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1

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

2

Water surface depth instrument  

NASA Technical Reports Server (NTRS)

Measurement gage provides instant visual indication of water depth based on capillary action and light diffraction in a group of solid, highly polished polymethyl methacrylate rods. Rod lengths are adjustable to measure various water depths in any desired increments.

Davis, Q. C., IV

1970-01-01

3

Analytic fits to Monte Carlo calculated depth-dose curves of 1- to 50-MeV electrons in water  

NASA Astrophysics Data System (ADS)

An analytic expression is given for depth-dose curves of plane-parallel electron beams normally incident on semi-infinite water absorbers with initial energies from 1 to 50 MeV. The expression consists of two terms representing the main component due to collision energy-loss of primary electrons and the component via radiative process. To study the profile of the bremsstrahlung component, Monte Carlo calculations have been made with the MCEF code. The results show that this component has a maximum around 0.9 r0, where r0 is the csda (continuous slowing-down approximation) range of electrons in water. Values of the constants in the main term have been determined so as to minimize the deviations of the expression from the depth-dose data calculated with three Monte Carlo codes (MCEF, EGS4 and ITS). The maximum value of the deviations is from 0.7 to 3.5% of the maximum dose at each energy and is less than or comparable to the maximum deviations among the different Monte Carlo results.

Tatsuo, Tabata; Andreo, Pedro; Rinsuke, Ito

1991-06-01

4

Polarization lidar for shallow water depth measurement.  

PubMed

A bathymetric, polarization lidar system transmitting at 532 nm and using a single photomultiplier tube is employed for applications of shallow water depth measurement. 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 1 order of magnitude improvement over current water depth determination techniques. In laboratory tests, an 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 with an ice floor to simulate a glacial meltpond. Measurement of 1 cm water depths with an uncertainty of ±3 mm are demonstrated using the technique. This novel approach enables new approaches to designing laser bathymetry systems for shallow depth determination from remote platforms while not compromising deep water depth measurement. PMID:21173834

Mitchell, Steven; Thayer, Jeffrey P; Hayman, Matthew

2010-12-20

5

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

6

Calculated depth dose tables for californium-252 sources in tissue  

Microsoft Academic Search

Depth dose tables for 252Cf sources of various designs currently available for use in radiotherapy have been calculated. Tables are presented for 5 cm along the transverse axis and 5 cm along the source axis in steps of 0.5 cm. Gamma-dose due to the primary gamma -rays includes a correction for the self-absorption in the platinum- iridium wire on which

V. Krishnaswamy

1972-01-01

7

Depth dose perturbation by a hydrogel fiducial marker in a proton beam.  

PubMed

The purpose of this study was to evaluate proton depth dose perturbation caused by a radio-opaque hydrogel fiducial marker. Electronic proton stopping powers in the hydrogel were calculated for energies 0.5-250 MeV, and Monte Carlo simulations were generated of hydrogel vs. gold markers placed at various water phantom depths in a generic proton beam. Across the studied energy range, the gel/water stopping power ratio was 1.0146 to 1.0160. In the Monte Carlo simulation, the hydrogel marker caused no discernible perturbation of the proton percent depth-dose (PDD) curve. In contrast, the gold marker caused dose reductions of as much as 20% and dose shadowing regions as long as 6.5 cm. In contrast to gold markers, the radio-opaque hydrogel marker causes negligible proton depth dose perturbation. This factor may be taken into consideration for image-guided proton therapy at facilities with suitable imaging modalities. PMID:25679167

Zhang, Miao; Reyhan, Meral; Kim, Leonard H

2015-01-01

8

Central axis depth dose curve for electron beams  

SciTech Connect

In this article an analytical equation for electron depth dose is proposed for electron energies from 6--20 MeV. The equation contains four parameters and it fits the build-up region, fall-off region as well as the bremsstrahlung background region. The calculated values from this equation fit within 1,5% of the measured data in the build-up region and in the fall-off region within 0,5 mm for the energy range 5--10 MeV and within 1 mm for the range 12--20 MeV. This equation can be applied beyond the practical range.

Strydom, W.J. (Department of Medical Physics, Medical University of Southern Africa, P.O. Medunsa 0204 (Republic of South Africa))

1991-11-01

9

Task 1: Water Depth Management, 1388  

NASA Technical Reports Server (NTRS)

The author has identified the following significant results. ERTS-1 MSS data taken on October 10, 1972, of the Little Bahama Bank are being used to demonstrate the use of ERTS-1 data for mapping of shallow water features for the purpose of upgrading world navigation charts. Marked reflectance differences occur for the shallow water areas in bands 4, 5, and 6. Digital processing of two adjacent data tapes within the ERTS-1 frame covering an area of about 40 by 40 miles has been completed. Correlation of depth measurements to 5 meters has been successful. A mathematical model for depth measurements using ratio of voltages in band 4 and 5 has been successfully developed and is being tested for accuracy. Additional studies for areas near Puerto Rico and in northern Lake Michigan will be undertaken. Satellite data will also provide geographical evidence for verifying existence or nonexistence of doubtful shoal waters now appearing on world charts and considered to be hazardous to shipping.

Polcyn, F. C. (principal investigator)

1973-01-01

10

Depth-dose relations for heavy ion beams  

NASA Technical Reports Server (NTRS)

Radiation transport of heavy ions in matter is of interest to radiological protection in space and high-altitude aircraft. In addition, heavy ion beams are expected to be of advantage in radiotherapy since their characteristic Bragg curve allows a relative reduction of the dose in reaching a tumor site and the near elimination of exposure beyond the tumor region as the beam exits the body. Furthermore, the radioresistance of tumorous cells due to their hypoxic state may be reduced or eliminated by the high specific ionization of heavy ion beams. The depth-dose distribution of heavy ion beams consists of energy deposited by the attenuated primary beam with its characteristic Bragg curve and a relatively unstructured background due to secondary radiations produced in nuclear reactions. As the ion mass increases, the secondary contribution becomes more structured and may add significantly to the Bragg peak of the primary ions. The result for heavy ions (z greater than 20) is a greatly broadened Bragg peak region, especially in comparison to straggling effects, which may prove to be of importance in radiotherapy and biomedical research.

Wilson, J. W.

1977-01-01

11

Spatially continuous interpolation of water stage and water depths using the Everglades depth estimation network (EDEN)  

USGS Publications Warehouse

The Everglades Depth Estimation Network (EDEN) is an integrated network of real-time water-level monitoring, ground-elevation modeling, and water-surface modeling that provides scientists and managers with current (2000-present), online water-stage and water-depth information for the entire freshwater portion of the Greater Everglades. Continuous daily spatial interpolations of the EDEN network stage data are presented on a 400-square-meter grid spacing. EDEN offers a consistent and documented dataset that can be used by scientists and managers to (1) guide large-scale field operations, (2) integrate hydrologic and ecological responses, and (3) support biological and ecological assessments that measure ecosystem responses to the implementation of the Comprehensive Everglades Restoration Plan (CERP) The target users are biologists and ecologists examining trophic level responses to hydrodynamic changes in the Everglades.

Pearlstine, Leonard; Higer, Aaron; Palaseanu, Monica; Fujisaki, Ikuko; Mazzotti, Frank

2007-01-01

12

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

13

Depth dose dependence of the mouse bone using kilovoltage photon beams: A Monte Carlo study for small-animal irradiation  

NASA Astrophysics Data System (ADS)

This study investigated the dose enhancement due to the presence of mouse bone irradiated by the kilovoltage (kV) photon beams. Dosimetry of the bone associated with soft and lung tissue was determined by Monte Carlo simulations using the EGSnrc-based code in millimeter scale. Two inhomogeneous phantoms with 2 mm of bone layer sandwiched by: (1) water and lung (bone-lung phantom); and (2) water (bone-water phantom), were used. Relative depth doses along the central beam axes in the phantoms and dose enhancement ratios (bone dose in the above inhomogeneous phantoms to the dose at the same point in the water phantom) were determined using the 100 and 225 kVp photon beams. For the 100 kVp photon beams, the depth dose gradient in the bone was significantly larger compared to that in a water phantom without the bone. This is due to the beam hardening effect that some low-energy photons were filtered out in the deeper depth, resulting in less photoelectric interactions and hence energy depositions in the bone. Moreover, dose differences between the top and downstream (bottom) bone edges at depths of 1-5 mm were 168-192% and 149-166% for the bone-lung and bone-water phantom, respectively. These differences were larger than 21-27% (bone-lung) and 12-23% (bone-water) for the 225 kVp photon beams. The maximum dose enhancement ratio in the bone for the bone-lung and bone-water phantoms in various depths was about 5.7 using the 100 kVp photon beams. This ratio was larger than two times of that (2.4) for the 225 kVp photon beams. It is concluded that, apart from the basic beam characteristics such as attenuation and penumbra, which are related to the photon beam energy in the mouse irradiation, the bone dose is another important factor to consider when selecting the beam energy in the small-animal treatment planning, provided that the bone dose enhancement is a concern in the preclinical model.

Chow, James C. L.

2010-05-01

14

Tissue depth dose calculations for breast cancer using MCNPX  

NASA Astrophysics Data System (ADS)

Determining the dose rate as a function of distance within both cancerous tumor tissue as well as healthy tissue represents a proof of concept for medical diagnostic techniques finding overall dose absorption. The Monte Carlo N-Particle Transport Code (MCNPX) was used to replicate radiotherapy treatments of external-beam radiation and high-dose-rate brachytherapy used in stages one and two of breast cancer. Modeling of conventional diagnostic radiology methods is limited by not only the chosen complexity of tissue material, but also in understanding absorbed dose. Preliminary results will be presented.

Dallas, C. B.; Crawford, B. E.; Stephenson, S. L.

2002-10-01

15

Nuclear-interaction correction of integrated depth dose in carbon-ion radiotherapy treatment planning  

NASA Astrophysics Data System (ADS)

In treatment planning of charged-particle therapy, tissue heterogeneity is conventionally modeled as water with various densities, i.e. stopping effective densities {?\\text{S}}, and the integrated depth dose measured in water (IDD) is applied accordingly for the patient dose calculation. Since the chemical composition of body tissues is different from that of water, this approximation causes dose calculation errors, especially due to difference in nuclear interactions. Here, we propose and validate an IDD correction method for these errors in patient dose calculations. For accurate handling of nuclear interactions, {?\\text{S}} of the patient is converted to nuclear effective density {?\\text{N}}, defined as the ratio of the probability of nuclear interactions in the tissue to that in water using a recently formulated semi-empirical relationship between the two. The attenuation correction factor ? \\text{w}\\text{p}, defined as the ratio of the attenuation of primary carbon ions in a patient to that in water, is calculated from a linear integration of {?\\text{N}} along the beam path. In our treatment planning system, a carbon-ion beam is modeled to be composed of three components according to their transverse beam sizes: primary carbon ions, heavier fragments, and lighter fragments. We corrected the dose contribution from primary carbon ions to IDD as proportional to ? \\text{w}\\text{p}, and corrected that from lighter fragments as inversely proportional to ? \\text{w}\\text{p}. We tested the correction method for some non-water materials, e.g. milk, lard, ethanol and water solution of potassium phosphate (K2HPO4), with un-scanned and scanned carbon-ion beams. In un-scanned beams, the difference in IDD between a beam penetrating a 150?mm-thick layer of lard and a beam penetrating water of the corresponding thickness amounted to ?4%, while it was +6% for a 150?mm-thick layer of 40% K2HPO4. The observed differences were accurately predicted by the correction method. The corrected IDDs agreed with the measurements within ±1% for all materials and combinations of them. In scanned beams, the dose estimation error in target dose amounted to 4% for a 150?mm-thick layer of 40% K2HPO4. The error is significantly reduced with the correction method. The planned dose distributions with the method agreed with the measurements within ±1.5% of target dose for all materials not only in the target region but also in the plateau and fragment-tail regions. We tested the correction method of IDD in some non-water materials to verify that this method would offer the accuracy and simplicity required in carbon-ion radiotherapy treatment planning.

Inaniwa, T.; Kanematsu, N.; Hara, Y.; Furukawa, T.

2015-01-01

16

Nuclear-interaction correction of integrated depth dose in carbon-ion radiotherapy treatment planning.  

PubMed

In treatment planning of charged-particle therapy, tissue heterogeneity is conventionally modeled as water with various densities, i.e. stopping effective densities [Formula: see text] and the integrated depth dose measured in water (IDD) is applied accordingly for the patient dose calculation. Since the chemical composition of body tissues is different from that of water, this approximation causes dose calculation errors, especially due to difference in nuclear interactions. Here, we propose and validate an IDD correction method for these errors in patient dose calculations.For accurate handling of nuclear interactions, [Formula: see text] of the patient is converted to nuclear effective density [Formula: see text] defined as the ratio of the probability of nuclear interactions in the tissue to that in water using a recently formulated semi-empirical relationship between the two. The attenuation correction factor [Formula: see text] defined as the ratio of the attenuation of primary carbon ions in a patient to that in water, is calculated from a linear integration of [Formula: see text] along the beam path. In our treatment planning system, a carbon-ion beam is modeled to be composed of three components according to their transverse beam sizes: primary carbon ions, heavier fragments, and lighter fragments. We corrected the dose contribution from primary carbon ions to IDD as proportional to [Formula: see text] and corrected that from lighter fragments as inversely proportional to [Formula: see text] We tested the correction method for some non-water materials, e.g. milk, lard, ethanol and water solution of potassium phosphate (K2HPO4), with un-scanned and scanned carbon-ion beams.In un-scanned beams, the difference in IDD between a beam penetrating a 150?mm-thick layer of lard and a beam penetrating water of the corresponding thickness amounted to -4%, while it was +6% for a 150?mm-thick layer of 40% K2HPO4. The observed differences were accurately predicted by the correction method. The corrected IDDs agreed with the measurements within ±1% for all materials and combinations of them. In scanned beams, the dose estimation error in target dose amounted to 4% for a 150?mm-thick layer of 40% K2HPO4. The error is significantly reduced with the correction method. The planned dose distributions with the method agreed with the measurements within ±1.5% of target dose for all materials not only in the target region but also in the plateau and fragment-tail regions.We tested the correction method of IDD in some non-water materials to verify that this method would offer the accuracy and simplicity required in carbon-ion radiotherapy treatment planning. PMID:25517336

Inaniwa, T; Kanematsu, N; Hara, Y; Furukawa, T

2015-02-01

17

Depth-dose and stopping-power data for mono-energetic electron beams  

NASA Astrophysics Data System (ADS)

The determination of absorbed dose to water in electron beams from ionization measurements in a phantom is based today mainly on data computed with the Monte Carlo code ETRAN. Changes in the energy-loss sampling procedure of ETRAN have produced significant modifications in electron transport results used in electron dosimetry. The magnitude of the changes in electron data in the energy interval used in radiation therapy with electron beams has been investigated using other Monte Carlo codes (MCEF, EGS, ITS). The depth-dose data and water/air stopping-power ratios are compared with the existing results calculated with ETRAN for a wide energy range of broad plane-parallel monoenergetic electron beams and an alternative set of data has been computed. Calculations of water/air stopping-power ratios using different sets of density-effect corrections have been performed. The influences on the dosimetry of electron beams given the present state of knowledge of electron stopping-powers is discussed.

Andreo, Pedro

1990-08-01

18

Asymptotic Viscous Shallow Water Model with Dependence on Depth  

Microsoft Academic Search

A new shallow water model with viscosity and dependence on depth is presented. It is derived from the Navier-Stokes equations, with an anisotropic viscosity tensor, in a shallow domain. Asymptotic analysis has been used as in our previous works [1]–[4]. The new model calculates the depth-averaged horizontal velocity, but also the three components of velocity for all z.

Jose´ M. Rodri´guez; Raquel Taboada-Va´zquez

2010-01-01

19

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 ...

20

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

21

A depth-dependent formula for shallow water propagation.  

PubMed

In shallow water propagation, the sound field depends on the proximity of the receiver to the sea surface, the seabed, the source depth, and the complementary source depth. While normal mode theory can predict this depth dependence, it can be computationally intensive. In this work, an analytical solution is derived in terms of the Faddeeva function by converting a normal mode sum into an integral based on a hypothetical continuum of modes. For a Pekeris waveguide, this approach provides accurate depth dependent propagation results (especially for the surface decoupling) without requiring complex calculation methods for eigenvalues and corresponding eigenfunctions. PMID:25096092

Sertlek, Hüseyin Özkan; Ainslie, Michael A

2014-08-01

22

An evaluation of the recommendations of the TG-25 protocol for determination of depth dose curves for electron beams using ionization chambers.  

PubMed

AAPM Radiation Therapy Committee Task Group 25 has recently outlined a protocol for the determination of relative dose curves for electron beams [Med. Phys. 18, 73-109 (1991)]. We have performed an evaluation of this protocol by comparing the central axis depth dose curves determined from measurements using two different ionization chambers and three different phantom materials. Measurements were made with a Farmer-type PTW and Capintec ionization chamber in solid water, PMMA, and clear polystyrene phantoms irradiated by 6- and 15-MeV electron beams. Central axis depth dose curves were generated from the measured depth-ionization data using the new protocol. For both the chambers and energies investigated in this study, excellent agreement was observed among all the depth doses in water obtained from measurements in all of the three phantoms studied. PMID:7476721

Huq, M S; Agostinelli, A G; Nath, R

1995-08-01

23

Dose distributions at extreme irradiation depths of gamma knife radiosurgery: EGS4 Monte Carlo calculations  

E-print Network

Dose distributions at extreme irradiation depths of gamma knife radiosurgery: EGS4 Monte Carlo calculations J.Y.C. Cheunga,b , K.N. Yub, *, C.P. Yua , R.T.K. Hoa a Gamma Knife Centre (HK), Canossa Hospital The accuracy of the dose planning system (Leksell GammaPlan), used in Gamma Knife (type B) radiosurgery

Yu, K.N.

24

Shallow water table depth algorithm in SWAT: Recent developments  

Technology Transfer Automated Retrieval System (TEKTRAN)

Knowledge of the shallow water table depth (wtd) is crucial in many studies including determination of optimum irrigation and drainage management systems for agricultural production, farm machine trafficability, and water quality due to agricultural chemical transport and soil salinity. Therefore, i...

25

Hyperspectral remote sensing for shallow waters: 2. Deriving bottom depths and water properties  

E-print Network

Hyperspectral remote sensing for shallow waters: 2. Deriving bottom depths and water properties very well in retrieving in-water optical properties and bottom depths from above-surface hyperspectral, and the optical properties of the water col- umn have to be known or derived. In earlier studies1­8 values

Lee, Zhongping

26

Dose to water versus dose to medium in proton beam therapy  

Microsoft Academic Search

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

Harald Paganetti

2009-01-01

27

Monte Carlo simulation of depth dose distribution in several organic models for boron neutron capture therapy  

NASA Astrophysics Data System (ADS)

Monte Carlo simulations are performed to evaluate depth-dose distributions for possible treatment of cancers by boron neutron capture therapy (BNCT). The ICRU computational model of ADAM & EVA was used as a phantom to simulate tumors at a depth of 5 cm in central regions of the lungs, liver and pancreas. Tumors of the prostate and osteosarcoma were also centered at the depth of 4.5 and 2.5 cm in the phantom models. The epithermal neutron beam from a research reactor was the primary neutron source for the MCNP calculation of the depth-dose distributions in those cancer models. For brain tumor irradiations, the whole-body dose was also evaluated. The MCNP simulations suggested that a lethal dose of 50 Gy to the tumors can be achieved without reaching the tolerance dose of 25 Gy to normal tissue. The whole-body phantom calculations also showed that the BNCT could be applied for brain tumors without significant damage to whole-body organs.

Matsumoto, T.

2007-09-01

28

Wave-current interaction in water of finite depth  

E-print Network

In this thesis, the nonlinear interaction of waves and current in water of finite depth is studied. Wind is not included. In the first part, a 2D theory for the wave effect on a turbulent current over rough or smooth bottom ...

Huang, Zhenhua, 1967-

2004-01-01

29

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. PMID:23145244

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

2011-01-01

30

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

2011-01-01

31

Groundshine dose-rate conversion factors of soil contaminated 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

2013-12-01

32

Multi-temporal water depth mapping by means of Landsat TM  

Microsoft Academic Search

The water depth in coastal areas was assumed to be linear with the first principal component of the logarithms of the detected signals within the spectral bands of the satellite sensor. Hence, relative water depths (digital counts) were computed. Charts of absolute water depths were then derived by the application of several calibration points with known water depth. The charts

W. van Hengel; D. Spitzer

1991-01-01

33

Estimation of infragravity waves at intermediate water depth  

Microsoft Academic Search

The accuracy of nearshore infragravity wave height model predictions has been investigated using a combination of the spectral short wave evolution model SWAN and a linear 1D SurfBeat model (IDSB). Data recorded by a wave rider located approximately 3.5km from the coast at 18m water depth have been used to construct the short wave frequency-directional spectra that are subsequently translated

A. J. H. M. Reniers; M. J. Groenewegen; K. C. Ewans; S. Masterton; G. S. Stelling; J. Meek

2010-01-01

34

Compact water depth sensor with LPFG using the photoelastic effect and heat-shrinkable tube  

NASA Astrophysics Data System (ADS)

We propose a compact water depth sensor with a long period fiber grating (LPFG) using a heat-shrinkable tube. The pressure property of the LPFG is investigated experimentally to confirm the feasibility of the water depth sensor. Moreover, the water depth in the 2m long water-filled pipe is successfully estimated by the proposed water sensors.

Takama, Shinya; Kudomi, Takamasa; Ohashi, Masaharu; Miyoshi, Yuji

2011-12-01

35

Depth distribution of absorbed dose on the external surface of Cosmos 1887 biosatellite  

NASA Technical Reports Server (NTRS)

Significant absorbed dose levels exceeding 1.0 Gy day-1 have been measured on the external surface of the Cosmos 1887 biosatellite as functions of depth in stacks of thin thermoluminescent detectors (TLDs) of U.S.S.R. and U.S.A. manufacture. The dose was found to decrease rapidly with increasing absorber thickness, thereby indicating the presence of intensive fluxes of low-energy particles. Comparison between the U.S.S.R. and U.S.A. results and calculations based on the Vette Model environment are in satisfactory agreement. The major contribution to the dose under thin shielding thickness is shown to be from electrons. The fraction of the dose due to protons and heavier charged particles increases with shielding thickness.

Dudkin, V. E.; Kovalev, E. E.; Benton, E. V.; Frank, A. L.; Watts, J. W. Jr; Parnell, T. A.

1990-01-01

36

Effect of indoor activity size distribution of (222)Rn progeny in-depth dose estimation.  

PubMed

In this work, the attached and unattached activity size distribution of (222)Rn progeny ((214)Bi and (218)Po) were measured indoor. The fraction of attached progeny was collected using a low-pressure Berner cascade-impactor technique. A constructed wire screen diffusion battery was used for collecting the fraction of unattached progeny. Most of the attached activities for (214)Bi progeny were associated with the aerosol particles of the accumulation mode. The active median aerodynamic diameter (AMAD) of this mode for (214)Bi was determined to be 350nm with a geometric standard division (GSD) of 3. The GSD of unattached size distributions for (218)Po was 1.3 with an active median aerodynamic diameter (AMTD) of 1.3nm. Given that dose estimation is sensitive to environmental conditions, an analytical method was introduced to compute the local energy deposition of (218)Po alpha particles in a target volume of 1?m spheres located at different depths in bronchial epithelium. While the depth-dose distributions for nuclides uniformly distributed within the epithelium were found to be practically constant with depth, they decreased in an almost linear fashion with increasing depth for nuclides on the airway surface. PMID:25528018

Yuness, Mostafa; Mohamed, Amer; AbdEl-Hady, Moustafa; Moustafa, Mona; Nazmy, Hyam

2015-03-01

37

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

NASA Astrophysics Data System (ADS)

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 specified in Monte Carlo calculated radiotherapy treatment plans. The study uses voxelized, virtual human phantoms, FAX06/MAX06 (female/male), incorporated into an EGSnrc Monte Carlo code to perform Monte Carlo dose calculations during simulated irradiation by a 6 MV photon beam from an Elekta SL25 accelerator. Head and neck, chest and pelvis irradiations are studied. FAX06/MAX06 include precise modelling of spongiosa based on µCT images, allowing dose to RBM and BSC to be resolved from the dose to bone. Modifications to the FAX06/MAX06 user codes are required to score Dw and Dm in spongiosa. Dose uncertainties of ~1% (BSC, RBM) or ~0.5% (Dm, Dw) are obtained after up to 5 days of simulations on 88 CPUs. Clinically significant differences (>5%) between Dm and Dw are found only in cranial spongiosa, where the volume fraction of trabecular bone (TBVF) is high (55%). However, for spongiosa locations where there is any significant difference between Dm and Dw, comparisons of differential dose volume histograms (DVHs) and average doses show that Dw provides a better overall estimate of dose to RBM and BSC. For example, in cranial spongiosa the average Dm underestimates the average dose to sensitive tissue by at least 5%, while average Dw is within ~1% of the average dose to sensitive tissue. Thus, it is better to specify Dw than Dm in Monte Carlo treatment plans, since Dw provides a better estimate of dose to sensitive tissue in bone, the only location where the difference is likely to be clinically significant.

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

2010-08-01

38

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

39

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

PubMed

The purpose of this study is to determine whether dose to medium, D(m), or dose to water, D(w), 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 D(m) or D(w) should be specified in Monte Carlo calculated radiotherapy treatment plans. The study uses voxelized, virtual human phantoms, FAX06/MAX06 (female/male), incorporated into an EGSnrc Monte Carlo code to perform Monte Carlo dose calculations during simulated irradiation by a 6 MV photon beam from an Elekta SL25 accelerator. Head and neck, chest and pelvis irradiations are studied. FAX06/MAX06 include precise modelling of spongiosa based on microCT images, allowing dose to RBM and BSC to be resolved from the dose to bone. Modifications to the FAX06/MAX06 user codes are required to score D(w) and D(m) in spongiosa. Dose uncertainties of approximately 1% (BSC, RBM) or approximately 0.5% (D(m), D(w)) are obtained after up to 5 days of simulations on 88 CPUs. Clinically significant differences (>5%) between D(m) and D(w) are found only in cranial spongiosa, where the volume fraction of trabecular bone (TBVF) is high (55%). However, for spongiosa locations where there is any significant difference between D(m) and D(w), comparisons of differential dose volume histograms (DVHs) and average doses show that D(w) provides a better overall estimate of dose to RBM and BSC. For example, in cranial spongiosa the average D(m) underestimates the average dose to sensitive tissue by at least 5%, while average D(w) is within approximately 1% of the average dose to sensitive tissue. Thus, it is better to specify D(w) than D(m) in Monte Carlo treatment plans, since D(w) provides a better estimate of dose to sensitive tissue in bone, the only location where the difference is likely to be clinically significant. PMID:20668336

Walters, B R B; Kramer, R; Kawrakow, I

2010-08-21

40

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

41

Depth of soil water uptake by tropical rainforest trees during dry periods: does tree dimension matter?  

PubMed

Though the root biomass of tropical rainforest trees is concentrated in the upper soil layers, soil water uptake by deep roots has been shown to contribute to tree transpiration. A precise evaluation of the relationship between tree dimensions and depth of water uptake would be useful in tree-based modelling approaches designed to anticipate the response of tropical rainforest ecosystems to future changes in environmental conditions. We used an innovative dual-isotope labelling approach (deuterium in surface soil and oxygen at 120-cm depth) coupled with a modelling approach to investigate the role of tree dimensions in soil water uptake in a tropical rainforest exposed to seasonal drought. We studied 65 trees of varying diameter and height and with a wide range of predawn leaf water potential (?pd) values. We confirmed that about half of the studied trees relied on soil water below 100-cm depth during dry periods. ?pd was negatively correlated with depth of water extraction and can be taken as a rough proxy of this depth. Some trees showed considerable plasticity in their depth of water uptake, exhibiting an efficient adaptive strategy for water and nutrient resource acquisition. We did not find a strong relationship between tree dimensions and depth of water uptake. While tall trees preferentially extract water from layers below 100-cm depth, shorter trees show broad variations in mean depth of water uptake. This precludes the use of tree dimensions to parameterize functional models. PMID:23852028

Stahl, Clément; Hérault, Bruno; Rossi, Vivien; Burban, Benoit; Bréchet, Claude; Bonal, Damien

2013-12-01

42

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. PMID:23532059

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

2013-01-01

43

Hydrologic evaluation using two SWAT shallow water table depth algorithms in the south fork watershed  

Technology Transfer Automated Retrieval System (TEKTRAN)

Recently, a new shallow water table depth (wtd) algorithm (Modified DRAINMOD) that relates drainage volume (vol) to wtd was incorporated into the Soil and Water Assessment Tool (SWAT), a continuous-time physically-based watershed-scale hydrologic model, to improve water table depth fluctuation profi...

44

Depth-dose equivalent relationship for cosmic rays at various solar minima  

NASA Technical Reports Server (NTRS)

Galactic cosmic rays (GCR) pose a serious radiation hazard for long-duration missions. In designing a lunar habitat or a Mars transfer vehicle, the radiation exposure determines the GCR shielding thickness, and hence the weight of spacecraft. Using the spherically symmetric diffusion theory of the solar modulation of GCR, and data on the differential energy spectra of H, He, O, and Fe, from 1965 to 1989, it has been shown that (1) the flux is determined by the diffusion parameter which is a function of the time in the solar cycle, and (2) the fluxes in the 1954 and 1976-1977 solar minima were similar and higher than those in 1965. In this paper, we have extended the spherical solar modulation theory back to 1954. The 1954-1955 GCR flux was nearly the same as that from 1976 to 1977; the 1965 flux values were nearly the same as those in 1986. Using this theory we have obtained the GCR spectra for all the nuclei, and calculated the depth dose as a function of Al thickness. It is shown that the shielding required to stay below 0.5 Sv is 17.5 -3/+8 g/sq cm of Al, and 9 -1.5/+5 g/sq cm to stay below 0.6 Sv. The calculated dose equivalent using the ICRP 60 values for quality factors is about 15 percent higher than that calculated using the ICRP 26 value.

Badhwar, G. D.; Cucinotta, F. A.; O'Neill, P. M.

1993-01-01

45

A new shallow water model with linear dependence on depth  

Microsoft Academic Search

In this paper, we study the Euler equations in a domain with small depth. With this aim, we introduce a small adimensional parameter ? related to the depth and we use asymptotic analysis to study what happens when ? becomes small.Usually, when asymptotics are used to analyze fluids, they are used in the original domain or the surface is supposed

José M. Rodríguez; Raquel Taboada-Vázquez

2008-01-01

46

Depth dose distributions measured with thermoluminescence detectors inside the anthropomorphic torso of the MATROSHKA experiment inside and outside the ISS  

NASA Astrophysics Data System (ADS)

The ESA MATROSHKA (MTR) facility was realized through the German Aerospace Center, DLR, Cologne, as main contractor, aiming for the determination of skin and organ doses within a simulated human upper torso. MTR simulates, by applying an anthropomorphic upper torso, as exact as possible an astronaut performing either an extravehicular activity (EVA) (MTR Phase 1) or an astronaut working inside the International Space Station (MTR Phase 2A). It consists of a human phantom, a Base Structure and a Carbon fibre container - simulating the astronaut‘s space suit. The phantom itself is made up of 33 slices composed of natural bones, embedded in tissue equivalent plastic of different density for tissue and lung. The Phantom slices are equipped with channels and cut-outs to allow the accommodation of active and passive dosemeters, temperature and pressure sensors. Over 4800 passive detectors (thermoluminescence detectors (TLDs) and plastic nuclear track detectors) constitute the radiation experiments which are beside inside the phantom also located on top the head of the phantom, in front of the belly and around the body as part of a Poncho and a Hood. In its 1st exposure phase (MTR 1: 2004 - 2005) MTR measured the depth dose distribution of an astronaut performing an EVA - mounted outside the Zvezda Module. In its 2nd exposure phase the phantom was positioned inside the ISS to monitor the radiation environment and measure the depth dose distribution in dependence on the inside shielding configurations. The majority of the TLDs provided for the determination of the depth dose distribution was provided by IFJ-PAN, ATI and DLR. Data of "combined" depth dose distribution of the three different groups will be shown for the MTR-1 exposure (outside the ISS) and the MTR-2A (inside the ISS). The discussion will focus on the difference in depth dose as well as skin dose distribution based on the different shielding thickness provided by the two experimental phases.

Berger, Thomas; Reitz, Guenther; Hajek, Michael; Bergmann, Robert; Bilski, Pawel; Puchalska, Msc. Monika

47

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

E-print Network

We study the energy deposition by light and heavy nuclei in tissue-like media as used for cancer therapy. The depth-dose distributions for protons, $^{3}$He, $^{12}$C, $^{20}$Ne, and $^{58}$Ni 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 $^{3}$He. On the other hand, all projectiles up to $^{20}$Ne were found equally suitable for therapeutic use at low penetration depths.

Pshenichnov, Igor; Greiner, Walter

2007-01-01

48

Experimental determination of effects of water depth on Nymphaea odorata growth, morphology and biomass allocation  

Microsoft Academic Search

Growth, morphology and biomass allocation in response to water depth was studied in white water lily, Nymphaea odorata Aiton. Plants were grown for 13months in 30, 60 and 90cm water in outdoor mesocosms in southern Florida. Water lily plant growth was distinctly seasonal with plants at all water levels producing more and larger leaves and more flowers in the warmer

Jennifer H. Richards; Tiffany G. Troxler; David W. Lee; Michael S. Zimmerman

2011-01-01

49

A comparison of observed and analytically derived remote sensing penetration depths for turbid water  

NASA Technical Reports Server (NTRS)

The depth to which sunlight will penetrate in turbid waters was investigated. The tests were conducted in water with a single scattering albedo range, and over a range of solar elevation angles. Two different techniques were used to determine the depth of light penetration. It showed little change in the depth of sunlight penetration with changing solar elevation angle. A comparison of the penetration depths indicates that the best agreement between the two methods was achieved when the quasisingle scattering relationship was not corrected for solar angle. It is concluded that sunlight penetration is dependent on inherent water properties only.

Morris, W. D.; Usry, J. W.; Witte, W. G.; Whitlock, C. H.; Guraus, E. A.

1981-01-01

50

The Effect of Irrigation Schedules on Water Table Depth and Root Zone Soil Moisture  

E-print Network

, soil type and climatic data used for the simulations are typical of semi-arid south- eastern AustraliaThe Effect of Irrigation Schedules on Water Table Depth and Root Zone Soil Moisture 1 H. T. Nguyen-Mail: thuhien@civenv.unimelb.edu.au Keywords: Irrigation schedules; water table depth; soil moisture; root zone

Walker, Jeff

51

Testate amoebae as proxies for mean annual water-table depth in Sphagnum-dominated  

E-print Network

Testate amoebae as proxies for mean annual water-table depth in Sphagnum-dominated peatlands, Bethlehem, Pennsylvania, USA Booth, R. K. 2007. Testate amoebae as proxies for mean annual water-table depth-inhabiting testate amoebae are sensitive indicators of substrate-moisture conditions and have increasingly been used

Booth, Robert K.

52

Variations in the RBE for cell killing along the depth-dose profile of a modulated proton therapy beam.  

PubMed

Considerable evidence now exists to show that that the relative biological effectiveness (RBE) changes considerably along the proton depth-dose distribution, with progressively higher RBE values at the distal part of the modulated, or spread out Bragg peak (SOBP) and in the distal dose fall-off (DDF). However, the highly variable nature of the existing studies (with regards to cell lines, and to the physical properties and dosimetry of the various proton beams) precludes any consensus regarding the RBE weighting factor at any position in the depth-dose profile. We have thus conducted a systematic study on the variation in RBE for cell killing for two clinical modulated proton beams at Indiana University and have determined the relationship between the RBE and the dose-averaged linear energy transfer (LETd) of the protons at various positions along the depth-dose profiles. Clonogenic assays were performed on human Hep2 laryngeal cancer cells and V79 cells at various positions along the SOBPs of beams with incident energies of 87 and 200 MeV. There was a marked variation in the radiosensitivity of both cell lines along the SOBP depth-dose profile of the 87 MeV proton beam. Using Hep2 cells, the D(0.1) isoeffect dose RBE values (normalized against (60)Co) were 1.46 at the middle of SOBP, 2.1 at the distal end of the SOBP and 2.3 in the DDF. For V79 cells, the D(0.1) isoeffect RBE for the 87 MEV beam were 1.23 for the proximal end of the SOBP: 1.46 for the distal SOBP and 1.78 for the DDF. Similar D(0.1) isoeffect RBE values were found for Hep2 cells irradiated at various positions along the depth-dose profile of the 200 MeV beam. Our experimentally derived RBE values were significantly correlated (P = 0.001) with the mean LETd of the protons at the various depths, which confirmed that proton RBE is highly dependent on LETd. These in vitro data suggest that the RBE of the proton beam at certain depths is greater than 1.1, a value currently used in most treatment planning algorithms. Thus, the potential for increased cell killing and normal tissue damage in the distal regions of the proton SOBP may be greater than originally thought. PMID:23148508

Britten, Richard A; Nazaryan, Vahagn; Davis, Leslie K; Klein, Susan B; Nichiporov, Dmitri; Mendonca, Marc S; Wolanski, Mark; Nie, Xiliang; George, Jerry; Keppel, Cynthia

2013-01-01

53

Genetic Algorithms for Optimal Scheduling of Chlorine Dosing in Water  

E-print Network

oz343 Genetic Algorithms for Optimal Scheduling of Chlorine Dosing in Water Distribution Systems for determining the optimal schedule of chlorine dosing within a water distribution system considering multiple. The model is also capable of handling improved nonlinear chlorine decay algorithms by separating the genetic

Coello, Carlos A. Coello

54

DOSE CONTROLLER FOR AGUACLARA WATER TREATMENT PLANTS  

EPA Science Inventory

The expected results include a proven design for a gravity powered dose controller that works for calcium hypochlorite or aluminum sulfate solutions. The dose controller will be coupled with plant flow rate measuring systems that have compatible relationships between flow rate...

