depth. Lateral spreading and range modulation of the beam are accomplished using specially designed components within the treatment delivery nozzle. The purpose of this study was to determine how changes in the size of the initial proton pencil beam affect the delivery of dose with a passive scatter treatment nozzle. Monte Carlo calculations were used to study changes of the beam's in-air energy distribution at the exit of the nozzle and the central axis depth dose profiles in water resulting from changes in the incident beam size. Our results indicate that the width of the delivered SOBP decreases as the size of the initial beam increases.

Polf, Jerimy C.; Harvey, Mark C.; Smith, Alfred R. [Department of Radiation Physics, University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 (United States)

2007-11-15

17

Differences in electron depth-dose curves calculated with EGS and ETRAN and improved energy-range relationships  

Microsoft Academic Search

For 1--50 MeV electrons incident on a water phantom there are systematic differences in the depth-dose curves calculated by the Monte Carlo codes EGS and ETRAN (and its descendants SANDYL, CYLTRAN, ACCEPT, and the ITS system). Compared to ETRAN, the EGS code calculates a higher surface dose and a slightly slower dose falloff past the dose maximum. The discrepancy in

D. W. O. Rogers; A. F. Bielajew

1986-01-01

18

Silicon Diodes as an Alternative to Diamond Detectors for Depth Dose Curves and Profile Measurements of Photon and Electron Radiation  

Microsoft Academic Search

\\u000a \\u000a Background:\\u000a   Depth dose curves and lateral dose profiles should correspond to relative dose to water in any measured point, what can be\\u000a more or less satisfied with different detectors. Diamond as detector material has similar dosimetric properties like water.\\u000a Silicon diodes and ionization chambers are also commonly used to acquire dose profiles.\\u000a \\u000a \\u000a \\u000a \\u000a Material and Methods:\\u000a   The authors compared dose profiles

Christian Scherf; Christiane Peter; Jussi Moog; Jörg Licher; Eugen Kara; Klemens Zink; Claus Rödel; Ulla Ramm

2009-01-01

19

Water depth measurement using an airborne pulsed neon laser system  

Microsoft Academic Search

Initial base-line field test performance results of the National Aeronautics and Space Administration's airborne oceanographic lidar (AOL) in the bathymetry mode are presented. Flight tests over the Atlantic Ocean yielded water depth measurements to 10 m. Water depths to 4.6 m were measured in the more turbid Chesapeake Bay. Water-truth measurements of depth and beam attenuation coefficients by boat were

F. E. Hoge; Robert N. Swift; Earl B. Frederick

1980-01-01

20

Polarization Lidar for Shallow Water Supraglacial Lake Depth Measurement  

NASA Astrophysics Data System (ADS)

A bathymetric, polarization lidar system transmitting at 532 nanometers and using a single photomultiplier tube is developed for applications of shallow water depth measurement, in particular those often found in supraglacial lakes of the ablation zone on the Greenland Ice Sheet. The technique exploits polarization attributes of the probed water body to isolate surface and floor returns, enabling constant fraction detection schemes to determine depth. The minimum resolvable water depth is no longer dictated by the system’s laser or detector pulse width and can achieve better than an order of magnitude improvement over current water depth determination techniques. In laboratory tests, a Nd:YAG microchip laser coupled with polarization optics, a photomultiplier tube, a constant fraction discriminator and a time to digital converter are used to target various water depths, using ice as the floor to simulate a supraglacial lake. Measurement of 1 centimeter water depths with an uncertainty of ±3 millimeters are demonstrated using the technique. This novel technique enables new approaches to designing laser bathymetry systems for shallow depth determination from remote platforms while not compromising deep water depth measurement, and will support comprehensive hydrodynamic studies of supraglacial lakes. Additionally, the compact size and low weight (<15 kg) of the field system currently in development presents opportunities for use in small unmanned aircraft systems (UAS) for large areal surveys of the ablation zone.

Mitchell, S.; Adler, J.; Thayer, J. P.; Hayman, M.

2010-12-01

21

SOME FACTORS INFLUENCING THE EXPERIMENTAL DETERMINATION OF PERCENTAGE DEPTH DOSES FOR MEDIUM ENERGY X RAYS  

Microsoft Academic Search

The effects of a number of variables on the experimental determination ; of percentage depth doses for medium energy x rays are discussed, including ; chamber size, type of applicator, and method of extrapolation to surface doserate. ; A method of transformation for converting depth doses for a diaphragm-limited-; field to those for a closedended applicator is also discussed. (auth);

R. G. Wood; W. H. Sutherland; M. Cohen

1963-01-01

22

Micronuclei induction in human lymphocytes induced by carbon ions exposion along the penetrate depth of ions in water  

NASA Astrophysics Data System (ADS)

Here we used cytokinesis-block micronucleus assay to measure the biological response along the penetrate depth of ions in water in human lymphocytes exposed to 100 MeV/u incident carbon ions in vitro. Polyethylene shielding was used to change the penetration depth of ions in water. A quantitative biological response curve was generated for micronuclei induction. The results showed a marked increase with the penetrate depth of ions in water in the micronuclei formation, which was consistent with a linear-energy-transfer dependent increase in biological effectiveness. The dose-response relationship for MN information was different at different penetrate depth of ions in water, at the 6 and 11.2 mm penetrate depth of ions in water, the dose-response relationships for the micronucleus frequencies induced by carbon ions irradiation were linear; while it was power function at 17.1 mm penetrate depth.

Wang, Z. Z.; Li, W. J.; Zhi, D. J.; Qu, Y.; Jing, X. G.

2009-08-01

23

ConcepTest: Ice Sheets and Water Depth  

NSDL National Science Digital Library

Ice sheets covered much of the Northern Hemisphere one million years ago during part of the last ice age. How did this affect the depth of water in the oceans? a. Oceans were shallower than today b. Oceans were ...

24

Modulational instability and wave growth in finite water depth  

NASA Astrophysics Data System (ADS)

The main feature of waves dynamic is the existence of modulational instability, which is the result of nonlinear interaction between a steep carrier wave with amplitude a0 and wave vector k0 and two infinitesimal side-band disturbances with wave vector k1 and k2. In finite water depth, the interaction between waves and the ocean floor induces a mean current. This subtracts energy from wave instability and the modulational instability ceases for relative water depth kh = 1.36. On the other hand, in general, unstable disturbances propagate obliquely to the direction of the carrier wave. When the depth decreases, the instability area becomes narrow and therefore its area decreases. At present, the growth of the sidebands has been treated in terms of the amplification of weak modulation imposed on a harmonic wave. A higher order spectral method is used to perform simulations of the random sea surface in arbitrary water depth. Third and fifth order of non-linearity expansion has been used to investigate the effect of modulational instability on random wave fields. Several configurations are considered with disturbances oblique and collinear with the primary waves and this for different water depths. The analysis shows that in the collinear case there is suppression of modulation instability for relative water depth kh=1.36. However, amplifications are observed in longer simulations. For directional cases the destabilization of a primary wave train and subsequent growth of side band perturbations produces amplification of surface elevations.

Fernández, Leandro; Onorato, Miguel; Monbaliu, Jaak; Toffoli, Alessandro

2013-04-01

25

Average fetal depth in utero: data for estimation of fetal absorbed radiation dose  

SciTech Connect

To estimate fetal absorbed dose from radiographic examinations, the depth from the anterior maternal surface to the midline of the fetal skull and abdomen was measured by ultrasound in 97 pregnant women. The relationships between fetal depth, fetal presentation, and maternal parameters of height, weight, anteroposterior (AP) thickness, gestational age, placental location, and bladder volume were analyzed. Maternal AP thickness (MAP) can be estimated from gestational age, maternal height, and maternal weight. Fetal midskull and abdominal depths were nearly equal. Fetal depth normalized to MAP was independent or nearly independent of maternal parameters and fetal presentation. These data enable a reasonable estimation of absorbed dose to fetal brain, abdomen, and whole body.

Ragozzino, M.W.; Breckle, R.; Hill, L.M.; Gray, J.E.

1986-02-01

26

Restoration Response of Relict Broadleaf Marshes to Increased Water Depths  

Microsoft Academic Search

Broadleaf marsh once covered much of the wetland landscape along the Kissimmee River in central Florida, USA, but is currently\\u000a restricted to remnant portions of the channelized floodplain that have been subjected to much shallower depths. The initial\\u000a phase of Kissimmee River restoration, which began in 1999, and a prior (1984–1990) demonstration project increased water depths\\u000a in several relict broadleaf

Louis A. Toth

2010-01-01

27

Depth  

PubMed Central

Depth is the feeling of remoteness, or separateness, that accompanies awareness in human modalities like vision and audition. In specific cases depths can be graded on an ordinal scale, or even measured quantitatively on an interval scale. In the case of pictorial vision this is complicated by the fact that human observers often appear to apply mental transformations that involve depths in distinct visual directions. This implies that a comparison of empirically determined depths between observers involves pictorial space as an integral entity, whereas comparing pictorial depths as such is meaningless. We describe the formal structure of pictorial space purely in the phenomenological domain, without taking recourse to the theories of optics which properly apply to physical space—a distinct ontological domain. We introduce a number of general ways to design and implement methods of geodesy in pictorial space, and discuss some basic problems associated with such measurements. We deal mainly with conceptual issues.

Koenderink, Jan J; van Doorn, Andrea J; Wagemans, Johan

2011-01-01

28

Depth.  

PubMed

Depth is the feeling of remoteness, or separateness, that accompanies awareness in human modalities like vision and audition. In specific cases depths can be graded on an ordinal scale, or even measured quantitatively on an interval scale. In the case of pictorial vision this is complicated by the fact that human observers often appear to apply mental transformations that involve depths in distinct visual directions. This implies that a comparison of empirically determined depths between observers involves pictorial space as an integral entity, whereas comparing pictorial depths as such is meaningless. We describe the formal structure of pictorial space purely in the phenomenological domain, without taking recourse to the theories of optics which properly apply to physical space-a distinct ontological domain. We introduce a number of general ways to design and implement methods of geodesy in pictorial space, and discuss some basic problems associated with such measurements. We deal mainly with conceptual issues. PMID:23145244

Koenderink, Jan J; van Doorn, Andrea J; Wagemans, Johan

2011-09-15

29

[Depth dose characteristics of photon beams released from a scanning-type racetrack microtron].  

PubMed

The MM50 is a racetrack microtron that can emit photon beams or electron beams up to 50 MeV. The MM22 using the scanning beam method and the MM22 using a flattening filter method both to flatten the emission field and a water phantom with particular function measurable of PDD etc. in an accelerator using the scanning beam method to make up the PDD curve of photon beams from the linear accelerator. The Clinac21EX was thus employed. The maximum depth of beam flux was shallow, the gradient of the flux decrement large, the surface dose large, and the estimated nominal energy low to the same nominal energy. From these findings, it can be said that thorough comprehension of the characteristics of beam flux properties for these units is necessary when photon beams are to be used. PMID:12518102

Sato, Tomoharu

2002-06-01

30

NEUTRON REFLECTION AND FLUX VERSUS DEPTH FOR WATER, WITH AN APPENDIX, COMPARISON WITH RESULTS OF NATIONAL BUREAU OF STANDARDS  

Microsoft Academic Search

Detailed calculated results on neutron reflection and flux versus depth ; for water are given in the form of machine printouts. The angular and energy ; distributions of the reflected neutrons along with the energy-dependent and total ; flux at various depths are contained in tabular form on the printouts. Neutron ; number current, number flux and dose transmission as

F. J. Allen; A. Futterer; W. Wright

1963-01-01

31

The Effect of a Carbon-Fiber Couch on the Depth-Dose Curves and Transmission Properties for Megavoltage Photon Beams  

Microsoft Academic Search

Purpose:  To investigate the attenuation of a carbon-fiber tabletop and a combiboard, alongside with the depth-dose profile in a solid-water phantom.Material and Methods:  Depth-dose measurements were performed with a Roos chamber for 6- and 10-MV beams for a typical field size (15 cm 15 cm, SSD [source-surface distance] 100 cm). A rigid-stem ionization chamber was used to measure transmission factors.Results:  Transmission factors varied

Björn Poppe; Ndimofor Chofor; Antje Rühmann; Wolfgang Kunth; Armand Djouguela; Ralf Kollhoff; Kay C. Willborn

2007-01-01

32

Effects of prescription depth, cylinder size, treatment length, tip space, and curved end on doses in high-dose-rate vaginal brachytherapy  

SciTech Connect

Purpose: To determine the effects of the prescription depth, cylinder size, treatment length, tip space, and curved end on high-dose-rate vaginal brachytherapy (HDR-VBT) of endometrial cancer. Methods and Materials: Treatment plans were prescribed and optimized based on points at the cylinder surface or at 0.5-cm depth. Cylinder sizes ranging from 2 to 4 cm in diameter, and treatment lengths ranging from 3 to 8 cm were used. Dose points in various depths were precisely defined along the cylinder dome. The given dose and dose uniformity to a depth of interest were measured by the mean dose (MD) and standard deviation (SD), respectively, among the dose points belonging to the depth. Dose fall-off beyond the 0.5 cm treatment depth was determined by the ratio of MD at 0.75-cm depth to MD at 0.5-cm depth. Results: Dose distribution varies significantly with different prescriptions. The surface prescription provides more uniform doses at all depths in the target volume, whereas the 0.5-cm depth prescription creates larger dose variations at the cylinder surface. Dosimetric uncertainty increases significantly (>30%) with shorter tip space. Extreme hot (>150%) and cold spots (<60%) occur if no optimization points were placed at the curved end. Conclusions: Instead of prescribing to a depth of 0.5 cm, increasing the dose per fraction and prescribing to the surface with the exact surface points around the cylinder dome appears to be the optimal approach.

Li Shidong [Department of Radiation Oncology, Henry Ford Health System, Detroit, Michigan (United States)]. E-mail: sli1@hfhs.org; Aref, Ibrahim [Department of Radiation Oncology, Henry Ford Health System, Detroit, Michigan (United States); Walker, Eleanor [Department of Radiation Oncology, Henry Ford Health System, Detroit, Michigan (United States); Movsas, Benjamin [Department of Radiation Oncology, Henry Ford Health System, Detroit, Michigan (United States)

2007-03-15

33

Modulational instability and rogue waves in finite water depth  

NASA Astrophysics Data System (ADS)

The mechanism of side band perturbations to a uniform wave train is known to produce modulational instability and in deep water conditions it is accepted as a plausible cause for rogue wave formation. In a condition of finite water depth, however, the interaction with the sea floor generates a wave-induced current that subtracts energy from the wave field and consequently attenuates this instability mechanism. As a result, a plane wave remains stable under the influence of collinear side bands for relative water depths kh ≤ 1.36 (where k represents the wavenumber of the plane wave and h the water depth), but it can still destabilise due to oblique perturbations. Using direct numerical simulations of the Euler equations, it is here demonstrated that oblique side bands are capable of triggering modulational instability and eventually leading to the formation of rogue waves also for kh ≤ 1.36. Results, nonetheless, indicates that modulational instability cannot sustain a substantial wave growth for kh < 0.8.

Fernandez, L.; Onorato, M.; Monbaliu, J.; Toffoli, A.

2013-10-01

34

Mixing intensity modulated electron and photon beams: combining a steep dose fall-off at depth with sharp and depth-independent penumbras and flat beam profiles  

Microsoft Academic Search

For application in radiotherapy, intensity modulated high-energy electron and photon beams were mixed to create dose distributions that feature: (a) a steep dose fall-off at larger depths, similar to pure electron beams, (b) flat beam profiles and sharp and depth-independent beam penumbras, as in photon beams, and (c) a selectable skin dose that is lower than for pure electron beams.

Erik W. Korevaar; Ben J. M. Heijmen; Evert Woudstra; Henk Huizenga; Anders Brahme

1999-01-01

35

Underwater depth reconstruction by local water wave measurements  

NASA Astrophysics Data System (ADS)

We present an experimental study of underwater depth reconstruction obtained by a method based on the Bessel series expansion of the solutions of the 2D linear water wave equation. This is achieved by measuring capillary-gravity waves using a contactless space-time resolved Fourier Transform Profilometry method. The ability of the method is exemplified for several type of bathymetry in laboratory experiments.

Przadka, A.; Petitjeans, P.; Pagneux, V.; Maurel, A.; Ing, R. K.

2013-09-01

36

Marine Riser System for 7,500Ft Water Depth  

Microsoft Academic Search

The design, construction and some of the operational experience with an 18-5\\/8-inch marine riser system for drilling in water depths of 5,000 - 7,500 feet in the Offshore East Coast, U.S.A. area are described. The more important stress criteria and analysis, along with generalized descriptions of, and rationale for, particular system components are presented. Unique system features include: 1. All

G. L. Marsh; E. B. Denison; S. J. Pekera

1984-01-01

37

Program analyzes marine riser systems in any water depth  

SciTech Connect

A frequency-domain computer program has been developed for analyzing marine riser systems in any water depth likely to be exploited by offshore operators. The program allows engineers to fine-tune the design of a marine riser at minimal cost. Hundreds of computer runs can be made to measure the effects of different boundary conditions or varying environmental factors without using up a big part of the project budget.

Not Available

1984-02-01

38

Diffuse reflectance of oceanic shallow waters: Influence of water depth and bottom albedo  

Microsoft Academic Search

We used simplifying assumptions to derive analytical formulae expressing the reflectance of shallow waters as a function of observation depth and of bottom depth and albedo. These formulae also involve two apparent optical properties of the water body: a mean diffise attenuation coefficient and a hypothetical reflectance which would be observed if the bottom was infinitely deep. The validity of

STÉPHANE MARITORENA; ANDRÉ MOREL; BERNARD GENTILI

1994-01-01

39

Estimating water equivalent snow depth from related meteorological variables  

SciTech Connect

Engineering design must take into consideration natural loads and stresses caused by meteorological elements, such as, wind, snow, precipitation and temperature. The purpose of this study was to determine a relationship of water equivalent snow depth measurements to meteorological variables. Several predictor models were evaluated for use in estimating water equivalent values. These models include linear regression, principal component regression, and non-linear regression models. Linear, non-linear and Scandanavian models are used to generate annual water equivalent estimates for approximately 1100 cooperative data stations where predictor variables are available, but which have no water equivalent measurements. These estimates are used to develop probability estimates of snow load for each station. Map analyses for 3 probability levels are presented.

Steyaert, L.T.; LeDuc, S.K.; Strommen, N.D.; Nicodemus, M.L.; Guttman, N.B.

1980-05-01

40

Dose specification for radiation therapy: dose to water or dose to medium?  

NASA Astrophysics Data System (ADS)

The Monte Carlo method enables accurate dose calculation for radiation therapy treatment planning and has been implemented in some commercial treatment planning systems. Unlike conventional dose calculation algorithms that provide patient dose information in terms of dose to water with variable electron density, the Monte Carlo method calculates the energy deposition in different media and expresses dose to a medium. This paper discusses the differences in dose calculated using water with different electron densities and that calculated for different biological media and the clinical issues on dose specification including dose prescription and plan evaluation using dose to water and dose to medium. We will demonstrate that conventional photon dose calculation algorithms compute doses similar to those simulated by Monte Carlo using water with different electron densities, which are close (<4% differences) to doses to media but significantly different (up to 11%) from doses to water converted from doses to media following American Association of Physicists in Medicine (AAPM) Task Group 105 recommendations. Our results suggest that for consistency with previous radiation therapy experience Monte Carlo photon algorithms report dose to medium for radiotherapy dose prescription, treatment plan evaluation and treatment outcome analysis.

Ma, C.-M.; Li, Jinsheng

2011-05-01

41

Paleoslope and water depth estimate, lower Wolfcampian, Hugoton embayment of the Anadarko basin  

Microsoft Academic Search

Three criteria are used in combination to estimate paleoslope and maximum water depth during deposition of seven lower Wolfcamp (Council Grove Group) sedimentary cycles on a low relief shelf in Kansas and Oklahoma. Landward extent of paleo-shoreline establishes zero water depth at maximum flooding, and the updip extent of depth-specific fauna (fusulinids) establishes approximate water depth along a sub parallel

Martin K. Dubois

42

Measurements of relative depth doses and Cerenkov light using a scintillating fiber-optic dosimeter with Co-60 radiotherapy source.  

PubMed

In this study, we fabricated a scintillating fiber-optic dosimeter, which consists of an organic scintillator and a plastic optical fiber, for radiotherapy dosimetry. To select an adequate kind and length of scintillator for ?-rays generated from a Co-60 source, scintillating light from various kinds and lengths of organic scintillators is measured. Using a scintillating fiber-optic dosimeter, the ?-rays generated from a Co-60 therapy unit are measured and relative doses are obtained according to the field size of the ?-ray beam and the depth in a water phantom. Also, Cerenkov light generated by the interactions of primary or secondary electrons and the plastic optical fiber is measured with different field sizes and depths of a water phantom using a background optical fiber. PMID:21889353

Jang, Kyoung Won; Yoo, Wook Jae; Moon, Jinsoo; Han, Ki Tek; Park, Jang-Yeon; Lee, Bongsoo

2011-08-16

43

Derivation of electron and photon energy spectra from electron beam central axis depth dose curves  

Microsoft Academic Search

A method for deriving the electron and photon energy spectra from electron beam central axis percentage depth dose (PDD) curves has been investigated. The PDD curves of 6, 12 and 20 MeV electron beams obtained from the Monte Carlo full phase space simulations of the Varian linear accelerator treatment head have been used to test the method. We have employed

Jun Deng; Steve B. Jiang; Todd Pawlicki; Jinsheng Li; C.-M. Ma

2001-01-01

44

GROUNDSHINE DOSE-RATE CONVERSION FACTORS OF SOIL CONTAMIANTED TO DIFFERENT DEPTHS.  

PubMed

For assessment of external doses from the ground contaminated with radionuclides, the dose-rate conversion factors (DCFs) prescribed in FGR (Federal Guidance Report) 12 have been used. Recently, significant changes were made by International Commission on Radiological Protection in dosimetric models and parameters, which include use of Reference Phantoms and revised tissue-weighting factors, as well as the updated decay data of radionuclides. The DCFs for effective and equivalent doses due to groundshine from contaminated soil were re-calculated by taking the changes into account. In this study, the DCFs for effective and equivalent doses were calculated for depths of 1, 5 and 15 cm and for infinite deposition. Doses to the Reference Phantoms were calculated by Monte Carlo simulations with the MCNPX 2.7.0 radiation transport code for 26 mono-energy photons between 0.01 and 10 MeV. Transport calculations were performed for the source volume within the converging of distances and depths practically contributing to the dose rates, which were determined by a simple model. With the resulting doses, empirical response functions were constructed as a function of photon energy. The DCFs for the radionuclides considered important were evaluated by combining the photon emission data of the radionuclide and the response functions. Finally, the contributions of accompanied beta particles to the skin equivalent doses and the effective doses were calculated separately and added to the DCFs. For radionuclides considered in this study, the new DCFs for the different depths agreed within 10 % with the data in FGR12. PMID:23765073

Yoo, Song Jae; Lee, Jai-Ki; Kim, Eun-Han; Jeong, Kyu Hwan; Cho, Gyuseong

2013-06-13

45

Simulations of crescent water wave patterns on finite depth  

NASA Astrophysics Data System (ADS)

A numerical study of the instabilities of Stokes waves on finite depth has been carried out using an efficient fully nonlinear method [D. Clamond and J. Grue, ``A fast method for fully nonlinear water-wave computations,'' J. Fluid Mech. 447, 337 (2001)]. First, attention is given to five-wave instabilities with k0h=O(1), k0 being the wavenumber and h the depth. Both instabilities leading to breaking and instabilities leading to recurrence are studied, yielding considerably different patterns than on infinite depth. Higher-order instabilities are exemplified, for the first time, by simulations of six- and seven-wave instabilities. Simulations of interactions between four- and five-wave instabilities show that a classical modulational instability can destabilize a three-dimensional perturbation causing crescent waves to appear, in accordance with the hypothesis of [M.-Y. Su and A. W. Green, ``Coupled two- and three-dimensional instabilities of surface gravity waves,'' Phys. Fluids 27, 2595 (1984)]. Also, a recurrent five-wave instability can boost the energy in a four-wave instability.

Kristiansen, Ø.; Fructus, D.; Clamond, D.; Grue, J.

2005-06-01

46

Hyperspectral Remote Sensing for Shallow Waters. 2. Deriving Bottom Depths and Water Properties by Optimization  

NASA Astrophysics Data System (ADS)

In earlier studies of passive remote sensing of shallow-water bathymetry, bottom depths were usually derived by empirical regression. This approach provides rapid data processing, but it requires knowledge of a few true depths for the regression parameters to be determined, and it cannot reveal in-water constituents. In this study a newly developed hyperspectral, remote-sensing reflectance model for shallow water is applied to data from computer simulations and field measurements. In the process, a remote-sensing reflectance spectrum is modeled by a set of values of absorption, backscattering, bottom albedo, and bottom depth; then it is compared with the spectrum from measurements. The difference between the two spectral curves is minimized by adjusting the model values in a predictor -corrector scheme. No information in addition to the measured reflectance is required. When the difference reaches a minimum, or the set of variables is optimized, absorption coefficients and bottom depths along with other properties are derived simultaneously. For computer-simulated data at a wind speed of 5 m /s the retrieval error was 5.3% for depths ranging from 2.0 to 20.0 m and 7.0% for total absorption coefficients at 440 nm ranging from 0.04 to 0.24 m-1 . At a wind speed of 10 m /s the errors were 5.1% for depth and 6.3% for total absorption at 440 nm. For field data with depths ranging from 0.8 to 25.0 m the difference was 10.9% (R2 = 0 .96 , N =37 ) between inversion-derived and field-measured depth values and just 8.1% (N = 33 ) for depths greater than 2.0 m. These results suggest that the model and the method used in this study, which do not require in situ calibration measurements, perform very well in retrieving in-water optical properties and bottom depths from above-surface hyperspectral measurements.

Lee, Zhongping; Carder, Kendall L.; Mobley, Curtis D.; Steward, Robert G.; Patch, Jennifer S.

1999-06-01

47

Dose to medium versus dose to water as an estimator of dose to sensitive skeletal tissue  

Microsoft Academic Search

The purpose of this study is to determine whether dose to medium, Dm, or dose to water, Dw, provides a better estimate of the dose to the radiosensitive red bone marrow (RBM) and bone surface cells (BSC) in spongiosa, or cancellous bone. This is addressed in the larger context of the ongoing debate over whether Dm or Dw should be

B. R. B. Walters; R. Kramer; I. Kawrakow

2010-01-01

48

Marine riser system for 7,500-Ft water depth  

SciTech Connect

The design, construction and some of the operational experience with an 18-5/8-inch marine riser system for drilling in water depths of 5,000 - 7,500 feet in the Offshore East Coast, U.S.A. area are described. The more important stress criteria and analysis, along with generalized descriptions of, and rationale for, particular system components are presented. Unique system features include: 1. All H/sub 2/S rated fluid exposed parts 2. Extra high capacity, forged, flange-type bolted connectors 3. Hybrid flotation 4. Backup emergency riser release 5. Instrumented riser joint 6. Fill valve to prevent collapse 7. Extra heavy duty telescoping joint and instrumented upper flex joint 8. 15,000 psi WP (working pressure) integral choke and kill lines

Marsh, G.L.; Denison, E.B.; Pekera, S.J.

1984-05-01

49

Effects of variations in soil water potential, depth of N placement, and cultivar on postanthesis N uptake by wheat  

Microsoft Academic Search

This study was conducted to investigate the influence of soil water potential, depth of N placement, timing, and cultivar on uptake of a small dose of labeled N applied after anthesis by wheat (Triticum aestivum L.) Understanding postanthesis N accumulation should allow better control of grain protein concentration through proper manipulation of inputs. Two hard, red spring-wheat cultivars were planted

S. B. Wuest; K. G. Cassman

1992-01-01

50

Simulation of depth-dose distributions for various ions in polyethylene medium  

NASA Astrophysics Data System (ADS)

Study of depth-dose distributions for intermediate energy ion beams in tissue-like media such as polyethylene (CH2)n provides a good platform for further improvements in the fields of hadrontherapy and space radiation shielding. The depth-dose distributions for 12C ions at various energies and for light and intermediate ion beams (3He, 16O, 20Ne and 28Si) as well as for heavy ions 56Fe in polyethylene were estimated by using simulation toolkit: Geant4. Calculations were performed mainly by considering two different combinations of standard electromagnetic (EM), binary cascade (BIC), statistical multifragmentation (SMF) and Fermi breakup (FB) models. The energies of the ion beams were selected to achieve the Bragg peaks at predefined position (˜60 mm) and as per their availability. Variations of peak-to-entrance ratio (from 7.44 ± 0.05 to 8.87 ± 0.05), entrance dose (from 2.89 ± 0.01 to 203.71 ± 0.63 MeV/mm) and entrance stopping power (from 3.608 to 208.858 MeV/mm, calculated by SRIM) with atomic number (Z) were presented in a systematic manner. The better peak-to-entrance ratio and less entrance dose in the region Z = 2 to 8 (i.e. 3He to 16O) may provide the suitability of the ion beams for hadrontherapy.

Kumar, Ashavani; Jalota, Summit; Gupta, Renu

2012-06-01

51

Calculated and measured depth dose profiles in a phantom exposed to neutron radiation fields  

SciTech Connect

An accurate evaluation of doses caused by external sources of neutron radiation depends on knowledge of the transport of radiation inside the human body. Health physicists use two primary methods for studying this radiation transport: computer calculations and measurements. Both computer calculations and measurements were performed under well controlled, nearly identical conditions to determine the extent of their agreement. A comparison of the dose profiles predicted by both measurements and calculations was thus possible. The measurements were performed in a cylindrical phantom made of tissue equivalent plastic. The phantom size, 61 cm high and 30 cm in diameter, was chosen to approximate the human torso and to match the dimensions of cylindrical phantoms used by previous calculations. Holes were drilled down through the phantom to accommodate small tissue equivalent proportional counters (TEPCs) at various depths in the phantom. These counters were used to measure the neutron dose inside the phantom when it was exposed to various sources of neutrons. The holes in the phantom could also accommodate miniature Geiger-Mueller detectors to measure the gamma component of the dose. Neutron and gamma dose profiles were measured for two different sources of neutrons: an unmoderated /sup 252/Cf source and a 733-keV neutron beam generated by a Van de Graaff accelerator. 14 refs., 13 figs., 11 tabs.

Scherpelz, R.I.; Tanner, J.E.; Sigalla, L.A.; Hadlock, D.E.

1989-05-01

52

Depth absorbed dose and LET distributions of therapeutic 1H, 4He, 7Li, and 12C beams.  

PubMed

The depth absorbed dose and LET (linear energy transfer) distribution of different ions of clinical interest such as 1H, 4He, 7Li, and 12C ions have been investigated using the Monte Carlo code SHIELD-HIT. The energies of the projectiles correspond to ranges in water and soft tissue of approximately 260 mm. The depth dose distributions of the primary particles and their secondaries have been calculated and separated with regard to their low and high LET components. A LET value below 10 eV/nm can generally be regarded as low LET and sparsely ionizing like electrons and photons. The high LET region may be assumed to start at 20 eV/nm where on average two double-strand breaks can be formed when crossing the periphery of a nucleosome, even though strictly speaking the LET limits are not sharp and ought to vary with the charge and mass of the ion. At the Bragg peak of a monoenergetic high energy proton beam, less than 3% of the total absorbed dose is comprised of high LET components above 20 eV/nm. The high LET contribution to the total absorbed dose in the Bragg peak is significantly larger with increasing ion charge as a natural result of higher stopping power and lower range straggling. The fact that the range straggling and multiple scattering are reduced by half from hydrogen to helium increases the possibility to accurately deposit only the high LET component in the tumor with negligible dose to organs at risk. Therefore, the lateral penumbra is significantly improved and the higher dose gradients of 7Li and 12C ions both longitudinally and laterally will be of major advantage in biological optimized radiation therapy. With increasing charge of the ion, the high LET absorbed dose in the beam entrance and the plateau regions where healthy normal tissues are generally located is also increased. The dose distribution of the high LET components in the 7Li beam is only located around the Bragg peak, characterized by a Gaussian-type distribution. Furthermore, the secondary particles produced by high energy 7Li ions in tissuelike media have mainly low LET character both in front of and beyond the Bragg peak. PMID:17278503

Kempe, Johanna; Gudowska, Irena; Brahme, Anders

2007-01-01

53

Energy Spectra of RITS-6 Electron Beam Derived from Depth Dose Measurements  

NASA Astrophysics Data System (ADS)

Until recently the main methods of determining the output voltage of the diode of the RITS-6 accelerator (nominal 7-12 MV) has been through parapotential flow theory of the magnetically insulated transmission line (MITL), a radiographers equation based on radiation transport calculations for a particular diode configuration, or particle-in-cell simulations of various regions of the accelerator. Time integrated measurements of the depth-dose profile using radiochromic films have been performed on RITS for large area diodes. Comparisons to theoretical predictions for monoenergetic beams and empirical relations for the average electron energy are presented as well as a potential method for unfolding the electron energy distribution.

Webb, Timothy; Oliver, Bryan; Bruner, Nichelle

2008-11-01

54

First experimental-based characterization of oxygen ion beam depth dose distributions at the Heidelberg Ion-Beam Therapy Center  

NASA Astrophysics Data System (ADS)

Over the last decades, the application of proton and heavy-ion beams to external beam radiotherapy has rapidly increased. Due to the favourable lateral and depth dose profile, the superposition of narrow ion pencil beams may enable a highly conformal dose delivery to the tumour, with better sparing of the surrounding healthy tissue in comparison to conventional radiation therapy with photons. To fully exploit the promised clinical advantages of ion beams, an accurate planning of the patient treatments is required. The clinical treatment planning system (TPS) at the Heidelberg Ion-Beam Therapy Center (HIT) is based on a fast performing analytical algorithm for dose calculation, relying, among others, on laterally integrated depth dose distributions (DDDs) simulated with the FLUKA Monte Carlo (MC) code. Important input parameters of these simulations need to be derived from a comparison of the simulated DDDs with measurements. In this work, the first measurements of 16O ion DDDs at HIT are presented with a focus on the determined Bragg peak positions and the understanding of factors influencing the shape of the distributions. The measurements are compared to different simulation approaches aiming to reproduce the acquired data at best. A simplified geometrical model is first used to optimize important input parameters, not known a priori, in the simulations. This method is then compared to a more realistic, but also more time-consuming simulation approach better accounting for the experimental set-up and the measuring process. The results of this work contributed to a pre-clinical oxygen ion beam database, which is currently used by a research TPS for corresponding radio-biological cell experiments. A future extension to a clinical database used by the clinical TPS at HIT is foreseen. As a side effect, the performed investigations showed that the typical water equivalent calibration approach of experimental data acquired with water column systems leads to slight deviations between the experimentally determined and the real Bragg peak positions. For improved accuracy, the energy dependence of the stopping power, and herewith the water equivalent thickness, of the material downstream of the water tank should be considered in the analysis of measured data.

Kurz, C.; Mairani, A.; Parodi, K.

2012-08-01

55

An investigation of the depth dose in the build-up region, andsurface dose for a 6-MV therapeutic photon beam: Monte Carlo simulation and measurements.  

PubMed

The percentage depth dose in the build-up region and the surface dose for the 6-MV photon beam from a Varian Clinac 23EX medical linear accelerator was investigated for square field sizes of 5 × 5, 10 × 10, 15 × 15 and 20 × 20 cm(2)using the EGS4nrc Monte Carlo (MC) simulation package. The depth dose was found to change rapidly in the build-up region, and the percentage surface dose increased proportionally with the field size from approximately 10% to 30%. The measurements were also taken using four common detectors: TLD chips, PFD dosimeter, parallel-plate and cylindrical ionization chamber, and compared with MC simulated data, which served as the gold standard in our study. The surface doses obtained from each detector were derived from the extrapolation of the measured depth doses near the surface and were all found to be higher than that of the MC simulation. The lowest and highest over-responses in the surface dose measurement were found with the TLD chip and the CC13 cylindrical ionization chamber, respectively. Increasing the field size increased the percentage surface dose almost linearly in the various dosimeters and also in the MC simulation. Interestingly, the use of the CC13 ionization chamber eliminates the high gradient feature of the depth dose near the surface. The correction factors for the measured surface dose from each dosimeter for square field sizes of between 5 × 5 and 20 × 20 cm(2)are introduced. PMID:23104898

Apipunyasopon, Lukkana; Srisatit, Somyot; Phaisangittisakul, Nakorn

2012-10-26

56

Present and future development of offshore structures in over 100 m water depth  

Microsoft Academic Search

In 1967 the 100 m water depth was reached for a permanently installed steel piled platform in the Gulf of Mexico. Since then over 300 platforms have been installed in that area of which only 9 in deeper water than 100 m. In 1976 the first platform will be installed in over 200 m water depth offshore California and for

Sjoerdsma

1979-01-01

57

EFFECT OF WATER DEPTH AND AERATION ON A CONTACT MEDIA CHANNEL PURIFICATION PROCESS FOR WASTEWATER RECLAMATION  

Microsoft Academic Search

In this study, contact media channel purification process (CMCP) filled with honeycomb media was adopted to implement continuous flow experiments when aeration and water depth varied. The water depth was set at 0.2, 0.5 and 0.8 m, respectively. Three aeration values including 30, 50 and 70 m h-1 were operated at each water depth. The results indicated that the removal

Tzu-Yi Pai; Chwen-Jeng Tzeng; Chen-Lung Hsu; Yao-Sheng Tsai; Wen-Jui Hsu

58

Correction for depth biases to shallow water multibeam bathymetric data  

NASA Astrophysics Data System (ADS)

Vertical errors often present in multibeam swath bathymetric data. They are mainly sourced by sound refraction, internal wave disturbance, imperfect tide correction, transducer mounting, long period heave, static draft change, dynamic squat and dynamic motion residuals, etc. Although they can be partly removed or reduced by specific algorithms, the synthesized depth biases are unavoidable and sometimes have an important influence on high precise utilization of the final bathymetric data. In order to confidently identify the decimeter-level changes in seabed morphology by MBES, we must remove or weaken depth biases and improve the precision of multibeam bathymetry further. The fixed-interval profiles that are perpendicular to the vessel track are generated to adjust depth biases between swaths. We present a kind of postprocessing method to minimize the depth biases by the histogram of cumulative depth biases. The datum line in each profile can be obtained by the maximum value of histogram. The corrections of depth biases can be calculated according to the datum line. And then the quality of final bathymetry can be improved by the corrections. The method is verified by a field test.

Yang, Fan-lin; Li, Jia-biao; Liu, Zhi-min; Han, Li-tao

2013-04-01

59

Water Table Depth and Growth of Young Cottonwood.  

National Technical Information Service (NTIS)

Planted cottonwood grew best when the water table was about 2 feet deep, whether the tree was planted on soil with a high water table or the water table was raised 1 year after planting. Growth over a 1-foot-deep water table was about the same as over no ...

W. M. Broadfoot

1973-01-01

60

Propagation in water with uniform sound velocity but variable-depth lossy bottom  

Microsoft Academic Search

The consequences of a very simple formula for underwater acoustic transmission loss are explored, coping with bottom losses and any slow variations in depth but restricted here to water without vertical sound velocity gradients. The intensity-range laws are given for many specific depth profiles. In constant-depth water the intensity varies as (range)-3\\/2, and it is shown that to obtain (range)-'

D. E. Weston

1976-01-01

61

Predicting shallow water table depth at regional scale from rainfall and soil data  

NASA Astrophysics Data System (ADS)

We model the spatio-temporal changes of shallow water table depth at regional scale. The model assumes a sinusoidal behavior of the water table with a bimodal yearly cycle. The predictive tool is based on cumulative rainfall data and long term water table characteristics. Integrating soil information will increase the accuracy of the model. Spatio-temporal maps of the water table depth will be used to optimize irrigation management.

Calzolari, Costanza; Ungaro, Fabrizio

2012-01-01

62

Changes in photosynthetic pigment concentration in seaweeds as a function of water depth  

Microsoft Academic Search

We conducted a study of the relationship between changes in photosynthetic pigment content and water depth in Great Harbor near Woods Hole, Massachusetts, USA, on the green algae Ulva lactuca and Codium fragile and the red algae Porphyra umbilicalis and Chondrus crispus. A calibrated underwater photometer equipped with spectral band filters measured light attenuation by the water column. The depth

J. Rarnus; S. I. Beale; D. Mauzerall; K. L. Howard

1976-01-01

63

Variation in bioturbation with water depth on marine slopes: a study on the Little Bahamas Bank  

Microsoft Academic Search

Reconstructing the paleoceanography of intermediate-depth waters is dependent on sedimentary records preserved on marine slopes. But knowledge of bioturbation processes in such slope environments is much poorer than for the deep sea. In this study, 210Pb profiles were measured for the upper ?20 cm of sediment from five box cores taken on the slopes of the Bahamas in water depths

Gideon M. Henderson; Fara N. Lindsay; Niall C. Slowey

1999-01-01

64

The depth-inversion problem in shallow water 1  

Microsoft Academic Search

Two Depth Inversion Algorithms (DIAs) were developed and validated using on results of computations for the shoaling of periodic waves over mild slopes, in a two- dimensional numerical wave tank, based on fully nonlinear potential flow theory. The first algorithm, DIA1, uses sets of values of wave celerity , height , and spatial wavelengths and , simultaneously measured at a

T. Grilli

65

Changes to dose at surface and shifts of dose distributions at depth through dry and wet wound dressings for photon and electron beam radiotherapy.  

PubMed

Wound dressings are used during patient radiotherapy treatments, particularly in cases of radiation induced lesions. Potentially, the presence of a dressing may increase the dose to the skin, further aggravating the skin reaction and decrease the dose at depth. The changes are dependent on linear accelerator beam type and beam quality and were determined for 4 and 10 MV photon energies and 6 and 15 MeV electron energies using a slab phantom and fixed separation parallel plate chambers. Since these dressings have been designed to be used on exuding wounds, measurements were taken under eight different wound dressings in both dry and wet state. Irradiations with photon energies increased the skin dose significantly (max. increase: 68.1 %; average increase: 48 %) with little or no change to dose at depth. Electron beam energies showed little or no change to doses at the surface, but the dose distribution was shifted towards the surface. The maximum decrease in dose at depth was 3.6 % for 6 and 15 MeV through all dressings except one and was therefore considered to be clinically insignificant. A change in dose at surface of 9.7 % and at R(50) of 25.9 %, equivalent to a shift of dose towards the surface of 7.5 mm, was measured for one dressing. This demonstrates that it is possible for a wet dressing to significantly alter electron beam dosimetry. PMID:22733122

Mac Nally, Ciara; Woodings, Simon

2012-06-26

66

Depth inversion in coastal water based on SAR image of waves  

NASA Astrophysics Data System (ADS)

Wave-number spectrum technique is proposed to retrieve coastal water depths by means of Synthetic Aperture Radar (SAR) image of waves. Based on the general dispersion relation of ocean waves, the wavelength changes of a surface wave over varying water depths can be derived from SAR. Approaching the analysis of SAR images of waves and using the general dispersion relation of ocean waves, this indirect technique of remote sensing bathymetry has been applied to a coastal region of Xiapu in Fujian Province, China. Results show that this technique is suitable for the coastal waters especially for the near-shore regions with variable water depths.

Fan, Kaiguo; Huang, Weigen; He, Mingxia; Fu, Bin; Zhang, Biao; Chen, Xiaoyan

2008-11-01

67

Comparative study of depth dose distributions for beams of light and heavy nuclei in tissue-like media  

NASA Astrophysics Data System (ADS)

We study the energy deposition by beams of light and heavy nuclei in tissue-like media for their possible application in charged-particle cancer therapy. The depth dose distributions for protons, 3He, 12C, 20Ne and 58Ni nuclei are calculated within a Monte Carlo model based on the GEANT4 toolkit. These distributions are compared with each other and with available experimental data. It is demonstrated that nuclear fragmentation reactions essentially reduce the peak-to-plateau ratio of the dose profiles for deeply penetrating energetic ions heavier than 3He. On the other hand, the shapes of depth dose profiles for all projectiles up to 58Ni were found similar at low penetration depths.

Pshenichnov, Igor; Mishustin, Igor; Greiner, Walter

2008-04-01

68

Irrigation Water Quality, Rooting Depth, and Nutrient Budgets in Citrus.  

National Technical Information Service (NTIS)

The effects of salinized irrigation water on tree canopy and root growth, water use, foliar nutrition, and leaching losses below the root zone were studied during a 2-year period using single tree lysimeters. Eighteen 6-year-old 'Valencia' orange trees on...

J. P. Syvertsen J. D. Lea-Cox A. Alva B. Bowman

1993-01-01

69

Artificial neural network modeling of water table depth fluctuations  

Microsoft Academic Search

Three types of functionally different artificial neural network (ANN) models are calibrated using a relatively short length of groundwater level records and related hydrometeorlogical data to simulate water table fluctuations in the Gondo aquifer, Burkina Faso. Input delay neural network (IDNN) with static memory structure and globally recurrent neural network (RNN) with inherent dynamical memory are proposed for monthly water

Paulin Coulibaly; François Anctil; Ramon Aravena; Bernard Bobée

2001-01-01

70

Rainfall exclusion in an eastern Amazonian forest alters soil water movement and depth of water uptake.  

PubMed

Deuterium-labeled water was used to study the effect of the Tapajós Throughfall Exclusion Experiment (TTEE) on soil moisture movement and on depth of water uptake by trees of Coussarea racemosa, Sclerolobium chrysophyllum, and Eschweilera pedicellata. The TTEE simulates an extended dry season in an eastern Amazonian rainforest, a plausible scenario if the El Niño phenomenon changes with climate change. The TTEE excludes 60% of the wet season throughfall from a 1-ha plot (treatment), while the control 1-ha plot receives precipitation year-round. Mean percolation rate of the label peak in the control plot was greater than in the treatment plot during the wet season (0.75 vs. 0.07 m/mo). The rate was similar for both plots during the dry season (ca. 0.15 m/mo), indicative that both plots have similar topsoil structure. Interestingly, the label peak in the control plot during the dry season migrated upward an average distance of 64 cm. We show that water probably moved upward through soil pores-i.e., it did not involve roots (hydraulic lift)-most likely because of a favorable gradient of total (matric + gravitational) potential coupled with sufficient unsaturated hydraulic conductivity. Water probably also moved upward in the treatment plot, but was not detectable; the label in this plot did not percolate below 1 m or beyond the depth of plant water uptake. During the dry season, trees in the rainfall exclusion plot, regardless of species, consistently absorbed water significantly deeper, but never below 1.5-2 m, than trees in the control plot, and therefore may represent expected root function of this understory/subcanopy tree community during extended dry periods. PMID:21652421

Romero-Saltos, Hugo; Sternberg, Leonel da S L; Moreira, Marcelo Z; Nepstad, Daniel C

2005-03-01

71

Polynomial expressions of electron depth dose as a function of energy in various materials: application to thermoluminescence (TL) dosimetry  

Microsoft Academic Search

The CEPXS\\/ONEDANT code package was used to produce a library of depth-dose profiles for monoenergetic electrons in various materials for energies ranging from 500keV to 5MeV in 10keV increments. The various materials for which depth-dose functions were derived include: lithium fluoride (LiF), aluminum oxide (Al2O3), beryllium oxide (BeO), calcium sulfate (CaSO4), calcium fluoride (CaF2), lithium boron oxide (LiBO), soft tissue,

E. C. Deogracias; J. L. Wood; E. C. Wagner; K. J. Kearfott

1999-01-01

72

Polynomial expressions of electron depth dose as a function of energy in various materials: application to thermoluminescence (TL) dosimetry  

Microsoft Academic Search

The CEPXS\\/ONEDANT code package was used to produce a library of depth–dose profiles for monoenergetic electrons in various materials for energies ranging from 500keV to 5MeV in 10keV increments. The various materials for which depth–dose functions were derived include: lithium fluoride (LiF), aluminum oxide (Al2O3), beryllium oxide (BeO), calcium sulfate (CaSO4), calcium fluoride (CaF2), lithium boron oxide (LiBO), soft tissue,

E. C Deogracias; J. L Wood; E. C Wagner; K. J Kearfott

1999-01-01

73

Dose to water versus dose to medium in proton beam therapy  

NASA Astrophysics Data System (ADS)

Dose in radiation therapy is traditionally reported as the water-equivalent dose, or dose to water. Monte Carlo dose calculations report dose to medium and thus a methodology is needed to convert dose to medium into dose to water (or vice versa) for comparison of Monte Carlo results with results from planning systems. This paper describes the development of a formalism to convert dose to medium into dose to water for proton fields when simulating the dose with Monte Carlo techniques. The conversion is based on relative stopping power but also considers energy transferred via nuclear interactions. The influence of different interaction mechanisms of proton beams (electromagnetic versus nuclear) is demonstrated. Further, an approximate method for converting doses retroactively is presented. Based on the outlined formalism, five proton therapy patients with a total of 33 fields were analyzed. Dose distributions, dose volume histograms and absolute doses to assess the clinical significance of differences between dose to medium and dose to water are presented. We found that the difference between the two dose reporting definitions can be up to 10% for high CT numbers if analyzing the mean dose to the target. The difference is clinically insignificant for soft tissues. For the structures analyzed, the mean dose to water could be converted to dose to medium by applying a correction factor increasing linearly with increasing average CT number in the volume. We determined that an approximate conversion method, done retroactively with an energy-independent stopping power ratio and without considering nuclear interaction events separately (as compared to on-the-fly conversion during simulation), is sufficiently accurate to compute mean doses. It is insufficient, however, when analyzing the beam range. For proton beams stopping in bony anatomy, the predicted beam range can differ by 2-3 mm when comparing dose to tissue and dose to water.

Paganetti, Harald

2009-07-01

74

Dose to water versus dose to medium in proton beam therapy.  

PubMed

Dose in radiation therapy is traditionally reported as the water-equivalent dose, or dose to water. Monte Carlo dose calculations report dose to medium and thus a methodology is needed to convert dose to medium into dose to water (or vice versa) for comparison of Monte Carlo results with results from planning systems. This paper describes the development of a formalism to convert dose to medium into dose to water for proton fields when simulating the dose with Monte Carlo techniques. The conversion is based on relative stopping power but also considers energy transferred via nuclear interactions. The influence of different interaction mechanisms of proton beams (electromagnetic versus nuclear) is demonstrated. Further, an approximate method for converting doses retroactively is presented. Based on the outlined formalism, five proton therapy patients with a total of 33 fields were analyzed. Dose distributions, dose volume histograms and absolute doses to assess the clinical significance of differences between dose to medium and dose to water are presented. We found that the difference between the two dose reporting definitions can be up to 10% for high CT numbers if analyzing the mean dose to the target. The difference is clinically insignificant for soft tissues. For the structures analyzed, the mean dose to water could be converted to dose to medium by applying a correction factor increasing linearly with increasing average CT number in the volume. We determined that an approximate conversion method, done retroactively with an energy-independent stopping power ratio and without considering nuclear interaction events separately (as compared to on-the-fly conversion during simulation), is sufficiently accurate to compute mean doses. It is insufficient, however, when analyzing the beam range. For proton beams stopping in bony anatomy, the predicted beam range can differ by 2-3 mm when comparing dose to tissue and dose to water. PMID:19550004

Paganetti, Harald

2009-06-23

75

Determination of the Absorbed Dose Rate to Water for the 18-mm Helmet of a Gamma Knife  

SciTech Connect

Purpose: To measure the absorbed dose rate to water of {sup 60}Co gamma rays of a Gamma Knife Model C using water-filled phantoms (WFP). Methods and Materials: Spherical WFP with an equivalent water depth of 5, 7, 8, and 9 cm were constructed. The dose rates at the center of an 18-mm helmet were measured in an 8-cm WFP (WFP-3) and two plastic phantoms. Two independent measurement systems were used: one was calibrated to an air kerma (Set I) and the other was calibrated to the absorbed dose to water (Set II). The dose rates of WFP-3 and the plastic phantoms were converted to dose rates for an 8-cm water depth using the attenuation coefficient and the equivalent water depths. Results: The dose rate measured at the center of WFP-3 using Set II was 2.2% and 1.0% higher than dose rates measured at the center of the two plastic phantoms. The measured effective attenuation coefficient of Gamma Knife photon beam in WFPs was 0.0621 cm{sup -1}. After attenuation correction, the difference between the dose rate at an 8-cm water depth measured in WFP-3 and dose rates in the plastic phantoms was smaller than the uncertainty of the measurements. Conclusions: Systematic errors related to the characteristics of the phantom materials in the dose rate measurement of a Gamma Knife need to be corrected for. Correction of the dose rate using an equivalent water depth and attenuation provided results that were more consistent.