55

A quantile count model of water depth constraints on Cape Sable seaside sparrows  

USGS Publications Warehouse

1. A quantile regression model for counts of breeding Cape Sable seaside sparrows Ammodramus maritimus mirabilis (L.) as a function of water depth and previous year abundance was developed based on extensive surveys, 1992-2005, in the Florida Everglades. The quantile count model extends linear quantile regression methods to discrete response variables, providing a flexible alternative to discrete parametric distributional models, e.g. Poisson, negative binomial and their zero-inflated counterparts. 2. Estimates from our multiplicative model demonstrated that negative effects of increasing water depth in breeding habitat on sparrow numbers were dependent on recent occupation history. Upper 10th percentiles of counts (one to three sparrows) decreased with increasing water depth from 0 to 30 cm when sites were not occupied in previous years. However, upper 40th percentiles of counts (one to six sparrows) decreased with increasing water depth for sites occupied in previous years. 3. Greatest decreases (-50% to -83%) in upper quantiles of sparrow counts occurred as water depths increased from 0 to 15 cm when previous year counts were 1, but a small proportion of sites (5-10%) held at least one sparrow even as water depths increased to 20 or 30 cm. 4. A zero-inflated Poisson regression model provided estimates of conditional means that also decreased with increasing water depth but rates of change were lower and decreased with increasing previous year counts compared to the quantile count model. Quantiles computed for the zero-inflated Poisson model enhanced interpretation of this model but had greater lack-of-fit for water depths > 0 cm and previous year counts 1, conditions where the negative effect of water depths were readily apparent and fitted better with the quantile count model.

Cade, B.S.; Dong, Q.

2008-01-01

56

Bidimensional shallow water model with polynomial dependence on depth through vorticity  

Microsoft Academic Search

In this paper, we obtain a bidimensional shallow water model with polynomial dependence on depth. With this aim, we introduce a small non-dimensional parameter ? and we study three-dimensional Euler equations in a domain depending on ? (in such a way that, when ? becomes small, the domain has small depth). Then, we use asymptotic analysis to study what happens

J. M. Rodríguez; R. Taboada-Vázquez

2009-01-01

57

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.

58

Tracking water pathways in steep hillslopes by ?18O depth profiles of soil water  

NASA Astrophysics Data System (ADS)

Assessing temporal variations in soil water flow is important, especially at the hillslope scale, to identify mechanisms of runoff and flood generation and pathways for nutrients and pollutants in soils. While surface processes are well considered and parameterized, the assessment of subsurface processes at the hillslope scale is still challenging since measurement of hydrological pathways is connected to high efforts in time, money and personnel work. The latter might not even be possible in alpine environments with harsh winter processes. Soil water stable isotope profiles may offer a time-integrating fingerprint of subsurface water pathways. In this study, we investigated the suitability of soil water stable isotope (?18O) depth profiles to identify water flow paths along two transects of steep subalpine hillslopes in the Swiss Alps. We applied a one-dimensional advection-dispersion model using ?18O values of precipitation (ranging from -24.7 to -2.9‰) as input data to simulate the ?18O profiles of soil water. The variability of ?18O values with depth within each soil profile and a comparison of the simulated and measured ?18O profiles were used to infer information about subsurface hydrological pathways. The temporal pattern of ?18O in precipitation was found in several profiles, ranging from -14.5 to -4.0‰. This suggests that vertical percolation plays an important role even at slope angles of up to 46°. Lateral subsurface flow and/or mixing of soil water at lower slope angles might occur in deeper soil layers and at sites near a small stream. The difference between several observed and simulated ?18O profiles revealed spatially highly variable infiltration patterns during the snowmelt periods: The ?18O value of snow (-17.7 ± 1.9‰) was absent in several measured ?18O profiles but present in the respective simulated ?18O profiles. This indicated overland flow and/or preferential flow through the soil profile during the melt period. The applied methods proved to be a fast and promising tool to obtain time-integrated information on soil water flow paths at the hillslope scale in steep subalpine slopes.

Mueller, Matthias H.; Alaoui, Abdallah; Kuells, Christoph; Leistert, Hannes; Meusburger, Katrin; Stumpp, Christine; Weiler, Markus; Alewell, Christine

2014-11-01

59

A NEURAL NETWORK APPROACH TO DERIVING OPTICAL PROPERTIES AND DEPTHS OF SHALLOW WATERS  

E-print Network

to downwelling irradiance above the surface) spectra for shallow waters were created with a semi-analytical model base of shallow-water remote sensing reflectance by a semi-analytical model11 , which is simple1 A NEURAL NETWORK APPROACH TO DERIVING OPTICAL PROPERTIES AND DEPTHS OF SHALLOW WATERS Z. P. Lee1

Lee, Zhongping

60

GROUND-WATER CONTRIBUTION TO DOSE FROM PAST HANFORD OPERATIONS  

SciTech Connect

The Hanford Environmental Dose Reconstruction (HEOR) 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 originating 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 that draw some or all of their water from the Columbia River (riparian wells); and 4) through atmospheric deposition resulting in the contamination of a small watershed that, in turn, results in contamination of a shallow well or spring. These four pathways make up the "ground-water pathway ," which is the subject of this study. The objective of the study was to assess the extent to which the groundwater pathway contributed to radiation doses that populations or individuals may have received from past operations at Hanford. The assessment presented in this report was performed by 1) reviewing the extensive ?literature on ground water and ground-water monitoring at Hanford and 2) performing simple calculations to estimate radionuclide concentrations in ground water and the Columbia River resulting from ground-water discharge. Radiation doses that would result from exposure to this ground water and surface water were calculated. The study conclusion is that the ground-water pathways did not contribute significantly to dose. Compared with background radiation in the TriCities {300 mrem/yr), estimated doses are small: 0.02 mrem/yr effective dose equivalent from discharge of contaminated ground water to the Columbia River; 1 mrem/yr effective dose equivalent from Hanford Site wells; 11 mrem/yr effective dose equivalent from riparian wells; and 1 mrem/yr effective dose equivalent from the watershed. Because the estimated doses are so small, the recommendation is that further work on the ground-water pathway be limited to tracking ongoing ground-water studies at the Hanford Site.

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

1992-01-01

61

Temporal variations in atmospheric water vapor and aerosol optical depth determined by remote sensing  

NASA Technical Reports Server (NTRS)

By automatically tracking the sun, a four-channel solar radiometer was used to continuously measure optical depth and atmospheric water vapor. The design of this simple autotracking solar radiometer is presented. A technique for calculating the precipitable water from the ratio of a water band to a nearby nonabsorbing band is discussed. Studies of the temporal variability of precipitable water and atmospheric optical depth at 0.610, 0.8730 and 1.04 microns are presented. There was good correlation between the optical depth measured using the autotracker and visibility determined from National Weather Service Station data. However, much more temporal structure was evident in the autotracker data than in the visibility data. Cirrus clouds caused large changes in optical depth over short time periods. They appear to be the largest deleterious atmospheric effect over agricultural areas that are remote from urban pollution sources.

Pitts, D. E.; Mcallum, W. E.; Heidt, M.; Jeske, K.; Lee, J. T.; Demonbrun, D.; Morgan, A.; Potter, J.

1977-01-01

62

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

63

Sugarcane Responses to Water-Table Depth and Periodic Flood  

Technology Transfer Automated Retrieval System (TEKTRAN)

Sugarcane (Saccharum spp.) is routinely exposed to periodic floods and shallow water tables in Florida’s Everglades Agricultural Area (EAA). The purpose of this study was to examine the yields and juice quality of four sugarcane cultivars (CP 88-1762, CP 89-2143, CP 89-2376, and CP 96-1252) maintain...

64

Influence of water depth on the sound generated by air-bubble vibration in the water musical instrument  

NASA Astrophysics Data System (ADS)

We have developed a water musical instrument that generates sound by the falling of water drops within resonance tubes. The instrument can give people who hear it the healing effect inherent in the sound of water. The sound produced by falling water drops arises from air- bubble vibrations. To investigate the impact of water depth on the air-bubble vibrations, we conducted experiments at varying values of water pressure and nozzle shape. We found that air-bubble vibration frequency does not change at a water depth of 50 mm or greater. Between 35 and 40 mm, however, the frequency decreases. At water depths of 30 mm or below, the air-bubble vibration frequency increases. In our tests, we varied the nozzle diameter from 2 to 4 mm. In addition, we discovered that the time taken for air-bubble vibration to start after the water drops start falling is constant at water depths of 40 mm or greater, but slower at depths below 40 mm.

Ohuchi, Yoshito; Nakazono, Yoichi

2014-06-01

65

Dose-depth and SEU monitors for the STRV-1c satellite  

Microsoft Academic Search

Small, low power instruments have been developed to monitor total-dose and single event upsets (SEUs) in spaceborne electronics. These instruments have been designed to act as continuous monitors on the Science and Technology Research Vehicle (STRV) satellite. They will also act as monitors for other spacecraft in orbits where total dose, single event upsets (SEUs) and other single event effects

I. Thomson; A. Hartshorn; M. Brown; L. Adams; R. Nickson; A. Ng; T. Cousins; T. Jones

1998-01-01

66

Design and Verification of an Inexpensive Ultrasonic Water Depth Sensor Using Arduino  

NASA Astrophysics Data System (ADS)

A system that combines the arduino micro-controller, a Parallax PING Ultrasonic distance sensor and a secure digital card to log the data is developed to help monitor water table depths in multiple settings. Traditional methods of monitoring water table depths involve the use of a pressure transducer and expensive data loggers that cost upward of 1000. The present system is built for less than 100, with the caveat that the accuracy of the measurements is 1cm. In this laboratory study, we first build the arduino based system to monitor water table depths in a piezometer and compare these measurements to those made by a pressure transducer. Initial results show that the depth measurements are accurate in comparison to actual tape measurements. Results from this benchmarking experiment will be presented at the meeting.

Mihevc, T. M.; Rajagopal, S.

2012-12-01

67

Commissioning dose computation models for spot scanning proton beams in water for a commercially available treatment planning system  

PubMed Central

Purpose: To present our method and experience in commissioning dose models in water for spot scanning proton therapy in a commercial treatment planning system (TPS). Methods: The input data required by the TPS included in-air transverse profiles and integral depth doses (IDDs). All input data were obtained from Monte Carlo (MC) simulations that had been validated by measurements. MC-generated IDDs were converted to units of Gy?mm2/MU using the measured IDDs at a depth of 2 cm employing the largest commercially available parallel-plate ionization chamber. The sensitive area of the chamber was insufficient to fully encompass the entire lateral dose deposited at depth by a pencil beam (spot). To correct for the detector size, correction factors as a function of proton energy were defined and determined using MC. The fluence of individual spots was initially modeled as a single Gaussian (SG) function and later as a double Gaussian (DG) function. The DG fluence model was introduced to account for the spot fluence due to contributions of large angle scattering from the devices within the scanning nozzle, especially from the spot profile monitor. To validate the DG fluence model, we compared calculations and measurements, including doses at the center of spread out Bragg peaks (SOBPs) as a function of nominal field size, range, and SOBP width, lateral dose profiles, and depth doses for different widths of SOBP. Dose models were validated extensively with patient treatment field-specific measurements. Results: We demonstrated that the DG fluence model is necessary for predicting the field size dependence of dose distributions. With this model, the calculated doses at the center of SOBPs as a function of nominal field size, range, and SOBP width, lateral dose profiles and depth doses for rectangular target volumes agreed well with respective measured values. With the DG fluence model for our scanning proton beam line, we successfully treated more than 500 patients from March 2010 through June 2012 with acceptable agreement between TPS calculated and measured dose distributions. However, the current dose model still has limitations in predicting field size dependence of doses at some intermediate depths of proton beams with high energies. Conclusions: We have commissioned a DG fluence model for clinical use. It is demonstrated that the DG fluence model is significantly more accurate than the SG fluence model. However, some deficiencies in modeling the low-dose envelope in the current dose algorithm still exist. Further improvements to the current dose algorithm are needed. The method presented here should be useful for commissioning pencil beam dose algorithms in new versions of TPS in the future. PMID:23556893

Zhu, X. R.; Poenisch, F.; Lii, M.; Sawakuchi, G. O.; Titt, U.; Bues, M.; Song, X.; Zhang, X.; Li, Y.; Ciangaru, G.; Li, H.; Taylor, M. B.; Suzuki, K.; Mohan, R.; Gillin, M. T.; Sahoo, N.

2013-01-01

68

Commissioning dose computation models for spot scanning proton beams in water for a commercially available treatment planning system  

SciTech Connect

Purpose: To present our method and experience in commissioning dose models in water for spot scanning proton therapy in a commercial treatment planning system (TPS). Methods: The input data required by the TPS included in-air transverse profiles and integral depth doses (IDDs). All input data were obtained from Monte Carlo (MC) simulations that had been validated by measurements. MC-generated IDDs were converted to units of Gy mm{sup 2}/MU using the measured IDDs at a depth of 2 cm employing the largest commercially available parallel-plate ionization chamber. The sensitive area of the chamber was insufficient to fully encompass the entire lateral dose deposited at depth by a pencil beam (spot). To correct for the detector size, correction factors as a function of proton energy were defined and determined using MC. The fluence of individual spots was initially modeled as a single Gaussian (SG) function and later as a double Gaussian (DG) function. The DG fluence model was introduced to account for the spot fluence due to contributions of large angle scattering from the devices within the scanning nozzle, especially from the spot profile monitor. To validate the DG fluence model, we compared calculations and measurements, including doses at the center of spread out Bragg peaks (SOBPs) as a function of nominal field size, range, and SOBP width, lateral dose profiles, and depth doses for different widths of SOBP. Dose models were validated extensively with patient treatment field-specific measurements. Results: We demonstrated that the DG fluence model is necessary for predicting the field size dependence of dose distributions. With this model, the calculated doses at the center of SOBPs as a function of nominal field size, range, and SOBP width, lateral dose profiles and depth doses for rectangular target volumes agreed well with respective measured values. With the DG fluence model for our scanning proton beam line, we successfully treated more than 500 patients from March 2010 through June 2012 with acceptable agreement between TPS calculated and measured dose distributions. However, the current dose model still has limitations in predicting field size dependence of doses at some intermediate depths of proton beams with high energies. Conclusions: We have commissioned a DG fluence model for clinical use. It is demonstrated that the DG fluence model is significantly more accurate than the SG fluence model. However, some deficiencies in modeling the low-dose envelope in the current dose algorithm still exist. Further improvements to the current dose algorithm are needed. The method presented here should be useful for commissioning pencil beam dose algorithms in new versions of TPS in the future.

Zhu, X. R.; Poenisch, F.; Lii, M.; Sawakuchi, G. O.; Titt, U.; Bues, M.; Song, X.; Zhang, X.; Li, Y.; Ciangaru, G.; Li, H.; Taylor, M. B.; Suzuki, K.; Mohan, R.; Gillin, M. T.; Sahoo, N. [Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, Texas 77030 (United States)

2013-04-15

69

Characterizing scale specific depth persistence of soil water content along two landscape transects  

NASA Astrophysics Data System (ADS)

Information on depth persistence of soil water content (SWC) is useful for adopting data assimilation techniques in integrating remote sensing data and soil water modeling. The objective of this study was to investigate the scale- and season-specific depth persistence of 0-1.0 m SWC distribution in two transects (having different soils and plant cover) in a watershed on the Chinese Loess Plateau, by combining multivariate empirical mode decomposition (MEMD) with Spearman's rank correlation analysis. Three or four intrinsic mode functions (IMFs) representing specific scales were separated out for SWC of each soil layer. The dominant scales in terms of explaining the spatial variance of SWC for Transect 1 were about 376 m (IMF1) and 677 m (IMF2), and those for Transect 2 were about 639 m (IMF2) and 1304 m (IMF3). Depth persistence of SWC varied with scale, and was the strongest at the dominant scales. The multi-scale depth persistence was weaker along Transect 1 than along Transect 2 due to the higher degree of landscape fragmentation resulting from greater human activity along Transect 1. Weaker depth persistence at each scale was mainly observed at wet conditions for Transect 1. Strong season-related depth persistence was also mainly observed at the dominant scales for both transects. The results of this study are useful for developing sampling strategies for soil water measurements, since information about depth persistence reduces the efforts involved in measuring SWC in deeper layers.

She, Dongli; Tang, Shengqiang; Shao, Ming'an; Yu, Shuang'en; Xia, Yongqiu

2014-11-01

70

ITAR: A modified TAR method to determine depth dose distribution for an ophthalmic device that performs kilovoltage x-ray pencil-beam stereotaxy  

SciTech Connect

Purpose: New technology has been developed to treat age-related macular degeneration (AMD) using 100 kVp pencil-beams that enter the patient through the radio-resistant sclera with a depth of interest between 1.6 and 2.6 cm. Measurement of reference and relative dose in a kilovoltage x-ray beam with a 0.42 cm diameter field size and a 15 cm source to axis distance (SAD) is a challenge that is not fully addressed in current guidelines to medical physicists. AAPM's TG-61 gives dosimetry recommendations for low and medium energy x-rays, but not all of them are feasible to follow for this modality. Methods: An investigation was conducted to select appropriate equipment for the application. PTW's Type 34013 Soft X-Ray Chamber (Freiburg, Germany) and CIRS's Plastic Water LR (Norfolk, VA) were found to be the best available options. Attenuation curves were measured with minimal scatter contribution and thus called Low Scatter Tissue Air Ratio (LSTAR). A scatter conversion coefficient (C{sub scat}) was derived through Monte Carlo radiation transport simulation using MCNPX (LANL, Los Alamos, NM) to quantify the difference between a traditional TAR curve and the LSTAR curve. A material conversion coefficient (C{sub mat}) was determined through experimentation to evaluate the difference in attenuation properties between water and Plastic Water LR. Validity of performing direct dosimetry measurements with a source to detector distance other than the treatment distance, and therefore a different field size due to a fixed collimator, was explored. A method—Integrated Tissue Air Ratio (ITAR)—has been developed that isolates each of the three main radiological effects (distance from source, attenuation, and scatter) during measurement, and integrates them to determine the dose rate to the macula during treatment. Results: LSTAR curves were determined to be field size independent within the range explored, indicating that direct dosimetry measurements may be performed with a source to detector distance of 20 cm even though the SAD is 15 cm during treatment. C{sub scat} varied from 1.102 to 1.106 within the range of depths of interest. The experimental variance among repeated measurements of C{sub mat} was larger than depth dependence, so C{sub mat} was estimated as1.019 for all depths of interest. Conclusions: Equipment selection, measurement techniques, and formalism for the determination of dose rate to the macula during stereotaxy for AMD have been determined and are strongly recommended by the authors of this paper to be used by clinical medical physicists.

Hanlon, Justin, E-mail: jhanlon@orayainc.com; Chell, Erik; Firpo, Michael; Koruga, Igor [Oraya Therapeutics, Inc., Newark, California 94560 (United States)] [Oraya Therapeutics, Inc., Newark, California 94560 (United States)

2014-02-15

71

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

72

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...

73

Experiments on Vertical Turbulent Plane Jets in Water of Finite Depth  

Microsoft Academic Search

Detailed experiments on vertical turbulent plane jets in water of finite depth were carried out in a two-dimensional water tank. The jet velocities were measured with a laser Doppler velocimeter (LDV). The LDV measurement covers the entire flow regime: the zone of flow establishment (ZFE), the zone of established flow (ZEF), the zone of surface impingement (ZSI), and the zone

Jun Kuang; Chin-Tsau Hsu; Huihe Qiu

2001-01-01

74

Predation risk of age-0 cod ( Gadus) relative to depth and substrate in coastal waters  

Microsoft Academic Search

Among individuals of a species, mean size in fishes increases with depth in the marine environment according to Heincke's Law. Atlantic cod (Gadus morhua L.), like many young fish, are distributed in shallow (<10 m) coastal water through much of their range as young juveniles (age 0) and deeper water as they grow. We tested the hypothesis that juvenile cod

Janice E Linehan; Robert S Gregory; David C Schneider

2001-01-01

75

FREE-WATER DEPTH AS A MANAGEMENT TOOL FOR CONSTRUCTED WETLANDS  

EPA Science Inventory

Marsh plants in constructed wetlands have shown the capacity to remove unwanted pollutants from storm water runoff. The plants can be established at the site from bare roots. However, plant growth from bare roots can be restricted by the elevated water depths. Using several wa...

76

A study on the spectral models for waves in finite water depth  

NASA Technical Reports Server (NTRS)

From an extension of the Wallops Spectrum (Huang et al., 1981) for the deep water waves, spectral models for waves in finite water depths are developed. Stokes wave expansions are found to offer a good approximation for intermediate water depth. The spectral function in this case is controlled by three parameters: the significant slope, the nondimensional depth, and the peak frequency. It is pointed out that solitary and cnoidal wave models must be used for the shallow water waves. The controlling parameters now reduce to the Urell number and the peak frequency. Even though the resulting spectral models place special emphasis on the energy-containing range of the spectrum, they are not limited to this range and they are not limited to any particular sea state. They are seen as offering a possible explanation of the variations in the special slope observed by previous investigators.

Huang, N. E.; Long, S. R.; Hwang, P. A.; Wang, H.; Bliven, L. F.

1983-01-01

77

Depth Dose Distribution Study within a Phantom Torso after Irradiation with a Simulated Solar Particle Event at NSRL  

NASA Technical Reports Server (NTRS)

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 compounded by the interactions of the primary particles with the atoms of the structural materials and with the body itself Astronauts' radiation exposures are measured by means of personal dosimetry, but there remains substantial uncertainty associated with the computational extrapolation of skin dose to organ dose, which can lead to over- or underestimation of the health risk. Comparisons of models to data showed that the astronaut's Effective dose (E) can be predicted to within about a +10% accuracy using space radiation transport models for galactic cosmic rays (GCR) and trapped radiation behind shielding. However for solar particle event (SPE) with steep energy spectra and for extra-vehicular activities on the surface of the moon where only tissue shielding is present, transport models predict that there are large differences in model assumptions in projecting organ doses. Therefore experimental verification of SPE induced organ doses may be crucial for the design of lunar missions. In the research experiment "Depth dose distribution study within a phantom torso" at the NASA Space Radiation Laboratory (NSRL) at BNL, Brookhaven, USA the large 1972 SPE spectrum was simulated using seven different proton energies from 50 up to 450 MeV. A phantom torso constructed of natural bones and realistic distributions of human tissue equivalent materials, which is comparable to the torso of the MATROSHKA phantom currently on the ISS, was equipped with a comprehensive set of thermoluminescence detectors and human cells. The detectors are applied to assess the depth dose distribution and radiation transport codes (e.g. GEANT4) are used to assess the radiation field and interactions of the radiation field with the phantom torso. Lymphocyte cells are strategically embedded at selected locations at the skin and internal organs and are processed after irradiation to assess the effects of shielding on the yield of chromosome damage. The initial focus of the present experiment is to correlate biological results with physical dosimetry measurements in the phantom torso. Further on, the results of the passive dosimetry within the anthropomorphic phantoms represent the best tool to generate reliable data to benchmark computational radiation transport models in a radiation field of interest. The presentation will give first results of the physical dose distribution, the comparison with GEANT4 computer simulations based on a Voxel model of the phantom, and a comparison with the data from the chromosome aberration study.

Berger, Thomas; Matthiae, Daniel; Koerner, Christine; George, Kerry; Rhone, Jordan; Cucinotta, Francis; Reitz, Guenther

2010-01-01

78

Estimation of radiation dose at various depths for commonly used radionuclides in radiosynoviorthesis in a tissue equivalent material.  

PubMed

The purpose of the paper is to report on the dose estimation studies at various depths for the commonly used beta-emitting 90Y, 166Ho, 153Sm, 32p, and 177Lu radionuclides in a phantom fabricated using the poly methyl methacrylate tissue equivalent material having a density of 1.19 gm/cc, by using thermoluminescent dosemeters. GAFChromic MD-55 films were used to calculate the calibration factor for the thermoluminescent micro-rods used in our study. It is observed that 90Y delivers the highest dose at 1 mm amongst the radionuclides tested followed by 32p, 166Ho, 153Sm, and 177Lu, whereas the cumulative dose received by the joint was found to be more for 32P followed by 90Y, 166Ho, 153Sm, and 177Lu. The highest therapeutic range obtained is 3.1 mm for 153Sm amongst the tested radionuclides. The dose values obtained for all the above-mentioned radionuclides can serve as reference material for those researchers and clinicians who are interested in selection of the radionuclide for the type of joint treated and the amount of dose necessary to be delivered to the synovial membrane. PMID:16964849

Tandon, Pankaj; Malpani, B L; Venkatesh, Meera; Bhatt, B C

2006-08-01

79

Estimation of radiation dose at various depths for commonly used radionuclides in radiosynoviorthesis in a tissue equivalent material  

SciTech Connect

The purpose of the paper is to report on the dose estimation studies at various depths for the commonly used beta-emitting {sup 90}Y, {sup 166}Ho, {sup 153}Sm, {sup 32}P, and {sup 177}Lu radionuclides in a phantom fabricated using the poly methyl methacrylate tissue equivalent material having a density of 1.19 gm/cc, by using thermoluminescent dosemeters. GAFChromic MD-55 films were used to calculate the calibration factor for the thermoluminescent micro-rods used in our study. It is observed that {sup 90}Y delivers the highest dose at 1 mm amongst the radionuclides tested followed by {sup 32}P, {sup 166}Ho, {sup 153}Sm, and {sup 177}Lu, whereas the cumulative dose received by the joint was found to be more for {sup 32}P followed by {sup 90}Y, {sup 166}Ho, {sup 153}Sm, and {sup 177}Lu. The highest therapeutic range obtained is 3.1 mm for {sup 153}Sm amongst the tested radionuclides. The dose values obtained for all the above-mentioned radionuclides can serve as reference material for those researchers and clinicians who are interested in selection of the radionuclide for the type of joint treated and the amount of dose necessary to be delivered to the synovial membrane.

Tandon, Pankaj; Malpani, B. L.; Venkatesh, Meera; Bhatt, B. C. [Radiological Physics and Advisory Division, Bhabha Atomic Research Centre, CT and CRS Building, Anushaktinagar, Mumbai, 400 094 (India); Radiation Medicine Centre, Bhabha Atomic Research Centre, CT and CRS Building, Anushaktinagar, Mumbai, 400 094 (India); Radiopharmaceutical Division, Bhabha Atomic Research Centre, CT and CRS Building, Anushaktinagar, Mumbai, 400 094 (India); Radiological Physics and Advisory Division, Bhabha Atomic Research Centre, CT and CRS Building, Anushaktinagar, Mumbai, 400 094 (India)

2006-08-15

80

Resistance to Water Diffusion in the Stratum Corneum Is Depth-Dependent  

PubMed Central

The stratum corneum (SC) provides a permeability barrier that limits the inflow and outflow of water. The permeability barrier is continuously and dynamically formed, maintained, and degraded along the depth, from the bottom to the top, of the SC. Naturally, its functioning and structure also change dynamically in a depth-dependent manner. While transepidermal water loss is typically used to assess the function of the SC barrier, it fails to provide any information about the dynamic mechanisms that are responsible for the depth-dependent characteristics of the permeability barrier. This paper aims to quantitatively characterize the depth-dependency of the permeability barrier using in vivo non-invasive measurement data for understanding the underlying mechanisms for barrier formation, maintenance, and degradation. As a framework to combine existing experimental data, we propose a mathematical model of the SC, consisting of multiple compartments, to explicitly address and investigate the depth-dependency of the SC permeability barrier. Using this mathematical model, we derive a measure of the water permeability barrier, i.e. resistance to water diffusion in the SC, from the measurement data on transepidermal water loss and water concentration profiles measured non-invasively by Raman spectroscopy. The derived resistance profiles effectively characterize the depth-dependency of the permeability barrier, with three distinct regions corresponding to formation, maintenance, and degradation of the barrier. Quantitative characterization of the obtained resistance profiles allows us to compare and evaluate the permeability barrier of skin with different morphology and physiology (infants vs adults, different skin sites, before and after application of oils) and elucidates differences in underlying mechanisms of processing barriers. The resistance profiles were further used to predict the spatial-temporal effects of skin treatments by in silico experiments, in terms of spatial-temporal dynamics of percutaneous water penetration. PMID:25671323

van Logtestijn, Mark D. A.; Domínguez-Hüttinger, Elisa; Stamatas, Georgios N.; Tanaka, Reiko J.

2015-01-01

81

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

82

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

NASA Astrophysics Data System (ADS)

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 itself. Astronauts' radiation exposures are measured by means of personal dosimetry, but there remains substantial uncertainty associated with the computational extrap-olation of skin dose to organ dose, which can lead to over-or under-estimation of the health risk. Comparisons of models to data showed that the astronaut's Effective dose (E) can be pre-dicted to within about a +10In the research experiment "Depth dose distribution study within a phantom torso" at the NASA Space Radiation Laboratory (NSRL) at BNL, Brookhaven, USA the large 1972 SPE spectrum was simulated using seven different proton energies from 50 up to 450 MeV. A phantom torso constructed of natural bones and realistic distributions of human tissue equivalent materials, which is comparable to the torso of the MATROSHKA phantom currently on the ISS, was equipped with a comprehensive set of thermoluminescence detectors and human cells. The detectors are applied to assess the depth dose distribution and radiation transport codes (e.g. GEANT4) are used to assess the radiation field and interactions of the radiation field with the phantom torso. Lymphocyte cells are strategically embedded at selected locations at the skin and internal organs and are processed after irradiation to assess the effects of shielding on the yield of chromosome damage. The first focus of the pre-sented experiment is to correlate biological results with physical dosimetry measurements in the phantom torso. Further on the results of the passive dosimetry using the anthropomorphic phantoms represent the best tool to generate reliable to benchmark computational radiation transport models in a radiation field of interest. The presentation will give first results of the physical dose distribution, the comparison with GEANT4 computer simulations, based on a Voxel model of the phantom, and a comparison with the data from the chromosome aberration study. The help and support of Adam Russek and Michael Sivertz of the NASA Space Radiation Laboratory (NSRL), Brookhaven, USA during the setup and the irradiation of the phantom are highly appreciated. The Voxel model describing the human phantom used for the GEANT4 simulations was kindly provided by Monika Puchalska (CHALMERS, Gothenburg, Sweden).

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

83

Effects of irrigation system management turnover on water table depth and salinity of groundwater.  

PubMed

In recent years, management of large, state owned irrigation projects in Turkey have been transferred to water users such as farmers cooperatives or associations in order to reduce the financial burden on the government and to increase irrigation efficiency and farmer participation. Water table depth and groundwater salinity are important factors in irrigation systems, not only for plant growth but for human health as well. The objective of this study was to determine the impact on water table depth and groundwater salinity for transferring management of the Mustafakemalpasa irrigation project (19,370 ha) in north-western Turkey to local, farmer controlled irrigation districts. Maps of water table depth and groundwater salinity were created for the month of July (averaged over several years), the month with the highest amount of applied irrigation water, based on measurements made in 200 wells in the project area before and after transfer of managerial control. Both depth of the water table and salinity decreased after transfer The area with average water table depth of 100-200 cm was 25.41% of total area before turnover and 79.45% after, and the area with water table depth 200-300 cm was 73.84% before turnover and 20.50% after Before turnover; the area with average groundwater salinity 1.5-2.0 dS/m was 26.16% of total area, and that with average salinity 2.0-2.5 dS/m was 61.73% of total area; after turnover, average groundwater salinity was 1.5-2.0 dS/m in over all areas. Both changes were the consequence of an increased amount of applied water after transfer of the control of irrigation management from the state to local irrigation districts controlled by farmers. In the short run, the farmers will get benefit from increased irrigation. However over the long term, if water table depth continues to decrease then secondary salinization could become a major hindrance to irrigation sustainability PMID:17929765

Gundogdu, Kemal Sulhi; Aslan, S Tulin Akkay

2007-04-01

84

Nest survival of American Coots relative to grazing, burning, and water depths  

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 water-level 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 land-management 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.

Austin, Jane E.; Buhl, Deborah A.

2011-01-01

85

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

86

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

PubMed

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. PMID:19125926

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

1999-01-01

87

Investigation of Dose Depth Distribution in Human Phantom on Russian Segment of ISS for Estimation of Radiation Risk during Long Term Space Flight  

Microsoft Academic Search

Described is the Liulin-5 active experiment for investigation of the space radiation doses depth distribution in a human phantom on the Russian segment of the International Space Station (ISS). Liulin-5 experiment is a part of the international project MATROSHKA-R on ISS. The experiment MATROSHKA-R is aimed to study the depth dose distribution at the sites of critical organs of the

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

2002-01-01

88

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

89

Bottom depth and type for shallow waters: Hyperspectral observations from a blimp  

SciTech Connect

In a study of a blimp transect over Tampa Bay (Florida), hyperspectral upwelling radiance over the sand and seagrass bottoms was measured. These measurements were converted to hyperspectral remote-sensing reflectances. Using a shallow-water remote-sensing-reflectance model, in-water optical properties, bottom depths and bottom albedos were derived analytically and simultaneously by an optimization procedure. In the process, curvatures of sand and seagrass albedos were used. Also used was a model of absorption spectrum of phytoplankton pigments. The derived bottom depths were compared with bathymetry charts and found to agree well. This study suggests that a low-flying blimp is a useful platform for the study and mapping of coastal water environments. The optical model as well as the data-reduction procedure used are practical for the retrieval of shallow water optical properties.

Lee, ZhongPing; Carder, K.; Steward, R. [Univ. of South Florida, St. Petersburg, FL (United States)] [and others

1997-08-01

90

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...

91

Comparison of shallow water table depth algorithms used in SWAT2005  

Technology Transfer Automated Retrieval System (TEKTRAN)

The fluctuation of the shallow water table depth (WTD) is important for planning drainage systems at the plot-, field-, and watershed-scale because its proximity to the ground surface impacts farm machine trafficability, crop development, agricultural chemical transport, soil salinity, and drainage....

92

Morphology, growth and carbohydrate storage of the plant Typha angustifolia at different water depths  

Microsoft Academic Search

Morphological characteristics, growth and carbohydrate storage dynamics of Typha angustifolia in relation to water depth were investigated. The study was based on observations carried out in two stands, namely Akigase and Teganuma, for two growth seasons. The latter stand was about two times deeper than the former. Teganuma stands exhibited significantly higher number of thick shoots compared to those of

P. Sharma; T. Asaeda; M. Kalibbala; T. Fujino

2008-01-01

93

QUALITY OF WATERS FOUND AT DEPTH WITHIN A LOESS-HILLS AGRICULTURAL LANDSCAPE  

Technology Transfer Automated Retrieval System (TEKTRAN)

Concerns about nitrate-N in ground waters of Midwest agricultural watersheds have increased in recent years. We installed a transect of multi-depth piezometers and lysimeters in each of two adjacent first-order watersheds in the loess hills of southwest Iowa, and monitored NO3-N concentrations each ...

94

Incorporation of a new shallow water table depth algorithm into SWAT 2005  

Technology Transfer Automated Retrieval System (TEKTRAN)

The fluctuation of the shallow water table depth (WTD) is important for planning drainage systems at the plot-, field-, and watershed-scale because its proximity to the surface impacts farm machine trafficability, crop development, agricultural chemical transport, soil salinity, and drainage. Theref...

95

One-hydrophone method of estimating distance and depth of phonating dolphins in shallow water  

E-print Network

is a fundamental param- eter necessary to gain insight about dolphin echolocation and social behavior in the wildOne-hydrophone method of estimating distance and depth of phonating dolphins in shallow water Hawaiian spinner dolphins Stenella longirostris at the Waianae coast of Oahu, Hawaii, were localized over

96

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

97

Influences of water depth and substrate nitrogen on leaf surface area and maximum bed extension in Nymphaea odorata  

Microsoft Academic Search

Relationships among water depth, substrate nitrogen, and leaf surface area in the floating-leaved macrophyte Nymphaea odorata Aiton (fragrant waterlily) were studied in seven ponds in Rhode Island, USA. Beds of N. odorata in ponds that varied three- to seven-fold in depth, total area, water-column phosphorus and nitrogen, transparency, and chlorophyll content grew to strikingly similar water depth maxima (1.9–2.2 m;

M. Sinden-Hempstead; K. T. Killingbeck

1996-01-01

98

Depth dose dependence of the mouse bone using kilovoltage photon beams: A Monte Carlo study for small-animal irradiation  

Microsoft Academic Search

This study investigated the dose enhancement due to the presence of mouse bone irradiated by the kilovoltage (kV) photon beams. Dosimetry of the bone associated with soft and lung tissue was determined by Monte Carlo simulations using the EGSnrc-based code in millimeter scale. Two inhomogeneous phantoms with 2mm of bone layer sandwiched by: (1) water and lung (bone–lung phantom); and

James C. L. Chow

2010-01-01

99

Depth dose dependence of the mouse bone using kilovoltage photon beams: A Monte Carlo study for small-animal irradiation  

Microsoft Academic Search

This study investigated the dose enhancement due to the presence of mouse bone irradiated by the kilovoltage (kV) photon beams. Dosimetry of the bone associated with soft and lung tissue was determined by Monte Carlo simulations using the EGSnrc-based code in millimeter scale. Two inhomogeneous phantoms with 2 mm of bone layer sandwiched by: (1) water and lung (bone-lung phantom);

James C. L. Chow

2010-01-01

100

Reverse evolution in RH1 for adaptation of cichlids to water depth in Lake Tanganyika.  

PubMed

Reverse evolution is a widespread phenomenon in biology, but the genetic mechanism for the reversal of a genetic change for adaptation to the ancestral state is not known. Here, we report the first case of complete reverse evolution of two amino acids, serine and alanine, at a single position in RH1 opsin pigment for adaptation to water depth. We determined RH1 sequences of cichlid fishes from four tribes of Lake Tanganyika with different habitat depths. Most of the species were divided into two types: RH1 with 292A for species in shallow water or 292S for species in deep water. Both types were adapted to their ambient light environments as indicated by the absorption spectra of the RH1 pigments. Based on the RH1 locus tree and ecological data, we inferred the ancestral amino acids at position 292 and the distribution of the depth ranges (shallow or deep) of ancestral species of each tribe. According to these estimates, we identified two distinct parallel adaptive evolutions: The replacement A292S occurred at least four times for adaptation from shallow to deep water, and the opposite replacement S292A occurred three times for adaptation from deep to shallow water. The latter parallelism represents the complete reverse evolution from the derived to the ancestral state, following back adaptive mutation with reversal of the RH1 pigment function accompanied by reversal of the species habitat shift. PMID:21172834

Nagai, Haruka; Terai, Yohey; Sugawara, Tohru; Imai, Hiroo; Nishihara, Hidenori; Hori, Michio; Okada, Norihiro

2011-06-01

101

(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

2012-08-01

102

Optimal design of equivalent water depth truncated mooring system based on baton pattern simulated annealing algorithm  

NASA Astrophysics Data System (ADS)

The highest similarity degree of static characteristics including both horizontal and vertical restoring force-displacement characteristics of total mooring system, as well as the tension-displacement characteristics of the representative single mooring line between the truncated and full depth system are obtained by annealing simulation algorithm for hybrid discrete variables (ASFHDV, in short). A "baton" optimization approach is proposed by utilizing ASFHDV. After each baton of optimization, if a few dimensional variables reach the upper or lower limit, the boundary of certain dimensional variables shall be expanded. In consideration of the experimental requirements, the length of the upper mooring line should not be smaller than 8 m, and the diameter of the anchor chain on the bottom should be larger than 0.03 m. A 100000 t turret mooring FPSO in the water depth of 304 m, with the truncated water depth being 76 m, is taken as an example of equivalent water depth truncated mooring system optimal design and calculation, and is performed to obtain the conformation parameters of the truncated mooring system. The numerical results indicate that the present truncated mooring system design is successful and effective.

Zhang, Huo-ming; Huang, Sai-hua; Guan, Wei-bing

2014-03-01

103

Changes in late-winter snowpack depth, water equivalent, and density in Maine, 1926-2004  

USGS Publications Warehouse

Twenty-three snow-course sites in and near Maine, USA, with records spanning at least 50 years through to 2004 were tested for changes over time in snowpack depth, water equivalent, and density in March and April. Of the 23 sites, 18 had a significant decrease (Mann-Kendall test, p < 0??1) in snowpack depth or a significant increase in snowpack density over time. Data from four sites in the mountains of western Maine-northern New Hampshire with mostly complete records from 1926 to 2004 indicate that average snowpack depths have decreased by about 16% and densities have increased by about 11%. Average snowpack depths and water equivalents in western Maine-northern New Hampshire peaked in the 1950s and 1960s, and densities peaked in the most recent decade. Previous studies in western North America also found a water-equivalent peak in the third quarter of the 20th century. Published in 2006 by John Wiley & Sons, Ltd.

Hodgkins, G.A.; Dudley, R.W.

2006-01-01

104

Factors for converting dose measured in polystyrene phantoms to dose reported in water phantoms for incident proton beams  

SciTech Connect

Purpose: Previous dosimetry protocols allowed calibrations of proton beamline dose monitors to be performed in plastic phantoms. Nevertheless, dose determinations were referenced to absorbed dose-to-muscle or absorbed dose-to-water. The IAEA Code of Practice TRS 398 recommended that dose calibrations be performed with ionization chambers only in water phantoms because plastic-to-water dose conversion factors were not available with sufficient accuracy at the time of its writing. These factors are necessary, however, to evaluate the difference in doses delivered to patients if switching from calibration in plastic to a protocol that only allows calibration in water. Methods: This work measured polystyrene-to-water dose conversion factors for this purpose. Uncertainties in the results due to temperature, geometry, and chamber effects were minimized by using special experimental set-up procedures. The measurements were validated by Monte Carlo simulations. Results: At the peak of non-range-modulated beams, measured polystyrene-to-water factors ranged from 1.015 to 1.024 for beams with ranges from 36 to 315 mm. For beams with the same ranges and medium sized modulations, the factors ranged from 1.005 to 1.019. The measured results were used to generate tables of polystyrene-to-water dose conversion factors. Conclusions: The dose conversion factors can be used at clinical proton facilities to support beamline and patient specific dose per monitor unit calibrations performed in polystyrene phantoms.

Moyers, M. F.; Vatnitsky, A. S.; Vatnitsky, S. M. [Loma Linda University Medical Center, Loma Linda, California 92354 (United States); Guthrie Clinic/Robert Packard Hospital, Sayre, Pennsylvania 18840 (United States); EBG MedAustron, Wiener Neustadt, Austria A2700 (Austria)

2011-10-15

105

Arsenic-related water quality with depth and water quality of well-head samples from production wells, Oklahoma, 2008  

USGS Publications Warehouse

The U.S. Geological Survey well profiler was used to describe arsenic-related water quality with well depth and identify zones yielding water with high arsenic concentrations in two production wells in central and western Oklahoma that yield water from the Permian-aged Garber-Wellington and Rush Springs aquifers, respectively. In addition, well-head samples were collected from 12 production wells yielding water with historically large concentrations of arsenic (greater than 10 micrograms per liter) from the Garber-Wellington aquifer, Rush Springs aquifer, and two minor aquifers: the Arbuckle-Timbered Hills aquifer in southern Oklahoma and a Permian-aged undefined aquifer in north-central Oklahoma. Three depth-dependent samples from a production well in the Rush Springs aquifer had similar water-quality characteristics to the well-head sample and did not show any substantial changes with depth. However, slightly larger arsenic concentrations in the two deepest depth-dependent samples indicate the zones yielding noncompliant arsenic concentrations are below the shallowest sampled depth. Five depth-dependent samples from a production well in the Garber-Wellington aquifer showed increases in arsenic concentrations with depth. Well-bore travel-time information and water-quality data from depth-dependent and well-head samples showed that most arsenic contaminated water (about 63 percent) was entering the borehole from perforations adjacent to or below the shroud that overlaid the pump. Arsenic concentrations ranged from 10.4 to 124 micrograms per liter in 11 of the 12 production wells sampled at the well head, exceeding the maximum contaminant level of 10 micrograms per liter for drinking water. pH values of the 12 well-head samples ranged from 6.9 to 9. Seven production wells in the Garber-Wellington aquifer had the largest arsenic concentrations ranging from 18.5 to 124 micrograms per liter. Large arsenic concentrations (10.4-18.5) and near neutral to slightly alkaline pH values (6.9-7.4) were detected in samples from one well in the Garber-Wellington aquifer, three production wells in the Rush Springs aquifer, and one well in an undefined Permian-aged aquifer. All well-head samples were oxic and arsenate was the only species of arsenic in water from 10 of the 12 production wells sampled. Arsenite was measured above the laboratory reporting level in water from a production well in the Garber-Wellington aquifer and was the only arsenic species measured in water from the Arbuckle-Timbered Hills aquifer. Fluoride and uranium were the only trace elements, other than arsenic, that exceeded the maximum contaminant level for drinking water in well-head samples collected for the study. Uranium concentrations in four production wells in the Garber-Wellington aquifer ranged from 30.2 to 99 micrograms per liter exceeding the maximum contaminant level of 30 micrograms per liter for drinking water. Water from these four wells also had the largest arsenic concentrations measured in the study ranging from 30 to 124 micrograms

Becker, Carol J.; Smith, S. Jerrod; Greer, James R.; Smith, Kevin A.

2010-01-01

106

Depth conversion in rapidly deepening water with application to the Seychelles  

SciTech Connect

Seismic time-maps may be converted to depth by a layer-cake method where each layer above the horizon of interest is given an interval velocity obtained from wells, from velocity analyses, or estimated from lithology. Using constant or laterally varying interval velocities and ignoring vertical changes of velocity within the layers can introduce serious errors: For instance, shallow faults may project downwards causing spurious lineations on deeper maps (Davis, 1990). Such errors can be reduced by using velocity functions for the individual layers. Similar errors that occur due to rapid variations in water-depth may be reduced by allowing the instantaneous velocity in the layer below the seabed to increase with depth. These principles were applied to a structure underlying the Constant Bank, a carbonate shoal in the southern part of the Seychelles Bank.

Davis, B.K. [Davis (Barrie K.), London (United Kingdom); Binks, R. [Enterprise Oil, London (United Kingdom)

1994-12-31

107

A weighted surface-depth gradient method for the numerical integration of the 2D shallow water equations with topography  

Microsoft Academic Search

A finite volume MUSCL scheme for the numerical integration of 2D shallow water equations is presented. In the framework of the SLIC scheme, the proposed weighted surface-depth gradient method (WSDGM) computes intercell water depths through a weighted average of DGM and SGM reconstructions, in which the weight function depends on the local Froude number. This combination makes the scheme capable

F. Aureli; A. Maranzoni; P. Mignosa; C. Ziveri

2008-01-01

108

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

109

Effect of water depth on the rhizome dynamics of Typha angustifolia  

Microsoft Academic Search

The rhizome dynamics of Typha angustifolia in relation to water depth were investigated. Observations were made in two different stands, namely Akigase from April 2002\\u000a to December 2003, and Teganuma from April 2003 to December 2004. The mean rhizome length in the two stands was not significantly\\u000a different but the mean rhizome diameter and biomass showed a significant difference. The

Pratima Sharma; Takashi Asaeda; Takeshi Fujino

2008-01-01

110

Effects of Light, Temperature, and Water Depth on Growth of a Rare Aquatic Plant, Ranunculus kadzusensis  

Microsoft Academic Search

Ranunculus kadzusensis is an endangered aquatic plant species that commonly reproduces in the rice paddies of Korea and Japan during winter and\\u000a early spring. Here, we investigated the effects of main aquatic environmental factors—light, temperature, and water depth—on\\u000a its growth, with the goal of seeking information that will contribute to its in situ conservation. As the amount of shading\\u000a increased,

In Su Jo; Dong Uk Han; Yong Joo Cho; Eun Ju Lee

2010-01-01

111

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

112

Nematode assemblages from the Kandalaksha Depression (White Sea, 251-288 m water depth)  

NASA Astrophysics Data System (ADS)

The shallow-water nematodes of the White Sea are relatively well studied; however, information on the nematode fauna inhabiting the deepest part of this sea is very scarce. The composition of the nematode assemblages (at species and genus level) was studied in samples collected during four sampling occasions in the deepest part of the Kandalaksha Depression (the White Sea) in July 1998, October 1998, May 1999, and November 1999. Samples were collected from a depth of 251-288 m with the aid of a multicorer. In total, 59 nematode morphotypes belonging to 37 genera and 18 families were distinguished. The genera Sabatieria and Filipjeva dominated at all stations, followed by Aponema, Desmoscolex, and Quadricoma. The composition of the dominant genera can be considered typical for this depth range in temperate and Arctic waters, although Filipjeva and Aponema were among the dominant genera for the first time. The most abundant species were Sabatieria ornata, Aponema bathyalis, and Filipjeva filipjevi. In general, diversity of the nematode assemblages was lower than in the temperate and Arctic continental shelf and slope with reduced evenness and species richness. The evenness of nematode assemblages and other diversity indices decreased with increasing sediment depth. Based on the valid species and genera recorded, the nematode fauna of the Kandalaksha Depression showed a higher resemblance to that found in the shallow waters of Kandalaksha Bay.

Miljutin, Dmitry M.; Miljutina, Maria A.; Tchesunov, Alexei V.; Mokievsky, Vadim O.

2014-03-01

113

Hydroelasticity of a circular plate on water of finite or infinite depth  

NASA Astrophysics Data System (ADS)

This paper considers the diffraction of incident surface waves by a floating elastic circular plate. We investigate the hydroelastic response of the plate to a plane incident wave for two cases of water depth. An analytic and numerical study is presented. An integro-differential equation is derived for the problem and an algorithm of its numerical solution is proposed. The representation of the solution as series of Bessel functions is the key idea of the approach. After a brief introduction and formulation of the problem, we derive the main integro-differential equation by the use of the thin plate theory and Green's theorem. The plate deflection, the free-surface elevation and the Green's function are expressed in cylindrical coordinates as series of Bessel functions. For the coefficients, a set of algebraic equations is obtained, yielding the approximate solution for the case of infinite water depth. Then a solution is obtained for the general case of finite water depth analogously. The exact solution is approximated by taking a finite number of roots of the dispersion relation into account. Numerical results for the plate deflection, initiated wave pattern and free-surface elevation are presented for various physical parameters of the problem, together with some remarks on the computation and discussion.

Andrianov, A. I.; Hermans, A. J.

2005-07-01

114

Elemental Water Impact Test: Phase 3 Plunge Depth of a 36-Inch Aluminum Tank Head  

NASA Technical Reports Server (NTRS)

Spacecraft are being designed based on LS-DYNA water landing simulations. The Elemental Water Impact Test (EWIT) series was undertaken to assess the accuracy of LS-DYNA water impact simulations. Phase 3 featured a composite tank head that was tested at a range of heights to verify the ability to predict structural failure of composites. To support planning for Phase 3, a test series was conducted with an aluminum tank head dropped from heights of 2, 6, 10, and 12 feet to verify that the test article would not impact the bottom of the test pool. This report focuses on the comparisons of the measured plunge depths to LS-DYNA predictions. The results for the tank head model demonstrated the following. 1. LS-DYNA provides accurate predictions for peak accelerations. 2. LS-DYNA consistently under-predicts plunge depth. An allowance of at least 20% should be added to the LS-DYNA predictions. 3. The LS-DYNA predictions for plunge depth are relatively insensitive to the fluid-structure coupling stiffness.

Vassilakos, Gregory J.

2014-01-01

115

EBT2 film as a depth-dose measurement tool for radiotherapy beams over a wide range of energies and modalities  

SciTech Connect

Purpose: One of the fundamental parameters used for dose calculation is percentage depth-dose, generally measured employing ionization chambers. There are situations where use of ion chambers for measuring depth-doses is difficult or problematic. In such cases, radiochromic film might be an alternative. The EBT-2 model GAFCHROMIC film was investigated as a potential tool for depth-dose measurement in radiotherapy beams over a broad range of energies and modalities. Methods: Pieces of the EBT-2 model GAFCHROMIC EBT2 film were exposed to x-ray, electron, and proton beams used in radiotherapy. The beams employed for this study included kilovoltage x-rays (75 kVp), {sup 60}Co gamma-rays, megavoltage x-rays (18 MV), electrons (7 and 20 MeV), and pristine Bragg-peak proton beams (126 and 152 MeV). At each beam quality, film response was measured over the dose range of 0.4-8.0 Gy, which corresponds to optical densities ranging from 0.05 to 0.4 measured with a flat-bed document scanner. To assess precision in depth-dose measurements with the EBT-2 model GAFCHROMIC film, uncertainty in measured optical density was investigated with respect to variation in film-to-film and scanner-bed uniformity. Results: For most beams, percentage depth-doses measured with the EBT-2 model GAFCHROMIC film show an excellent agreement with those measured with ion chambers. Some discrepancies are observed in case of (i) kilovoltage x-rays at larger depths due to beam-hardening, and (ii) proton beams around Bragg-peak due to quenching effects. For these beams, an empirical polynomial correction produces better agreement with ion-chamber data. Conclusions: The EBT-2 model GAFCHROMIC film is an excellent secondary dosimeter for measurement of percentage depth-doses for a broad range of beam qualities and modalities used in radiotherapy. It offers an easy and efficient way to measure beam depth-dose data with a high spatial resolution.

Arjomandy, Bijan; Tailor, Ramesh; Zhao Li; Devic, Slobodan [Department of Radiation Oncology, McLaren Regional Medical Center, Flint, Michigan 48532 (United States); Department of Radiation Physics, University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 (United States); Indiana University Health Proton Therapy Center, Bloomington, Indiana 47408 (United States); Radiation Oncology Department, SMBD Jewish General Hospital, Montreal, Quebec H3T 1E2 (Canada)

2012-02-15

116

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

NASA Astrophysics Data System (ADS)

SummaryRotational 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, land management, such as changes in burning or grazing practices, has been proposed as a possible strategy for the remediation of the widespread increases in dissolved organic carbon (DOC) observed across the northern hemisphere. This study is based on a long-term experiment on the effect of different rotational burning cycles and grazing intensities on upland vegetation and aims to understand the effects of these management strategies on hydrology and water quality. The main outcomes are: The depth to water table in the soil showed significant differences between different burning rotations and grazing intensities. Depth to water table was greatest on plots where burning did not occur or for longer burning cycles where livestock had been excluded. The pH and conductivity of sampled soil water showed no significant difference between grazing treatments, with the presence of burning being the most important factor (frequency of the burning cycle was not important). The DOC content showed no significant difference between grazing treatments but showed a significant decrease with the presence of burning, though no direct relationship with the depth to water table could be found. Burn management explains only a small proportion of the variance in the composition of the DOC, rather the variation is dominated by the differences between days of sampling and seasonal variation. Therefore, this study suggests that land management controls hydrology and water quality through controlling the development of vegetation.

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

2007-06-01

117

Cetacean distribution related with depth and slope in the Mediterranean waters off southern Spain  

NASA Astrophysics Data System (ADS)

The northeastern section of the Alboran Sea is currently under consideration as a Special Area for Conservation under the European Union's Habitat Directive. Within this framework, the present study focuses on the distribution of cetaceans in this area and is part of the Spanish Ministry of the Environment's "Program for the Identification of Areas of Special Interest for the Conservation of Cetaceans in the Spanish Mediterranean". Shipboard visual surveys were conducted in 1992 and from 1995 to 2001 in the north-eastern Alboran Sea, covering 14,409 km. A total of 1,134 sightings of cetaceans were made. From the data collected, the distribution of seven species of odontocete was examined with respect to two physiographic variables, water depth and slope. Analyses of ?2 and fitting of GLMs demonstrated significant differences in distribution for all species, mainly with respect to depth. Kruskal-Wallis tests, factor analysis and discriminant function analysis showed that the species could be classified in two major groups, shallow-waters (short-beaked common dolphin and bottlenose dolphin) and deep-waters (striped dolphin, Risso's dolphin, long-finned pilot whale, sperm whale and beaked whale), respectively. Preferred habitats in terms of water depth were areas deeper than 600 m for the deep-water group, and the shallower ranges from shore to 400 m for the other. The distribution of cetaceans was further matched with that of their most common prey in order to establish which habitats could be considered important for their feeding. The resulting analysis highlighted two areas in the region as important habitats for the conservation of the most vulnerable species in the Mediterranean, the bottlenose and the common dolphin.

Cańadas, A.; Sagarminaga, R.; García-Tiscar, S.

2002-11-01

118

Determination of the dose–depth distribution of proton beam using resazurin assay in vitro and diode laser-induced fluorescence detection  

Microsoft Academic Search

In this study the dose–depth distribution pattern of proton beams was investigated by inactivation of human cells exposed to high-LET (linear energy transfer) protons. The proton beams accelerated up to 45MeV were horizontally extracted from the cyclotron, and were delivered to the cells acutely through a home made prototype over a range of physical depths (in the form of a

Min Jung Kim; Sukdeb Pal; Yu Kyung Tak; Kyeong-Hee Lee; Tae Keun Yang; Su-Jae Lee; Joon Myong Song

2007-01-01

119

Aquila field - advanced contracting strategies for the offshore development, in 850 meter water depth  

SciTech Connect

Aquila oil field is located in 850 meters of water in the middle of the Otranto Channel, in the Mediterranean Sea, at about 45 km from the shore and is subject to both difficult sea and weather conditions. The many difficulties, mainly due to the very high water depth, imposed the use of advanced technology, that could be obtained only through the direct association of contractor companies, leaders in their own field. Such a solution safeguards the technological reliability and allows the maximum control of time and cost. The selection of an FPSO (Floating, Production, Storage and Offloading) comes from a feasibility study indicating this solution as the only one, allowing the economical exploitation of the Aquila field. This paper deals with a series of technical solutions and contractual agreements with a Joint-Venture embracing two leading world contractors for developing, manufacturing and installing the FPSO {open_quotes}Agip Firenze{close_quotes}, permanently anchored at a world record 850 m water depth. The system includes flowlines and control lines. The ship, has been especially redesigned and purchased by contractors. They will use the vessel to manage the field development. Agip will provide the subsea production system: christmas tree and control system with artificial lift. The Aquila field development project aims to identify an economically viable, low risk method of producing hydrocarbons from a deep water location where previously the reserves were technologically and economically out of range.

Cerrito, E.; Ciprigno, M.

1996-12-31

120

Ocean color patterns help to predict depth of optical layers in stratified coastal waters  

NASA Astrophysics Data System (ADS)

Subsurface optical layers distributed at two different depths were investigated in Monterrey Bay, East Sound, and the Black Sea based on spatial statistics of remote sensing reflectance (Rrs). The main objective of this study was to evaluate the use of Rrs(443)/Rrs(490) (hereafter R1) skewness (?) as an indicator of vertical optical structure in different marine regions. Measurements of inherent optical properties were obtained using a remotely operated towed vehicle and R1 was theoretically derived from optical profiles. Although the broad range of trophic status and water stratification, a common statistical pattern consisting of lower ?R1--a deeper optical layer was found in all study cases. This variation was attributed to optical changes above the opticline and related to horizontal variability of particulates and spectral variations with depth. We recommend more comparisons in stratified coastal waters with different phytoplankton communities before the use of ?R1 can be generalized as a noninvasive optical proxy for screening depth changes on subsurface optical layers.

Montes-Hugo, Martín A.; Weidemann, Alan; Gould, Richard; Arnone, Robert; Churnside, James H.; Jaroz, Ewa

2011-01-01

121

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

USGS Publications Warehouse

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.

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

2001-01-01

122

[Variations in depth and chemistry of groundwater in interval of water delivery at the lower Tarim River].  

PubMed

Variations in groundwater depth and groundwater chemistry influenced by ecological water delivery in the lower Tarim River result in ecological changes. Based on the monitoring data during March, 2007 to September, 2009, the changes of both depths and chemistry of groundwater were studied. It is found that the depth of groundwater at the upper section of lower reaches increased, the major ions, such as Cl-, Na+, showed an increased change. The variations in groundwater depth in groundwater at middle section of lower Tarim River increased, and the concentrations of the major ions showed an opposite trend after the 11th water delivery. At lower section, the depths of groundwater decreased from August, 2008 till September, 2009. At the same time, the major ions in groundwater increased gradually. The groundwater depth and groundwater chemistry far away from the watercourse had a complex change. PMID:22452189

Chen, Yong-Jin; Li, Wei-Hong; Dong, Jie; Liu, Jia-Zhen

2012-01-01

123

Escape from water or remain quiescent? Lotus tenuis changes its strategy depending on depth of submergence  

PubMed Central

Background and Aims Two main strategies that allow plants to cope with soil waterlogging or deeper submergence are: (1) escaping by means of upward shoot elongation or (2) remaining quiescent underwater. This study investigates these strategies in Lotus tenuis, a forage legume of increasing importance in areas prone to soil waterlogging, shallow submergence or complete submergence. Methods Plants of L. tenuis were subjected for 30 d to well-drained (control), waterlogged (water-saturated soil), partially submerged (6 cm water depth) and completely submerged conditions. Plant responses assessed were tissue porosity, shoot number and length, biomass and utilization of water-soluble carbohydrates (WSCs) and starch in the crown. Key Results Lotus tenuis adjusted its strategy depending on the depth of submergence. Root growth of partially submerged plants ceased and carbon allocation prioritized shoot lengthening (32 cm vs. 24·5 cm under other treatments), without depleting carbohydrate reserves to sustain the faster growth. These plants also developed more shoot and root porosity. In contrast, completely submerged plants became quiescent, with no associated biomass accumulation, new shoot production or shoot elongation. In addition, tissue porosity was not enhanced. The survival of completely submerged plants is attributed to consumption of WSCs and starch reserves from crowns (concentrations 50–75 % less than in other treatments). Conclusions The forage legume L. tenuis has the flexibility either to escape from partial submergence by elongating its shoot more vigorously to avoid becoming totally submerged or to adopt a non-elongating quiescent strategy when completely immersed that is based on utilizing stored reserves. The possession of these alternative survival strategies helps to explain the success of L. tenuis in environments subjected to unpredictable flooding depths. PMID:19687031

Manzur, M. E.; Grimoldi, A. A.; Insausti, P.; Striker, G. G.

2009-01-01

124

Headgroup Immersion Depth and Its Effect on the Lateral Diffusion of Amphiphiles at the Air/Water Interface  

E-print Network

Headgroup Immersion Depth and Its Effect on the Lateral Diffusion of Amphiphiles at the Air/water interface to characterize the lateral mobilities of several long alkyl chain ferrocene amphiphiles strongly on the headgroup polarity, demonstrating that the immersion depth of the amphiphiles is the key

Majda, Marcin

125

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. PMID:23906324

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

2013-01-01

126

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

2013-08-21

127

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

Microsoft Academic Search

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. ;\\u000aIt 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

1988-01-01

128

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

129

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

NASA Astrophysics Data System (ADS)

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 detectable, even in extremely turbid and dynamic coastal waters. Here, in part 2 of this paper, we analyze the water-leaving radiance patterns of bioluminescence modeled by HydroLight 4.2 to determine if the depth of the bioluminescent source can be estimated from its spectral signature. We find that the depth of the bioluminescent source is contained within the spectral signal and can be elucidated by simple neural networks. These networks can predict the depth of a bioluminescent layer with great accuracy, solely on the basis of the spectral shape of bioluminescent water-leaving radiance in a variety of water column and bottom type conditions. In addition, we found that as little as three wavelengths from the spectrum of water-leaving radiance are sufficient for an accurate determination of the depth of the bioluminescent source.

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

2007-11-01

130

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

NASA Astrophysics Data System (ADS)

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 125I, 169Yb and 192Ir 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.

Carlsson Tedgren, Ĺsa; Alm Carlsson, Gudrun

2013-04-01

131

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

132

Large-scale regionalization of water table depth in peatlands optimized for greenhouse gas emission upscaling  

NASA Astrophysics Data System (ADS)

Fluxes of the three main greenhouse gases (GHG) CO2, CH4 and N2O from peat and other soils with high organic carbon contents are strongly controlled by water table depth. Information about the spatial distribution of water level is thus a crucial input parameter when upscaling GHG emissions to large scales. Here, we investigate the potential of statistical modeling for the regionalization of water levels in organic soils when data covers only a small fraction of the peatlands of the final map. Our study area is Germany. Phreatic water level data from 53 peatlands in Germany were compiled in a new data set comprising 1094 dip wells and 7155 years of data. For each dip well, numerous possible predictor variables were determined using nationally available data sources, which included information about land cover, ditch network, protected areas, topography, peatland characteristics and climatic boundary conditions. We applied boosted regression trees to identify dependencies between predictor variables and dip-well-specific long-term annual mean water level (WL) as well as a transformed form (WLt). The latter was obtained by assuming a hypothetical GHG transfer function and is linearly related to GHG emissions. Our results demonstrate that model calibration on WLt is superior. It increases the explained variance of the water level in the sensitive range for GHG emissions and avoids model bias in subsequent GHG upscaling. The final model explained 45% of WLt variance and was built on nine predictor variables that are based on information about land cover, peatland characteristics, drainage network, topography and climatic boundary conditions. Their individual effects on WLt and the observed parameter interactions provide insight into natural and anthropogenic boundary conditions that control water levels in organic soils. Our study also demonstrates that a large fraction of the observed WLt variance cannot be explained by nationally available predictor variables and that predictors with stronger WLt indication, relying, for example, on detailed water management maps and remote sensing products, are needed to substantially improve model predictive performance.

Bechtold, M.; Tiemeyer, B.; Laggner, A.; Leppelt, T.; Frahm, E.; Belting, S.

2014-09-01

133

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

134

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

135

Preprocessing issues associated with multiple attenuation in water depths of less than 150 meters: ISMA and predictive deconvolution  

E-print Network

Over the past three decades, marine exploration has been essentially limited to water depths within the 200-500 m range. With most reservoirs in this range depleting, exploration is moving towards very shallow water, less than 100 m, as well...

Walsh, Jeffrey Robert

2001-01-01

136

Distribution of Wading Birds Relative to Vegetation and Water Depths in the Northern Everglades of Florida, USA  

Microsoft Academic Search

The response of Great Blue Herons ( Ardea herodias ), Great Egrets ( Casmerodius albus ), Wood Storks ( Mycteria americana ), and White Ibises ( Eudocimus albus ) to water level (index of depth) and vegetation in the north- ern Everglades of Florida was studied in two years, each with dissimilar water levels. A regression model was con- structed

G. T HOMAS; D ALE E. G AWLIK; K EN R UTCHEY

137

Relationships between optical depth, liquid water path, droplet concentration and effective radius in an adiabatic layer cloud  

E-print Network

Relationships between optical depth, liquid water path, droplet concentration and effective radius. The mean volume radius rvol is defined through the relationship between droplet concentration Nd and qL: rvol = 3qL 4wNd 1/3 (3) where w is the density of liquid water. The effective radius and volume radius

Wood, Robert

138

An estimate of the influence of sediment concentration and type on remote sensing penetration depth for various coastal waters  

NASA Technical Reports Server (NTRS)

Under the assumptions of collimated light, a homogenous water column, zero molecular scattering, and constant ratio of volume scattering function to scattering coefficient, estimates of the remote sensing depth parameter, Z90, are made for various coastal waters at 540 nm. Calculations indicate that sediment concentration and type have a strong influence on remote sensing depth when concentrations are below 5 mg/theta. Above 5 mg/theta, the absorption coefficient of the sediments becomes large in comparison to that of water, causing Z90 values to be less than 2 m with only small differences between various sediment types.

Whitlock, C. H.

1976-01-01

139

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

140

Variation of Water Quality Parameters with Siltation Depth for River Ichamati Along International Border with Bangladesh Using Multivariate Statistical Techniques  

NASA Astrophysics Data System (ADS)

River is considered as one of the main sources of freshwater all over the world. Hence analysis and maintenance of this water resource is globally considered a matter of major concern. This paper deals with the assessment of surface water quality of the Ichamati river using multivariate statistical techniques. Eight distinct surface water quality observation stations were located and samples were collected. For the samples collected statistical techniques were applied to the physico-chemical parameters and depth of siltation. In this paper cluster analysis is done to determine the relations between surface water quality and siltation depth of river Ichamati. Multiple regressions and mathematical equation modeling have been done to characterize surface water quality of Ichamati river on the basis of physico-chemical parameters. It was found that surface water quality of the downstream river was different from the water quality of the upstream. The analysis of the water quality parameters of the Ichamati river clearly indicate high pollution load on the river water which can be accounted to agricultural discharge, tidal effect and soil erosion. The results further reveal that with the increase in depth of siltation, water quality degraded.

Roy, P. K.; Pal, S.; Banerjee, G.; Biswas Roy, M.; Ray, D.; Majumder, A.

2014-08-01

141

Variation of Water Quality Parameters with Siltation Depth for River Ichamati Along International Border with Bangladesh Using Multivariate Statistical Techniques  

NASA Astrophysics Data System (ADS)

River is considered as one of the main sources of freshwater all over the world. Hence analysis and maintenance of this water resource is globally considered a matter of major concern. This paper deals with the assessment of surface water quality of the Ichamati river using multivariate statistical techniques. Eight distinct surface water quality observation stations were located and samples were collected. For the samples collected statistical techniques were applied to the physico-chemical parameters and depth of siltation. In this paper cluster analysis is done to determine the relations between surface water quality and siltation depth of river Ichamati. Multiple regressions and mathematical equation modeling have been done to characterize surface water quality of Ichamati river on the basis of physico-chemical parameters. It was found that surface water quality of the downstream river was different from the water quality of the upstream. The analysis of the water quality parameters of the Ichamati river clearly indicate high pollution load on the river water which can be accounted to agricultural discharge, tidal effect and soil erosion. The results further reveal that with the increase in depth of siltation, water quality degraded.

Roy, P. K.; Pal, S.; Banerjee, G.; Biswas Roy, M.; Ray, D.; Majumder, A.

2014-12-01

142

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

143

Gravity and geoid anomalies of the Philippine Sea: Evidence on the depth of compensation for the negative residual water depth anomaly  

NASA Technical Reports Server (NTRS)

A negative free-air gravity anomaly which occurs in the central part of the Philippine Sea was examined to determine the distribution and nature of possible regional mass excesses or deficiencies. Geoid anomalies from GEOS-3 observation were positive. A negative residual geoid anomaly consistent with the area of negative free-air gravity anomalies were found. Theoretical gravity-topography and geoid-topography admittance functions indicated that high density mantle at about 60 km dept could account for the magnitudes of the gravity and residual geoid anomaly and the 1 km residual water depth anomaly in the Philippine Sea. The negative residual depth anomaly may be compensated for by excess density in the uppermost mantle, but the residual geoid and regional free-air gravity anomalies and a slow surface wave velocity structure might result from low-density warm upper mantle material lying beneath the zone of high-density uppermost mantle. From a horizontal disk approximation, the depth of the low-density warm mantle was estimated to be on the order of 200 km.

Bowin, C.

1982-01-01

144

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

145

Quantitative relationship between water-depth and sub-fossil ostracod assemblages in Lake Donggi Cona, Qinghai Province, China  

Microsoft Academic Search

A calibration data set of 51 surface sediment samples from Lake Donggi Cona on the northeastern Tibetan Plateau was investigated\\u000a to study the relationship between sub-fossil ostracod assemblages and water depth. Samples were collected over a depth range\\u000a from 0.6 to 80 m. A total of 16 ostracod species was identified from the lake with about half of the species restricted

Steffen Mischke; Ulrich Bößneck; Bernhard Diekmann; Ulrike Herzschuh; Huijun Jin; Annette Kramer; Bernd Wünnemann; Chengjun Zhang

2010-01-01

146

Scattering of surface water waves involving semi-infinite floating elastic plates on water of finite depth  

NASA Astrophysics Data System (ADS)

Two problems of scattering of surface water waves involving a semi-infinite elastic plate and a pair of semi-infinite elastic plates, separated by a gap of finite width, floating horizontally on water of finite depth, are investigated in the present work for a two-dimensional time-harmonic case. Within the frame of linear water wave theory, the solutions of the two boundary value problems under consideration have been represented in the forms of eigenfunction expansions. Approximate values of the reflection and transmission coefficients are obtained by solving an over-determined system of linear algebraic equations in each problem. In both the problems, the method of least squares as well as the singular value decomposition have been employed and tables of numerical values of the reflection and transmission coefficients are presented for specific choices of the parameters for modelling the elastic plates. Our main aim is to check the energy balance relation in each problem which plays a very important role in the present approach of solutions of mixed boundary value problems involving Laplace equations. The main advantage of the present approach of solutions is that the results for the values of reflection and transmission coefficients obtained by using both the methods are found to satisfy the energy-balance relations associated with the respective scattering problems under consideration. The absolute values of the reflection and transmission coefficients are presented graphically against different values of the wave numbers.