Chung, Hyun-Tai [Department of Neurosurgery, Seoul National University College of Medicine, Seoul (Korea, Republic of); Park, Youngho [Department of Mechanical Engineering, Chonnam National University, Gwangju (Korea, Republic of); Hyun, Sangil [Nanotechnology Lab, Korea Institute of Ceramic Engineering and Technology, Seoul (Korea, Republic of); Choi, Yongsoo [Faculty of Liberal Arts and Basic Science, Hankyung National University, Anseong (Korea, Republic of); Kim, Gi Hong [Department of Neurosurgery, Yonsei University Severance Hospital, Seoul (Korea, Republic of); Kim, Dong Gyu [Department of Neurosurgery, Seoul National University College of Medicine, Seoul (Korea, Republic of); Chun, Kook Jin, E-mail: chunkj@kriss.re.k [Center for Ionizing Radiation, Korea Research Institute of Standards and Science, Daejon (Korea, Republic of); Department of Neurosurgery, Seoul National University College of Medicine, Seoul (Korea, Republic of)

2011-04-01

76

Depth of penetration of bubbles entrained by a plunging water jet  

Microsoft Academic Search

A model is proposed to predict the depth of penetration of the air bubbles entrained by a round water jet impacting into a flat, liquid pool. This depth is shown to be determined only by the initial jet momentum and by the non-monotonic nature of the bubble terminal velocities as a function of their size. The model is shown to

Christophe Clanet; Juan C. Lasheras

1997-01-01

77

Interpretation of AMSU microwave measurements for the retrievals of snow water equivalent and snow depth  

Microsoft Academic Search

The objective of this paper is to interpret microwave scattering signatures over snow cover as observed by the Advanced Microwave Sounding Unit (AMSU) for the retrievals of snow water equivalent and snow depth. A case study involving seasonal snow cover over the U.S. Great Plains was analyzed in detail. Area-wide analysis of the relationship between snow depth and the AMSU

Cezar Kongoli; Norman C. Grody; Ralph R. Ferraro

2004-01-01

78

Feeling Pressured: Water Pressure and Depth (title provided or enhanced by cataloger)  

NSDL National Science Digital Library

These two activities illustrate the relationship between water pressure and depth. They offer students an exploration of the relationship between pressure and depth, an opportunity to construct an experimental apparatus, experience in taking measurements with the apparatus, and an introduction to the impact of pressure on the lungs.

79

Depth colonization of eelgrass ( Zostera marina ) and macroalgae as determined by water transparency in Danish coastal waters  

Microsoft Academic Search

We present a comparative analysis of lower depth limits for growth of eelgrass, large brown algae and other macroalgae measured\\u000a by SCUBA-diving along 162 transects in 27 Danish fjords and coastal waters, coupled to 1,400 data series of water chemistry\\u000a (especially nitrogen) and Secchi depth transparency collected between March and October. Danish coastal waters are heavily\\u000a eutrophied and characterized by

Søren Laurentius Nielsen; Kaj Sand-Jensen; Jens Borum; Ole Geertz-Hansen

2002-01-01

80

The depth of feed water influences maximum discharge-pressure of hot water geothermal wells  

SciTech Connect

The maximum wellhead pressure at which hot water wells discharge is an important parameter for geothermal power and as it slowly declines with years of exploitation presents a moving target for project designers. It can also decrease rapidly for newly closed-in wells (within days or even hours) to a point at which auto-discharge is impossible and tedious techniques have to be employed to restart flow. The common cause of this phenomenon is reduction in the temperature of the hot water feeding the well; in the former case is the result of a general decline in the reservoir water enthalpy, and in the latter is due to cooler denser water from higher in the uncased part of the well percolating down and flooding the lower more permeable levels from which a discharging well mainly draws its fluids. The inter-relationship of feed water temperature, depth and maximum discharging-pressure is determined in this study with illustrated examples demonstrating application.

James, Russell

1988-01-01

81

Plant species distribution in relation to water-table depth and soil ...  

Treesearch

International Institute of Tropical Forestry ... Title: Plant species distribution in relation to water-table depth and soil redox potential in ... riparian plant communities¡ªdefined as wet, moist, and dry meadow¡ªalong short topographic gradients.

82

Is topsoil water repellency a mechanism for improving water conservation in depth?  

NASA Astrophysics Data System (ADS)

Soil water repellency (WR) is widespread in forest soils under different climatic conditions, soil types and vegetation covers (Doerr et al., 2000). It is normally characterized by a high spatial variability in persistence, showing wettable and water repellent patches. This phenomenon has a special interest in semiarid areas, such as the Mediterranean ecosystems, where water resources are limited. For that reason, it is thought to be a possible mechanism for improving water conservation in soil profile, which would minimize evaporation losses from the soil surface (Doerr et al., 2000; Robinson et al. 2010). The ecological function of having a patchy hydrophobic surface might be the means of transporting water deeper into the soil profile and away from surface evaporation. In addition, it may also inhibit the growth of other vegetal species. This could increase the resistance of plants to drought by increasing water availability through reducing losses to surface evaporation or other plants. Our aim was to test the hypothesis that soil WR improves the water conservation within the soil. We have compared the temporal evolution of soil moisture between samples with repellent and wettable layers. Repellent and wettable soil samples were collected from an agricultural area in Biar (Alicante, Spain). Samples were put in 100ml plastic pots (n=30). Each one had two layers (WR and wettable or both wettable) with depth around 2.5cm for superficial and 3.5cm for deeper wettable horizon. We measured the evolution under different initial conditions of soil water content (around 20% and 9%) and soil superficial WR persistence (wettable, slight, strong and severe soil (n=5 per treatment)). Pots were kept under laboratory conditions (between 30-50% of relative air humidity and ? 20°C). Soil water content was controlled daily by weight measurement. Our results showed a clear significant difference in evaporation rates, which were higher in samples with a wettable superficial layer. However, differences in evaporation rates were not significant between samples with different WR levels of persistence nor between samples with different initial water content. Our preliminary results indicated that soil WR is a mechanism which clearly contributes to the conservation of moisture in depth, making more sense of the hypothesis of a possible ecological strategy for plants. Keywords: Soil water repellency, hydrophobicity. References: Doerr, S.H., Shakesby, R.A., Walsh, R.P.D., 2000. Soil water repellency: its causes, characteristics and hydro-geomorphological significance. Earth-Sci. Rev. 51, 33-65. Robinson D.A., Lebron I., Ryel R.J., Jones S.B., 2010. Soil Water Repellency: A Method of Soil Moisture Sequestration in Pinyon-Juniper Woodland Soil Science Society of America Journal 74 (2), 624-634. Rodriguez-Iturbe, I., 2000. Ecohydrology: a hydrologic perspective of climate-soil-vegetation dynamics. Water Resour. Res., 36 (1), 3-9.

Lozano, Elena; Jiménez-Pinilla, Patricia; Mataix-Solera, Jorge; Arcenegui, Vicky; Mataix-Beneyto, Jorge

2013-04-01

83

Evaluation of target dose based on water-equivalent thickness in external beam radiotherapy  

PubMed Central

In vivo dosimetry was carried out for 152 patients receiving external beam radiotherapy and the treatment sites were divided into two main groups: Thorax, Abdomen, and Pelvic (120 fields) and Head and Neck (52 fields). Combined entrance and exit dose measurements were performed using LiF: Mg, Cu, P thermoluminescent dosimeters (TLDs). Water-equivalent (effective) thicknesses and target dose were evaluated using dose transmission data. The ratio of measured to expected value for each quantity was considered as an indicator for the accuracy of the parameter. The average ratio of the entrance dose was evaluated as 1.01 ± 0.07. In the diameter measurement, the mean ratio of effective depth divided by the contour depth is 1.00 ± 0.13 that shows a wide distribution which reflects the influence of contour inaccuracies as well as tissue inhomogeneities. At the target level, the mean ratio of measured to the prescribed dose is 1.00 ± 0.07. According to our findings, the difference between effective depth and patient depth has a direct relation to target dose discrepancies. There are some inevitable sources which may cause the difference. Evaluation and application of effective diameter in treatment calculations would lead to a more reliable target dose, especially for fields which involve Thorax, Abdomen, and Pelvic.

Moghaddam, Behnaz Ghanbar; Vahabi-Moghaddam, Masoud; Sadremomtaz, Alireza

2013-01-01

84

Improving secondary ion mass spectrometry C60(n+) sputter depth profiling of challenging polymers with nitric oxide gas dosing.  

PubMed

Organic depth profiling using secondary ion mass spectrometry (SIMS) provides valuable information about the three-dimensional distribution of organic molecules. However, for a range of materials, commonly used cluster ion beams such as C60(n+) do not yield useful depth profiles. A promising solution to this problem is offered by the use of nitric oxide (NO) gas dosing during sputtering to reduce molecular cross-linking. In this study a C60(2+) ion beam is used to depth profile a polystyrene film. By systematically varying NO pressure and sample temperature, we evaluate their combined effect on organic depth profiling. Profiles are also acquired from a multilayered polystyrene and polyvinylpyrrolidone film and from a polystyrene/polymethylmethacrylate bilayer, in the former case by using an optimized set of conditions for C60(2+) and, for comparison, an Ar2000(+) ion beam. Our results show a dramatic improvement for depth profiling with C60(2+) using NO at pressures above 10(-6) mbar and sample temperatures below -75 °C. For the multilayered polymer film, the depth profile acquired using C60(2+) exhibits high signal stability with the exception of an initial signal loss transient and thus allows for successful chemical identification of each of the six layers. The results demonstrate that NO dosing can significantly improve SIMS depth profiling analysis for certain organic materials that are difficult to analyze with C60(n+) sputtering using conventional approaches/conditions. While the analytical capability is not as good as large gas cluster ion beams, NO dosing comprises a useful low-cost alternative for instruments equipped with C60(n+) sputtering. PMID:23590425

Havelund, R; Licciardello, A; Bailey, J; Tuccitto, N; Sapuppo, D; Gilmore, I S; Sharp, J S; Lee, J L S; Mouhib, T; Delcorte, A

2013-05-08

85

Antelope Valley-East Kern Water Agency area, California, showing ground-water subunits and areas, location of wells, and lines of equal depth to water  

USGS Publications Warehouse

The U.S. Geological Survey has released to the open file a map showing ground-water subunits and areas, and depth to water for spring 1978, in the Antelope Valley-East Kern Water Agency area, California.

Blankenbaker, G. G.

1978-01-01

86

Neutron Reflection and Flux Versus Depth for Aluminum with an Appendix. Neutron Dose Transmission Versus Thickness.  

National Technical Information Service (NTIS)

Detailed calculated results of neutron reflection and flux versus depth for aluminum are given in the form of machine printouts. The angular and energy distributions of the reflected neutrons along with the energy-dependent and total flux at various depth...

F. J. Allen A. T. Futterer W. P. Wright

1964-01-01

87

Evidence of high natural radiation doses in certain mid-water oceanic organisms  

SciTech Connect

Concentrations of the naturally occurring radioactive nuclide polonium-210 were determined in mid-water crustaceans and fish from depths to 1500 meters. Unusually high levels were found in certain categories of organisms, indicating that these organisms were exposed to a particularly high natural radiation dose. The results have implications in terms of possible radiation effects, as a baseline against which artificial radioactive nuclides can be compared, and as a potential technique for studying the feeding behavior of mid-water organisms.

Cherry, R.D.; Heyraud, M.

1982-10-01

88

Experimental verification of improved depth-dose distribution using hyper-thermal neutron incidence in neutron capture therapy.  

PubMed

We have proposed the utilization of 'hyper-thermal neutrons' for neutron capture therapy (NCT) from the viewpoint of the improvement in the dose distribution in a human body. In order to verify the improved depth-dose distribution due to hyper-thermal neutron incidence, two experiments were carried out using a test-type hyper-thermal neutron generator at a thermal neutron irradiation field in Kyoto University Reactor (KUR), which is actually utilized for NCT clinical irradiation. From the free-in-air experiment for the spectrum-shift characteristics, it was confirmed that the hyper-thermal neutrons of approximately 860 K at maximum could be obtained by the generator. From the phantom experiment, the improvement effect and the controllability for the depth-dose distribution were confirmed. For example, it was found that the relative neutron depth-dose distribution was about 1 cm improved with the 860 K hyper-thermal neutron incidence, compared to the normal thermal neutron incidence. PMID:11197667

Sakurai, Y; Kobayashi, T

2001-01-01

89

CALIBRATION OF THE ABSORBED DOSE PRODUCED IN WATER BY BETATRON ELECTRONS WITH THE BENZOIC-ACID DOSIMETER  

Microsoft Academic Search

The benzoic acid dosimeter was used to determine the absorbed dose rate ; produced by betatron electrons at the depth of relative maximum dose in water. ; These measurements were related to the conventional and arbitrary specification ; of betatron electron exposure in terms of the reading of a Victoreen thimble ; chamber inserted in a polystyrene block. Chemical yield

N. F. Barr; M. B. Stark; J. S. Laughlin

1962-01-01

90

New shallow water table depth algorithm in SWAT2005: recent modifications  

Technology Transfer Automated Retrieval System (TEKTRAN)

The proximity of the shallow water table depth (wtd) to the soil surface impacts agricultural production, farm machine trafficability, and water quality due to agricultural chemical transport and soil salinity. Therefore, it is essential for hydrologic models to accurately simulate wtd. Recently, an...

91

Passive remote sensing techniques for mapping water depth and bottom features.  

PubMed

Ratio processing methods are reviewed, and a new method is proposed for extracting water depth and bottom type information from passive multispectral scanner data. Limitations of each technique are discussed, and an error analysis is performed using an analytical model for the radiance over shallow water. PMID:20174418

Lyzenga, D R

1978-02-01

92

STUDY OF WATER BOLUS EFFECT ON SAR PENETRATION DEPTH AND EFFECTIVE FIELD SIZE FOR LOCAL HYPERTHERMIA  

Microsoft Academic Search

Abstract—Water bolus is used in microwave hyperthermia of cancer treatment to control the body surface temperature. In this paper the effect of water bolus on SAR distribution is investigated in the muscle layer of a three layered tissue model. Both the SAR penetration depth and the effective field size (EFS) are computed and compared in presence and in absence of

Mohammad Ali Ebrahimi-Ganjeh; Amir R. Attari

2008-01-01

93

Breaking probabilities for dominant surface waves on water of finite constant depth  

NASA Astrophysics Data System (ADS)

This paper extends our previous study of the breaking probability of dominant deep water gravity surface waves into the finite water depth environment. It reports a unified behavior of the mean breaking statistics once the effects of finite water depth are taken into account. The shallow water wave data that form the basis of this study were acquired at a field experiment site at Lake George, New South Wales, Australia. The breaking events were detected through visual observation of videotaped records of the wave field in combination with acoustic signatures of the breaking waves from a collocated hydrophone. Following Banner et al. [2000], we argue that when constant finite depth bottom influence is operative, nonlinear hydrodynamical effects associated with energy and momentum fluxes within deforming wave groups remain the primary determinant of breaking onset. This underpins our proposed finite depth water parameterization for the environmental dependence of dominant wave breaking probability, given by the average number of breakers passing a fixed point per dominant wave period. The additional influence of bottom interaction with the wind drift current shear and wind forcing are also included in our finite constant depth formulation. This is a natural extension of our recently proposed deep water dependence and reduces to it as the significant wave height becomes much smaller than the water depth. In common with the deep water case we propose that there exists a threshold of the significant peak steepness below which negligible dominant wave breaking occurs. The available data show encouraging agreement with our proposed dependence, with a correlation coefficient approaching 0.9.

Babanin, Alexander V.; Young, Ian R.; Banner, Michael L.

2001-06-01

94

Rooting depth and soil water extraction patterns of different crops in a silty loam Haplustoll  

Microsoft Academic Search

This study was carried out: (i) to estimate from soil water depletion curves the apparent rooting depth (RD) for several crops; (ii) to calculate the soil water extraction parameters; and (iii) to compare inter- and intraspecific differences in the water extraction parameters. Experiments were conducted at the Manfredi Experimental Station (INTA), Argentina (31°49?S, 63°48?W), and at the Institute of Phytopathology

J. L. Dardanelli; O. A. Bachmeier; R. Sereno; R. Gil

1997-01-01

95

Study and Application of In-depth Water Control Technology for Production Wells  

Microsoft Academic Search

In view of low oil increment and short valid period of conventional water shutoff for production well, the authors propose and develop a new in-depth water control technology for production well. The different-strength (from weak to strong) water shutoff agents are separately injected into a remote zone, transition zone, and near-wellbore zone in this technology, which can achieve the aim

D. Caili; Y. Qing; G. Qilin; Z. Fulin

2011-01-01

96

Arsenic-Related Water Quality with Depth and Water Quality of Well-Head Samples from Production Wells, Oklahoma, 2008.  

National Technical Information Service (NTIS)

This report presents the results of an investigation that used the USGS well profiler to describe arsenic-related water quality with depth in two production wells in an attempt to identify zones yielding water with high arsenic concentrations. This report...

C. J. Becker J. R. Greer K. A. Smith S. J. Smith

2010-01-01

97

Effect of seedling age and water depth on morphological and physiological aspects of transplanted rice under high temperature  

Microsoft Academic Search

To study the effect of high temperature, rice seedlings 20, 30, 40 and 50 d were kept at 5, 10, 15 and 20 cm water depth in a water pool. Meteorological findings indicated that water temperature varied up to 10 cm but became stable below this depth. Deep water inflicted higher tiller mortality, minimal increase in dry weight of aerial

KHAKWANI Abdul Aziz; SHIRAISHI Masaaki; ZUBAIR Muhammad; BALOCH Mohammad Safdar; NAVEED Khalid; AWAN Inayatullah

98

Optimization of coagulant dosing process in water purification system  

Microsoft Academic Search

In the water purification plant, chemicals are injected for quick purification of raw water. The amount of chemicals intrinsically depends on the water quality such as turbidity, temperature, pH and alkalinity, etc. This paper presents the method of deriving the optimum dosing rate of coagulant in water purification system. A fuzzy model for normal condition and a neural network model

Tae-Hwan Han; Eui-Suck Nahm; Kwang-Bang Woo; C. J. Kim; Jeong-Woong Ryu

1997-01-01

99

Application of flowmeter and depth-dependent water quality data for improved production well construction  

USGS Publications Warehouse

Ground water production wells commonly are designed to maximize well yield and, therefore, may be screened over several water-bearing zones. These water-bearing zones usually are identified, and their hydrogeologic characteristics and water quality are inferred, on the basis of indirect data such as geologic and geophysical logs. Production well designs based on these data may result in wells that are drilled deeper than necessary and are screened through zones having low permeability or poor-quality ground water. In this study, we examined the application of flowmeter logging and depth-dependent water quality samples for the improved design of production wells in a complex hydrogeologic setting. As a demonstration of these techniques, a flowmeter log and depth-dependent water quality data were collected from a long-screened production well within a multilayered coastal aquifer system in the Santa Clara-Calleguas Basin, Ventura County, California. Results showed that the well yields most of its water from four zones that constitute 58% of the screened interval. The importance of these zones to well yield was not readily discernible from indirect geologic or geophysical data. The flowmeter logs and downhole water quality data also show that small quantities of poor-quality water could degrade the overall quality of water from the well. The data obtained from one well can be applied to other proposed wells in the same hydrologic basin. The application of flowmeter and depth-dependent water quality data to well design can reduce installation costs and improve the quantity and quality of water produced from wells in complex multiple-aquifer systems.

Gossell, M. A.; Nishikawa, T.; Hanson, R. T.; Izbicki, J. A.; Tabidian, M. A.; Bertine, K.

1999-01-01

100

Investigation on optimization design of equivalent water depth truncated mooring system  

NASA Astrophysics Data System (ADS)

The oil industry is now increasingly concentrating their efforts and activities in connection with developing fields in deeper waters, ranging typically from 500 m to 3000 m worldwide. However, the modeling of a full-depth system has become difficult presently; no tank facility is sufficiently large to perform the testing of a complete FPS with compliant mooring in 1000 m to 3000 m depth, within reasonable limits of model scale. Until recently, the most feasible procedure to meet this challenge seems to be the so-called “hybrid model testing technique”. To implement this technique, the first and important step is to design the equivalent water depth truncated mooring system. In this work, the optimization design of the equivalent water depth truncated mooring system in hybrid model testing for deep sea platforms is investigated. During the research, the similarity of static characteristics between the truncated and full depth system is mainly considered. The optimization mathematical model for the equivalent water depth truncated system design is set up by using the similarity in numerical value of the static characteristics between the truncated system and the full depth one as the objective function. The dynamic characteristic difference between the truncated and full depth mooring system can be minished by selecting proper design rule. To calculate the static characteristics of the mooring system, the fourth order Runge-Kutta method is used to solve the static equilibrium equation of the single mooring line. After the static characteristic of the single mooring line is calculated, the static characteristic of the whole mooring system is calculated with Lagrange numerical interpolation method. The mooring line material database is established and the standard material name and the diameter of the mooring line are selected as the primary key. The improved simulated annealing algorithm for continual & discrete variables and the improved complex algorithm for discrete variables are employed to perform the optimization calculation. The C++ programming language is used to develop the computer program according to the object-oriented programming idea. To perform the optimization calculation with the two algorithms mentioned above respectively and the better result is selected as the final one. To examine the developed program, an example of equivalent water depth truncated mooring system optimum design calculation on a 100,000-t, turret mooring FPSO in water depth of 320 m are performed to obtain the conformation parameters of the truncated mooring system, in which the truncated water depth is 160 m. The model test under some typical environment conditions are performed for both the truncated and the full depth system with model scale factor ?=80. After comparing the corresponding results from the test of the truncated system with those from the full depth system test, it’s found that the truncated mooring system design in this work is successful.

Zhang, Huoming; Sun, Zhilin; Yang, Jianmin; Gao, Mingzheng

2009-02-01

101

Depth dose distribution measurement on the Foton-M2 bio-satellite by TLD technique  

NASA Astrophysics Data System (ADS)

In the framework of “Biology and Physics in Space” project of the European Space Agency (ESA), a returning satellite, Foton-M2, carried an open-to-space sample holder outside of the satellite body, called as BIOPAN-5, loaded with exo-biological experiments and dosemeters for RAdiation DOsimetry (RADO). One of the RADO experiments (Teflon TLD) was dedicated to dose distribution measurements of the cosmic radiation by thermo-luminescent (TL) technique. It was found that the maximum surface absorbed dose rate, averaged over the first ˜8 mg/cm2 thickness, was ˜2 Gy/d and showed a location dependence due the shading effect of the satellite construction elements. The dose rate decreased nearly by 3 orders of magnitude below 500 mg/cm2.

Fehér, I.; Pálfalvi, J. K.

2008-09-01

102

Simplified Volume-Area-Depth Method for Estimating Water Storage of Isolated Prairie Wetlands  

Microsoft Academic Search

There are millions of wetlands in shallow depressions on the North American prairies but the quantity of water stored in these depressions remains poorly understood. Hayashi and van der Kamp (2000) used the relationship between volume (V), area (A) and depth (h) to develop an equation for estimating wetland storage. We tested the robustness of their full and simplified V-A-h

A. G. Minke; C. J. Westbrook; G. van der Kamp

2009-01-01

103

DYNAMICS OF A SUBTIDAL SEAGRASS LANDSCAPE: SEASONAL AND ANNUAL CHANGE IN RELATION TO WATER DEPTH  

EPA Science Inventory

The spatial heterogeneity of a subtidal marine landscape and the areal extent of both monospecific and mixed patches of seagrass species were studied in Tampa Bay, FL. Specifically, we examined the temporal dynamics of seagrass distribution and its relationship to water depth an...

104

Performance study of the inverted absorber solar still with water depth and total dissolved solid  

Microsoft Academic Search

In this communication, an experimental study of inverted absorber solar still (IASS) and single slope solar still (SS) at different water depth and total dissolved solid (TDS) is presented. Experiments are conducted for the climatic condition of Muscat, Oman. A thermal model is also developed for the IASS and validated with experimental results. A fair agreement is found for the

Rahul Dev; Sabah A. Abdul-Wahab; G. N. Tiwari

2011-01-01

105

Effect of Mixing Depth and Turbidity on the Productivity of Fresh-Water Impoundments  

Microsoft Academic Search

Mixing depth and turbidity negatively affect the productivity of an aquatic environment through the control they exert on the effective energy available for photosynthesis. A feedback equation is developed that defines the interaction of these two quantities with the production by phytoplankton. The equation permits calculation of the relative productivity of any body of water provided nutrients are assumed adequate,

Garth I. Murphy

1962-01-01

106

The influence of convective flow on rhizome length in Typha domingensis over a water depth gradient  

Microsoft Academic Search

We present direct evidence for an ecological role of convective flow in the emergent macrophyte Typha domingensis Pers. A pond experiment was conducted to examine the influence of convective flow on rhizome length at water depths ranging from 5 to 65cm. The leaves of half of the plants were pierced while the remaining plants were used as a control. Leaf

Sean D. White; George G. Ganf

1998-01-01

107

The role of water depth and soil temperature in determining initial composition of prairie wetland coenoclines  

Microsoft Academic Search

In this study, we examined the effects of water depth and temperature on seedling recruitment from a prairie wetland seed bank. We collected seed-bank samples from natural and restored prairie pothole wetlands in northwestern Iowa and combined them into a single sample. We examined seedling recruitment from this seed-bank sample in an experimental study using a factorial design of 4

Eric W. Seabloom; Arnold G. van der Valk; Kirk A. Moloney

1998-01-01

108

On scattering and radiation problem for a cylinder in water of finite depth  

Microsoft Academic Search

Wave loadings due to scattering and radiation for a floating vertical circular cylinder in water of finite depth are derived. These are derived from the total velocity potential which can be decomposed as four velocity potentials; one due to scattering in the presence of an incident wave on fixed structure (diffraction problem), and the other three due to radiation respectively

D. D. Bhatta; M. Rahman

2003-01-01

109

Market depth in an illiquid market: applying the VNET concept to Victorian water markets  

Microsoft Academic Search

In the context of highly liquid markets and intra-day data, Engle and Lange (2001) successfully develop a measure of market depth they call VNET. This article explores the applicability of a modified version of this measure in the case of the weekly market for seasonal water in rural Victoria. The modified VNET measure is found to be successful in this

Robert Brooks; Edwyna Harris; Yovina Joymungul

2009-01-01

110

Seismic evidence of negligible water carried below 400-km depth in subducting lithosphere.  

PubMed

Strong evidence exists that water is carried from the surface into the upper mantle by hydrous minerals in the uppermost 10-12?km of subducting lithosphere, and more water may be added as the lithosphere bends and goes downwards. Significant amounts of that water are released as the lithosphere heats up, triggering earthquakes and fluxing arc volcanism. In addition, there is experimental evidence for high solubility of water in olivine, the most abundant mineral in the upper mantle, for even higher solubility in olivine's high-pressure polymorphs, wadsleyite and ringwoodite, and for the existence of dense hydrous magnesium silicates that potentially could carry water well into the lower mantle (deeper than 1,000?km). Here we compare experimental and seismic evidence to test whether patterns of seismicity and the stabilities of these potentially relevant hydrous phases are consistent with a wet lithosphere. We show that there is nearly a one-to-one correlation between dehydration of minerals and seismicity at depths less than about 250?km, and conclude that the dehydration of minerals is the trigger of instability that leads to seismicity. At greater depths, however, we find no correlation between occurrences of earthquakes and depths where breakdown of hydrous phases is expected. Lastly, we note that there is compelling evidence for the existence of metastable olivine (which, if present, can explain the distribution of deep-focus earthquakes) west of and within the subducting Tonga slab and also in three other subduction zones, despite metastable olivine being incompatible with even extremely small amounts of water (of the order of 100?p.p.m. by weight). We conclude that subducting slabs are essentially dry at depths below 400?km and thus do not provide a pathway for significant amounts of water to enter the mantle transition zone or the lower mantle. PMID:20927105

Green, Harry W; Chen, Wang-Ping; Brudzinski, Michael R

2010-10-03

111

Monte Carlo calculations of monoenergetic electron depth dose distributions in LiF chips: Skin dose correction factors for beta rays  

SciTech Connect

Monte Carlo calculations have been carried out for monoenergetic electrons from 0.1 to 4 MeV irradiating LiF chips in both perpendicular and isotropic geometry. This enabled the calculation of skin dose correction factors (beta factors) for typical beta energy spectra as measured with a beta-ray spectrometer at CANDU nuclear generating stations. The correction factors were estimated by averaging the depth dose distributions for the monoenergetic electrons over the experimentally measured beta-ray spectra. The calculations illustrate the large uncertainty in beta factors arising from the unknown angular distribution of the beta-ray radiation field and uncertainties in the shape of the beta-ray spectra below 500 keV. 28 refs., 8 figs., 2 tabs.

Horowitz, Y.S. [Ben Gurion Univ. of the Negev, Beersheva (Israel); Hirning, C.R. [Ontario Hydro, Whitby (Canada); Yuen, P.; Wong, P. [Chalk River Labs., Ontario (Canada)

1994-10-01

112

DS86 neutron dose: Monte Carlo analysis for depth profile of 152Eu activity in a large stone sample.  

PubMed

The depth profile of 152Eu activity induced in a large granite stone pillar by Hiroshima atomic bomb neutrons was calculated by a Monte Carlo N-Particle Transport Code (MCNP). The pillar was on the Motoyasu Bridge, located at a distance of 132 m (WSW) from the hypocenter. It was a square column with a horizontal sectional size of 82.5 cm x 82.5 cm and height of 179 cm. Twenty-one cells from the north to south surface at the central height of the column were specified for the calculation and 152Eu activities for each cell were calculated. The incident neutron spectrum was assumed to be the angular fluence data of the Dosimetry System 1986 (DS86). The angular dependence of the spectrum was taken into account by dividing the whole solid angle into twenty-six directions. The calculated depth profile of specific activity did not agree with the measured profile. A discrepancy was found in the absolute values at each depth with a mean multiplication factor of 0.58 and also in the shape of the relative profile. The results indicated that a reassessment of the neutron energy spectrum in DS86 is required for correct dose estimation. PMID:10494148

Endo, S; Iwatani, K; Oka, T; Hoshi, M; Shizuma, K; Imanaka, T; Takada, J; Fujita, S; Hasai, H

1999-06-01

113

Spectral model of depth-integrated water column photosynthesis and its inhibition by ultraviolet radiation  

NASA Astrophysics Data System (ADS)

Depth-integrated models of primary production (DIMs) are used to estimate water column photosynthesis as a function of chlorophyll concentration, irradiance at the surface, the penetration of photosynthetically available radiation (PAR), and parameters of the relationship between photosynthesis and PAR. These models are inherently unable to account for variability in the ratio of photosynthetically utilizable radiation (PUR) to PAR with depth and water type, and they cannot account for the inhibition of photosynthesis by ultraviolet radiation, UVR. These important spectral effects — all sensitive to climate change — are readily described with numerical models that require many computations and are unsuitable for some important applications, including the estimation of aquatic productivity from remote sensing. We present a simple DIM that accounts for the spectral effects of irradiance on photosynthesis, including inhibition by UVR. Water column photosynthesis, normalized to surface chlorophyll and scaled to the maximum rate per unit chlorophyll, is described as a function of four dimensionless derived variables:E*PUR, PUR at the surface scaled to the saturation irradiance for photosynthesis; T*PUR, water transparency, normalized to a depth scale and weighted spectrally for photosynthetic absorption; E*PIR, surface irradiance weighted spectrally for inhibition of photosynthesis; and T*PIR, scaled transparency weighted for photosynthesis-inhibiting radiation. Simple functions of these variables closely approximate (within 6%) the results of a full-spectral numerical model of instantaneous and daily integrated water column photosynthesis with and without UVR for a broad range of water types, solar angles, stratospheric ozone concentrations and biological properties of phytoplankton. The spectral DIM is suitable for examining patterns in global ocean productivity and can be used to assess the biological effects of variations in solar radiation (e.g., ozone depletion) and water clarity in climate-change scenarios for lakes and oceans.

Cullen, John J.; Davis, Richard F.; Huot, Yannick

2012-03-01

114

Depth profile study of Ti implanted Si at very high doses  

NASA Astrophysics Data System (ADS)

A detailed study on the resulting impurity profile in Si samples implanted with high doses of Ti and subsequently annealed by pulsed-laser melting (PLM) is reported. Two different effects are shown to rule the impurity profile redistribution during the annealing. During the melting stage, the thickness of the implanted layer increases while the maximum peak concentration decreases (box-shaped effect). On the contrary, during the solidifying stage, the thickness of the layer decreases and the maximum peak concentration increases (snow-plow effect). Both effects are more pronounced as the energy density of the annealing increases. Moreover, as a direct consequence of the snow-plow effect, part of the impurities is expelled from the sample through the surface.

Olea, J.; Pastor, D.; Toledano-Luque, M.; Mártil, I.; González-Díaz, G.

2011-09-01

115

Upscaling of annual mean and dynamics of water table depth in German organic soils  

NASA Astrophysics Data System (ADS)

Water table depth is the key parameter controlling the fluxes of CO2, CH4 and N2O from organic soils (peatlands and other organic soils). Therefore, a good estimation of the spatial distribution of water table depth is crucial in any upscaling approach for these greenhouse gases (GHGs). It is further the prerequisite to assess the effects of re-wetting measures. There are attempts to obtain maps of water table depth at large scales (e.g. national or continental) by using process-based hydrological model concepts. However, major problem of the process-based approach is the representation of the water management (ditches, tile drains, pumping and weir management), which is at the best known spatially just for the ditch patterns. Thus, this approach is hardly applicable to the diversely-drained and -used organic soils in central Europe. Here, we present an alternative, data-driven approach for upscaling annual mean and dynamics of water table depth in organic soils. Groundwater level data of a unique dataset from about 60 peatlands, 1100 dipwells and around 8000 annual data sets, is the basis of this approach. Time series were used to calculate long-term annual means, average annual amplitudes and ponding durations. In case of continuous observations, shape parameters of the annual frequency distribution of water table depths were calculated. For each well, numerous site characteristics were collected as possible explanatory variables. This collection was restricted to nationally-available data. For each dipwell, land use is taken from official land use maps (German database ATKIS), and the soil type from the national geological map (1:200.000). In case of reliable site information, maps were corrected accordingly. Additionally, from these maps, topological indicators such as the ditch distance and density, the distance to the edge of the peatland and the peatland area within different buffers were calculated. Meteorological data (precipitation, potential evapotranspiration and climatic water balance) was extracted from gridded data (1x1 km) from the German Weather Service. Topographic indices were calculated using the national digital elevation model. Further, protection status (nature reserves, Natura2000, etc.) and peatland type was collected for each well. We use two data-driven models (fuzzy-logic and boosted regression trees) to analyze the influence of the site characteristics on the various water table depth target variables (mean, amplitude, etc.). First results using the fuzzy-logic approach show that a land use/vegetation and protection status categorization of the data combined with separate fuzzy models for each category can explain substantial parts of the variance seen in the data set. Variables with strong explaining power were meteorological (summer precipitation and/or climatic water balance) and topological parameters of the ditch network and the peatland body. Uncertainty of the models is evaluated using cross-validation. Models are applied with nationally-available data to generate maps of statistical measures of water table depth for the German organic soils.

Bechtold, Michel; Tiemeyer, Bärbel; Belting, Susanne; Laggner, Andreas; Leppelt, Thomas; Frahm, Enrico; Freibauer, Annette

2013-04-01

116

Coupled discontinuous and continuous Galerkin finite element methods for the depth-integrated shallow water equations  

Microsoft Academic Search

In this paper, we investigate a new approach for the two-dimensional fully non-linear depth-averaged shallow water equations by coupling continuous and discontinuous Galerkin methods. We apply a discontinuous Galerkin method to the primitive continuity and momentum equations and couple this to a continuous method discretizing the so-called “wave continuity” and momentum equation. Herein we present the formulation and derive an

Clint Dawson; Jennifer Proft

2004-01-01

117

Earthquakes induced by water injection at ?3 km depth within the Rongchang gas field, Chongqing, China  

Microsoft Academic Search

Unwanted water, amounting more than 1 million m3, has been injected intermittently at a pumping pressure of 2.1–2.9 MPa (over hydrostatic) at 2.6–2.9 km depth within the Rongchang gas field, western Chongqing, China, since July 1988. The injections have induced more than 32,000 surface-recorded earthquakes, including 2 of ML ? 5, 14 of ML ? 4, and more than 100

Xinglin Lei; Guozheng Yu; Shengli Ma; Xueze Wen; Qiang Wang

2008-01-01

118

Mineral nutrients in floodwater and floating rice growing at water depths up to two metres  

Microsoft Academic Search

Concentrations of N, P and K were measured in floodwater and in floating rice cultivars growing at up to 2m water depths in\\u000a the central flood plain of Thailand. Concentrations of N, P and K in floodwater were often higher than those reported for\\u000a oligotrophic lakes, nevertheless the floodwater contained 4–45 times less K and 15–90 times less N than

T. L. Setter; T. Kupkanchanakul; L. Pakinnaka; Y. Aguru; H. Greenway

1987-01-01

119

Investigation on optimization design of equivalent water depth truncated mooring system  

Microsoft Academic Search

The oil industry is now increasingly concentrating their efforts and activities in connection with developing fields in deeper\\u000a waters, ranging typically from 500 m to 3000 m worldwide. However, the modeling of a full-depth system has become difficult\\u000a presently; no tank facility is sufficiently large to perform the testing of a complete FPS with compliant mooring in 1000\\u000a m to

Huoming Zhang; Zhilin Sun; Jianmin Yang; Mingzheng Gao

2009-01-01

120

Differential effects of water depth and sediment type on clonal growth of the submersed macrophyte Vallisneria natans  

Microsoft Academic Search

The response of clonal growth and ramet morphology to water depth (from 60 to 260 cm) and sediment type (sand versus organic\\u000a clay) was investigated for the stoloniferous submersed macrophyte Vallisneria natans in an outdoor pond experiment. Results showed that water depth significantly affected clonal growth of V. natans in terms of clone weight, number of ramets, number of generations,

Keyan Xiao; Dan Yu; Zhonghua Wu

2007-01-01

121

Shallow sea-floor reflectance and water depth derived by unmixing multispectral imagery  

SciTech Connect

A major problem for mapping shallow water zones by the analysis of remotely sensed data is that contrast effects due to water depth obscure and distort the special nature of the substrate. This paper outlines a new method which unmixes the exponential influence of depth in each pixel by employing a mathematical constraint. This leaves a multispectral residual which represents relative substrate reflectance. Input to the process are the raw multispectral data and water attenuation coefficients derived by the co-analysis of known bathymetry and remotely sensed data. Outputs are substrate-reflectance images corresponding to the input bands and a greyscale depth image. The method has been applied in the analysis of Landsat TM data at Hamelin Pool in Shark Bay, Western Australia. Algorithm derived substrate reflectance images for Landsat TM bands 1, 2, and 3 combined in color represent the optimum enhancement for mapping or classifying substrate types. As a result, this color image successfully delineated features, which were obscured in the raw data, such as the distributions of sea-grasses, microbial mats, and sandy area. 19 refs.

Bierwirth, P.N.; Lee, T.J.; Burne, R.V. (Marine Spill Response Corp., Washington, DC (United States) Michigan Environmental Research Inst., Ann Arbor (United States))

1993-03-01

122

Comments on ‘The effective depth of cylindrical ionization chambers in water for clinical proton beams’  

NASA Astrophysics Data System (ADS)

In a recent paper (Bhullar and Watchman 2012 Phys. Med. Biol. 57 273-86), the authors comment on data concerning the effective depth of cylindrical ionization chambers in water for clinical proton beams calculated in a previous paper (Palmans 2006 Phys. Med. Biol. 51 3483-501) and propose different results. They present a closed-format expression for an integral in the analytical model and claim that the series expansion I used in the older paper does not converge to the correct solution. They also claim that this is the reason for the resulting values of the shift of the effective depth with respect to the chamber centre to be different in both papers. Both claims are, however, incorrect as I show in this comment. The values they present are most likely based on a mistake in the scaling coefficients to account for the non-water equivalence of wall, sleeve and central electrode materials. The better agreement which they observe between their values and the recommendation ofIAEA TRS-398 is thus a coincidence. My conclusion is that the best available data for the effective depth of cylindrical ionization chambers in water in clinicalproton beams are at present the values I published before (Palmans 2006Phys. Med. Biol. 51 3483-501) and which are supported by Monte Carlo simulations and experimental evidence.

Palmans, H.

2012-11-01

123

Estimated Depth to Ground Water and Configuration of the Water Table in the Portland, Oregon Area.  

National Technical Information Service (NTIS)

Reliable information on the configuration of the water table in the Portland metropolitan area is needed to address concerns about various water-resource issues, especially with regard to potential effects from stormwater injection systems such as UIC (un...

D. T. Snyder

2008-01-01

124

Modeling bulk density and snow water equivalent using daily snow depth observations.  

NASA Astrophysics Data System (ADS)

Bulk density is a fundamental property of snow relating its depth and mass. Previously, two simple models of bulk density (depending on snow depth, date, and location) have been developed to convert snow depth observations to snow water equivalent (SWE) estimates. However, these models were not intended for application at the daily time step. We develop a new model of bulk density for the daily timestep and demonstrate its improved skill over the existing models. Snow depth and density are negatively correlated at short (10 days) timescales while positively correlated at longer (90 days) timescales. We separate these scales of variability by modeling smoothed, daily snow depth (long time scales) and the observed positive and negative anomalies from the smoothed timeseries (short timescales) as separate terms. A climatology of fit is also included as a predictor variable. Over a half-million, daily observations of depth and SWE at 345 SNOTEL sites are used to fit models and evaluate their performance. For each location, we train the three models to the neighboring stations within 70 km, transfer the parameters to the location to be modeled, and evaluate modeled timeseries against the observations at that site. Our model exhibits improved statistics and qualitatively more-realistic behavior at the daily time step when sufficient local training data are available. We reduce density RMSE by 9.6% and 4.2% compared to previous models. Similarly, R2 increases from 0.46 to 0.52 to 0.56 across models. Removing the challenge of parameter transfer increases R2 scores for both the existing and new models, but the gain is greatest for the new model (R2 = 0.75). Our model shows general improvement over the existing models when data are more frequent than once every 5 days and at least 3 stations are available for training.

McCreight, J. L.; Small, E. E.

2013-10-01

125

Mapping Water-Table Depths Over Time to Assess Desiccation of Groundwater-Dependent Ecosystems in the Netherlands  

Microsoft Academic Search

During the past decades, groundwater-dependent ecosystems in the Netherlands have been threatened by a decline in the water-table\\u000a level. However, information on water-table depths and changes in water-table depths is insufficient and outdated. For policy\\u000a evaluation, spatially explicit and detailed information on water-table depths is required, especially in areas with groundwater-dependent\\u000a ecosystems including wetlands. Some 35,000 observations of seasonal fluctuation

Tom Hoogland; Gerard B. M. Heuvelink; Martin Knotters

2010-01-01

126

(Depth-dose curves of the beta reference fields (147)Pm, (85)Kr and (90)Sr/(90)Y produced by the beta secondary standard BSS2.  

PubMed

The most common reference fields in beta dosimetry are the ISO 6980 series 1 radiation fields produced by the beta secondary standard BSS2 and its predecessor BSS. These reference fields require sealed beta radiation sources ((147)Pm, (85)Kr or (90)Sr/(90)Y) in combination with a source-specific beam-flattening filter, and are defined only at a given distance from the source. Every radiation sources shipped with the BSS2 is sold with a calibration certificate of the Physikalisch-Technische Bundesanstalt. The calibration workflow also comprises regular depth-dose measurements. This work publishes complete depth-dose curves of the series 1 sources (147)Pm, (85)Kr and (90)Sr/(90)Y in ICRU tissue up to a depth of 11 mm,when all electrons are stopped. For this purpose, the individual depth-dose curves of all BSS2 sources calibrated so far have been determined, i.e. the complete datasets of all BSS2 beta sources have been re-evaluated. It includes 191 depth-dose curves of 116 different sources comprising more than 2200 data points in total. Appropriate analytical representations of the nuclide-specific depth-dose curves are provided for the first time. PMID:22267274

Brunzendorf, Jens

2012-01-20

127

A controlled water-table depth system to study the influence of fine-scale differences in water regime for plant growth  

Microsoft Academic Search

A method was developed to maintain water-table depths at a constant level in outdoor mesocosms. The system included a water treatment reservoir, where tap water was microbially deoxygenated and denitrified; an adjustable-level control chamber that set desired water-table depths and plant growing mesocosms.The soil water status was evaluated by constant monitoring using tensiometers, pressure transducers and dipwells. The robustness of

Yoseph N. Araya; David J. Gowing; Nancy Dise

2010-01-01

128

Ground-water contribution to dose from past Hanford Operations. Hanford Environmental Dose Reconstruction Project  

SciTech Connect

The Hanford Environmental Dose Reconstruction (HEDR) Project is being conducted to estimate radiation doses that populations and individuals could have received from Hanford Site operations from 1944 to the present. Four possible pathways by which radionuclides migrating in ground water on the Hanford Site could have reached the public have been identified: (1) through contaminated ground water migrating to the Columbia River; (2) through wells on or adjacent to the Hanford Site; (3) through wells next to the Columbia River downstream of Hanford that draw some or all of their water from the river (riparian wells); and (4) through atmospheric deposition resulting in contamination of a small watershed that, in turn, results in contamination of a shallow well or spring by transport in the ground water. These four pathways make up the ``ground-water pathway,`` which is the subject of this study. Assessment of the ground-water pathway was performed by (1) reviewing the existing extensive literature on ground water and ground-water monitoring at Hanford and (2) performing calculations to estimate radionuclide concentrations where no monitoring data were collected. Radiation doses that would result from exposure to these radionuclides were calculated.

Freshley, M.D.; Thorne, P.D.

1992-08-01

129

Effect of seedling age and water depth on morphological and physiological aspects of transplanted rice under high temperature.  

PubMed

To study the effect of high temperature, rice seedlings 20, 30, 40 and 50 d were kept at 5, 10, 15 and 20 cm water depth in a water pool. Meteorological findings indicated that water temperature varied up to 10 cm but became stable below this depth. Deep water inflicted higher tiller mortality, minimal increase in dry weight of aerial parts and leaf area, decrease in root length, and decrease in root dry weight especially at 20 cm water depth and produced an unbalanced T/R ratio (top versus root dry weight). However, deep water tended to increase plant length. These parameters, however, excel in shallow water. Older seedlings, with the exception of root dry weight, could not perform well compared to young seedlings in all physiological and morphological aspects. The study revealed that seedlings, particularly young ones, stand well in shallow water and can cope with high temperature. PMID:15822153

Khakwani, Abdul Aziz; Shiraishi, Masaaki; Zubair, Muhammad; Baloch, Mohammad Safdar; Naveed, Khalid; Awan, Inayatullah

2005-05-01

130

Seagrass Depth Limits in the Indian River Lagoon (Florida, U.S.A.): Application of an Optical Water Quality Model  

NASA Astrophysics Data System (ADS)

A model of spectral diffuse attenuation coefficient for downwelling irradiance in terms of the inherent optical properties of optically important water quality parameters was calibrated near two seagrass beds in the Indian River Lagoon, Florida, U.S.A. One of the seagrass sites was near the outflow of a canal discharging highly coloured water, and is regularly inundated by a plume of coloured water. Attenuation coefficients for photosynthetically active radiation predicted by the model agreed with observations within about 15 %. Observed ecological compensation depth for the seagrass bed more distant from the colour source agreed well with the central tendency of the 20 % penetration depth predicted by the optical model using the observed distributions of water quality parameters. Depth distributions of the seagrass bed near the coloured water source were about 0 ·5 m shallower, a result predicted by the optical model assuming the seagrass bed is inundated by the coloured water plume 50 -70 % of the time. At depths less than their ecological compensation depths, the two seagrass beds had similar species composition, shoot densities and biomass characteristics. Application of the model to hypothetical scenarios to reduce the impact of coloured water on the depth distribution of seagrasses near the discharge site indicated that any improvement in water quality would improve conditions for seagrass growth. The results indicate the utility of optical modelling in conjunction with limited field surveys of seagrasses for setting water quality objectives.

Gallegos, C. L.; Kenworthy, W. J.

1996-03-01

131

Ground-water contribution to dose from past Hanford Operations  

SciTech Connect

The Hanford Environmental Dose Reconstruction (HEDR) Project is being conducted to estimate radiation doses that populations and individuals could have received from Hanford Site operations from 1944 to the present. Four possible pathways by which radionuclides migrating in ground water on the Hanford Site could have reached the public have been identified: (1) through contaminated ground water migrating to the Columbia River; (2) through wells on or adjacent to the Hanford Site; (3) through wells next to the Columbia River downstream of Hanford that draw some or all of their water from the river (riparian wells); and (4) through atmospheric deposition resulting in contamination of a small watershed that, in turn, results in contamination of a shallow well or spring by transport in the ground water. These four pathways make up the ground-water pathway,'' which is the subject of this study. Assessment of the ground-water pathway was performed by (1) reviewing the existing extensive literature on ground water and ground-water monitoring at Hanford and (2) performing calculations to estimate radionuclide concentrations where no monitoring data were collected. Radiation doses that would result from exposure to these radionuclides were calculated.

Freshley, M.D.; Thorne, P.D.

1992-08-01

132

Low-cost water depth, temperature and electrical conductivity (CTD) sensor for spatially distributed groundwater table and surface water measurement  

NASA Astrophysics Data System (ADS)

Traditional instrumentation suites utilized for spatially distributed, catchment scale hydrological characterization effectively sample aboveground environmental variables and water storage in the vadose zone. However, spatially distributed measurements of shallow groundwater characteristics, critical to understand both vadose zone and groundwater hydrology, have often been under-sampled due mostly to prohibitive expense. An inexpensive CTD sensor designed specifically for catchment scale distributed sensing networks was developed to specifically fill this need. The depth measurement is optimized for shallow water measurements, with the high resolution and accuracy necessary for shallow ground and surface water measurements. Temperature and conductivity measurements are also optimized for these scenarios and the sensor consumes very little power and is therefore ideal for wireless data acquisition networks that are common in distributed sensing applications. This new measurement tool provides an opportunity to better understand shallow groundwater and surface water hydrologic processes.