Chakrabarti, Aloknath; Mohapatra, Smrutiranjan

2013-09-01

147

Understanding patterns in global water table depth: the enormous data challenges (Invited)  

NASA Astrophysics Data System (ADS)

The depth to groundwater can tell us much about where societies and land ecosystems can potentially depend on this water resource, but to have a coherent picture of this variable in space and time requires real data support. Here we outline the key roles that groundwater plays in land surface processes, and present some rudimentary effort in compiling observations and building simple models, the latter as a case study to expose the vast deficiency in data and the need for community-level, and international coordination. Key challenges include the establishment of a global network of groundwater time series for syntheses and analyses of patterns and trends (e.g., the Pan-Africa effort led by Richard Taylor), and a global database of upper crustal porosity and permeability for supporting model simulations (e.g., MacroStrat led by Shanan Peters and the new Digital Crust initiative at NSF-USGS Powell Synthesis Center). Real steps must be taken to build these community data infrastructure if we are to understand the functions of groundwater in shaping terrestrial water fluxes.

Fan, Y.; Li, H.; Pokhrel, Y. N.; Miguez-Macho, G.

2013-12-01

148

Modelling Contrasting Responses of Wetland Productivity to Changes in Water Table Depth  

NASA Astrophysics Data System (ADS)

Responses of wetland productivity to changes in water table depth (WTD) are controlled by complex interactions among several soil and plant processes, and hence are site-specific rather than general in nature. Hydrological controls on wetland productivity were studied by representing these interactions in connected hummock and hollow sites in the ecosystem model ecosys, and by testing CO2 and energy fluxes from the model with those measured by eddy covariance (EC) during years with contrasting WTD in a shrub fen at Lost Creek, WI. Modelled interactions among coupled processes for O2 transfer, O2 uptake, C oxidation, N mineralization, N uptake and C fixation by diverse microbial, root and mycorrhizal populations enabled the model to simulate complex responses of CO2 exchange to changes in WTD that depended on the WTD at which change was occurring. At the site scale, greater WTD caused the model to simulate greater CO2 influxes and effluxes over hummocks vs. hollows, as has been found at field sites. At the landscape scale, greater WTD caused the model to simulate greater diurnal CO2 influxes and effluxes under cooler weather when water tables were shallow, but also smaller diurnal CO2 influxes and effluxes under warmer weather when water tables were deeper, as was also apparent in the EC flux measurements. At an annual time scale, these diurnal responses to WTD in the model caused lower net primary productivity (NPP) and heterotrophic respiration (Rh), but higher net ecosystem productivity (NEP = NPP - Rh), to be simulated in a cooler year with a shallower water table than in a warmer year with a deeper one. This difference in NEP was consistent with those estimated from gap-filled EC fluxes in years with different water tables at Lost Creek and at similar boreal fens elsewhere. In sensitivity test of the model, annual NEP declined with increasing WTD in a year with a shallow water table, but rose in a year with a deeper one. The model thus provided an integrated set of hypotheses for explaining site-specific and sometimes contrasting responses of wetland productivity to changes in WTD as found in different field experiments.

Grant, R. F.; Desai, A. R.; Sulman, B. N.

2012-12-01

149

Modelling contrasting responses of wetland productivity to changes in water table depth  

NASA Astrophysics Data System (ADS)

Responses of wetland productivity to changes in water table depth (WTD) are controlled by complex interactions among several soil and plant processes, and hence are site-specific rather than general in nature. Hydrological controls on wetland productivity were studied by representing these interactions in connected hummock and hollow sites in the ecosystem model ecosys, and by testing CO2 and energy fluxes from the model with those measured by eddy covariance (EC) during years with contrasting WTD in a shrub fen at Lost Creek, WI. Modelled interactions among coupled processes for O2 transfer, O2 uptake, C oxidation, N mineralization, N uptake and C fixation by diverse microbial, root and mycorrhizal populations enabled the model to simulate complex responses of CO2 exchange to changes in WTD that depended on the WTD at which change was occurring. At the site scale, greater WTD caused the model to simulate greater CO2 influxes and effluxes over hummocks vs. hollows, as has been found at field sites. At the landscape scale, greater WTD caused the model to simulate greater diurnal CO2 influxes and effluxes under cooler weather when water tables were shallow, but also smaller diurnal CO2 influxes and effluxes under warmer weather when water tables were deeper, as was also apparent in the EC flux measurements. At an annual time scale, these diurnal responses to WTD in the model caused lower net primary productivity (NPP) and heterotrophic respiration (Rh), but higher net ecosystem productivity (NEP = NPP - Rh), to be simulated in a cooler year with a shallower water table than in a warmer year with a deeper one. This difference in NEP was consistent with those estimated from gap-filled EC fluxes in years with different water tables at Lost Creek and at similar boreal fens elsewhere. In sensitivity tests of the model, annual NEP declined with increasing WTD in a year with a shallow water table, but rose in a year with a deeper one. The model thus provided an integrated set of hypotheses for explaining site-specific and sometimes contrasting responses of wetland productivity to changes in WTD as found in different field experiments.

Grant, R. F.; Desai, A. R.; Sulman, B. N.

2012-11-01

150

Modelling contrasting responses of wetland productivity to changes in water table depth  

NASA Astrophysics Data System (ADS)

Responses of wetland productivity to changes in water table depth (WTD) are controlled by complex interactions among several soil and plant processes, and hence are site-specific rather than general in nature. Hydrological controls on wetland productivity were studied by representing these interactions in connected hummock and hollow sites in the ecosystem model ecosys, and by testing CO2 and energy fluxes from the model with those measured by eddy covariance (EC) during years with contrasting WTD in a shrub fen at Lost Creek, WI. Modelled interactions among coupled processes for O2 transfer, O2 uptake, C oxidation, N mineralization, N uptake and C fixation by diverse microbial, root, mycorrhizal and shoot populations enabled the model to simulate complex responses of CO2 exchange to changes in WTD that depended on the WTD at which change was occurring. At the site scale, greater WTD caused the model to simulate greater CO2 influxes and effluxes over hummocks vs. hollows, as has been found at field sites. At the landscape scale, greater WTD caused the model to simulate greater diurnal CO2 influxes and effluxes under cooler weather when water tables were shallow, but also smaller diurnal CO2 influxes and effluxes under warmer weather when water tables were deeper, as was also apparent in the EC flux measurements. At an annual time scale, these diurnal responses to WTD in the model caused lower net primary productivity (NPP) and heterotrophic respiration (Rh), but higher net ecosystem productivity (NEP = NPP - Rh), to be simulated in a cooler year with a shallower water table than in a warmer year with a deeper one. This difference in NEP was consistent with those estimated from gap-filled EC fluxes in years with different water tables at Lost Creek and at similar boreal fens elsewhere. In sensitivity test of the model, annual NEP declined with increasing WTD in a year with a shallow water table, but rose in a year with a deeper one. The model thus provided an integrated set of hypotheses for explaining site-specific and sometimes contrasting responses of wetland productivity to changes in WTD as found in different field experiments.

Grant, R. F.; Desai, A. R.; Sulman, B. N.

2012-05-01

151

Sponge distribution across Davies Reef, Great Barrier Reef, relative to location, depth, and water movement  

Microsoft Academic Search

Sponge populations were surveyed at different depths in three zones of Davies Reef, a large platform reef of the central Great Barrier Reef. Depth is the major discriminatory factor as few sponges are found within the first 10 m depth and maximal populations occur between 15 m and 30 m on fore-reef, lagoon and back-reef slopes. Reef location is another

Clive R. Wilkinson; Elizabeth Evans

1989-01-01

152

Airborne Sunphotometry of Aerosol Optical Depth and Columnar Water Vapor During ACE-Asia  

NASA Technical Reports Server (NTRS)

During the Intensive Field Campaign (IFC) of the Aerosol Characterization Experiment - Asia (ACE-Asia), March-May 2001, the 6-channel NASA Ames Airborne Tracking Sunphotometer (AATS-6) operated during 15 of the 19 research flights aboard the NCAR C- 130, while its 14-channel counterpart (AATS- 14) was flown successfully on all 18 research flights of a Twin Otter aircraft operated by the Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS), Monterey, CA. ACE-Asia was the fourth in a series of aerosol characterization experiments and focused on aerosol outflow from the Asian continent to the Pacific basin. Each ACE was designed to integrate suborbital and satellite measurements and models so as to reduce the uncertainty in calculations of the climate forcing due to aerosols. The Ames Airborne Tracking Sunphotometers measured solar beam transmission at 6 (380-1021 nm, AATS-6) and 14 wavelengths (353-1558 nm, AATS-14) respectively, yielding aerosol optical depth (AOD) spectra and column water vapor (CWV). Vertical differentiation in profiles yielded aerosol extinction and water vapor concentration. The wavelength dependence of AOD and extinction indicates that supermicron dust was often a major component of the aerosol. Frequently this dust-containing aerosol extended to high altitudes. For example, in data flights analyzed to date 34 +/- 13% of full-column AOD(525 nm) was above 3 km. In contrast, only 10 +/- 4% of CWV was above 3 km. In this paper, we will show first sunphotometer-derived results regarding the spatial variation of AOD and CWV, as well as the vertical distribution of aerosol extinction and water vapor concentration. Preliminary comparison studies between our AOD/aerosol extinction data and results from: (1) extinction products derived using in situ measurements and (2) AOD retrievals using the Multi-angle Imaging Spectro-Radiometer (MISR) aboard the TERRA satellite will also be presented.

Redemann, Jens; Schmid, B.; Russell, P. B.; Livingston, J. M.; Eilers, J. A.; Ramirez, S. A.; Kahn, R.; Hipskind, R. Stephen (Technical Monitor)

2001-01-01

153

Hand powered portable ultraviolet sterilizing water bottle with active UV dose sensing  

E-print Network

A portable hand powered water sterilization device was created to address a portion of the growing epidemic of global water contamination. As being more supply chain independent and having an active dose sensing component ...

Das, Chandan (Chandan K.)

2007-01-01

154

Evaluation of multi-resolution satellite sensors for assessing water quality and bottom depth of Lake Garda.  

PubMed

In this study we evaluate the capabilities of three satellite sensors for assessing water composition and bottom depth in Lake Garda, Italy. A consistent physics-based processing chain was applied to Moderate Resolution Imaging Spectroradiometer (MODIS), Landsat-8 Operational Land Imager (OLI) and RapidEye. Images gathered on 10 June 2014 were corrected for the atmospheric effects with the 6SV code. The computed remote sensing reflectance (Rrs) from MODIS and OLI were converted into water quality parameters by adopting a spectral inversion procedure based on a bio-optical model calibrated with optical properties of the lake. The same spectral inversion procedure was applied to RapidEye and to OLI data to map bottom depth. In situ measurements of Rrs and of concentrations of water quality parameters collected in five locations were used to evaluate the models. The bottom depth maps from OLI and RapidEye showed similar gradients up to 7 m (r = 0.72). The results indicate that: (1) the spatial and radiometric resolutions of OLI enabled mapping water constituents and bottom properties; (2) MODIS was appropriate for assessing water quality in the pelagic areas at a coarser spatial resolution; and (3) RapidEye had the capability to retrieve bottom depth at high spatial resolution. Future work should evaluate the performance of the three sensors in different bio-optical conditions. PMID:25517691

Giardino, Claudia; Bresciani, Mariano; Cazzaniga, Ilaria; Schenk, Karin; Rieger, Patrizia; Braga, Federica; Matta, Erica; Brando, Vittorio E

2014-01-01

155

Evaluation of Multi-Resolution Satellite Sensors for Assessing Water Quality and Bottom Depth of Lake Garda  

PubMed Central

In this study we evaluate the capabilities of three satellite sensors for assessing water composition and bottom depth in Lake Garda, Italy. A consistent physics-based processing chain was applied to Moderate Resolution Imaging Spectroradiometer (MODIS), Landsat-8 Operational Land Imager (OLI) and RapidEye. Images gathered on 10 June 2014 were corrected for the atmospheric effects with the 6SV code. The computed remote sensing reflectance (Rrs) from MODIS and OLI were converted into water quality parameters by adopting a spectral inversion procedure based on a bio-optical model calibrated with optical properties of the lake. The same spectral inversion procedure was applied to RapidEye and to OLI data to map bottom depth. In situ measurements of Rrs and of concentrations of water quality parameters collected in five locations were used to evaluate the models. The bottom depth maps from OLI and RapidEye showed similar gradients up to 7 m (r = 0.72). The results indicate that: (1) the spatial and radiometric resolutions of OLI enabled mapping water constituents and bottom properties; (2) MODIS was appropriate for assessing water quality in the pelagic areas at a coarser spatial resolution; and (3) RapidEye had the capability to retrieve bottom depth at high spatial resolution. Future work should evaluate the performance of the three sensors in different bio-optical conditions. PMID:25517691

Giardino, Claudia; Bresciani, Mariano; Cazzaniga, Ilaria; Schenk, Karin; Rieger, Patrizia; Braga, Federica; Matta, Erica; Brando, Vittorio E.

2014-01-01

156

Impact of interspecific interactions on the soil water uptake depth in a young temperate mixed species plantation  

NASA Astrophysics Data System (ADS)

Interactions between tree species in forests can be beneficial to ecosystem functions and services related to the carbon and water cycles by improving for example transpiration and productivity. However, little is known on below- and above-ground processes leading to these positive effects. We tested whether stratification in soil water uptake depth occurred between four tree species in a 10-year-old temperate mixed species plantation during a dry summer. We selected dominant and co-dominant trees of European beech, Sessile oak, Douglas fir and Norway spruce in areas with varying species diversity, competition intensity, and where different plant functional types (broadleaf vs. conifer) were present. We applied a deuterium labelling approach that consisted of spraying labelled water to the soil surface to create a strong vertical gradient of the deuterium isotope composition in the soil water. The deuterium isotope composition of both the xylem sap and the soil water was measured before labelling, and then again three days after labelling, to estimate the soil water uptake depth using a simple modelling approach. We also sampled leaves and needles from selected trees to measure their carbon isotope composition (a proxy for water use efficiency) and total nitrogen content. At the end of the summer, we found differences in the soil water uptake depth between plant functional types but not within types: on average, coniferous species extracted water from deeper layers than did broadleaved species. Neither species diversity nor competition intensity had a detectable influence on soil water uptake depth, foliar water use efficiency or foliar nitrogen concentration in the species studied. However, when coexisting with an increasing proportion of conifers, beech extracted water from progressively deeper soil layers. We conclude that complementarity for water uptake could occur in this 10-year-old plantation because of inherent differences among functional groups (conifers and broadleaves). Furthermore, water uptake depth of beech was already influenced at this young development stage by interspecific interactions whereas no clear niche differentiation occurred for the other species. This finding does not preclude that plasticity-mediated responses to species interactions could increase as the plantation ages, leading to the coexistence of these species in adult forest stands.

Grossiord, Charlotte; Gessler, Arthur; Granier, André; Berger, Sigrid; Bréchet, Claude; Hentschel, Rainer; Hommel, Robert; Scherer-Lorenzen, Michael; Bonal, Damien

2014-11-01

157

Depth of the biomass maximum affects the rules of resource competition in a water column.  

PubMed

The theory of resource competition in spatially extended systems with resources and biomass fluxes is far from trivial. Here, we analyze the competition between two phytoplankton species for light and a nutrient in a weakly mixed water column. We develop a general framework for such an analysis and show that the competition outcome can be largely understood from a single parameter, the slope of the invasion threshold in the plane of resources. Using this approach, we show that the competition outcome crucially depends on the depth of the biomass maximum. Under eutrophic conditions, when the phytoplankton production peaks on the surface, species composition depends on the ratio of resource supplies, and the competition outcome follows the “classic” rule: coexistence is possible if each competitor has the greatest effect on its most limiting resource. By contrast, in oligotrophic systems, characterized by deep biomass maxima, the absolute level of resource supplies drives species composition, and coexistence becomes more feasible if each competitor mostly consumes its least limiting resource. Finally, when the production peaks in the subsurface, good nutrient competitors are favored. Our findings are supported by empirical data. PMID:25508783

Ryabov, Alexei B; Blasius, Bernd

2014-11-01

158

Depth of the biomass maximum affects the rules of resource competition in a water column.  

PubMed

The theory of resource competition in spatially extended systems with resources and biomass fluxes is far from trivial. Here, we analyze the competition between two phytoplankton species for light and a nutrient in a weakly mixed water column. We develop a general framework for such an analysis and show that the competition outcome can be largely understood from a single parameter, the slope of the invasion threshold in the plane of resources. Using this approach, we show that the competition outcome crucially depends on the depth of the biomass maximum. Under eutrophic conditions, when the phytoplankton production peaks on the surface, species composition depends on the ratio of resource supplies, and the competition outcome follows the “classic” rule: coexistence is possible if each competitor has the greatest effect on its most limiting resource. By contrast, in oligotrophic systems, characterized by deep biomass maxima, the absolute level of resource supplies drives species composition, and coexistence becomes more feasible if each competitor mostly consumes its least limiting resource. Finally, when the production peaks in the subsurface, good nutrient competitors are favored. Our findings are supported by empirical data. PMID:25481931

Ryabov, Alexei B; Blasius, Bernd

2014-11-01

159

What depth should deep-sea water be pumped up from in the South China Sea for medicinal research?  

NASA Astrophysics Data System (ADS)

In this study, seawater was pumped up from 150, 200, 300, 500 and 1000 m in the South China Sea and analyzed to make certain what depth should deep-sea water (DSW) be pumped up for medicinal usage. The pumping depth of DSW was determined on the basis of chemical ingredients. The analyses of inorganic elements and dissolved organic matter (DOM) were performed by inductively coupled plasma mass spectrometry (ICP-MS) and ultra performance liquid chromatography-mass spectrometry (UPLC-MS) respectively. The raw data were used for hierarchical cluster analysis (HCA) and principal component analysis (PCA). The results showed that seawater pumped up from 500 m and 1000 m was similar in their chemical ingredients, and was different from the seawater pumped up from other depths. These results indicated that seawater from more than 500 m depth had relatively stable chemical ingredients and could be used as DSW in the South China Sea.

He, Shan; Liu, Hongbing; Yang, Xue; Li, Chunxia; Guan, Huashi

2013-03-01

160

Some relationships between Secchi depth and inherent optical properties of natural waters  

NASA Technical Reports Server (NTRS)

Relationships between the inherent and optical properties of the ocean (Gorden et al., 1975 and Preisendorfer, 1961) are combined with the Duntley-Preisendorfer equation to show the dependence of these properties on the depth at which a Secchi disk disappears from view. An expression relating the Secchi depth to the limiting contrast of the disk is derived in terms of the average beam attenuation coefficient, the average diffuse attenuation coefficient for downwelling irradiance, the albedo of the disk, and the reflectance functions at the Secchi depth and just below the surface. It is shown that combining Secchi depth observations with other optical properties yields significant information about the constituents of the medium.

Gordon, H. R.; Wouters, A. W.

1978-01-01

161

Water-table depth and oxygen content of deep peat in relation to root growth of Pinus contorta  

Microsoft Academic Search

Summary Oxygen concentrations were measured at monthly intervals in deep peat in plots in which the water-tables are maintained artificially at levels ranging in depth from 11 cm to 33 cm below the surface. Good correlation was observed between weight of roots of 11 year oldPinus contorta in these plots and oxygen concentrations in different horizons at all times of

Robert Boggie

1977-01-01

162

Seasonal and depth-related dynamics of prokaryotes and viruses in surface and deep waters of the northwestern Mediterranean Sea  

E-print Network

Seasonal and depth-related dynamics of prokaryotes and viruses in surface and deep waters Keywords: Bacteriophage Virus Prokaryote Marine Deep sea Flow cytometry a b s t r a c t The study site of prokaryotes and viruses was determined by flow cytometry (FCM). Prokaryotic abundance in the epi-, meso

Winter, Christian

163

Variation of Pressure with Depth of Water: Working with High-Tech and Low-Cost Materials  

ERIC Educational Resources Information Center

When you dive underwater, you feel the pressure on your ears and, as you dive deeper, more pressure is felt. This article presents an activity that teachers might find useful for demonstrating the relationship between water depth and pressure. (Contains 5 figures and 1 table.)

Ornek, Funda; Zziwa, Byansi Jude; Taganahan, Teresita D.

2013-01-01

164

Statistical testing of a new testate amoeba-based transfer function for water-table depth reconstruction  

E-print Network

Statistical testing of a new testate amoeba-based transfer function for water-table depth. A new testate amoeba-based transfer function is presented that fully incorporates the new recommended America; peat; testate amoebae; transfer function. Introduction Testate amoebae are a group of Protozoa

165

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

166

Depth dose distributions measured with thermoluminescence detectors inside the anthropomorphic torso of the MATROSHKA experiment inside and outside the ISS  

Microsoft Academic Search

The ESA MATROSHKA (MTR) facility was realized through the German Aerospace Center, DLR, Cologne, as main contractor, aiming for the determination of skin and organ doses within a simulated human upper torso. MTR simulates, by applying an anthropomorphic upper torso, as exact as possible an astronaut performing either an extravehicular activity (EVA) (MTR Phase 1) or an astronaut working inside

Thomas Berger; Guenther Reitz; Michael Hajek; Robert Bergmann; Pawel Bilski; Msc. Monika Puchalska

2008-01-01

167

Use of ground penetrating radar for determination of water table depth and subsurface soil characteristics at Kennedy Space Center  

NASA Astrophysics Data System (ADS)

Sustainable use and management of natural resources require strategic responses using non-destructive tools to provide spatial and temporal data for decision making. Experiments conducted at John F. Kennedy Space Center (KSC) demonstrate ground penetrating radar (GPR) can provide high-resolution images showing depth to water tables. GPR data at KSC were acquired using a MALĹ Rough Terrain 100 MHz Antenna. Data indicate strong correlation (R2=0.80) between measured water table depth (shallow monitoring wells and soil auger) and GPR estimated depth. The study demonstrated the use of GPR to detect Holocene and Pleistocene depositional environments such as Anastasia Formation that consists of admixtures of sand, shell and coquinoid limestone at a depth of 20-25 ft. This corresponds well with the relatively strong reflections from 7.5 to 13 m (125-215 ns) in GPR images. Interpretations derived from radar data coupled with other non-GPR data (wells data and soil auger data) will aid in the understanding of climate change impacts due to sea level rise on the scrub vegetation composition at KSC. Climate change is believed to have a potentially significant impact potential on near coastal ground water levels and associated water table depth. Understanding the impacts of ground water levels changes will, in turn, lead to improved conceptual conservation efforts and identifications of climate change adaptation concepts related to the recovery of the Florida scrub jay (Aphelocoma coerulescens) and other endangered or threatened species which are directly dependent on a healthy near coastal scrub habitat. Transfer of this inexpensive and non-destructive technology to other areas at KSC, Florida, and to other countries, may prove useful in the development of future conservation programs.

Hengari, Gideon M.; Hall, Carlton R.; Kozusko, Tim J.; Bostater, Charles R.

2013-10-01

168

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. PMID:24065874

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

2013-01-01

169

Airborne detection of oceanic turbidity cell structure using depth-resolved laser-induced water Raman backscatter  

NASA Technical Reports Server (NTRS)

Airborne laser-induced, depth-resolved water Raman backscatter is useful in the detection and mapping of water optical transmission variations. This test, together with other field experiments, has identified the need for additional field experiments to resolve the degree of the contribution to the depth-resolved, Raman-backscattered signal waveform that is due to (1) sea surface height or elevation probability density; (2) off-nadir laser beam angle relative to the mean sea surface; and (3) the Gelbstoff fluorescence background, and the analytical techniques required to remove it. When converted to along-track profiles, the waveforms obtained reveal cells of a decreased Raman backscatter superimposed on an overall trend of monotonically decreasing water column optical transmission.

Hoge, F. E.; Swift, R. N.

1983-01-01

170

Influence of variable water depth and turbidity on microalgae production in a shallow estuarine lake system - A modelling study  

NASA Astrophysics Data System (ADS)

Strongly varying water levels and turbidities are typical characteristics of the large shallow estuarine lake system of St. Lucia, one of the largest on the African continent. This theoretical study investigated the combined effects of variable water depth and turbidity on seasonal pelagic and benthic microalgae production using a mathematical model, in order to ascertain productivity levels during variable and extreme conditions. Simulated pelagic and benthic net production varied between 0.3 and 180 g C m-2 year-1 and 0 and 220 g C m-2 year-1, respectively, dependent on depth, turbidity, and variability in turbidity. Although not surprising production and biomass decreased with increasing turbidity and depth. A high variability in turbidity, i.e. an alteration of calm and windy days, could reduce or enhance the seasonal pelagic and benthic production by more than 30% compared to a low variability. The day-to-day variability in wind-induced turbidity therefore influences production in the long term. On the other hand, varying water depth within a year did not significantly influence the seasonal production for turbidities representative of Lake St. Lucia. Reduced lake area and volume as observed during dry periods in Lake St. Lucia did not reduce primary production of the entire system since desiccation resulted in lower water depth and thus increased light availability. This agrees with field observations suggesting little light limitation and high areal microalgal biomass during a period with below average rainfall (2005-2011). Thus, microalgae potentially fulfil their function in the lake food-web even under extreme drought conditions. We believe that these results are of general interest to shallow aquatic ecosystems that are sensitive to drought periods due to either human or natural causes.

Tirok, Katrin; Scharler, Ursula M.

2014-06-01

171

Instrumentation for investigation of the depth-dose distribution by the Liulin-5 instrument of a human phantom on the Russian segment of ISS for estimation of the radiation risk during long term space flights  

Microsoft Academic Search

Described is the Liulin-5 experiment and instrumentation, developed for investigation of the space radiation doses depth distribution in a human phantom on the Russian Segment of the International Space Station (ISS). Liulin-5 experiment is a part of the international project MATROSHKA-R on ISS. The experiment MATROSHKA-R is aimed to study the depth dose distribution at the sites of critical organs

J. Semkova; R. Koleva; G. Todorova; N. Kanchev; V. Petrov; V. Shurshakov; I. Tchhernykh; S. Kireeva

2004-01-01

172

Development of a chronic noncancer oral reference dose and drinking water screening level for sulfolane using benchmark dose modeling.  

PubMed

Sulfolane is a widely used industrial solvent that is often used for gas treatment (sour gas sweetening; hydrogen sulfide removal from shale and coal processes, etc.), and in the manufacture of polymers and electronics, and may be found in pharmaceuticals as a residual solvent used in the manufacturing processes. Sulfolane is considered a high production volume chemical with worldwide production around 18 000-36 000 tons per year. Given that sulfolane has been detected as a contaminant in groundwater, an important potential route of exposure is tap water ingestion. Because there are currently no federal drinking water standards for sulfolane in the USA, we developed a noncancer oral reference dose (RfD) based on benchmark dose modeling, as well as a tap water screening value that is protective of ingestion. Review of the available literature suggests that sulfolane is not likely to be mutagenic, clastogenic or carcinogenic, or pose reproductive or developmental health risks except perhaps at very high exposure concentrations. RfD values derived using benchmark dose modeling were 0.01-0.04?mg?kg(-1) per day, although modeling of developmental endpoints resulted in higher values, approximately 0.4?mg?kg(-1) per day. The lowest, most conservative, RfD of 0.01?mg?kg(-1) per day was based on reduced white blood cell counts in female rats. This RfD was used to develop a tap water screening level that is protective of ingestion, viz. 365 µg l(-1). It is anticipated that these values, along with the hazard identification and dose-response modeling described herein, should be informative for risk assessors and regulators interested in setting health-protective drinking water guideline values for sulfolane. PMID:22936336

Thompson, Chad M; Gaylor, David W; Tachovsky, J Andrew; Perry, Camarie; Carakostas, Michael C; Haws, Laurie C

2013-12-01

173

Arsenic in Drinking Water and Skin Lesions: Dose-Response Data from West Bengal, India  

E-print Network

. (EPIDEMIOLOGY 2003;14:174­182) Key words: arsenic, keratoses, hyperpigmentation, drinking water, case in West Bengal.8 Clear exposure-response relations were found for water-arsenic levels and the prevalenceArsenic in Drinking Water and Skin Lesions: Dose-Response Data from West Bengal, India Reina Haque

California at Berkeley, University of

174

The climate influence on the mid-depth Northeast Atlantic gyres viewed by cold-water corals  

NASA Astrophysics Data System (ADS)

The neodymium (Nd) isotopic composition (expressed in epsilon units, $\\varepsilon$Nd) of reef framework-forming cold-water corals provides unique measures of water mass provenance and mixing within the Northeast Atlantic today and in the past. A reconstruction of near thermocline water $\\varepsilon$Nd from cold-water corals of the Gulf of Cádiz and Porcupine Seabight spanning over the past 300,000 years, now revealed that climate cooling during Marine Isotope Stages (MIS) 7.2 and MIS 8/9 led to a retraction of the mid-depth Subpolar Gyre (mSPG) to the west. Conversely, Northern Hemisphere warming and increasing fresh water fluxes to the northwest (Labrador Sea) favor a stronger eastward extension of the mSPG blocking the northward flow of temperate Atlantic water as observed during the early MIS 1 and the early stage MIS 5.5. These changes are likely the result of large-scale south-north displacement of the westerlies similar to present-day observations that the North Atlantic Oscillation (NAO) is linked with mid-depth ocean circulation. Based on these observations, we hypothesize that further climate warming will also strengthen the mSPG leading to a salt and temperature decrease in the Northeast Atlantic whereas salinity and temperature will increase in the temperate Atlantic. However, the amplitude of such changes on North Atlantic overturning remains to be tested.

Montero-Serrano, Jean-Carlos; Frank, Norbert; Colin, Christophe; Wienberg, Claudia; Eisele, Markus

2011-10-01

175

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

176

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

2010-01-21

177

Absorbed dose to water determination with ionization chamber dosimetry and calorimetry in restricted neutron, photon, proton and heavy-ion radiation fields  

NASA Astrophysics Data System (ADS)

Absolute dose measurements with a transportable water calorimeter and ionization chambers were performed at a water depth of 20 mm in four different types of radiation fields, for a collimated 60Co photon beam, for a collimated neutron beam with a fluence-averaged mean energy of 5.25 MeV, for collimated proton beams with mean energies of 36 MeV and 182 MeV at the measuring position, and for a 12C ion beam in a scanned mode with an energy per atomic mass of 430 MeV u-1. The ionization chambers actually used were calibrated in units of air kerma in the photon reference field of the PTB and in units of absorbed dose to water for a Farmer-type chamber at GSI. The absorbed dose to water inferred from calorimetry was compared with the dose derived from ionometry by applying the radiation-field-dependent parameters. For neutrons, the quantities of the ICRU Report 45, for protons the quantities of the ICRU Report 59 and for the 12C ion beam, the recommended values of the International Atomic Energy Agency (IAEA) protocol (TRS 398) were applied. The mean values of the absolute absorbed dose to water obtained with these two independent methods agreed within the standard uncertainty (k = 1) of 1.8% for calorimetry and of 3.0% for ionometry for all types and energies of the radiation beams used in this comparison.

Brede, H. J.; Greif, K.-D.; Hecker, O.; Heeg, P.; Heese, J.; Jones, D. T. L.; Kluge, H.; Schardt, D.

2006-08-01

178

Modeling scale-dependent runoff generation in a small semi-arid watershed accounting for rainfall intensity and water depth  

NASA Astrophysics Data System (ADS)

Observed scale effects of runoff on hillslopes and small watersheds derive from complex interactions of time-varying rainfall rates with runoff, infiltration and macro- and microtopographic structures. A little studied aspect of scale effects is the concept of water depth-dependent infiltration. For semi-arid rangeland it has been demonstrated that mounds underneath shrubs have a high infiltrability and lower lying compacted or stony inter-shrub areas have a lower infiltrability. It is hypothesized that runoff accumulation further downslope leads to increased water depth, inundating high infiltrability areas, which increases the area-averaged infiltration rate. A model was developed that combines the concepts of water depth-dependent infiltration, partial contributing area under variable rainfall intensity, and the Green-Ampt theory for point-scale infiltration. The model was applied to rainfall simulation data and natural rainfall-runoff data from a small sub-watershed (0.4 ha) of the Walnut Gulch Experimental Watershed in the semi-arid US Southwest. Its performance to reproduce observed hydrographs was compared to that of a conventional Green-Ampt model assuming complete inundation sheet flow, with runon infiltration, which is infiltration of runoff onto pervious downstream areas. Parameters were derived from rainfall simulations and from watershed-scale calibration directly from the rainfall-runoff events. The performance of the water depth-dependent model was better than that of the conventional model on the scale of a rainfall simulator plot, but on the scale of a small watershed the performance of both model types was similar. We believe that the proposed model contributes to a less scale-dependent way of modeling runoff and erosion on the hillslope-scale.

Langhans, Christoph; Govers, Gerard; Diels, Jan; Stone, Jeffry J.; Nearing, Mark A.

2014-07-01

179

Analytical modelling of the total depth of cut in the abrasive water jet machining of polycrystalline brittle material  

Microsoft Academic Search

In the present paper, the material removal mechanism in the abrasive water jet machining of polycrystalline ceramics is addressed. The proposed mechanism seems to be micro-cutting and inter-granular fracture at shallow angles of impact. This is followed by plastic deformation and inter-granular fracture at near-orthogonal angles of impact. The analytical model developed to predict the total depth of cut correlates

S. Paul; A. M. Hoogstrate; C. A. van Luttervelt; H. J. J. Kals

1998-01-01

180

Depth to water in the eastern Snake River Plain and surrounding tributary valleys, southwestern Idaho and eastern Oregon, calculated using water levels from 1980 to 1988  

USGS Publications Warehouse

The vulnerability of ground water to contamination in Idaho is being assessed by the IDHW/DEQ (Idaho Department of Health and Welfare, Division of Environmental Quality), using a modified version of the Environmental Orotection Agency DRASTIC methods (Allers and others, 1985). The project was designed as a technique to: (1) Assign priorities for development of ground-water management and monitoring programs; (2) build support for, and public awareness of, vulnerability or ground water to contamination; (3) assist in the development of regulatory programs; and (4) provide access to technical data through the use of a GIS (geographic information system) (C. Grantha,, Idaho Department of Health and Welfare, written commun., 1989). A digital representation of first-encountered water below land surface is an important element in evaluating vulnerability of ground water to contamination. Depth-to-water values were developed using existing data and computer software to construct a GIS data set to be combined with a sols data set developed by the SCS (Soil Conservation Service) and IDHW/WQB (Idaho Department of Health and Welfare/Water Quality Bureau), and a recharge data set developed by the IDWR/RSF (Idaho Department of Water Resources/Remote Sensing Facility). The USGS (U.S. Geological Survey) developed digital depth-to-water values for eleven 1:100,000-scale quadrangles on the eastern Snake River Plain and surrounding tributary valleys.

Maupin, Molly A.

1992-01-01

181

Depth to water in the western Snake River Plain and surrounding tributary valleys, southwestern Idaho and eastern Oregon, calculated using water levels from 1980 to 1988  

USGS Publications Warehouse

The vulnerability of ground water to contamination in Idaho is being assessed by the ISHW/DEQ (Idaho Department of Health and Welfare, Division of Environmental Quality), using a modified version of the Environmental Protection Agency DRASTIC methods (Allers and others, 1985). The project was designed as a technique to: (1) Assign priorities for development of ground-water management and monitoring programs; (2) build support for, and public awareness of, vulnerability of ground water to contamination; (3) assist in the development of regulatory programs; and (4) provide access to technical data through the use of a GIS (geographic information system) (C. Grantham, Idaho Department of Health and Welfare, written commun., 1989). Digital representation of first-encountered water below land surface is an important element in evaluating vulnerability of ground water to contamination. Depth-to-water values were developed using existing data and computer software to construct a GIS data set to be combined with a soils data set developed by the SCS (Soul Conservation Service) and the IDHW/WQB (Idaho Department of Health and Welfare/Water Quality Bureau), and a recharge data set developed by the IDWR/RSF (idaho Department of Water Resources/Remote Sensing Facility). The USGS (U.S. Geological Survey) has developed digital depth-to-water values for eleven 1:100,00-scale quadrangles on the eastern Snake River Plain and surrounding tributary valleys.

Maupin, Molly A.