Cobos, D.; Rivera, L.; Teare, B.; Campbell, G.; Campbell, C.

2012-04-01

133

Multidimensional modal analysis of nonlinear sloshing in a rectangular tank with finite water depth  

NASA Astrophysics Data System (ADS)

The discrete infinite-dimensional modal system describing nonlinear sloshing of an incompressible fluid with irrotational flow partially occupying a tank performing an arbitrary three-dimensional motion is derived in general form. The tank has vertical walls near the free surface and overturning waves are excluded. The derivation is based on the Bateman Luke variational principle. The free surface motion and velocity potential are expanded in generalized Fourier series. The derived infinite-dimensional modal system couples generalized time-dependent coordinates of free surface elevation and the velocity potential. The procedure is not restricted by any order of smallness. The general multidimensional structure of the equations is approximated to analyse sloshing in a rectangular tank with finite water depth. The amplitude frequency response is consistent with the fifth-order steady-state solutions by Waterhouse (1994). The theory is validated by new experimental results. It is shown that transients and associated nonlinear beating are important. An initial variation of excitation periods is more important than initial conditions. The theory is invalid when either the water depth is small or water impacts heavily on the tank ceiling. Alternative expressions for hydrodynamic loads are presented. The procedure facilitates simulations of a coupled vehicle fluid system.

Faltinsen, Odd M.; Rognebakke, Olav F.; Lukovsky, Ivan A.; Timokha, Alexander N.

2000-03-01

134

Effect of Depth of Flooding on the Rice Water Weevil, Lissorhoptrus oryzophilus, and Yield of Rice  

PubMed Central

The rice water weevil, Lissorhoptrus oryzophilus (Kuschel) (Coleoptera: Curculionidae), is a semi-aquatic pest of rice and is the most destructive insect pest of rice in the United States. Adults oviposit after floods are established, and greenhouse studies have shown that plants exposed to deep floods have more eggs oviposited in leaf sheaths than plants exposed to a shallow flood. Experiments were conducted in three mid-southern states in the USA to determine if the depth of flooding would impact numbers of L. oryzophilus on rice plants under field conditions. Rice was flooded at depths of approximately 5 or 10 cm in Arkansas in 2007 and 2008 and Louisiana in 2008, and at depths between 0–20 cm in Missouri in 2008. Plants were sampled three and four weeks after floods were established in all locations, and also two weeks after flood in Missouri. On all sampling dates in four experiments over two years and at three field sites, fewer L. oryzophilus larvae were collected from rice in shallow-flooded plots than from deep-flooded plots. The number of L. oryzophilus was reduced by as much as 27% in shallow-flooded plots. However, the reduction in insect numbers did not translate to a significant increase in rice yield. We discuss how shallow floods could be used as a component of an integrated pest management program for L. oryzophilus.

Tindall, Kelly V.; Bernhardt, John L.; Stout, Michael J.; Beighley, Donn H.

2013-01-01

135

Evaluation of SNODAS snow depth and snow water equivalent estimates for the Colorado Rocky Mountains, USA  

USGS Publications Warehouse

The National Weather Service's Snow Data Assimilation (SNODAS) program provides daily, gridded estimates of snow depth, snow water equivalent (SWE), and related snow parameters at a 1-km2 resolution for the conterminous USA. In this study, SNODAS snow depth and SWE estimates were compared with independent, ground-based snow survey data in the Colorado Rocky Mountains to assess SNODAS accuracy at the 1-km2 scale. Accuracy also was evaluated at the basin scale by comparing SNODAS model output to snowmelt runoff in 31 headwater basins with US Geological Survey stream gauges. Results from the snow surveys indicated that SNODAS performed well in forested areas, explaining 72% of the variance in snow depths and 77% of the variance in SWE. However, SNODAS showed poor agreement with measurements in alpine areas, explaining 16% of the variance in snow depth and 30% of the variance in SWE. At the basin scale, snowmelt runoff was moderately correlated (R2 = 0.52) with SNODAS model estimates. A simple method for adjusting SNODAS SWE estimates in alpine areas was developed that uses relations between prevailing wind direction, terrain, and vegetation to account for wind redistribution of snow in alpine terrain. The adjustments substantially improved agreement between measurements and SNODAS estimates, with the R2 of measured SWE values against SNODAS SWE estimates increasing from 0.42 to 0.63 and the root mean square error decreasing from 12 to 6 cm. Results from this study indicate that SNODAS can provide reliable data for input to moderate-scale to large-scale hydrologic models, which are essential for creating accurate runoff forecasts. Refinement of SNODAS SWE estimates for alpine areas to account for wind redistribution of snow could further improve model performance. Published 2011. This article is a US Government work and is in the public domain in the USA.

Clow, David W.; Nanus, Leora; Verdin, Kristine L.; Schmidt, Jeffrey

2012-01-01

136

Enhanced migratory waterfowl distribution modeling by inclusion of depth to water table data.  

PubMed

In addition to being used as a tool for ecological understanding, management and conservation of migratory waterfowl rely heavily on distribution models; yet these models have poor accuracy when compared to models of other bird groups. The goal of this study is to offer methods to enhance our ability to accurately model the spatial distributions of six migratory waterfowl species. This goal is accomplished by creating models based on species-specific annual cycles and introducing a depth to water table (DWT) data set. The DWT data set, a wetland proxy, is a simulated long-term measure of the point either at or below the surface where climate and geological/topographic water fluxes balance. For species occurrences, the USGS' banding bird data for six relatively common species was used. Distribution models are constructed using Random Forest and MaxEnt. Random Forest classification of habitat and non-habitat provided a measure of DWT variable importance, which indicated that DWT is as important, and often more important, to model accuracy as temperature, precipitation, elevation, and an alternative wetland measure. MaxEnt models that included DWT in addition to traditional predictor variables had a considerable increase in classification accuracy. Also, MaxEnt models created with DWT often had higher accuracy when compared with models created with an alternative measure of wetland habitat. By comparing maps of predicted probability of occurrence and response curves, it is possible to explore how different species respond to water table depth and how a species responds in different seasons. The results of this analysis also illustrate that, as expected, all waterfowl species are tightly affiliated with shallow water table habitat. However, this study illustrates that the intensity of affiliation is not constant between seasons for a species, nor is it consistent between species. PMID:22272288

Kreakie, Betty J; Fan, Ying; Keitt, Timothy H

2012-01-17

137

Water mass and depth determine the distribution and diversity of Rhodobacterales in an Arctic marine system.  

PubMed

Marine Rhodobacterales are recognized as a widespread, abundant, and metabolically versatile bacterial group in the world's oceans. They also show a nearly universal conservation of the genes for production of gene transfer agents (GTAs), virus-like particles that mediate genetic exchange between cells. It is not yet clear what factors determine the distribution of the various taxonomic subgroups of this order. To address this question, we analyzed the Rhodobacterales communities in 10 seawater samples from northern Baffin Bay collected during September 2008. A conserved gene from the GTA gene cluster was used to characterize the Rhodobacterales community structure. A total of 320 clones from 10 clone libraries were sequenced, and 22 operational taxonomic units representing putative species and 13 clusters representing putative genera were identified. A cluster related to Octadecabacter comprised 59% of total clones from the northern Baffin Bay. Phylogenetic analysis of the clones showed that the Rhodobacterales communities had distinct compositions in the different water masses that were sampled. A change in community structure related to depth was also observed. Therefore, in northern Baffin Bay where two ocean currents meet and mix, the Rhodobacterales community structures were primarily determined by water mass and depth. PMID:23374017

Fu, Yunyun; Keats, Kimberley F; Rivkin, Richard B; Lang, Andrew S

2013-02-27

138

Robust time reversal focusing based on Maximin criterion in a waveguide with uncertain water depth  

NASA Astrophysics Data System (ADS)

Time reversal processing (TRP) might be regarded as matched field processing with known environmental knowledge. However, the performance of TRP is degraded in an uncertain environment. A technique based on the Maximin criterion is proposed for enhancing the robustness of TRP in a waveguide with uncertain water depth. The relationship between the water depth and the focal spot translation is examined based on the waveguide-invariant theory. Then the time reversal transmission scheme with the Maximin criterion is performed to maximize the minimum transmission power on a target of interest. At the receiving end, coherent summation operation is carried out over the received data by a reception focusing bank. If it is necessary to enhance the target echo further, the iterative time reversal can be considered where the target echo corresponding to the first time reversal transmission is regarded as a secondary source. Numerical simulations and experimental results of the target localization in a waveguide tank have verified the effectiveness of robust TRP.

Pan, Xiang; Wang, Nan; Zhang, JiangFan; Xu, Wen; Gong, XianYi

2013-10-01

139

Water depth and surface current retrievals from airborne optical measurements of surface gravity wave dispersion  

NASA Astrophysics Data System (ADS)

Visible images of nearshore ocean waves obtained from an aircraft have been utilized to estimate the surface currents and water depth below the waves. A digital framing camera was mounted in a motion-stabilized turret and used to obtain temporal sequences of high-quality optical images of shoaling ocean waves. Data on the position and attitude of the camera/turret were used to map the image data to a rectilinear coordinate system at the level of the surface, effectively separating the spatial and temporal modulations due to the waves. The resulting three-dimensional (3-D) space-time data sets were Fourier transformed to obtain frequency-wave number spectra of these modulations. These spectra contain information on the propagation characteristics of the waves, such as their wavelengths and frequencies, and their directions and speeds of propagation. The water depth and current vector have been estimated by choosing these parameters so that a "best" fit is obtained between the theoretical dispersion relation for linear gravity waves and these 3-D wave spectra. Image data sets were acquired during the Shoaling Waves Experiment (SHOWEX) along the quasi-linear coastline in the vicinity of the Army Corps of Engineers' Field Research Facility (FRF) near Duck on the North Carolina Outer Banks. Summary wave parameters and bathymetry and current retrievals are typically within 10% of contemporaneous in situ measurements, though outliers occur.

Dugan, J. P.; Piotrowski, C. C.; Williams, J. Z.

2001-08-01

140

Influence of water vapour and permanent gases on the atmospheric optical depths and transmittance  

NASA Astrophysics Data System (ADS)

The influence of the atmospheric state on the extinction of direct solar radiation has been studied by using a four layer atmospheric model. Simple analytical formulae are established for the spectral optical depths of permanent gases and water vapour. These formulae use the ground level values of air pressure, temperature and relative huniidity. An additional parameter, related to the vertical distribution of the hunmidity content, is used for a better estimation of the water vapour optical depth. Good agreement between theory and measurements is found. The paper shows the dependence of the atmospheric spectral transmittance on the above mentioned parameters. L'influence de l'état atmosphérique sur l'extinction de la radiation solaire directe a été étudiée à l'aide d'un modèle atmosphérique développé antérieurement par l'auteur. Des formules simples ont été établies pour l'épaisseur optique spectrale des gaz et de la vapeur d'eau. Ces formules utilisent les valeurs de la pression atmosphérique, de la température et de l'humidité relative, mesurées au niveau du sol. Un paramètre supplémentaire, lié à la distribution verticale du contenu d'humidité, est utilisé pour calculer l'épaisseur optique due à la vapeur d'eau. La théorie est en bon accord avec les résultats des mesures. Le travail montre la dépendance de la transmittance atmosphérique spectrale en fonction des paramètres spécifiés ci-dessus.

Badescu, V.

1991-05-01

141

Out-of-field dose measurements in a water phantom using different radiotherapy modalities.  

PubMed

This investigation focused on the characterization of the lateral dose fall-off following the irradiation of the target with photons, protons and carbon ions. A water phantom was irradiated with a rectangular field using photons, passively delivered protons as well as scanned protons and carbon ions. The lateral dose profile in the depth of the maximum dose was measured using an ion chamber, a diamond detector and thermoluminescence detectors TLD-600 and TLD-700. The yield of thermal neutrons was estimated for all radiation types while their complete spectrum was measured with bubble detectors during the irradiation with photons. The peripheral dose delivered by photons is significantly higher compared to both protons and carbon ions and exceeds the latter by up to two orders of magnitude at distances greater than 50 mm from the field. The comparison of passive and active delivery techniques for protons shows that, for the chosen rectangular target shape, the former has a sharper penumbra whereas the latter has a lower dose in the far-out-of-field region. When comparing scanning treatments, carbon ions present a sharper dose fall-off than protons close to the target but increasing peripheral dose with increasing incident energy. For photon irradiation, the contribution to the out-of-field dose of photoneutrons appears to be of the same order of magnitude as the scattered primary beam. Charged particles show a clear supremacy over x-rays in achieving a higher dose conformality around the target and in sparing the healthy tissue from unnecessary radiation exposure. The out-of-field dose for x-rays increases with increasing beam energy because of the production of biologically harmful neutrons. PMID:22836598

Kaderka, R; Schardt, D; Durante, M; Berger, T; Ramm, U; Licher, J; La Tessa, C

2012-07-27

142

Out-of-field dose measurements in a water phantom using different radiotherapy modalities  

NASA Astrophysics Data System (ADS)

This investigation focused on the characterization of the lateral dose fall-off following the irradiation of the target with photons, protons and carbon ions. A water phantom was irradiated with a rectangular field using photons, passively delivered protons as well as scanned protons and carbon ions. The lateral dose profile in the depth of the maximum dose was measured using an ion chamber, a diamond detector and thermoluminescence detectors TLD-600 and TLD-700. The yield of thermal neutrons was estimated for all radiation types while their complete spectrum was measured with bubble detectors during the irradiation with photons. The peripheral dose delivered by photons is significantly higher compared to both protons and carbon ions and exceeds the latter by up to two orders of magnitude at distances greater than 50 mm from the field. The comparison of passive and active delivery techniques for protons shows that, for the chosen rectangular target shape, the former has a sharper penumbra whereas the latter has a lower dose in the far-out-of-field region. When comparing scanning treatments, carbon ions present a sharper dose fall-off than protons close to the target but increasing peripheral dose with increasing incident energy. For photon irradiation, the contribution to the out-of-field dose of photoneutrons appears to be of the same order of magnitude as the scattered primary beam. Charged particles show a clear supremacy over x-rays in achieving a higher dose conformality around the target and in sparing the healthy tissue from unnecessary radiation exposure. The out-of-field dose for x-rays increases with increasing beam energy because of the production of biologically harmful neutrons.

Kaderka, R.; Schardt, D.; Durante, M.; Berger, T.; Ramm, U.; Licher, J.; La Tessa, C.

2012-08-01

143

Dose distributions of model 6702 I-125 seeds in water.  

PubMed

Dose distributions in water of Model 6702 I-125 seeds have been measured to a distance of 9 cm from the seed center as a function of angle about the seed axis. A silicon diode and electrometer were used in the measurement. Two empirical models have been fitted to the data. The data have also been compared with Monte Carlo calculations. PMID:3570903

Schell, M C; Ling, C C; Gromadzki, Z C; Working, K R

1987-05-01

144

An Integrated System for the Study of Wind-Wave Source Terms in Finite-Depth Water  

Microsoft Academic Search

A field experiment to study the spectral balance of the source terms for wind-generated waves in finite water depth was carried out in Lake George, Australia. The measurements were made from a shore- connected platform at varying water depths from 1.2 m down to 20 cm. Wind conditions and the geometry of the lake were such that fetch-limited conditions with

Ian R. Young; Michael L. Banner; Mark A. Donelan; Alexander V. Babanin; W. Kendall Melville; Fabrice Veron; Cyril McCormick

2005-01-01

145

Dose to tissue medium or water cavities as surrogate for the dose to cell nuclei at brachytherapy photon energies  

Microsoft Academic Search

It has been suggested that modern dose calculation algorithms should be able to report absorbed dose both as dose to the local medium, Dm,m, and as dose to a water cavity embedded in the medium, Dw,m, using conversion factors from cavity theory. Assuming that the cell nucleus with its DNA content is the most important target for biological response, the

Shirin A Enger; Anders Ahnesjö; Frank Verhaegen; Luc Beaulieu

2012-01-01

146

Temperate carbonate cycling and water mass properties from intertidal to bathyal depths (Azores, N-Atlantic)  

NASA Astrophysics Data System (ADS)

The rugged submarine topography of the Azores supports a diverse heterozoan association resulting in intense biotically-controlled carbonate production and accumulation. In order to characterise this cold-water (C) factory a 2-year experiment was carried out to study the biodiversity of hardground communities and for budgeting carbonate production and degradation along a bathymetrical transect from the intertidal to bathyal 500 m depth. Seasonal temperatures peak in September (above a thermocline) and bottom in March (stratification diminishes) with a decrease in amplitude and absolute values with depth, and with tidal-driven short-term fluctuations. Measured seawater stable isotope ratios and levels of dissolved nutrients decrease with depth, as do the calcium carbonate saturation states. The photosynthetic active radiation shows a base of the euphotic zone in ~70 m and a dysphotic limit in ~150 m depth. Bioerosion, being primarily a function of light availability for phototrophic endoliths and grazers feeding upon them, is ~10 times stronger on the illuminated upside versus the shaded underside of substrates in the photic zone, with maximum rates in the intertidal (-631 g/m2/yr). Rates rapidly decline towards deeper waters where bioerosion and carbonate accretion are slow and epibenthic/endolithic communities take years to mature. Accretion rates are highest in the lower euphotic zone (955 g/m2/yr), where the substrate is less prone to hydrodynamic force. Highest rates are found - inversely to bioerosion - on downward facing substrates, suggesting that bioerosion may be a key factor governing the preferential settlement and growth of calcareous epilithobionts on downward facing substrates. In context of a latitudinal gradient, the Azores carbonate cycling rates plot between known values from the cold-temperate Swedish Kosterfjord and the tropical Bahamas, with a total range of two orders in magnitude. Carbonate budget calculations for the bathymetrical transect yield a mean 266.9 kg of epilithic carbonate production, -54.6 kg of bioerosion, and 212.3 kg of annual net carbonate production per metre of coastline in the Azores C factory.

Wisshak, M.; Form, A.; Jakobsen, J.; Freiwald, A.

2010-05-01

147

Temperate carbonate cycling and water mass properties from intertidal to bathyal depths (Azores)  

NASA Astrophysics Data System (ADS)

The rugged submarine topography of the Azores supports a diverse heterozoan association resulting in intense biotically-controlled carbonate-production and accumulation. In order to characterise this cold-water (C) factory a 2-year experiment was carried out in the southern Faial Channel to study the biodiversity of hardground communities and for budgeting carbonate production and degradation along a bathymetrical transect from the intertidal to bathyal 500 m depth. Seasonal temperatures peak in September (above a thermocline) and bottom in March (stratification diminishes) with a decrease in amplitude and absolute values with depth, and tidal-driven short-term fluctuations. Measured seawater stable isotope ratios and levels of dissolved nutrients decrease with depth, as do the calcium carbonate saturation states. The photosynthetic active radiation shows a base of the euphotic zone in ~70 m and a dysphotic limit in ~150 m depth. Bioerosion, being primarily a function of light availability for phototrophic endoliths and grazers feeding upon them, is ~10 times stronger on the illuminated upside versus the shaded underside of substrates in the photic zone, with maximum rates in the intertidal (-631 g/m2/yr). Rates rapidly decline towards deeper waters where bioerosion and carbonate accretion are slow and epibenthic/endolithic communities take years to mature. Accretion rates are highest in the lower euphotic zone (955 g/m2/yr), where the substrate is less prone to hydrodynamic force. Highest rates are found - inversely to bioerosion - on down-facing substrates, suggesting that bioerosion may be a key factor governing the preferential settlement and growth of calcareous epilithobionts on down-facing substrates. In context of a latitudinal gradient, the Azores carbonate cycling rates plot between known values from the cold-temperate Swedish Kosterfjord and the tropical Bahamas, with a total range of two orders in magnitude. Carbonate budget calculations for the bathymetrical transect yield a mean 266.9 kg of epilithic carbonate production, -54.6 kg of bioerosion, and 212.3 kg of annual net carbonate production per metre of coastline in the Azores C factory.

Wisshak, M.; Form, A.; Jakobsen, J.; Freiwald, A.

2010-08-01

148

Investigation on optimization design of an equivalent water depth truncated mooring system based on INSGA-II  

NASA Astrophysics Data System (ADS)

At present, equivalent water depth truncated mooring system optimization design is regarded as the priority of hybrid model testing for deep sea platforms, and will replace the full depth system test in the future. Compared with the full depth system, the working depth and span are smaller in the truncated one, and the other characteristics maintain more consistency as well. In this paper, an inner turret moored floating production storage & offloading system (FPSO) which works at a water depth of 320m, was selected to be a research example while the truncated water depth was 80m. Furthermore, an improved non-dominated sorting genetic algorithm (INSGA-II) was selected to optimally calculate the equivalent water depth truncated system, considering the stress condition of the total mooring system in both the horizontal and vertical directions, as well as the static characteristic similarity of the representative single mooring line. The results of numerical calculations indicate that the mathematical model is feasible, and the optimization method is fast and effective.

Zhang, Huoming; Gao, Wenjun; Wang, Qiang; Jiang, Juan; Zhao, Zhou

2012-06-01

149

Soil water and vegetation responses to precipitation and changes in depth to ground water in Owens Valley, California  

USGS Publications Warehouse

Vegetation on the floor of Owens Valley, California, is composed predominantly of phreatophytic desert communities that are adapted to small quantities of precipitation and alkaline soils. These plant communities are believed to be dependent on the continuing presence of a shallow water table. Maintaining existing plant communities is important to preserve the environmental quality of the valley. Proposals to pump additional quantities of ground water from the valley for export to the city of Los Angeles caused concern about the effect of pumping on the existing vegetation and how the plants would adapt to short- or long-term declines of the shallow water table. To test the ability of selected major shrub species to adapt to water-table decline, four sites were selected, pump-equipped wells were installed, and water-table drawdown was monitored. Soil samples were collected with a hand auger and analyzed by using the filter-paper method to monitor changes in soil water content and soil matric potential at test sites. Plant reactions were determined by measurements of plant cover, shoot growth, and xylem pressure potential. Results of 3 years of monitoring show that growth and cover repetition of the shrubs studied are affected greatly by the quantity of annual precipitation, especially at sites with coarse-textured soils. Plants were not affected by drying soil in the root zone until the maximum matric potential exceeded 4.3 pF (-1,950 kilopascal) at depths greater than 0.5 meter. Rabbit-brush was most sensitive to dry soil and was the only shrub species that died as the result of water stress from water-table drawdown. The change in cover repetition correlated positively with the magnitude of water-table drawdown at one site and negatively at another site. Measurements of xylem pressure potential taken before dawn correlated well with water content in the upper 1.5 meters of soil. The magnitude of water-table drawdown achieved by the pump-equipped wells was less than expected at three of the four sites. Additional water-table drawdown for a longer period of time would be needed to separate the effects of water-table drawdown from the effects caused by differences in soil textures and natural fluctuations in the quantity of precipitation.

Sorenson, Stephen K.; Dileanis, Peter D.; Branson, Farrel A.

1991-01-01

150

The wave excitation forces on a truncated vertical cylinder in water of infinite depth  

NASA Astrophysics Data System (ADS)

When carrying out any numerical modelling it is useful to have an analytical approximation available to provide a check on the accuracy of the numerical results and to give insight into the underlying physics of the system. The numerical modelling of wave energy converters is an efficient and inexpensive method of undertaking initial optimisation and experimentation. Therefore, the main objective of this paper is to determine an analytical approximation for the wave excitation forces on a floating truncated vertical cylinder in water of infinite depth. The approximation is developed by solving appropriate boundary value problems using the method of separation of variables. A graphical representation of the analytical approximation for the truncated vertical cylinder and the cylinder of infinite depth are presented and are compared to the results from a computational fluid dynamics analysis, using a commercial boundary element package. The presented analytical approximation and the computational fluid dynamics analysis results were found to be in good agreement. Furthermore, the presented analytical approximation was found to be in good agreement with independent experimental data.

Finnegan, William; Meere, Martin; Goggins, Jamie

2013-07-01

151

Measurement of the depth-dependent resonance of water-loaded human lungs  

NASA Astrophysics Data System (ADS)

An experiment was conducted to determine the response of the human lung to water-borne sound in the range of 20 to 500 Hz. A small pool inside a hyperbaric chamber was used to simulate four ambient pressure conditions spanning the range of recreational diving depths. Ten subjects were tested on two occasions each using three separate measures to evaluate the response of the subjects' lungs. With some notable exceptions, results were consistent between subjects and between measures. These indicate that human lungs can be reasonably modeled as a lumped single-degree-of-freedom system over the lower portion of the band of interest. Here, the surrounding fluid provides the dominant mass and the dominant stiffness is provided by the entrapped air with a small additional contribution from tissue elasticity. Measured resonances increase with the square root of ambient pressure from an average of 40 Hz with a quality factor of 1.8 at near-surface pressure to 73 Hz with a quality factor of 2.6 at an equivalent depth of 36.4 m. There is evidence of other resonances within or near the band of interest that may be attributable to nonvolumetric chest/lung modes, Helmholtz resonance, and/or resonance of gastrointestinal bubbles. .

Martin, J. S.; Rogers, P. H.; Cudahy, E. A.

2005-04-01

152

Depth of cinder deposits and water-storage capacity at Cinder Lake, Coconino County, Arizona  

USGS Publications Warehouse

The 2010 Schultz fire northeast of Flagstaff, Arizona, burned more than 15,000 acres on the east side of San Francisco Mountain from June 20 to July 3. As a result, several drainages in the burn area are now more susceptible to increased frequency and volume of runoff, and downstream areas are more susceptible to flooding. Resultant flooding in areas downgradient of the burn has resulted in extensive damage to private lands and residences, municipal water lines, and roads. Coconino County, which encompasses Flagstaff, has responded by deepening and expanding a system of roadside ditches to move flood water away from communities and into an area of open U.S. Forest Service lands, known as Cinder Lake, where rapid infiltration can occur. Water that has been recently channeled into the Cinder Lake area has infiltrated into the volcanic cinders and could eventually migrate to the deep regional groundwater-flow system that underlies the area. How much water can potentially be diverted into Cinder Lake is unknown, and Coconino County is interested in determining how much storage is available. The U.S. Geological Survey conducted geophysical surveys and drilled four boreholes to determine the depth of the cinder beds and their potential for water storage capacity. Results from the geophysical surveys and boreholes indicate that interbedded cinders and alluvial deposits are underlain by basalt at about 30 feet below land surface. An average total porosity for the upper 30 feet of deposits was calculated at 43 percent for an area of 300 acres surrounding the boreholes, which yields a total potential subsurface storage for Cinder Lake of about 4,000 acre-feet. Ongoing monitoring of storage change in the Cinder Lake area was initiated using a network of gravity stations.

Macy, Jamie P.; Amoroso, Lee; Kennedy, Jeff; Unema, Joel

2012-01-01

153

Sedimentological data indicate greater range of water depths for Costistricklandia lirata in the Southern Appalachians  

SciTech Connect

Two distinct horizons of the pentamerid brachiopod Costistricklandia lirata occur in the upper part of the Red Mountain Formation (Lower Silurian) in northern Alabama. Stratigraphic and sedimentologic characteristics of the rocks associated with the brachiopods suggest water depths of 15-150 m during times of low rates of terrigenous influx. Costistricklandid assemblages from the lower horizon are composed of extremely large individuals in association with a diverse population of large corals. They are interpreted to have lived in a protected environment. In an overlying horizon, costistricklandids occur in growth position at the base of a thick siliciclastic interval. These brachiopods lived in a storm-dominated environment and were buried in situ by the rapid influx of sediment associated with a passing storm.

Bolton, J.C. (Univ. of Tennessee, Knoxville (USA))

1990-08-01

154

Comparison of MCNP4C and EGSnrc Monte Carlo codes in depth-dose calculation of low energy clinical electron beams  

Microsoft Academic Search

Comparison of different Monte Carlo codes for understanding their limitations is essential to avoid systematic errors in the simulation, and to suggest further improvement for the codes. MCNP4C and EGSnrc, two Monte Carlo codes commonly used in medical physics, were compared and evaluated against electron depth-dose data and experimental results obtained using clinical radiotherapy beams. Different physical models and algorithms

N. Jabbari; B. Hashemi-Malayeri; A. R. Farajollahi; A. Kazemnejad; A. Shafaei; S. Jabbari

2007-01-01

155

Operational Aspects of Mooring a Drilling Vessel in Water Depths of 4,200 to 4,700 ft  

Microsoft Academic Search

This paper reports on mooring operations in deep water which require detailed planning and special techniques for oil well drilling rigs and anchor-handling vessels (AHV's). Techniques developed by a multidisciplinary task group were used successfully and safely during two mooring operations in water depths ranging from 4,200 to 4,700 ft.

J. W. Barker; R. M. Day

1991-01-01

156

[Effects of submarine topography and water depth on distribution of pelagic fish community in minnan-taiwan bank fishing ground].  

PubMed

According to the fishing record of the light-seine information vessel in Minnan-Taiwan bank ground during 1989 to 1999, the effects of submarine topography and water depth on distribution of pelagic fish community in Minnan-Taiwan bank fishing ground was studied. The results showed that the pelagic fish distributed concentratively, while the submarine topography and water depth varied widely, but in different fishing regions, the distribution of pelagic fishes was uneven. The distribution of fishing yield increased from north to south, and closed up from sides of the bank to south or north in the regions. Pelagic fish distributed mainly in mixed water in the southern Taiwan Strait, and in warm water in the Taiwan Strait. The central fishing grounds were at high salt regions. Close gathering regions of pelagic fish or central fishing ground would be varied with the seasonal variation of mixed water in the southern Taiwan Strait and warm water in the Taiwan Strait. Central fishing ground was not only related to submarine topography and water depth, but also related to wind direction, wind-power and various water systems. In the fishing ground, the gathering depth of pelagic fish was 30-60 m in spring and summer, and 40-80 m in autumn and winter. PMID:12625009

Fang, Shuimei; Yang, Shengyun; Zhang, Chengmao; Zhu, Jinfu

2002-11-01

157

Bioluminescence in a complex coastal environment: 2. Prediction of bioluminescent source depth from spectral water-leaving radiance  

Microsoft Academic Search

Many bioluminescence observations are made from the ocean's surface. However, the depth of the bioluminescent source is difficult to estimate on the basis of surface observations alone, given the variable light attenuation of unknown concentrations of water column constituents such as phytoplankton, colored dissolved organic matter, and detritus. Part 1 of this paper showed that bioluminescent water-leaving radiance signals are

Matthew J. Oliver; Mark A. Moline; Curtis D. Mobley; Lydia Sundman; Oscar M. E. Schofield

2007-01-01

158

Operational aspects of mooring a drilling vessel in water depths of 4,200 to 4,700 ft  

SciTech Connect

This paper reports on mooring operations in deep water which require detailed planning and special techniques for oil well drilling rigs and anchor-handling vessels (AHV's). Techniques developed by a multidisciplinary task group were used successfully and safely during two mooring operations in water depths ranging from 4,200 to 4,700 ft.

Barker, J.W.; Day, R.M. (Exxon Co. U.S.A. (US))

1991-09-01

159

Effect of crop sequence, soil sample location and depth on soil water holding capacity under center pivot irrigation  

Microsoft Academic Search

This study was carried out to investigate the changes that may occur to the soil water holding capacity under center pivot irrigation systems when grown with different crop patterns over a long period of time. The changes of water holding capacity were checked as affected by crop location and depth. The study was carried out in a dominantly sandy loam

Yousef A. Al-Rumikhani

2002-01-01

160

Penetration of Antarctic subglacial lakes by VHF electromagnetic pulses: Information on the depth and electrical conductivity of basal water bodies  

Microsoft Academic Search

Owing to the high level of absorption of very high frequency radio waves in water, previous investigators of airborne radio echo sounding (RES) data from Antarctica have assumed that the depth of subglacial lakes cannot be measured directly by this method. However, we have identified a number of RES returns from beneath the ice-water interface at the surface of eight

Michael R. Gorman; Martin J. Siegert

1999-01-01

161

Semi-empirical lake level (SELL) model for mapping lake water depths from partially clouded satellite data  

NASA Astrophysics Data System (ADS)

Information on the variability in surface water is critical to understand the impact of climate change and global water cycle. Surface water features such as lakes, or reservoirs can affect local weather and regional climate. Hence, there is a widespread demand for accurate and quantitative global observations of surface water variability. Satellite imagery provides a direct way to monitor variations in surface water. However, estimating accurate surface area from satellite imagery can be a problem due to clouds. Hence, the use of optical imagery for operational implementation has been a challenge for monitoring variations in surface water. In this research, a semi-empirical lake level (SELL) model is developed to derive lake/reservoir water levels from partially covered satellite imagery. SRTM elevation combined with bathymetry was used to derive the relationships between lake depth vs. surface area and shore line (L). Using these relationships, lake level/depth (D) was estimated from the surface area (A) and/or shore line (L) delineated from Landsat and MODIS data. The SELL model was applied on Lake Turkana, one of the rift valley lakes in East Africa. First, Lake Turkana water levels were delineated using cloud-free or partially clouded Landsat and MODIS imagery over 1993-2009 and 2002-2009 time periods respectively. Historic lake depths were derived using 1972-1992 Landsat imagery. Lake depths delineated using this approach were validated using TOPEX/Poseidon/Jason satellite altimetry data. It was found that lake depths derived using SELL model matched reasonably well with the satellite altimetry data. The approach presented in this research can be used to (a) simulate lake water level variations in data scarce regions (b) increase the frequency of observation in regions where cloud cover is a problem (c) operationally monitor lake water levels in ungauged basins (d) derive historic lake level information using satellite data.

Velpuri, N.; Senay, G. B.

2011-12-01

162

The mean depth of soil water uptake by two temperate grassland species over time subjected to mild soil water deficit and competitive association  

Microsoft Academic Search

Little is known concerning the soil water use dynamics of white clover (WC) and ryegrass (RG) grown in mixtures. A greenhouse study, on a deep soil, was conducted to determine the mean depth of soil water uptake of WC and RG plants grown in a competitive association and subjected to a moderate soil water deficit. Plant growth period simulated that

P. Grieu; D. W. Lucero; R. Ardiani; J. R. Ehleringer

2001-01-01

163

Effects of water table depth and calcium perioxide application on cowpea ( Vigna unguiculata ) and soybean ( Glycine max )  

Microsoft Academic Search

Summary  The effects of three water table (WT) depths (0, 15 and 40 cm) and calcium peroxide (Calper) on the growth and yield of cowpea\\u000a (Vigna unguiculata, L.) and soybean (Glycine max) were investigated in field lysimeters for a sandy loam soil. Cowpea growth was the best at 40 cm WT depth. Leaf area, plant\\u000a height, dry matter production, number of

L. T. Ogunremi; R. Lal; O. Babalola

1981-01-01

164

Natural succession of macroalgal-dominated epibenthic assemblages at different water depths and after transplantation from deep to shallow water on Spitsbergen  

Microsoft Academic Search

In the current study, we investigated the primary succession of seaweeds over different time periods at different water depths.\\u000a Furthermore, we followed the succession of field-grown benthic communities of different successional age, developing on ceramic\\u000a tiles, prior to and after transplantation from 8 to 0.5 m water depth. The transplantation simulated changes associated with\\u000a the break up of sea-ice cover, e.g.

Anna Fricke; Markus Molis; Christian Wiencke; Nelson Valdivia; Annelise S. Chapman

2008-01-01

165

Dose assessment for process water tunnels at Hanford Site.  

SciTech Connect

The RESRAD-BUILD and RESRAD computer codes were used for dose assessment of the 105-C Process Water Tunnels at the Hanford Site. The evaluation assessed three different exposure scenarios: recreational use, tunnel maintenance worker, and residential use. The recreationist and maintenance worker scenarios were evaluated by using RESRAD-BUILD, a computer model for analyzing the radiological doses resulting from remediation and occupancy of structures contaminated with radioactive material. The recreationist was assumed to use the tunnels as an overnight shelter for eight hours per day for one week. The maintenance worker was assumed to spend 20 hours per year working in the tunnel. Six exposure pathways were considered for both scenarios in dose assessment. The gradual removal of surface contamination over time and ingrowth of decay products were considered in calculating the dose at different times. The maximum dose would occur immediately after the release and was estimated to be 1.9 mrem/yr for the recreationist and 0.9 mrem/yr for the maintenance worker. The residential scenario was evaluated by using the probabilistic RESRAD code. It was assumed that total activity from the tunnels would be brought into the near-surface layer by future human activities. Eight exposure pathways were considered. The maximum yearly dose for this very unlikely scenario would occur immediately after the release and was less than 4 mrem/yr for the maximally exposed individual. The assessment demonstrates that both codes are suitable for nuclear facility decontamination and decommissioning sites, where buildings and structures with residual radioactivity must be evaluated to facilitate property transfer or release.

Kamboj, S.; Yu, C.; LePoire, D.; Environmental Assessment

2000-01-01

166

Small scale spatial variability of snow density and depth over complex alpine terrain: Implications for estimating snow water equivalent  

NASA Astrophysics Data System (ADS)

This study analyzes spatial variability of snow depth and density from measurements made in February and April of 2010 and 2011 in three 1-2 km2 areas within a valley of the central Spanish Pyrenees. Snow density was correlated with snow depth and different terrain characteristics. Regression models were used to predict the spatial variability of snow density, and to assess how the error in computed densities might influence estimates of snow water equivalent (SWE).The variability in snow depth was much greater than that of snow density. The average snow density was much greater in April than in February. The correlations between snow depth and density were generally statistically significant but typically not very high, and their magnitudes and signs were highly variable among sites and surveys. The correlation with other topographic variables showed the same variability in magnitude and sign, and consequently the resulting regression models were very inconsistent, and in general explained little of the variance. Antecedent climatic and snow conditions prior to each survey help highlight the main causes of the contrasting relation shown between snow depth, density and terrain. As a consequence of the moderate spatial variability of snow density relative to snow depth, the absolute error in the SWE estimated from computed densities using the regression models was generally less than 15%. The error was similar to that obtained by relating snow density measurements directly to adjacent snow depths.

López-Moreno, J. I.; Fassnacht, S. R.; Heath, J. T.; Musselman, K. N.; Revuelto, J.; Latron, J.; Morán-Tejeda, E.; Jonas, T.

2013-05-01

167

Rooting depth and water source flexibility of Arundo donax across a wide and topographically varied floodplain inferred from stable isotopes  

NASA Astrophysics Data System (ADS)

Floodplain environments can exhibit strong gradients in soil moisture availability, from very dry to saturated, with important consequences for riparian vegetation transpiration and productivity and therefore ecohydrologic flowpaths. These gradients are often driven by geomorphic features that themselves can be affected by vegetation change over relatively short timescales. The Rio Grande has undergone substantial change in the past half century, including channel narrowing and significant expansion of non-native vegetation, often across previously unvegetated sandbars and natural levees. The objective of this study was to assess water sources for Arundo donax L. (giant reed), a now common invasive grass growing along the floodplains of the Rio Grande. Our hypotheses were: a) Arundo would switch from primarily shallow soil moisture to groundwater during periods of soil moisture deficit, but that this access would be limited by increasing groundwater depths, and b) transpiration would decline with floodplain elevation and decreasing surface soil moisture because of increasing depth to groundwater and surface soil moisture deficits. We used natural-abundance stable isotopes of oxygen (?18O) and hydrogen (?2H) to determine the water sources of Arundo along four approximately 100-meter transects arrayed perpendicular to the Rio Grande in southwest Texas. Surface soil water, river water, groundwater, precipitation and rhizome sections were collected every month from summer 2010 until summer 2011 to assess potential source water isotopic composition for Arundo. Mixing models were used to estimate Arundo dependence on surface soil moisture or groundwater. The isotopic compositions of groundwater and river water were similar throughout the year, indicating significant hyporheic exchange. As expected, the isotopic composition of precipitation events and a large flood event were distinct from the slowly-changing river and allowed an assessment of Arundo use of these sources relative to groundwater. Rhizome water isotopic composition exhibited marked spatio-temporal variability that showed strong sensitivity to both soil moisture deficits and flooding. Our results demonstrate that Arundo readily switches water source from surface soil to groundwater to maintain relatively uniform transpiration across environmental gradients. Consistent with our observations of rooting depths to at least 5 m, dependence on groundwater increased with decreasing soil moisture in a similar manner across a wide range of groundwater depths (<1 m to 5 m), with no apparent influence of depth on deep water access. These trends illustrate how this now broadly-distributed species benefits from flexible use of hydrologic flowpaths unique to riparian environments. A more in-depth understanding of the ecohydrological interactions between the river, the hyporheic zone, riparian sediments and soils will improve our ability to predict ecosystem responses to changing climate and increasing human demands for water.

Moore, G. W.; West, J. B.; Li, F.; Kui, L.

2011-12-01

168

Improving parameter estimation and water table depth simulation in a land surface model using GRACE water storage and estimated base flow data  

Microsoft Academic Search

Several previous studies have shown the significance of representing shallow groundwater in land surface model (LSM) simulations. However, optimal methods for parameter estimation in order to realistically simulate water table depth have received little attention. The recent availability of Gravity Recovery and Climate Experiment (GRACE) water storage data provides a unique opportunity to constrain LSM simulations of terrestrial hydrology. In

Min-Hui Lo; James S. Famiglietti; P. J.-F. Yeh; T. H. Syed

2010-01-01

169

Conversion from dose-to-graphite to dose-to-water in an 80 MeV/A carbon ion beam  

NASA Astrophysics Data System (ADS)

Based on experiments and numerical simulations, a study is carried out pertaining to the conversion of dose-to-graphite to dose-to-water in a carbon ion beam. This conversion is needed to establish graphite calorimeters as primary standards of absorbed dose in these beams. It is governed by the water-to-graphite mass collision stopping power ratio and fluence correction factors, which depend on the particle fluence distributions in each of the two media. The paper focuses on the experimental and numerical determination of this fluence correction factor for an 80 MeV/A carbon ion beam. Measurements have been performed in the nuclear physics laboratory INFN-LNS in Catania (Sicily, Italy). The numerical simulations have been made with a Geant4 Monte Carlo code through the GATE simulation platform. The experimental data are in good agreement with the simulated results for the fluence correction factors and are found to be close to unity. The experimental values increase with depth reaching 1.010 before the Bragg peak region. They have been determined with an uncertainty of 0.25%. Different numerical results are obtained depending on the level of approximation made in calculating the fluence correction factors. When considering carbon ions only, the difference between measured and calculated values is maximal just before the Bragg peak, but its value is less than 1.005. The numerical value is close to unity at the surface and increases to 1.005 near the Bragg peak. When the fluence of all charged particles is considered, the fluence correction factors are lower than unity at the surface and increase with depth up to 1.025 before the Bragg peak. Besides carbon ions, secondary particles created due to nuclear interactions have to be included in the analysis: boron ions (10B and 11B), beryllium ions (7Be), alpha particles and protons. At the conclusion of this work, we have the conversion of dose-to-graphite to dose-to-water to apply to the response of a graphite calorimeter in an 80 MeV/A carbon ion beam. This conversion consists of the product of two contributions: the water-to-graphite electronic mass collision stopping power ratio, which is equal to 1.115, and the fluence correction factor which varies linearly with depth, as kfl, all = 0.9995 + 0.0048?zw-eq. The latter has been determined on the basis of experiments and numerical simulations.

Rossomme, S.; Palmans, H.; Shipley, D.; Thomas, R.; Lee, N.; Romano, F.; Cirrone, P.; Cuttone, G.; Bertrand, D.; Vynckier, S.

2013-08-01

170

Conversion from dose-to-graphite to dose-to-water in an 80 MeV/A carbon ion beam.  

PubMed

Based on experiments and numerical simulations, a study is carried out pertaining to the conversion of dose-to-graphite to dose-to-water in a carbon ion beam. This conversion is needed to establish graphite calorimeters as primary standards of absorbed dose in these beams. It is governed by the water-to-graphite mass collision stopping power ratio and fluence correction factors, which depend on the particle fluence distributions in each of the two media. The paper focuses on the experimental and numerical determination of this fluence correction factor for an 80 MeV/A carbon ion beam. Measurements have been performed in the nuclear physics laboratory INFN-LNS in Catania (Sicily, Italy). The numerical simulations have been made with a Geant4 Monte Carlo code through the GATE simulation platform. The experimental data are in good agreement with the simulated results for the fluence correction factors and are found to be close to unity. The experimental values increase with depth reaching 1.010 before the Bragg peak region. They have been determined with an uncertainty of 0.25%. Different numerical results are obtained depending on the level of approximation made in calculating the fluence correction factors. When considering carbon ions only, the difference between measured and calculated values is maximal just before the Bragg peak, but its value is less than 1.005. The numerical value is close to unity at the surface and increases to 1.005 near the Bragg peak. When the fluence of all charged particles is considered, the fluence correction factors are lower than unity at the surface and increase with depth up to 1.025 before the Bragg peak. Besides carbon ions, secondary particles created due to nuclear interactions have to be included in the analysis: boron ions ((10)B and (11)B), beryllium ions ((7)Be), alpha particles and protons. At the conclusion of this work, we have the conversion of dose-to-graphite to dose-to-water to apply to the response of a graphite calorimeter in an 80 MeV/A carbon ion beam. This conversion consists of the product of two contributions: the water-to-graphite electronic mass collision stopping power ratio, which is equal to 1.115, and the fluence correction factor which varies linearly with depth, as k(fl, all) = 0.9995 + 0.0048(zw-eq). The latter has been determined on the basis of experiments and numerical simulations. PMID:23877166

Rossomme, S; Palmans, H; Shipley, D; Thomas, R; Lee, N; Romano, F; Cirrone, P; Cuttone, G; Bertrand, D; Vynckier, S

2013-07-23

171

The development of a concept for accurate and efficient dredging at great water depths  

Microsoft Academic Search

Especially in the past decade dredging projects are being carried out at an ever increasing depth and scale. Modern Trailing Suction Hopper Dredgers (TSHD's) can now dredge up to 150 m depth. However, for certain projects, it is necessary to exceed this limit. One can think of the exploitation of certain minerals, which may be economic in the near future,

O. Verheul; P. M. Vercruijsse; S. A. Miedema

172

Comparison of MCNP4C and EGSnrc Monte Carlo codes in depth-dose calculation of low energy clinical electron beams  

NASA Astrophysics Data System (ADS)

Comparison of different Monte Carlo codes for understanding their limitations is essential to avoid systematic errors in the simulation, and to suggest further improvement for the codes. MCNP4C and EGSnrc, two Monte Carlo codes commonly used in medical physics, were compared and evaluated against electron depth-dose data and experimental results obtained using clinical radiotherapy beams. Different physical models and algorithms used in the codes give significantly different depth-dose curves. The default version of MCNP4C calculates electron depth-dose curves which are too much penetrating. The MCNP4C results agree better with the experiment if the Integrated Tiger Series-style energy-indexing algorithm is used. EGSnrc uses a class II-Condensed History (CH) scheme for the simulation of electron transport. To conclude the comparison, a timing study was performed. It was noted that EGSnrc is generally faster than MCNP4C and the use of a large number of scoring voxels dramatically slows down the MCNP4C calculation. However, the use of a large number of geometry voxels in MCNP4C only slightly affects the speed of the calculation.

Jabbari, N.; Hashemi-Malayeri, B.; Farajollahi, A. R.; Kazemnejad, A.; Shafaei, A.; Jabbari, S.

2007-08-01

173

Penetration depth measurement of a 6 MeV electron beam in water by magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

We demonstrate magnetic resonance imaging (MRI) visualization of a 6 MeV electron beam in ferrous-doped water; a 25 mm penetration depth was measured. Time domain nuclear magnetic resonance was used to investigate the effect of generated free radicals on the free induction decay (FID) in nondoped water; no apparent effects to the FID were observed. We show that MRI visualization of charged particle beams used in medical applications will require exogenous agents to provide contrast enhancement.

Hammer, B. E.; Christensen, N. L.; Conroy, M. J.; King, W. J.; Pogue, N.

2011-11-01

174

Surface analysis and depth profiling of corrosion products formed in lead pipes used to supply low alkalinity drinking water  

Microsoft Academic Search

Modern analytical techniques have been applied to investigate the nature of lead pipe corrosion products formed in pH adjusted, orthophosphate-treated, low alkalinity water, under supply conditions. Depth profiling and surface analysis have been carried out on pipe samples obtained from the water distribution system in Glasgow, Scotland, UK. X-ray diffraction spectrometry identified basic lead carbonate, lead oxide and lead phosphate

C. M. Davidson; N. J. Peters; A. Britton; L. Brady; P. H. E. Gardiner; B. D. Lewis

175

Map showing depth to pre-Cenozoic basement in the Death Valley ground-water model area, Nevada and California  

Microsoft Academic Search

This map shows the depth to pre-Cenozoic basement in the Death Valley ground-water model area. It was prepared utilizing gravity (Ponce and others, 2001), geologic (Jennings and others, 1977; Stewart and Carlson, 1978), and drill-hole information. Geophysical investigations of the Death Valley ground-water model area are part of an interagency effort by the U.S. Geological Survey (USGS) and the U.S.

R. J. Blakely; D. A. Ponce

2002-01-01

176

Correlation of changes in pigment content with photosynthetic capacity of seaweeds as a function of water depth  

Microsoft Academic Search

We conducted a study of the relationship between changes in photosynthetic pigment content and photosynthetic capacity as a function of water depth in Great Harbor near Woods Hole, Massachusetts, USA, on the green algae Ulva lactuca and Codium fragile and the red algae Porphyra umbilicalis and Chondrus crispus. Seaweeds were attached to vertically buoyed lines at 0.5 and 10 m

J. Ramus; S. I. Beale; D. Mauzerall

1976-01-01

177

Interactive effects of seed availability, water depth, and phosphorus enrichment on cattail colonization in an Everglades wetland  

Microsoft Academic Search

The relative importance of seed availability, waterdepth, and soil phosphorus (P) concentrations oncattail (Typha domingensis pers.) earlyestablishment in an Everglades wetland area wasexamined using seed bank analysis and controlledexperiments. The experiments measured seed germinationand seedling growth in tanks with cattail seedaddition subjected to two P concentrations(un-enriched vs. enriched) and water depth (saturatedvs. flooded soils). A limited seed bank (223 ±

S. L. Miao; P. V. McCormick; S. Newman; S. Rajagopalan

2001-01-01

178

Monitoring of Abundance and Depth Distribution of Water Along the Path of MSL Rover with DAN Instrument  

NASA Astrophysics Data System (ADS)

We present a summary of the Dynamic Albedo of Neutrons (DAN) instrument onboard NASA's 2009 Mars Science Laboratory mission. This instrument will study the abundance and depth distribution of water in the martian subsurface along the path of the MSL rover.

Litvak, M. L.; Kozyrev, A. S.; Malakhov, A. V.; Mitrofanov, I. G.; Mokrousov, M. I.; Sanin, A. B.; Tretyakov, V.; Vostrukhin, A.

2007-07-01

179

Evaluation of the effects of incorporation rate and depth of water-retentive amendment materials in sports turf constructions  

Microsoft Academic Search

The objective of the current laboratory study was to assess the effects of a number of amendment materials and the depth of incorporation on water retention. 300 mm rootzone profiles were established in 150 mm diameter plastic cylinders over a 50 mm gravel drainage layer. Five amendment materials (sphagnum peat, compost, zeolite, TerraCottem and Stockosorb) were mixed with a medium-coarse

Stanislav Hejduk; Stephen W. Baker; Christian A. Spring

2012-01-01

180

Highly compliant column for tanker mooring and oil production in 1000-m water depth  

SciTech Connect

A two year research project has been carried out, devoted to the design of SPMs for temporary and permanent tanker mooring in 1000 m water depth in the Mediterranean Sea. The main component is a very slender and highly compliant vertical column, tensioned at its top by a proper buoyancy chamber. The column is connected down to the base and to the upper buoyancy chamber through tapered steel terminators, thus ensuring full structural continuity and avoiding any critical mechanical ball joint. A small lattice tower placed on top of the buoyancy chamber, supports deck and facilities. The structure, designed as mooring/loading system, has natural period within the range of the wave periods so that it behaves in resonance conditions, yet the fatigue strength all along the column is adequate. This has been demonstrated through an extensive non-linear dynamic analysis and fatigue evaluation by spectral approach. A two phase transportation/installation procedure and a telescopic assembling of the column have been proposed in order to accomplish marine operations on structures of reasonable size. Furthermore, for the use of this concept as a permanent mooring, an original gravity yoke has been studied for the connection of the tanker to the top of the column. The paper, after a description of the structure configuration, its performance and proposed marine operations, presents the main results of an extensive dynamic-fatigue analysis. What is considered to be new, in this work, are the proposed simple but original structural concept, the installation procedure and the advanced nonlinear dynamic analysis carried out for a correct evaluation of the response of a compliant structure with several resonance conditions in the range of the wave period.

Sebastiani, G.; Brandi, R.; DiLena, F.; Nista, A.

1984-05-01

181

Estimation of the depth to the fresh-water/salt-water interface from vertical head gradients in wells in coastal and island aquifers  

USGS Publications Warehouse

An accurate estimate of the depth to the theoretical interface between fresh, water and salt water is critical to estimates of well yields in coastal and island aquifers. The Ghyben-Herzberg relation, which is commonly used to estimate interface depth, can greatly underestimate or overestimate the fresh-water thickness, because it assumes no vertical head gradients and no vertical flow. Estimation of the interface depth needs to consider the vertical head gradients and aquifer anisotropy that may be present. This paper presents a method to calculate vertical head gradients using water-level measurements made during drilling of a partially penetrating well; the gradient is then used to estimate interface depth. Application of the method to a numerically simulated fresh-water/salt-water system shows that the method is most accurate when the gradient is measured in a deeply penetrating well. Even using a shallow well, the method more accurately estimates the interface position than does the Ghyben-Herzberg relation where substantial vertical head gradients exist. Application of the method to field data shows that drilling, collection methods of water-level data, and aquifer inhomogeneities can cause difficulties, but the effects of these difficulties can be minimized.

Izuka, S. K.; Gingerich, S. B.

1998-01-01

182

Absorbed dose to water reference dosimetry using solid phantoms in the context of absorbed-dose protocols.  

PubMed

For reasons of phantom material reproducibility, the absorbed dose protocols of the American Association of Physicists in Medicine (AAPM) (TG-51) and the International Atomic Energy Agency (IAEA) (TRS-398) have made the use of liquid water as a phantom material for reference dosimetry mandatory. In this work we provide a formal framework for the measurement of absorbed dose to water using ionization chambers calibrated in terms of absorbed dose to water but irradiated in solid phantoms. Such a framework is useful when there is a desire to put dose measurements using solid phantoms on an absolute basis. Putting solid phantom measurements on an absolute basis has distinct advantages in verification measurements and quality assurance. We introduce a phantom dose conversion factor that converts a measurement made in a solid phantom and analyzed using an absorbed dose calibration protocol into absorbed dose to water under reference conditions. We provide techniques to measure and calculate the dose transfer from solid phantom to water. For an Exradin A12 ionization chamber, we measured and calculated the phantom dose conversion factor for six Solid Water phantoms and for a single Lucite phantom for photon energies between 60Co and 18 MV photons. For Solid Water of certified grade, the difference between measured and calculated factors varied between 0.0% and 0.7% with the average dose conversion factor being low by 0.4% compared with the calculation whereas for Lucite, the agreement was within 0.2% for the one phantom examined. The composition of commercial plastic phantoms and their homogeneity may not always be reproducible and consistent with assumed composition. By comparing measured and calculated phantom conversion factors, our work provides methods to verify the consistency of a given plastic for the purpose of clinical reference dosimetry. PMID:16266109

Seuntjens, Jan; Olivares, Marina; Evans, Michael; Podgorsak, Ervin

2005-09-01

183

Seasonal Variations in Particle Motion of Microseisms and monitoring of water content at shallow depths  

NASA Astrophysics Data System (ADS)

There is a long history of study on microseisms, historically regarded as an annoying seismic noise for frequencies between about 0.05 and 0.3 Hz. With the emergence of dense, broadband seismic networks in the world, however, there is clearly an opportunity to carefully analyze microseisms and learn about their sources and the crustal structure in which they travel. The main point of this paper is our discovery of seasonal variations in particle motion of microseisms. We report this result from our analysis of seismic data from California Integrated Seismic Network (CISN) that has more than 150 broadband stations. But we also show some examples from other networks that seem to possess similar characteristics. It was pointed out more than 40 years ago that microseisms consist of Rayleigh waves (e.g. Haubrich et al., 1963). We first confirmed this feature by checking the phase shift between the maximum horizontal motion and the vertical motion. Indeed, we can identify Rayleigh-wave signal by performing this analysis. There exist some other type of energy in microseisms but, in this paper, we focus on the Rayleigh-wave type energy for further analyses. Once we identify the Rayleigh wave signals in microseisms, we can easily determine the direction(s) of energy propagation at a given station. We confirmed that the sources, determined at each station, point toward coasts, which was certainly expected and not surprising. We then discovered, to our surprise, that the ratio of the horizontal amplitude to the vertical (hereafter referred as HZ-ratio) displays seasonal variations. Particle motion is relatively flat in winter (northern hemisphere) and becomes closer to a circle in July. This feature is found at basically all stations with good signal-to-noise ratio that we analyzed. The manner they change with season, especially their frequency dependence, differ from one station to another. This feature is NOT related to the changes in sources of excitation because the HZ-ratio of Rayleigh waves, as it is the ratio for the horizontal and vertical amplitude of the eigenfunction of a local seismic structure, should not change with variations of excitation sources. We argue that this is caused by the changes in water content below each seismic station, especially through changes in groundwater level and the water content in the vadose zone. We have developed theoretical modeling technique and confirmed that it is possible to match data and theory using reasonable numbers for porosity for shallow crust. Apparently, variations of water content at shallow depths, typically within 10-50 m from the surface, amount to changing of the surface boundary conditions for Rayleigh waves. If this model is correct, this feature in microseisms can be used to monitor water content in the shallow crust.

Tanimoto, T.

2004-12-01

184

Experimental evidence of the modulation of a plane wave to oblique perturbations and generation of rogue waves in finite water depth  

NASA Astrophysics Data System (ADS)

We present a laboratory experiment in a large directional wave basin to discuss the instability of a plane wave to oblique side band perturbations in finite water depth. Experimental observations, with the support of numerical simulations, confirm that a carrier wave becomes modulationally unstable even for relative water depths k0h < 1.36 (with k the wavenumber of the plane wave and h the water depth), when it is perturbed by appropriate oblique disturbances. Results corroborate that the underlying mechanism is still a plausible explanation for the generation of rogue waves in finite water depth.

Toffoli, A.; Fernandez, L.; Monbaliu, J.; Benoit, M.; Gagnaire-Renou, E.; Lefèvre, J. M.; Cavaleri, L.; Proment, D.; Pakozdi, C.; Stansberg, C. T.; Waseda, T.; Onorato, M.

2013-09-01

185

The Ecological Response of Carex lasiocarpa Community in the Riparian Wetlands to the Environmental Gradient of Water Depth in Sanjiang Plain, Northeast China  

PubMed Central

The response of Carex lasiocarpa in riparian wetlands in Sanjiang Plain to the environmental gradient of water depth was analyzed by using the Gaussian Model based on the biomass and average height data, and the ecological water-depth amplitude of Carex lasiocarpa was derived. The results indicated that the optimum ecological water-depth amplitude of Carex lasiocarpa based on biomass was [13.45?cm, 29.78?cm], while the optimum ecological water-depth amplitude of Carex lasiocarpa based on average height was [2.31?cm, 40.11?cm]. The intersection of the ecological water-depth amplitudes based on biomass and height confirmed that the optimum ecological water-depth amplitude of Carex lasiocarpa was [13.45?cm, 29.78?cm] and the optimist growing water-depth of Carex lasiocarpa was 21.4?cm. The TWINSPAN, a polythetic and divisive classification tool, was used to classify the wetland ecological series into 6 associations. Result of TWINSPAN matrix classification reflected an obvious environmental gradient in these associations: water-depth gradient. The relation of biodiversity of Carex lasiocarpa community and water depth was determined by calculating the diversity index of each association.

Luan, Zhaoqing; Wang, Zhongxin; Yan, Dandan; Liu, Guihua; Xu, Yingying

2013-01-01

186

The ecological response of Carex lasiocarpa community in the Riparian Wetlands to the environmental gradient of water depth in Sanjiang Plain, Northeast China.  

PubMed

The response of Carex lasiocarpa in riparian wetlands in Sanjiang Plain to the environmental gradient of water depth was analyzed by using the Gaussian Model based on the biomass and average height data, and the ecological water-depth amplitude of Carex lasiocarpa was derived. The results indicated that the optimum ecological water-depth amplitude of Carex lasiocarpa based on biomass was [13.45?cm, 29.78?cm], while the optimum ecological water-depth amplitude of Carex lasiocarpa based on average height was [2.31?cm, 40.11?cm]. The intersection of the ecological water-depth amplitudes based on biomass and height confirmed that the optimum ecological water-depth amplitude of Carex lasiocarpa was [13.45?cm, 29.78?cm] and the optimist growing water-depth of Carex lasiocarpa was 21.4?cm. The TWINSPAN, a polythetic and divisive classification tool, was used to classify the wetland ecological series into 6 associations. Result of TWINSPAN matrix classification reflected an obvious environmental gradient in these associations: water-depth gradient. The relation of biodiversity of Carex lasiocarpa community and water depth was determined by calculating the diversity index of each association. PMID:24065874

Luan, Zhaoqing; Wang, Zhongxin; Yan, Dandan; Liu, Guihua; Xu, Yingying

2013-08-26

187

Halite depositional facies in a solar salt pond: A key to interpreting physical energy and water depth in ancient deposits  

SciTech Connect

Subaqueous deposits of aragonite, gypsum, and halite are accumulating in shallow solar salt ponds constructed in the Pekelmeer, a sea-level salina on Bonaire, Netherlands Antilles. Several halite facies are deposited in the crystallizer ponds in response to difference in water depth and wave energy. Cumulate halite, which originates as floating rafts, is present only along the protected, upwind margins of ponds where low-energy conditions foster their formation and preservation. Cornet crystals with peculiar mushroom- and mortarboard-shaped caps precipitate in centimetre-deep brine sheets within a couple of metres of the upwind or low-energy margins. Downwind from these margins, cornet and chevron halite precipitate on the pond floors in water depths ranging from a few centimetres to {approximately} 60 cm. Halite pisoids with radial-concentric structure are precipitated in the swash zone along downwind high-energy shorelines where they form pebbly beaches. This study suggests that primary halite facies are energy and/or depth dependent and that some primary features, if preserved in ancient halite deposits, can be used to infer physical energy conditions, subenvironments such as low- to high-energy shorelines, and extremely shallow water depths in ancient evaporite basins.

Handford, C.R. (ARCO Oil and Gas Co., Plano, TX (USA))

1990-08-01

188

Stratigraphic source and depth into bedrock control composition of ground water across a buried anticline in central Illinois  

SciTech Connect

Buried beneath glacial drift in Coles, Douglas and Champaign Counties, seven stratigraphic units have been tapped for ground water across a small (ca. 10 x 20 mi.) doubly-plunging anticline, part of the LaSalle Anticlinal Belt. Analyses of groundwater from 78 wells in these units have been obtained from the Illinois State Water Survey's Ground-Water Quality Database. Bedrock sources for the water have been determined from well depth, thickness of drift, and the Geologic Map of the US. Piper diagrams have been prepared for all data, by stratigraphic unit, and by depth of well in each unit. Water types, using the convention of > 50% on a milliequivalents per liter basis to determine dominant cation and anion names, include 38 no dominant cation bicarbonate samples, 33 sodium bicarbonate, 5 sodium chloride and 2 calcium bicarbonate samples. Principal variation among cation composition involves presence of Na + K whereas Mg/Mg + Ca remains relatively constant at 43% (s.d. 4%). Groundwater composition tends to be lower in Na+K and Cl from P[sub 3] and higher in older units. A Chi Square test rejects the hypothesis of independence of water type and stratigraphic unit. Similarly, groundwater composition tends to be lower in Na+K and Cl from P[sub 3] and higher in older units. A Chi Square test rejects the hypothesis of independence of water type and stratigraphic unit. Similarly, groundwater composition tends to be lower in Na+K and Cl from shallower wells and higher from deeper wells. A Chi Square test rejects (P of .0001) the hypothesis of independence of water type and depth of well into bedrock.

DeCastro, R.R.; Corbett, R.G. (Illinois State Univ., Normal, IL (United States). Dept. of Geography-Geology)

1994-04-01

189

A simulation study to identify the sea water depth for the presence of air waves in sea bed logging  

NASA Astrophysics Data System (ADS)

Sea Bed Logging (SBL) is an offshore geophysical technique that can give information about resistivity variation beneath the seafloor. This information is crucial in offshore oil and gas exploration. However, data collected through this technique in shallow water at low frequencies is associated with a problem termed "air wave effect". The air wave effect is a phenomena resulting from Electro-Magnetic (EM) waves produced by the antenna (source) which interact with air-sea interface to generate air waves that diffuse from sea surface to the receivers. These air wave signals dominate the receivers at far offsets to the source and consequently, the refracted signal due the target is hardly distinguishable. The refracted signals from the target being masked by the airwaves can make it difficult to identify the hydrocarbon reservoir. The aim of this study is to investigate the sea water depth for the presence of air waves. Synthetic data are generated by simulating SBL environment without Hydro-Carbon (HC) target and varying the sea water depth from 1000m to 100m with the interval of 100m. The simulated distances for the source-receiver separation (offset) are divided into five ranges. The magnitude versus offset plot together with the Friedman and Wilcoxon statistical test are used to analyze the data. Results show that the air waves are present at 400m of sea water depth and below.

Abdulkarim, Muhammad; Shafie, Afza; Yahya, Noorhana Binti; Razali, Radzuan; Ahmad, Wan Fatimah Wan

2012-09-01

190

Use of artificial neural networks for predicting optimal alum doses and treated water quality parameters  

Microsoft Academic Search

Coagulation is an important component of water treatment. Determination of optimal coagulant doses is vital, as insufficient dosing will result in undesirable treated water quality. On the other hand, doses that are too high can result in high cost and health problems related to high levels of residual aluminium (if alum is used as the coagulant). Traditionally, jar tests are

Holger R. Maier; Nicolas Morgan; Christopher W. K. Chow

2004-01-01

191

Specification of absorbed dose to water using model-based dose calculation algorithms for treatment planning in brachytherapy.  

PubMed

Model-based dose calculation algorithms (MBDCAs), recently introduced in treatment planning systems (TPS) for brachytherapy, calculate tissue absorbed doses. In the TPS framework, doses have hereto been reported as dose to water and water may still be preferred as a dose specification medium. Dose to tissue medium Dmed then needs to be converted into dose to water in tissue Dw,med. Methods to calculate absorbed dose to differently sized water compartments/cavities inside tissue, infinitesimal (used for definition of absorbed dose), small, large or intermediate, are reviewed. Burlin theory is applied to estimate photon energies at which cavity sizes in the range 1 nm-10 mm can be considered small or large. Photon and electron energy spectra are calculated at 1 cm distance from the central axis in cylindrical phantoms of bone, muscle and adipose tissue for 20, 50, 300 keV photons and photons from (125)I, (169)Yb and (192)Ir sources; ratios of mass-collision-stopping powers and mass energy absorption coefficients are calculated as applicable to convert Dmed into Dw,med for small and large cavities. Results show that 1-10 nm sized cavities are small at all investigated photon energies; 100 µm cavities are large only at photon energies <20 keV. A choice of an appropriate conversion coefficient Dw, med/Dmed is discussed in terms of the cavity size in relation to the size of important cellular targets. Free radicals from DNA bound water of nanometre dimensions contribute to DNA damage and cell killing and may be the most important water compartment in cells implying use of ratios of mass-collision-stopping powers for converting Dmed into Dw,med. PMID:23528349

Tedgren, Åsa Carlsson; Carlsson, Gudrun Alm

2013-03-26

192

Effective upwelling irradiance depths in turbid waters: a spectral analysis of origins and fate.  

PubMed

The spectral distribution of upwelling and downwelling irradiance were used to estimate the effective upwelling irradiance depth as well as examine the angular distribution of the downwelling radiance. The effective upwelling depth was seen to undergo spectral "shifts" in wavelength maxima in relation to elevated particulate concentrations. Wavelengths of the UVA minimum and mid visible maximum depths were found to be shifted to higher wavelengths (red shifted) at high particulate concentrations, while expected minimums at chlorophyll and phycocyanin absorption peaks and in the NIR were shifted to lower wavelengths (blue shifted). By comparing upwelling and downwelling irradiance profiles, the wavelength limits of the asymptotic angular radiance distribution were found to correspond to the visible spectral domain (390-740 nm). PMID:21503026

Ma, Ronghua; Jiang, Guangjia; Duan, Hongtao; Bracchini, Luca; Loiselle, Steven

2011-04-11

193

Depth dose distribution study within a phantom torso after irradiation with a simulated Solar Particle Event at NSRL  

Microsoft Academic Search

The adequate knowledge of the radiation environment and the doses incurred during a space mission is essential for estimating an astronaut's health risk. The space radiation environment is complex and variable, and exposures inside the spacecraft and the astronaut's body are com-pounded by the interactions of the primary particles with the atoms of the structural materials and with the body

Thomas Berger; Daniel Matthiä; Christine Koerner; Kerry George; Jordan Rhone; Francis A. Cucinotta; Guenther Reitz

2010-01-01

194

Water and nitrate distributions as affected by layered-textural soil and buried dripline depth under subsurface drip fertigation  

Microsoft Academic Search

Laboratory experiments were conducted to investigate the distributions of water and nitrate from a buried dripline discharging\\u000a an ammonium nitrate solution in uniform and layered-textural soils. Two layered soils, a sandy-over-loam soil (SL) and a loam-sandy-loam\\u000a soil (LSL), and two uniform soils of sandy (S) and loam (L) were tested. The experimental results demonstrated that dripline\\u000a depth and layered-textural soil

Jiusheng LiYuchun Liu; Yuchun Liu

195

delta18O values of coexisting brachiopods and fish: Temperature differences and estimates of paleo water depths  

Microsoft Academic Search

To estimate vertical thermal gradients and paleo water depths to marine platforms we present a new method based on the difference between delta18O values of contemporaneous brachiopod carbonate and fish phosphate. Present-day marine fauna of well-known ecology from the surface to the sea floor record isotopic temperatures that agree with measured temperatures. We predict distributions of isotopic data that result

Stéphanie Picard; Jean-Pierre Garcia; Christophe Lécuyer; Simon M. F. Sheppard; Henri Cappetta; Christian C. Emig

1998-01-01

196

The Incredible Shrinking Cup Lab: Connecting with Ocean and Great Lakes Scientists to Investigate the Effect of Depth and Water Pressure on Polystyrene  

ERIC Educational Resources Information Center

|Pressure increases rapidly with depth in a water body. Ocean and Great Lakes scientists often use this physical feature of water as the basis of a fun pastime performed aboard research vessels around the world: the shrinking of polystyrene cups. Depending on the depth to which the cups are deployed, the results can be quite striking! Capitalizing…

Rose, Chantelle M.; Adams, Jacqueline M.; Hinchey, Elizabeth K.; Nestlerode, Janet A.; Patterson, Mark R.

2013-01-01

197

An auger depth profile study of corrosion-inhibiting films formed under cooling water conditions  

SciTech Connect

Various corrosion inhibitors were evaluated in a dynamic corrosion test loop which is equipped with deposit and corrosion monitors and with pH and blowdown controllers. The Auger depth profiles were used to study the compositions and thicknesses of films formed by these corrosion inhibitors as a function of pH. The profile study is discussed in this paper.

Schreifels, J.; Gailey, R.; Goewert, S.; O'Brien, M.; Jost, S. (George Mason Univ., Fairfax, VA (USA)); Labine, P. (807 Garonne, Manchester, MO (US))

1989-05-01

198

Dose calculations for nuclear criticality accidents shielded by large amounts of water.  

National Technical Information Service (NTIS)

A nuclear criticality accident under a large amount of water will yield, at first analysis, only a trivial dose to any person standing above the water surface. Attenuation by 15 ft of water reduces the gamma dose substantially, and virtually eliminates do...

K. N. Schwinkendorf A. D. Wilcox S. P. Roblyer H. Toffer

1992-01-01

199

Dose and dose rate dependency of lipid peroxide formation in rat tissues by low level contamination with tritiated water  

NASA Astrophysics Data System (ADS)

The changes in peroxide level in different tissues (liver, kidney, small intestine, spleen, bone marrow) of rats exposed to low levels of tritiated water were investigated in relation to tissue radiosensitivity, the irradiation dose and the dose rate domain. The radiation exposure was performed by internal contamination of rats with tritiated water, in the 0 50cGy dose domain, with dose rates in the range of 0.01 2cGy/day. For the lower dose rates (< 0.35cGy/day) the peroxide levels did not increase for doses up to 10cGy, while a dose rate of 1 1.75cGy/day induced an increase in peroxide levels starting at 5cGy. The increases were more significant for the tissues with higher radiosensitivity: spleen, small intestine and bone marrow. For the 4.2 7cGy dose domain and very low dose rates, up to 0.1cGy/day, the peroxide level seemed to have an inverse dose rate dependency. Nous avons étudié la modification du niveau des peroxydes lipidiques pour des tissus ayant des radiosensibilités différentes (foie, rein, rate, intestin grêle, moelle osseuse) après irradiation de rats par contamination interne à l'eau tritiée dans le domaine des faibles doses (0 - 50 cGy) et faibles débits de doses (0,01 - 2 cGy/jour). L'irradiation au débit de dose inférieure à 0,35 cGy/jour, n'augmente le niveau de peroxydation que pour des doses supérieures à 10 cGy. Par contre, le débit de 1-1.75 cGy/jour induit une augmentation significative du paramètre étudié à partir de la dose de 5 cGy. Cette augmentation est plus accentuée pour la rate, l'intestin grêle et la moelle osseuse. Aux doses de 4,2-7 cGy et débits de doses très faibles (< 0.1 cGy), le niveau de peroxydation montre une dépendance inverse par rapport au débit de dose.

Moisoi, N.; Petcu, I.

1999-01-01

200

Waveform tomography at a ground water contamination site: comparison with depth migration  

NASA Astrophysics Data System (ADS)

We have previously applied 2D acoustic waveform tomography to surface and VSP seismic data from a groundwater contamination site, where the results were compared with images from a 3D reflection dataset. In this study, 2-D waveform tomograms from the reflection dataset acquired at Hill Air Force Base (HAFB) are extensively compared with depth migrated images from the same dataset. Comparisons of tomograms and depth migrated images from a small subset of the data show good agreement in terms of the structural features identified in both types of images. In terms of shallow seismic imaging, the advantages of waveform tomography over depth migration are that the former can be applied using both direct and refracted waves, eliminating a number of processing steps while achieving resolution scales similar to depth migration. Further more, the images provide quantitative estimates of material property perturbations. The disadvantage of waveform tomography is its computational expense when compared with migration. This restricts waveform tomography to 2D applications at present. Thus far we have applied acoustic waveform tomography to first arrival waveforms from land data as an approximation to the elastic case. To improve the applicability of waveform inversion, we present initial efforts to develop a form of elastic waveform tomography in the frequency-space domain. The frequency domain approach has distinct computational advantages over time domain in 2D applications. The technique is being developed in Cartesian as well as cylindrical coordinates to take the curvature of the Earth into account, in order to allow application to teleseismic data.

Gao, F.; Fradelizio, G.; Levander, A.; Pratt, G.; Zelt, C.; Symes, W.

2004-12-01

201

Surface Waves on Water with Depths Less than the Boundary-Layer Thickness  

Microsoft Academic Search

Equations are derived for the complex wavenumber for plane surface waves in liquids of low viscosity with depths from one-fifth to two-thirds of the boundary-layer thickness. For capillary waves, the values of the real wavenumber and of the spatial absorption coefficient are approximately proportional to (??)1?4, where ? is the kinematic coefficient of viscosity and ? is the real angular

N. L. Walbridge

1972-01-01

202

Core Top 14C Ages as a Function of Latitude and Water Depth on the Ontong-Java Plateau  

NASA Astrophysics Data System (ADS)

Radiocarbon measurements on core tops from the Ontong-Java plateau confirm a previous finding by Berger and Killingley [1982] that at any given water depth, cores taken on the equator have higher accumulation rates and younger core top ages than their off-equator counterparts. Further, these new results fortify the conclusion by Broecker et al. [1991] that the increase in core top radiocarbon age with water depth rules out homogeneous dissolution within the pore waters as the dominant mechanism. Either most of the dissolution must occur prior to burial or it must occur during the first pass through the respiration-CO2-rich upper pore waters after which the calcite grains become armored against further dissolution. A puzzling aspect of this new data set is that despite the sizable difference in accumulation rate, the extent of dissolution as measured by either the CaCO3 content or the ratio of CaCO3 in the >150-µm size fraction to that in the < 63-µm fraction is no different off than on the equator. In order to reconcile the results of this study with those obtained by Hales and Emerson [1996] using in situ electrodes, it is necessary to call upon calcite armoring.

Broecker, Wallace S.; Clark, Elizabeth; McCorkle, Daniel C.; Hajdas, Irka; Bonani, Georges

1999-02-01

203

The influence of the depth of the ground water table on free field road traffic-induced vibrations  

NASA Astrophysics Data System (ADS)

This paper describes the influence of seasonal variations of the ground water table on free field traffic-induced vibrations. The passage of a truck on two types of road unevenness is considered: a joint in a road pavement consisting of concrete plates and a speed bump with a sinusoidal profile. Free field vibrations are computed with a two-step solution procedure, where the computation of the vehicle axle loads is decoupled from the solution of the road-soil interaction problem. The impedance of the soil is calculated using a boundary element method, based on the Green's functions for a dry layer on top of a saturated half-space. It is demonstrated that, in the low-frequency range of interest, wave propagation in the saturated half-space can be modelled with an equivalent single phase medium as an alternative to Biot's poroelastic theory for saturated porous media. The relation between the free field velocity and the depth of the ground water table is dominated by three phenomena: (1) the compressibility of the soil decreases due to the presence of the pore water, (2) the ground water table introduces a layering of the soil which may cause resonance of the dry layer and (3) refracted P-waves in the dry layer interfere with surface waves. If the depth of the ground water table is large with respect to the wavelength of the vibrations in the soil, the response tends to the response of a dry half-space. The average free field velocity is equal to the velocity in the absence of ground water. If the depth of the ground water table is small with respect to the wavelength of the vibrations in the soil, the response tends to the response of a saturated half-space and resonance of the dry layer does not occur. The average free field velocity is smaller than the velocity in the absence of ground water. The interference of refracted P-waves and surface waves causes an additional oscillation of the response as a function of the excitation frequency and the distance between the road and the receiver. Copyright

Schevenels, M.; Degrandec, G.; Lombaert, G.

2004-04-01

204

Defining restoration targets for water depth and salinity in wind-dominated Spartina patens (Ait.) Muhl. coastal marshes  

USGS Publications Warehouse

Coastal wetlands provide valued ecosystem functions but the sustainability of those functions often is threatened by artificial hydrologic conditions. It is widely recognized that increased flooding and salinity can stress emergent plants, but there are few measurements to guide restoration, management, and mitigation. Marsh flooding can be estimated over large areas with few data where winds have little effect on water levels, but quantifying flooding requires hourly measurements over long time periods where tides are wind-dominated such as the northern Gulf of Mexico. Estimating salinity of flood water requires direct daily measurements because coastal marshes are characterized by dynamic salinity gradients. We analyzed 399,772 hourly observations of water depth and 521,561 hourly observations of water salinity from 14 sites in Louisiana coastal marshes dominated by Spartina patens (Ait.) Muhl. Unlike predicted water levels, observed water levels varied monthly and annually. We attributed those observed variations to variations in river runoff and winds. In stable marshes with slow wetland loss rates, we found that marsh elevation averaged 1 cm above mean high water, 15 cm above mean water, and 32 cm above mean low water levels. Water salinity averaged 3.7 ppt during April, May, and June, and 5.4 ppt during July, August, and September. The daily, seasonal, and annual variation in water levels and salinity that were evident would support the contention that such variation be retained when designing and operating coastal wetland management and restoration projects. Our findings might be of interest to scientists, engineers, and managers involved in restoration, management, and restoration in other regions where S. patens or similar species are common but local data are unavailable. ?? 2009 Elsevier B.V.

Nyman, J. A.; La, Peyre, M. K.; Caldwell, A.; Piazza, S.; Thom, C.; Winslow, C.

2009-01-01

205

Initial yield to depth relation for water wells drilled into crystalline bedrock--Pinardville quadrangle, New Hampshire.  

PubMed

A model is proposed to explain the statistical relations between the mean initial water well yields from eight time increments from 1984 to 1998 for wells drilled into the crystalline bedrock aquifer system in the Pinardville area of southern New Hampshire and the type of bedrock, mean well depth, and mean well elevation. Statistical analyses show that the mean total yield of drilling increments is positively correlated with mean total well depth and mean well elevation. In addition, the mean total well yield varies with rock type from a minimum of 46.9 L/min (12.4 gpm) in the Damon Pond granite to a maximum of 74.5 L/min (19.7 gpm) in the Permian pegmatite and granite unit. Across the eight drilling increments that comprise 211 wells each, the percentages of very low-yield wells (1.9 L/min [0.5 gpm] or less) and high-yield wells (151.4 L/min [40 gpm] or more) increased, and those of intermediate-yield wells decreased. As housing development progressed during the 1984 to 1998 interval, the mean depth of the wells and their elevations increased, and the mix of percentages of the bedrock types drilled changed markedly. The proposed model uses a feed-forward mechanism to explain the interaction between the increasing mean elevation, mean well depth, and percentages of very low-yielding wells and the mean well yield. The increasing percentages of very low-yielding wells through time and the economics of the housing market may control the system that forces the mean well depths, percentages of high-yield wells, and mean well yields to increase. The reason for the increasing percentages of very low-yield wells is uncertain, but the explanation is believed to involve the complex structural geology and tectonic history of the Pinardville quadrangle. PMID:11554245

Drew, L J; Schuenemeyer, J H; Armstrong, T R; Sutphin, D M

206

Map showing depth to pre-Cenozoic basement in the Death Valley ground-water model area, Nevada and California  

SciTech Connect

This map shows the depth to pre-Cenozoic basement in the Death Valley ground-water model area. It was prepared utilizing gravity (Ponce and others, 2001), geologic (Jennings and others, 1977; Stewart and Carlson, 1978), and drill-hole information. Geophysical investigations of the Death Valley ground-water model area are part of an interagency effort by the U.S. Geological Survey (USGS) and the U.S. Department of Energy (Interagency Agreement DE-AI08-96NV11967) to help characterize the geology and hydrology of southwestern Nevada and parts of California. The Death Valley ground-water model is located between lat 35 degrees 00' and 38 degrees 15' N., and long 115 degrees and 118 degrees W.

Blakely, R.J.; Ponce, D.A.

2002-03-12

207

Fluid flow during slab unbending and dehydration: Implications for intermediate-depth seismicity, slab weakening and deep water recycling  

NASA Astrophysics Data System (ADS)

Subducting oceanic plates carry a considerable amount of water from the surface down to mantle depths and contribute significantly to the global water cycle. A part of these volatiles stored in the slab is expelled at intermediate depths (70-300 km) where dehydration reactions occur. However, despite the fact that water considerably affects many physical properties of rocks, not much is known about the fluid flow path and the interaction with the rocks through which volatiles flow in the slab interior during its dehydration. We performed thermomechanical models (coupled with a petrological database and with incompressible aqueous fluid flow) of a dynamically subducting and dehydrating oceanic plate. Results show that, during slab dehydration, unbending stresses drive part of the released fluids into the cold core of the plate toward a level of strong tectonic under-pressure and neutral (slab-normal) pressure gradients. Fluids progressively accumulate and percolate updip along such a layer forming, together with the upper hydrated layer near the top of the slab, a Double Hydrated Zone (DHZ) where intermediate-depth seismicity could be triggered. The location and predicted mechanics of the DHZ would be consistent with seismological observations regarding Double Seismic Zones (DSZs) found in most subduction zones and suggests that hydrofracturing could be the trigger mechanism for observed intermediate-depth seismicity. In the light of our results, the lower plane of the DSZ is more likely to reflect a layer of upward percolating fluid than a level of mantle dehydration. In our models, a 20-30 km thick DSZ forms in relatively old oceanic plates without requiring an extremely deep slab hydration prior to subduction. The redistribution of fluids into the slab interior during slab unbending also has important implications for slab weakening and the deep water cycle. We estimate that, over the whole of Earth's history, a volume of water equivalent to around one to two oceans can be stored in nominally anhydrous minerals of the oceanic lithosphere and transported to the transition zone by this mechanism, suggesting that mantle regassing could have been efficient even without invoking the formation of high pressure hydrous minerals.

Faccenda, Manuele; Gerya, Taras V.; Mancktelow, Neil S.; Moresi, Louis

2012-01-01

208

Discoloration of polyvinyl chloride (PVC) tape as a proxy for water-table depth in peatlands: validation and assessment of seasonal variability  

USGS Publications Warehouse

Summary: 1. Discoloration of polyvinyl chloride (PVC) tape has been used in peatland ecological and hydrological studies as an inexpensive way to monitor changes in water-table depth and reducing conditions. 2. We investigated the relationship between depth of PVC tape discoloration and measured water-table depth at monthly time steps during the growing season within nine kettle peatlands of northern Wisconsin. Our specific objectives were to: (1) determine if PVC discoloration is an accurate method of inferring water-table depth in Sphagnum-dominated kettle peatlands of the region; (2) assess seasonal variability in the accuracy of the method; and (3) determine if systematic differences in accuracy occurred among microhabitats, PVC tape colour and peatlands. 3. Our results indicated that PVC tape discoloration can be used to describe gradients of water-table depth in kettle peatlands. However, accuracy differed among the peatlands studied, and was systematically biased in early spring and late summer/autumn. Regardless of the month when the tape was installed, the highest elevations of PVC tape discoloration showed the strongest correlation with midsummer (around July) water-table depth and average water-table depth during the growing season. 4. The PVC tape discoloration method should be used cautiously when precise estimates are needed of seasonal changes in the water-table.

Booth, Robert K.; Hotchkiss, Sara C.; Wilcox, Douglas A.

2005-01-01

209

Exploration of water jet generated by Q-switched laser induced water breakdown with different depths beneath a flat free surface.  

PubMed

The dynamics of a water jet on a flat free surface are investigated using a nanosecond pulsed laser for creating an oscillating bubble with different depths beneath the free surface. A thin jet is shown to deform a crater surface resulted from surface depression and cause a circular ring-shaped crater on the connection surface between the crater of surface depression and the thin jet. The collapse of this circular ring-shaped crater is proposed to the crown-like formation around a thick jet. The evolution of the bubble depth suggests a classification of four distinctive ranges of the bubble depths: non-crown formation when the parameter of bubble depth over the maximum bubble radius ? ? 0.5, unstable crown formation when 0.5 ? ? ? 0.6, crown-like structure with a complete crown wall when 0.6 ? ? ? 1.1, and non-crown formation when 1.1 ? ?. Furthermore, the orientation of the crown wall gradually turns counterclockwise to vertical direction with increasing ? from 0.5 to 1.1, implying a high correlation between the orientation of the crown wall and the depth of the bubble. This correlation is explained and discussed by the directional change of the jet eruption from the collapse of circular ring-shaped crater. PMID:23388938

Chen, Ross C C; Yu, Y T; Su, K W; Chen, J F; Chen, Y F

2013-01-14

210

Determination of water absorbed dose in a carbon ion beam using thimble ionization chambers  

Microsoft Academic Search

The method to measure absorbed dose to water in a field of carbon ions as applied for the heavy ion therapy project at the Heavy Ion Research Laboratory in Darmstadt (GSI), Germany, is described in detail. Thimble ionization chambers with a water absorbed calibration factor are applied. The dose obtained with this method was compared with that obtained at the

G H Hartmann; P Heeg; C P Karger

211

A multiproxy study of Holocene water-depth and environmental changes in Lake St Ana, Eastern Carpathian Mountains, Romania  

NASA Astrophysics Data System (ADS)

This study presents the results of a multi-disciplinary investigation carried out on the sediment of a crater lake (Lake Saint Ana, 950 m a.s.l.) from the Eastern Carpathian Mountains. The lake is set in a base-poor volcanic environment with oligotrophic and slightly acidic water. Loss-on-ignition, major and trace element, pollen, plant macrofossil and siliceous algae analyses were used to reconstruct Holocene environmental and water-depth changes. Diatom-based transfer functions were applied to estimate the lake's trophic status and pH, while reconstruction of the water-depth changes was based on the plant macrofossil and diatom records. The lowest Holocene water-depths were found between 9,000 and 7,400 calibrated BP years, when the crater was occupied by Sphagnum-bog and bog-pools. The major trend from 7,400 years BP was a gradual increase, but the basin was still dominated by poor-fen and poor fen-pools. Significant increases in water-depth, and meso/oligotrophic lake conditions were found from 5,350(1), 3,300(2) and 2,700 years BP. Of these, the first two coincided with major terrestrial vegetation changes, namely the establishment of Carpinus betulus on the crater slope (1), and the replacement of the lakeshore Picea abies forest by Fagus sylvatica (2). The chemical record clearly indicated significant soil changes along with the canopy changes (from coniferous to deciduous), that in turn led to increased in-lake productivity and pH. A further increase in water-depth around 2,700 years BP resulted in stable thermal stratification and hypolimnetic anoxia that via P-release further increased in-lake productivity and eventually led to phytoplankton blooms with large populations of Scenedesmus cf. S. brasiliensis. High productivity was depressed by anthropogenic lakeshore forest clearances commencing from ca. 1,000 years BP that led to the re-establishment of Picea abies on the lakeshore and consequent acidification of the lake-water. On the whole, these data allow the following main inference to be made: Lake Saint Ana is a vulnerable ecosystem; hydrological, biological and chemical processes in the lake are heavily influenced by the lakeshore forest and the soil underlying it. In-lake productivity is higher under deciduous canopy and litter, and considerably repressed by coniferous canopy and litter. The lake today subsists in a managed environment, that is however far from its natural state. This would be a dense Fagus sylvatica forest supplying more nutrients and keeping up a more productive in-lake flora and fauna. An overview of the regional Holocene lake-level records suggests that the general lake-level trends of this study agree with other records in the region, except for the lat 2,700 years, for which conflicting trends were found. The pollen based palaeo-precipitation record in NW Romania signals lower precipitation, while our, and some other records, signal significant increase in available moisture. Further studies are needed to resolve this problem.

Magyari, E. K.; Buczkó, K.; Braun, M.; Jakab, G.

2009-04-01

212

Tiefenprofile der anorganisch-chemischen Zusammensetzung von Bodenwasser in der ungesaettigten Zone. (Depth profiles of the inorganic chemical composition of soil water in the unsaturated zone).  

National Technical Information Service (NTIS)

Soil water up to a depth of 4 m below ground surface was analysed for its inorganic-chemical composition. It was obtained as 'soil solution' by centrifuging original moist soil samples. The analysis provides depth profiles of the concentration of the majo...

J. Hoess

1992-01-01

213

Utilizing Depth of Colonization of Seagrasses to Develop Numeric Water Quality Criteria for Florida Estuaries  

EPA Science Inventory

US EPA is working with state and local partners in Florida to develop numeric water quality criteria to protect estuaries from nutrient pollution. Similar to other nutrient management programs in Florida, EPA is considering status of seagrass habitats as an indicator of biologic...

214

Minimum ecological water depth of a typical stream in Taihu Lake Basin, China  

Microsoft Academic Search

Minimum ecological instream water requirements are important for maintaining basic ecological functions. Characterized by its location and the effects of human activities, successful application significantly depends on the similarity in natural environment and biology. The Mengjin Stream was selected as a typical stream in the Taihu Lake Basin, which is located in the lower reaches of the Yangtze River, to

Junfeng Gao; Yongnian Gao; Guangzhu Zhao; Georg Hörmann

2010-01-01

215

SUGARCANE GROWTH, MORPHOLOGICAL, AND PHOTOSYNTHETIC RESPONSES TO WATER-TABLE DEPTHS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Sugarcane (Saccharum spp.) is the primary crop on the Histosols of the Everglades Agricultural Area (EAA), where undesirably high water tables are increasing in occurrence and duration. Improved understanding of sugarcane responses to these conditions could help develop cultivars and agronomic stra...

216

Soil Water Storage and Rooting Depth: Key Factors Controlling Recharge on Rangelands  

Technology Transfer Automated Retrieval System (TEKTRAN)

The practice of removing woody vegetation to enhance water supply in semiarid rangelands in the USA continues to generate considerable interest, even though past research has yielded apparently contradictory results concerning its efficacy. In an attempt to elucidate the factors that determine wheth...

217

Tillage depth and timing effects on soil water profiles in two semiarid soils  

Technology Transfer Automated Retrieval System (TEKTRAN)

The two-year winter wheat--fallow rotation continues to be the most profitable and productive cropping system in much of the Pacific Northwest, USA. Sustainability of soils in the region depends on our ability to halt or greatly reduce wind and water erosion. An incomplete understanding of how tille...

218

Assessment of satellite derived diffuse attenuation coefficients and euphotic depths in south Florida coastal waters  

EPA Science Inventory

Optical data collected in coastal waters off South Florida and in the Caribbean Sea between January 2009 and December 2010 were used to evaluate products derived with three bio-optical inversion algorithms applied to MOIDS/Aqua, MODIS/Terra, and SeaWiFS satellite observations. Th...

219

EFFECTS OF FLOW DEPTH ON WATER FLOW AND SOLUTE TRANSPORT IN FURROW IRRIGATION: FIELD DATA ANALYSIS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Because of field-scale heterogeneity in soil hydraulic and solute transport properties, relatively large-scale experiments are now increasingly believed to be critical to better understand and predict the movement of water and dissolved solutes under field conditions. In this study, five field exper...

220

Effect of different pre-sowing water application depths on wheat yield under spate irrigation in Dera Ismael Khan District of Pakistan  

Microsoft Academic Search

Spate irrigation is a method of flood water harvesting, practiced in Dera Ismael Khan (D.I. Khan), Pakistan for agricultural production for the last several hundred years in which during monsoon period flood water is used for irrigation before wheat sowing. A field study on the effect of different pre-sowing water application depths on the yield of wheat was conducted during

M. J. Khan; A. Razzaq; M. K. Khattak; L. Garcia

2009-01-01

221

Particle telescopes as a tool for assessment of depth-dose curves in human phantom and for radiation environment measurements during deep space missions  

NASA Astrophysics Data System (ADS)

Possible limitations imposed by the adverse effects of long-term exposure to cosmic radiation is a major obstacle to human space exploration. Concerning the human exploration of Mars, the radiation exposures to be received in transit to Mars and on the Mars surface have to be assessed. The evaluation of the radiation risk is needed concerning the spacecraft and Martian basis design, the arrangements to make in case of SPE and the location of a Martian basis. The current models for radiation risk assessment lead to evaluations with very large uncertainties because of the lack of knowledge of i) the source term (precise radiation composition, energy spectrum, flux) and the influence of the Martian atmosphere and magnetic field, ii) the different interactions of cosmic radiations in matter needed for the calculation of shielding or the dose in the human body and, iii) the biological effects of cosmic particles, especially HZE particles. For the estimation of the organ doses, and thus the radiation risk, measurements in human phantoms are essential. A method and a particle telescope Liulin-5 was developed for investigation of the radiation environment dynamics within a sphere tissue-equivalent phantom on ISS. Energy deposition spectra, linear energy transfer spectra, flux and dose rates for protons and the biologically-relevant heavy ion components of the galactic cosmic radiation will be measured simultaneously with near real time resolution at different depths of the phantom's radial channel. The dose in intermediate points will be determined by interpolation. Data obtained will be used to estimate the radiation risk to the crewmembers, verify the models of radiation environment, validate body transport model and correlate organ level dose to skin dose. Adaptations of the instrument are under development for radiation monitoring outside the phantom. These techniques could be used for investigation of the radiation hazards during future exploratory missions through unmanned interplanetary missions, as well as a part of the radiation safety system for manned deep space missions. Described are functional requirements to the instrumentation and technical specifications.

Semkova, J.; Koleva, R.; Todorova, G.; Kanchev, N.; Petrov, V.; Shurshakov, V.; Benghin, V.; Tchhernykh, I.

222

Comparison between absorbed dose to water standards established by water calorimetry at the LNE-LNHB and by application of international air-kerma based protocols for kilovoltage medium energy x-rays.  

PubMed

Nowadays, the absorbed dose to water for kilovoltage x-ray beams is determined from standards in terms of air-kerma by application of international dosimetry protocols. New standards in terms of absorbed dose to water has just been established for these beams at the LNE-LNHB, using water calorimetry, at a depth of 2 cm in water in accordance with protocols. The aim of this study is to compare these new standards in terms of absorbed dose to water, to the dose values calculated from the application of four international protocols based on air-kerma standards (IAEA TRS-277, AAPM TG-61, IPEMB and NCS-10). The acceleration potentials of the six beams studied are between 80 and 300 kV with half-value layers between 3.01 mm of aluminum and 3.40 mm of copper. A difference between the two methods smaller than 2.1% was reported. The standard uncertainty of water calorimetry being below 0.8%, and the one associated with the values from protocols being around 2.5%, the results are in good agreement. The calibration coefficients of some ionization chambers in terms of absorbed dose to water, established by application of calorimetry and air-kerma based dosimetry protocols, were also compared. The best agreement with the calibration coefficients established by water calorimetry was found for those established with the AAPM TG-61 protocol. PMID:23563051

Perichon, N; Rapp, B; Denoziere, M; Daures, J; Ostrowsky, A; Bordy, J-M

2013-04-08

223

Comparison between absorbed dose to water standards established by water calorimetry at the LNE-LNHB and by application of international air-kerma based protocols for kilovoltage medium energy x-rays  

NASA Astrophysics Data System (ADS)

Nowadays, the absorbed dose to water for kilovoltage x-ray beams is determined from standards in terms of air-kerma by application of international dosimetry protocols. New standards in terms of absorbed dose to water has just been established for these beams at the LNE-LNHB, using water calorimetry, at a depth of 2 cm in water in accordance with protocols. The aim of this study is to compare these new standards in terms of absorbed dose to water, to the dose values calculated from the application of four international protocols based on air-kerma standards (IAEA TRS-277, AAPM TG-61, IPEMB and NCS-10). The acceleration potentials of the six beams studied are between 80 and 300 kV with half-value layers between 3.01 mm of aluminum and 3.40 mm of copper. A difference between the two methods smaller than 2.1% was reported. The standard uncertainty of water calorimetry being below 0.8%, and the one associated with the values from protocols being around 2.5%, the results are in good agreement. The calibration coefficients of some ionization chambers in terms of absorbed dose to water, established by application of calorimetry and air-kerma based dosimetry protocols, were also compared. The best agreement with the calibration coefficients established by water calorimetry was found for those established with the AAPM TG-61 protocol.

Perichon, N.; Rapp, B.; Denoziere, M.; Daures, J.; Ostrowsky, A.; Bordy, J.-M.

2013-05-01

224

The radial depth–dose distribution of a 188W\\/188Re ? line source measured with novel, ultra-thin TLDs in a PMMA phantom: comparison with Monte Carlo simulations  

Microsoft Academic Search

The radial depth–dose distribution of a prototype 188W\\/188Re ? particle line source of known activity has been measured in a PMMA phantom, using a novel, ultra-thin type of LiF:Mg,Cu,P thermoluminescent detector (TLD). The measured radial dose function of this intravascular brachytherapy source agrees well with MCNP4C Monte Carlo simulations, which indicate that 188Re accounts for ?99% of the dose between

Dennis R Schaart; Adrie J J Bos; August J M Winkelman; Martijn C Clarijs

2002-01-01

225

Influence of subhumid climate and water table depth on groundwater recharge in shallow outwash aquifers  

Microsoft Academic Search

Hypothetical one-dimensional models of unsaturated flow were used to estimate the probability of groundwater recharge to shallow, glacial outwash aquifers. Simulations were supported by field data, previous three-dimensional modeling, and cross-sectional models of water table response to precipitation events for a research area in northern Alberta, Canada. Groundwater recharge rates were found to depend on the year-to-year climate variation, the

B. D. Smerdon; C. A. Mendoza; K. J. Devito

2008-01-01

226

Evaluating the role of higher order nonlinearity in water of finite and shallow depth with a direct numerical simulation method of Euler equations  

NASA Astrophysics Data System (ADS)

In deep water, the dynamics of surface gravity waves is dominated by the instability of wave packets to side band perturbations. This mechanism, which is a nonlinear third order in wave steepness effect, can lead to a particularly strong focusing of wave energy, which in turn results in the formation of waves of very large amplitude also known as freak or rogue waves [1]. In finite water depth, however, the interaction between waves and the ocean floor induces a mean current. This subtracts energy from wave instability and causes it to cease for relative water depth , where k is the wavenumber and h the water depth [2]. Yet, this contradicts field observations of extreme waves such as the infamous 26-m "New Year" wave that have mainly been recorded in regions of relatively shallow water . In this respect, recent studies [3] seem to suggest that higher order nonlinearity in water of finite depth may sustain instability. In order to assess the role of higher order nonlinearity in water of finite and shallow depth, here we use a Higher Order Spectral Method [4] to simulate the evolution of surface gravity waves according to the Euler equations of motion. This method is based on an expansion of the vertical velocity about the surface elevation under the assumption of weak nonlinearity and has a great advantage of allowing the activation or deactivation of different orders of nonlinearity. The model is constructed to deal with an arbitrary order of nonlinearity and water depths so that finite and shallow water regimes can be analyzed. Several wave configurations are considered with oblique and collinear with the primary waves disturbances and different water depths. The analysis confirms that nonlinearity higher than third order play a substantial role in the destabilization of a primary wave train and subsequent growth of side band perturbations.

Fernandez, L.; Toffoli, A.; Monbaliu, J.

2012-04-01

227

Determination of the contribution of livestock water ingestion to dose from the cow-milk pathway. Hanford Environmental Dose Reconstruction Project: Dose code recovery activities, Calculation 002  

SciTech Connect

As part of the Hanford Environmental Dose Reconstruction (HEDR) Project, a series of calculations has been undertaken to evaluate the absolute and relative contribution of different exposure pathways to thyroid doses that may have been received by individuals living in the vicinity of the Hanford Site. These evaluations include some pathways that were included in the Phase I air-pathway dose evaluations (HEDR staff 1991, page xx), as well as other potential exposure pathways being evaluated for possible inclusion in the future HEDR modeling efforts. This calculation (002) examined the possible doses that may have been received by individuals who drank milk from cows that drank from sources of water (stock tanks and farm ponds) exposed to iodine-131 in the atmosphere during 1945.