1991-01-01

182

Evolution of deep-water rifted margins: Testing depth-dependent extensional models  

NASA Astrophysics Data System (ADS)

A general understanding of rifted margins, which form by thinning of the continental lithosphere, exists. Nevertheless, the exact form of thinning is unclear. This debate has been stimulated by acquisition of dense seismic wide-angle and deep reflection surveys from Atlantic Ocean margins. A central issue concerns the way in which thinning changes with depth. We have tackled this issue by developing a generalized inverse model. This model attempts to fit subsidence and crustal thinning observations by varying strain rate as a function of time and space. Depth-dependent thinning is permitted but we do not prescribe its existence or form. Here, the algorithm is applied to six margins, including two of the most contentious conjugate margins: Newfoundland-Iberia and Brazil-Angola. Calculated strain rate histories predict thinning estimates which broadly match estimates inferred from normal faulting. The Eastern Indian and Beaufort Sea margins formed by largely uniform lithospheric thinning. In contrast, the Newfoundland-Iberian conjugate margins formed by a pattern of strongly depth-dependent strain rate. To account for the paucity of syn-rift decompression melting of the underlying asthenosphere, the lithospheric mantle close to oceanic-continent transition must thin more slowly than the overlying crust. This form of depth dependency is not common. For example, the Brazil-Angolan conjugate margin could have formed by uniform lithospheric thinning provided thick layers of salt were deposited in a preexisting 400 m deep topographic depression. Depth-dependent thinning is not required to account for rapid subsidence of presalt strata.

Crosby, A. G.; White, N. J.; Edwards, G. R. H.; Thompson, M.; Corfield, R.; Mackay, L.

2011-02-01

183

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

184

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.

185

Tsunami and acoustic-gravity waves in water of constant depth  

SciTech Connect

A study of wave radiation by a rather general bottom displacement, in a compressible ocean of otherwise constant depth, is carried out within the framework of a three-dimensional linear theory. Simple analytic expressions for the flow field, at large distance from the disturbance, are derived. Realistic numerical examples indicate that the Acoustic-Gravity waves, which significantly precede the Tsunami, are expected to leave a measurable signature on bottom-pressure records that should be considered for early detection of Tsunami.

Hendin, Gali; Stiassnie, Michael [Faculty of Civil and Environmental Engineering, Technion – Israel institute of technology, Haifa 32000 (Israel)] [Faculty of Civil and Environmental Engineering, Technion – Israel institute of technology, Haifa 32000 (Israel)

2013-08-15

186

Risk assessment and evaluation of the conductor setting depth in shallow water, Gulf of Mexico  

E-print Network

, they have ignored situations where upward fluid migration can lead to abnormally pressured shallow formations, especially in a developed field. Even in situations where there has not been any artificial charging of shallow formations, selection... on rudimentary engineering and geological theories and to provide a feasible engineering procedure for the conductor setting depth based on direct measurements, such as soil boring. 1.1 Background Abnormally pressured formations can be found around...

Tu, Yong B.

2006-08-16

187

Seasonal variation in light, mixing depth and primary productivity in temperate northern hemisphere waters  

NSDL National Science Digital Library

In this exercise students work with light, temperature, and phytoplankton biomass proxy (chlorophyll a concentration) data to; Become more skilled in reading and interpreting semi log graphs, temperature profiles, and time series plots. Practice unit conversions. Gain an understanding of k, the attenuation coefficient for nondirectional light. See how the depth of the photic zone and the surface mixed layer varies seasonally at temperate latitudes and how this relates to seasonal phytoplankton productivity dynamics.

Lauren Sahl

188

Chemical composition of selected Kansas brines as an aid to interpreting change in water chemistry with depth  

USGS Publications Warehouse

Chemical analyses of approximately 1,881 samples of water from selected Kansas brines define the variations of water chemistry with depth and aquifer age. The most concentrated brines are found in the Permian rocks which occupy the intermediate section of the geologic column of this area. Salinity decreases below the Permian until the Ordovician (Arbuckle) horizon is reached and then increases until the Precambrian basement rocks are reached. Chemically, the petroleum brines studied in this small area fit the generally accepted pattern of an increase in calcium, sodium and chloride content with increasing salinity. They do not fit the often-predicted trend of increases in the calcium to chloride ratio, calcium content and salinity with depth and geologic age. The calcium to chloride ratio tends to be asymptotic to about 0.2 with increasing chloride content. Sulfate tends to decrease with increasing calcium content. Bicarbonate content is relatively constant with depth. If many of the hypotheses concerning the chemistry of petroleum brines are valid, then the brines studied are anomolous. An alternative lies in accepting the thesis that exceptions to these hypotheses are rapidly becoming the rule and that indeed we still do not have a valid and general hypothesis to explain the origin and chemistry of petroleum brines. ?? 1969.

Dingman, R.J.; Angino, E.E.

1969-01-01

189

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

190

Natural radionuclides in bottled drinking waters produced in Croatia and their contribution to radiation dose.  

PubMed

Activity concentrations of (234)U, (238)U, (226)Ra, (228)Ra, (210)Po and (210)Pb in all Croatian bottled drinking natural spring and natural mineral water products, commercially available on the market, were determined. The samples originated from various geological regions of Croatia. Activity concentrations of measured radionuclides are in general decreasing in this order: (234)U>(238)U>(226)Ra>(228)Ra>(210)Pb>(210)Po and (226)Ra>(228)Ra>(234)U>(238)U>(210)Pb>(210)Po for natural spring and mineral waters, respectively. Based on the radionuclide activity concentrations average total annual effective ingestion doses for infants, children and adults, as well as contribution of each particular radionuclide to total dose, were assessed and discussed. The highest doses were calculated for children from 7 to 12 years of age, which makes them the most critical group of population. All values for each type of water, as well as for each population group, were well below the recommended reference dose level (RDL) of 0.1 mSv from one year's consumption of drinking water according to the European Commission recommendations from 1998. Contribution of each particular radionuclide to total doses varied among different water types and within each water type, as well as between different age groups, where the lowest contribution was found for uranium isotopes and the highest for (228)Ra. PMID:22906977

Rožmari?, Martina; Rogi?, Matea; Benedik, Ljudmila; Strok, Marko

2012-10-15

191

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

2001-01-01

192

Interrelationships of petiole air canal architecture, water depth and convective air flow in Nymphaea odorata (Nymphaeaceae)  

Technology Transfer Automated Retrieval System (TEKTRAN)

Premise of the study--Nymphaea odorata grows in water up to 2 m deep, producing fewer, larger leaves in deeper water. This species has a convective flow system that moves gases from younger leaves through submerged parts to older leaves, aerating submerged parts. Petiole air canals are in the conv...

193

CHARACTERISATION OF AGED HDPE PIPES FROM DRINKING WATER DISTRIBUTION: INVESTIGATION OF CRACK DEPTH BY NOL RING  

E-print Network

are used for the transport of drinking water. However, disinfectants in water seem to have a strong impact with disinfectants leading to the formation of a thin oxidised layer coupled to the cracks initiation of cracks, when they are in contact with disinfectants such as chlorine dioxide ClO2 or chlorine Cl2 (in severe

Paris-Sud XI, Université de

194

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

2012-06-01

195

The difference of scoring dose to water or tissues in Monte Carlo dose calculations for low energy brachytherapy photon sources  

SciTech Connect

Purpose: The goal of this work is to compare D{sub m,m} (radiation transported in medium; dose scored in medium) and D{sub w,m} (radiation transported in medium; dose scored in water) obtained from Monte Carlo (MC) simulations for a subset of human tissues of interest in low energy photon brachytherapy. Using low dose rate seeds and an electronic brachytherapy source (EBS), the authors quantify the large cavity theory conversion factors required. The authors also assess whether applying large cavity theory utilizing the sources' initial photon spectra and average photon energy induces errors related to spatial spectral variations. First, ideal spherical geometries were investigated, followed by clinical brachytherapy LDR seed implants for breast and prostate cancer patients. Methods: Two types of dose calculations are performed with the GEANT4 MC code. (1) For several human tissues, dose profiles are obtained in spherical geometries centered on four types of low energy brachytherapy sources: {sup 125}I, {sup 103}Pd, and {sup 131}Cs seeds, as well as an EBS operating at 50 kV. Ratios of D{sub w,m} over D{sub m,m} are evaluated in the 0-6 cm range. In addition to mean tissue composition, compositions corresponding to one standard deviation from the mean are also studied. (2) Four clinical breast (using {sup 103}Pd) and prostate (using {sup 125}I) brachytherapy seed implants are considered. MC dose calculations are performed based on postimplant CT scans using prostate and breast tissue compositions. PTV D{sub 90} values are compared for D{sub w,m} and D{sub m,m}. Results: (1) Differences (D{sub w,m}/D{sub m,m}-1) of -3% to 70% are observed for the investigated tissues. For a given tissue, D{sub w,m}/D{sub m,m} is similar for all sources within 4% and does not vary more than 2% with distance due to very moderate spectral shifts. Variations of tissue composition about the assumed mean composition influence the conversion factors up to 38%. (2) The ratio of D{sub 90(w,m)} over D{sub 90(m,m)} for clinical implants matches D{sub w,m}/D{sub m,m} at 1 cm from the single point sources. Conclusions: Given the small variation with distance, using conversion factors based on the emitted photon spectrum (or its mean energy) of a given source introduces minimal error. The large differences observed between scoring schemes underline the need for guidelines on choice of media for dose reporting. Providing such guidelines is beyond the scope of this work.

Landry, Guillaume; Reniers, Brigitte; Pignol, Jean-Philippe; Beaulieu, Luc; Verhaegen, Frank [Department of Radiation Oncology (MAASTRO), GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht 6201 BN (Netherlands); Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario M4N 3M5 (Canada); Departement de Radio-Oncologie et Centre de Recherche en Cancerologie, Universite Laval, CHUQ Pavillon L'Hotel-Dieu de Quebec, Quebec G1R 2J6 (Canada) and Departement de Physique, de Genie Physique et d'Optique, Universite Laval, Quebec G1K 7P4 (Canada); Department of Radiation Oncology (MAASTRO), GROW School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht 6201 BN (Netherlands) and Department of Oncology, McGill University, Montreal General Hospital, Montreal, Quebec H3G 1A4 (Canada)

2011-03-15

196

A strip theory approximation for wave forces on submerged vehicles in finite depth water  

E-print Network

Autonomous Underwater Vehicles (AUV's) are becoming of increasing use in shallow waters for oceanographic data collection, coastal mapping, and military operations such as mine surveillance along enemy coastlines. Currently ...

Rybka Jan A. (Jan Andrzej)

2005-01-01

197

Oman-India pipeline sets survey challenges. Crossing involves most rugged terrain, water depths four times greater than previous attempts  

SciTech Connect

Decisions concerning the route for the world`s deepest pipeline call for some of the most challenging commercial oceanographic and engineering surveys ever undertaken. Oman Oil Co.`s 1, 170-kilometer pipeline will carry 2 billion cubic feet of gas daily across the Arabian Sea from Oman to the northern coast of India at the Gulf of Kutch. Not only will the project be in water depths four times greater than any previous pipeline, but it will cross some of the world`s most rugged seabed terrain, traversing ridges and plunging into deep canyons. Project costs are likely to approach $5 billion.

Flynn, J. [Wimpey Environmental Ltd., Swindon (United Kingdom)

1995-02-01

198

Dose-dependent inhibition of gastric injury by hydrogen in alkaline electrolyzed drinking water  

PubMed Central

Background Hydrogen has been reported to relieve damage in many disease models, and is a potential additive in drinking water to provide protective effects for patients as several clinical studies revealed. However, the absence of a dose–response relationship in the application of hydrogen is puzzling. We attempted to identify the dose–response relationship of hydrogen in alkaline electrolyzed drinking water through the aspirin induced gastric injury model. Methods In this study, hydrogen-rich alkaline water was obtained by adding H2 to electrolyzed water at one atmosphere pressure. After 2 weeks of drinking, we detected the gastric mucosal damage together with MPO, MDA and 8-OHdG in rat aspirin induced gastric injury model. Results Hydrogen-dose dependent inhibition was observed in stomach mucosal. Under pH 8.5, 0.07, 0.22 and 0.84 ppm hydrogen exhibited a high correlation with inhibitory effects showed by erosion area, MPO activity and MDA content in the stomach. Gastric histology also demonstrated the inhibition of damage by hydrogen-rich alkaline water. However, 8-OHdG level in serum did not have significant hydrogen-dose dependent effect. pH 9.5 showed higher but not significant inhibitory response compared with pH 8.5. Conclusions Hydrogen is effective in relieving the gastric injury induced by aspirin-HCl, and the inhibitory effect is dose-dependent. The reason behind this may be that hydrogen-rich water directly interacted with the target tissue, while the hydrogen concentration in blood was buffered by liver glycogen, evoking a suppressed dose–response effect. Drinking hydrogen-rich water may protect healthy individuals from gastric damage caused by oxidative stress. PMID:24589018

2014-01-01

199

Evaluation of passive microwave snow water equivalent algorithms in the depth hoar-dominated snowpack of the Kuparuk River Watershed, Alaska, USA  

Microsoft Academic Search

This research investigates the utility of passive microwave remote sensing instruments to accurately determine snow water equivalent (SWE) over large spatial extents. Three existing Special Sensor Microwave Imager (SSM\\/I) snow water equivalent algorithms produced by Chang, Tait and Goodison were evaluated for their ability to determine snow water equivalent in a snowpack containing substantial depth hoar, large faceted snow crystals.

Lora S. Koenig; Richard R. Forster

2004-01-01

200

The Testing of AMSR-E Snow Depth and Snow Water Equivalent Estimates in the Northern Hemisphere  

NASA Astrophysics Data System (ADS)

Accurate estimation of snow mass is important for effective characterization of the hydrological cycle at different space and time scales. In the global hydrological cycle, not only does snow constitute a critical seasonal and long-term storage factor but it also affects global climate mass and energy dynamics. Satellite passive microwave observations have been used to estimate global snow depth and snow water equivalent (SWE) since 1979. However, during this time the instruments available have been able to observe snow mass over spatial domains only at regional scales; finer scale observations have not been possible. The Advanced Microwave Scanning Radiometer - EOS launched in 2002 aboard NASA's Aqua platform, has improved spatial resolution capabilities compared with previous passive microwave instruments and, potentially, can be used to estimate snow depth and SWE with increased accuracy at the regional scale. This paper describes refinements to the snow water equivalent products that are being developed for AMSR-E. The baseline retrieval algorithm uses the brightness temperature difference between 18 and 36 GHz channels to estimate snow depth and SWE. Two important refinements under development are described that attempt to better constrain the retrieval algorithm with respect to the effect of grain size and forest cover. Both these factors are known to affect the naturally upwelling microwave radiation from snow. Testing of the refined approach is conducted using daily measurements of snow depth from the World Meteorological Organization (WMO) Global Telecommunications System (GTS) archive. We examine the accuracy of the snow depth estimates at the global scale and also in three regions: Colorado Rocky Mountains, USA, Canadian Prairies and Finland. Each region represents a different "snow regime" and is affected by grain size evolution and forest cover in different ways. Additionally, for each region, WMO/GTS data are augmented by locally collected ground data to produce a more comprehensive ground test data set. The paper demonstrates the accuracy of the refined AMSR-E product and how important the need is to account for grain size and forest cover effects.

Chang, A. T.; Kelly, R. E.; Foster, J. L.; Hall, D. K.

2003-12-01

201

Radium and (40)K in Algerian bottled mineral waters and consequent doses.  

PubMed

Concentrations of (226)Ra, (228)Ra and (40)K in the five most popular Algerian bottled mineral waters have been found to be 13.9 to 148.9 mBq l(-1), 7.2 to 52.9 mBq l(-1) and <0.07 to 2.19 Bq l(-1), respectively. Ratios of (226)Ra to (228)Ra activities ranged from 1.0 to 13.66 with a mean of 5.62. The annual effective doses due to ingestion of these waters have been estimated for three age categories (infants, children and adults) using the measured activities of these radionuclides and assuming the World Health Organisation's default water intake rate. Annual doses for children and adults have been found to be well below the 0.1 mSv y(-1) reference dose level, whereas for the most vulnerable group the annual effective dose from all the waters exceeds the reference value and contributes 12% to the mean annual dose from natural exposure. PMID:19223293

Seghour, A; Seghour, F Z

2009-01-01

202

Depth to and concentrations of water in large bodies of silicic magma. Progress report, July 1, 1982-June 30, 1983  

SciTech Connect

Large bodies of silicic magma are potential sources of geothermal energy and ore. They also pose threats of catastrophic eruptions. The depths of such bodies are related to their economic potential and probably to their eruption mechanisms. The concentrations of water in the magmas are important for their eruptive and dynamical behavior and for the development of ores. Estimates of viscosity and density of melt require knowledge of concentration of water. The concentration of water in melt before ascent and eruption can be measured in inclusions of glass which became trapped in crystals before extrusion. The depth of a magma body can be estimated or delimited if we can find out the concentrations of both carbon dioxide and water in the inclusions of glass. Initial results on the Bishop Tuff of Long Valley Caldera, California yield 4.9 +- 0.5 percent H/sub 2/O for glass included in quartz from the Plinian air fall pumice. This result is comparable to the estimates of Hildreth (1977) of about 3.5 to 4.9 percent H/sub 2/O in the lowermost part of the Bishop ash flow. From January 1982 through December 1982, analyses of inclusions of glass in two additional quartz phenocrysts from the Plinian air fall unit of the Bishop Tuff revealed variable H/sub 2/O and CO/sub 2/. The corresponding partial pressures range between about 2000 and 5000 atmospheres, assuming gas saturation. The variation may be natural or caused by an analytical artifact. A computerized data file has been constructed to facilitate the storage and retrieval of published and unpublished chemical analyses of glasses and minerals. Some data on the Bishop Tuff are presently stored.

Anderson, A.T.

1983-03-03

203

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...

204

Immersion depth of surfactants at the free water surface: a computer simulation and ITIM analysis study.  

PubMed

The adsorption layer of five different surfactants, namely, pentanol, octanol, dodecanol, dodecyl trimethyl ammonium chloride, and sodium dodecyl sulfate, has been analyzed on the basis of molecular dynamics simulation results at two surface densities, namely, 1 and 4 ?mol/m(2). The analyses have primarily focused on the question of how deeply, in terms of atomistic layers, the different surfactant molecules are immersed into the aqueous phase. The orientation and conformation of the surfactant molecules have also been analyzed. The obtained results reveal a clear difference between the immersion behavior of the alcoholic and ionic surfactants. Thus, alcoholic surfactants are found to be located right at the water surface, their apolar tails not being considerably immersed into the aqueous phase and the alcoholic headgroups being preferentially located in the surface layer of water. Ionic surfactants are immersed several layers deep into the aqueous phase, with headgroup atoms reaching the sixth-eighth and tail carbon atoms reaching the third-fourth subsurface layer in several cases. The observed difference is related, on the one hand, to the ability of the alcoholic surfactants of substituting surface water molecules in their lateral hydrogen bonding network at the water surface and that of their apolar tails for replacing dangling hydrogens and, on the other hand, to the energetic gain of the ionic headgroups if they are fully hydrated rather than being in contact with hydrocarbon tail groups. PMID:23789824

Abrankó-Rideg, Nóra; Darvas, Mária; Horvai, George; Jedlovszky, Pál

2013-07-25

205

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...

206

Interactions among fungal community structure, litter decomposition and depth of water table in a cutover peatland.  

PubMed

Peatlands are important reservoirs of carbon (C) but our understanding of C cycling on cutover peatlands is limited. We investigated the decomposition over 18 months of five types of plant litter (Calluna vulgaris, Eriophorum angustifolium, Eriophorum vaginatum, Picea sitchensis and Sphagnum auriculatum) at a cutover peatland in Scotland, at three water tables. We measured changes in C, nitrogen (N) and phosphorus (P) in the litter and used denaturing gradient gel electrophoresis to investigate changes in fungal community composition. The C content of S. auriculatum litter did not change throughout the incubation period whereas vascular plant litters lost 30-40% of their initial C. There were no differences in C losses between low and medium water tables, but losses were always significantly less at the high water table. Most litters accumulated N and E. angustifolium accumulated significant quantities of P. C, N and P were significant explanatory variables in determining changes in fungal community composition but explained <25% of the variation. Litter type was always a stronger factor than water table in determining either fungal community composition or turnover of C, N and P in litter. The results have implications for the ways restoration programmes and global climate change may impact upon nutrient cycling in cutover peatlands. PMID:18430005

Trinder, Clare J; Johnson, David; Artz, Rebekka R E

2008-06-01

207

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

208

Water calorimetric determination of absorbed dose by 280 kVp orthovoltage X-rays.  

PubMed

The absorbed dose to water from 280 kVp orthovoltage X-rays was determined by a water calorimeter and compared with that determined by an ionization chamber. X-ray qualities of three different filtrations were investigated: they were characterized by 0.57, 0.695 and 1.76 mm of copper half value layers (HVL). The absorbed dose determined by the calorimeter is found higher by 7-9% than that by an ionization chamber. This difference was greater by 4% than that observed for a 60Co beam with the same two detectors. PMID:4081114

Kubo, H

1985-11-01

209

Changing Water Depths in the Eastern Part of Sydney Harbour due to Human Impacts  

NASA Astrophysics Data System (ADS)

Sydney Harbour has been significantly modified by human impacts from the start of the European settlement in 1788. Land clearing has accelerated soil erosion, resulting in increased sedimentation. Dredging has deepened many areas to accommodate ever-larger ships. In this paper a GIS method is used to map bathymetric changes in the eastern part of the harbour from 1903 to more recently. Dredged areas are apparent in the entrance and in wharfage areas, while sedimentation is most marked around the deepest section, which is well inside the harbour itself. In this latter region sediment has built up considerably, to over 3 m in some locations, and ship-induced motions appear to have had an impact. Despite these changes the overall depth of the eastern part of the harbour has changed little. This work is of interest to maritime archaeologists because it brings out the types of processes by which sediments can accumulate and be removed thus altering a harbour's seabed and potentially burying, exposing or erasing archaeological sites and artefacts.

Mulhearn, Phillip

2014-12-01

210

The Potential of Using Worldview-2 Imagery for Shallow Water Depth Mapping  

NASA Astrophysics Data System (ADS)

Worldview-2 is the first very high resolution satellite imagery that has the ability to acquire data of eight bands named: Coastal (400--450 nm), Blue (450--510 nm), Green (510--580 nm), Yellow (585--25 nm), Red (630--690 nm), Red Edge (705--45 nm), Near Infrared(NIR) 1 (770--895 nm) and Near Infrared (NIR) 2 (860--040 nm). Furthermore, five of these bands---Coastal Blue, yellow, red edge and NIR 2 are the new bands in WorldView-2 that are capable of extracting new features that were not possible with previous satellite imagery. Accurate and upto- date bathymetric models are an effective tool for gaining a clearer understanding of the world's waterways, and thus play an important role in many marine applications such as navigation. In this research, the automatic feature extraction technique will be used to locate water area edges. A threshold mask will then be used to determine small land and ships inside the shallow water area. An assessment will be done for all the eight bands to show their contribution to the bathymetry application and shore edge and shallow water outlining, with an emphasis on the yellow and Coastal bands. The conclusion and recommendation will be based on a statistical analysis of the comparison between Worldview-2 data and DEM data for the same area of interest.

Alsubaie, Naif Muidh

211

Wind-forced modulations in crossing sea states over infinite depth water  

NASA Astrophysics Data System (ADS)

The present work is motivated by the work of Leblanc ["Amplification of nonlinear surface waves by wind," Phys. Fluids 19, 101705 (2007)] which showed that Stokes waves grow super exponentially under fair wind as a result of modulational instability. Here, we have studied the effect of wind in a situation of crossing sea states characterized by two obliquely propagating wave systems in deep water. It is found that the wind-forced uniform wave solution in crossing seas grows explosively with a super-exponential growth rate even under a steady horizontal wind flow. This is an important piece of information in the context of the formation of freak waves.

Debsarma, Suma; Senapati, Sudipta; Das, K. P.

2014-09-01

212

Mars outflow channels: A reappraisal of the estimation of water flow velocities from water depths, regional slopes, and channel floor  

E-print Network

2004; revised 25 June 2004; accepted 14 July 2004; published 10 September 2004. [1] Methods used so far to corresponding overestimates of subsurface aquifer permeabilities, rates of filling of depressions with water. Geophys. Res., 109, E09003, doi:10.1029/2004JE002281. 1. Introduction [2] The discharge rates and volumes

Head III, James William

213

The effect of dose and water treatment on EPR signals in irradiated fingernails.  

PubMed

Fast and precise retrospective dosimetry is crucial in making decisions about medical procedures and safety measures in radiation accidents. Electron paramagnetic resonance (EPR) spectroscopy has a potential as one of available biodosimetry methods for use in victims of such incidents. In this study, authors present the findings on EPR dosimetry in fingernails. Authors describe changes of EPR signals in unirradiated and irradiated nails in time after cutting and the effect of water on the mechanically induced and radiation-induced EPR signals measured ex vivo in the fingernails. The effect of dose on amplitude of the EPR signal was measured in nails that were soaked for 10 min in water after their irradiation. The obtained dose-response curves, which reflect changes in concentration of the radiation-induced RIS5 radicals, reach their maximum for doses of 40-60 Gy. PMID:25004939

Marciniak, A; Ciesielski, B; Prawdzik-Dampc, A

2014-11-01

214

Doses and risks from tritiated water and environmental organically bound tritium.  

PubMed

This short review provides an explanation of the calculation and use of the ICRP protection quantities, equivalent and effective dose, including the simplifications introduced by using radiation and tissue weighting factors. It discusses the dose coefficients (Sv Bq(-1) intake) provided by ICRP for intakes of tritiated water (HTO) and organically bound tritium (OBT) and considers uncertainties in the human and animal data on which they are based, including information on the relative biological effectiveness (RBE) of tritium beta particles compared to gamma and x-rays. The review also addresses the specific issue of dose coefficients for ingestion of OBT in Cardiff Bay fish. A distinction is drawn between the adequacy of the ICRP calculation of effective dose to a reference person for the purposes of planning and regulatory control, and the calculation of best estimates of dose and risk to individuals. ICRP will continue to use a radiation weighting factor of 1 for all low LET radiations in the calculation of effective dose, but specific RBE data should be used in risk estimates. Uncertainties in dose coefficients are small for HTO but greater for OBT. The generic consideration of OBT provided by ICRP may not be appropriate for specific organic forms such as OBT in fish. PMID:19690361

Harrison, John

2009-09-01

215

Assessment of dose to man from releases of sup 99 Tc in fresh water systems  

SciTech Connect

The objective of this paper is to evaluate the dose to man from releases of {sup 99}Tc in a fresh water system and to identify the biospheric transfer parameters to which the total dose is the most sensitive. Only internal exposure is taken into account, as the external irradiation leads to a negligible dose contribution. Two release modes were considered: continuous (routine) releases and accidental releases. The concentrations in the biospheric compartments subsequent to routine releases were calculated according to International Atomic Energy Agency procedures. For the accidental releases, a more dynamic approach was adopted, especially for the milk and meat compartments. A routine-release scenario typical for the Mol site has been applied, and the biospheric compartment leading to the highest dose contribution was shown to be the irrigated grain. The biospheric transfer parameters to which the first-year doses were the most sensitive consisted mainly of the mass interception factor for grain and the milk transfer factor. The doses in following years were very dependent on the value of the root zone removal rate. The accidental-release scenario resulted in committed dose equivalent that are strongly influenced by the time of year at which the release occurs. 12 references.

Zeevaert, T.; Vandecasteele, C.M.; Kirchmann, R. (S.C.K./C.E.N. Mol (Belgium))

1989-08-01

216

Natural radioactivity in various water samples and radiation dose estimations in Bolu province, Turkey.  

PubMed

The level of natural radioactivity for Bolu province of north-western Turkey was assessed in this study. There is no information about radioactivity measurement reported in water samples in the Bolu province so far. For this reason, gross ? and ? activities of 55 different water samples collected from tap, spring, mineral, river and lake waters in Bolu were determined. The mean activity concentrations were 68.11 mBq L(-1), 169.44 mBq L(-1) for gross ? and ? in tap water. For all samples the gross ? activity is always higher than the gross ? activity. All value of the gross ? were lower than the limit value of 500 mBq L(-1) while two spring and one mineral water samples were found to have gross ? activity concentrations of greater than 1000 mBq L(-1). The associated age-dependent dose from all water ingestion in Bolu was estimated. The total dose for adults had an average value exceeds the WHO recommended limit value. The risk levels from the direct ingestion of the natural radionuclides in tap and mineral water in Bolu were determinated. The mean (210)Po and (228)Ra risk the value of tap and mineral waters slightly exceeds what some consider on acceptable risk of 10(-4) or less. PMID:25048899

Gorur, F Korkmaz; Camgoz, H

2014-10-01

217

A measurement of the muon-induced neutron yield in lead at a depth of 2850 m water equivalent  

SciTech Connect

We present results from the measurement of the neutron production rate in lead by high energy cosmic-ray muons at a depth of 2850 m water equivalent (mean muon energy of 260 GeV). A tonne-scale highly segmented plastic scintillator detector was utilised to detect both the energy depositions from the traversing muons as well as the delayed radiative capture signals of the induced neutrons. Complementary Monte Carlo simulations reproduce well the distributions of muons and detected muon-induced neutrons. Absolute agreement between simulation and data is of the order of 25%. By comparing the measured and simulated neutron capture rates a neutron yield in pure lead of (5.78{sub ?0.28}{sup +0.21})×10{sup ?3} neutrons/muon/(g/cm{sup 2}) has been obtained.

Reichhart, L.; Ghag, C. [School of Physics and Astronomy, SUPA University of Edinburgh, UK and High Energy Physics Group, Department of Physics and Astronomy, University College London (United Kingdom)] [School of Physics and Astronomy, SUPA University of Edinburgh, UK and High Energy Physics Group, Department of Physics and Astronomy, University College London (United Kingdom); Lindote, A.; Chepel, V.; DeViveiros, L.; Lopes, M. I.; Neves, F.; Pinto da Cunha, J.; Silva, C.; Solovov, V. N. [LIP-Coimbra and Department of Physics of the University of Coimbra (Portugal)] [LIP-Coimbra and Department of Physics of the University of Coimbra (Portugal); Akimov, D. Yu.; Belov, V. A.; Burenkov, A. A.; Kobyakin, A. S.; Kovalenko, A. G.; Stekhanov, V. N. [Institute for Theoretical and Experimental Physics, Moscow (Russian Federation)] [Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); Araújo, H. M.; Bewick, A.; Currie, A.; Horn, M. [High Energy Physics Group, Blackett Laboratory, Imperial College London (United Kingdom)] [High Energy Physics Group, Blackett Laboratory, Imperial College London (United Kingdom); and others

2013-08-08

218

DEVELOPMENT OF DUAL ANCHORED SHEET PILE WALL METHOD TO INCREASE FRONT WATER DEPTH AND SEISMIC RESISTANCE OF EXISTING QUAY  

NASA Astrophysics Data System (ADS)

Recently the dual anchored sheet pile wall method has been developed to increase a front water depth and seismic resistance of existing quay walls by providing an additional anchor in the lower level of them to reduce a flexural moment of the sheet piles and a tension of the anchors. The existing technical information is not enough to evaluate the seismic behavior and the retrofit of the quay walls with anchors at two different levels. Therefore the experiments with a scale model set on the vibration table of the centrifugal apparatus as well as two dimensional effective stress analyses have been mobilized to investigate the seismic retrofit of the dual anchored sheet pile wall. The experiments and analyses demonstrate the increase the earthquake resistance of quay walls, because they showed the additional anchor can reduce the stress of the sheet walls to one half.

Nakamura, Yasushi; Sato, Masakatsu; Kikuchi, Yoshiaki; Sugano, Takahiro; Morikawa, Yoshiyuki; Hoshino, Masami; Miki, Kenichi

219

Korean coastal water depth/sediment and land cover mapping (1:25,000) by computer analysis of LANDSAT imagery  

NASA Technical Reports Server (NTRS)

Computer analysis was applied to single date LANDSAT MSS imagery of a sample coastal area near Seoul, Korea equivalent to a 1:50,000 topographic map. Supervised image processing yielded a test classification map from this sample image containing 12 classes: 5 water depth/sediment classes, 2 shoreline/tidal classes, and 5 coastal land cover classes at a scale of 1:25,000 and with a training set accuracy of 76%. Unsupervised image classification was applied to a subportion of the site analyzed and produced classification maps comparable in results in a spatial sense. The results of this test indicated that it is feasible to produce such quantitative maps for detailed study of dynamic coastal processes given a LANDSAT image data base at sufficiently frequent time intervals.

Park, K. Y.; Miller, L. D.

1978-01-01

220

Korean coastal water depth/sediment and land cover mapping /1:25,000/ by computer analysis of Landsat imagery  

NASA Technical Reports Server (NTRS)

Computer analysis was applied to single data Landsat MSS imagery of a coastal area near Seoul, Korea equivalent to a 1:50,000 topographic map, and featuring large dynamic sediment transport processes. Supervised image processing yielded a test classification map containing five water depth/sediment classes, two shoreline/tidal classes and five coastal land cover classes at a scale of 1:25,000 and with a training set accuracy of 76%; the training sets were selected by direct examination of the digitally displayed imagery. The unsupervised ISOCLAS (Senkus, 1976) clustering analysis was performed to assess the relative value of this approach to image classification in areas of sparse or nonexistent ground control. Results indicate that it is feasible to produce quantitative maps for detailed study of dynamic coastal processes given a Landsat image data base at sufficiently frequent time intervals.

Park, K. Y.; Miller, L. D.

1980-01-01

221

Instrumentation for investigation of the depth-dose distribution by the Liulin-5 instrument of a human phantom on the Russian segment of ISS for estimation of the radiation risk during long term space flights.  

PubMed

Described is the Liulin-5 experiment and instrumentation, developed for investigation of the space radiation doses depth distribution in a human phantom on the Russian Segment of the International Space Station (ISS). Liulin-5 experiment is a part of the international project MATROSHKA-R on ISS. The experiment MATROSHKA-R is aimed to study the depth dose distribution at the sites of critical organs of the human body, using models of human body-anthropomorphic and spherical tissue-equivalent phantoms. The aim of Liulin-5 experiment is long term (4-5 years) investigation of the radiation environment dynamics inside the spherical tissue-equivalent phantom, mounted in different places of the Russian Segment of 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 by a telescope of silicon detectors. Data obtained together with data from other active and passive dosimeters will be used to estimate the radiation risk to the crewmembers, verify the models of radiation environment in low Earth orbit, validate body transport model and correlate organ level dose to skin dose. Presented are the test results of the prototype unit. The spherical phantom will be flown on the ISS in 2004 year and Liulin-5 experiment is planned for 2005 year. PMID:15880917

Semkova, J; Koleva, R; Todorova, G; Kanchev, N; Petrov, V; Shurshakov, V; Tchhernykh, I; Kireeva, S

2004-01-01

222

A depth-averaged 2-D shallow water model for breaking and non-breaking long waves affected by rigid vegetation  

Technology Transfer Automated Retrieval System (TEKTRAN)

This paper presents a depth-averaged two-dimensional shallow water model for simulating long waves in vegetated water bodies under breaking and non-breaking conditions. The effects of rigid vegetation are modelled in the form of drag and inertia forces as sink terms in the momentum equations. The dr...