Ikenberry, T.A.

1992-12-01

228

Collateral geochemical impacts of agricultural nitrogen enrichment from 1963 to 1985: a southern Wisconsin ground water depth profile.  

PubMed

In this study, we used chlorofluorocarbon (CFC) age-dating to investigate the geochemistry of N enrichment within a bedrock aquifer depth profile beneath a south central Wisconsin agricultural landscape. Measurement of N(2)O and excess N(2) allowed us to reconstruct the total NO(3)(-) and total nitrogen (TN) leached to ground water and was essential for tracing the separate influences of soil nitrification and ground water denitrification in the collateral geochemical chronology. We identify four geochemical impacts due to a steady ground water N enrichment trajectory (39 +/- 2.2 micromol L(-1) yr(-1), r(2) = 0.96) over two decades (1963-1985) of rapidly escalating N use. First, as a by-product of soil nitrification, N(2)O entered ground water at a stable (r(2) = 0.99) mole ratio of 0.24 +/- 0.007 mole% (N(2)O-N/NO(3)-N). The gathering of excess N(2)O in ground water is a potential concern relative to greenhouse gas emissions and stratospheric ozone depletion after it discharges to surface water. Second, excess N(2) measurements revealed that NO(3)(-) was a prominent, mobile, labile electron acceptor comparable in importance to O(2.) Denitrification transformed 36 +/- 15 mole% (mol mol(-1) x 100) of the total N within the profile to N(2) gas, delaying exceedance of the NO(3)(-) drinking water standard by approximately 6 yr. Third, soil acids produced from nitrification substantially increased the concentrations of major, dolomitic ions (Ca, Mg, HCO(3)(-)) in ground water relative to pre-enrichment conditions. By 1985, concentrations approximately doubled; by 2006, CFC age-date projections suggest concentrations may have tripled. Finally, the nitrification induced mobilization of Ca may have caused a co-release of P from Ca-rich soil surfaces. Dissolved P increased from an approximate background value of 0.02 mg L(-1) in 1963 to 0.07 mg L(-1) in 1985. The CFC age-date projections suggest the concentration could have reached 0.11 mg L(-1) in ground water recharge by 2006. These results highlight an intersection of the N and P cycles potentially important for managing the quality of ground water discharged to surface water. PMID:18574177

Browne, Bryant A; Kraft, George J; Bowling, Juliane M; Devita, William M; Mechenich, David J

2008-06-23

229

Abrupt changes in soil water content variability for various time scales and at different depths at the catchment scale  

NASA Astrophysics Data System (ADS)

A current challenge in hydrology is to observe, explain and model soil water content (SWC) patterns across multiple space-time scales. A promising technique for the assessment of SWC patterns at the catchment scale is the wireless sensor network. This technique has the potential to continuously monitor three-dimensional SWC fields with high spatial and temporal resolution, i.e. to detect abrupt changes in SWC patterns. The objective of this study was to analyze the dynamics of SWC patterns at the TERENO forest hydrologic observatory Wüstebach (0.27 km2) for different depths (surface and subsurface soil) and various time scales (annual, seasonal scale and wetting and drying periods). We used the SoilNet wireless network system developed at Forschungszentrum Jülich. SWC measurements were taken every 15 minutes in three depths (5, 20, 50 cm) at 150 locations using EC-5 and 5TE sensors (Decagon Devices). This particular analysis is based on hourly aggregated SWC data measured from 1st of August 2009 to 31st of July 2010. Descriptive statistics and geostatistics were used to investigate the data set depending on soil depth and time scale. We analyzed the mean SWC, standard deviation, coefficient of variation and geostatististical parameters (nugget, sill and range) as a function of time and mean SWC. We found that the dynamics of SWC variability depended on depth, mean soil moisture status, time scale and wetting versus drying period. The magnitude and the variability of the mean SWC, standard deviation, coefficient of variation, and the range decreased with depth depending on soil moisture status. As already observed by others, the standard deviation peaked at medium (critical) SWC, which means that during wetting the standard deviation increased for mean SWC below the critical SWC and decreased above the mean SWC (and vice versa for drying). In addition, we observed that the standard deviation was higher during wetting periods than during drying periods in the medium SWC range, leading to hysteresis effects during abrupt changes in soil moisture status. In the low and high SWC range, the relationship between standard deviation and mean SWC was linear. This systematic behaviour was independent of the time scale. The topography and shallow groundwater are important controls especially in very dry situations. Underlying factors that are variable in space and time and interact in a complex, non-linear way have still to be investigated. The results of this study demonstrated that the SoilNet sensor network was able to detect abrupt changes in SWC patterns at the catchment scale.

Rosenbaum, U.; Herbst, M.; Huisman, J. A.; Weuthen, A.; Petersen, T. J.; Western, A. W.; Vereecken, H.; Bogena, H. R.

2010-12-01

230

The oxidation of calcium implanted titanium in water: A depth profiling study  

NASA Astrophysics Data System (ADS)

Ion implantation of calcium has been proposed previously as a route to bioactive titanium surfaces and has been shown to stimulate promising cell and tissue responses. While the precise reasons for this behaviour remain poorly understood, it is clear that the nature of the Ca implanted surface changes rapidly on exposure to body fluids. In order to understand the processes taking place more clearly, the current work examined the simple interaction of Ca implanted Ti with water. The surface chemistry and compositional changes within the sub-surface region of the modified Ti were examined. On immersion in water, the concentration of implanted Ca ions was found to decrease both at the surface and throughout the implanted region. At the same time, the sub-surface oxygen concentration was found to increase dramatically. Although Ca implantation into Ti results in a thicker oxide layer at the surface, it appears that this layer no longer affords the underlying Ti the same protection from further oxidation provided by the native oxide. By examining samples implanted with O, Ti or Ar it was possible to conclude that this was specific to Ca implantation and not a result of the ion implantation process itself.

Armitage, D. A.; Mihoc, R.; Tate, T. J.; McPhail, D. S.; Chater, R.; Hobkirk, J. A.; Shinawi, L.; Jones, F. H.

2007-02-01

231

Water release and rock volume change associated with smectite dehydration in the < 30 km depth seismcity of subduction zones  

NASA Astrophysics Data System (ADS)

Volatiles play important roles in the dynamics of subduction systems from the shallowest levels of the plate interface to the greatest depths of arc melting source region. Near the trench, the release of water during the breakdown of smectite into illite is often proposed to be responsible for the elevated pore pressure associated with low frequency earthquakes. The thermal breakdown of smectite in subduction zones is generally assumed to occur at 100-150°C, as generally observed in sedimentary basins. However, the upper thermal stability of smectite depends on many factors such as the availability and activity of pore water, which might be higher in the context of subduction than in burial diagenesis. Smectite is also observed to crystallize up to 300°C in geothermal environment. Various experiments have shown that the dehydration of smectite is a stepwise process that occurs at T up to 550°C at P > 3 kbar. At each dehydration step, changes of volume can be as high as 30% and a release of free water of about 150 kgH2O/m3 smectite are observed. The consequences of the smectite dehydration might be thus extremely important at shallow to moderate depth subduction zones, if this mineral remains present at T > 100°C. We have constrained the first macroscopic thermodynamic model that reproduces i) the experimentally observed 3 -> 2 -> 1 -> 0 water-layer transitions during dehydration and the associated volume changes as a function of the nature of interlayer cation, water activity, pressure and temperature, and ii) the stability and compatibility relations of smectite with other minerals at high temperature and pressure condition. This model is used to predict the variations of the solid volume of the subducting sediments and the amount of water expelled from the conditions of early diagenesis to metamorphism. Large, fast and abrupt changes are predicted to occur up to 250°C. This result suggests a possible role of smectite dehydration in the production of high and local fluid pressure that might trigger the < 30 km seismicity, before its breakdown into mica and chlorite.

Vidal, O.; Dubacq, B.

2010-12-01

232

The effects of burning and sheep-grazing on water table depth and soil water quality in a upland peat  

Microsoft Academic Search

Rotational burning of heather to improve grazing and grouse breeding is a common management practice for upland catchments in the UK. However, the effects of such practices on hydrology and water quality are not well understood because the timescale of burning rotation is typically between 7 and 20 years thus requiring long-term experiments in order to resolve the effects. Furthermore,

F. Worrall; A. Armstrong; J. K. Adamson

2007-01-01

233

Technical Note: Using wavelet analyses on water depth time series to detect glacial influence in high-mountain hydrosystems  

NASA Astrophysics Data System (ADS)

Worldwide, the rapid shrinking of glaciers in response to ongoing climate change is currently modifying the glacial meltwater contribution to hydrosystems in glacierized catchments. Assessing the contribution of glacier run-off to stream discharge is therefore of critical importance to evaluate potential impact of glacier retreat on water quality and aquatic biota. This task has challenged both glacier hydrologists and ecologists over the last 20 yr due to both structural and functional complexity of the glacier-stream system interface. Here we propose a new methodological approach based on wavelet analyses on water depth time series to determine the glacial influence in glacierized catchments. We performed water depth measurement using water pressure loggers over ten months in 15 stream sites in two glacier-fed catchments in the Ecuadorian Andes (> 4000 m). We determined the global wavelet spectrum of each time series and defined the Wavelet Glacier Signal (WGS) as the ratio between the global wavelet power spectrum value at a 24 h-scale and its corresponding significance value. To test the relevance of the WGS we compared it with the percentage of the glacier cover in the catchments, a metric of glacier influence often used in the literature. We then tested whether one month data could be sufficient to reliably determine the glacial influence. As expected we found that the WGS of glacier-fed streams decreased downstream with the increasing of non-glacial tributaries. We also found that the WGS and the percentage of the glacier cover in the catchment were significantly positively correlated and that one month data was sufficient to identify and compare the glacial influence between two sites, provided that the water level time series were acquired over the same period. Furthermore, we found that our method permits to detect glacial signal in supposedly non-glacial sites, thereby evidencing glacial meltwater infiltrations. While we specifically focused on the tropical Andes in this paper, our approach to determine glacier influence would be applicable to temperate and arctic glacierized catchments. The WGS therefore appears as a powerful and cost effective tool to better understand the hydrological links between glaciers and hydrosystems and assess the consequences of rapid glacier melting.

Cauvy-Fraunié, S.; Condom, T.; Rabatel, A.; Villacis, M.; Jacobsen, D.; Dangles, O.

2013-04-01

234

Observations of onshore sediment transport in water depths of 10-20 m off Long Island, NY  

NASA Astrophysics Data System (ADS)

A high-resolution multibeam echosounder has been used as part of investigations of sediment transport, benthic habitat and coastal infrastructure in a number of estuarine and inner shelf settings. High-resolution multibeam topographic data provides important information on the nature and distribution of sedimentary bed forms while co-registered backscatter at 300 kHz provides insights into sediment type and the presence of smaller bed forms. A number of studies have been conducted on the inner continental shelf off Long Island, New York to characterize surf-clam habitat and the present-day structure of artificial reefs. These studies, which range in depth from to over 20 m, often show the existence of asymmetric sand waves and other features caused by sediment movement (especially scour depressions and backscatter anomalies) which indicate onshore sediment transport. Repeat surveys show that sand waves can migrate onshore as much 15 m over a 6-month period, although migration is likely to be episodic, occurring primarily during storms or other events. This high-resolution bathymetric data shows the sand waves are not uniformly distributed across the sea bed, but are often concentrated on the flanks of elongate topographic depressions. This onshore sediment movement appears to be occurring along the length of Long Island, although there are regional variations in the water depth in which they are observed. This observed transport may represent a portion of the onshore sediment transport thought to exist in this area.

Flood, R. D.

2004-12-01

235

Comparative analysis of doses to aquatic biota in water bodies impacted by radioactive contamination  

Microsoft Academic Search

Comparative analysis of doses to the reference species of freshwater biota was performed for the following water bodies in Russia or former USSR: Chernobyl NPPs cooling pond, Lakes Uruskul and Berdenish located in the Eastern Urals Radioactive Trace, Techa River, Yenisei River. It was concluded that the doses to biota were considerably different in the acute and chronic periods of

A. I. Kryshev; T. G. Sazykina

236

A novel method for patient exit and entrance dose prediction based on water equivalent path length measured with an amorphous silicon electronic portal imaging device.  

PubMed

In vivo dosimetry is one of the quality assurance tools used in radiotherapy to monitor the dose delivered to the patient. Electronic portal imaging device (EPID) images for a set of solid water phantoms of varying thicknesses were acquired and the data fitted onto a quadratic equation, which relates the reduction in photon beam intensity to the attenuation coefficient and material thickness at a reference condition. The quadratic model is used to convert the measured grey scale value into water equivalent path length (EPL) at each pixel for any material imaged by the detector. For any other non-reference conditions, scatter, field size and MU variation effects on the image were corrected by relative measurements using an ionization chamber and an EPID. The 2D EPL is linked to the percentage exit dose table, for different thicknesses and field sizes, thereby converting the plane pixel values at each point into a 2D dose map. The off-axis ratio is corrected using envelope and boundary profiles generated from the treatment planning system (TPS). The method requires field size, monitor unit and source-to-surface distance (SSD) as clinical input parameters to predict the exit dose, which is then used to determine the entrance dose. The measured pixel dose maps were compared with calculated doses from TPS for both entrance and exit depth of phantom. The gamma index at 3% dose difference (DD) and 3 mm distance to agreement (DTA) resulted in an average of 97% passing for the square fields of 5, 10, 15 and 20 cm. The exit dose EPID dose distributions predicted by the algorithm were in better agreement with TPS-calculated doses than phantom entrance dose distributions. PMID:20019398

Kavuma, Awusi; Glegg, Martin; Metwaly, Mohamed; Currie, Garry; Elliott, Alex

2009-12-17

237

A novel method for patient exit and entrance dose prediction based on water equivalent path length measured with an amorphous silicon electronic portal imaging device  

NASA Astrophysics Data System (ADS)

In vivo dosimetry is one of the quality assurance tools used in radiotherapy to monitor the dose delivered to the patient. Electronic portal imaging device (EPID) images for a set of solid water phantoms of varying thicknesses were acquired and the data fitted onto a quadratic equation, which relates the reduction in photon beam intensity to the attenuation coefficient and material thickness at a reference condition. The quadratic model is used to convert the measured grey scale value into water equivalent path length (EPL) at each pixel for any material imaged by the detector. For any other non-reference conditions, scatter, field size and MU variation effects on the image were corrected by relative measurements using an ionization chamber and an EPID. The 2D EPL is linked to the percentage exit dose table, for different thicknesses and field sizes, thereby converting the plane pixel values at each point into a 2D dose map. The off-axis ratio is corrected using envelope and boundary profiles generated from the treatment planning system (TPS). The method requires field size, monitor unit and source-to-surface distance (SSD) as clinical input parameters to predict the exit dose, which is then used to determine the entrance dose. The measured pixel dose maps were compared with calculated doses from TPS for both entrance and exit depth of phantom. The gamma index at 3% dose difference (DD) and 3 mm distance to agreement (DTA) resulted in an average of 97% passing for the square fields of 5, 10, 15 and 20 cm. The exit dose EPID dose distributions predicted by the algorithm were in better agreement with TPS-calculated doses than phantom entrance dose distributions.

Kavuma, Awusi; Glegg, Martin; Metwaly, Mohamed; Currie, Garry; Elliott, Alex

2010-01-01

238

Hydrogeochemical contrast between brown and grey sand aquifers in shallow depth of Bengal Basin: consequences for sustainable drinking water supply.  

PubMed

Delineation of safe aquifer(s) that can be targeted by cheap drilling technology for tubewell (TW) installation becomes highly imperative to ensure access to safe and sustainable drinking water sources for the arsenic (As) affected population in Bengal Basin. This study investigates the potentiality of brown sand aquifers (BSA) as a safe drinking water source by characterizing its hydrogeochemical contrast to grey sand aquifers (GSA) within shallow depth (<70 m) over an area of 100 km(2) in Chakdaha Block of Nadia district, West Bengal, India. The results indicate that despite close similarity in major ion composition, the redox condition is markedly different in groundwater of the two studied aquifers. The redox condition in the BSA is delineated to be Mn oxy-hydroxide reducing, not sufficiently lowered for As mobilization into groundwater. In contrast, the enrichments of NH(4)(+), PO(4)(3-), Fe and As along with lower Eh in groundwater of GSA reflect reductive dissolution of Fe oxy-hydroxide coupled to microbially mediated oxidation of organic matter as the prevailing redox process causing As mobilization into groundwater of this aquifer type. In some portions of GSA the redox status even has reached to the stage of SO(4)(2-) reduction, which to some extent might sequester dissolved As from groundwater by co-precipitation with authigenic pyrite. Despite having low concentration of As in groundwater of the BSA the concentration of Mn often exceeds the drinking water guidelines, which warrants rigorous assessment of attendant health risk for Mn prior to considering mass scale exploitation of the BSA for possible sustainable drinking water supply. PMID:22706147

Biswas, Ashis; Nath, Bibhash; Bhattacharya, Prosun; Halder, Dipti; Kundu, Amit K; Mandal, Ujjal; Mukherjee, Abhijit; Chatterjee, Debashis; Mörth, Carl-Magnus; Jacks, Gunnar

2012-06-16

239

Dependence of Yb-169 absorbed dose energy correction factors on self-attenuation in source material and photon buildup in water  

SciTech Connect

Purpose: Absorbed dose energy correction factors, used to convert the absorbed dose deposited in a LiF thermoluminescent dosimeter (TLD) into the clinically relevant absorbed dose to water, were obtained for both spherical volumetric sources and for the model 4140 HDR Yb-169 source. These correction factors have a strong energy dependence below 200 keV; therefore, spectral changes were quantified as Yb-169 photons traveled through both source material (Yb{sub 2}O{sub 3}) and water with the corresponding absorbed dose energy correction factors, f(r,{theta}), calculated as a function of location in a phantom. Methods: Using the MCNP5 Monte Carlo radiation transport simulation program, the Yb-169 spectrum emerging from spherical Yb{sub 2}O{sub 3} sources (density 6.9 g/cm{sup 3}) with radii between 0.2 and 0.9 mm were analyzed and their behavior compared against those for a point-source. The absorbed dose deposited to both LiF and H{sub 2}O materials was analyzed at phantom depths of 0.1-10 cm for each source radius and the absorbed dose energy correction factor calculated as the ratio of the absorbed dose to water to that of LiF. Absorbed dose energy correction factors for the Model 4140 Yb-169 HDR brachytherapy source similarly were obtained and compared against those calculated for the Model M-19 Ir-192 HDR source. Results: The Yb-169 average spectral energy, emerging from Yb{sub 2}O{sub 3} spherical sources 0.2-0.9 mm in radius, was observed to harden from 7% to 29%; as these photons traveled through the water phantom, the photon average energy softened by as much as 28% at a depth of 10 cm. Spectral softening was dependent on the measurement depth in the phantom. Energy correction factors were found to vary both as a function of source radius and phantom depth by as much as 10% for spherical Yb{sub 2}O{sub 3} sources. The Model 4140 Yb-169 energy correction factors depended on both phantom depth and reference angle and were found to vary by more than 10% between depths of 1 and 10 cm and angles of 0 deg. and 180 deg. This was in contrast to that of the Model M-19 Ir-192 source which exhibited approximately 3.5%-4.4% variation in its energy correction factors from phantom depths of 0.5-10 cm. The absorbed dose energy correction factor for the Ir-192 source, on the other hand, was independent of angle to within 1%. Conclusions: The application of a single energy correction factor for Yb-169 TLD based dosimetry would introduce a high degree of measurement uncertainty that may not be reasonable for the clinical characterization of a brachytherapy source; rather, an absorbed dose energy correction function will need to be developed for these sources. This correction function should be specific to each source model, type of TLD used, and to the experimental setup to obtain accurate and precise dosimetric measurements.

Medich, David C.; Munro, John J. III [Radiation Laboratory, University of Massachusetts Lowell, 1 University Avenue, Lowell, Massachusetts 01854 (United States); Source Production and Equipment Co., Inc., 113 Teal Street, St. Rose, Louisiana 70087 (United States)

2010-05-15

240

Calorimetric determination of the absorbed dose to water for medium-energy x-rays with generating voltages from 70 to 280 kV.  

PubMed

For medium energy x-rays produced with tube voltages from 70 to 280 kV, the absorbed dose to water, D(w), has been determined by means of water calorimetry with relative standard uncertainties ranging from 0.45% to 0.98% at 280 and 70 kV. The results were confirmed by Monte Carlo calculations, in which the ratios of D(w) at 5 cm depth in a reference water phantom to the air kerma free in air, K(a), at the same point in space were compared to the corresponding ratios determined experimentally. The general agreement between measurement and calculation was better than 1%. These results confirm earlier investigations in which the absorbed dose to graphite was determined by means of a graphite extrapolation chamber. For the Monte Carlo calculations, an attempt was made to present a complete uncertainty budget, taking into account type B contributions also. PMID:22975691

Krauss, A; Büermann, L; Kramer, H-M; Selbach, H-J

2012-09-14

241

Calorimetric determination of the absorbed dose to water for medium-energy x-rays with generating voltages from 70 to 280 kV  

NASA Astrophysics Data System (ADS)

For medium energy x-rays produced with tube voltages from 70 to 280 kV, the absorbed dose to water, Dw, has been determined by means of water calorimetry with relative standard uncertainties ranging from 0.45% to 0.98% at 280 and 70 kV. The results were confirmed by Monte Carlo calculations, in which the ratios of Dw at 5 cm depth in a reference water phantom to the air kerma free in air, Ka, at the same point in space were compared to the corresponding ratios determined experimentally. The general agreement between measurement and calculation was better than 1%. These results confirm earlier investigations in which the absorbed dose to graphite was determined by means of a graphite extrapolation chamber. For the Monte Carlo calculations, an attempt was made to present a complete uncertainty budget, taking into account type B contributions also.

Krauss, A.; Büermann, L.; Kramer, H.-M.; Selbach, H.-J.

2012-10-01

242

Modelling effects of seasonal variation in water table depth on net ecosystem CO2 exchange of a tropical peatland  

NASA Astrophysics Data System (ADS)

Seasonal variation in water table depth (WTD) determines the balance between aggradation and degradation of tropical peatlands. Longer dry seasons together with human interventions (e.g. drainage) can cause WTD drawdowns making tropical peatland C storage highly vulnerable. Better predictive capacity for effects of WTD on net CO2 exchange is thus essential to guide conservation of tropical peat deposits. Mathematical modelling of basic eco-hydrological processes under site-specific conditions can provide such predictive capacity. We hereby deploy a mathematical model ecosys to study effects of seasonal variation in WTD on net ecosystem productivity (NEP) of an Indonesian peatland. We simulated lower NEPs (~ -2 g C m-2 d-1) during rainy seasons with shallow WTD, higher NEPs (~ +1 g C m-2 d-1) during early dry seasons with intermediate WTD and again lower NEPs (~ -4 g C mm-2 d-1) during late dry seasons with deep WTD during 2002-2005. These values were corroborated by regressions (P < 0.0001) of hourly modelled vs. eddy covariance (EC) measured net ecosystem CO2 fluxes which yielded R2 > 0.8, intercepts approaching 0 and slopes approaching 1. We also simulated a gradual increase in annual NEPs from 2002 (-609 g C m-2) to 2005 (-373 g C m-2) with decreasing WTD which was corroborated by EC-gap filled annual NEP estimates. These WTD effects on NEP were modelled from basic eco-hydrological processes including microbial and root oxidation-reduction reactions driven by soil and root O2 transport and uptake which in turn drove soil and plant C, N and P transformations within a soil-plant-atmosphere water transfer scheme driven by water potential gradients. This modelling should therefore provide a predictive capacity for WTD management programs to reduce tropical peat degradation.

Mezbahuddin, M.; Grant, R. F.; Hirano, T.

2013-08-01

243

Water Pressure in Depth  

ERIC Educational Resources Information Center

How can a science concept be taught in a way that generates interest, gives students the opportunity to consider other possibilities, does not lock them into one way of doing or seeing things, and gives them some ownership of their learning? These authors searched high and low for the perfect activity to illustrate a key concept for their partner…

Lynch, Mary Jean; Zenchak, John

2011-01-01

244

Comparative analysis of doses to aquatic biota in water bodies impacted by radioactive contamination.  

PubMed

Comparative analysis of doses to the reference species of freshwater biota was performed for the following water bodies in Russia or former USSR: Chernobyl NPPs cooling pond, Lakes Uruskul and Berdenish located in the Eastern Urals Radioactive Trace, Techa River, Yenisei River. It was concluded that the doses to biota were considerably different in the acute and chronic periods of radioactive contamination. The most vulnerable part of all considered aquatic ecosystems was benthic trophic chain. A numerical scale on the "dose rate - effects" relationships for fish was formulated. Threshold dose rates above which radiation effects can be expected in fish were evaluated to be the following: 1 mGy d(-1) for appearance of the first morbidity effects in fish; 5 mGy d(-1) for the first negative effects on reproduction system; 10 mGy d(-1) for the first effects on life shortening of fish. The results of dose assessment to biota were compared with the scale "dose rate - effects" and the literature data on the radiobiological effects observed in the considered water bodies. It was shown that in the most contaminated water bodies the dose rates were high enough to cause the radiobiological effects in fish. PMID:21924530

Kryshev, A I; Sazykina, T G

2011-09-15

245

Changes in soil aggregate stability under different irrigation doses of waste water  

NASA Astrophysics Data System (ADS)

Freshwater availability and soil degradation are two of the most important environmental problems in the Mediterranean area acerbated by incorrect agricultural use of irrigation in which organic matter is not correctly managed, the use of low quality water for irrigation, and the inefficiency of dose irrigation. For these reasons strategies for saving water and for the restoration of the mean properties of soil are necessary. The use of treated waste water for the irrigation of agricultural land could be a good solution to these problems, as it reduces the utilization of fresh water and could potentially improve key soil properties. In this work we have been studying, for more than three years, the effects on soil properties of different doses of irrigation with waste water. Here we show the results on aggregate stability. The study is located in an agricultural area at Biar (Alicante, SE of Spain), with a crop of grape (Vitis labrusca). Three types of waters are being used in the irrigation of the soil: fresh water (control) (TC), and treated waste water from secondary (T2) and tertiary treatment (T3). Three different doses of irrigation have been applied to fit the efficiency of the irrigation to the crop and soil type: D10 (10 L m-2 every week during 17 months), D50 (50 L m-2 every fifteen days during 14 moths) and D30 (30 L m-2 every week during 6 months up to present day). The results showed a clear decrease of aggregate stability during the period we used the second dose (D50) independent of the type of water used. That dose of irrigation and frequency produced strong wetting and drying cycles (WD) in the soil, and this is suspected to be the main factor responsible for the results. When we changed the dose of irrigation to D30, reducing the quantity per event and increasing the frequency, the soil aggregate stability started to improve. This dose avoids strong drying periods between irrigation events and the aggregate stability is confirmed to be slowly increasing. A study in the medium or long-term is necessary to continue to ascertain the impact on soil of the irrigation and to assess the feasibility of using these waters in this type of soil. Aknowledgements: This research was supported by the Water Reuse project (Reference STREP- FP6-2003-INCO-Russia+NIS-1. PL 516731). A. Morugán acknowledge the grants from 'Caja Mediterraneo'. The authors also acknowledge the "Biar waste water treatment station", 'Entidad pública de saneamiento de aguas residuales de la Comunidad Valenciana' and "Proaguas Costablanca" for the collaboration and to Frances Young for improving the English.

Morugán, Alicia; García-Orenes, Fuensanta; Mataix-Solera, Jorge; Arcenegui, Victoria; Bárcenas, Gema

2010-05-01

246

Results from a winter 2009-2010 nearshore mooring test in 25 m water depth off Newport, Oregon  

NASA Astrophysics Data System (ADS)

As part of the NSF-funded Ocean Observatories Initiative (OOI), two surface moorings will be placed in 25 m water depth off Newport, Oregon and Grays Harbor, Washington. These moorings are intended to acquire continuous observations over the inner-shelf, where the surface boundary layer interacts continuously with the ocean bottom boundary layer. The moorings will utilize the WHOI-developed stretch hose technology implemented at several operational moorings along the US east coast. For the purposes of mooring survival, the largest significant waves need to be considered. Analysis of the historical record indicates the 100-year return period storm would generate 14.5 m high waves. The harsh wind and wave conditions encountered over the inner-shelf have the potential to cause mooring failure either by destroying surface buoy components, or by causing subsurface mooring components to fail. For example, during a winter storm in December 2007, several NDBC moorings along the Oregon and Washington coasts broke. To test modeling of mooring performance under winter conditions we constructed a test/pilot mooring with hardware, communications and power similar to the OOI buoy design. The test focused on the survivability of components. The mooring was equipped with a load cell to examine responses under varying wave and mean flow conditions. A secondary objective of the deployment was to test Ship-to-Ship/Ship-to-Shore Wireless Access Protocol (SWAP) telemetry from the buoy to shore over a distance of 1.5 km. Load cell data as well as buoy instruments (conductivity, temperature) were telemetered. This test mooring was deployed near one of the OOI sites in 25 m of water off Newport, Oregon in late October 2009. The mooring parted in mid-March 2010, two weeks prior to planned recovery. We recovered all mooring components, and we will report on the mooring design, the test, and the science and engineering data received.

Dever, E. P.; Waldorf, B. W.; Risien, C. M.

2010-12-01

247

Stability of gravity-capillary waves generated by a moving pressure disturbance in water of finite depth  

NASA Astrophysics Data System (ADS)

In previous work, we investigated two-dimensional steady gravity-capillary waves generated by a localized pressure distribution moving with a constant speed U in water of finite depth h. Localized solitary waves can only exist in subcritical flows where the Froude number F=U/(gh)1/2<1, and were found using a combination of numerical simulations of the fully nonlinear inviscid, irrotational equations, and analytically from a weakly nonlinear long-wave model, the steady forced Korteweg-de Vries equation. The solution branches depended on three parameters, the Froude number, F<1, the Bond number, ?>1/3, and the magnitude and sign of the pressure distribution, ?. In this paper, we examine the two-dimensional stability of these waves using numerical simulations of the fully nonlinear unsteady equations. The results are favorably compared to analogous numerical solutions of the unsteady forced Korteweg-de Vries equation. We find that for ?>0, the small-amplitude steady depression wave is stable whereas the large-amplitude steady depression wave is unstable. The depression wave with a dimple at its crest, which occurs only when ?<0 is unstable, but the small-amplitude elevation wave with ?<0 is stable.

Grimshaw, Roger; Maleewong, Montri; Asavanant, Jack

2009-08-01

248

Stability of steady gravity waves generated by a moving localised pressure disturbance in water of finite depth  

NASA Astrophysics Data System (ADS)

We study the stability of the steady waves forced by a moving localised pressure disturbance in water of finite depth. The steady waves take the form of a downstream wavetrain for subcritical flow, but for supercritical flow there is a solution branch for each specified forcing term, which has two localised solitary-like solutions for each Froude number, a small-amplitude and a large-amplitude solution. Our main purpose is to numerically investigate the stability of these steady waves by simulating the unsteady development from appropriate initial conditions. We use a forced Korteweg-de Vries model valid in the transcritical regime for weak forcing, and a fully nonlinear boundary integral simulation. The simulations using the forced Korteweg-de Vries model are in good agreement with the fully nonlinear simulations when the Froude number is near unity for small pressure forcing, as expected. We find that the steady subcritical downstream wavetrain is stable. For supercritical flow, the small-amplitude solitary-like wave which has bifurcated from a uniform flow is stable, whereas the large-amplitude solitary-like wave which has bifurcated from a free solitary wave is unstable. Furthermore, here a difference between the forced Korteweg-de Vries model and the fully nonlinear simulations is revealed. For moderate and large pressure forcing, the forced Korteweg-de Vries model predicts a stable solitary wave moving away from the pressure forcing, while the nonlinear simulation shows that this wave evolves to a breaking wave.

Grimshaw, Roger; Maleewong, Montri

2013-07-01

249

Hydrophytes extraction in Taihu Lake, China: an approach of integrating decision tree with water depth based on Landsat TM and SPOT  

NASA Astrophysics Data System (ADS)

When multispectral images are used to extract the area of aquatic vegetation in Taihu Lake, because of the influence of suspended matter and algae, different objects may have the same spectrum and make it difficult to mapping the distribution of aquatic vegetation exactly. Many different methods, including unsupervised classification and supervised classification, are used, but the classification accuracy didn't improve obviously. The growth of aquatic vegetation is closely to the water depth. So we try to use water depth data to increase the extraction accuracy. The whole Taihu Lake is classified into three types: open water, emerged vegetation and submersed aquatic vegetation. Suppose the DN (Digital number) of each type satisfies normal distribution. Numbers of sample points of each type in single band or combined bands are selected and put down there DNs, and then statistical method is adopted to acquire the maximum and minimum which are used to build decision tree to fulfill the classification. The single band or combined bands in which maximum and minimum interval of each type have small intersect set are considered as the suitable bands for classification. Two methods, classification based on spectral characteristics and classification based on spectral characteristics and water depth data, are used. The classification accuracies of the two methods are compared. The results show the water depth data can improve the classification accuracy and resolve the different objects with same spectrum problem partially.

Zhang, Shouxuan; Ma, Ronghua; Zhao, Shuhe; Wang, Chunhong; Tang, Wei

2007-08-01

250

Depth-resolved water column spectral absorption of sunlight by phytoplankon during the Southern Ocean Gas Exchange (SOGasEx) Lagrangian tracer experiments  

NASA Astrophysics Data System (ADS)

Optical measurements made during gas exchange tracer experiments in the Southern Ocean, Atlantic sector near 51°S, 38°W from March-April 2008 (SOGasEx) were used to develop daily integrated depth- resolved PAR absorbed by phytoplankton. Particulate and phytoplankton pigment spectral absorption coefficients (ap and aph), and methanol-extracted chlorophyll-a concentrations (chl-a) from discrete samples within and below the upper mixed layer (40 stations) were combined with data from optical casts where chlorophyll-a and cdom fluorescence and PAR scalar irradiance were measured (11 stations), PAR Kd was measured from a buoy free of ship shadow for 0-5m (11 stations), and Wetlabs AC-9 whole water absorption coefficients to 150m were measured (14 stations, with 3 in common with fluorescence data) to estimate depth-resolved values for both total spectral absorption and spectral PAR irradiance. By combining depth-adjusted spectral absorption of phytoplankton pigments (aph) with depth-adjusted PAR spectral irradiance we estimated depth-resolved daily PAR irradiance absorbed by photosynthetic pigments. These data can be compared with time-integrated primary production measurements conducted on deck where solar exposure or lamp exposure was modified to simulate a range of depths. Such a synthesis should improve our estimates of depth-integrated daily primary production, and ultimately contribute to refining estimates of carbon export rates to be incorporated into a carbon budget and CO2 air-sea flux models for the SOGasEx experiments.

Hargreaves, B. R.

2008-12-01

251

Temporal variation in depth to water table and hydrochemistry in three raised bogs and their laggs in coastal British Columbia, Canada  

NASA Astrophysics Data System (ADS)

The laggs of three raised bogs in coastal British Columbia were studied in 2010-2012 to determine the temporal variation in depth to water table and hydrochemistry. The lagg is an integral, but rarely studied, part of a raised bog that helps to maintain the water mound in the bog and provides a buffer for runoff from adjacent mineral areas. Depth to water table measurements in 25 piezometers displayed similar annual fluctuations, with the highest water table in winter and the lowest at the end of summer. The smallest fluctuations in depth to water table were recorded closest to the bog centre, and the largest fluctuations in the laggs and adjacent mineral soil sites. Removal of a mature forest stand on one of the study transects resulted in a "watering-up" of the lagg site; the mean water level between August and November increased by 8 cm from 2010 to 2011, and by up to 27 cm during the driest time of the year. pH, pH-corrected electrical conductivity, and Na+ and Mg2+ concentrations varied little during the study period, whereas Ca2+, K+, Cl-, and DOC concentrations and acidity were more variable.

Howie, S. A.; van Meerveld, H. J.

2012-12-01

252

Quantifying the source regions of observed pore water B and ?^{11}B signatures at shallow depths in forearcs  

NASA Astrophysics Data System (ADS)

At many subduction zones, geochemistry of pore waters taken from boreholes and mud volcanoes indicates a contribution from deep, high-temperature sources. These observations include pore water freshening, elevated K, thermogenic hydrocarbons, enrichment in volatiles such as B and Li, and decreased ?11B, ?6Li, and ?37Cl. As tracers of subduction zone devolatilization, geochemical signatures provide constraints on fluid flow pathways and rates within the forearc; in addition, the return flux of volatiles to the oceans through forearcs may constitute a significant component of the global cycles for B and Li. Identifying the location and distribution of source regions for these tracers is one critical step toward characterizing subduction zone fluid transport systems. To date, this problem is relatively well studied for pore water freshening signals and thermogenic hydrocarbons. In contrast, there has been little work to rigorously constrain the locations of source regions for other tracers, or to quantify the expected source concentrations. Here, we focus on numerous observations of high [B] and low ?11B in fluids sampled at shallow depths, which have been interpreted to reflect desorption of isotopically light B from clays with increased temperature, and subsequent advection of the altered fluids to the seafloor either near the trench or on the continental slope. At the Costa Rican, Nankai, and N. Japan margins, observed values of [B] range from ~2000 to 4000 ?M (typical seawater concentration is ~42 ?M), and ?11B values are as low as ~25 ‰ (average seawater value is ~39.5 ‰). We use a simple model to combine (1) heating and compaction that accompany progressive burial of sediment with (2) previously published laboratory experimental data that constrain the distribution coefficient (Kd) for B in marine sediments as a function of temperature, to quantify the expected distribution of B concentrations and isotopic ratios within bulk mudstones in subduction zones. We track packages of sediment as they are heated and compacted, and calculate resulting [B] and ?11B step-wise from conservation of mass and applying a temperature-dependent Kd. The resulting distribution of [B] and ?11B depend primarily upon the rates of heating and porosity loss with burial. In our preliminary analysis, we consider a generic subduction zone with a total taper angle of 8°, and evaluate two end- member cases: cold and warm scenarios, in which heat flow on the incoming plate is set at 60 mW m-2, and 120 mW m-2, respectively. For the cold end-member scenario, simulated values of [B] within the subducted sedment at 30 km from the trench range from 650 to 1200 ?M and values of ?11B range from 23.4 to 30.6 ‰. At 60 km from the trench, [B] ranges from 1010 to 3340 ?M and ?11B from 18.0 to 25.0 ‰. For the warm scenario, simulated [B] ranges from 970 to 2400 ?M at 30 km and 2250 to 11480 ?M at 60 km; ?11B ranges from 19.2 to 25.2 ‰ at 30 km and 15.9 to 19.5 ‰ at 60 km. These signatures are generally stronger than those observed in pore fluids at shallow depths, consistent with the probable re-adsorption of some B during updip or vertical advection. Ultimately, the results of these calculations can be used as input for hydrologic models that include re-adsorption, to quantitatively investigate the fluid flow rates and permeabilities required to transport B at rates required to produce the observed signatures.

Saffer, D. M.; Kopf, A. J.

2006-12-01

253

Depth dependence of electron backscatter: An energy spectral and dosimetry study using Monte Carlo simulation  

SciTech Connect

This study investigated the depth dependence of electron backscatter from a layer of lead (Pb) for clinical electron beams. The change in the electron backscatter with variation in the water depth above the Pb was determined. Electron energy spectra and relative depth doses as a function of depth in water over the Pb layer were calculated using a Monte Carlo simulation and studied. Phase-space files for 4 and 9 MeV electron beams (10x10 cm{sup 2} applicator and cutout) based on the Varian 21 EX linear accelerator were generated using the EGSnrc-based BEAMNRC code. 3 mm of Pb, at depths of 0.5 and 1 cm in water, was irradiated with electrons. The source-to-surface distance is equal to 100 cm. Electron energy spectra and relative depth doses with and without the presence of the Pb layer at different depths in water were determined using the BEAMNRC code. For the 4 MeV electron energy spectra at a depth of 0.5 cm in water, electron backscatter was found to originate at the Pb-water interface and extend to 0.5 cm above the Pb insert. However, at a depth of 1 cm in water, electron backscatter almost disappeared at 0.5 and 1 cm above th ePb insert. This is due to the increased attenuation of the incident 4 MeV electron beam in a thicker layer of water as well as increased attenuation of the electron backscatter above the Pb. This resulted in a 23% decrease in relative dose at a measurement point of 0.5 cm depth, when the depth of the Pb insert was changed from 1 to 0.5 cm. For the electron energy spectra of the 9 MeV beams with a 0.5 cm depth of water, only a small amount of electron backscatter was observed. However, more electron backscatter was found when the water depth was increased to 1 cm. This is because the electron beam energy was decreased more due to the increase in attenuation from the increased depth of water compared to 0.5 cm. Since the electron energy spectrum and relative depth dose above the Pb layer vary with depth of water on top of the Pb, the electron backscatter depends significantly on the thickness of water, or water equivalent bolus, or critical tissue over the Pb shield in electron radiotherapy.

Chow, James C. L.; Owrangi, Amir M. [Department of Radiation Physics, Princess Margaret Hospital and Department of Radiation Oncology, University of Toronto, Toronto, Ontario M5G 2M9 (Canada); Department of Physics, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada) and Department of Physics, Ryerson University, Toronto, Ontario M5B 2K3 (Canada); Department of Radiation Physics, Princess Margaret Hospital, Toronto, Ontario M5G 2M9 (Canada)

2009-02-15

254

Low doses of dexamethasone decrease brain water content of collagenase-induced cerebral hematoma  

PubMed Central

Different doses of dexamethasone were evaluated for the treatment of cerebral trauma using a rat model of cerebral hematoma induced by intracerebral (IC) stereotaxic injections of collagenase. Control animals received an intracerebral collagenase injection followed by intraperitoneal (IP) saline injection. Sham operated animals received saline only (IC, IP). Forty-eight hours following the surgeries, the brains were removed from the euthanized animals. Cerebral hemispheres were separated and the 4 coronal sections (antero-posterior plane) were weighed. Each slice was dried for 24 h (100°C) and weighed again to establish brain water content. In hematoma-induced saline treated rats, significant differences in brain water content were observed when compared to sham operated animals. Rats treated with 1 mg/kg dexamethasone had a significant brain water content decrease; however, no significant differences were observed with higher doses of dexamethasone. In conclusion, low doses of dexamethasone seem to be beneficial for the treatment of cerebral trauma.

Vachon, Pascal; Moreau, Jean-Pierre

2003-01-01

255

Three-dimensional Green's function for harmonic water waves over a bottom topography with different depths at infinity  

NASA Astrophysics Data System (ADS)

The three-dimensional Green's function of water waves in variable-bathymetry regions, associated with the problem of propagation of water waves emitted from a monochromatic point source, is derived and studied. The solution is of interest in its own right but also provides useful information for the formulation and treatment of complex wave body seabed interaction problems in variable-bathymetry regions, especially as regards the hydrodynamic characteristics of large structures installed in the nearshore and coastal environment. Assuming a parallel-contour bathymetry, with a continuous depth function of the form h(x,y) {=} h(x), attaining constant, but possibly different, values at the semi-infinite regions x {<} a and x {>} b, the problem is reduced to a two-dimensional one, by using Fourier transform. The transformed problem is treated by applying domain decomposition and reformulating it as a transmission problem in the finite domain containing the bottom irregularity. An appropriate decomposition of the wave potential is introduced, permitting the singular part to be solved analytically, and the problem for the regular part to be reformulated as a variational problem. An enhanced local-mode series representation is used for the regular wave potential in the variable-bathymetry region, including the propagating mode, the sloping-bottom mode (see Athanassoulis & Belibassakis 1999), and a number of evanescent modes. Using this representation, in conjunction with the variational principle, a forced system of horizontal coupled-mode equations is derived for the determination of the complex modal-amplitude functions of the regular wave potential. This system is numerically solved by using a second-order central finite-difference scheme. The source-generated water-wave potential is, finally, obtained by an efficient numerical Fourier inversion based on FFT. Numerical results are presented and discussed for various bottom topographies, including smooth but steep underwater trenches and ridges, putting emphasis on the identification of the important features of the near- and far-field patterns on the horizontal plane and on the vertical plane containing the point source. Characteristic patterns of trapped (well-localized) wave propagation over ridges are predicted and discussed.

Belibassakis, K. A.; Athanassoulis, G. A.

2004-07-01

256

Seasonal patterns in depth of water uptake under contrasting annual and perennial systems in the Corn Belt Region of the Midwestern U.S  

Microsoft Academic Search

In agricultural landscapes, variation and ecological plasticity in depth of water uptake by annual and perennial plants is\\u000a an important means by which vegetation controls hydrological balance. However, little is known about how annual and perennial\\u000a plants growing in agriculturally dominated landscapes in temperate humid regions vary in their water uptake dynamics. The\\u000a primary objective of this study was to

H. Asbjornsen; G. Shepherd; M. Helmers; G. Mora

2008-01-01

257

Rating curves and estimation of average water depth at the upper Negro River based on satellite altimeter data and modeled discharges  

NASA Astrophysics Data System (ADS)

The objective of this study is to derive the stage discharge relationship for 21 “virtual gauge stations” located at the upper Negro River (Amazon Basin, Brazil). A virtual station can be defined as any crossing of water body surface (i.e., large rivers) by radar altimeter satellite tracks. Rating curve parameters are estimated by fitting with a power law the temporal series of water surface altitude derived from satellite measurements and the discharge. Discharges are calculated using ProGUM, a flow routing model based on the Muskingum Cunge (M C) approach considering a diffusion-cum-dynamic wave propagation [Leon, J.G., Bonnet, M.P., Cauhope, M., Calmant, S., Seyler, F., submitted for publication. Distributed water flow estimates of the upper Negro River using a Muskingum Cunge routing model based on altimetric spatial data. J. Hydrol.]. Among these parameters is the height of effective zero flow. Measured from the WGS84 ellipsoid used as reference, it is shown that the height of effective zero flow is a good proxy of the mean water depth from which bottom slope of the reaches can be computed and Manning roughness coefficients can be evaluated. Mean absolute difference lower than 1.1 m between estimated equivalent water depth and measured water depth indicates the good reliability of the method employed. We computed the free surface water slope from ENVISAT altimetry data for dry and rainy seasons. These profiles are in good agreement with the bottom profile derived from the aforementioned water depths. Also, the corresponding Manning coefficients are consistent with the admitted ranges for natural channels with important flows (superficial width >30.5 m [Chow, V.T., 1959. Open Channel Hydraulics. McGraw-Hill, New York]) and irregular section.

Leon, J. G.; Calmant, S.; Seyler, F.; Bonnet, M.-P.; Cauhopé, M.; Frappart, F.; Filizola, N.; Fraizy, P.

2006-09-01

258

Palaeo-water depth estimation for a 600-year record from Nam Co (Tibet) using an ostracod-based transfer function  

Microsoft Academic Search

A modern training set of ostracods from the large slightly saline lake Nam Co on the southeastern Tibetan Plateau is presented. In total 44 samples covering the largest part of the lake and water depth from 2 to 93m were taken. There are eight ostracod species in surface sediments of Nam Co: Leucocytherella sinensis, ?Leucocythere dorsotuberosa, Fabaeformiscandona gyirongensis, Candona xizangensis,

Peter Frenzel; Claudia Wrozyna; Manping Xie; Liping Zhu; Antje Schwalb

2010-01-01

259

Direct determination of the absorbed dose to water from 125I low dose-rate brachytherapy seeds using the new absorbed dose primary standard developed at ENEA-INMRI  

NASA Astrophysics Data System (ADS)

Low-intensity radioactive sources emitting low-energy photons are used in the clinic for low dose-rate brachytherapy treatments of tumours. The dosimetry of these sources is based on reference air kerma rate measurements. The absorbed dose rate to water at the reference depth d0 = 1 cm, \\dot {D}_{w,1\\,cm} , is then obtained by a conversion procedure with a large relative standard uncertainty of about 5%. This paper describes a primary standard developed at ENEA-INMRI to directly measure \\dot {D}_{w,1\\,cm} due to LDR sources. The standard is based on a large-angle and variable-volume ionization chamber, embedded in a graphite phantom and operating under ‘wall-less air chamber’ conditions. A set of correction and conversion factors, based on experiments and Monte Carlo simulations, are determined to obtain the value of Dw,1 cm from measurements of increment of ionization current with increasing chamber volume. The relative standard uncertainty on \\dot {D}_{w,1\\,cm} is 2.6%, which is appreciably lower than the current uncertainty. Characteristics of the standard, its associated uncertainty budget, and some experimental results are given for 125I BEBIG I25.S16.C brachytherapy seeds. Finally, results of the experimental determination of the dose-rate constant ?1 cm, traceable to the Dw,1 cm and the low-energy air kerma ENEA-INMRI standards, are given. The relative standard uncertainty on ?1 cm is 2.9%, appreciably lower than the typical uncertainty (4.8%) of the values available in the literature.

Toni, M. P.; Pimpinella, M.; Pinto, M.; Quini, M.; Cappadozzi, G.; Silvestri, C.; Bottauscio, O.

2012-10-01

260

Thermal Responses for Men With Different Fat Compositions During Immersion in Cold Water at Two Depths: Prediction versus Observation.  

National Technical Information Service (NTIS)

A cold thermoregulatory model (CTM) was applied to data from partially immersed subjects divided into normal (NF) or low fat (LF) groups in order to validate CTM during immersion at two depths and to examine mechanisms underlying the individual difference...

J. W. Castellani M. Kolka W. Santee X. Xu

2007-01-01

261

Development of a water calorimetry-based standard for absorbed dose to water in HDR {sup 192}Ir brachytherapy  

SciTech Connect

Purpose: The aim of this article is to develop and evaluate a primary standard for HDR {sup 192}Ir brachytherapy based on 4 deg. C stagnant water calorimetry. Methods: The absolute absorbed dose to water was directly measured for several different Nucletron microSelectron {sup 192}Ir sources of air kerma strength ranging between 21 000 and 38 000 U and for source-to-detector separations ranging between 25 and 70 mm. The COMSOL MULTIPHYSICS software was used to accurately calculate the heat transport in a detailed model geometry. Through a coupling of the ''conduction and convection'' module with the ''Navier-Stokes incompressible fluid'' module in the software, both the conductive and convective effects were modeled. Results: A detailed uncertainty analysis resulted in an overall uncertainty in the absorbed dose of 1.90%(1{sigma}). However, this includes a 1.5% uncertainty associated with a nonlinear predrift correction which can be substantially reduced if sufficient time is provided for the system to come to a new equilibrium in between successive calorimetric runs, an opportunity not available to the authors in their clinical setting due to time constraints on the machine. An average normalized dose rate of 361{+-}7 {mu}Gy/(h U) at a source-to-detector separation of 55 mm was measured for the microSelectron {sup 192}Ir source based on water calorimetry. The measured absorbed dose per air kerma strength agreed to better than 0.8%(1{sigma}) with independent ionization chamber and EBT-1 Gafchromic film reference dosimetry as well as with the currently accepted AAPM TG-43 protocol measurements. Conclusions: This work paves the way toward a primary absorbed dose to water standard in {sup 192}Ir brachytherapy.

Sarfehnia, Arman; Seuntjens, Jan [Medical Physics Unit, McGill University, Montreal General Hospital, Montreal, Quebec H3G 1A4 (Canada)

2010-04-15

262

Calculation of absorbed doses to water pools in severe accident sequences  

SciTech Connect

A methodology is presented for calculating the radiation dose to a water pool from the decay of uniformly distributed nuclides in that pool. Motivated by the need to accurately model radiolysis reactions of iodine, direct application is made to fission product sources dissolved or suspended in containment sumps or pools during a severe nuclear reactor accident. Two methods of calculating gamma absorption are discussed - one based on point-kernal integration and the other based on Monte Carlo techniques. Using least-squares minimization, the computed results are used to obtain a correlation that relates absorbed dose to source energy and surface-to-volume ratio of the pool. This correlation is applied to most relevant fission product nuclides and used to actually calculate transient sump dose rate in a pressurized-water reactor (PWR) severe accident sequence.

Weber, C.F. [Oak Ridge National Lab., TN (United States)

1991-12-01

263

Dose-rate to water calibrations for brachytherapy sources from the end-user perspective  

NASA Astrophysics Data System (ADS)

Independent primary standards for brachytherapy photon-emitting source calibration in terms of dose-rate to water have been developed within the framework of the Euramet T2.J06 project. The introduction of dose-rate to water calibration presents an important change in clinical brachytherapy dosimetry that is expected to result to improved dosimetric accuracy. Nevertheless, as with any change in dosimetry for radiation therapy purposes, a phase-in period of well concerted actions aimed at precluding ambiguities and accidents at the end-user level is necessary. The overall uncertainty budget of clinical brachytherapy applications, as well as current trends in brachytherapy treatment planning system dose-calculation algorithms, also need to be considered for a realistic assessment of the net benefit of improving source calibration accuracy.

Siebert, Frank-André; Venselaar, Jack L. M.; Paulsen Hellebust, Taran; Papagiannis, Panagiotis; Rijnders, Alex; Rivard, Mark J.

2012-10-01

264

DETERMINATION OF MINIMAL INFECTIOUS DOSE OF AN ENTEROVIRUS IN DRINKING WATER  

EPA Science Inventory

The goals of this project were to determine the minimal infectious dose and medical significance of an enteric virus ingested in drinking water. The study was conducted under double-blind, placebo-controlled, random-selection conditions. A total of 149 susceptible (antibody-free)...

265

Clinical beta radiation dosimetry for brachytherapy in terms of absorbed dose to water  

Microsoft Academic Search

Purpose: Beta radiation has found increasing interest in intravascular brachytherapy for successfully overcoming the severe problem of restenosis after interventional treatment of arterial stenosis. Prior to initiating procedures applying beta radiation there is a common need to specify methods for the determination and specification of the absorbed dose to water or tissue and their spatial distributions. The DIN-NAR standardization in

Ulrich Quast; Jürgen Böhm; Theodor W. Kaulich

2002-01-01

266

Tracing the Influence of Mediterranean Outflow Waters on the Mid-depth Portuguese Margin Between Marine Isotope Stages 9 and 13  

NASA Astrophysics Data System (ADS)

Calypso piston core MD03-2699 was retrieved from the Estremadura promontory north of Lisbon from a water depth of 1895 m. Nowadays, this site is bathed by Northeast Atlantic Deep Water (NEADW), whose physical properties are modified by diffusive mixing with the overlying Mediterranean Outflow Water (MOW; 700-1400 m). During the last glacial maximum the MOW became denser and settled deeper in the water column and its lower core's flow strength increased on millennial time scales during the Greenland stadials of the last 50 ka. In order to reconstruct deep-water variations on the mid-depth Portuguese margin during the mid-Brunhes we generated benthic stable isotope and trace element records and measured the mean grain size <63µm for the interval from 300 to 510 ka. Because of the strong MOW derived salinity overprint on the benthic Mg/ Ca data we currently use the western Mediterranean equation (Cacho et al., 2006) to calculate bottom water temperatures (BWT). During the MIS 10 glacial inception, BWT and grain size records reveal millennial-scale oscillation in deep-water conditions with warmer MOW waters (8-10°C) bathing the site during stadials and NEADW (5-7°C) during interstadials. The lower MOW core was the dominant water mass throughout glacial MIS 10 and 12 and NEADW during interglacial MIS 9.5 and 11.31. During MIS 13.1, on the other hand, strong MOW influence on the BWT is observed nearly throughout with NEADW-level BWT occurring only between 493 and 497 ka. During termination IV the MOW/ NEADW boundary shifted upwards right at the onset of the termination, but during termination V the lower MOW core settled further up in the water column only after 408 ka. The Cd/ Ca data indicates that the glacial and stadial MOW was enriched in nutrients either by exporting nutrients from the Mediterranean Sea or by mixing with southern source waters. Overall, our records reveal that deep-water dynamics on the mid-depth Portuguese margin were very variable during the mid-Brunhes, experienced millennial-scale oscillations similar to the last glacial cycle and are driven by the density and thus settling depth of the MOW.

Voelker, A. H.; Martin, P.; Lea, D. W.; Lebreiro, S.

2008-12-01

267

Determination of the contribution of livestock water ingestion to dose from the cow-milk pathway  

SciTech Connect

As part of the Hanford Environmental Dose Reconstruction (HEDR) Project, a series of calculations has been undertaken to evaluate the absolute and relative contribution of different exposure pathways to thyroid doses that may have been received by individuals living in the vicinity of the Hanford Site. These evaluations include some pathways that were included in the Phase I air-pathway dose evaluations (HEDR staff 1991, page xx), as well as other potential exposure pathways being evaluated for possible inclusion in the future HEDR modeling efforts. This calculation (002) examined the possible doses that may have been received by individuals who drank milk from cows that drank from sources of water (stock tanks and farm ponds) exposed to iodine-131 in the atmosphere during 1945.

Ikenberry, T.A.

1992-12-01

268

Natural radionuclides measurements and total dose indicative evaluation in drinking waters of an Italian central region.  

PubMed

A study of radioactivity content in drinking waters collected in some areas of geological interest in an Italian central region was performed to check the compliance with recent European regulations. Gross alpha and beta activities, 226Ra, 238U, 234U, 210Po and 3H concentrations were measured. Gross alpha and beta, 226Ra and 3H activities were determined using an ultra-low-level scintillation counter, 238U, 234U and 210Po by alpha spectrometry after radiochemical separation. Recommended WHO guideline activity concentrations for drinking water were exceeded in 6 cases for gross alpha activity and were not exceeded in any case for gross beta activity. Tritium concentration was always lower than MDA (6.75 Bq L(-1)); the concentrations (mBq L(-1)) of 226Ra, 238U, 234U and 210Po ranged from <1.80 to 23.00, from 1.20 to 140.00, from 1.60 to 120.00 and from 0.25 to 5.90, respectively. Due to the importance of the water in human diet, the doses were calculated for children and adults using the dose coefficient factors reported by EC Directive 96/29 EURATOM and annual water intake; all samples furnished a dose lower the reference level for drinking water (0.1 mSv y(-1)). PMID:17849305

Borio, Rita; Rongoni, Alba; Saetta, Daniela; Desideri, Donatella; Meli, Maria Assunta; Feduzi, Laura

2007-09-01

269

Using polarimetric remote sensing measurements to estimate ice particle size, optical depth and ice water path during CRYSTAL-FACE  

NASA Astrophysics Data System (ADS)

In situ observations made during the CRYSTAL-FACE field experiment have indicated that ice crystals have smaller sizes and are more reflective than is commonly assumed in most current climate models. The size of the particles appears to be principally determined by temperature with the smallest particles being found at the coldest temperatures. Previous analyses of polarimetric measurements in non-absorbing bands have suggested that either bubble inclusions (inhomogeneous hexagonal mono-crystals) or distortions of the hexagonal crystal shape (distorted chain aggregates) are responsible for the observed general absence of haloes, smooth angular variation of reflectance and brightness of ice clouds. In this paper we use multi-angle measurements made by the Research Scanning Polarimeter (RSP) to examine the polarized and unpolarized reflectance of cirrus clouds in bands where ice is non-absorbing (670 and 865 nm) and absorbing (1590, 1880 and 2250 nm). During CRSYTAL-FACE the RSP scan was biased so that the view angle range was from 0 to 75 degrees to the rear of the Proteus aircraft and from 0 to 45 degrees to the front and was oriented to scan along the groundtrack of the aircraft. This allowed observations of a single target over a wide scattering angle range particularly when consecutive flight legs could be combined which allows for basic discrimination of crystal habit using the non-absorbing bands, similar to previous studies (at least in the gross sense of being able to separate columns from plates from distorted crystals from spheroidal shapes). However, compared with non-absorbing bands, the reflectance in absorbing bands is different depending on whether ice particles are geometrically distorted or contain air bubble inclusions because the path length of light inside an ice crystal is quite short which limits scattering off the bubble inclusions. Consequently the retrieved particle size is also sensitive to whether ice crystals are modeled as being distorted or containing air bubbles. We examine how the RSP size retrievals, with an appropriate vertical weighting determined by Green's function calculations, compare with in situ measurements and examine the angular and spectral polarized and unpolarized residuals from the retrievals. This allows us to identify the most appropriate crystal habit for use in the remote sensing of cirrus clouds formed by convection over land, such as those observed during CRYSTAL-FACE, and provide best estimates for the particle size, optical depth and ice water path determined using solar reflectance measurements.

Geogdzhayev, I.; Cairns, B.; Mishchenko, M. I.; Travis, L. D.

2006-12-01

270

LNE-LNHB air-kerma and absorbed dose to water primary standards for low dose-rate 125I brachytherapy sources  

NASA Astrophysics Data System (ADS)

The devices and methods applied for the LNE-LNHB primary standards in terms of reference air-kerma and absorbed dose to water for low dose-rate brachytherapy sources are described. Both standards are based on ionometric measurements, using a circular-shaped free-in-air ionization chamber, and Monte Carlo calculated conversion factors. Results for an IBt Bebig 125I source are presented and used here to assess the dose-rate constant. Uncertainties of 1.5% and 1.6% (with k = 1) were found for the air-kerma rate and the absorbed dose to water rate estimated with the new primary standards. Good agreement was found between our values and the AAPM published dose-rate constants. Comparisons with other primary standards are in progress.

Aubineau-Lanièce, I.; Chauvenet, B.; Cutarella, D.; Gouriou, J.; Plagnard, J.; Aviles Lucas, P.

2012-10-01

271

Realisation of the absorbed dose to water for I-125 interstitial brachytherapy sources.  

PubMed

A large air-filled parallel-plate extrapolation chamber in a phantom of water-equivalent material is used as a primary standard measuring device for low-energy interstitial brachytherapy sources from which the unit of absorbed dose to water can be derived. The chamber is suitable for low-energy photons with energies up to 50 keV. The method to determine the absorbed dose to water was newly developed based on radiation transport theory. It offers a clear analytical expression to determine D(w). A conversion factor C(x(i),x(i)(+1)) has to be applied to the difference of ionization charges measured at two plate separations x(i) and x(i)(+1). The details of the method are presented. The determination of D(w) of an I-125 seed is demonstrated by the measurement of a 'BEBIG Symmetra I25.S16' - seed. Additional measurements of the reference air kerma rate with the PTB primary standard chamber GROVEX I allow to determine experimentally the dose rate constant of an I-125 seed by means of primary standards for the first time. Good agreement was found between the obtained dose rate constant and the published data. PMID:21924788

Schneider, Thorsten; Selbach, Hans-Joachim

2011-09-15

272

Vacuum ultraviolet photodissociation and surface morphology change of water ice films dosed with hydrogen chloride  

SciTech Connect

Time-of-flight (TOF) spectra of photofragment H atoms from the photodissociation of water ice films at 193 nm were measured for amorphous and polycrystalline water ice films with and without dosing of hydrogen chloride at 100-145 K. The TOF spectrum is sensitive to the surface morphology of the water ice film because the origin of the H atom is the photodissociation of dimerlike water molecules attached to the ice film surfaces. Adsorption of HCl on a polycrystalline ice film was found to induce formation of disorder regions on the ice film surface at 100-140 K, while the microstructure of the ice surface stayed of polycrystalline at 145 K with adsorption of HCl. The TOF spectra of photofragment Cl atoms from the 157 nm photodissociation of neutral HCl adsorbed on water ice films at 100-140 K were measured. These results suggest partial dissolution of HCl on the ice film surface at 100-140 K.

Yabushita, Akihiro; Kanda, Daichi; Kawanaka, Noboru; Kawasaki, Masahiro [Department of Molecular Engineering, Kyoto University, Kyoto 615-8510 (Japan)

2007-10-21

273

High altitude diving depths.  

PubMed

In order to make any sea level dive table usable during high altitude diving, a new conversion factor is created. We introduce the standardized equivalent sea depth (SESD), which allows conversion of the actual lake diving depth (ALDD) to an equivalent sea dive depth. SESD is defined as the sea depth in meters or feet for a standardized sea dive, equivalent to a mountain lake dive at any altitude, such that [image omitted] [image omitted] [image omitted] Mountain lakes contain fresh water with a relative density that can be standardized to 1,000 kg m(-3), and sea water can likewise be standardized to a relative density of 1,033 kg m(-3), at the general gravity of 9.80665 m s(-2). The water density ratio (1,000/1,033) refers to the fresh lake water and the standardized sea water densities. Following calculation of the SESD factor, we recommend the use of our simplified diving table or any acceptable sea level dive table with two fundamental guidelines: 1. The classical decompression stages (30, 20, and 10 feet or 9, 6, and 3 m) are corrected to the altitude lake level, dividing the stage depth by the SESD factor. 2. Likewise, the lake ascent rate during diving is equal to the sea ascent rate divided by the SESD factor. PMID:17987509

Paulev, Poul-Erik; Zubieta-Calleja, Gustavo

274

WAVECALC: an Excel-VBA spreadsheet to model the characteristics of fully developed waves and their influence on bottom sediments in different water depths  

NASA Astrophysics Data System (ADS)

The generation and growth of waves in deep water is controlled by winds blowing over the sea surface. In fully developed sea states, where winds and waves are in equilibrium, wave parameters may be calculated directly from the wind velocity. We provide an Excel spreadsheet to compute the wave period, length, height and celerity, as well as horizontal and vertical particle velocities for any water depth, bottom slope, and distance below the reference water level. The wave profile and propagation can also be visualized for any water depth, modeling the sea surface change from sinusoidal to trochoidal and finally cnoidal profiles into shallow water. Bedload entrainment is estimated under both the wave crest and the trough, using the horizontal water particle velocity at the top of the boundary layer. The calculations are programmed in an Excel file called WAVECALC, which is available online to authorized users. Although many of the recently published formulas are based on theoretical arguments, the values agree well with several existing theories and limited field and laboratory observations. WAVECALC is a user-friendly program intended for sedimentologists, coastal engineers and oceanographers, as well as marine ecologists and biologists. It provides a rapid means to calculate many wave characteristics required in coastal and shallow marine studies, and can also serve as an educational tool.

Le Roux, Jacobus P.; Demirbilek, Zeki; Brodalka, Marysia; Flemming, Burghard W.

2010-10-01

275

Phase 1 summaries of radionuclide concentration data for vegetation, river water, drinking water, and fish. Hanford Environmental Dose Reconstruction Project  

SciTech Connect

The objective of the Hanford Environmental Dose Reconstruction (HEDR) Project is to estimate the radiation doses that individuals and populations could have received from nuclear operations at the Hanford Site since 1944. As part of the HEDR Project, the Environmental Monitoring Data Task (Task 05) staff assemble, evaluate, and summarize key historical measurements of radionuclide concentrations in the environment as a result of Hanford operations. The scope of work performed during Phase I included initiating the search, recovery, and inventory of environmental reports. Summaries of the environmental monitoring data that were recovered and evaluated are presented for specific periods of interest. These periods include vegetation monitoring data (primarily sagebrush) for the years 1945 through 1947, Columbia River water and drinking water monitoring data for the years 1963 through 1966, and fish monitoring data for the years 1964 through 1966. Concern was limited to those radionuclides identified as the most likely major contributors to the dose potentially received by the public during the times of interest: phosphorous-32, copper-64, zinc-65, arsenic-76, and neptunium-239 in Columbia River fish and drinking water taken from the river, and iodine-131 in vegetation. This report documents the achievement of the Phase I objectives of the Environmental Monitoring Data Task.

Denham, D.H.; Dirkes, R.L.; Hanf, R.W.; Poston, T.M.; Thiede, M.E.; Woodruff, R.K.

1993-06-01

276

Radioactivity measurements and radiation dose evaluation in tap waters of Central Italy.  

PubMed

Consumption of drinking water is very important for human nutrition and its quality must be strictly controlled. A study of radioactivity content in tap water samples collected in the Central Italy was performed in order to check the compliance with recent European regulations. Gross alpha and beta activity, 226Ra, 238U and 234U concentrations were measured. Gross alpha and beta activities were determined by standard ISO 9696 and ISO 9697; for 226Ra determination liquid scintillation was used. 238U and 234U concentrations were determined by alpha spectrometry after separation from matrix by extraction chromatography and electroplating. Recommended WHO guideline activity concentrations for drinking water (0.1 and 1.0 Bq/L for gross alpha and gross beta activity, respectively) are exceeded in two cases for gross alpha activity and are not exceeded in any case for gross beta activity. The concentrations (mBq/L) of 226Ra, 238U and 234U ranged from <1.70 to 15.3, 0.65 to 48.8 and 0.780 to 51.5, respectively. Effective dose due to the uranium isotopes and radium was calculated for children and adults using the dose coefficients reported by EC Directive 96/29 EURATOM and annual water intake. For all class ages, the doses are quite similar and much lower than 0.1 mSv/year. PMID:17688298

Desideri, Donatella; Roselli, Carla; Assunta Meli, Maria; Feduzi, Laura; Rongoni, Alba; Saetta, Daniela

2007-09-01

277

Depth of penetration of the neodymium: yttrium-aluminum-garnet laser in the human prostate and clinical results of high-dose laser energy in 50 patients  

Microsoft Academic Search

We evaluated the treatment of the human prostate with the Nd:YAG laser using a Cytocare Prolase II fiber. We utilized this first in 12 patients prior to radical prostatectomy and then appropriately serially sectioned the prostate to measure the depth of penetration. The studies clearly revealed that 60 W of power and 60 s of pulse duration gave the most

A. M. Shanberg; D. E. Sawyer; I. S. Lee; L. W. Rodgers; L. A. Tansey; T. Ahlering

1995-01-01

278

Diatom habitats, species diversity and water-depth inference models across surface-sediment transects in Worth Lake, northwest Ontario, Canada  

Microsoft Academic Search

We analyzed surface-sediment samples collected along transects from three sub-basins of a relatively large (~115 ha), bathymetrically\\u000a complex lake, in northwest Ontario, Canada, to assess the reproducibility of diatom species habitats and diversity along a\\u000a water-depth gradient. Transects displayed different orientations with respect to prevailing wind direction and varied in complexity\\u000a and degree of slope along the lake bottom. Each transect

Kathleen R. LairdMelanie; Melanie V. Kingsbury; Brian F. Cumming

2010-01-01

279

Shipboard sunphotometer measurements of aerosol optical depth spectra and columnar water vapor during ACE2, and comparison with selected land, ship, aircraft, and satellite measurements  

Microsoft Academic Search

Analyses of aerosol optical depth (AOD) and columnar water vapor (CWV) measurements acquired with NASA Ames Research Center's 6-channel Airborne Tracking Sunphotometer (AATS-6) operated aboard the R\\/V Professor Vodyanitskiy during the 2nd Aerosol Characterization Experiment (ACE-2) are discussed. Data are compared with various in situ and remote measurements for selected cases. The focus is on 10 July, when the Pelican

John M. Livingston; Vladimir N. Kapustin; Beat Schmid; Philip B. Russell; Patricia K. Quinn; Timothy S. Bates; Philip A. Durkee; Peter J. Smith; Volker Freudenthaler; Matthias Wiegner; Dave S. Covert; Santiago Gassó; Dean Hegg; Donald R. Collins; Richard C. Flagan; John H. Seinfeld; Vito Vitale; Claudio Tomasi

2000-01-01

280

Airborne Sun photometer measurements of aerosol optical depth and columnar water vapor during the Puerto Rico Dust Experiment and comparison with land, aircraft, and satellite measurements  

Microsoft Academic Search

Analyses of aerosol optical depth (AOD) and columnar water vapor (CWV) measurements obtained with the six-channel NASA Ames Airborne Tracking Sunphotometer (AATS-6) mounted on a twin-engine aircraft during the summer 2000 Puerto Rico Dust Experiment are presented. In general, aerosol extinction values calculated from AATS-6 AOD measurements acquired during aircraft profiles up to 5 km above sea level (asl) reproduce

John M. Livingston; Philip B. Russell; Jeffrey S. Reid; Jens Redemann; Beat Schmid; Duane A. Allen; Omar Torres; Robert C. Levy; Lorraine A. Remer; Brent N. Holben; Alexander Smirnov; Oleg Dubovik; Ellsworth J. Welton; James R. Campbell; Jun Wang; Sundar A. Christopher

2003-01-01

281

The effects that well depth and wellhead protection have on bacterial contamination of private water wells in the Estes Park Valley, Colorado.  

PubMed

Over the past five years, it is estimated that 10% of residential water wells have tested positive for total coliform and 2% for E.coli bacteria in the Estes Park Valley, Colorado. Many of these water wells are shallow or hand-dug in construction. In this study, samplings of 30 private untreated water wells were tested for total coliform bacteria in the Estes Park Valley. Water wells were classified into three categories for well depth (<99 feet [30.2 m], 100-199 feet [30.5-60.7 m], and >200 feet [61 m]) and for wellhead protection (poor, fair, and good). Results indicated that 71% of the wells less than 199 feet (60.7 m) tested positive for total coliform (chi2 = 15.559, p < .0001). Also, 71% of wells classified as having poor and fair wellhead protection tested positive for total coliform (chi2 = 13.084, p = .001). This study determined that wellhead protection and well depth does play a role in bacterial contamination of water wells. PMID:19115719

Gonzales, Thomas R

2008-12-01

282

Behavioural thermoregulation in Daphnia carinata from different depths of a natural water body: influence of environmental oxygen levels and temperature  

Microsoft Academic Search

The influence of environmental parameters (water temperature and dissolved oxygen content) on the haemoglobin content of a naturally occurring population of Daphnia carinata was studied in a population resident in an intermittently flowing, shallow body of water. It was found that the Hb content of the animals was influenced by a combination of both the water temperature and dissolved oxygen

P. R Wiggins; P. B Frappell

2002-01-01

283

Dose to tissue medium or water cavities as surrogate for the dose to cell nuclei at brachytherapy photon energies.  

PubMed

It has been suggested that modern dose calculation algorithms should be able to report absorbed dose both as dose to the local medium, D(m,m,) and as dose to a water cavity embedded in the medium, D(w,m), using conversion factors from cavity theory. Assuming that the cell nucleus with its DNA content is the most important target for biological response, the aim of this study is to investigate, by means of Monte Carlo (MC) simulations, the relationship of the dose to a cell nucleus in a medium, D(n,m,) to D(m,m) and D(w,m), for different combinations of cell nucleus compositions and tissue media for different photon energies used in brachytherapy. As D(n,m) is very impractical to calculate directly for routine treatment planning, while D(m,m) and D(w,m) are much easier to obtain, the questions arise which one of these quantities is the best surrogate for D(n,m) and which cavity theory assumptions should one use for its estimate. The Geant4.9.4 MC code was used to calculate D(m,m,) D(w,m) and D(n,m) for photon energies from 20 (representing the lower energy end of brachytherapy for ¹?³Pd or ¹²?I) to 300 keV (close to the mean energy of (¹?²Ir) and for the tissue media adipose, breast, prostate and muscle. To simulate the cell and its nucleus, concentric spherical cavities were placed inside a cubic phantom (10 × 10 × 10 mm³). The diameter of the simulated nuclei was set to 14 µm. For each tissue medium, three different setups were simulated; (a) D(n,m) was calculated with nuclei embedded in tissues (MC-D(n,m)). Four different published elemental compositions of cell nuclei were used. (b) D(w,m) was calculated with MC (MC-D(w,m)) and compared with large cavity theory calculated D(w,m) (LCT-D(w,m)), and small cavity theory calculated D(w,m) (SCT-D(w,m)). (c) D(m,m) was calculated with MC (MC-D(m,m)). MC-D(w,m) is a good substitute for MC-D(n,m) for all photon energies and for all simulated nucleus compositions and tissue types. SCT-D(w,m) can be used for most energies in brachytherapy, while LCT-D(w,m) should only be considered for source spectra well below 50 keV, since contributions to the absorbed dose inside the nucleus to a large degree stem from electrons released in the surrounding medium. MC-D(m,m) is not an appropriate substitute for MC-D(n,m) for the lowest photon energies for adipose and breast tissues. The ratio of MC-D(m,m) to MC-D(n,m) for adipose and breast tissue deviates from unity by 34% and 15% respectively for the lowest photon energy (20 keV), whereas the ratio is close to unity for higher energies. For prostate and muscle tissue MC-D(m,m) is a good substitute for MC-D(n,m). However, for all photon energies and tissue types the nucleus composition with the highest hydrogen content behaves differently than other compositions. Elemental compositions of the tissue and nuclei affect considerably the absorbed dose to the cell nuclei for brachytherapy sources, in particular those at the low-energy end of the spectrum. Thus, there is a need for more accurate data for the elemental compositions of tumours and healthy cells. For the nucleus compositions and tissue types investigated, MC-D(w,m) is a good substitute to MC-D(n,m) for all simulated photon energies. Whether other studied surrogates are good approximations to MC-D(n,m) depends on the target size, target composition, composition of the surrounding tissue and photon energy. PMID:22722477

Enger, Shirin A; Ahnesjö, Anders; Verhaegen, Frank; Beaulieu, Luc

2012-06-22

284

Herbicide dose and incorporation depth in combination with 1,3-dichloropropene plus chloropicrin for Cyperus rotundus control in tomato and pepper  

Microsoft Academic Search

Field trials were conducted to compare the efficacy of various herbicides in combination with 1,3-dichloropropene plus chloropicrin (C-17) on Cyperus rotundus (purple nutsedge) control and their effect on tomato and pepper yields, and to determine the appropriate herbicide application depth in the soil for purple nutsedge control in polyethylene-mulched tomato and pepper fields. The various chemical treatments were incorporated into

James P. Gilreath; Bielinski M. Santos

2004-01-01

285

Thermal responses for men with different fat compositions during immersion in cold water at two depths: prediction versus observation  

Microsoft Academic Search

A cold thermoregulatory model (CTM) was applied to data from partially immersed subjects divided into normal (NF) or low fat (LF) groups in order to validate\\u000a CTM during immersion at two depths and to examine mechanisms underlying the individual differences. CTM defines thermal characteristics,\\u000a e.g. surface area and maximal shivering intensity, using height, weight, fat %, age and VO2max. Ten

Xiaojiang Xu; John W. Castellani; William Santee; Margaret Kolka

2007-01-01

286

Conductivity Temperature Depth Profiler (CTD)  

USGS Multimedia Gallery

These are the lids both on top and below the water bottles on the Conductivity Temperature Depth Profiler (CTD). When the CTD is placed in the ocean and reaches a desired depth, an electronic signal is sent from the ship that closes the bottles and a water sample is collected. ...

2008-12-09

287

Conductivity Temperature Depth Profiler (CTD)  

USGS Multimedia Gallery

This is the top of the Conductivity Temperature Depth Profiler (CTD). When the instrument is lowered into the water and reaches a desired depth, an electronic signal is sent along these wires from the ship that closes the bottles and a water sample is collected. ...

2008-12-09

288

Well Wishes: A Case on Septic Systems and Well Water Requiring In-Depth Analysis and Including Optional Laboratory Experiments  

ERIC Educational Resources Information Center

|The case of Well Wishes involves students in a thorough examination of the interaction among nitrogen-composed species in the septic systems and well water, which helps to clean household water. The case supports the attainment of five goals for students, and can be analyzed through classroom discussions or laboratory experiments.|

Walczak, Mary M.; Lantz, Juliette M.

2004-01-01

289

RELATION OF WATER TABLE DEPTH AND SOIL MORPHOLOGY IN TWO CLAY-RICH SOILS OF NORTHWESTERN OHIO1  

Microsoft Academic Search

Water table levels within the upper 165 cm of the soil and precipitation were measured over a three—yr period for two forested soils representative of clay-rich soils common throughout much of northwestern Ohio. The soils included very poorly drained Hoytville taxadjunct (fine, illitic, mesic Typic Haplaquept) and moderately well drained Glynwood (fine, illitic, mesic Aquic Hapludalf). A water table was

TED M. ZOBECK; A. RITCHIE

1984-01-01

290

Seagrass Depth Limits in the Indian River Lagoon (Florida, U.S.A.): Application of an Optical Water Quality Model  

Microsoft Academic Search

A model of spectral diffuse attenuation coefficient for downwelling irradiance in terms of the inherent optical properties of optically important water quality parameters was calibrated near two seagrass beds in the Indian River Lagoon, Florida, U.S.A. One of the seagrass sites was near the outflow of a canal discharging highly coloured water, and is regularly inundated by a plume of

C. L. Gallegos; W. J. Kenworthy

1996-01-01

291

Sonar depth sounder apparatus  

US Patent & Trademark Office Database

An improved microprocessor-controlled sonar depth sounder, which is automatically operative to detect and lock to the bottom of a body of water, fill in the display below the detected bottom, change display scales in response to the detected bottom going off-scale, and reformat the entire display in response to a scale change. A memory is provided for storing target data up to the operable depth limits of the device, thereby allowing display reversing and display expansion or "zoom" of a predetermined portion of the display selected by a zoom cursor. The zoom or cursor is variably positionable at different depths. The device employs an improved variable sensitivity amplifier. Also disclosed is an improved water-resistant switch construction for marine electronic equipment.

1989-10-10

292

Monte-Carlo calculations of radial dose and restricted-let for protons in water.  

PubMed

A new Monte-Carlo code for event-by-event simulation of the transport of energetic non-relativistic protons (approximately 0.5-10 MeV) and all their secondary electrons (down to 1 Ry) in both the vapour and liquid phases of water is presented. A unified particle-water inelastic model for both phases of water has been developed based on experimental optical data and elements of the Bethe theory. The model applies to both electrons and heavy-charged particles and is particularly suitable for extension to other media of biological relevance (organic polymers, DNA, etc.). Condensed-phase effects are included in the liquid version (MC4L) by means of the dielectric functions which, essentially, substitute the oscillator-strength used in the vapour version (MC4V). The results in the form of radial dose distributions and spatially restricted linear energy transfer are presented and compared with the literature. PMID:15353761

Emfietzoglou, D; Karava, K; Papamichael, G; Moscovitch, M

2004-01-01

293

[Radiation doses in the population of the coastal area of the Kakhovsk Water Reservoir].  

PubMed

The Chernobyl accident resulted in environmental radionuclide pollution in many areas, including the Dnepr river. The water and fish of the Kakhovsk Water Reservoir were under study and tested for 90Sr and 137Cs. It was found that the content of 137Cs achieved pre-accident levels and that of 90Sr was 4-6 times higher than that prior to the accident. The fish levels of the above radionuclides were 10-20 times as high as the pre-accident levels. Due to the consumption of fish, the radiation doses of the radionuclides, mainly 90Sr, in the population living in the costal areas of the Kakhovsk Water Reservoir were 20-30 times higher than the pre-accident levels. PMID:9662887

Kostenetski?, M I; Gribinenko, G T; Kravtsova, L S; Ryzhova, G L; Khripko, Z A

294

A critical review of measures to reduce radioactive doses from drinking water and consumption of freshwater foodstuffs  

Microsoft Academic Search

Following a radioactive fallout event, there are a number of possible intervention measures to reduce radioactive doses to the public via the surface water pathway. We have critically reviewed the options available to decision-makers in the event of radioactive contamination of surface waters. We believe that the most effective and viable measures to reduce radioactivity in drinking water are those

J. T Smith; O. V Voitsekhovitch; L Håkanson; J Hilton

2001-01-01

295

Diversity of active aerobic methanotrophs along depth profiles of arctic and subarctic lake water column and sediments.  

PubMed

Methane (CH(4)) emitted from high-latitude lakes accounts for 2-6% of the global atmospheric CH(4) budget. Methanotrophs in lake sediments and water columns mitigate the amount of CH(4) that enters the atmosphere, yet their identity and activity in arctic and subarctic lakes are poorly understood. We used stable isotope probing (SIP), quantitative PCR (Q-PCR), pyrosequencing and enrichment cultures to determine the identity and diversity of active aerobic methanotrophs in the water columns and sediments (0-25 cm) from an arctic tundra lake (Lake Qalluuraq) on the north slope of Alaska and a subarctic taiga lake (Lake Killarney) in Alaska's interior. The water column CH(4) oxidation potential for these shallow (?2 m deep) lakes was greatest in hypoxic bottom water from the subarctic lake. The type II methanotroph, Methylocystis, was prevalent in enrichment cultures of planktonic methanotrophs from the water columns. In the sediments, type I methanotrophs (Methylobacter, Methylosoma and Methylomonas) at the sediment-water interface (0-1 cm) were most active in assimilating CH(4), whereas the type I methanotroph Methylobacter and/or type II methanotroph Methylocystis contributed substantially to carbon acquisition in the deeper (15-20 cm) sediments. In addition to methanotrophs, an unexpectedly high abundance of methylotrophs also actively utilized CH(4)-derived carbon. This study provides new insight into the identity and activity of methanotrophs in the sediments and water from high-latitude lakes. PMID:22592821

He, Ruo; Wooller, Matthew J; Pohlman, John W; Quensen, John; Tiedje, James M; Leigh, Mary Beth

2012-05-17

296

Diversity of active aerobic methanotrophs along depth profiles of arctic and subarctic lake water column and sediments  

PubMed Central

Methane (CH4) emitted from high-latitude lakes accounts for 2–6% of the global atmospheric CH4 budget. Methanotrophs in lake sediments and water columns mitigate the amount of CH4 that enters the atmosphere, yet their identity and activity in arctic and subarctic lakes are poorly understood. We used stable isotope probing (SIP), quantitative PCR (Q-PCR), pyrosequencing and enrichment cultures to determine the identity and diversity of active aerobic methanotrophs in the water columns and sediments (0–25?cm) from an arctic tundra lake (Lake Qalluuraq) on the north slope of Alaska and a subarctic taiga lake (Lake Killarney) in Alaska's interior. The water column CH4 oxidation potential for these shallow (?2?m deep) lakes was greatest in hypoxic bottom water from the subarctic lake. The type II methanotroph, Methylocystis, was prevalent in enrichment cultures of planktonic methanotrophs from the water columns. In the sediments, type I methanotrophs (Methylobacter, Methylosoma and Methylomonas) at the sediment-water interface (0–1?cm) were most active in assimilating CH4, whereas the type I methanotroph Methylobacter and/or type II methanotroph Methylocystis contributed substantially to carbon acquisition in the deeper (15–20?cm) sediments. In addition to methanotrophs, an unexpectedly high abundance of methylotrophs also actively utilized CH4-derived carbon. This study provides new insight into the identity and activity of methanotrophs in the sediments and water from high-latitude lakes.

He, Ruo; Wooller, Matthew J; Pohlman, John W; Quensen, John; Tiedje, James M; Leigh, Mary Beth

2012-01-01

297

Allograft heart valve sterilization: A six-year in-depth analysis of a twenty-five–year experience with low-dose antibiotics  

Microsoft Academic Search

At the Prince Charles Hospital, from a 25-year experience with allograft heart valves (1969 to 1994), a 6-year analysis from March 1988 to August 1994 of the contamination rates and efficiency of a short-duration, low-dose antibiotic sterilization protocol was made. This analysis covered 642 collections and 680 aortic and pulmonary valve implants. Tissue samples obtained at collection, valve trimming, postantibiotic

Ken Gall; Susan Smith; Christene Willmette; Mae Wong; Mark O'Brien

1995-01-01

298

Three-dimensional Green's function for harmonic water waves over a bottom topography with different depths at infinity  

Microsoft Academic Search

The three-dimensional Green's function of water waves in variable-bathymetry regions, associated with the problem of propagation of water waves emitted from a monochromatic point source, is derived and studied. The solution is of interest in its own right but also provides useful information for the formulation and treatment of complex wave body seabed interaction problems in variable-bathymetry regions, especially as

K. A. Belibassakis; G. A. Athanassoulis

2004-01-01

299

Design of a Shadowband Spectral Radiometer for the Retrieval of Thin Cloud Optical Depth, Liquid Water Path, and the Effective Radius  

SciTech Connect

The design and operation of a Thin-Cloud Rotating Shadowband Radiometer (TCRSR) described here was used to measure the radiative intensity of the solar aureole and enable the simultaneous retrieval of cloud optical depth, drop effective radius, and liquid water path. The instrument consists of photodiode sensors positioned beneath two narrow metal bands that occult the sun by moving alternately from horizon to horizon. Measurements from the narrowband 415-nm channel were used to demonstrate a retrieval of the cloud properties of interest. With the proven operation of the relatively inexpensive TCRSR instrument, its usefulness for retrieving aerosol properties under cloud-free skies and for ship-based observations is discussed.

Bartholomew M. J.; Reynolds, R. M.; Vogelmann, A. M.; Min, Q.; Edwards, R.; Smith, S.

2011-11-01

300

Design and implementation of a water phantom for IMRT, arc therapy, and tomotherapy dose distribution measurements  

SciTech Connect

The aim of this paper is to present a new phantom for arc therapy, intensity-modulated radiation therapy (IMRT), and tomotherapy dose distribution measurement in pretreatment verification. The presented phantom is innovative for its use of water as the tissue equivalent material, together with a technical solution specifically designed to support radiographic or radiochromic film and ionization chambers in any desired position. The phantom comprise a Plexiglas container, whose present shape and dimensions offer the possibility to simulate a human torso or abdomen; the container can be filled with water by opening the upper cover. On the internal side of the cover, a set of carbon pipes can support film in the desired coronal, axial, or sagittal planes. At one of the two ends of the phantom, an ionization chamber can be positioned parallel to the rotation axis of the accelerator gantry in all possible positions within a 20 cm diameter cylinder, for film calibration purposes. Inhomogeneities can be inserted into the phantom using the same carbon pipes and plastic sheets used to support film. An example of vertebra-shaped inserts made of bone equivalent material is reported. Radiochromic film can be dipped in water, while radiographic film must be protected to prevent damage. To accomplish this, radiographic film is laminated using a cold laminating film. In order to assess the effects of both the lamination itself and the effects of water on laminated Kodak EDR2 film, the optical density (OD) of conventional, laminated, and laminated film immersed in water and exposed to a range of doses from 0 to 300 cGy were compared. The OD of the three samples receiving the same radiation dose did not present any significant difference, thus proving that laminated EDR2 film can also be used in water. A prerequisite for any dosimetric comparison between planned and measured data is a proper film to plan registration. The solution proposed here is an extrinsic in-plane registration technique using four reference points marked on each film in predefined positions. The four points and the millimeter scales fixed on the carbon pipes that support the film are designed and manufactured so as to transfer onto the film the same reference system used during the planning procedure, thus allowing a straightforward registration. Tests to assess the accuracy of the proposed registration method demonstrate that the distances between measured and intended marker positions, evaluated for coronal, axial, and sagittal planes, were about 1 mm for both anteroposterior and lateral projections.

Pallotta, Stefania; Marrazzo, Livia; Bucciolini, Marta [Dipartimento di Fisiopatologia Clinica, Universita degli Studi di Firenze, Florence (Italy)

2007-10-15

301

Effect of contrast water therapy duration on recovery of cycling performance: a dose–response study  

Microsoft Academic Search

This study investigated whether contrast water therapy (CWT) has a dose–response effect on recovery from high-intensity cycling.\\u000a Eleven trained male cyclists completed four trials, each commencing with a 75-min cycling protocol containing six sets of\\u000a five 15-s sprints and three 5-min time-trials in thermoneutral conditions. Ten minutes post-exercise, participants performed\\u000a one of four recovery protocols: CWT for 6 min (CWT6), 12 min

Nathan Versey; Shona Halson; Brian Dawson

2011-01-01

302

Comparison of the standards for absorbed dose to water of the VNIIFTRI, Russia and the BIPM in 60Co ? rays  

Microsoft Academic Search

A new comparison of the standards for absorbed dose to water of the All-Russian Scientific Research Institute for Physical-Technical and Radiotechnical Measurements (VNIIFTRI), Russia and of the Bureau International des Poids et Mesures (BIPM) has been made in 60Co gamma radiation in 2009. The results show that the VNIIFTRI and the BIPM standards for absorbed dose to water are in

P J Allisy-Roberts; C Kessler; D T Burns; V Berlyand; A Berlyand

2010-01-01

303

Ultra-thin TLDs for skin dose determination in high energy photon beams  

Microsoft Academic Search

Estimation of surface dose is very important for patients undergoing radiation therapy. In this work we investigate the dose at the surface of a water phantom and at a depth of 0.007 cm, the practical reference depth for skin as recommended by ICRP and ICRU, with ultra-thin TLDs and Monte Carlo calculations. The calculations and measurements were carried out for

S. Stathakis; J. S. Li; K. Paskalev; J. Yang; L. Wang; C.-M. Ma

2006-01-01

304

Geometrical ?- and ?-dose distributions and production rates of radiolysis products in water in contact with spent nuclear fuel  

NASA Astrophysics Data System (ADS)

A mathematical model for the dose distribution and production rates of radiolysis products in water surrounding spent nuclear fuel has been developed, based on the geometrical and energetic properties of radiation. The nuclear fuel particle is divided into layers, from which the radiation emits. The water is likewise divided into layers, where the doses are distributed. The doses are stored in vectors which are added to determine the total dose rate. A complete inventory with over 200 radionuclides has been used as input data for the model. The purpose of the model is to describe the geometrical dose distribution as a function of fuel age and burn-up, to be used as input data for kinetic modeling of the fuel dissolution. The results show that the ?-dose contribution close to the spent fuel surface is negligible. Also, the variation in the relative ?/? dose contribution between different ages and burn-ups is insignificant. The ?- and ?-dose rates vary between different burn-ups of the same age; the younger the fuel is, the larger is the difference. Exponential functions have been fitted to the relations between fuel age and average dose rate, giving useful expressions for determining average dose rates for fuel ages other than those covered in this work.

Nielsen, Fredrik; Jonsson, Mats

2006-12-01

305

Deep-water rice production as influenced by time and depth of flooding on the east coast of India  

Microsoft Academic Search

The saucer-shaped landform, high rainfall due to the south-west monsoon (June–September) and poor drainage conditions make certain parts of the east coast of India susceptible to waterlogging during the rainy season. There is no alternative other than to grow rice in the coastal lowlands, where surface water accumulation of 0.5–2.0 m occurs during the rainy season. In this study, the physical

Gouranga Kar; Narayan Sahoo; Ashwani Kumar

2012-01-01

306

Deep-water rice production as influenced by time and depth of flooding on the east coast of India  

Microsoft Academic Search

The saucer-shaped landform, high rainfall due to the south-west monsoon (June–September) and poor drainage conditions make certain parts of the east coast of India susceptible to waterlogging during the rainy season. There is no alternative other than to grow rice in the coastal lowlands, where surface water accumulation of 0.5–2.0 m occurs during the rainy season. In this study, the physical

Gouranga Kar; Narayan Sahoo; Ashwani Kumar

2011-01-01

307

Effect of contrast water therapy duration on recovery of cycling performance: a dose-response study.  

PubMed

This study investigated whether contrast water therapy (CWT) has a dose-response effect on recovery from high-intensity cycling. Eleven trained male cyclists completed four trials, each commencing with a 75-min cycling protocol containing six sets of five 15-s sprints and three 5-min time-trials in thermoneutral conditions. Ten minutes post-exercise, participants performed one of four recovery protocols: CWT for 6 min (CWT6), 12 min (CWT12), or 18 min (CWT18) duration, or a seated rest control trial. The CWT commenced in hot water (38.4 ± 0.6°C) and alternated between hot and cold water (14.6 ± 0.3°C) every minute with a 5-s changeover. The cycling protocol was repeated 2 h after completion of exercise bout one. Prior to exercise bout two, core temperature was lower in CWT12 (-0.19 ± 0.14°C, mean ± 90% CL) and CWT18 (-0.21 ± 0.10°C) than control. Compared with control, CWT6 substantially improved time-trial (1.5 ± 2.1%) and sprint performance (3.0 ± 3.1%), and CWT12 substantially improved sprint total work (4.3 ± 3.4%) and peak power (2.7 ± 3.8%) in exercise bout two. All CWT conditions generally improved thermal sensation, whole body fatigue and muscle soreness compared with control, but no differences existed between conditions in heart rate or rating of perceived exertion. In conclusion, CWT duration did not have a dose-response effect on recovery from high-intensity cycling; however, CWT for up to 12 min assisted recovery of cycling performance. PMID:20809231

Versey, Nathan; Halson, Shona; Dawson, Brian

2010-09-01

308

The Effects of Periphyton, Fish and Fertilizer Dose on Biological Processes Affecting Water Quality in Earthen Fish Ponds  

Microsoft Academic Search

The potential of periphyton-based aquaculture in South Asia is under investigation in an extensive research program. This paper is a further analysis of data from four experiments carried out in that framework, to explore periphyton, fish and fertilizer dose effects on water quality. Factor analysis and ANOVA models applied to a data matrix of water quality parameters in ponds with

Ana Milstein; Mohammed Ekram Azim; Mohammed Abdul Wahab; Marc Charles Jean Verdegem

2003-01-01

309

Dose–effect relationship between drinking water fluoride levels and damage to liver and kidney functions in children  

Microsoft Academic Search

Although a dose–effect relationship between water fluoride levels and damage to liver and kidney functions in animals has been reported, it was not demonstrated in humans. To evaluate the effects of drinking water fluoride levels on the liver and kidney functions in children with and without dental fluorosis, we identified 210 children who were divided into seven groups with 30

XianZhi Xiong; JunLing Liu; WeiHong He; Tao Xia; Ping He; XueMin Chen; KeDi Yang; AiGuo Wang

2007-01-01

310

Evaluation of effective dose for a patient under Ga-67 nuclear examination using TLD, water phantom and a simplified model.  

PubMed

This study evaluated the effective dose of Ga-67 for a patient undergoing Ga-67 citrate nuclear examination by applying thermoluminescent dosimeter (TLD) technique and an indigenous water phantom. The Ga-67 radionuclide remaining in the body inevitably generated a measurable internal dose even though gamma camera scanning took only minutes to complete the clinical examination. For effective simulation of the cumulated effective dose for a patient undergoing examination, 150 TLDs were placed inside the water phantom for 6 days to monitor the gamma ray dose from the distributed Ga-67 citrate solution. The inserted TLDs represented internal organs, and the effective dose was calculated according to data in the ICRP-60 report. The water phantom was designed to model the body of a healthy human weighing 70 kg, and the water that was mixed with Ga-67 citrate solution was slowly replaced with fresh feed water to yield the required biological half life of the phantom. After continuously feeding in fresh water throughout the 6 days of TLD exposure, the TLDs were analyzed to determine the effective doses from the various biological half lives of the phantom. The derived effective dose of 185 MBq Ga-67 citrate solution for male/female (M/F) was 10.7/12.2, 10.7/12.0, 8.7/9.9 and 6.0/6.8 mSv, of biological half lives of 6.0, 4.5, 3.0 and 1.5 days, respectively. Although these experimental results correlated well with earlier empirical studies, they were lower than most calculated values. The cumulated uncertainty in the effective dose was 12.5-19.4%, which was acceptable in terms of both TLD counting statistic and reproducibility. PMID:22915780

Chu, Kuang Hua; Lin, Yu Ting; Hsu, Chia Chun; Chen, Chien Yi; Pan, Lung Kwang

2012-08-21

311

Regional and local patterns in depth to water table, hydrochemistry and peat properties of bogs and their laggs in coastal British Columbia  

NASA Astrophysics Data System (ADS)

In restoration planning for damaged raised bogs, the lagg at the bog margin is often not given considerable weight and is sometimes disregarded entirely. However, the lagg is critical for the proper functioning of the bog, as it supports the water mound in the bog. In order to include the lagg in a restoration plan for a raised bog, it is necessary to understand the hydrological characteristics and functions of this rarely studied transition zone. We studied 13 coastal British Columbia (BC) bogs and identified two different gradients in depth to water table, hydrochemistry and peat properties: (1) a local bog expanse-bog margin gradient, and (2) a regional gradient related to climate and proximity to the ocean. Depth to water table generally increased across the transition from bog expanse to bog margin. In the bog expanse, pH was above 4.2 in the Pacific Oceanic wetland region (cooler and wetter climate) and below 4.3 in the Pacific Temperate wetland region (warmer and drier climate). Both pH and pH-corrected electrical conductivity increased significantly across the transition from bog expanse to bog margin, though not in all cases. Na+ and Mg2+ concentrations were generally highest in exposed, oceanic bogs and lower in inland bogs. Ash content in peat samples increased across the bog expanse-bog margin transition, and appears to be a useful abiotic indicator of the location of the bog margin. The observed variation in the hydrological and hydrochemical gradients across the bog expanse-bog margin transition highlights both local and regional diversity of bogs and their associated laggs.

Howie, S. A.; van Meerveld, H. J.

2013-09-01

312

Regional and local patterns in depth to water table, hydrochemistry, and peat properties of bogs and their laggs in coastal British Columbia  

NASA Astrophysics Data System (ADS)

In restoration planning for damaged raised bogs, the lagg at the bog margin is usually not given considerable weight and is sometimes disregarded entirely. However, the lagg is critical for the proper functioning of the restored bog, as it supports the water mound in the bog. In order to include the lagg in a restoration plan for a raised bog, it is necessary to understand the ecohydrological characteristics and functions of this transition zone. To this end, we studied 13 coastal British Columbia (BC) bogs and identified two different gradients in depth to water table, hydrochemistry, and peat properties: (1) a local bog expanse - bog margin gradient, and (2) a regional gradient related to climate and proximity to the ocean. Depth to water table generally increased across the transition from bog expanse to bog margin, but did not differ regionally. In the bog expanse, pH was above 4.2 in the Pacific Oceanic wetland region (cooler and wetter climate) and below 4.3 in the Pacific Temperate wetland region (warmer and drier climate). Both pH and pH-corrected electrical conductivity increased significantly across the transition from bog expanse to bog margin, though not in all cases. Sodium and magnesium concentrations were generally highest in exposed, oceanic bogs and lower in inland bogs. Ash content in peat samples increased across the bog expanse - bog margin transition, and appears to be a useful abiotic indicator of the location of the bog margin. These gradients highlight both local and regional diversity of bogs and their associated laggs. Knowledge of these gradients is critical if undisturbed bogs are used as templates for the restoration of damaged raised bogs.

Howie, S. A.; van Meerveld, H. J.

2013-03-01

313

Topic in Depth - Chlorine  

NSDL National Science Digital Library

Chlorine, a chemical element whose name means âÂÂpale green,â is explored from a number of angles in this informative Topic in Depth.WeâÂÂve all heard of chlorine being used in swimming pools and drinking water, but this jack-of-all-trades chemical element is also used in making everything from plastics and dry cleaning products to insecticides and pharmaceuticals.