223

Late Quaternary water depth changes in Hala Lake, northeastern Tibetan Plateau, derived from ostracod assemblages and sediment properties in multiple sediment records  

NASA Astrophysics Data System (ADS)

Late Pleistocene and Holocene climate dynamics along the marginal belt of the East Asian Summer Monsoon in China and their responses to hydrological cycles in lake basins of the Tibetan Plateau are still a matter of scientific discussion. Hala Lake, a closed 65 m deep lake basin in the western Qilian Mountains, Qinghai Province, is considered a monitor of climate-driven hydrological and environmental changes during the past 24 kyr BP. The distribution patterns of ostracod assemblages, stable isotopes, sediment-geochemical properties in four sediment records from different water depths and their combination with the unique limnological setting enabled us to reconstruct four major phases of centennial-scale water depth fluctuations from the global Last Glacial Maximum (ca 24 kyr BP) to the Present. Our results show that Hala Lake experienced a very shallow and small water body during the LGM and Lateglacial under cold and dry climate conditions. Rapid increase of water depth and contemporaneous lake expansion started at around 14 kyr BP (Phase I), most likely as a result of glacier melt due to the onset of climate warming. The lake reached >45 m water depth at around 13.5 kyr BP. Reduced water depth during the Younger Dryas spell (ca 12 kyr BP) may be attributed to a short-term return to cooler and drier conditions. During the early Holocene (Phase II), water depth increased further toward lake highstands close to its present level, with a highest lake level of up to 9 m above the present lakestand at 8.0-7.8 kyr BP. Besides continued glacier melt supply, we assume that summer monsoon effective moisture contributed to the overall water budget, but remained relatively unstable, favoring water depth fluctuations. A pronounced lower water depth falls into the period between 9.2 and 8.1 kyr BP, perhaps the result of weak monsoon influence or its complete absence, although the warming trend continued toward its optimum at ca 8-7 kyr BP. A distinct mass flow, most likely triggered by an earthquake, occurred during a lake lowstand either at ca 7.0 kyr BP or at around 8.1 kyr BP. The mid-Holocene (Phase III) was characterized by fluctuating water depths between 7.8 and 4.5 kyr BP. Conflicting trends of stable isotope data limit the validity of water depth estimations, but may show higher lake levels between 5.5 and 4.5 kyr BP, coincident with dated lake sediments in a cliff position at the northern lake shore. This positive water balance can most likely be attributed to increased westerly-derived moisture supply during autumn and late winter, although summer monsoon influence could also be of significance. Coincident with the 4.2 ka event, the lake experienced shallow water at around 4.1 kyr BP, perhaps as a result of continued cooling and drier climate conditions, supporting the arguments of a general cooling trend throughout the Holocene. The Late Holocene (Phase IV) is characterized by extremely unstable hydrological conditions with rapid fluctuations in water depth, more frequently controlled by westerly-driven effective moisture supply. Since the lake lowstand at about 1.4-1.2 kyr BP, the lake has developed toward its present level. Our research underlines the necessity for comparing multiple proxy records from different lake sites to better evaluate centennial-scale climate-driven variations throughout the late Pleistocene and Holocene periods. All presented data suggest the variable influence of summer monsoon effective moisture on the hydrological budget of the lake. Water depth variations did not follow the long-term pattern of the Asian monsoon system due to a potential modulation by westerly-derived moisture impact.

Yan, Dada; Wünnemann, Bernd

2014-07-01

224

Radiological characterization of tap waters in Croatia and the age dependent dose assessment.  

PubMed

Activity concentrations of (234)U, (238)U, (226)Ra, (228)Ra, (210)Po and (210)Pb in tap waters, originating from various geological regions of Croatia, were determined. Activity concentrations of measured radionuclides are in general decreasing in this order: (238)U?(234)U>(228)Ra?(210)Pb>(226)Ra?(210)Po. Based on the radionuclide activity concentrations average total annual internal doses for infants, children and adults, as well as contribution of each particular radionuclide to total dose, were assessed and discussed. The highest doses were calculated for infants, which makes them the most critical group of population. All values for each population group were well below the recommended reference dose level (RDL) of 0.1mSv from one year's consumption of drinking water according to European Commission recommendations from 1998. Contribution of each particular radionuclide to total doses varied among different age groups but for each group the lowest contribution was found for (226)Ra and the highest for (228)Ra. PMID:24997928

Rožmari?, Martina; Rogi?, Matea; Benedik, Ljudmila; Bariši?, Delko; Planinšek, Petra

2014-09-01

225

A feasibility study to estimate minimum surface-casing depths of oil and gas wells to prevent ground-water contamination in four areas of western Pennsylvania  

USGS Publications Warehouse

Hydrologic data were evaluated from four areas of western Pennsylvania to estimate the minimum depth of well surface casing needed to prevent contamination of most of the fresh ground-water resources by oil and gas wells. The areas are representative of the different types of oil and gas activities and of the ground-water hydrology of most sections of the Appalachian Plateaus Physiographic Province in western Pennsylvania. Approximate delineation of the base of the fresh ground-water system was attempted by interpreting the following hydrologic data: (1) reports of freshwater and saltwater in oil and gas well-completion reports, (2) water well-completion reports, (3) geophysical logs, and (4) chemical analyses of well water. Because of the poor quality and scarcity of ground-water data, the altitude of the base of the fresh ground-water system in the four study areas cannot be accurately delineated. Consequently, minimum surface-casing depths for oil and gas wells cannot be estimated with confidence. Conscientious and reliable reporting of freshwater and saltwater during drilling of oil and gas wells would expand the existing data base. Reporting of field specific conductance of ground water would greatly enhance the value of the reports of ground water in oil and gas well-completion records. Water-bearing zones in bedrock are controlled mostly by the presence of secondary openings. The vertical and horizontal discontinuity of secondary openings may be responsible, in part, for large differences in altitudes of freshwater zones noted on completion records of adjacent oil and gas wells. In upland and hilltop topographies, maximum depths of fresh ground water are reported from several hundred feet below land surface to slightly more than 1,000 feet, but the few deep reports are not substantiated by results of laboratory analyses of dissolved-solids concentrations. Past and present drillers for shallow oil and gas wells commonly install surface casing to below the base of readily observed fresh ground water. Casing depths are selected generally to maximize drilling efficiency and to stop freshwater from entering the well and subsequently interfering with hydrocarbon recovery. The depths of surface casing generally are not selected with ground-water protection in mind. However, on the basis of existing hydrologic data, most freshwater aquifers generally are protected with current casing depths. Minimum surface-casing depths for deep gas wells are prescribed by Pennsylvania Department of Environmental Resources regulations and appear to be adequate to prevent ground-water contamination, in most respects, for the only study area with deep gas fields examined in Crawford County.

Buckwalter, T.F.; Squillace, P.J.

1995-01-01

226

Seasonal changes in depth of water uptake for encroaching trees Juniperus virginiana and Pinus ponderosa and two dominant C4 grasses in a semiarid grassland.  

PubMed

We used the natural abundance of stable isotopic ratios of hydrogen and oxygen in soil (0.05-3 m depth), plant xylem and precipitation to determine the seasonal changes in sources of soil water uptake by two native encroaching woody species (Pinus ponderosa P. & C. Lawson, Juniperus virginiana L.), and two C(4) grasses (Schizachyrium scoparium (Michx.) Nash, Panicum virgatum L.), in the semiarid Sandhills grasslands of Nebraska. Grass species extracted most of their water from the upper soil profile (0.05-0.5 m). Soil water uptake from below 0.5 m depth increased under drought, but appeared to be minimal in relation to the total water use of these species. The grasses senesced in late August in response to drought conditions. In contrast to grasses, P. ponderosa and J. virginiana trees exhibited significant plasticity in sources of water uptake. In winter, tree species extracted a large fraction of their soil water from below 0.9 m depth. In spring when shallow soil water was available, tree species used water from the upper soil profile (0.05-0.5 m) and relied little on water from below 0.5 m depth. During the growing season (May-August) significant differences between the patterns of tree species water uptake emerged. Pinus ponderosa acquired a large fraction of its water from the 0.05-0.5 and 0.5-0.9 m soil profiles. Compared with P. ponderosa, J. virginiana acquired water from the 0.05-0.5 m profile during the early growing season but the amount extracted from this profile progressively declined between May and August and was mirrored by a progressive increase in the fraction taken up from 0.5-0.9 m depth, showing plasticity in tracking the general increase in soil water content within the 0.5-0.9 m profile, and being less responsive to growing season precipitation events. In September, soil water content declined to its minimum, and both tree species shifted soil water uptake to below 0.9 m. Tree transpiration rates (E) and water potentials (Psi) indicated that deep water sources did not maintain E which sharply declined in September, but played an important role in the recovery of tree Psi. Differences in sources of water uptake among these species and their ecological implications on tree-grass dynamics and soil water in semiarid environments are discussed. PMID:19203941

Eggemeyer, Kathleen D; Awada, Tala; Harvey, F Edwin; Wedin, David A; Zhou, Xinhua; Zanner, C William

2009-02-01

227

Empirical water depth predictions in Dublin Bay based on satellite EO multispectral imagery and multibeam data using spatially weighted geographical analysis  

NASA Astrophysics Data System (ADS)

The coastal shallow water zone can be a challenging and expensive environment within which to acquire bathymetry and other oceanographic data using traditional survey methods. Dangers and limited swath coverage make some of these areas unfeasible to survey using ship borne systems, and turbidity can preclude marine LIDAR. As a result, an extensive part of the coastline worldwide remains completely unmapped. Satellite EO multispectral data, after processing, allows timely, cost efficient and quality controlled information to be used for planning, monitoring, and regulating coastal environments. It has the potential to deliver repetitive derivation of medium resolution bathymetry, coastal water properties and seafloor characteristics in shallow waters. Over the last 30 years satellite passive imaging methods for bathymetry extraction, implementing analytical or empirical methods, have had a limited success predicting water depths. Different wavelengths of the solar light penetrate the water column to varying depths. They can provide acceptable results up to 20 m but become less accurate in deeper waters. The study area is located in the inner part of Dublin Bay, on the East coast of Ireland. The region investigated is a C-shaped inlet covering an area of 10 km long and 5 km wide with water depths ranging from 0 to 10 m. The methodology employed on this research uses a ratio of reflectance from SPOT 5 satellite bands, differing to standard linear transform algorithms. High accuracy water depths were derived using multibeam data. The final empirical model uses spatially weighted geographical tools to retrieve predicted depths. The results of this paper confirm that SPOT satellite scenes are suitable to predict depths using empirical models in very shallow embayments. Spatial regression models show better adjustments in the predictions over non-spatial models. The spatial regression equation used provides realistic results down to 6 m below the water surface, with reliable and error controlled depths. Bathymetric extraction approaches involving satellite imagery data are regarded as a fast, successful and economically advantageous solution to automatic water depth calculation in shallow and complex environments.

Monteys, Xavier; Harris, Paul; Caloca, Silvia

2014-05-01

228

Bacterial diversity and biogeochemistry of different chemosynthetic habitats of the REGAB cold seep (West African margin, 3160 m water depth)  

NASA Astrophysics Data System (ADS)

The giant pockmark REGAB (West African margin, 3160 m water depth) is an active methane-emitting cold seep ecosystem, where the energy derived from microbially mediated oxidation of methane supports high biomass and diversity of chemosynthetic communities. Bare sediments interspersed with heterogeneous chemosynthetic assemblages of mytilid mussels, vesicomyid clams and siboglinid tubeworms form a complex seep ecosystem. To better understand if benthic bacterial communities reflect the patchy distribution of chemosynthetic fauna, all major chemosynthetic habitats at REGAB were investigated using an interdisciplinary approach combining pore water geochemistry, in situ quantification of fluxes and consumption of methane, as well as bacterial community fingerprinting. This study revealed that sediments populated by different fauna assemblages show distinct biogeochemical activities and are associated with distinct sediment bacterial communities. The methane consumption rates and methane effluxes ranged over one to two orders of magnitude across habitats, and reached highest values at the mussel habitat, which hosted a different bacterial community compared to the other habitats. Clam assemblages had a profound impact on the sediment geochemistry, but less so on the bacterial community structure. Moreover, all clam assemblages at REGAB were restricted to sediments characterized by complete methane consumption in the seafloor, and intermediate biogeochemical activity. Overall, variations in the sediment geochemistry were reflected in the distribution of both fauna and microbial communities; and were mostly determined by methane flux.

Pop Ristova, P.; Wenzhöfer, F.; Ramette, A.; Zabel, M.; Fischer, D.; Kasten, S.; Boetius, A.

2012-12-01

229

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

230

Airborne Sunphotometer Measurements of Aerosol Optical Depth and Water Vapor in ACE-Asia and Their Comparisons to Correlative Measurements  

NASA Technical Reports Server (NTRS)

In the Spring 2001 phase of the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia), the 6-channel NASA Ames Airborne Tracking Sunphotometer (AATS-6) operated on 15 of the 19 research flights of the NCAR C-130, while its 14-channel counterpart (AATS-14) flew successfully on all 19 research flights of the CIRPAS Twin Otter. ACE-Asia studied aerosol outflow from the Asian continent to the Pacific basin. It was designed to integrate suborbital and satellite measurements and models to reduce the uncertainty in calculations of the climate forcing due to aerosols. AATS-6 and AATS-14 measured solar beam transmission at six and 14 wavelengths (380-1021 and 354-1558 nm, respectively), yielding aerosol optical depth (AOD) spectra and columnar water vapor (CWV). Vertical differentiation in profiles yielded aerosol extinction spectra and water vapor concentration. In this paper, we plan to present examples of the following, preliminary findings that are based in part on our airborne sunphotometer measurements: (1) The wavelength dependence of sunphotometer-derived AOD and extinction indicates that supermicron dust was often a major component of the aerosol, frequently extending to high altitudes. The percentage of full-column AOD (525 nm) that Jay above 3 km was typically 34+/-13%. In contrast, the analogous percentage of columnar water vapor was only 10+/-4%; (2) Initial comparison studies between AOD data obtained by AATS-6 and AATS-14 during coordinated low-level flight legs show agreement well within the instruments' error bars; (3) Aerosol extinction has been derived from airborne in situ measurements of scattering (nephelometers) and absorption (particle soot/ absorption photometer, PSAP) or calculated from particle size distribution measurements (mobility analyzers and aerodynamic particle sizers). Comparison with corresponding extinction values derived from the Ames airborne sunphotometer measurements shows good agreement for the vertical distribution of aerosol layers. However, the level of agreement in absolute magnitude of the derived aerosol extinction/optical depth varied among the aerosol layers sampled; (4) Initial comparisons of sunphotometer and satellite-derived AOD using SeaWiFS, MISR and AVHRR show promising results. We also plan to include comparisons with MODIS and TOMS: (5) Initial comparisons of sunphotometer-derived AOD and aerosol extinction profiles with lidars in Tokyo and on a ship show reasonable agreement.

Schmid, B.; Redemann, J.; Livingston, J.; Russell, P.; Hegg, D.; Wang, J.; Kahn, R.; Hsu, C.; Masonis, S.; Murayama, T.; Hipskind, R. Stephen (Technical Monitor)

2002-01-01

231

Relationships between inherent optical properties and the depth of penetration of solar radiation in optically complex coastal waters  

NASA Astrophysics Data System (ADS)

The attenuation of downward planar irradiance can be quantified by KŻd>(E10%,?>), the diffuse attenuation coefficient calculated from the surface to the depth where the irradiance Ed at wavelength ? falls to 10% of its surface value. Theoretical studies by Gordon (1989) and Lee et al. (2005a) suggest that KŻd>(E10%,?>)can be derived from the absorption coefficient, a(?) and the backscattering coefficient, bb(?), using equations incorporating either the solar zenith angle (?a) or the subsurface distribution function (D0) and empirical coefficients derived by radiative transfer modeling. These results have not, however, been validated against in situ measurements. We have therefore assessed the performance of both models using measurements of a(?), bb(?), and KŻd>(E10%,?>) for 100 stations in UK coastal waters. Best results were obtained from the Lee et al. (2005a) model, for which over 90% of the predicted KŻd>(E10%,?>) values in the 440 nm to 665 nm range were within ±0.1 m-1 of those measured in situ. A strong linear relationship (R2> 0.95, mean relative difference 5.4%) was found between KŻd>(E10%>) at 490 nm and the reciprocal of the depth of the midpoint of the euphotic zone (z10%, PAR). This allowed (z10%, PAR) to be predicted from measured values of a(490 nm), bb(490 nm) and ?a, using the Lee et al. model as an intermediate step, with an RMS error of 1.25 m over the 2.5-25.0 m range covered by our data set.

Cunningham, Alex; Ramage, Leanne; McKee, David

2013-05-01

232

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

233

The effect of drought and interspecific interactions on depth of water uptake in deep- and shallow-rooting grassland species as determined by ?18O natural abundance  

NASA Astrophysics Data System (ADS)

Increased incidence of drought, as predicted under climate change, has the potential to negatively affect grassland production. Compared to monocultures, vertical belowground niche complementarity between shallow- and deep-rooting species may be an important mechanism resulting in higher yields and higher resistance to drought in grassland mixtures. However, very little is known about the belowground responses in grassland systems and increased insight into these processes may yield important information both to predict the effect of future climate change and better design agricultural systems to cope with this. This study assessed the effect of a 9-week experimental summer drought on the depth of water uptake of two shallow-rooting species (Lolium perenne L. and Trifolium repens L.) and two deep-rooting species (Cichorium intybus L. and Trifolium pratense L.) in grassland monocultures and four-species mixtures by using the natural abundance ?18O isotope method. We tested the following three hypotheses: (1) drought results in a shift of water uptake to deeper soil layers, (2) deep-rooting species take up a higher proportion of water from deeper soil layers relative to shallow-rooting species, and (3) as a result of interspecific interactions in mixtures, the water uptake of shallow-rooting species becomes shallower when grown together with deep-rooting species and vice versa, resulting in reduced niche overlap. The natural abundance ?18O technique provided novel insights into the depth of water uptake of deep- and shallow- rooting grassland species and revealed large shifts in depth of water uptake in response to drought and interspecific interactions. Compared to control conditions, drought reduced the proportional water uptake from 0-10 cm soil depth (PCWU0-10) of L. perenne, T. repens and C. intybus in monocultures by on average 54%. In contrast, the PCWU0-10 of T. pratense in monoculture increased by 44%, and only when grown in mixture did the PCWU0-10 of T. pratense decrease under drought conditions. In line with hypothesis (2), in monoculture, the PCWU0-10 of shallow-rooting species L. perenne and T. repens was 0.53 averaged over the two drought treatments, compared to 0.16 for the deep-rooting C. intybus. Surprisingly, in monoculture, water uptake by T. pratense was shallower than for the shallow-rooting species (PCWU0-10 = 0.68). Interspecific interactions in mixtures resulted in a shift in the depth of water uptake by the different species. As hypothesised, the shallow-rooting species L. perenne and T. repens tended to become shallower, and the deep-rooting T. pratense made a dramatic shift to deeper soil layers (reduction in PCWU0-10 of 58% on average) in mixture compared to monoculture. However, these shifts did not result in a reduction in the proportional similarity of the proportional water uptake from different soil depth intervals (niche overlap) in mixtures compared to monocultures. There was no clear link between interspecific differences in depth of water uptake and the reduction of biomass production under drought compared to control conditions (drought resistance). Cichorium intybus, the species with water uptake from the deepest soil layers was one of the species most affected by drought. Interestingly, T. pratense, which was least affected by drought, also had the greatest plasticity in depth of water uptake. This suggests that there may be an indirect effect of rooting depth on drought resistance, as it determines the potential plasticity in the depth of water uptake.

Hoekstra, N. J.; Finn, J. A.; Hofer, D.; Lüscher, A.

2014-08-01

234

Radon concentrations in drinking water in Beijing City, China and contribution to radiation dose.  

PubMed

(222)Rn concentrations in drinking water samples from Beijing City, China, were determined based on a simple method for the continuous monitoring of radon using a radon-in-air monitor coupled to an air-water exchanger. A total of 89 water samples were sampled and analyzed for their (222)Rn content. The observed radon levels ranged from detection limit up to 49 Bq/L. The calculated arithmetic and geometric means of radon concentrations in all measured samples were equal to 5.87 and 4.63 Bq/L, respectively. The average annual effective dose from ingestion of radon in drinking water was 2.78 ?Sv, and that of inhalation of water-borne radon was 28.5 ?Sv. It is concluded that it is not the ingestion of waterborne radon, but inhalation of the radon escaping from water that is a substantial part of the radiological hazard. Radon in water is a big concern for public health, especially for consumers who directly use well water with very high radon concentration. PMID:25350007

Wu, Yun-Yun; Ma, Yong-Zhong; Cui, Hong-Xing; Liu, Jian-Xiang; Sun, Ya-Ru; Shang, Bing; Su, Xu

2014-11-01

235

Radon Concentrations in Drinking Water in Beijing City, China and Contribution to Radiation Dose  

PubMed Central

222Rn concentrations in drinking water samples from Beijing City, China, were determined based on a simple method for the continuous monitoring of radon using a radon-in-air monitor coupled to an air-water exchanger. A total of 89 water samples were sampled and analyzed for their 222Rn content. The observed radon levels ranged from detection limit up to 49 Bq/L. The calculated arithmetic and geometric means of radon concentrations in all measured samples were equal to 5.87 and 4.63 Bq/L, respectively. The average annual effective dose from ingestion of radon in drinking water was 2.78 ?Sv, and that of inhalation of water-borne radon was 28.5 ?Sv. It is concluded that it is not the ingestion of waterborne radon, but inhalation of the radon escaping from water that is a substantial part of the radiological hazard. Radon in water is a big concern for public health, especially for consumers who directly use well water with very high radon concentration. PMID:25350007

Wu, Yun-Yun; Ma, Yong-Zhong; Cui, Hong-Xing; Liu, Jian-Xiang; Sun, Ya-Ru; Shang, Bing; Su, Xu

2014-01-01

236

Depth to water, 1991, in the Rathdrum Prairie, Idaho; Spokane River valley, Washington; Moscow-Lewiston-Grangeville area, Idaho; and selected intermontane valleys, east-central Idaho  

USGS Publications Warehouse

This map report illustrates digitally generated depth-to-water zones for the Rathdrum Prairie in Idaho; part of the Spokane River Valley in eastern Washington; and the intermontane valleys of the upper Big Wood, Big Lost, Pahsimeroi, Little Lost, and Lemhi Rivers and Birch Creek in Idaho. Depth to water is 400 to 500 feet below land surface in the northern part of Rathdrum Prairie, 100 to 200 feet below land surface at the Idaho-Washington State line, and 0 to 250 feet below land surface in the Spokane area. Depth to water in the intermontane valleys in east-central Idaho is least (usually less than 50 feet) near streams and increases toward valley margins where mountain-front alluvial fans have formed. Depths to water shown in the Moscow-Lewiston-Grangeville area in Idaho are limited to point data at individual wells because most of the water levels measured were not representative of levels in the uppermost aquifer but of levels in deeper aquifers.

Berenbrock, Charles E.; Bassick, M.D.; Rogers, T.L.; Garcia, S.P.

1995-01-01

237

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

2007-06-01

238

Dose optimization of proton and heavy ion therapy using generalized sampled pattern matching  

Microsoft Academic Search

We have proposed a new dose optimization method for proton and heavy ion therapy using generalized sampled pattern matching, where an optimal beam weight distribution for scanning is obtained as a solution. Using water phantom models, one-dimensional lateral and depth dose distributions were separately optimized, each resulting in a uniform dose distribution within a target region and minimum dose fall-off

Kiyoshi Yoda; Yoshifuru Saito; Hidenobu Sakamoto

1997-01-01

239

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 process-based mathematical model ecosys to study effects of seasonal variation in WTD on net ecosystem productivity (NEP) of a drainage affected tropical peat swamp forest at Palangkaraya, Indonesia. Simulated NEP suggested that the peatland was a C source (NEP ~ -2 g C m-2 d-1, where a negative sign represents a C source and a positive sign a C sink) during rainy seasons with shallow WTD, C neutral or a small sink (NEP ~ +1 g C m-2 d-1) during early dry seasons with intermediate WTD and a substantial C source (NEP ~ -4 g C m-2 d-1) during late dry seasons with deep WTD from 2002 to 2005. These values were corroborated by regressions (P < 0.0001) of hourly modelled vs. eddy covariance (EC) net ecosystem CO2 fluxes which yielded R2 > 0.8, intercepts approaching 0 and slopes approaching 1. We also simulated a gradual increase in annual NEP from 2002 (-609 g C m-2) to 2005 (-373 g C m-2) with decreasing WTD which was attributed to declines in duration and intensity of dry seasons following the El Nińo event of 2002. This increase in modelled NEP was corroborated by EC-gap filled annual NEP estimates. Our modelling hypotheses suggested that (1) poor aeration in wet soils during shallow WTD caused slow nutrient (predominantly phosphorus) mineralization and consequent slow plant nutrient uptake that suppressed gross primary productivity (GPP) and hence NEP (2) better soil aeration during intermediate WTD enhanced nutrient mineralization and hence plant nutrient uptake, GPP and NEP and (3) deep WTD suppressed NEP through a combination of reduced GPP due to plant water stress and increased ecosystem respiration (Re) from enhanced deeper peat aeration. 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 carbon, nitrogen and phosphorus transformations within a soil-plant-atmosphere water transfer scheme driven by water potential gradients. Including these processes in ecosystem models should therefore provide an improved predictive capacity for WTD management programs intended to reduce tropical peat degradation.

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

2014-02-01

240

ACE-Asia Aerosol Optical Depth and Water Vapor Measured by Airborne Sunphotometers and Related to Other Measurements and Calculations  

NASA Technical Reports Server (NTRS)

In the Spring 2001 phase of the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia), the 6-channel NASA Ames Airborne Tracking Sunphotometer (AATS-6) operated on 15 of the 19 research flights of the NCAR C-130, while its 14-channel counterpart (AATS- 14) flew successfully on all 18 research flights of the CIRPAS Twin Otter. ACE-Asia studied aerosol outflow from the Asian continent to the Pacific basin. It was designed to integrate suborbital and satellite measurements and models so as to reduce the uncertainty in calculations of the climate forcing due to aerosols. AATS-6 and AATS-14 measured solar beam transmission at 6 and 14 wavelengths (380-1021 and 354-1558 nm, respectively), yielding aerosol optical depth (AOD) spectra and column water vapor (CWV). Vertical differentiation in profiles yielded aerosol extinction spectra and water vapor concentration. The wavelength dependence of these AOD and extinction spectra indicates that supermicron dust was often a major component of the ACE-Asia aerosol. Frequently this dust-containing aerosol extended to high altitudes. For example, in AATS- 14 profiles analyzed to date, 36% of full-column AOD at 525 nm was above 3 km. In contrast, only 10% of CWV was above 3 km. Analyses and applications of AATS-6 and AATS-14 data to date include comparisons to (i) extinction products derived using in situ measurements, (ii) extinction profiles derived from lidar measurements, and (iii) AOD retrievals from the Multi-angle Imaging Spectro-Radiometer (MISR) aboard the TERRA satellite. Other planned collaborative studies include comparisons to results from size spectrometers, chemical measurements, other satellite sensors, flux radiometers, and chemical transport models. Early results of these studies will be presented.

Livingston, John M.; Russell, P. B.; Schmid, B.; Redemann, J.; Eilers, J. A.; Ramirez, S. A.; Kahn, R.; Hegg, D.; Pilewskie, P.; Anderson, T.; Hipskind, R. Stephen (Technical Monitor)

2001-01-01

241

Active probing of cloud multiple scattering, optical depth, vertical thickness, and liquid water content using wide-angle imaging LIDAR.  

SciTech Connect

At most optical wavelengths, laser light in a cloud lidar experiment is not absorbed but merely scattered out of the beam, eventually escaping the cloud via multiple scattering. There is much information available in this light scattered far from the input beam, information ignored by traditional 'on-beam' lidar. Monitoring these off-beam returns in a fully space- and time-resolved manner is the essence of our unique instrument, Wide Angle Imaging Lidar (WAIL). In effect, WAIL produces wide-field (60-degree full-angle) 'movies' of the scattering process and records the cloud's radiative Green functions. A direct data product of WAIL is the distribution of photon path lengths resulting from multiple scattering in the cloud. Following insights from diffusion theory, we can use the measured Green functions to infer the physical thickness and optical depth of the cloud layer, and, from there, estimate the volume-averaged liquid water content. WAIL is notable in that it is applicable to optically thick clouds, a regime in which traditional lidar is reduced to ceilometry. Here we present recent WAIL data oti various clouds and discuss the extension of WAIL to full diurnal monitoring by means of an ultra-narrow magneto-optic atomic line filter for daytime measurements.

Love, Steven P.; Davis, A. B. (Anthony B.); Rohde, C. A. (Charles A.); Tellier, L. L. (Larry L.); Ho, Cheng,

2002-01-01

242

Assessment of total body water in hemodialysis patients by a single oral dose of antipyrine.  

PubMed

Accurate determination of total body water in hemodialysis patients is important for calculation of the amount of fluid excess that should be removed by ultrafiltration, and for dialysis prescribing by KT/V. Indirect methods using 0.6 x body weight or pre and post serum urea concentrations are inaccurate and determination by tritiated water space requires the use of radioactivity. The authors measured the volume of distribution for antipyrine that is distributed in body water, and compared it to tritiated water space in hemodialysis patients. Sixteen patients on hemodialysis were given 500 mg antipyrine and saliva samples were collected at fixed time points. Concentrations of antipyrine in saliva were measured by high pressure liquid chromatography. Volume of distribution for antipyrine was calculated by pharmacokinetic methods. Fluid excess was determined as the difference between tritiated water space or volume of distribution for antipyrine and ideal total body water measured anthropometrically. Total body water as the volume of distribution for antipyrine was 24.8 to 61.5 (mean 44.0 +/- 10.3) L, or 68% of body weight, and tritiated water space 27.0 to 56.6 L (43.6 +/- 7.7), 67% of body weight. Volume of distribution for antipyrine correlated well with tritiated water space (r = 0.997 and p = 0.001). Fluid excess calculated from tritiated water space was between 2.5 and 12.4 (6.0 +/- 4.0) L, and from volume of distribution for antipyrine -0.7 to 13.3 (5.7 +/- 5.1) L (r = 0.80, p = 0.001). The authors conclude that by using a single oral dose of antipyrine, one can simply and accurately measures total body water in hemodialysis patients. PMID:8828783

Odar-Cederlöf, I; Eriksson, C G; Albertioni, F; Ericsson, F; Kjellstrand, C M

1996-01-01

243

No shift to a deeper water uptake depth in response to summer drought of two lowland and sub-alpine C3-grasslands in Switzerland.  

PubMed

Temperate C3-grasslands are of high agricultural and ecological importance in Central Europe. Plant growth and consequently grassland yields depend strongly on water supply during the growing season, which is projected to change in the future. We therefore investigated the effect of summer drought on the water uptake of an intensively managed lowland and an extensively managed sub-alpine grassland in Switzerland. Summer drought was simulated by using transparent shelters. Standing above- and belowground biomass was sampled during three growing seasons. Soil and plant xylem waters were analyzed for oxygen (and hydrogen) stable isotope ratios, and the depths of plant water uptake were estimated by two different approaches: (1) linear interpolation method and (2) Bayesian calibrated mixing model. Relative to the control, aboveground biomass was reduced under drought conditions. In contrast to our expectations, lowland grassland plants subjected to summer drought were more likely (43-68 %) to rely on water in the topsoil (0-10 cm), whereas control plants relied less on the topsoil (4-37 %) and shifted to deeper soil layers (20-35 cm) during the drought period (29-48 %). Sub-alpine grassland plants did not differ significantly in uptake depth between drought and control plots during the drought period. Both approaches yielded similar results and showed that the drought treatment in the two grasslands did not induce a shift to deeper uptake depths, but rather continued or shifted water uptake to even more shallower soil depths. These findings illustrate the importance of shallow soil depths for plant performance under drought conditions. PMID:25273953

Prechsl, Ulrich E; Burri, Susanne; Gilgen, Anna K; Kahmen, Ansgar; Buchmann, Nina

2015-01-01

244

The effect of drought and interspecific interactions on the depth of water uptake in deep- and shallow-rooting grassland species as determined by ?18O natural abundance  

NASA Astrophysics Data System (ADS)

Increased incidence of weather drought, as predicted under climate change, has the potential to negatively affect grassland production. Compared to monocultures, vertical belowground niche complementarity between shallow- and deep-rooting species may be an important mechanism resulting in higher yields and higher resistance to drought in grassland mixtures. However, very little is known about the belowground responses in grassland systems and increased insight into these processes may yield important information both to predict the effect of future climate change and better design agricultural systems to cope with this. This study assessed the effect of a 10-week experimental summer drought on the depth of water uptake of two shallow-rooting species (Lolium perenne L. and Trifolium repens L.) and two deep-rooting species (Chicorium intybus L. and Trifolium pratense L.) in grassland monocultures and four-species-mixtures by using the natural abundance ?18O isotope method. We tested the following hypotheses: (1) drought results in a shift of water uptake to deeper soil layers, (2) deep-rooting species take up a higher proportion of water from deeper soil layers relative to shallow-rooting species, (3) as a result of interspecific interactions in mixtures, the water uptake of shallow-rooting species become shallower when grown together with deep-rooting species and vice versa, resulting in reduced niche overlap. The natural abundance ?18O technique provided novel insights into the depth of water uptake of deep- and shallow- rooting grassland species and revealed large shifts in response to drought and interspecific interactions. Compared to control conditions, drought reduced the proportional water uptake from 0-10 cm soil depth (PCWU0-10) of L. perenne, T. repens and C. intybus in monocultures by on average 54%. In contrast, the PCWU0-10 of T. pratense in monoculture increased by 44%, and only when grown in mixture did the PCWU0-10 of T. pratense decrease under drought conditions. In line with hypothesis 2, in monoculture, the PCWU0-10 of shallow-rooting species L. perenne and T. repens was 0.53 averaged over the two drought treatments, compared to 0.16 for the deep-rooting C. intybus. Surprisingly, in monoculture, water uptake by T. pratense was shallower than for the shallow-rooting species (PCWU0-10 = 0.68). Interspecific interactions in mixtures resulted in a shift in the depth of water uptake by the different species. As hypothesised, the shallow-rooting species L. perenne and T. repens tended to become shallower, and the deep-rooting T. pratense made a dramatic shift to deeper soil layers (reduction in PCWU0-10 of 58% on average) in mixture compared to monoculture. However, these shifts did not result in a reduction in the proportional similarity of the proportional water uptake from different soil depth intervals (niche overlap) in mixtures compared to monocultures. There was no clear link between interspecific differences in depth of water uptake and drought resistance. C. intybus, the species with water uptake from the deepest soil layers was one of the species most affected by drought. However, T. pratense, the species with the highest plasticity in depth of water uptake, was least affected by drought, suggesting an indirect effect of rooting depth on drought resistance. Our results show that niche complementarity in the depth of water uptake between shallow- and deep-rooting species may have contributed to the diversity effect in mixtures.

Hoekstra, N. J.; Finn, J. A.; Lüscher, A.

2014-03-01

245

A Feasibility Study of Fricke Dosimetry as an Absorbed Dose to Water Standard for 192Ir HDR Sources  

PubMed Central

High dose rate brachytherapy (HDR) using 192Ir sources is well accepted as an important treatment option and thus requires an accurate dosimetry standard. However, a dosimetry standard for the direct measurement of the absolute dose to water for this particular source type is currently not available. An improved standard for the absorbed dose to water based on Fricke dosimetry of HDR 192Ir brachytherapy sources is presented in this study. The main goal of this paper is to demonstrate the potential usefulness of the Fricke dosimetry technique for the standardization of the quantity absorbed dose to water for 192Ir sources. A molded, double-walled, spherical vessel for water containing the Fricke solution was constructed based on the Fricke system. The authors measured the absorbed dose to water and compared it with the doses calculated using the AAPM TG-43 report. The overall combined uncertainty associated with the measurements using Fricke dosimetry was 1.4% for k?=?1, which is better than the uncertainties reported in previous studies. These results are promising; hence, the use of Fricke dosimetry to measure the absorbed dose to water as a standard for HDR 192Ir may be possible in the future. PMID:25521914

deAlmeida, Carlos Eduardo; Ochoa, Ricardo; de Lima, Marilene Coelho; David, Mariano Gazineu; Pires, Evandro Jesus; Peixoto, José Guilherme; Salata, Camila; Bernal, Mario Antônio

2014-01-01

246

Bathymetry of Lake Erie and Lake St. Clair Bathymetry is the science of measuring (soundings) and mapping (bathymetric maps) the depths of a water body (oceans, seas,  

E-print Network

) and mapping (bathymetric maps) the depths of a water body (oceans, seas, lakes) to delineate the topography of their basins. Bathymetric maps are two-dimensional representations of the 3-dimensional shape of these basins to the mid-1800s. However, no bathymetric maps approaching the full resolution allowed by these data were

247

Seasonal changes in depth of water uptake for encroaching trees Juniperus virginiana and Pinus ponderosa and two dominant C4 grasses in a semiarid grassland  

Microsoft Academic Search

Summary We used the natural abundance of stable isotopic ratios of hydrogen and oxygen in soil (0.05- 3 m depth), plant xylem and precipitation to determine the seasonal changes in sources of soil water uptake by two native encroaching woody species (Pinus ponderosa P. & C. Lawson, Juniperus virginiana L.), and two C4 grasses (Schizachyrium scoparium (Michx.) Nash, Panicum virgatum

KATHLEEN D. EGGEMEYER; TALA AWADA; F. EDWIN HARVEY; DAVID A. WEDIN; XINHUA ZHOU; C. WILLIAM ZANNER

2008-01-01

248

Draft Genome Sequence of Thalassotalea sp. Strain ND16A Isolated from Eastern Mediterranean Sea Water Collected from a Depth of 1,055 Meters.  

PubMed

Thalassotalea sp. strain ND16A belongs to the family Colwelliaceae and was isolated from eastern Mediterranean Sea water at a depth of 1,055 m. Members of Colwelliaceae are ubiquitous marine heterotrophs. Here, we report the draft genome sequence of Thalassotalea sp. strain ND16A, a member of the newly described genus Thalassotalea. PMID:25428976

Stelling, Savannah C; Techtmann, Stephen M; Utturkar, Sagar M; Alshibli, Noor K; Brown, Steven D; Hazen, Terry C

2014-01-01

249

The Incredible Shrinking Cup Lab: An Investigation of the Effect of Depth and Water Pressure on Polystyrene  

EPA Science Inventory

This activity familiarizes students with the effects of increased depth on pressure and volume. Students will determine the volume of polystyrene cups before and after they are submerged to differing depths in the ocean and the Laurentian Great Lakes. Students will also calculate...