2010-09-15

314

Dose effect for South Serbians due to 238U in natural drinking water.  

PubMed

The use of depleted uranium ammunition in South Serbia during the 1999 Kosovo conflict raised a great deal of public concern in the Balkans. Radioactivity levels of 238U in 20 wells and lake water samples were checked from the viewpoint of internal radiation exposure for South Serbian subjects. We have measured 238U concentration using inductively coupled plasma mass spectrometry, whereas thermal ionisation mass spectrometry has been used for the measurement of isotope ratios, e.g. 234U/238U and 235U/238U. The concentration of uranium in water samples varies in the range 1.37-63.18 mBq/L. 234U belongs to the 238U natural radioactive decay series, and at secular equilibrium, the abundance ratio, 234U/238U, corresponds to the ratio of their half-lives. The 234U/238U activity ratio varies in the range 0.88-2.2 and 235U/238U isotope ratio varies from 0.00698 to 0.00745. These findings indicate that uranium in water was a mixture of natural and anthropogenic origin. The annual effective dose due to 238U was estimated to be in the range 9.2 x 10(-5)-2.1 x 10(-3) mSv. PMID:17567760

Sahoo, S K; Matsumoto, M; Shiraishi, K; Fujimoto, K; Cuknic, O; Zunic, Z S

2007-06-13

315

Quantitative oral dosing of water soluble and lipophilic contaminants in the Japanese medaka (Oryzias latipes)  

SciTech Connect

Quantitative oral dosing in fish can be challenging, particularly with water soluble contaminants, which can leach into the aquarium water prior to ingestion. We applied a method of bioencapsulation using newly hatched brine shrimp (Artemia franciscana) nauplii to study the toxicokinetics of five chlorinated and brominated halogenated acetic acids (HAAs), which are drinking water disinfection by-products. These results are compared to those obtained in a previous study using a polybrominated diphenyl ether (PBDE-47), a highly lipophilic chemical. The HAAs and PBDE-47 were bioencapsulated using freshly hatched A. franciscana nauplii after incubation in concentrated solutions of the study chemicals for 18 h. Aliquots of the brine shrimp were quantitatively removed for chemical analysis and fed to individual fish that were able to consume 400–500 nauplii in less than 5min. At select times after feeding, fish were euthanized and the HAA or PBDE-47 content determined. The absorption of HAAs was quantitatively similar to previous studies in rodents: rapid absorptionwith peak body levels occurringwithin 1–2 h, then rapidly declining with elimination half-life of 0.3–3 h depending on HAA. PBDE-47 was more slowly absorbed with peak levels occurring by 18 h and very slowly eliminated with an elimination half-life of 281 h.

Schultz, Irv; Reed, Stacey M.; Pratt, Amanda V.; Skillman, Ann D.

2007-02-01

316

Direct dose to water dosimetry for pretreatment IMRT verification using a modified EPID  

SciTech Connect

Purpose: Electronic portal imaging devices (EPIDs) are high resolution systems that produce electronic dose maps with minimal time required for equipment setup, and therefore potentially present a time-saving alternative for intensity modulated radiation therapy (IMRT) pretreatment verification. A modified commercial EPID was investigated operated with an opaque sheet blocking the optical signal produced in the phosphor layer as a precursor to a switched mode dual dosimetry-imaging EPID system. The purpose of this study was to investigate the feasibility of using this system for direct dose to water dosimetry for pretreatment IMRT verification. Methods: A Varian amorphous silicon EPID was modified by placing an opaque sheet between the Gd{sub 2}S{sub 2}O:Tb phosphor layer and the photodiode array to block the optical photons. The EPID was thus converted to a direct-detecting system (dEPID), in which the high energy radiation deposits energy directly in the photodiode array. The copper build-up was replaced with d{sub max} solid water. Sixty-one IMRT beams of varying complexity were delivered to the EPID, to EDR2 dosimetric film and to a 2D ion chamber array (MapCheck). EPID data was compared to film and MapCheck data using gamma analysis with 3%, 3mm pass criteria. Results: The fraction of points that passed the gamma test was on average 98.1% and 98.6%, for the EPID versus film and EPID versus MapCheck comparisons, respectively. In the case of comparison with film, the majority of observed discrepancies were associated with problems related to film sensitivity or processing. Conclusions: The very close agreement between EPID and both film and MapCheck data demonstrates that the modified EPID is suitable for direct dose to water measurement for pretreatment IMRT verification. These results suggest a reconfigured EPID could be an efficient and accurate dosimeter. Alternatively, optical switching methods could be developed to produce a dual-mode EPID with both dosimetry and imaging capabilities.

Gustafsson, Helen; Vial, Philip; Kuncic, Zdenka; Baldock, Clive; Denham, James W.; Greer, Peter B. [Institute of Medical Physics, School of Physics, University of Sydney, Sydney 2006 (Australia) and Northern Sydney Cancer Centre, Royal North Shore Hospital, Sydney 2065 (Australia); Institute of Medical Physics, School of Physics, University of Sydney, Sydney 2006 (Australia) and Department of Medical Physics, Liverpool and Macarthur Cancer Therapy Centres, Sydney 2170 (Australia); Institute of Medical Physics, School of Physics, University of Sydney, Sydney 2006 (Australia); School of Medicine and Public Health, University of Newcastle, Newcastle 2308 (Australia) and Radiation Oncology Department, Calvary Mater Newcastle Hospital, Newcastle 2310 (Australia); School of Mathematical and Physical Sciences, University of Newcastle, Newcastle 2308 (Australia) and Radiation Oncology Department, Calvary Mater Newcastle Hospital, Newcastle 2310 (Australia)

2011-11-15

317

Low-dose whey protein-enriched water beverages alter satiety in a study of overweight women  

Microsoft Academic Search

Aim: To determine the effect of low-dose whey protein-enriched water beverages on postprandial satiety and energy intake (EI). Methods: Fifty overweight and mildly obese women were given 500mL water-based beverages on 4 different occasions in a double blind, cross-over study. The beverages were reasonably matched for colour, flavour, sweetness and contained 0% (water control, 0g, 8kJ), 1% (5g, 93kJ), 2%

Sally D. Poppitt; Janie Proctor; Anne-Thea McGill; Katy R. Wiessing; Sofie Falk; Liping Xin; Stephanie C. Budgett; Alison Darragh; Ramon S. Hall

2011-01-01

318

Absorption of Different Doses of Fat Soluble and Water Miscible Preparations of Vitamin E in Children with Cystic Fibrosis  

PubMed Central

A comparison of the intestinal absorption of water miscible and fat soluble preparations of ?-tocopheryl acetate in children with cystic fibrosis showed the water miscible preparation to be more efficiently absorbed. In the absence of liver disease, a daily dose of 1 mg/kg body weight of a water miscible preparation can be expected to correct any pre-existing vitamin E deficiency within 2 months of starting treatment, and is adequate for subsequent maintenance.

Harries, J. T.; Muller, D. P. R.

1971-01-01

319

Spatial variability of soil apparent electrical conductivity(ECa) and the water table depth in an alluvial valley under different uses.  

NASA Astrophysics Data System (ADS)

The apparent soil electrical conductivity (ECa), measured by contact or by electromagnetic induction (EMI), has been widely used as a variable that is correlated with physical and chemical soil properties. Therefore this property is used as a parameter in precision agriculture, to enable assessment of soil spatial variability and defining management units, allowing obtaining information about other soil properties like texture, salinity, water content, among others. These conditions are adequate to study spatial variability of data with the help of geostatistics, which models the spatial variability of soil properties, allowing the construction of spatial variability maps unbiased and with minimum variance. Thus, the goal this work was assess the variability special of electrical conductivity apparent soil (ECa) and the water table level in an alluvial valley in the brazilian semi-arid adopting different uses. The studied alluvial valley is located in Pesqueira (Pernambuco State, Brazil) and has 421.0 hectares. The main soil types occurring in the valley are: Fluvic Neosols , litholic Neossols and regolithic Neosols . Climate according to Koppen's classification is BSsh type, with total annual rainfall average of 730mm. The attributes evaluated in this study were sampled at 88 piezometric wells. The apparent soil electrical conductivity (ECa) was measured by electromagnetic induction with the EM38 device (Geonics Ltd) in vertical dipole (effective depth 1.5m). The ground water table was determined in piezometric wells with the aid of a measuring tape. Data were analyzed by using descriptive statistics and geostatistical tools. The land use map was constructed using field verification and spatialized by means of GIS. The attributes analyzed showed Normal frequency distribution. ECa readings ranged between 8 and 79 mS m-1. The major differences between the ECa values are due to the variation of water content in soil and distance from the water table at the soil surface. The water table in the study area ranged from 0.8 to 3.8 m deep. The Pearson linear correlation found for the data in the study was zero (r = -0.0185). The Gaussian model was the best fit to the data, and the water table had the highest range value (a = 500.00 m). The maps of spatial variability of water table and ECa have similar spatial behavior, indicating that where the water table is deeper at places with the lowest ECa.

Siqueira, G. M.; Fontes Júnior, R. V. P.; Montenegro, A. A. A.; Barros, Y. L.; Silva, E. F. F.

2012-04-01

320

Dosimetric validation of the Acuros XB Advanced Dose Calculation algorithm: fundamental characterization in water.  

PubMed

A new algorithm, Acuros® XB Advanced Dose Calculation, has been introduced by Varian Medical Systems in the Eclipse planning system for photon dose calculation in external radiotherapy. Acuros XB is based on the solution of the linear Boltzmann transport equation (LBTE). The LBTE describes the macroscopic behaviour of radiation particles as they travel through and interact with matter. The implementation of Acuros XB in Eclipse has not been assessed; therefore, it is necessary to perform these pre-clinical validation tests to determine its accuracy. This paper summarizes the results of comparisons of Acuros XB calculations against measurements and calculations performed with a previously validated dose calculation algorithm, the Anisotropic Analytical Algorithm (AAA). The tasks addressed in this paper are limited to the fundamental characterization of Acuros XB in water for simple geometries. Validation was carried out for four different beams: 6 and 15 MV beams from a Varian Clinac 2100 iX, and 6 and 10 MV 'flattening filter free' (FFF) beams from a TrueBeam linear accelerator. The TrueBeam FFF are new beams recently introduced in clinical practice on general purpose linear accelerators and have not been previously reported on. Results indicate that Acuros XB accurately reproduces measured and calculated (with AAA) data and only small deviations were observed for all the investigated quantities. In general, the overall degree of accuracy for Acuros XB in simple geometries can be stated to be within 1% for open beams and within 2% for mechanical wedges. The basic validation of the Acuros XB algorithm was therefore considered satisfactory for both conventional photon beams as well as for FFF beams of new generation linacs such as the Varian TrueBeam. PMID:21364257

Fogliata, Antonella; Nicolini, Giorgia; Clivio, Alessandro; Vanetti, Eugenio; Mancosu, Pietro; Cozzi, Luca

2011-03-01

321

Contrasting responses of growing season ecosystem CO2 exchange to variation in temperature and water table depth in two peatlands in northern Alberta, Canada  

NASA Astrophysics Data System (ADS)

The large belowground carbon stocks in northern peatland ecosystems are potentially susceptible to release because of the expected differential responses of photosynthesis and respiration to climate change. This study compared net ecosystem CO2 exchange (NEE) measured using the eddy covariance technique at two peatland sites in northern Alberta, Canada, over three growing seasons (May-October). We observed distinct differences between the poor fen (Sphagnum moss dominated) and extreme-rich fen (Carex sedge dominated) sites for their responses of NEE to interannual variation in temperature and water table depth. The rates of growing season cumulative NEE at the poor fen were very similar among the three study years with an average (± standard deviation) of -110.1 ± 0.5 g C m-2 period-1. By contrast, the growing season cumulative NEE at the extreme-rich fen varied substantially among years (-34.5, -153.5, and -41.8 g C m-2 period-1 in 2004, 2005, and 2006, respectively), and net uptake of CO2 was lower (on average) than at the poor fen. Consistent with the eddy covariance measurements, analysis of 210Pb-dated peat cores also showed higher recent net rates of carbon accumulation in the poor fen than in the rich fen. Warm spring temperatures and sufficient water availability during the growing season resulted in the highest-magnitude ecosystem photosynthesis and NEE at the extreme-rich fen in 2005. Cool spring temperatures limited photosynthesis at the extreme-rich fen in 2004, while reduced water availability (lower water table) in 2006 constrained photosynthetic capacity relative to 2005, despite the warmer spring and summer temperatures in 2006. The combination of contrasting plant functional types and different peat water table features at our two study sites meant that the poor fen showed a reduced response of ecosystem CO2 exchange to environmental variation compared to the extreme-rich fen.

Adkinson, Angela C.; Syed, Kamran H.; Flanagan, Lawrence B.

2011-03-01

322

Effects of Low-Dose Drinking Water Arsenic on Mouse Fetal and Postnatal Growth and Development  

PubMed Central

Background Arsenic (As) exposure is a significant worldwide environmental health concern. Chronic exposure via contaminated drinking water has been associated with an increased incidence of a number of diseases, including reproductive and developmental effects. The goal of this study was to identify adverse outcomes in a mouse model of early life exposure to low-dose drinking water As (10 ppb, current U.S. EPA Maximum Contaminant Level). Methodology and Findings C57B6/J pups were exposed to 10 ppb As, via the dam in her drinking water, either in utero and/or during the postnatal period. Birth outcomes, the growth of the F1 offspring, and health of the dams were assessed by a variety of measurements. Birth outcomes including litter weight, number of pups, and gestational length were unaffected. However, exposure during the in utero and postnatal period resulted in significant growth deficits in the offspring after birth, which was principally a result of decreased nutrients in the dam's breast milk. Cross-fostering of the pups reversed the growth deficit. Arsenic exposed dams displayed altered liver and breast milk triglyceride levels and serum profiles during pregnancy and lactation. The growth deficits in the F1 offspring resolved following separation from the dam and cessation of exposure in male mice, but did not resolve in female mice up to six weeks of age. Conclusions/Significance Exposure to As at the current U.S. drinking water standard during critical windows of development induces a number of adverse health outcomes for both the dam and offspring. Such effects may contribute to the increased disease risks observed in human populations.

Kozul-Horvath, Courtney D.; Zandbergen, Fokko; Jackson, Brian P.; Enelow, Richard I.; Hamilton, Joshua W.

2012-01-01

323

An absorbed dose to water standard for HDR {sup 192}Ir brachytherapy sources based on water calorimetry: Numerical and experimental proof-of-principle  

SciTech Connect

Water calorimetry is an established technique for absorbed dose to water measurements in external beams. In this paper, the feasibility of direct absorbed dose measurements for high dose rate (HDR) iridium-192 ({sup 192}Ir) sources using water calorimetry is established. Feasibility is determined primarily by a balance between the need to obtain sufficient signal to perform a reproducible measurement, the effect of heat loss on the measured signal, and the positioning uncertainty affecting the source-detector distance. The heat conduction pattern generated in water by the Nucletron microSelectron-HDR {sup 192}Ir brachytherapy source was simulated using COMSOL MULTIPHYSICSTM software. Source heating due to radiation self-absorption was calculated using EGSnrcMP. A heat-loss correction k{sub c} was calculated as the ratio of the temperature rise under ideal conditions to temperature rise under realistic conditions. The calorimeter setup used a parallel-plate calorimeter vessel of 79 mm diameter and 1.12 mm thick front and rear glass windows located 24 mm apart. Absorbed dose was measured with two sources with nominal air kerma strengths of 38 000 and 21 000 U, at source-detector separations ranging from 24.7 to 27.6 mm and irradiation times of 36.0 to 80.0 s. The preliminary measured dose rate per unit air kerma strength of (0.502{+-}0.007) {mu}Gy/(s U) compares well with the TG-43 derived 0.505 {mu}Gy/(s U). This work shows that combined dose uncertainties of significantly less than 5% can be achieved with only modest modifications of current water calorimetry techniques and instruments. This work forms the basis of a potential future absolute dose to water standard for HDR {sup 192}Ir brachytherapy.

Sarfehnia, Arman; Stewart, Kristin; Seuntjens, Jan [Medical Physics Unit, McGill University Health Centre, Montreal, Quebec H3G 1A4 (Canada)

2007-12-15

324

An absorbed dose to water standard for HDR 192Ir brachytherapy sources based on water calorimetry: numerical and experimental proof-of-principle.  

PubMed

Water calorimetry is an established technique for absorbed dose to water measurements in external beams. In this paper, the feasibility of direct absorbed dose measurements for high dose rate (HDR) iridium-192 (192Ir) sources using water calorimetry is established. Feasibility is determined primarily by a balance between the need to obtain sufficient signal to perform a reproducible measurement, the effect of heat loss on the measured signal, and the positioning uncertainty affecting the source-detector distance. The heat conduction pattern generated in water by the Nucletron microSelectron-HDR 192Ir brachytherapy source was simulated using COMSOL MULTIPHYSICS software. Source heating due to radiation self-absorption was calculated using EGSnrcMP. A heat-loss correction k(c) was calculated as the ratio of the temperature rise under ideal conditions to temperature rise under realistic conditions. The calorimeter setup used a parallel-plate calorimeter vessel of 79 mm diameter and 1.12 mm thick front and rear glass windows located 24 mm apart. Absorbed dose was measured with two sources with nominal air kerma strengths of 38 000 and 21 000 U, at source-detector separations ranging from 24.7 to 27.6 mm and irradiation times of 36.0 to 80.0 s. The preliminary measured dose rate per unit air kerma strength of (0.502 +/- 0.007) microGy/(s U) compares well with the TG-43 derived 0.505 microGy/(s U). This work shows that combined dose uncertainties of significantly less than 5% can be achieved with only modest modifications of current water calorimetry techniques and instruments. This work forms the basis of a potential future absolute dose to water standard for HDR 192Ir brachytherapy. PMID:18196821

Sarfehnia, Arman; Stewart, Kristin; Seuntjens, Jan

2007-12-01

325

{open_quote}Optimism{close_quote} is watchword in deep water U.S. Gulf. Exploration, development in OCS frontiers over 1,500 feet threaten domestic drilling depth records  

Microsoft Academic Search

An air of optimism surrounds deep water drilling and field development activity in the U.S. Gulf of Mexico. In a marketplace that is otherwise characterized by sagging mobile rig activity and worrisome natural gas prices, millions of dollars are budgeted in 1995 for new drilling programs and development of hydrocarbon fields in domestic record-setting water depths on the outer continental

1995-01-01

326

Depth and temporal variations in water quality of the Snake River Plain aquifer in well USGS59 near the Idaho Chemical Processing Plant at the Idaho National Engineering and Environmental Laboratory  

Microsoft Academic Search

In-situ measurements of the specific conductance and temperature of ground water in the Snake River Plain aquifer were collected in observation well USGS-59 near the Idaho Chemical Processing Plant at the Idaho National Engineering and Environmental Laboratory. These parameters were monitored at various depths in the aquifer from October 1994 to August 1995. The specific conductance of ground water in

D. B. Frederick; G. S. Johnson

1997-01-01

327

Natural radionuclides and dose estimation in natural water resources from Elba protective area, Egypt.  

PubMed

The concentrations of the natural radionuclides (226)Ra, (232)Th and (40)K in 15 different water samples from Elba protective area, south-eastern desert of Egypt, have been determined using NaI(Tl) detector. Gamma ray spectrometric analysis was performed and the concentrations obtained for each of the radionuclides expressed in Bq l(-1) ranging from 1.6 to 11.1 for (226)Ra, 0.21 to 0.97 for (232)Th and 9.1 to 23 for (40)K. A reasonable correlation was found between (226)Ra, (232)Th concentrations and pH, although no general trend was observed with conductivity and total dissolved solids. The mean effective doses of 0.56 mSv y(-1) for (226)Ra, 0.065 mSv y(-1) for (232)Th and 0.04 mSv y(-1) for (40)K were estimated for the ingestion of these waters by adults. PMID:16497873

Arabi, A M El; Ahmed, N K; Din, K Salahel

2006-02-23

328

EURAMET.RI(I)-S7 comparison of alanine dosimetry systems for absorbed dose to water measurements in gamma- and x-radiation at radiotherapy levels  

NASA Astrophysics Data System (ADS)

The National Physical Laboratory (NPL), the Physikalisch-Technische Bundesanstalt (PTB) and the Laboratoire National Henri Becquerel (LNE-LNHB) are involved in the European project 'External Beam Cancer Therapy', a project of the European Metrology Research Programme. Within this project, the electron paramagnetic resonance (EPR)/alanine dosimetric method has been chosen for performing measurements in small fields such as those used in IMRT (intensity modulated radiation therapy). In this context, these three National Metrology Institutes (NMI) wished to compare the result of their alanine dosimetric systems (detector, modus operandi etc) at radiotherapy dose levels to check their consistency. This EURAMET.RI(I)-S7 comparison has been performed with the support of the Bureau International des Poids et Mesures (BIPM) which collected and distributed the results as a neutral organization, to ensure the comparison was 'blind'. Irradiations have been made under reference conditions by each laboratory in a 60Co beam and in an accelerator beam (10 MV or 12 MV) in a water phantom of 30 cm × 30 cm × 30 cm in a square field of 10 cm × 10 cm at the reference depth. Irradiations have been performed at known values of absorbed dose to water (Dw) within 10% of nominal doses of 5 Gy and 10 Gy, i.e. between 4.5 Gy and 5.5 Gy and between 9 Gy and 11 Gy, respectively. Each participant read out their dosimeters and assessed the doses using their own protocol (calibration curve, positioning device etc) as this comparison aims at comparing the complete dosimetric process. The results demonstrate the effectiveness of the EPR/alanine dosimetry systems operated by National Metrology Institutes as a method of assuring therapy level doses with the accuracy required. The maximum deviation in the ratio of measured to applied dose is less than 1%. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by EURAMET, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Garcia, Tristan; Anton, Mathias; Sharpe, Peter

2012-01-01

329

The Association of Arsenic With Redox Conditions, Depth, and Ground-Water Age in the Glacial Aquifer System of the Northern United States  

USGS Publications Warehouse

More than 800 wells in the glacial aquifer system of the Northern United States were sampled for arsenic as part of U.S. Geological Survey National Water-Quality Assessment (NAWQA) studies during 1991-2003. Elevated arsenic concentrations (greater than or equal to 10 micrograms per liter) were detected in 9 percent of samples. Elevated arsenic concentrations were associated with strongly reducing conditions. Of the samples classified as iron reducing or sulfate reducing, arsenic concentrations were elevated in 19 percent. Of the methanogenic samples, arsenic concentrations were elevated in 45 percent. In contrast, concentrations of arsenic were elevated in only 1 percent of oxic samples. Arsenic concentrations were also related to ground-water age. Elevated arsenic concentrations were detected in 34 percent of old waters (recharged before 1953) as compared to 4 percent of young waters (recharged since 1953). For samples classified as both old and methanogenic, elevated arsenic concentrations were detected in 62 percent of samples, as compared to 1 percent for samples classified as young and oxic. Arsenic concentrations were also correlated with well depth and concentrations of several chemical constituents, including (1) constituents linked to redox processes and (2) anions or oxyanions that sorb to iron oxides. Observations from the glacial aquifer system are consistent with the idea that the predominant source of arsenic is iron oxides and the predominant mechanism for releasing arsenic to the ground water is reductive desorption or reductive dissolution. Arsenic is also released from iron oxides under oxic conditions, but on a more limited basis and at lower concentrations. Logistic regression was used to investigate the relative significance of redox, ground-water age, depth, and other water-quality constituents as indicators of elevated arsenic concentrations in the glacial aquifer system. The single variable that explained the greatest amount of variation in the data was redox. Multivariate models that included a redox variable overestimated the percentage of samples with elevated arsenic concentrations because, even though elevated arsenic concentrations were associated with strongly reducing samples, not all strongly reducing samples had elevated arsenic concentrations. Arsenic concentrations and redox conditions differed among four broad areas of the glacial aquifer system. For the East, Central, and West-Central north areas, there was a trend of increasing arsenic concentrations that corresponded to an increase in reducing conditions. For the West-Central south area, arsenic concentrations in oxic samples were higher than for the other areas, possibly because of high concentrations of orthophosphate, which is linked to desorption of arsenic from iron oxides under oxic conditions. The observed differences in arsenic concentrations among broad areas of the glacial aquifer system were generally consistent with a conceptual model developed by Smedley and Kinniburg, who studied or reviewed studies of widespread arsenic contamination in Bangladesh, India, China, Vietnam, Hungary, Argentina, northern Chile and the Southwestern United States.

Thomas, Mary Ann

2007-01-01

330

210Po and 238U isotope concentrations in commercial bottled mineral water samples in Spain and their dose contribution.  

PubMed

(210)Po is a naturally occurring radionuclide, belonging to the uranium series, which is present in minute amounts in the different environmental compartments (water, soil, biota). Through its route along the trophic chain, it can be incorporated in the human body via ingestion of waters and/or food. This radionuclide is highly radiotoxic, being one of the main contributors to the committed effective dose via ingestion by the general population. In this work, the contribution of this radionuclide to the committed effective dose received by the Spanish population via consumption of bottled mineral waters is evaluated. With this end, the (210)Po activity concentrations in a total of 32 different commercial bottled mineral waters have been determined by alpha-particle spectrometry. The determined contribution is also compared with the contributions of other natural radionuclides such as (234)U and (238)U. PMID:23559586

Díaz-Francés, I; Mantero, J; Manjón, G; Díaz, J; García-Tenorio, R

2013-04-04

331

Effects of low-dose epinephrine infusion on cardiovascular and renal responses to water immersion in humans  

Microsoft Academic Search

Elevated plasma epinephrine concentrations may impair blood pressure homeostasis and renal sodium and volume excretion in response to central hypervolemia. We studied the effects of a low-dose epinephrine infusion (12 ng\\/kg\\/min) on cardiovascular and renal responses to a thermoneutral head-out water immersion in eleven healthy men.Responses to water immersion without epinephrine were characterized by significant suppression of plasma renin activity

Hans-Joachim Kruse; Reinhold Kreutz; Martina Lennarz; Axel Overlack; Klaus O. Stumpe; Rainer E. Kolloch

1996-01-01

332

ABSORBED DOSE MEASUREMENTS OF A HANDHELD 50 kVP X-RAY SOURCE IN WATER WITH THERMOLUMINESCENCE DOSEMETERS  

Microsoft Academic Search

Absorbed dose rate measurements of a 50 kVp handheld X-ray probe source in a water phantom are described. The X-ray generator is capable of currents of up to 40 lA, and is designed for cranial brachytherapy and intraoperative applications with applicators. The measurements were performed in a computer-controlled water phantom in which both the source and the detectors are mounted.

Christopher Soares; Chris Drupieski; Brian Wingert; Garey Pritchett; Vasilis Pagonis; Michelle O'Brien; Alan Sliski; Pawel Bilski; Pawel Olko

333

Application of an expert system using neural network to control the coagulant dosing in water treatment plant  

Microsoft Academic Search

The coagulation process is one of the most important stages in water treatment plant, which involves many complex physical\\u000a and chemical phenomena. Moreover, coagulant dosing rate is non-linearly correlated to raw water characteristics such as turbidity,\\u000a conductivity, PH, temperature, etc. As such, coagulation reaction is hard or even impossible to control satisfactorily by\\u000a conventional methods. Based on neural network and

Hang Zhang; Dayong Luo

2004-01-01

334

A robust method for determining the absorbed dose to water in a phantom for low-energy photon radiation  

NASA Astrophysics Data System (ADS)

The application of more and more low-energy photon radiation in brachytherapy—either in the form of low-dose-rate radioactive seeds such as Pd-103 or I-125 or in the form of miniature x-ray tubes—has induced greater interest in determining the absorbed dose to water in water in this energy range. As it seems to be hardly feasible to measure the absorbed dose with calorimetric methods in this low energy range, ionometric methods are the preferred choice. However, the determination of the absorbed dose to water in water by ionometric methods is difficult in this energy range. With decreasing energy, the relative uncertainty of the photon cross sections increases and as the mass energy transfer coefficients show a steep gradient, the spectra of the radiation field must be known precisely. In this work two ionometric methods to determine the absorbed dose to water are evaluated with respect to their sensitivity to the uncertainties of the spectra and of the atomic database. The first is the measurement of the air kerma free in air and the application of an MC-based conversion factor to the absorbed dose to water. The second is the determination of the absorbed dose to water by means of an extrapolation chamber as an integral part of a phantom. In the complementing MC-calculations, two assortments of spectra each of which is based on a separate unfolding procedure were used as well as two kinds of databases: the standard PEGS and the recently implemented NIST database of EGSnrc. Experimental results were obtained by using a parallel-plate graphite extrapolation chamber and a free-air chamber. In the case when the water kerma in a phantom is determined from the measurements of air kerma free in air, differences in the order of 10% were found, according to which the database or the kind of spectrum is used. In contrast to this, for the second method, the differences found were about 0.5%.

Schneider, T.

2011-06-01

335

Calculation of absorbed doses to water pools in severe accident sequences  

SciTech Connect

The liberation of radioactive materials into various containment locations during a severe accident creates a radiation field that may have a significant impact on the accident progression. High radiation may not only impair the functioning of important equipment, but contributes directly to a higher source term. Recent experiments indicate that radiation in air may create significant quantities of nitric acid. Irradiation of acidic iodide solutions is known to produce more volatile iodine species (chiefly I/sub 2/ and CH/sub 3/I). Hence, the high radiation fields in severe accidents could convert the less mobile iodide into more volatile forms, which could evaporate and present a considerable threat to public health and safety. The ORNL code TRENDS has been developed as a research tool to analyze the effects in severe accident sequences of such phenomena as gas phase iodine transport and radiolysis reactions. The purpose of this paper is to describe the methodology currently used for determining doses to sumps or water pools due to the decay of dissolved or suspended nuclides.

Weber, C.F.

1987-01-01

336

{open_quote}Optimism{close_quote} is watchword in deep water U.S. Gulf. Exploration, development in OCS frontiers over 1,500 feet threaten domestic drilling depth records  

SciTech Connect

An air of optimism surrounds deep water drilling and field development activity in the U.S. Gulf of Mexico. In a marketplace that is otherwise characterized by sagging mobile rig activity and worrisome natural gas prices, millions of dollars are budgeted in 1995 for new drilling programs and development of hydrocarbon fields in domestic record-setting water depths on the outer continental shelf`s deep water frontier. It`s possible that exploration and development projects in water depths greater than 1,500 feet offshore Texas and Louisiana could take priority over subsalt development in the near future. Many geologists and reservoir engineers believe deep water areas of the Gulf of Mexico have the potential to rival the largest oil field in the United States-Alaska`s Prudhoe Bay field.

Pagano, S.S. [Offshore Data Services, Inc., Houston, TX (United States)

1995-04-01

337

Generalized potentiometric surface, estimated depth to water, and estimated saturated thickness of the High Plains aquifer system, March–June 2009, Laramie County, Wyoming  

USGS Publications Warehouse

The High Plains aquifer system, commonly called the High Plains aquifer in many publications, is a nationally important water resource that underlies a 111-million-acre area (173,000 square miles) in parts of eight States including Wyoming. Through irrigation of crops with groundwater from the High Plains aquifer system, the area that overlies the aquifer system has become one of the major agricultural regions in the world. In addition, the aquifer system also serves as the primary source of drinking water for most residents of the region. The High Plains aquifer system is one of the largest aquifers or aquifer systems in the world. The High Plains aquifer system underlies an area of 8,190 square miles in southeastern Wyoming. Including Laramie County, the High Plains aquifer system is present in parts of five counties in southeastern Wyoming. The High Plains aquifer system underlies 8 percent of Wyoming, and 5 percent of the aquifer system is located within the State. Based on withdrawals for irrigation, public supply, and industrial use in 2000, the High Plains aquifer system is the most utilized source of groundwater in Wyoming. With the exception of the Laramie Mountains in western Laramie County, the High Plains aquifer system is present throughout Laramie County. In Laramie County, the High Plains aquifer system is the predominant groundwater resource for agricultural (irrigation), municipal, industrial, and domestic uses. Withdrawal of groundwater for irrigation (primarily in the eastern part of the county) is the largest use of water from the High Plains aquifer system in Laramie County and southeastern Wyoming. Continued interest in groundwater levels in the High Plains aquifer system in Laramie County prompted a study by the U.S. Geological Survey in cooperation with the Wyoming State Engineer's Office to update the potentiometric-surface map of the aquifer system in Laramie County. Groundwater levels were measured in wells completed in the High Plains aquifer system from March to June 2009. The groundwater levels were used to construct a map of the potentiometric surface of the High Plains aquifer system. In addition, depth to water and estimated saturated-thickness maps of the aquifer system were constructed using the potentiometric-surface map.

Bartos, Timothy T.; Hallberg, Laura L.

2011-01-01

338

An investigation of dose changes for therapeutic kilovoltage x-ray beams with underlying lead shielding  

SciTech Connect

Kilovoltage x-ray beams are used to treat cancer on or close to the skin surface. Many clinical cases use high atomic number materials as shielding to reduce dose to underlying healthy tissues. In this work, we have investigated the effect on both the surface dose and depth doses in a water phantom with lead shielding at depth in the phantom. The EGSnrc Monte Carlo code was used to simulate the water phantom and to calculate the surface doses and depth doses using primary x-ray beam spectra derived from an analytical model. The x-ray beams were in the energy range of 75-135 kVp with field sizes of 2, 5 and 8 cm diameter. The lead sheet was located beneath the water surface at depths ranging from 0.5-7.5 cm. The surface dose decreased as the lead was positioned closer to the water surface and as the field size was increased. The variation in surface dose as a function of x-ray beam energy was only small but the maximum reduction occurred for the 100 kVp x-ray beam. For the 8 cm diameter field with the lead at 1 cm depth and using the 100 kVp x-ray beam, the surface dose was reduced to 0.898 of the surface dose in the water phantom only. Measured surface dose changes, using a Farmer-type ionization chamber, agreed with the Monte Carlo calculated doses. Calculated depth doses in water with a lead sheet positioned below the surface showed that the dose fall-off increased as the lead was positioned closer to the water surface as compared to the depth dose in the water phantom only. Monte Carlo calculations of the total x-ray beam spectrum at the water surface showed that the total fluence decreased due to a reduction in backscatter from within the water and very little backscatter from the lead. The mean energy of the x-ray spectrum varied less than 1 keV, with the lead at 1 cm beneath the water phantom surface. As the Monte Carlo calculations showed good agreement with the measured results, this method can be used to verify surface dose changes in clinical situations where measurements are difficult. The clinical impact of the use of lead must be considered in the dose prescription for patients being treated with kilovoltage x-ray beams.

Hill, Robin; Healy, Brendan; Holloway, Lois; Baldock, Clive [Institute of Medical Physics, School of Physics, University of Sydney, Australia and Department of Radiation Oncology, Royal Prince Alfred Hospital, Sydney (Australia); Peter MacCallum Cancer Institute, Melbourne, Victoria (Australia); Cancer Therapy Centre, Liverpool Hospital, Sydney, Australia and Institute of Medical Physics, School of Physics, University of Sydney (Australia); Institute of Medical Physics, School of Physics, University of Sydney (Australia)

2007-07-15

339

An investigation of dose changes for therapeutic kilovoltage X-ray beams with underlying lead shielding.  

PubMed

Kilovoltage x-ray beams are used to treat cancer on or close to the skin surface. Many clinical cases use high atomic number materials as shielding to reduce dose to underlying healthy tissues. In this work, we have investigated the effect on both the surface dose and depth doses in a water phantom with lead shielding at depth in the phantom. The EGSnrc Monte Carlo code was used to simulate the water phantom and to calculate the surface doses and depth doses using primary x-ray beam spectra derived from an analytical model. The x-ray beams were in the energy range of 75-135 kVp with field sizes of 2, 5 and 8 cm diameter. The lead sheet was located beneath the water surface at depths ranging from 0.5-7.5 cm. The surface dose decreased as the lead was positioned closer to the water surface and as the field size was increased. The variation in surface dose as a function of x-ray beam energy was only small but the maximum reduction occurred for the 100 kVp x-ray beam. For the 8 cm diameter field with the lead at 1 cm depth and using the 100 kVp x-ray beam, the surface dose was reduced to 0.898 of the surface dose in the water phantom only. Measured surface dose changes, using a Farmer-type ionization chamber, agreed with the Monte Carlo calculated doses. Calculated depth doses in water with a lead sheet positioned below the surface showed that the dose fall-off increased as the lead was positioned closer to the water surface as compared to the depth dose in the water phantom only. Monte Carlo calculations of the total x-ray beam spectrum at the water surface showed that the total fluence decreased due to a reduction in backscatter from within the water and very little backscatter from the lead. The mean energy of the x-ray spectrum varied less than 1 keV, with the lead at 1 cm beneath the water phantom surface. As the Monte Carlo calculations showed good agreement with the measured results, this method can be used to verify surface dose changes in clinical situations where measurements are difficult. The clinical impact of the use of lead must be considered in the dose prescription for patients being treated with kilovoltage x-ray beams. PMID:17822012

Hill, Robin; Healy, Brendan; Holloway, Lois; Baldock, Clive

2007-07-01

340

Mixed layer depth (MLD) variability in the southern Bay of Biscay. Deepening of winter MLDs concurrent with generalized upper water warming trends?  

NASA Astrophysics Data System (ADS)

Mixed layer depth (MLD) variability from seasonal to decadal time scales in the Bay of Biscay is studied in this work. A hydrographic time series running since 1991 in the study area, a climatology of the upper layer vertical structure based on the topology of this temperature profile time series and a one-dimensional water column model have been used for this purpose. The prevailing factors driving MLD variability have been determined with detail, and agreement with observations is achieved. Tests carried out to investigate climatological profile skill to reproduce the upper layer temporal evolution have demonstrated its ability to simulate variability at seasonal time scales and reproduce the most conspicuous events observed. This has enabled us to carry out a reconstruction of the MLD variability for the last 60 years in the study area. Favourable sequence of intense mixing events explains interannual differences and cases of extraordinary deepening of winter mixed layer. The negative phase of the Eastern Atlantic pattern seems to determine important interannual variability through intense episodes of cooling and mixing as in winter 2005 in the Bay of Biscay. Low-frequency variability is also observed. A very striking and unexpected shallower winter MLD during the 1970s and 1980s than those observed from 1995 has been found. Simulation results support this counter-intuitive outcome of shallower winter mixed layers concurrent with generalized upper water warming trends reported on several occasions for the area. The long-term trends in MLD seem related with decadal variability in the North Atlantic Oscillation, being in phase and opposition with other deepening-shallowing cycles found from subtropical-to-subpolar areas in the North Atlantic.

Somavilla Cabrillo, Raquel; González-Pola, Cesar; Ruiz-Villarreal, Manuel; Lavín Montero, Alicia

2011-09-01

341

The dam-break of non-Boussinesq gravity currents of various fractional depth: two-layer shallow-water results  

NASA Astrophysics Data System (ADS)

The dam-break initial stage of propagation of a gravity current released from a lock of length x0 and height h0 into an ambient fluid in a channel of height H^* is considered. The system contains heavy and light fluids, of density ?H and ?L, respectively. When the Reynolds number is large, the resulting flow is governed by the parameters R= ?L/?H and H = H^*/h0. We focus attention on non-Boussinesq effects, when the parameter R is not close to 1; in this case significant differences appear between the "light" (top) current and the "heavy" (bottom) current. Using a shallow-water two-layer formulations, we obtain "exact" analytical solutions for the thickness and speed of the current and ambient by the method of characteristics. We shown that a jump (instead of a rarefaction wave) propagates into the reservoir when H < Hcrit(R), and that propagation with critical speed occurs for some combinations of H,R. The theory is applied to the full-depth lock exchange H=1 problem, and also to more general cases H >1. Comparisons to previously published results are discussed. This is a significant extension of the Boussinesq problem (which is recovered by the present solution for R = 1), which elucidates the non- Boussinesq effects during the first stage of propagation of lock-released gravity currents.

Ungarish, Marius

2010-11-01

342

Elliptic Phantom Measurements and Calculations of Neutron Spectra and Dose Distributions for exp 252 Cf and Heavy-Water-Moderated exp 252 Cf Sources.  

National Technical Information Service (NTIS)

Calculations and measurements for the dose distribution in a water-filled elliptical phantom when irradiated with neutrons of bare and heavy-water moderated Californium neutron sources are presented. The calculations were performed by a Monte-Carlo code, ...

J. Palfalvi

1983-01-01

343

Nest survival of American Coots relative to grazing, burning, and water depths [Survie au nid chez la foulque D'Am??rique en fonction du p??turage, du br??lage et de la profondeur d'eau  

USGS Publications Warehouse

Water and emergent vegetation are key features influencing nest site selection and success for many marsh-nesting waterbirds. Wetland management practices such as grazing, burning, and waterlevel manipulations directly affect these features and can influence nest survival. We used model selection and before-after-control-impact approaches to evaluate the effects of water depth and four common landmanagement practices or treatments, i.e., summer grazing, fall grazing, fall burning, and idle (no active treatment) on nest survival of American coots (Fulica americana) nesting at Grays Lake, a large montane wetland in southeast Idaho. The best model included the variables year ?? treatment, and quadratic functions of date, water depth, and nest age; height of vegetation at the nest did not improve the best model. However, results from the before-after-control-impact analysis indicate that management practices affected nest success via vegetation and involved interactions of hydrology, residual vegetation, and habitat composition. Nest success in idled fields changed little between pre- and post-treatment periods, whereas nest success declined in fields that were grazed or burned, with the most dramatic declines the year following treatments. The importance of water depth may be amplified in this wetland system because of rapid water-level withdrawal during the nesting season. Water and land-use values for area ranchers, management for nesting waterbirds, and long-term wetland function are important considerations in management of water levels and vegetation. ?? 2011 by the author(s).

Austin, J. E.; Buhl, D. A.

2011-01-01

344

Semi-3D dosimetry of high dose rate brachytherapy using a novel Gafchromic EBT3 film-array water phantom  

NASA Astrophysics Data System (ADS)

There is a need to modernise clinical brachytherapy dosimetry measurement beyond traditional point dose verification to enable appropriate quality control within 3D treatment environments. This is to keep pace with the 3D clinical and planning approaches which often include significant patient-specific optimisation away from 'standard loading patterns'. A multi-dimension measurement system is required to provide assurance of the complex 3D dose distributions, to verify equipment performance, and to enable quality audits. However, true 3D dose measurements around brachytherapy applicators are often impractical due to their complex shapes and the requirement for close measurement distances. A solution utilising an array of radiochromic film (Gafchromic EBT3) positioned within a water filled phantom is presented. A calibration function for the film has been determined over 0 to 90Gy dose range using three colour channel analysis (FilmQAPro software). Film measurements of the radial dose from a single HDR source agree with TPS and Monte Carlo calculations within 5 % up to 50 mm from the source. Film array measurements of the dose distribution around a cervix applicator agree with TPS calculations generally within 4 mm distance to agreement. The feasibility of film array measurements for semi-3D dosimetry in clinical HDR applications is demonstrated.

Palmer, A. L.; Nisbet, A.; Bradley, D. A.

2013-06-01

345

TOPICAL REVIEW: Advances in the determination of absorbed dose to water in clinical high-energy photon and electron beams using ionization chambers  

Microsoft Academic Search

During the last two decades, absorbed dose to water in clinical photon and electron beams was determined using dosimetry protocols and codes of practice based on radiation metrology standards of air kerma. It is now recommended that clinical reference dosimetry be based on standards of absorbed dose to water. Newer protocols for the dosimetry of radiotherapy beams, based on the

M. Saiful Huq; Pedro Andreo

2004-01-01

346

Safe depths for teaching children to dive.  

PubMed

Eight stages commonly used to teach diving were analysed for peak vertical velocity; vertical velocity at and following water impact and at previously recommended minimum water depths; maximum depth reached; and relationship between vertical velocity and maximum depth attained at each stage; for 13 male and 13 female children aged 6-8 years. Comparisons of mean water impact vertical velocities and maximum depths attained revealed significantly lower impact vertical velocities (F[6] = 117.39, p < 0.0001) and maximum depths (F[6] = 36.59, p < 0.0001) when performing the sit dive compared to the reference standing dive. At other stages, subjects travelled faster than the critical head velocities shown to cause adult cervical spine damage when passing through previously recommended minimum water depths. PMID:8937663

Blanksby, B A; Wearne, F K; Elliott, B C

1996-09-01

347

Application of large benthic foraminifera as a tool for interpretation of paleoclimate and water depth, in the Ziyarat Formation, Alborz, Iran  

NASA Astrophysics Data System (ADS)

The Ziyarat Formation, with a total thickness of 213 m, is a shallow warm water limestone, overlies the Fajan conglomerate and is overlain by tufaceous siltstone of the Karj Formation. The age of late Paleocene- Middle Eocene was considered for the Ziyarat Formation at the type section. From late Paleocene towards Middle Eocene, temperature has increased (Scheibner et al., 2005). This rising temperature has intensified and giving way to an unprecedented expansion of Large Benthic Foraminifera (LBF) dominating Tethyan platform during Middle Eocene (Scheibner et al., 2005). ?18O paleotemperature calculation based on heaviest oxygen isotope value of micrite and ?18Ow of Eocene seawater of 0.85 SMOW shows that temperature was around 39?C in the study area. In response to continued global warming during Paleocene-Eocene Termal Maximum (PETM), some organisms (such as corals) has been declined, while at the same time, L.B.F. were increasingly favored as dominant carbonate producing organisms in oligotrophic environment (Scheibner et al., 2008). For the even warmer period of PTEM a transient rise in sea-surface temperature of 4-5?C in low latitudes and 8 to 10? C in high latitudes has been proposed based on Mg/Ca ratios of planktic foraminifera (Zachos et al., 2003; Tripati and Elderfield, 2004). Thus, L.B.F was able to exploit their niche as evidenced by their increase in size, species diversity and their overwhelming abundance. In the Ziyarat Formation, 11 microfacies were recognized from the shallower to deeper part of the platform. The lack of evidence of resedimentation, e.g. turbidite, related to steep slop, and absence of reefal facies and widespread tidal flat deposits indicate that the Ziyarat Formation was deposited in a homocline carbonate ramp environment. The evaporite facies, dolomicrite, intraclast ooid packstone to grainstone, Miliolid wackestone, and Alveolina nummulite packstone belong to inner ramp sub-environment; middle ramp microfacies composed of Nummulite packstone, red algae nummulite packstone, Discocyclina nummulite wackestone, and Nummulite discocyclina wackestone to packstone; and outer ramp microfacies consist of benthic foraminifera packstone and radiolar sponge spicule wackestone. The ramp model proposed here for the Ziyarat Formation represent an example of a foraminifera dominated ramp system. The Paleogene was a time of particular abundance and radiation of miliolid and larger hyaline foraminifera and, especially during the Eocene they occurred in rock-forming quantities. Among L.B.F typical of Early Cenozoic carbonate platforms, Nummulites occupied a broad range of open marine environments on both ramps and shelves, and was generally absent from more restricted waters. Assilina and discocyclina in relatively deep water environments, while smaller lenticular Nummulites occur in shallower, inner ramp/shelf settings, often co-existing with Alveolina. Nummulites in the Ziyarat Formation showing variation in test shape, along the paleoenvironmental gradient. Nummulites from inner ramp have robust ovate shape with thick walls, while by increasing water depth, lower temperature, decreasing light levels and water energy, the test shape becomes flatter and elongate.

Khatibi Mehr, M.; Adabi, M. H.

2009-04-01

348

Autonomous depth adjustment for underwater sensor networks  

Microsoft Academic Search

To fully understand the ocean environment requires sensing the full water column. Utilizing a depth adjustment system on an underwater sensor network provides this while also improving global sensing and communications. This paper presents a depth adjustment system for waters of up to 50m deep that connects to the AquaNode sensor network. We performed experiments characterizing the system and demonstrating

Carrick Detweiler; Marek Doniec; Iuliu Vasilescu; Elizabeth Basha; Daniela Rus

2010-01-01

349

Dose of UV light required to inactivate Listeria monocytogenes in distilled water, fresh brine, and spent brine.  

PubMed

The purpose of this research was to establish the dose of UV light (253.7 nm) needed to inactivate Listeria monocytogenes in distilled water, fresh brine (9% NaCl), spent brine, and diluted (5, 35, and 55%) spent brine, using uridine as a chemical actinometer. Strains N1-227 (isolated from hot dog batter), N3-031 (isolated from turkey franks), and R2-499 (isolated from meat) were mixed in equal proportions and suspended in each solution prepared so as to contain 10(-4) M uridine. Samples were irradiated in sterile quartz cells for 0, 5, 10, 15, 20, 25, or 30 min. Inactivation was evaluated by serially diluting samples in 0.1% peptone, by surface plating in duplicate onto modified Oxford agar and Trypticase soy agar with yeast extract, and by enrichment in brain heart infusion broth, followed by incubation at 37 degrees C for 24 to 48 h. For dose measurements, the absorbance (262 nm) was measured before and after irradiation. Differences were observed in population estimates depending on the solution (P < or = 0.05). Reductions were as follows from greatest to least: water > fresh brine > 5% spent brine > 35% spent brine > 55% spent brine > undiluted spent brine. UV light did not significantly reduce populations suspended in spent brine solutions. L. monocytogenes decreased to below the detection limit (1 log CFU/ml) at doses greater than 33.2 mJ/cm(2) in water and at doses greater than 10.3 mJ/cm(2) in fresh brine. Knowledge of UV dosing required to control L. monocytogenes in brines similar to those used for ready-to-eat meat processing will aid manufacturers in establishing appropriate food safety interventions for these products. PMID:19833038

McKinney, Julie; Williams, Robert C; Boardman, Gregory D; Eifert, Joseph D; Sumner, Susan S

2009-10-01

350

High Altitude Diving Depths  

Microsoft Academic Search

In order to make any sea level dive table usable during high altitude diving, a new conversion factor is created. We introduce the standardized equivalent sea depth (SESD), which allows conversion of the actual lake diving depth (ALDD) to an equivalent sea dive depth.SESD is defined as the sea depth in meters or feet for a standardized sea dive, equivalent

Poul-Erik Paulev; Gustavo Zubieta-Calleja

2007-01-01

351

A critical review of measures to reduce radioactive doses from drinking water and consumption of freshwater foodstuffs.  