250

Ventilatory mechanics and the effects of water depth on breathing pattern in the aquatic caecilian Typhlonectes natans.  

PubMed

The breathing pattern in the aquatic caecilian Typhlonectes natans was investigated by recording airflow via a pneumotachograph under unrestrained normal physiological conditions. Ventilatory mechanics were assessed using airflow and pressure measurements from the buccal cavity and trachea. The breathing pattern consisted of an expiratory phase followed by a series of 10-15 small buccal pumps to inflate the lung, succeeded by a long non-ventilatory period. T. natans separate the expiratory and inspiratory gases in the buccal cavity and take several inspiratory pumps, distinguishing their breathing pattern from that of sarcopterygians. Hydrostatic pressure assisted exhalation. The tracheal pressure was greater than the water pressure at that depth, suggesting that pleuroperitoneal pressure as well as axial or pulmonary smooth muscles may have contributed to the process of exhalation. The frequency of lung ventilation was 6.33+/-0.84 breaths h(-)(1), and ventilation occurred via the nares. Compared with other amphibians, this low ventilatory frequency suggests that T. natans may have acquired very efficient pulmonary respiration as an adaptation for survival in their seasonally fluctuating natural habitat. Their respiratory pathway is quite unique, with the trachea separated into anterior, central and posterior regions. The anterior region serves as an air channel, the central region is attached to the tracheal lung, and the posterior region consists of a bifurcated air channel leading to the left and right posterior lungs. The lungs are narrow, elongated, profusely vascularized and compartmentalized. The posterior lungs extend to approximately two-thirds of the body length. On the basis of their breathing pattern, it appears that caecilians are phylogenetically derived from two-stroke breathers. PMID:10607536

Prabha, K C; Bernard, D G; Gardner, M; Smatresk, N J

2000-01-01

251

Uncertainties in dose coefficients for intakes of tritiated water and organically bound forms of tritium by members of the public.  

PubMed

The International Commission on Radiological Protection (ICRP) provides models for the calculation of doses from intakes of radionuclides, including intakes of tritium as tritiated water (HTO) or organically bound tritium (OBT). The ICRP models for HTO and OBT are explained and the assumptions made are examined. The reliability of dose estimates is assessed in terms of uncertainties in central estimates for population groups. The models consider intakes of HTO and OBT by ingestion and inhalation by adults and children and doses to the fetus following intakes by the mother. The analysis includes uncertainties in the absorption of OBT to blood, incorporation of tritium into OBT in body tissues, retention times in tissues, transfer to the fetus and the relative biological effectiveness (RBE) of tritium beta emissions compared with gamma rays. Heterogeneity of dose within tissues and cells is also considered. For intakes as HTO, dose is predominantly due to distribution and retention of HTO in body water and it was concluded that adult doses are reliable to within a factor of 2. For intakes of OBT, the extent of incorporation into OBT in body tissues results in greater uncertainties with estimates relying on animal data for selected compounds. The analysis indicated that adult doses from OBT can be considered to be known to within a factor of 3. Greater uncertainties in estimated doses for children and for in utero exposures were considered. Central values from the uncertainty analyses of doses for HTO and OBT were greater than the corresponding ICRP dose coefficients by about a factor of 2, mainly due to the inclusion of uncertainties in RBE for tritium. A detailed assessment of doses using appropriate parameters and considering uncertainties would be of particular importance in situations where the dose may approach dose limits or constraints. For exposures to known forms of OBT, specific dose assessments may be required. PMID:12018747

Harrison, J D; Khursheed, A; Lambert, B E

2002-01-01

252

Temperature, water availability, and nutrient levels at various soil depths-consequences for shallow-rooted desert succulents, including nurse plant effects. [Agave deserti; Ferocactus acanthodes; hilaria rigida  

SciTech Connect

Soil conditions were evaluated over the rooting depths for Agave deserti and Ferocactus acanthodes from the northwestern Sonoran Desert. These succulents have mean root depths of only 10 cm when adults and even shallower distribution when seedlings, which often occur is association with the nurse plant Hilaria rigida, which also has shallow roots. Maximum soil temperatures in the 2 cm beneath bare ground were predicted to exceed 65 C, which is lethal to the roots of A. deserti and F. acanthodes, whereas H. rigida reduced the maximum surface temperatures by over 10 C, providing a microhabitat suitable for seedling establishment. Water Availability was defined as the soil-to-plant drop in water potential, for periods when the plants could take up water, integrated over time. Below 4 cm under bare ground, simulated Water Availability increased slightly with depth (to 35 cm) for a wet year, was fairly constant for an average year, and decreased for a dry year, indicating that the shallow rooting habit is more advantageous in drier years. Water uptake by H. rigida substantially reduced Water Availability for seedlings associated with this nurse plant. On the other hand, a 66-90% higher soil nitrogen level occurred under H. rigida, possibly representing its harvesting of this macronutrient from a wide ground area. Phosphorus was slightly less abundant in the soil under H. rigida compared with under bare ground, the potassium level was substantially higher, and the sodium level was substantially lower. All four elements varied greatly with depth, N and K decreasing and P and Na increasing. Based on the known growth responses of A. deserti and F. acanthodes to these four elements, growth was predicted to be higher for plants in soil from the shallower layers, most of the differences being due to nitrogen.

Nobel, P.S. (Univ. of California, Los Angeles (USA))

1989-10-01

253

Radon and radium concentration in water from North-West of Romania and the estimated doses.  

PubMed

In the present study, the measurements of radon were carried out using the LUK-VR system based on radon gas measurements with Lucas cells. The radium concentration in water was determined, with the same device, immediately after was established the radon equilibrium with radium. The results presented here are from a survey carried out in the N-W region of Transylvania (Romania) in which were investigated the radon concentrations in natural (spring, well and surface) and drinking (tap) waters. The results showed radon concentrations within the range of 0.4-187.3 Bq l(-1) with an average value of 15.9 Bq l(-1) whereas radium concentration varied between 0.05 and 0.825 Bq l(-1) with an average value of 0.087 Bq l(-1) for all types of water covered within this survey. The corresponding annual effective ingestion dose due to radon and radium from water was determined from drinking water used by the population inhabiting the area. PMID:25031036

Moldovan, M; Benea, V; Ni??, D C; Papp, B; Burghele, B D; Bican-Bri?an, N; Cosma, C

2014-11-01

254

Dose to ‘water-like’ media or dose to tissue in MV photons radiotherapy treatment planning: still a matter of debate  

NASA Astrophysics Data System (ADS)

The difference between Monte Carlo Treatment Planning (MCTP) based on the assumption of ‘water-like’ tissues with densities obtained from CT procedures, or on tissue compositions derived from CT-determined densities, have been investigated. Stopping powers and electron fluences have been calculated for a range of media and body tissues for 6 MV photon beams, including changes in their physical data (density and stopping powers). These quantities have been used to determine absorbed doses using cavity theory. It is emphasized that tissue compositions given in ICRU or ICRP reports should not be given the standing of physical constants as they correspond to average values obtained for a limited number of human-body samples. It has been shown that mass stopping-power ratios to water are more dependent on patient-to-patient composition differences, and therefore on their mean excitation energies (I-values), than on mass density. Electron fluence in different media are also more dependent on media composition (and their I-values) than on density. However, as a consequence of the balance between fluence and stopping powers, doses calculated from their product are more constant than what the independent stopping powers and fluence variations suggest. Additionally, cancelations in dose ratios minimize the differences between the ‘water-like’ and ‘tissue’ approaches, yielding practically identical results except for bone, and to a lesser extent for adipose tissue. A priori, changing from one approach to another does not seem to be justified considering the large number of approximations and uncertainties involved throughout the treatment planning tissue segmentation and dose calculation procedures. The key issue continues to be the composition of tissues and their I-values, and as these cannot be obtained for individual patients, whatever approach is selected does not lead to significant differences from a water reference dose, the maximum of these being of the order of 5% for bone tissues. Considering, however, current developments in advanced dose calculation methods, planning in terms of dose-to-tissue should be the preferred choice, under the expectancy that progress in the field will gradually improve some of the crude approximations included in MCTP and numerical transport methods. The small differences obtained also show that a retrospective conversion from dose-to-tissue to dose-to-water, based on a widely used approach, would mostly increase the final uncertainty of the treatment planning process. It is demonstrated that, due to the difference between electron fluence distributions in water and in body tissues, the conversion requires an additional fluence correction that has so far been neglected. An improved expression for the conversion and data for the fluence correction factor are provided. These will be necessary even in a dose-to-tissue environment, for the normalization of the treatment plan to the reference dosimetry of the treatment unit, always calibrated in terms of absorbed dose to water.

Andreo, Pedro

2015-01-01

255

Dose to 'water-like' media or dose to tissue in MV photons radiotherapy treatment planning: still a matter of debate.  

PubMed

The difference between Monte Carlo Treatment Planning (MCTP) based on the assumption of 'water-like' tissues with densities obtained from CT procedures, or on tissue compositions derived from CT-determined densities, have been investigated. Stopping powers and electron fluences have been calculated for a range of media and body tissues for 6 MV photon beams, including changes in their physical data (density and stopping powers). These quantities have been used to determine absorbed doses using cavity theory. It is emphasized that tissue compositions given in ICRU or ICRP reports should not be given the standing of physical constants as they correspond to average values obtained for a limited number of human-body samples.It has been shown that mass stopping-power ratios to water are more dependent on patient-to-patient composition differences, and therefore on their mean excitation energies (I-values), than on mass density. Electron fluence in different media are also more dependent on media composition (and their I-values) than on density. However, as a consequence of the balance between fluence and stopping powers, doses calculated from their product are more constant than what the independent stopping powers and fluence variations suggest.Additionally, cancelations in dose ratios minimize the differences between the 'water-like' and 'tissue' approaches, yielding practically identical results except for bone, and to a lesser extent for adipose tissue. A priori, changing from one approach to another does not seem to be justified considering the large number of approximations and uncertainties involved throughout the treatment planning tissue segmentation and dose calculation procedures. The key issue continues to be the composition of tissues and their I-values, and as these cannot be obtained for individual patients, whatever approach is selected does not lead to significant differences from a water reference dose, the maximum of these being of the order of 5% for bone tissues. Considering, however, current developments in advanced dose calculation methods, planning in terms of dose-to-tissue should be the preferred choice, under the expectancy that progress in the field will gradually improve some of the crude approximations included in MCTP and numerical transport methods.The small differences obtained also show that a retrospective conversion from dose-to-tissue to dose-to-water, based on a widely used approach, would mostly increase the final uncertainty of the treatment planning process. It is demonstrated that, due to the difference between electron fluence distributions in water and in body tissues, the conversion requires an additional fluence correction that has so far been neglected. An improved expression for the conversion and data for the fluence correction factor are provided. These will be necessary even in a dose-to-tissue environment, for the normalization of the treatment plan to the reference dosimetry of the treatment unit, always calibrated in terms of absorbed dose to water. PMID:25503312

Andreo, Pedro

2015-01-01

256

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

PubMed

The radial depth-dose distribution of a prototype 188W/188Re beta 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 > or = 99% of the dose between 1 mm and 5 mm radial distance from the source axis. The TLDs were calibrated using a 90Sr/90Y beta secondary standard. Several correction factors are calculated using analytical and Monte Carlo methods. An analysis of the measurement uncertainty is made. Since it is partly determined by components of uncertainty arising from random effects, repeated measurements yield a lower uncertainty. The expanded uncertainty in the absolute dose at 2 mm radial distance equals 11%, 10%, 9% and 8% for 1, 2, 3 and 5 measurements, respectively. After a correction for source non-uniformity, the measured dose rate per unit source activity at 2 mm radial distance equals (1.53 +/- 0.16) Gy min(-1) GBq(-1) (2sigma), in agreement with the value of (1.45 +/- 0.01) Gy min(-1) GBq(-1) (2sigma) predicted by the MCNP4C simulations. PMID:12433123

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

2002-10-21

257

Response of vegetation and carbon accumulation to changes in precipitation and water table depths in two bogs during the Holocene: a modelling exercise  

NASA Astrophysics Data System (ADS)

To assess the influence of hydrological changes on northern peatland ecosystems, we analysed the response of the Holocene Peat Model (HPM, Frolking et al. 2010), designed to simulate peatland development at millennial timescale, to two hydrological settings, based on precipitation and water table depths reconstructions. The studied sites are two open ombrotrophic peatlands located in the James Bay Lowlands in Northeastern Canada. For both sites, two simulations were realised: one based on a precipitation reconstruction from pollen data, used as input in the model, and a second using a water table depth reconstruction derived from testate amoebae to apply a water table forcing on the model. Simulated variations in carbon accumulation rates (CAR) and vegetation composition were analysed against the palaeoecological datasets. Results in CAR in both sites and hydrological settings showed periods of net carbon loss, which coincided with fluctuations in observed CAR, though they cannot be traced in palaeoecological datasets. The comparison between plant macrofossils records and simulated vegetation distributions highlighted differences between precipitation and water table depth driven simulations that can be used to distinguish the origin of vegetation shifts. The methodology used could thus be useful in paleoecological studies when two or more proxies are available.

Quillet, A.; Garneau, M.; van Bellen, S.; Frolking, S. E.; Tuittila, E.

2013-12-01

258

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

PubMed Central

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

2012-01-01

259

The IPEM code of practice for electron dosimetry for radiotherapy beams of initial energy from 4 to 25 MeV based on an absorbed dose to water calibration  

NASA Astrophysics Data System (ADS)

This report contains the recommendations of the Electron Dosimetry Working Party of the UK Institute of Physics and Engineering in Medicine (IPEM). The recommendations consist of a code of practice for electron dosimetry for radiotherapy beams of initial energy from 4 to 25 MeV. The code is based on the absorbed dose to water calibration service for electron beams provided by the UK standards laboratory, the National Physical Laboratory (NPL). This supplies direct ND,w calibration factors, traceable to a calorimetric primary standard, at specified reference depths over a range of electron energies up to approximately 20 MeV. Electron beam quality is specified in terms of R50,D, the depth in water along the beam central axis at which the dose is 50% of the maximum. The reference depth for any given beam at the NPL for chamber calibration and also for measurements for calibration of clinical beams is 0.6R50,D - 0.1 cm in water. Designated chambers are graphite-walled Farmer-type cylindrical chambers and the NACP- and Roos-type parallel-plate chambers. The practical code provides methods to determine the absorbed dose to water under reference conditions and also guidance on methods to transfer this dose to non-reference points and to other irradiation conditions. It also gives procedures and data for extending up to higher energies above the range where direct calibration factors are currently available. The practical procedures are supplemented by comprehensive appendices giving discussion of the background to the formalism and the sources and values of any data required. The electron dosimetry code improves consistency with the similar UK approach to megavoltage photon dosimetry, in use since 1990. It provides reduced uncertainties, approaching 1% standard uncertainty in optimal conditions, and a simpler formalism than previous air kerma calibration based recommendations for electron dosimetry.

Thwaites (Chair), IPEM Working Party: D. I.; Du Sautoy, A. R.; Jordan, T.; McEwen, M. R.; Nisbet, A.; Nahum, A. E.; Pitchford, W. G.

2003-09-01

260

Using stable isotopes to characterize differential depth of water uptake based on environmental conditions in perennial biofuel and traditional annual crops  

NASA Astrophysics Data System (ADS)

Global climate change related to fossil fuel consumption coupled with the necessity for secure, cost-effective, and renewable domestic energy is continuing to drive the development of a bioenergy industry. Numerous second-generation biofuel crops have been identified that hold promise as sustainable feedstocks for the industry, including perennial grasses that utilize the highly water and energy efficient C4 photosynthetic pathway. Among the perennial grasses, miscanthus (Miscanthus × giganteus) and switchgrass (Panicum virgatum) stand out as having high biomass, minimal maintenance, low nutrient input requirements, and positive environmental benefits. These grasses are able to withstand a wide range of growing season temperatures and precipitation regimes, particularly in reference to the annual row crops that they are likely to replace. During the drought of 2012 traditional row crops suffered major reductions in yield whereas the perennial grasses retained relatively high biomass yields. We hypothesize that this is due to the ability of the perennial grasses to access water from deeper soil water relative to the annual row crops. To test this hypothesis, we use isotopic techniques to determine the soil depth from which the various species obtain water. Data from summer 2013 suggests that the perennial grasses preferentially use surface water when available but can extract water from depths that the annual row crops are unable to reach. These results indicate that perennial grasses, with deeper roots, will likely sustain growth under conditions when annual row crops are unable.

Miller, J. N.; Nystrom, R.; Bernacchi, C.

2013-12-01

261

Apparent Depth.  

ERIC Educational Resources Information Center

Discusses a well-known optical refraction problem where the depth of an object in a liquid is determined. Proposes that many texts incorrectly solve the problem. Provides theory, equations, and diagrams. (MVL)

Nassar, Antonio B.

1994-01-01

262

Modeling water flow, depth and inundation extent over the rivers of the Contiguous US within a Catchment-based Land Surface Modeling Framework  

NASA Astrophysics Data System (ADS)

With population growth and increasing demand of water supply, the need for integrated continental and global scale surface water dynamics simulation systems relying on both observations and models is ever increasing. In this study we characterize how accurately we can estimate river discharge, river depth and the corresponding inundation extent over the contiguous U.S. by combining observations and models. We present a continental-scale implementation of the Catchment-based Hydrological And Routing Modeling System (CHARMS) that includes an explicit representation of the river networks from a Geographic Information System (GIS) dataset. The river networks and contributing catchment boundaries of the Contiguous U.S are upscaled from the NHDPlus dataset. The average upscaled catchment size is 2773 km2 and the unique main river channel contained in each catchment consists of several river reaches of average length 1.6 km. We derive 18 sets of empirical relationship between channel dimension (bankfull depth and bankfull width) and drainage area based on USGS gauge observations to describe river dynamics for the 18 water resource regions of the NHDPlus representation of the United States. These relationships are used to separate the main river channel and floodplain. Modeled monthly and daily streamflow show reasonable agreement with gauge observations and initial results show that basins with fewer anthropogenic modifications are more accurately simulated. Modeled monthly and daily river depth and floodplain extent associated with each river reach are also explicitly estimated over the U.S., although such simulations are more challenging to validate. Our results have implications for capturing the seasonal-to-interannual dynamics of surface water in climate models. Such a continental-scale modeling framework development would, by design, facilitate the use of existing in situ observations and be suitable for integrating the upcoming NASA Surface Water and Ocean Topography (SWOT) mission measurements for a range of studies in climate, hydrology and water management.

Liu, Z.; David, C. H.; Famiglietti, J. S.

2013-12-01

263

Relations among water levels, specific conductance, and depths of bedrock fractures in four road-salt-contaminated wells in Maine, 2007–9  

USGS Publications Warehouse

Data on groundwater-level, specific conductance (a surrogate for chloride), and temperature were collected continuously from 2007 through 2009 at four bedrock wells known to be affected by road salts in an effort to determine the effects of road salting and fractures in bedrock that intersect the well at a depth below the casing on the presence of chloride in groundwater. Dissolved-oxygen data collected periodically also were used to make inferences about the interaction of fractures and groundwater flow. Borehole geophysical tools were used to determine the depths of fractures in each well that were actively contributing flow to the well, under both static and pumped conditions; sample- and measurement-depths were selected to correspond to the depths of these active fractures. Samples of water from the wells, collected at depths corresponding to active bedrock fractures, were analyzed for chloride concentration and specific conductance; from these analyses, a linear relation between chloride concentration and specific conductance was established, and continuous and periodic measurements of specific conductance were assumed to represent chloride concentration of the well water at the depth of measurement. To varying degrees, specific conductance increased in at least two of the wells during winter and spring thaws; the shallowest well, which also was closest to the road receiving salt treatment during the winter, exhibited the largest changes in specific conductance during thaws. Recharge events during summer months, long after application of road salt had ceased for the year, also produced increases in specific conductance in some of the wells, indicating that chloride which had accumulated or sequestered in the overburden was transported to the wells throughout the year. Geophysical data and periodic profiles of water quality along the length of each well’s borehole indicated that the greatest changes in water quality were associated with active fractures; in one case, high concentration of dissolved oxygen at the bottom of the well indicated the presence of a highly transmissive fracture that was in good connection with a surficial feature (stream or atmosphere). Data indicated that fractures have a substantial influence on the transport of chlorides to the subsurface; that elevated specific conductance occurred throughout the year, not just when road salts were applied; and that chloride contamination, as indicated by elevated specific conductance, may persist for years.

Schalk, Charles W.; Stasulis, Nicholas W.

2012-01-01

264

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

2007-01-01

265

Experience in Wales (UK) of the optimisation of ortho-phosphate dosing for controlling lead in drinking water.  

PubMed

Dwr Cymru Welsh Water supplies over three million people with drinking water throughout most of Wales (UK). Ortho-phosphate has increasingly been dosed at around 1 mg/L (P) to further reduce the corrosivity of supplies to the lead pipes which connect approximately 30% of houses to water mains in the company's area, additional to long-establish pH adjustment measures. The installation of new ortho-phosphate dosing schemes and the optimisation of these and existing dosing schemes, 29 schemes in total, were subject to a regulatory programme of work, agreed with the Drinking Water Inspectorate (DWI). Optimisation comprised (i) selection of appropriate ortho-phosphate doses by a procedure involving laboratory based plumbosolvency testing linked to zonal lead emission (compliance) modelling, (ii) tight dose control and (iii) extensive monitoring of lead in supply by random daytime (RDT) sampling and by the use of lead pipe test rigs. The successful outcome was confirmed by 99% of over 5,000 RDT samples complying with the future standard of 10 microg/L for lead in drinking water. PMID:18209280

Hayes, C R; Incledion, S; Balch, M

2008-06-01

266

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

USGS Publications Warehouse

A depth to basement map of the Death Valley groundwater model area was prepared using over 40,0000 gravity stations as part of an interagency effort by the U.S. Geological Survey and the U.S. Department of Energy to help characterize the geology and hydrology of southwest Nevada and parts of California.

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

2001-01-01

267

Dosimetric validation of the Acuros XB Advanced Dose Calculation algorithm: fundamental characterization in water  

NASA Astrophysics Data System (ADS)

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.

Fogliata, Antonella; Nicolini, Giorgia; Clivio, Alessandro; Vanetti, Eugenio; Mancosu, Pietro; Cozzi, Luca

2011-03-01

268

Hydrologic Record Extension of Water-Level Data in the Everglades Depth Estimation Network (EDEN) Using Artificial Neural Network Models, 2000-2006  

USGS Publications Warehouse

The Everglades Depth Estimation Network (EDEN) is an integrated network of real-time water-level gaging stations, ground-elevation models, and water-surface models designed to provide scientists, engineers, and water-resource managers with current (2000-present) water-depth information for the entire freshwater portion of the greater Everglades. The U.S. Geological Survey Greater Everglades Priority Ecosystem Science provides support for EDEN and the goal of providing quality assured monitoring data for the U.S. Army Corps of Engineers Comprehensive Everglades Restoration Plan. To increase the accuracy of the water-surface models, 25 real-time water-level gaging stations were added to the network of 253 established water-level gaging stations. To incorporate the data from the newly added stations to the 7-year EDEN database in the greater Everglades, the short-term water-level records (generally less than 1 year) needed to be simulated back in time (hindcasted) to be concurrent with data from the established gaging stations in the database. A three-step modeling approach using artificial neural network models was used to estimate the water levels at the new stations. The artificial neural network models used static variables that represent the gaging station location and percent vegetation in addition to dynamic variables that represent water-level data from the established EDEN gaging stations. The final step of the modeling approach was to simulate the computed error of the initial estimate to increase the accuracy of the final water-level estimate. The three-step modeling approach for estimating water levels at the new EDEN gaging stations produced satisfactory results. The coefficients of determination (R2) for 21 of the 25 estimates were greater than 0.95, and all of the estimates (25 of 25) were greater than 0.82. The model estimates showed good agreement with the measured data. For some new EDEN stations with limited measured data, the record extension (hindcasts) included periods beyond the range of the data used to train the artificial neural network models. The comparison of the hindcasts with long-term water-level data proximal to the new EDEN gaging stations indicated that the water-level estimates were reasonable. The percent model error (root mean square error divided by the range of the measured data) was less than 6 percent, and for the majority of stations (20 of 25), the percent model error was less than 1 percent.

Conrads, Paul A.; Roehl, Edwin A., Jr.

2007-01-01

269

Relative biological effectiveness and dose rate effect of tritiated water on chromosomes in human lymphocytes and bone marrow cells.  

PubMed

Tritiated water (HTO) is a major toxic effluent from the nuclear power industry, that is released into the environment in large quantities. The low dose radiation effect and dose rate effect of HTO on human lymphocytes and bone marrow cells have not been well studied. The present study was therefore undertaken to investigate the HTO dose-response relationship for chromosomal aberrations in human lymphocytes and bone marrow cells at low in vitro radiation doses ranging from 0.1 to 1 Gy. Lymphocytes (G0 stage) and bone marrow cells were incubated for 10-150 min with HTO at a dose rate of 2 cGy/min (555 MBq/ml). The relative biological effectiveness (RBE) of HTO was calculated with respect to 60Co gamma-rays for the induction of dicentric and centric ring chromosomes at low radiation doses. The RBE value for HTO beta-rays relative to 60Co gamma-rays was 2.7 for lymphocytes and 3.1 for chromatid aberrations in bone marrow cells. Lymphocytes were also chronically exposed to HTO for 6.7-80 h at dose rates of 0.5 cGy/min (138.5 MBq/ml) and 0.02 cGy/min (5.6 MBq/ml). There was a 71.5% decrease in the yield of dicentrics and centric rings at the dose rate of 0.02 cGy/min, indicating a clear dose rate effect of HTO. The RBE value for HTO relative to 137Cs gamma-rays was 2.0 at a dose rate of 0.02 cGy/min, suggesting that low HTO dose rates produce no increase of the RBE values and that the values may be constant between 2 and 3 within these dose rates. These results should prove useful in assessment of the health risk for humans exposed to low levels of HTO. PMID:7508567

Tanaka, K; Sawada, S; Kamada, N

1994-01-01

270

[The depth distribution of neutron-capture events in 10B nuclei during the irradiation of a water phantom with neutrons from the channels of the BR-10 reactor].  

PubMed

The authors present the results of experimental investigations of distribution of capture events on nuclei 10B by the depth of a water phantom during its irradiation with beams T-4 and B-3 of the BR-10 reactor. A ferrous sulfate dosimeter with added boric acid was used as a detector of such events. The depth of a water phantom on which the effect of boron capture by a neutron beam is decreased 2-fold, is 1.7 cm. For the B-3 beam a curve of depth correlation of neutron capture events had a broad maximum at a depth of 4-5 cm. PMID:1890942

Kapchigashev, S P; Potetnia, V I; Khodyreva, E V; Neshina, V S

1991-01-01

271

Microborer ichnocoenoses in Quaternary corals from New Caledonia: reconstructions of paleo-water depths and reef growth strategies in relation to environmental changes  

NASA Astrophysics Data System (ADS)

Coral reef growth and development depend on several environmental factors, including tectonic and climatic parameters and local ecological drivers. Reef growth is especially sensitive to sea-level variations. Paleo-water depth reconstructions are essential tools used to determine reef growth patterns during different periods of reef growth. Assemblages of corals and/or coralline algae have been commonly used in such paleodepth reconstructions. This study shows that using microendolith ichnocoenoses can sometimes provide better accuracy than traditional coralgal analyses, particularly in the depth-range 0-10 m where coralgal assemblages usually show broad distribution ranges. Holocene and Pleistocene cores from two barrier reef sites on the west coast of Grande Terre in New Caledonia are examined here. Holocene reef development at these sites feature examples of microendolith ichnocoenoses that document rapid environmental changes and small sea-level variations of about 2-5 m in amplitude, and record these changes with more accuracy than coral and coralline algae assemblages which are highly dependant on the hydrodynamic energy of the setting. During the Pleistocene, which was less chronologically constrained, the microendolith ichnocoenoses also reflect paleo-water depths and reef-growth patterns at different periods of reef history.

Rémy, Richet; Véronique, Chazottes; Guy, Cabioch; Norbert, Frank; Burr George, S.

2011-09-01

272

Depth Profiling of Water Molecules at the Liquid-Liquid Interface Using a Combined Surface Vibrational Spectroscopy  

E-print Network

tetrachloride-water (CCl4-H2O) and 1,2-dichloroethane-water (DCE- H2O). In particular, molecular dynamics simulations are performed to generate computational spectral intensities of the CCl4-H2O and DCE-H2O

Richmond, Geraldine L.

273

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

274

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

275

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

2013-09-01

276

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

USGS Publications Warehouse

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 (~2m 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

277

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. PMID:22592821

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

2012-01-01

278

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

2012-10-01

279

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

E-print Network

Stability of gravity-capillary waves generated by a moving pressure disturbance in water of finite In previous work, we investigated two-dimensional steady gravity-capillary waves generated by a localized when wave with gravity

280

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

281

Modeling of depth to base of Last Glacial Maximum and seafloor sediment thickness for the California State Waters Map Series, eastern Santa Barbara Channel, California  

USGS Publications Warehouse

Models of the depth to the base of Last Glacial Maximum and sediment thickness over the base of Last Glacial Maximum for the eastern Santa Barbara Channel are a key part of the maps of shallow subsurface geology and structure for offshore Refugio to Hueneme Canyon, California, in the California State Waters Map Series. A satisfactory interpolation of the two datasets that accounted for regional geologic structure was developed using geographic information systems modeling and graphics software tools. Regional sediment volumes were determined from the model. Source data files suitable for geographic information systems mapping applications are provided.

Wong, Florence L.; Phillips, Eleyne L.; Johnson, Samuel Y.; Sliter, Ray W.

2012-01-01

282

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

283

GENE EXPRESSION DOSE-RESPONSE IN THE BLADDERS OF MICE EXPOSED TO ARSENIC IN DRINKING WATER FOR 13 WEEKS  

EPA Science Inventory

The association between drinking water exposures to inorganic arsenic and life-threatening tumors in the human is strongest for bladder cancer. To investigate the mode of action for inorganic arsenic carcinogenicity in the bladder, a study was conducted to characterize the dose-r...

284

Using LiF:Mg,Cu,P TLDs to estimate the absorbed dose to water in liquid water around an {sup 192}Ir brachytherapy source  

SciTech Connect

Purpose: The absorbed dose to water is the fundamental reference quantity for brachytherapy treatment planning systems and thermoluminescence dosimeters (TLDs) have been recognized as the most validated detectors for measurement of such a dosimetric descriptor. The detector response in a wide energy spectrum as that of an{sup 192}Ir brachytherapy source as well as the specific measurement medium which surrounds the TLD need to be accounted for when estimating the absorbed dose. This paper develops a methodology based on highly sensitive LiF:Mg,Cu,P TLDs to directly estimate the absorbed dose to water in liquid water around a high dose rate {sup 192}Ir brachytherapy source. Methods: Different experimental designs in liquid water and air were constructed to study the response of LiF:Mg,Cu,P TLDs when irradiated in several standard photon beams of the LNE-LNHB (French national metrology laboratory for ionizing radiation). Measurement strategies and Monte Carlo techniques were developed to calibrate the LiF:Mg,Cu,P detectors in the energy interval characteristic of that found when TLDs are immersed in water around an{sup 192}Ir source. Finally, an experimental system was designed to irradiate TLDs at different angles between 1 and 11 cm away from an {sup 192}Ir source in liquid water. Monte Carlo simulations were performed to correct measured results to provide estimates of the absorbed dose to water in water around the {sup 192}Ir source. Results: The dose response dependence of LiF:Mg,Cu,P TLDs with the linear energy transfer of secondary electrons followed the same variations as those of published results. The calibration strategy which used TLDs in air exposed to a standard N-250 ISO x-ray beam and TLDs in water irradiated with a standard{sup 137}Cs beam provided an estimated mean uncertainty of 2.8% (k = 1) in the TLD calibration coefficient for irradiations by the {sup 192}Ir source in water. The 3D TLD measurements performed in liquid water were obtained with a maximum uncertainty of 11% (k = 1) found at 1 cm from the source. Radial dose values in water were compared against published results of the American Association of Physicists in Medicine and the European Society for Radiotherapy and Oncology and no significant differences (maximum value of 3.1%) were found within uncertainties except for one position at 9 cm (5.8%). At this location the background contribution relative to the TLD signal is relatively small and an unexpected experimental fluctuation in the background estimate may have caused such a large discrepancy. Conclusions: This paper shows that reliable measurements with TLDs in complex energy spectra require a study of the detector dose response with the radiation quality and specific calibration methodologies which model accurately the experimental conditions where the detectors will be used. The authors have developed and studied a method with highly sensitive TLDs and contributed to its validation by comparison with results from the literature. This methodology can be used to provide direct estimates of the absorbed dose rate in water for irradiations with HDR{sup 192}Ir brachytherapy sources.

Lucas, P. Avilés, E-mail: paz.aviles@ciemat.es; Aubineau-Laničce, I.; Lourenço, V.; Vermesse, D.; Cutarella, D. [CEA, LIST, Laboratoire National Henri Becquerel, 91191 Gif-sur-Yvette (France)] [CEA, LIST, Laboratoire National Henri Becquerel, 91191 Gif-sur-Yvette (France)

2014-01-15

285

Interannual to decadal oxygen variability in the mid-depth water masses of the eastern North Atlantic  

NASA Astrophysics Data System (ADS)

The detection of multi-decadal trends in the oceanic oxygen content and its possible attribution to global warming is protracted by the presence of a substantial amount of interannual to decadal variability, which hitherto is poorly known and characterized. Here we address this gap by studying interannual to decadal changes of the oxygen concentration in the Subpolar Mode Water (SPMW), the Intermediate Water (IW) and the Mediterranean Outflow Water (MOW) in the eastern North Atlantic. We use data from a hydrographic section located in the eastern North Atlantic at about 48°N repeated 12 times over a period of 19 years from 1993 through 2011, with a nearly annual resolution up to 2005. Despite a substantial amount of year-to-year variability, we observe a long-term decrease in the oxygen concentration of all three water masses, with the largest changes occurring from 1993 to 2002. During that time period, the trends were mainly caused by a contraction of the subpolar gyre associated with a northwestward shift of the Subpolar Front (SPF) in the eastern North Atlantic. This caused SPMW to be ventilated at lighter densities and its original density range being invaded by subtropical waters with substantially lower oxygen concentrations. The contraction of the subpolar gyre reduced also the penetration of IW of subpolar origin into the region in favor of an increased northward transport of IW of subtropical origin, which is also lower in oxygen. The long-term oxygen changes in the MOW were mainly affected by the interplay between circulation and solubility changes. Besides the long-term signals, mesoscale variability leaves a substantial imprint as well, affecting the water column over at least the upper 1000 m and laterally by more than 400 km. Mesoscale eddies induced changes in the oxygen concentration of a magnitude that can substantially alias analyses of long-term changes based on repeat hydrographic data that are being collected at intervals of typically 10 years.

Stendardo, Ilaria; Kieke, Dagmar; Rhein, Monika; Gruber, Nicolas; Steinfeldt, Reiner

2015-01-01

286

Does deposition depth control the OSL bleaching of fluvial sediment?  

NASA Astrophysics Data System (ADS)

The Optically Stimulated Luminescence (OSL) signal from fluvial sediment often contains a remnant from the previous deposition cycle, leading to a partially bleached equivalent-dose distribution. Although identification of the burial dose is of primary concern, the degree of bleaching could potentially provide insights into geomorphic processes. However, comparison of bleaching between samples is complicated by sample-to-sample variation in aliquot size and luminescence sensitivity. Here we develop an age model to account for these effects. With measurement data from multi-grain aliquots, we use Bayesian computational statistics to estimate the burial dose and bleaching parameters of the single-grain dose distribution. We apply the model to 46 samples taken from fluvial sediment of Rhine branches in the Netherlands, and compare the results with environmental predictor variables (depositional energy and environment, sample depth, depth relative to mean water level, dose rate). We find no significant correlations between any predictor variable and the bleaching parameters, although large uncertainties may be obscuring relationships. However, the best bleached samples are found close to the mean water level. Based on these results, we hypothesize that bleaching occurs mainly during fluvial transport rather than upon deposition, with extra bleaching possible for sediments near the transition of channel to overbank deposits due to local reworking after deposition either by wind or water.

Cunningham, A. C.; Wallinga, J.; Hobo, N.; Versendaal, A. J.; Makaske, B.; Middelkoop, H.