PubMed

Following a radioactive fallout event, there are a number of possible intervention measures to reduce radioactive doses to the public via the surface water pathway. We have critically reviewed the options available to decision-makers in the event of radioactive contamination of surface waters. We believe that the most effective and viable measures to reduce radioactivity in drinking water are those which operate at the water treatment and distribution stage. Intervention measures to reduce concentrations of radioactivity in rivers and reservoirs are expected to be much less viable and efficient at reducing doses via the drinking water pathway. Bans on consumption of freshwater fish can be effective, but there are few viable measures to reduce radioactivity in fish prior to the preparation stage. Lake liming and biomanipulation have been found to be ineffective for radiocaesium, although the addition of potassium to lakewaters appears promising in some situations. Lake liming may be effective in reducing radiostrontium in fish, though this has not, to our knowledge, been tested. De-boning fish contaminated by strontium is probably the most effective food preparation measure, but salting and freezing can also reduce radiocaesium concentrations in fish. The provision of accurate information to the public is highlighted as a key element of countermeasure implementation. PMID:11446114

Smith, J T; Voitsekhovitch, O V; Håkanson, L; Hilton, J

2001-01-01

352

Comparison of the standards for absorbed dose to water of the PTB, Germany and the BIPM for 60Co ? rays  

Microsoft Academic Search

A comparison of the standards for absorbed dose to water of the Physikalisch-Technische Bundesanstalt (PTB), Germany and of the Bureau International des Poids et Mesures (BIPM) has been made in 60Co gamma radiation under the auspices of the key comparison BIPM.RI(I)-K4. The comparison result, based on the calibration coefficients for three transfer standards and expressed as a ratio of the

C. Kessler; P. J. Allisy; D. T. Burns; A. Krauss; R.-P. Kapsch

2006-01-01

353

Heat transport by material-dependent heating during absorption of radiation in the water absorbed dose calorimeter  

Microsoft Academic Search

Water absorbed dose calorimeters have been developed for the application as PTB standards for the dosimetry in radiation therapy with photon and electron radiation. Different detector types for various applications are available. In this paper, heat conduction effects of “sealed” detectors are investigated, caused by the material-dependent temperature rise during the absorption of 60Co-?-radiation in the detector walls and in

A. Krauss; M. Roos

1999-01-01

354

The application of powdered activated carbon for mib and geosmin removal: predicting pac doses in four raw waters  

Microsoft Academic Search

Blooms of blue–green algae in reservoirs often produce the musty-earthy taste and odour algal metabolites 2-methylisoborneol (MIB) and geosmin. MIB and geosmin are not removed by conventional water treatment and their presence in the distribution system, even at low ngL?1 levels, can result in consumer complaints. Powdered activated carbon (PAC) can effectively remove MIB and geosmin when the correct dose

David Cook; Gayle Newcombe; Pascale Sztajnbok

2001-01-01

355

Influence of tap water quality and household water use activities on indoor air and internal dose levels of trihalomethanes.  

PubMed

Individual exposure to trihalomethanes (THMs) in tap water can occur through ingestion, inhalation, or dermal exposure. Studies indicate that activities associated with inhaled or dermal exposure routes result in a greater increase in blood THM concentration than does ingestion. We measured blood and exhaled air concentrations of THM as biomarkers of exposure to participants conducting 14 common household water use activities, including ingestion of hot and cold tap water beverages, showering, clothes washing, hand washing, bathing, dish washing, and indirect shower exposure. We conducted our study at a single residence in each of two water utility service areas, one with relatively high and the other low total THM in the residence tap water. To maintain a consistent exposure environment for seven participants, we controlled water use activities, exposure time, air exchange, water flow and temperature, and nonstudy THM sources to the indoor air. We collected reference samples for water supply and air (pre-water use activity), as well as tap water and ambient air samples. We collected blood samples before and after each activity and exhaled breath samples at baseline and post-activity. All hot water use activities yielded a 2-fold increase in blood or breath THM concentrations for at least one individual. The greatest observed increase in blood and exhaled breath THM concentration in any participant was due to showering (direct and indirect), bathing, and hand dishwashing. Average increase in blood THM concentration ranged from 57 to 358 pg/mL due to these activities. More research is needed to determine whether acute and frequent exposures to THM at these concentrations have public health implications. Further research is also needed in designing epidemiologic studies that minimize data collection burden yet maximize accuracy in classification of dermal and inhalation THM exposure during hot water use activities. PMID:16002374

Nuckols, John R; Ashley, David L; Lyu, Christopher; Gordon, Sydney M; Hinckley, Alison F; Singer, Philip

2005-07-01

356

Estimation of mean annual effective dose through radon concentration in the water and indoor air of Islamabad and Murree.  

PubMed

Different samples of water, indoor air and soil gas have been collected from Islamabad (33 degrees 38'N, 73 degrees 09'E, altitude of 1760 ft.), the capital of Pakistan and Murree (33 degrees 53'N, 73 degrees 23'E, altitude of 7323 ft.), lying on a geological fault line and are analysed for the estimation of mean effective dose through radon concentrations by using RAD-7, a solid state alpha-detector. The variation of radon concentration in water, indoor air and soil gas in Islamabad region ranges from 25.90-158.40 kBq m(-3), 43.26-97.04 Bq m(-3) and 17.34-72.52 kBq m(-3), having mean values 88.63 kBq m(-3), 70.67 Bq m(-3) and 45.08 kBq m(-3)(,) respectively. It ranges from 1.64-10.20 kBq m(-3), 18.48-42.08 Bq m(-3) and 0.61-3.89 kBq m(-3) with mean values 4.38 kBq m(-3), 28.63 Bq m(-3) and 1.70 kBq m(-3)(,) respectively in Murree and its surroundings. The total mean annual effective doses from water and indoor air of Islamabad and Murree regions are 2.023 and 0.733 mSv a(-1), respectively. These doses are within the recommended limits of the world organisations. PMID:20511405

Ali, N; Khan, E U; Akhter, P; Khan, F; Waheed, A

2010-05-28

357

Solar disinfection of drinking water (SODIS): an investigation of the effect of UV-A dose on inactivation efficiency.  

PubMed

The effect of solar UV-A irradiance and solar UV-A dose on the inactivation of Escherichia coli K-12 using solar disinfection (SODIS) was studied. E. coli K-12 was seeded in natural well-water contained in borosilicate glass tubes and exposed to sunlight at different irradiances and doses of solar UV radiation. In addition, E. coli K-12 was also inoculated into poly(ethylene) terephthalate (PET) bottles and in a continuous flow system (10 L min(-1)) to determine the effect of an interrupted and uninterrupted solar dose on inactivation. Results showed that inactivation from approximately 10(6) CFU mL(-1) to below the detection level (4 CFU/mL) for E. coli K-12, is a function of the total uninterrupted dose delivered to the bacteria and that the minimum dose should be >108 kJ m(-2) for the conditions described (spectral range of 0.295-0.385 microm). For complete inactivation to below the limit of detection, this dose needs to be received regardless of the incident solar UV intensity and needs to be delivered in a continuous and uninterrupted manner. This is illustrated by a continuous flow system in which bacteria were not fully inactivated (residual viable concentration approximately 10(2) CFU/mL) even after 5 h of exposure to strong sunlight and a cumulative dose of >108 kJ m(-2). This has serious implications for attempts to scale-up solar disinfection through the use of re-circulatory continuous flow reactors. PMID:19424529

Ubomba-Jaswa, Eunice; Navntoft, Christian; Polo-López, M Inmaculada; Fernandez-Ibáñez, Pilar; McGuigan, Kevin G

2009-01-19

358

Development of an optimum control software package for coagulant dosing process in water purification system  

Microsoft Academic Search

In the water purification plant, raw water is promptly purified by injection of chemicals. The amount of chemicals is directly related to water qualities such as turbidity, temperature, pH and alkalinity. However, the process of chemical reaction to the turbidity is not yet to be clarified. Since the process of coagulant dosage has no feedback signal, the amount of chemicals

Eui-Suck Nahm; Su-Bum Lee; Kwang-Bang Woo; Bong-Kuk Lee; Sang-Keun Shin

1996-01-01

359

Global patterns of groundwater table depth.  

PubMed

Shallow groundwater affects terrestrial ecosystems by sustaining river base-flow and root-zone soil water in the absence of rain, but little is known about the global patterns of water table depth and where it provides vital support for land ecosystems. We present global observations of water table depth compiled from government archives and literature, and fill in data gaps and infer patterns and processes using a groundwater model forced by modern climate, terrain, and sea level. Patterns in water table depth explain patterns in wetlands at the global scale and vegetation gradients at regional and local scales. Overall, shallow groundwater influences 22 to 32% of global land area, including ~15% as groundwater-fed surface water features and 7 to 17% with the water table or its capillary fringe within plant rooting depths. PMID:23430651

Fan, Y; Li, H; Miguez-Macho, G

2013-02-22

360

[Method of ecological risk assessment for risk pollutants under short-term and high dose exposure in water pollution accident].  

PubMed

In recent years, water pollution accidents resulting in acute aquatic ecological risk and security issues become a research focus. However, in our country, the surface water quality standards and drinking water health standards were used to determine the safety of waters or not in pollution incidents due to lacking safety effect threshold or risk value for protection of aquatic life. In foreign countries, although predicted no effect concentration (PNEC) or risk value (R) of pollutants were provided for protection of aquatic organisms, the PNECs or risk values were derived based on long-term exposure toxicity data NOECs (no observed effect concentrations) and lack of short-term exposure risk or threshold values. For the short-term and high dose exposure in pollution incident, ecological risk assessment methods were discussed according to the procedures of the conventional ecological risk assessment and the water quality criteria establishment of the U.S. EPA for the protection of aquatic organisms in short-term exposure, and had a case study. At the same time, we provide some suggestions for the establishment of ecological risk assessment system in water pollution incidents. PMID:22295619

Lei, Bing-Li; Sun, Yan-Feng; Liu, Qian; Yu, Zhi-Qiang; Zeng, Xiang-Ying

2011-11-01

361

Particle size distribution and inhalation dose of shower water under selected operating conditions.  

PubMed

Showering produces respirable droplets that may serve to deposit pollutants such as trihalomethane decontamination products, heavy metals, inorganic salts, microbes, or cyanoacterial toxins within the respiratory tract. The extent and importance of this route of indoor exposure depend on the physical characteristics of the aerosol as well as the pollutant profile of the source water. The purpose of this study was to characterize shower-generated aerosols as a function of water flow rate, temperature, and bathroom location. Aerosols were generated within a shower stall containing a mannequin to simulate the presence of a human. Using hot water, the mass median diameter (MMD) of the droplets inside the shower and in the bathroom were 6.3-7.5 um and 5.2-6 microm, respectively. Size was independent of water flow rate. The particle concentration inside the shower ranged from 5 to 14 mg/m3. Aerosols generated using cold water were smaller (2.5-3.1 microm) and concentrations were lower (0.02-0.1 mg/m3) inside the shower stall. No aerosols were detected in the bathroom area when cold water was used. The International Commission on Radiological Protection model was used to estimate water deposition in the respiratory tract. For hot water, total deposition ranged from 11 to 14 mg, depending on water flow rate, with approximately 50% of this deposited in the extrathoracic region during assumed mouth breathing, and greater than 86% when nose breathing was assumed. Alveolar deposition was 6-10% and 0.9% assuming oral and nasal breathing, respectively. The consequences deposition of shower water droplets will depend on the nature and extent of any pollutants in the source water. PMID:17365038

Zhou, Yue; Benson, Janet M; Irvin, Clinton; Irshad, Hammad; Cheng, Yung-Sung

2007-04-01

362

Particle Size Distribution and Inhalation Dose of Shower Water Under Selected Operating Conditions  

PubMed Central

Showering produces respirable droplets that may serve to deposit pollutants such as trihalomethane decontamination products, heavy metals, inorganic salts, microbes, or cyanoacterial toxins within the respiratory tract. The extent and importance of this route of indoor exposure depend on the physical characteristics of the aerosol as well as the pollutant profile of the source water. The purpose of this study was to characterize shower-generated aerosols as a function of water flow rate, temperature, and bathroom location. Aerosols were generated within a shower stall containing a mannequin to simulate the presence of a human. Using hot water, the mass median diameter (MMD) of the droplets inside the shower and in the bathroom were 6.3–7.5 um and 5.2–6 µm, respectively. Size was independent of water flow rate. The particle concentration inside the shower ranged from 5 to 14 mg/m3. Aerosols generated using cold water were smaller (2.5–3.1 µm) and concentrations were lower (0.02–0.1 mg/m3) inside the shower stall. No aerosols were detected in the bathroom area when cold water was used. The International Commission on Radiological Protection model was used to estimate water deposition in the respiratory tract. For hot water, total deposition ranged from 11 to 14 mg, depending on water flow rate, with approximately 50% of this deposited in the extrathoracic region during assumed mouth breathing, and greater than 86% when nose breathing was assumed. Alveolar deposition was 6–10% and 0.9% assuming oral and nasal breathing, respectively. The consequences deposition of shower water droplets will depend on the nature and extent of any pollutants in the source water.

Zhou, Yue; Benson, Janet M.; Irvin, Clinton; Irshad, Hammad; Cheng, Yung-Sung

2010-01-01

363

Anomalous Stereoscopic Depth Perception.  

National Technical Information Service (NTIS)

Normal or complete stereoscopic depth perception is based upon at least two and probably three mechanisms. These mechanisms may be isolated by studying depth judgments made by stereoanomalous individuals who are unable to discriminate disparities over wid...

W. Richards

1970-01-01

364

Dose rate estimates from irradiated light-water-reactor fuel assemblies in air  

Microsoft Academic Search

It is generally considered that irradiated spent fuel is so radioactive (self-protecting) that it can only be moved and processed with specialized equipment and facilities. However, a small, possibly subnational, group acting in secret with no concern for the environment (other than the reduction of signatures) and willing to incur substantial but not lethal radiation doses, could obtain plutonium by

W. R. Lloyd; M. K. Sheaffer; W. G. Sutcliffe

1994-01-01

365

Great Lakes waters: radiation dose commitments, potential health effects, and cost-benefit considerations  

Microsoft Academic Search

In 1972, a Great Lakes Water Quality Agreement was signed by the United States and Canadian Governments. It was stipulated that the operation and effectiveness of the agreement were to be reviewed comprehensively in 1977. Aspects of the agreement concern nondegradation of Great Lakes waters and maintenance of levels of radioactivity or other potential pollutants at levels considered as low

1977-01-01

366

Depth Adaptive Video Stitching  

Microsoft Academic Search

This paper proposes a novel approach to stitch videos fast and with high quality. In general, scene depth is frequently varying for dynamic video content. For example, moving foreground objects will move closely or far from a camera. The scene depth will be changing according to changed scene content. Therefore, accurate projection transform estimation corresponding to current scene depth is

Wei Zeng; Hongming Zhang

2009-01-01

367

Automated Source Depth Estimation  

Microsoft Academic Search

Source depth estimation is a key process in the discrimination of earthquakes and explosions for nuclear treaty monitoring. The lack of observable depth phases does not mean an event occurred at or near the surface. Shallow events can have closely spaced depth phases that are imperceptible to human analysts and regional events are often complicated by the simultaneous arrival of

W. N. Junek; J. R. Nieves; R. C. Kemerait; M. T. Woods; J. P. Creasey

2007-01-01

368

A decadal regional and global trend analysis of the aerosol optical depth using a data-assimilation grade over-water MODIS and Level 2 MISR aerosol products  

Microsoft Academic Search

Using the ten-year (2000-2009) DA quality Terra MODIS and MISR aerosol products, as well as 7 years of Aqua MODIS, we studied both regional and global aerosol trends over oceans. This included both natural and data assimilation grade versions of the products. Contrary to some of the previous studies that showed a decreasing trend in aerosol optical depth (AOD) over

J. Zhang; J. S. Reid

2010-01-01

369

Depth and temporal variations in water quality of the Snake River Plain aquifer in well USGS-59 near the Idaho Chemical Processing Plant at the Idaho National Engineering and Environmental Laboratory  

SciTech Connect

In-situ measurements of the specific conductance and temperature of ground water in the Snake River Plain aquifer were collected in observation well USGS-59 near the Idaho Chemical Processing Plant at the Idaho National Engineering and Environmental Laboratory. These parameters were monitored at various depths in the aquifer from October 1994 to August 1995. The specific conductance of ground water in well USGS-59, as measured in the borehole, ranged from about 450 to 900 {micro}S/cm at standard temperature (25 C). The pumping cycle of the production wells at the Idaho Chemical Processing Plant causes changes in borehole circulation patterns, and as a result the specific conductance of ground water at some depths in the well varies by up to 50% over a period of about 14 hours. However, these variations were not observed at all depths, or during each pumping cycle. The temperature of ground water in the well was typically between 12.8 and 13.8 C. The results of this study indicate that temporal variations in specific conductance of the ground water at this location are caused by an external stress on the aquifer--pumping of a production well approximately 4,000 feet away. These variations are believed to result from vertical stratification of water quality in the aquifer and a subsequent change in intrawell flow related to pumping. When sampling techniques that do not induce a stress on the aquifer (i.e., thief sampling) are used, knowledge of external stresses on the system at the time of sampling may aid in the interpretation of geochemical data.

Frederick, D.B. [Idaho INEL Oversight Program, Boise, ID (United States); Johnson, G.S. [Univ. of Idaho, Moscow, ID (United States). Dept. of Geology and Geological Engineering

1997-03-01

370

Jeju ground water containing vanadium induced immune activation on splenocytes of low dose ?-rays-irradiated mice.  

PubMed

Vanadium, an essential micronutrient, has been implicated in controlling diabetes and carcinogenesis and in impeding reactive oxygen species (ROS) generation. ?-ray irradiation triggers DNA damage by inducing ROS production and causes diminution in radiosensitive immunocytes. In this study, we elucidate the immune activation capacities of Jeju water containing vanadium on immunosuppression caused by ?-ray irradiation, and identify its mechanism using various low doses of NaVO(3). We examined the intracellular ROS generation, DNA damage, cell proliferation, population of splenocytes, and cytokine/antibody profiles in irradiated mice drinking Jeju water for 180 days and in non-irradiated and in irradiated splenocytes both of which were treated with NaVO(3). Both Jeju water and 0.245 ?M NaVO(3) attenuated the intracellular ROS generation and DNA damage in splenocytes against ?-ray irradiation. Splenocytes were significantly proliferated by the long-term intake of Jeju water and by 0.245 ?M NaVO(3) treatment, and the expansion of B cells accounted for the increased number of splenocytes. Also, 0.245 ?M NaVO(3) treatment showed the potency to amplify the production of IFN-? and total IgG in irradiated splenocytes, which correlated with the expansion of B cells. Collectively, Jeju water containing vanadium possesses the immune activation property against damages caused by ?-irradiation. PMID:22446809

Ha, Danbee; Joo, Haejin; Ahn, Ginnae; Kim, Min Ju; Bing, So Jin; An, Subin; Kim, Hyunki; Kang, Kyung-goo; Lim, Yoon-Kyu; Jee, Youngheun

2012-03-17

371

Hyperthermia following MDMA administration in rats: Effects of ambient temperature, water consumption, and chronic dosing  

Microsoft Academic Search

In two experiments it was found that the hyperthermia which follows MDMA (“Ecstasy”) results from an interaction of direct pharmacological effect of the drug and the prevailing environmental conditions in which it is administered. In Experiment 1, rats given fixed doses of either 2..5, 5.0 or 7.5 mg\\/kg MDMA or saline were injected on different days at ambient temperatures (Ta's)

Richard I. Dafters

1995-01-01

372

Evaluation of factors to convert absorbed dose calibrations from graphite to water for the NPL high-energy photon calibration service  

Microsoft Academic Search

The National Physical Laboratory (NPL) provides a high-energy photon calibration service using 4-19 MV x-rays and 60Co gamma-radiation for secondary standard dosemeters in terms of absorbed dose to water. The primary standard used for this service is a graphite calorimeter and so absorbed dose calibrations must be converted from graphite to water. The conversion factors currently in use were determined

R. F. Nutbrown; S. Duane; D. R. Shipley; R. A. S. Thomas

2002-01-01

373

Absorption and elimination of trivalent and hexavalent chromium in humans following ingestion of a bolus dose in drinking water.  

PubMed

These studies investigate the magnitude and valence state of chromium absorbed following plausible drinking water exposures to chromium(VI). Four adult male volunteers ingested a single dose of 5 mg Cr (in 0.5 liters deionized water) in three choromium mixtures: (1) Cr(III) chloride (CrCl3), (2) potassium dichromate reduced with orange juice (cr(III)-OJ); and (3) potassium dichromate [Cr(VI)]. Blood and urine chromium levels were followed for 1-3 days prior to and up to 12 days after ingestion. The three mixtures showed quite different pharmacokinetic patterns. CrCl3 was poorly absorbed (estimated 0.13% bioavailability) and rapidly eliminated in urine (excretion half-life, approximately 10 hr), whereas Cr(III)-OJ was absorbed more efficiently (0.60% bioavailability) but more slowly (half-life, approximately 17 hr), and Cr(VI) had the highest bioavailability (6.9%) and the longest half-life (approximately 39 hr). All three chromium mixtures caused temporary elevations in red blood cell (RBC) and plasma chromium concentrations, but the magnitude and duration of elevation showed a clear trend (Cr(VI) > Cr(III)-OJ > CrCl3). The data suggest that nearly all the ingested Cr(VI) was reduced to Cr(III) before entering the bloodstream based on comparison to RBC and plasma chromium patterns in animals exposed to high doses of Cr(VI). These findings support our prior work which suggests that water-soluble organic complexes of Cr(III) formed during the reduction of Cr(VI) in vivo explain the patterns of blood uptake and urinary excretion in humans at drinking water concentrations of 10 mg/liter or less. PMID:8917687

Kerger, B D; Paustenbach, D J; Corbett, G E; Finley, B L

1996-11-01

374

Radiological dose assessment for the dismantlement and decommissioning option for the Heavy Water Components Test Reactor facility at the Savannah River Site, Aiken, South Carolina  

SciTech Connect

Potential maximum radiation dose rates for a 10,000-year horizon were calculated for the dismantlement and decommissioning option for the Heavy Water Components Test Reactor facility at the Savannah River Site. The residual radioactive material guidelines (RESRAD) computer code was used. The study will help determine if it is acceptable (in terms of DOE radiation dose limits) for activated and contaminated concrete to remain in the facility, along with embedded radioactive piping and radioactive equipment. Four cases were developed to evaluate potential doses; the cases vary with regard to the definitions of the sources. Case A considers the dose from the reactor biological shield; case B considers the dose from contaminated concrete rubble; case C considers the dose from contaminated concrete rubble, the reactor biological shield, and installed equipment; and case D considers the dose from contaminated cuttings brought to the surface following the perforation of a well through the contaminated zone in case C. Site-specific parameter values were used to estimate the radiation doses. The results indicate that neither the DOE dose limit of 100 mrem/yr nor the 15-mrem/yr dose constraint would be exceeded for any of the cases. The potential maximum dose rates for cases A, B, C, and D are 0.000028, 0.015, 0.018, and 0.17 mrem/yr, respectively. The drinking water pathway is the dominant contributor to the doses in cases A through C, and the external gamma pathway is the dominant contributor in case D. Carbon-14, uranium-234, uranium-238, and americium-241 are the principal radionuclides contributing to the doses in cases A through C. Cobalt-60, europium-152, and barium-133 are the important radionuclides in case D. A sensitivity analysis was performed to determine which parameters have the greatest impact on the estimated doses. 9 refs., 11 figs., 3 tabs.

Faillace, E.R.; Kamboj, S.; Yu, C.; Chen, S.Y.

1997-10-01

375

Depth of root symbiont occurrence in soil  

Microsoft Academic Search

The woody legume Prosopis glandulosa (mesquite) growing in the California Sonoran Desert develops functional root symbiotic associations (N2-fixing nodules, vesicular-arbuscular mycorrhizal fungi) at depths greater than 4 m in moist soil above a seasonally stable water table. Population densities of symbiotic microorganisms are substantially greater at depth than near the surface. Inferences of plant symbiotic dependence based upon examination of

R. A. Virginia; M. B. Jenkins; W. M. Jarrell

1986-01-01

376

Age-dependent dose and health risk due to intake of uranium in drinking water from Jaduguda, India.  

PubMed

Uranium is a heavy metal that is not only radiologically harmful but also a well-known nephrotoxic element. In this study, occurrence of uranium in drinking water samples from locations near the uranium mining site at Jaduguda, India, was studied by Laser-induced fluorimetry. Uranium concentrations range from 0.03 ± 0.01 to 11.6 ± 1.3 µg l(-l), being well within the US Environmental Protection Agency drinking water limit of 30 ?g l(-1). The ingestion dose due to the presence of uranium in drinking water for various age groups varies from 0.03 to 28.3 ?Sv y(-1). The excess lifetime cancer risk varies from 4.3×10(-8) to 1.7×10(-5) with an average value of 4.8×10(-6), much less than the acceptable excess lifetime cancer risk of 10(-3) for radiological risk. The chemical risk (hazard quotient) has an average value of 0.15 indicating that the water is safe for drinking. PMID:23525912

Patra, A C; Mohapatra, S; Sahoo, S K; Lenka, P; Dubey, J S; Tripathi, R M; Puranik, V D

2013-03-22

377

Use of the reference dose in risk characterization of drinking water contaminants  

Microsoft Academic Search

Regulatory decisions should be made in the most expert and informed way since they are precipitated by real and perceived threats to public health, under the glare of public scrutiny. The development of environmental regulations require a three?step paradigm, collectively called risk analysis. This paper will address the risk assessment practices required under the Safe Drinking Water Act (SDWA) Amendments

Edward V. Ohanian

1995-01-01

378

Comparing pencil-beam generated and Monte Carlo generated dose-to-water and dose-to-tissue distributions for proton therapy patients  

Microsoft Academic Search

Proton Monte Carlo dose calculation based on the Monte Carlo toolkit Geant4 is implemented at Massachusetts General Hospital.\\u000a This paper summarizes the clinical implementation of the code, i.e. modeling of the treatment head, modeling of the patient,\\u000a dose scoring, absolute dosimetry, and the Geant4 physics settings for proton therapy.\\u000a \\u000a We present comparisons between dose distributions calculated by the pencil beam

H. Paganetti

379

Preliminary Maps of (1) Pleistocene Alluvial Surface, (2) Depth to Historical High Ground Water, and (3) Thickness of Holocene Alluvium - and their use in Liquefaction Hazard Mapping, Santa Clara Valley and the East San Francisco Bay Plain, California  

NASA Astrophysics Data System (ADS)

The California Geological Survey (CGS) has prepared a series of Seismic Hazard Zone Maps for a portion of the southern San Francisco Bay of Northern California. Twelve 7.5-minute quadrangles (1:24,000 scale) have been released identifying areas that may be susceptible to earthquake-induced liquefaction or landsliding. Cities and Counties use these maps to identify areas requiring site-specific investigations prior to permitting development. "Liquefaction Zones of Required Investigation" are the result of the three-dimensional integration of geotechnical and geological data. For areas where we've obtained sufficient geotechnical data, liquefaction zone boundaries are sometimes delineated by comparing the depth to denser material, primarily late Pleistocene alluvial fan deposits (Qpf), and the depth to ground water. Areas are excluded from the zones of required investigation where lower density, younger (Holocene) material is above historical high ground-water levels (i.e. unsaturated) and only Pleistocene material is saturated. We have contoured the elevation of the top of the Pleistocene alluvial surface using methods similar to those of Helley (1990), for portions of the twelve 7.5-minute quadrangles that cover much of the northern Santa Clara Valley and the East San Francisco Bay Plain. Approximately 1700 geotechnical borehole logs were collected, analyzed, entered into a geotechnical GIS database, and interpreted to identify the top of the Pleistocene alluvial surface and evaluate the susceptibility of deposits to liquefaction. Physical and geotechnical characteristics evaluated to identify the Pleistocene/Holocene transition include: color; mottling; grain size; gradation; penetration resistance; unit thickness; dry density; moisture content; Unified Soil Classification; presence of organic material or caliche; lateral continuity; etc. We have also compiled a historical-high ground-water map by plotting depths to first-encountered unconfined ground water. These data layers are the basis for our evaluation of liquefaction hazard.

Clahan, K. B.; Mattison, M. E.; Rosinski, A. M.; Bott, J. D.; Knudsen, K. L.

2002-12-01

380

Preliminary map of the conterminous United States showing depth to and quality of shallowest ground water containing more than 1,000 parts per million dissolved solids  

USGS Publications Warehouse

In this atlas, mineralized ground water is viewed presently as a source of water in some areas, but in much of the country as a source for future development. Mineralized water underlies large areas of the country, and its importance will grow as present supplies of fresh water are appropriated and developed. The potential uses fall in two main categories: (1) direct use in industrial processes, such as cooling, or for irrigation, where a moderate mineral content may not be a disadvantage; and (2) use after demineralization or dilution to whatever degree may be required by the intended user. It is clearly more efficient to produce and process water of moderate mineralization at points of use, where available in adequate amounts, than it is to process ocean water and pump it many miles from the sea. The Geological Survey, as a part of its responsibility to describe the water resources of the United States, has surveyed the known occurrences of mineralized ground water in the conterminous United States. The results are shown on the maps (sheets 1 and 2). This atlas was prepared to meet needs for information on the distribution and availability of mineralized water as expressed by Government agencies, private industries, and consultants. The maps are one step in providing an inventory of mineralized water of the Nation and will serve as a planning guide for further investigations and for development. They are necessarily generalized in many places owing to the complexity of the occurrence of the mineralized water, lack of detailed information for parts of the nation, and the difficulties inherent in attempts to put threedimensional information on maps.

Feth, John Henry Frederick

1965-01-01

381

Olestra dose response on fat-soluble and water-soluble nutrients in humans.  

PubMed

Ninety normal healthy adults were given 0, 8, 20 or 32 g/d olestra for 8 wk as part of a diet that provided 1 +/- 0.2 of the recommended dietary allowance (RDA) of vitamins A, D, E and K, folate zinc, calcium and iron. In addition, a 20 microg/d supplement of vitamin D was supplied. The diet provided 15% of energy from protein, 35% from fat and 55% from carbohydrate. The purpose of the study was to determine the dose response of olestra on vitamins D, E and K, carotenoids, vitamin B12, folate and zinc. Circulating concentrations of retinol, carotenoids, tocopherols, 25-hydroxy- and 1,25-dihydroxyvitamin D metabolites, phylloquinone, des-gamma-carboxyprothrombin, prothrombin, folate and hematological parameters were measured biweekly, as were urine concentrations of zinc and gamma-carboxyglutamic acid (Gla). Clinical chemistry, urinalysis and vitamin B12 absorption were measured at wk 0 and 8. Olestra reduced serum concentrations of carotenoids, alpha-tocopherol, 25-hydroxyergocalciferol and phylloquinone in a dose-responsive manner. Olestra did not affect Gla excretion, plasma des-gamma-carboxyprothrombin or prothrombin concentrations, prothrombin time, vitamin B12 absorption, overall vitamin D status or the status of folate or zinc. Laboratory evaluations showed no health-related effects of olestra. Subjects in all groups reported common gastrointestinal symptoms such as loose stools, fecal urgency and flatulence, which were transient and generally mild to moderate in severity. These symptoms did not affect protocol compliance or the ability to measure the potential for olestra to affect nutrient availability. PMID:9237961

Schlagheck, T G; Riccardi, K A; Zorich, N L; Torri, S A; Dugan, L D; Peters, J C

1997-08-01

382

Annual effective dose and concentration levels of gross ? and ? in various waters from Samsun, Turkey  

Microsoft Academic Search

Samsun city which is between the deltas where Ye?il?rmak and K?z?l?rmak rivers run out, exists in the middle part of Black Sea's costal way. It is the biggest city of the Black Sea Region in terms of population, industry, trade, natural and cultural wealth. There is no information about radioactivity measurement reported in water samples in the Samsun province so

F. Korkmaz Görür; R. Keser; S. Dizman; N. T. Okumu?o?lu

2011-01-01

383

DBP Formation in Hot and Cold Water Across a Simulated Distribution System: Effect of Incubation Time, Heating Time, pH, Chlorine Dose, and Incubation Temperature.  

PubMed

This paper demonstrates that disinfection byproducts (DBP) concentration profiles in heated water were quite different from the DBP concentrations in the cold tap water. Chloroform concentrations in the heated water remained constant or even decreased slightly with increasing distribution system water age. The amount of dichloroacetic acid (DCAA) was much higher in the heated water than in the cold water; however, the maximum levels in heated water with different distribution system water ages did not differ substantially. The levels of trichloroacetic acid (TCAA) in the heated water were similar to the TCAA levels in the tap water, and a slight reduction was observed after the tap water was heated for 24 h. Regardless of water age, significant reductions of nonregulated DBPs were observed after the tap water was heated for 24 h. For tap water with lower water ages, there were significant increases in dichloroacetonitrile (DCAN), chloropicrin (CP), and 1,1-dichloropropane (1,1-DCP) after a short period of heating. Heating of the tap water with low pH led to a more significant increase of chloroform and a more significant short-term increase of DCAN. High pH accelerated the loss of the nonregulated DBPs in the heated water. The results indicated that as the chlorine doses increased, levels of chloroform and DCAA in the heated water increased significantly. However, for TCAA, the thermally induced increase in concentration was only notable for the chlorinated water with very high chlorine dose. Finally, heating may lead to higher DBP concentrations in chlorinated water with lower distribution system temperatures. PMID:24044418

Liu, Boning; Reckhow, David A

2013-10-04

384

Snow Water Equivalent Estimation via Assimilation of Modis Snow Cover and Real Time Snow Depth Measurements Data in a Snow Dynamic Model  

Microsoft Academic Search

Estimates of snow water equivalent (SWE) is very difficult due to its high variability also over small distances. This variability makes it often impossible to obtain a sufficiently accurate estimate of the water volume available in the snowpack at the watershed scale. All sources of information to evaluate SWE distribution are then to be considered: point measurements, satellite data and

Simone Gabellani; Roberto Rudari; Fabio Castelli; Giorga Macchiavello; Giorgio Boni

2010-01-01

385

Changes in surface water table depth and soil physical properties after harvest and establishment of loblolly pine ( Pinus taeda L.) in Atlantic coastal plain wetlands of South Carolina  

Microsoft Academic Search

The surface water table is an important factor determining soil chemical, physical and biological processes, and thus affects the functions of forested wetlands. The objective of this study was to assess surface water table dynamics from timber harvesting through early forest plantation establishment in a coastal plain wetland area located in the southeastern United States. Simulated harvesting patterns included two

Yi-Jun Xu; James A Burger; W Michael Aust; Steven C Patterson; Masato Miwa; David P Preston

2002-01-01

386

Flow Contribution and Water Quality with Depth in a Test Hole and Public-Supply Wells: Implications for Arsenic Remediation Through Well Modification, Norman, OK 2003-2006.  

EPA Science Inventory

The City of Norman, Oklahoma, is one municipality affected by a change in the Environmental Protection Agencyâ??s National Primary Drinking Water Regulation for arsenic. In 2006, the maximum contaminant level for arsenic in drinking-water was lowered from 50 to 10 micrograms per li...

387

Indexes and efficiencies of N optimum dose reviewed as water- and Nitrogen- footprint  

NASA Astrophysics Data System (ADS)

In order to establish rational nitrogen (N) fertilization and reduce groundwater contamination, a clearer understanding of the N distribution through the growing season and its balance is crucial. In three successive years, a melon crop (Cucumis melo L. cv. Sancho) was grown under field conditions to determine the uptake of N fertilizer, applied by means of fertigation at different stages of plant growth. In addition, Strategies are being sought to increase water use in cropping systems and to reduce drainage. The estimation of N mineralized from soil organic matter is an essential tool to determine the amount necessary to optimize crop yield and minimize the environmental impact of excess N. In this study we propose a methodology that allows us to study fertigated management integrating several aspects: economic and environmental. Even the complexity of the system, we have reduced the number of indexes and efficiencies need to establish the framework of N management and its economical and environmental consequences. At the same time, we have translated all them into a water- and Nitrogen- footprint in each year. ACKNOWLEDGEMENTS This work has been partially supported by INIA under Project INIA-RTA 2010-00110-C03-02

Castellanos, Maria Teresa; Cartagena, Maria Carmen; Cabello, Maria Jesus; Rivas, Francisco; Tarquis, Ana Maria; Arce, Augusto

2013-04-01

388

Adsorption and reactions of tetraethoxysilane (TEOS) on clean and water-dosed titanium dioxide (110)  

SciTech Connect

The adsorption and reactions of tetraethoxysilane (TEOS) vapor on clean and water-predosed rutile TiO[sub 2]-(110) have been studied using temperature-programmed desorption (TPD), low-energy electron diffraction (LEED), and X-ray photoelectron spectroscopy (XPS). The molecule sticks with a probability near unity at temperatures of 130-300 K, and at low coverage, TEOS dissociates upon heating. At higher coverages, some desorbs. On the water-and hydroxyl-free surface, the dissociation reaction occurs rapidly between 200 and 350 K, with the initial products being Si(OEt)[sub 15s] plus 2EtO[sub 3] (ET = C[sub 2]H[sub 5]). This is a new mechanism for silane coupling to oxide surfaces which requires neither hydroxyl groups nor surface defects. The EtO ligands, whether attached to Ti or Si atoms, decompose at approximately 650 K via [beta]-hydrogen elimination to yield ethylene gas and surface-bound hydrogen, which rapidly attaches to another EtO ligand, yielding ethanol gas. By 700 K, the net products evolved are equal amounts of ethylene and ethanol gas (two molecules of each per dissociated TEOS molecule), while SiO[sub 2] remains on the surface. 41 refs., 7 figs.

Gamble, L.; Hugenschmidt, M.B.; Campbell, C.T.; Jurgens, T.A.; Rogers, J.W. Jr. (Univ. of Washington, Seattle, WA (United States))

1993-12-15

389

NOTE: Peripheral dose outside applicators in electron beams  

NASA Astrophysics Data System (ADS)

The peripheral dose outside the applicators in electron beams was studied using a Varian 21 EX linear accelerator. To measure the peripheral dose profiles and point doses for the applicator, a solid water phantom was used with calibrated Kodak TL films. Peak dose spot was observed in the 4 MeV beam outside the applicator. The peripheral dose peak was very small in the 6 MeV beam and was ignorable at higher energies. Using the 10 × 10 cm2 cutout and applicator, the dose peak for the 4 MeV beam was about 12 cm away from the field central beam axis (CAX) and the peripheral dose profiles did not change with depths measured at 0.2, 0.5 and 1 cm. The peripheral doses and profiles were further measured by varying the angle of obliquity, cutout and applicator size for the 4 MeV beam. The local peak dose was increased with about 3% per degree angle of obliquity, and was about 1% of the prescribed dose (angle of obliquity equals zero) at 1 cm depth in the phantom using the 10 × 10 cm2 cutout and applicator. The peak dose position was also shifted 7 mm towards the CAX when the angle of obliquity was increased from 0 to 15°.

Chow, James C. L.; Grigorov, Grigor N.

2006-06-01

390

TOPICAL REVIEW: Advances in the determination of absorbed dose to water in clinical high-energy photon and electron beams using ionization chambers  

NASA Astrophysics Data System (ADS)

During the last two decades, absorbed dose to water in clinical photon and electron beams was determined using dosimetry protocols and codes of practice based on radiation metrology standards of air kerma. It is now recommended that clinical reference dosimetry be based on standards of absorbed dose to water. Newer protocols for the dosimetry of radiotherapy beams, based on the use of an ionization chamber calibrated in terms of absorbed dose to water, ND,w, in a standards laboratory's reference quality beam, have been published by several national or regional scientific societies and international organizations. Since the publication of these protocols multiple theoretical and experimental dosimetry comparisons between the various ND,w based recommendations, and between the ND,w and the former air kerma (NK) based protocols, have been published. This paper provides a comprehensive review of the dosimetry protocols based on these standards and of the intercomparisons of the different protocols published in the literature, discussing the reasons for the observed discrepancies between them. A summary of the various types of standards of absorbed dose to water, together with an analysis of the uncertainties along the various steps of the dosimetry chain for the two types of formalism, is also included. It is emphasized that the NK-ND,air and ND,w formalisms have very similar uncertainty when the same criteria are used for both procedures. Arguments are provided in support of the recommendation for a change in reference dosimetry based on standards of absorbed dose to water.

Saiful Huq, M.; Andreo, Pedro

2004-02-01

391

Derivation of a melamine oral reference dose (RfD) and drinking-water total allowable concentration.  

PubMed

Due to its high nitrogen content, melamine has been used to adulterate food to increase apparent protein content. In 2008, thousands of Chinese infants consumed reconstituted formula derived from melamine-adulterated milk. Urinary-tract stones (comprised of melamine and uric acid) accumulated in some victims and lead to acute renal failure or death. Premature infants and children (<2 yr) have an increased susceptibility to ingested melamine. Due to incomplete reporting, the human data were inadequate to identify a no-observed-adverse-effect level (NOAEL) for melamine-induced pediatric urolithiasis. Urolithiasis, urinary bladder cystitis, and ulcerations were observed in F344 rats after subchronic or chronic ingestion of melamine at > or =72 mg/kg-d. Bladder epithelial damage was followed by epithelial hyperplasia that progressed to bladder papillomas and carcinomas in male but not female F344 rats or male or female B6C3F1 mice. Short-term assays suggest, at best, weak genotoxic activity, and kinetic data show that melamine is not metabolized. Since reliable exposure information was lacking from the clinical reports, an oral reference dose (RfD) based on urolithiasis in male rats after 13 wk of continuous melamine ingestion was calculated as a 10% benchmark dose (38 mg/kg-d). Incorporation of 10-fold interspecies and intraspecies (for the increased susceptibility of infants) uncertainty factors and a threefold database uncertainty factor (for the lack of immunological, neurological and reproduction toxicity data) yields an oral RfD of 0.13 mg/kg-d. Assuming the 70-kg adult consumes 2 L of drinking water daily, a total allowable concentration of 0.9 mg/L (900 microg/L) was calculated for melamine in drinking water. PMID:20336578

Bhat, Virunya S; Ball, Gwen L; McLellan, Clifton J

2010-01-01

392

Reverse water-in-fluorocarbon emulsions for use in pressurized metered-dose inhalers containing hydrofluoroalkane propellants.  

PubMed

Pulmonary administration of drugs has demonstrated numerous advantages in the treatment of pulmonary diseases due to direct targeting to the respiratory tract. It enables avoiding the first pass effect, reduces the amount of drugs administered, targets drugs to specific sites and reduces their side effects. Reverse water-in-fluorocarbon (FC) emulsions are potential drug delivery systems for pulmonary administration using pressurized metered-dose inhalers (pMDI). The external phase of these emulsions consists of perfluorooctyl bromide (PFOB, perflubron), whereas their internal phase contains the drugs solubilized or dispersed in water. These emulsions are stabilized by a perfluoroalkylated dimorpholinophosphate (F8H11DMP), i.e. a fluorinated surfactant. This study demonstrates the possibility of delivering a reverse fluorocarbon emulsion via the pulmonary route using a CFC-free pMDI. Two hydrofluoroalkanes (HFAs) (Solkane(R) 134a and Solkane(R) 227) were used as propellants, and various solution (or emulsion)/propellant ratios (1/3, 1/2, 2/3, 1/1, 3/2, 3/1 v/v) were investigated. The insolubility of water (with or without the fluorinated surfactant F8H11DMP) in both HFA 227 and HFA 134a was demonstrated. PFOB and the reverse emulsion were totally soluble or dispersible in all proportions in both propellants. This study demonstrated also that the reverse FC emulsion can be successfully used to deliver caffeine in a homogeneous and reproducible way. The mean diameter of the emulsion water droplets in the pressured canister was investigated immediately after packaging and after 1 week of storage at room temperature. Best results were obtained with emulsion/propellant ratios comprised between 2/3 and 3/2, and with HFA 227 as propellant. PMID:11996829

Butz, N; Porté, C; Courrier, H; Krafft, M P; Vandamme, Th F

2002-05-15

393

Pressure Versus Depth  

NSDL National Science Digital Library

In this inquiry activity, students do not know the equation for pressure versus depth before beginning, but through guided activities they discover it themselves. This is a powerful way to get students to conceptually understand the equation and remember

Horton, Michael

2009-05-30

394

Topic in Depth - Gyroscopes  

NSDL National Science Digital Library

This Topic in Depth explores gyroscopes and gyroscopic effect, from introductory materials about how gyroscopes are used in bicycles to research and commercial applications to hypothetical uses, such as in Rosie the Robot from The Jetsons cartoon.

2010-09-14

395

Evaluation of hybrid depth scanning for carbon-ion radiotherapy  

SciTech Connect

Purpose: In radiotherapy with a scanned carbon-ion beam, its Bragg peak is shifted along the depth direction either by inserting the range shifter plates or by changing the beam-extraction energy of a synchrotron. In the former technique (range shifter scanning: RS), the range shifter plates broaden the beam size and produce secondary fragments through nuclear reactions. In the latter technique (active-energy scanning: ES), it may take several seconds to change the beam energy depending on the synchrotron operation cycle, leading to a long treatment time. The authors propose a hybrid depth scan technique (hybrid scanning: HS), where several beam energies are used in conjunction with the range shifter plates for finer range shift. In this study, HS is evaluated from the viewpoints of dose distribution and treatment time. Methods: Assuming realistic accelerator and beam-delivery systems, the authors performed computer simulations using GEANT4 Monte Carlo code for beam modeling and a treatment planning system to evaluate HS. Three target volumes with the same dimensions of 60 x 60 x 60 mm{sup 3} were generated at depths of 45, 85, and 125 mm in water phantom, and uniform clinical dose was planned for these targets. The sizes of lateral dose falloff and the peak to plateau ratio defined as the ratio of the clinical dose averaged over the target to the clinical dose at the entrance as well as the treatment time were compared among the three depth scan techniques. Results: The sizes of lateral dose falloffs at the center of SOBP are 11.4, 8.5, and 5.9 mm for the three targets in RS, while they are 5.7, 4.8, and 4.6 mm in ES and 6.6, 5.7, and 5.0 mm in HS, respectively. The peak to plateau ratios are 1.39, 1.96, and 2.15 in RS, while they are 1.48, 2.04, and 2.19 in ES and 1.47, 2.03, and 2.18 in HS, respectively. The treatment times are 128.7, 128.6, and 128.6 s in ES, while they are 61.2, 54.6, and 47.8 s in RS and 43.2, 44.1, and 44.7 s in HS, respectively. The multiple scattering and the nuclear reaction by range shifter degraded the beam qualities such as lateral dose falloff and peak to plateau ratio, which was especially pronounced for the shallow target in RS. The depth scan timing was limited by accelerator cycle in ES. That increased the treatment time by a few times. Conclusions: This study revealed that HS can provide dose distributions with steeper lateral dose falloffs and higher peak to plateau ratio comparing to RS and comparable to ES. In addition, the treatment time can be considerably reduced in HS compared to ES.

Inaniwa, Taku; Furukawa, Takuji; Kanematsu, Nobuyuki; Mori, Shinichiro; Mizushima, Kota; Sato, Shinji; Toshito, Toshiyuki; Shirai, Toshiyuki; Noda, Koji [Medical Physics Research Group, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Anagawa 4-9-1, Inage-ku, Chiba 263-8555 (Japan); Quality Life 21 Johoku Promotion Office, Health Department, Health and Welfare Bureau, Nagoya City, Sannomaru 3-1-1, Naka-ku, Nagoya 460-8508 (Japan); Medical Physics Research Group, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Anagawa 4-9-1, Inage-ku, Chiba 263-8555 (Japan)

2012-05-15

396

Water-filled balloon in the postoperative resection cavity improves dose distribution to target volumes in radiotherapy of maxillary sinus carcinoma.  

PubMed

Postoperative radiotherapy is a major treatment for patients with maxillary sinus carcinoma. However, the irregular resection cavity poses a technical difficulty for this treatment, causing uneven dose distribution to target volumes. In this study, we evaluated the dose distribution to target volumes and normal tissues in postoperative intensity-modulated radiotherapy (IMRT) after placing a water-filled balloon into the resection cavity. Three postoperative patients with advanced maxillary sinus carcinoma were selected in this trial. Water-filled balloons and supporting dental stents were fabricated according to the size of the maxillary resection cavity. Simulation CT scans were performed with or without water-filled balloons, IMRT treatment plans were established, and dose distribution to target volumes and organs at risk were evaluated. Compared to those in the treatment plan without balloons, the dose (D98) delivered to 98% of the gross tumor volume (GTV) increased by 2.1 Gy (P = 0.009), homogeneity index (HI) improved by 2.3% (P = 0.001), and target volume conformity index (TCI) of 68 Gy increased by 18.5% (P = 0.011) in the plan with balloons. Dosimetry endpoints of normal tissues around target regions in both plans were not significantly different (P > 0.05) except for the optic chiasm. In the plan without balloons, 68 Gy high-dose regions did not entirely cover target volumes in the ethmoid sinus, posteromedial wall of the maxillary sinus, or surgical margin of the hard palate. In contrast, 68 Gy high-dose regions entirely covered the GTV in the plan with balloons. These results suggest that placing a water-filled balloon in the resection cavity for postoperative IMRT of maxillary sinus carcinoma can reduce low-dose regions and markedly and simultaneously increase dose homogeneity and conformity of target volumes. PMID:22035860

Zhang, Qun; Lin, Shi-Rong; He, Fang; Kang, De-Hua; Chen, Guo-Zhang; Luo, Wei

2011-11-01

397

MultiChannel Ground Penetrating Radar: A Fast, Non-Invasive Tool to Detect Reflector Depth and Average Water Content Simultaneously  

Microsoft Academic Search

Many hydrologic applications require information from subsurface structure and water content distribution over distances of some hundreds of meters to kilometers. An accurate monitoring tool therefor would provide i) input data for and ii) allow the validation of large scale hydrologic numerical simulations. It would also close the gap between local measurements and large scale remote sensing applications. A promising

H. Gerhards; U. Wollschläger; K. Roth

2007-01-01

398

WAVECALC: an Excel-VBA spreadsheet to model the characteristics of fully developed waves and their influence on bottom sediments in different water depths  

Microsoft Academic Search

The generation and growth of waves in deep water is controlled by winds blowing over the sea surface. In fully developed sea states, where winds and waves are in equilibrium, wave parameters may be calculated directly from the wind velocity. We provide an Excel spreadsheet to compute the wave period, length, height and celerity, as well as horizontal and vertical

Jacobus P. Le Roux; Zeki Demirbilek; Marysia Brodalka; Burghard W. Flemming

2010-01-01

399

Diving behavior in Anopheles gambiae (Diptera: Culicidae): avoidance of a predacious wolf spider (Araneae: Lycosidae) in relation to life stage and water depth.  

PubMed

It has been suggested that mosquito larvae and pupae dive to avoid predators. We tested this predator-avoidance hypothesis by using immature Anopheles gambiae Giles (Diptera: Culicidae) and the wolf spider Pardosa messingerae (Stand) (Araneae: Lycosidae). Because previous studies have suggested that wolf spiders are poor predators of immature mosquitoes, we first examined the predatory ability of the wolf spider and found that the spider was effective at capturing all stages of larvae and pupae. The mortality from experimental cups containing deep water increased with the age of mosquitoes, with the exception of pupae. In contrast, this trend was not observed in shallow water. In particular, mortality was significantly lower in deep water during the second instar. During the third instar, the opposite trend was observed. When the effect of cannibalism was excluded by subtracting the number of missing mosquitoes for the treatment without spiders from those with spiders, the cannibalism corrected mortality was significantly lower in deep water during the second instar. The duration of diving by larvae and pupae decreased with age. With the exception of first instar, diving frequency also decreased with age. We postulate that this diving behavior allows An. gambiae to escape predation by wolf spiders, which supports the predator-avoidance hypothesis. This study indicates some important implications for vector control. PMID:19058628

Futami, Kyoko; Sonye, George; Akweywa, Peter; Kaneko, Satoshi; Minakawa, Noboru

2008-11-01

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Association of Arsenic with Redox Conditions, Depth, and Ground-Water Age in the Glacial Aquifer System of the Northern United States.  

National Technical Information Service (NTIS)

More than 800 wells in the glacial aquifer system of the Northern United States were sampled for arsenic as part of U.S. Geological Survey National Water-Quality Assessment (NAWQA) studies during 1991-2003. Elevated arsenic concentrations (greater than or...

M. A. Thomas

2007-01-01