2014-07-01

287

Dose evaluation and measurement of radon concentration in some drinking water sources of the Ramsar region in Iran.  

PubMed

Ramsar is one of the highest background radiation areas in the world, whose natural radioactivity is due to (238)U natural series and its decay products, especially (226)Ra and (220)Rn, which have been brought to the surface by water of hot springs. In this study, radon concentration in 14 drinking water sources of the Ramsar region has been measured with the PRASSI system. The results show all of the water supplies have radon concentration greater than 10kBq/m(3) as normal level. Moreover, the estimated mean annual radiation dose to public due to waterborne radon has also been evaluated. PMID:20183237

Mowlavi, Ali Asghar; Shahbahrami, Amrolah; Binesh, Alireza

2009-09-01

288

Simultaneous determination of shallow water-table depths and EM wave velocities using multiple-offset GPR profiling data in peatland  

NASA Astrophysics Data System (ADS)

Bibai bog in Hokkaido is the only high moor peatland left in the Ishikari peatlands (60,000ha). Almost all bogs except Bibai bog have been reclaimed for farmlands, housing lands, etc. in last century. The total area of Bibai bog is now about 50 ha. The remaining bog is suffering from drying and ground subsidence by the drainage of water. To propose an appropriate management for Bibai bog preservation, deep understanding of the temporal and spatial behaviors of water table is necessary. To obtain water-table depths along a survey line, we used ground-penetrating radar (GPR). In many applications, GPR data are collected with the common-offset profiling (CO), in which the separation distance between a transmitter and a receiver is constant. However, it gives only travel time of reflected EM waves from an unknown reflector. To calculate the velocity of the EM wave, the common-midpoint (CMP) method, a multi- offset acquisition method, is also used. In this study, we collected CO profiling data with different antenna separations along a common survey line in Bibai bog. This approach allows us to directly estimate the EM wave velocity at all measurement locations without performing a common multi-offset acquisition method, such as the CMP method. In this survey, 7 CO data with 7 different antenna separations varying from 60 cm to 120 cm were collected along survey lines in and around the bog. As a result, we could calculate the average EM wave velocity and gain the velocity distribution every 5 cm along the survey lines. In addition, we could determine the shallow water-table depths directly by using multiple offset GPR profiling data.

Saito, H.; Matsushima, S.; Asada, K.; Kawamoto, K.; Komatsu, T.

2009-05-01

289

Depth of penetration of bubbles entrained by a plunging water jet Christophe Clanet and Juan C. Lasheras  

E-print Network

, where g is the acceleration due to gravity, is the liquid density and is the surface tension of water through a regulator and a flowmeter. All nozzles consisted of stainless steel needles with length was measured experimen- tally applying an edge finding filter to the average image resulting from 125 video

Clanet, Christophe

290

Responses of saltcedar ( Tamarix chinensis ) to water table depth and soil salinity in the Yellow River Delta, China  

Microsoft Academic Search

Significant studies about Tamarix chinensis as an introduced invasive plant species have been implemented in North America. However, the response of native T. chinensis to its environment is not well known in China. T. chinensis is a useful species in preventing sea water intrusion in coastal areas of northern China. It is necessary to fully understand\\u000a the relationships between environmental

Baoshan Cui; Qichun Yang; Kejiang Zhang; Xinsheng Zhao; Zheyuan You

2010-01-01

291

Anatomy of T Phases Recorded by An OBS at 5 km Water Depth: Effects of Local Bathymetry and SOFAR Channel Heterogeneity  

NASA Astrophysics Data System (ADS)

We have deployed broadband ocean bottom seismometers (OBSs) offshore eastern Taiwan in 2006 and 2007. One OBS at 5 km water depth has routinely recorded abnormal seismic phase after P and S phases. The attributes of the energy, including frequency band and arrival time, are consistent with that of a T wave. T waves are phases contained at least some acoustic paths through water bodies. It is still not clear how the T phase energy leaks out of the SOFAR channel before being recorded at depth. From regional physical oceanographic data we found heterogeneous SOFAR channel near the OBS site. Thus, some of the energy can be scattered out of the waveguide. We used an earthquake near the coast to calculate the traveltimes through different solid-earth to acoustic conversion points along the regional 1000 meter bathymetry contour line where the regional SOFAR channel axis is located. The beginning of the T wave usually travel with a path that follows Fermat's principle, instead of the shortest path. The T wave ends when there are no effective conversion points available in the regional bathymetry. The maximum amplitude of the T phase usually has a path with the least solid-earth leg. In addition, T phase amplitude decreases when a typhoon passed between the conversion points and the OBS, possibly due to the strong winds causing mixing of the upper SOFAR channel, making the waveguide less effective.

Chi, W.; Kuo, B.; Tu, T.; Lin, C.; Ando, M.; Lin, C.; Collina, J.

2008-12-01

292

Freshwater lenses as archive of climate, groundwater recharge, and hydrochemical evolution: Insights from depth-specific water isotope analysis and age determination on the island of Langeoog, Germany  

NASA Astrophysics Data System (ADS)

age stratification of a freshwater lens on the island of Langeoog, Germany, was reconstructed through depth-specific sampling and groundwater dating using the tritium-helium method. The stratification is strongly affected by the land use and resulting differences in recharge rates. Infiltration at the dune tops is significantly lower than in the valleys, due to repellency of the dry sand. Dune valleys contribute up to four times more groundwater recharge per area than other areas. Housing development in dune areas might therefore significantly decrease the available fresh groundwater. The freshwater column shows a distinct increase of stable isotope values with decreasing depths. Hence, the freshwater lens contains a climate archive which reflects changing environmental conditions at the time of recharge. Combined with tritium-helium dating, this pattern could be matched to climate records which show an increase of the temperature at the time of recharge and rainfall rates during the last 50 years. The spatial and temporal developments of water chemistry during the passage through the lens follow a marked pattern from a sodium and chloride-dominated rainwater of low conductivity to a more mineralized sodium bicarbonate water type, caused by dissolution of carbonate shells close to the surface and subsequent ion exchange of calcium for sodium in the deeper parts.

Houben, Georg J.; Koeniger, Paul; Sültenfuß, Jürgen

2014-10-01

293

Life Cycle Water Consumption and Water Resource Assessment for Utility-Scale Geothermal Systems: An In-Depth Analysis of Historical and Forthcoming EGS Projects  

SciTech Connect

This report is the third in a series of reports sponsored by the U.S. Department of Energy Geothermal Technologies Program in which a range of water-related issues surrounding geothermal power production are evaluated. The first report made an initial attempt at quantifying the life cycle fresh water requirements of geothermal power-generating systems and explored operational and environmental concerns related to the geochemical composition of geothermal fluids. The initial analysis of life cycle fresh water consumption of geothermal power-generating systems identified that operational water requirements consumed the vast majority of water across the life cycle. However, it relied upon limited operational water consumption data and did not account for belowground operational losses for enhanced geothermal systems (EGSs). A second report presented an initial assessment of fresh water demand for future growth in utility-scale geothermal power generation. The current analysis builds upon this work to improve life cycle fresh water consumption estimates and incorporates regional water availability into the resource assessment to improve the identification of areas where future growth in geothermal electricity generation may encounter water challenges. This report is divided into nine chapters. Chapter 1 gives the background of the project and its purpose, which is to assess the water consumption of geothermal technologies and identify areas where water availability may present a challenge to utility-scale geothermal development. Water consumption refers to the water that is withdrawn from a resource such as a river, lake, or nongeothermal aquifer that is not returned to that resource. The geothermal electricity generation technologies evaluated in this study include conventional hydrothermal flash and binary systems, as well as EGSs that rely on engineering a productive reservoir where heat exists, but where water availability or permeability may be limited. Chapter 2 describes the approach and methods for this work and identifies the four power plant scenarios evaluated: a 20-MW EGS binary plant, a 50-MW EGS binary plant, a 10-MW hydrothermal binary plant, and a 50-MW hydrothermal flash plant. The methods focus on (1) the collection of data to improve estimation of EGS stimulation volumes, aboveground operational consumption for all geothermal technologies, and belowground operational consumption for EGS; and (2) the mapping of the geothermal and water resources of the western United States to assist in the identification of potential water challenges to geothermal growth. Chapters 3 and 4 present the water requirements for the power plant life cycle. Chapter 3 presents the results of the current data collection effort, and Chapter 4 presents the normalized volume of fresh water consumed at each life cycle stage per lifetime energy output for the power plant scenarios evaluated. Over the life cycle of a geothermal power plant, from construction through 30 years of operation, the majority of water is consumed by plant operations. For the EGS binary scenarios, where dry cooling was assumed, belowground operational water loss is the greatest contributor depending upon the physical and operational conditions of the reservoir. Total life cycle water consumption requirements for air-cooled EGS binary scenarios vary between 0.22 and 1.85 gal/kWh, depending upon the extent of belowground operational water consumption. The air-cooled hydrothermal binary and flash plants experience far less fresh water consumption over the life cycle, at 0.04 gal/kWh. Fresh water requirements associated with air- cooled binary operations are primarily from aboveground water needs, including dust control, maintenance, and domestic use. Although wet-cooled hydrothermal flash systems require water for cooling, these plants generally rely upon the geofluid, fluid from the geothermal reservoir, which typically has high salinity and total dissolved solids concentration and is much warmer than normal groundwater sources, for their cooling water needs; thus,

Clark, Corrie E. [Environmental Science Division] [Environmental Science Division; Harto, Christopher B. [Environmental Science Division] [Environmental Science Division; Schroeder, Jenna N. [Environmental Science Division] [Environmental Science Division; Martino, Louis E. [Environmental Science Division] [Environmental Science Division; Horner, Robert M. [Environmental Science Division] [Environmental Science Division

2013-11-05

294

Life Cycle Water Consumption and Water Resource Assessment for Utility-Scale Geothermal Systems: An In-Depth Analysis of Historical and Forthcoming EGS Projects  

DOE Data Explorer

This report is the third in a series of reports sponsored by the U.S. Department of Energy Geothermal Technologies Program in which a range of water-related issues surrounding geothermal power production are evaluated. The first report made an initial attempt at quantifying the life cycle fresh water requirements of geothermal power-generating systems and explored operational and environmental concerns related to the geochemical composition of geothermal fluids. The initial analysis of life cycle fresh water consumption of geothermal power-generating systems identified that operational water requirements consumed the vast majority of water across the life cycle. However, it relied upon limited operational water consumption data and did not account for belowground operational losses for enhanced geothermal systems (EGSs). A second report presented an initial assessment of fresh water demand for future growth in utility-scale geothermal power generation. The current analysis builds upon this work to improve life cycle fresh water consumption estimates and incorporates regional water availability into the resource assessment to improve the identification of areas where future growth in geothermal electricity generation may encounter water challenges.

Schroeder, Jenna N.

295

Life Cycle Water Consumption and Water Resource Assessment for Utility-Scale Geothermal Systems: An In-Depth Analysis of Historical and Forthcoming EGS Projects  

SciTech Connect

This report is the third in a series of reports sponsored by the U.S. Department of Energy Geothermal Technologies Program in which a range of water-related issues surrounding geothermal power production are evaluated. The first report made an initial attempt at quantifying the life cycle fresh water requirements of geothermal power-generating systems and explored operational and environmental concerns related to the geochemical composition of geothermal fluids. The initial analysis of life cycle fresh water consumption of geothermal power-generating systems identified that operational water requirements consumed the vast majority of water across the life cycle. However, it relied upon limited operational water consumption data and did not account for belowground operational losses for enhanced geothermal systems (EGSs). A second report presented an initial assessment of fresh water demand for future growth in utility-scale geothermal power generation. The current analysis builds upon this work to improve life cycle fresh water consumption estimates and incorporates regional water availability into the resource assessment to improve the identification of areas where future growth in geothermal electricity generation may encounter water challenges.

Schroeder, Jenna N.

2013-08-31

296

Water wave interaction with a sphere in a two-layer fluid flowing through a channel of finite depth  

Microsoft Academic Search

Using linear water wave theory, we consider a three-dimensional problem involving the interaction of waves with a sphere in\\u000a a fluid consisting of two layers with the upper layer and lower layer bounded above and below, respectively, by rigid horizontal\\u000a walls, which are approximations of the free surface and the bottom surface; these walls can be assumed to constitute a

S. Mohapatra; S. N. Bora

2009-01-01

297

Distribution and abundance of marine fish larvae in relation to effluent plumes from sewage outfalls and depth of water  

Microsoft Academic Search

Fish larvae were sampled in and below three separate sewage plumes associated with the cliff-face (shoreline) outfalls at North Head, Bondi and Malabar, and at three control (non-plume) sites located>8 km away from the sewage outfalls, at Long Reef, Port Hacking and Marley Beach, in nearshore waters off Sydney, south-eastern Australia. Samples were collected at the surface and at 20

C. A. Gray; N. M. Otway; F. A. Laurenson; A. G. Miskiewicz; R. L. Pethebridge

1992-01-01

298

Temperature and Water Depth Monitoring Within Chum Salmon Spawning Habitat Below Bonneville Dam -- Annual Report -- October 2007-September 2008  

SciTech Connect

The overall goal of the project described in this report is to provide a sound scientific basis for operation of the Federal Columbia River Power System (FCRPS) in ways that will effectively protect and enhance chum salmon populations----a species listed in March 1999 as threatened under the Endangered Species Act of 1973 (ESA). The study objective during fiscal year 2008 was to provide real-time data on Ives Island area water temperature and water surface elevations from the onset of chum salmon spawning through the end of chum salmon emergence. Sampling locations included areas where riverbed temperatures were elevated, potentially influencing alevin development and emergence timing. In these locations, hydrosystem operation caused large, frequent changes in river discharge that affected salmon habitat by dewatering redds and altering egg pocket temperatures. The 2008 objective was accomplished using temperature and water-level sensors deployed inside piezo¬meters. Sensors were integrated with a radio telemetry system such that real-time data could be downloaded remotely and posted hourly on the Internet.

Arntzen, Evan V.

2009-07-14

299

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

300

Treatment of steam-assisted gravity drainage water using low coagulant dose and Fenton oxidation.  

PubMed

The use of coagulation and Fenton oxidation was studied for total organic carbon (TOC) and silica removal from steam-assisted gravity drainage (SAGD) water at 800C and two different concentrations replicating the stream feeding the warm lime softening unit having 675 mg/L TOC and 350 mg/L silica and the blowdown of the once through steam generator having 3700mg/L TOC and 2585 mg/L silica. Coagulation was carried out by the addition of FeCl3, Al(NO3)3 or Ca(NO3)2. The results showed that Fe(III) salt outperformed Al(III) and Ca(II) salts. A two-stage addition of 2.5 g FeCl3 per g TOC intermediated by a filtration unit resulted in approximately 72% TOC removal and more than 80% silica removal while maintaining low solid waste. Comparing results pertaining to coagulant concentration and final pH, it can be easily concluded that silica removal is governed by the resultant pH, whereas TOC removal was accomplished through surface neutralization and localized enmeshment coagulation. Fenton oxidation is proposed to further treat the filtrate obtained from the second stage Fe(III) coagulation. An additional 10% TOC removal could be achieved; at seven times lower H202 dose in the presence of Fe2+ or Fe0 reagent. Moreover, the advanced Fenton process resulted in high silica removal as a result of adsorption onto Fe(OH)3 precipitate, which formed at the equilibrium pH of the system. PMID:24956753

Al-As'ad, Ahmad; Husein, Maen M

2014-08-01

301

Temperature and Water Depth Monitoring Within Chum Salmon Spawning Habitat Below Bonneville Dam : Annual Report October 2007-September 2008  

SciTech Connect

The overall goal of the project described in this report is to provide a sound scientific basis for operation of the Federal Columbia River Power System (FCRPS) in ways that will effectively protect and enhance chum salmon populations - a species listed in March 1999 as threatened under the Endangered Species Act of 1973 (ESA). The study objective during fiscal year 2008 was to provide real-time data on Ives Island area water temperature and water surface elevations from the onset of chum salmon spawning through the end of chum salmon emergence. Sampling locations included areas where riverbed temperatures were elevated, potentially influencing alevin development and emergence timing. In these locations, hydrosystem operation caused large, frequent changes in river discharge that affected salmon habitat by dewatering redds and altering egg pocket temperatures. The 2008 objective was accomplished using temperature and water-level sensors deployed inside piezometers. Sensors were integrated with a radio telemetry system such that real-time data could be downloaded remotely and posted hourly on the Internet. During our overall monitoring period (October 2007 through June 2008), mean temperature in chum spawning areas was nearly 2 C warmer within the riverbed than in the overlying river. During chum salmon spawning (mid-November 2007 through December2007), mean riverbed temperature in the Ives Island area was 14.5 C, more than 5 C higher than in the river, where mean temperature was 9.4 C. During the incubation period (January 2008 through mid-May 2008), riverbed temperature was approximately 3 C greater than in the overlying river (10.5 C and 7.2 C, respectively). Chum salmon preferentially select spawning locations where riverbed temperatures are elevated; consequently the incubation time of alevin is shortened before they emerge in the spring.

Arntzen, E.V. [Pacific Northwest National Laboratory

2009-07-14

302

Possible Extent and Depth of Salt Contamination in Ground Water Using Geophysical Techniques, Red River Aluminum Site, Stamps, Arkansas, April 2003  

USGS Publications Warehouse

A surface-geophysical investigation of the Red River Aluminum site at Stamps, Arkansas, was conducted in cooperation with the Arkansas Department of Environmental Quality to determine the possible extent and depth of saltwater contamination. Water-level measurements indicate the distance to water level below land surface ranges from about 1.2 to 3.9 feet (0.37 to 1.19 meters) in shallow monitor wells and about 10.5 to 17.1 feet (3.20 to 5.21 meters) in deeper monitoring wells. The two-dimensional, direct-current resistivity method identified resistivities less than 5 ohm-meters which indicated possible areas of salt contamination occurring in near-surface or deep subsurface ground water along four resistivity lines within the site. One line located east of the site yielded data that demonstrated no effect of salt contamination. Sections from two of the five data sets were modeled. The input model grids were created on the basis of the known geology and the results and interpretations of borehole geophysical data. The clay-rich Cook Mountain Formation is modeled as 25 ohm-meters and extends from 21 meters (68.9 feet) below land surface to the bottom of the model (about 52 meters (170.6 feet)). The models were used to refine interpretation of the resistivity data and to determine extent of saltwater contamination and depth to the Cook Mountain Formation. Data from the resistivity lines indicate both near-surface and subsurface saltwater contamination. The near-surface contamination appears as low resistivity (less than 5 ohm-meters) on four of the five resistivity lines, extending up to 775 meters (2,542.8 feet) horizontally in a line that traverses the entire site south to north. Model resistivity data indicate that the total depth of saltwater contamination is about 18 meters (59 feet) below land surface. Data from four resistivity lines identified areas containing low resistivity anomalies interpreted as possible salt contamination. A fifth line located just east of the site showed no saltwater contamination.

Stanton, Gregory P.; Kress, Wade; Hobza, Christopher M.; Czarnecki, John B.

2003-01-01

303

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

304

Tsunami and the Depth of the Ocean  

NSDL National Science Digital Library

An inquiry approach to using the celerity (=velocity) of a tsunami to measure the depth of the ocean along its path. Tsunami are shallow-water waves, because their wavelengths are so long relative to ocean depth. Shallow-water wave celerity depends on ocean depth. Students reason this out. They then determine the distance of the path of the tsunami from the epicenter of the 1964 Alaska Good Friday earthquake tsunami to various locations, use tsunami arrival times to calculate the velocity, and re-arrange the shallow-water celerity equation to calculate depth. Students evaluate the geographic distribution of water depths.

Martin Farley

305

Integrating flood depth and plant resistance with chlorantraniliprole seed treatments for management of rice water weevil, Lissorhoptrus oryzophilus (Coleoptera: Curculionidae).  

PubMed

Chlorantraniliprole seed treatments in rice provide effective suppression of rice water weevil populations in the United States; however, heavy reliance on prophylactic insecticide treatments as a sole strategy could destabilize management programs for this insect. The present research evaluated the compatibility of seed treatments with two other potential management tactics-plant resistance and shallow flooding-by conducting two split-plot experiments in 2009 and 2011. In both experiments, no substantial antagonism was found among the 3 different tactics. Statistical interactions in these experiments arose from the strong and persistent effects of chlorantraniliprole on larval densities rather than incompatibility of tactics. In 2009, weevil densities differed among varieties and were significantly lower on the cultivar "Jefferson." In 2011, weevil densities were reduced significantly in shallow-flooded plots compared to deep-flooded plots. Significant reductions in weevil numbers by chlorantraniliprole seed treatments, even at application rates 5 fold lower than commercially recommended rates, demonstrated the potential to reduce application rates of this highly potent larvicide. These latter results suggest that future studies on the relationship between chlorantraniliprole seed treatment rate and weevil fitness are warranted. PMID:25176158

Lanka, Srinivas K; Blouin, David C; Stout, Michael J

2014-09-01

306

Topic in Depth - Chlorine  

NSDL National Science Digital Library

Chlorine, a chemical element whose name means â??pale green,â?ť is explored from a number of angles in this informative Topic in Depth.Weâ??ve 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.

307

Distribution and biogeographic trends of decapod assemblages from Galicia Bank (NE Atlantic) at depths between 700 and 1800 m, with connexions to regional water masses  

NASA Astrophysics Data System (ADS)

The Galicia Bank (NE Atlantic, 42°67?N-11°74?W) is an isolated seamount, near NW Spain, a complex geomorphological and sedimentary structure that receives influences from contrasting water masses of both northern and southern origins. Within the project INDEMARES, three cruises were performed on the bank in 2009 (Ecomarg0709), 2010 (BanGal0810) and 2011 (BanGal0811) all in July-August. Decapods and other macrobenthic crustaceans (eucarids and peracarids) were collected with different sampling systems, mainly beam trawls (BT, 10 mm of mesh size at codend) and a GOC73 otter trawl (20 mm mesh size). Sixty-seven species of decapod crustaceans, 6 euphausiids, 19 peracarids and 1 ostracod were collected at depths between 744 and 1808 m. We found two new species, one a member of the Chirostylidae, Uroptychus cartesi Baba & Macpherson, 2012, the other of the Petalophthalmidae (Mysida) Petalophthalmus sp. A, in addition to a number of new biogeographic species records for European or Iberian waters. An analysis of assemblages showed a generalized species renewal with depth, with different assemblages between 744 and ca. 1400 m (the seamount top assemblage, STA) and between ca. 1500 and 1800 m (the deep-slope assemblage over seamount flanks, DSA). These were respectively associated with Mediterranean outflow waters (MOW) and with Labrador Sea Water (LSW). Another significant factor separating different assemblages over the Galician Bank was the co-occurrence of corals (both colonies of hard corals such as Lophelia pertusa and Madrepora oculata and/or gorgonians) in hauls. Munidopsids (Munidopsis spp.), chirostylids (Uroptychus spp.), and the homolodromiid Dicranodromia mahieuxii formed a part of this coral-associated assemblage. Dominant species at the STA were the pandalid Plesionika martia (a shrimp of subtropical-southern distribution) and the crabs Bathynectes maravigna and Polybius henslowii, whereas dominant species in the DSA were of northern origin, the lithodid Neolithodes grimaldii and the crangonid Glyphocrangon longiristris, likely associated with LSW. The diversity (H and J) of small crustaceans (collected with BT) seemed to be controlled by the phytoplankton blooms (satellite Chl a data) over bank surface 3 months before the samplings, both at the top (Spearman r=0.57, p=0.03) and on the flanks (r=0.74, p=0.02) of Galicia Bank, while no significant relationships with Chl a were found for the larger decapods collected with GOC73, on average they feed at the higher trophic levels than those collected with BT.

Cartes, J. E.; Papiol, V.; Frutos, I.; Macpherson, E.; González-Pola, C.; Punzón, A.; Valeiras, X.; Serrano, A.

2014-08-01

308

Modeling soil water fluxes in two arable Chernozems with different depth to carbonates after fifty years under bare fallow and under corn  

NASA Astrophysics Data System (ADS)

Arable Chernozems of the East European Plain were studied in Voronezh region (51°36' N, 38°58' E, 180-185 m AMSL). The studied soils were formed on calcareous loess-like loam parent material in well-drained position with groundwater level at 8-10 m depth. The mean annual air temperature at the site is 6.9 °C, mean annual precipitation is 587 mm. The weather conditions are highly variable: the extreme values of monthly precipitation registered in June were 7 (in 1960) and 219 mm (in 1988); the extreme daily value of precipitation was 95 mm (in 1988); the extreme air temperatures registered in June were -1.6 and 38.9 °C. The first experimental plot was under corn monocrop and another one was under bare fallow for 50 years. The depth to the top of the carbonate horizon was 1.4-1.6 m under corn and 0.8 m under bare fallow. We supposed that this difference in carbonate depths is due to carbonate accumulation in the upper soil layers under bare fallow and that it can be explained by the repeating upward water fluxes, which are much greater under bare fallow than those under corn. To test this hypothesis a series of simulations was carried out using the Hydrus-1D modeling environment. Simulation of soil hydrology was performed for the vegetation period. The depth of modeled soil profile was 2 m. Sand, silt and clay contents were about 20, 40 and 40 % and were similar for both plots. The lower boundary condition was free drainage. Monthly precipitation was set equal to (1) long-term average norm, (2) half-norm, (3) two norms and (4) three norms. The monthly distribution of precipitation was either (a) two rainy days at the beginning of each month followed by 28-days dry period or (b) one rainy day at the beginning of each decade followed by 9-days dry period. Evapotranspiration during dry periods was estimated using the standardized FAO56 Penman - Monteith model. Simulations were performed for each combination of (1)-(4) and (a)-(b) conditions and for the real-time weather data. The two plots differed in profile moisture distribution in all simulation series. The moisture content in the upper 0-0.5 m layer was higher under corn and the moisture content at the 0.5 m depth and deeper was significantly higher under bare fallow. The repeating upward fluxes of soil water were obtained only for the plot under bare fallow. The thickness of the soil layer with downward and upward fluxes increased with monthly precipitation. This result indicates the particular role of the years with extra precipitation in the process of carbonate accumulation within the upper part of the soil profile under bare fallow.

Arkhangelskaya, Tatiana; Khokhlova, Olga

2014-05-01

309

Influence of Tap Water Quality and Household Water Use Activities on Indoor Air and Internal Dose Levels of Trihalomethanes  

PubMed Central

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 postactivity. 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

2005-01-01

310

Sunphotometric Measurement of Columnar H2O and Aerosol Optical Depth During the 3rd Water Vapor IOP in Fall 2000 at the SGP ARM Site  

NASA Technical Reports Server (NTRS)

We conducted ground-based measurements with the Ames Airborne Tracking 6-channel Sunphotometer (AATS-6) during the 3rd Water Vapor IOP (WVIOP3), September 18 - October 8, 2000 at the SGP ARM site. For this deployment our primary result was columnar water vapor (CWV) obtained from continuous solar transmittance measurements in the 0.94-micron band. In addition, we simultaneously measured aerosol optical depth (AOD) at 380, 450, 525, 864 and 1020 nm. During the IOP, preliminary results of CWV and AOD were displayed in real-time. The result files were made available to other investigators by noon of the next day. During WVIOP3 those data were shown on the daily intercomparison plots on the IOP web-site. Our preliminary results for CWV fell within the spread of values obtained from other techniques. After conclusion of WVIOP3, AATS-6 was shipped directly to Mauna Loa, Hawaii for post-mission calibration. The updated calibration, a cloud screening technique for AOD, along with other mostly cosmetic changes were applied to the WVIOP3 data set and released as version 0.1. The resulting changes in CWV are small, the changes in AOD and Angstrom parameter are more noticeable. Data version 0.1 was successfully submitted to the ARM External Data Center. In the poster we will show data examples for both CWV and AOD. We will also compare our CWV results with those obtained from a GPS (Global Positioning System) slant path method.

Schmid, B; Eilers, J. A.; McIntosh, D. M.; Longo, K.; Livingston, J. M.; Redemann, J.; Russell, P. B.; Braun, J.; Rocken, C.; Hipskind, R. Stephen (Technical Monitor)

2001-01-01

311

Estimating Snow Water Equivalent in the Swedish mountains by scaling snow depth measurements based on in situ data and local topography using passive and active remote sensing  

NASA Astrophysics Data System (ADS)

Estimating the snow water equivalent (SWE) of the seasonal snow pack in the Swedish mountains is key information for the prediction of spring flood rates and the contribution to water reservoirs in Hydro-power production. The snow pack properties determining the SWE (snow depth and snow density) show spatial variations caused by synoptic scale weather patterns (air temperature gradients, wind and precipitation patterns) topography and vegetation. By establishing the relationship between accumulation patterns and physical parameters in the landscape a model of the spatial organization of the snow pack and its change over the season can be determined. By identifying the frequency and amplitude of topography in the Swedish mountain regions and by measuring snow accumulation in these regions we can increase the accuracy of the estimation of SWE. By using multiple parameters sampled in the snow pack from four sites in the Swedish mountains we quantify the local variability of SWE. This information will then be up-scaled to local coverage based on interpolation weighted on topography and vegetation. By validation of satellite imagery and existing snow cover products the information can be up-scaled from high-resolution field data to regional scale covering the Swedish mountain range in order to derive new satellite algorithms.

Ingvander, Susanne; Johansson, Cecilia; Brandel, Malin; Brown, Ian

2014-05-01

312

Examining the interrelationship between DOC, bromide and chlorine dose on DBP formation in drinking water--a case study.  

PubMed

During drinking water treatment aqueous chlorine and bromine compete to react with natural organic matter (NOM). Among the products of these reactions are potentially harmful halogenated disinfection by-products, notably four trihalomethanes (THM4) and nine haloacetic acids (HAAs). Previous research has concentrated on the role of bromide in chlorination reactions under conditions of a given NOM type and/or concentration. In this study different concentrations of dissolved organic carbon (DOC) from U.K. lowland water were reacted with varying amounts of bromide and chlorine in order to examine the interrelationship between the three reactants in the formation of THM4, dihaloacetic acids (DHAAs) and trihaloacetic acids (THAAs). Results showed that, in general, molar yields of THM4 increased with DOC, bromide and chlorine concentrations, although yields did fluctuate versus chlorine dose. In contrast both DHAA and THAA yields were mainly independent of changes in bromide and chlorine dose at low DOC (1 mg·L(-1)), but increased with chlorine dose at higher DOC concentrations (4 mg·L(-1)). Bromine substitution factors reached maxima of 0.80, 0.67 and 0.65 for the THM4, DHAAs and THAAs, respectively, at the highest bromide/chlorine ratio studied. These results suggest that THM4 formation kinetics depend on both oxidation and halogenation steps, whereas for DHAAs and THAAs oxidation steps are more important. Furthermore, they indicate that high bromide waters may prove more problematic for water utilities with respect to THM4 formation than for THAAs or DHAAs. While mass concentrations of all three groups increased in response to increased bromide incorporation, only the THMs also showed an increase in molar yield. Overall, the formation behaviour of DHAA and THAA was more similar than that of THM4 and THAA. PMID:24176694

Bond, Tom; Huang, Jin; Graham, Nigel J D; Templeton, Michael R

2014-02-01

313

Responses of Ecosystem Methane, Carbon and Water Fluxes to Long-Term Experimental Increases in Temperature, Soil Moisture and Snow Depth in NW Greenland  

NASA Astrophysics Data System (ADS)

The carbon balance of permafrost zone ecosystems may be vulnerable to changes in growing season temperature and precipitation. But the effects of climate change on C cycling in the high arctic are largely unknown, particularly for multiple simultaneous changes that may reduce or reinforce each other. We examined the effects of single or multiple environmental changes (increased temperature, soil moisture or snow depth, in comparison to control plots) on a high arctic tundra ecosystem at a global warming manipulation experiment in NW Greenland. We collected 3 years of data during the growing season from 2010 to 2012. Plant and soil fluxes of methane, carbon and water were measured continuously using automated chambers coupled to a CH4 laser analyzer. We observed CH4 uptake of 1-2 nmol m-2 s-1 across all treatment and control plots. CH4 uptake was inversely correlated with soil moisture over the seasonal time scale, and showed similar rates and patterns on the interannual time scale. Net carbon and water fluxes in the elevated temperature plots were similar to the control plots, but fluxes were significantly enhanced in the combined treatment of elevated temperature and added water. Total growing season C accumulation was 3-5 times greater, water fluxes were 1.5-2 times higher, and water use efficiency was about 3 times higher in the combined treatment than the control. Measurements of leaf level physiology and morphology revealed the role of different compartments and mechanisms in determining the response of the net ecosystem fluxes. Plants at elevated temperature had higher photosynthetic capacity, leaf N content and specific leaf area than control plants, indicating enhanced soil respiration may balance increased photosynthetic uptake. In contrast, watering alone or in the combined treatment resulted in a decreased N availability to the plants, with photosynthetic rates comparable to control plants. However, a 35% increase in leaf area in the combined treatment resulted in higher C uptake at the ecosystem scale relevant for atmospheric CO2 drawdown. The effects of climate change on ecosystem-atmosphere fluxes in the high arctic clearly depends on the interactions between plant strategies, soil responses and the relative impacts of multiple climatic drivers.

Seibt, U.; Maseyk, K. S.; Lupascu, M.; Lett, C.; Welker, J. M.; Czimczik, C. I.

2012-12-01

314

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

315

In situ fabrication of depth-type hierarchical CNT/quartz fiber filters for high efficiency filtration of sub-micron aerosols and high water repellency  

NASA Astrophysics Data System (ADS)

We fabricated depth-type hierarchical CNT/quartz fiber (QF) filters through in situ growth of CNTs upon quartz fiber (QF) filters using a floating catalyst chemical vapor deposition (CVD) method. The filter specific area of the CNT/QF filters is more than 12 times higher than that of the pristine QF filters. As a result, the penetration of sub-micron aerosols for CNT/QF filters is reduced by two orders of magnitude, which reaches the standard of high-efficiency particulate air (HEPA) filters. Simultaneously, due to the fluffy brush-like hierarchical structure of CNTs on QFs, the pore size of the hybrid filters only has a small increment. The pressure drop across the CNT/QF filters only increases about 50% with respect to that of the pristine QF filters, leading to an obvious increased quality factor of the CNT/QF filters. Scanning electron microscope images reveal that CNTs are very efficient in capturing sub-micron aerosols. Moreover, the CNT/QF filters show high water repellency, implying their superiority for applications in humid conditions.We fabricated depth-type hierarchical CNT/quartz fiber (QF) filters through in situ growth of CNTs upon quartz fiber (QF) filters using a floating catalyst chemical vapor deposition (CVD) method. The filter specific area of the CNT/QF filters is more than 12 times higher than that of the pristine QF filters. As a result, the penetration of sub-micron aerosols for CNT/QF filters is reduced by two orders of magnitude, which reaches the standard of high-efficiency particulate air (HEPA) filters. Simultaneously, due to the fluffy brush-like hierarchical structure of CNTs on QFs, the pore size of the hybrid filters only has a small increment. The pressure drop across the CNT/QF filters only increases about 50% with respect to that of the pristine QF filters, leading to an obvious increased quality factor of the CNT/QF filters. Scanning electron microscope images reveal that CNTs are very efficient in capturing sub-micron aerosols. Moreover, the CNT/QF filters show high water repellency, implying their superiority for applications in humid conditions. Electronic supplementary information (ESI) available: Schematic of the synthesis process of the CNT/QF filter; typical size distribution of atomized polydisperse NaCl aerosols used for air filtration testing; images of a QF filter and a CNT/QF filter; SEM image of a CNT/QF filter after 5 minutes of sonication in ethanol; calculation of porosity and filter specific area. See DOI: 10.1039/c3nr34325a

Li, Peng; Zong, Yichen; Zhang, Yingying; Yang, Mengmeng; Zhang, Rufan; Li, Shuiqing; Wei, Fei

2013-03-01

316

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. PMID:17365038

Zhou, Yue; Benson, Janet M.; Irvin, Clinton; Irshad, Hammad; Cheng, Yung-Sung

2010-01-01

317

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

318

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

319

33 CFR 183.215 - Reference depth.  

Code of Federal Regulations, 2010 CFR

...215 Reference depth. Reference depth is the minimum...between the uppermost surface of the submerged...the surface of the water measured at the...there is no deck surface at the centerline...the reference depth is the average...

2010-07-01

320

33 CFR 183.315 - Reference depth.  

Code of Federal Regulations, 2010 CFR

...315 Reference depth. Reference depth is the minimum...between the uppermost surface of the submerged...the surface of the water measured at the...there is no deck surface at the centerline...the reference depth is the average...

2010-07-01

321

A practical method for determining organ dose during CT examination.  

PubMed

A practical method, based on depth dose, for determining organ dose during computed tomography (CT) examination is presented. For 4-slice spiral CT scans, performed at radii of 0, 37.5, 75.0, 112.5, and 150.0 mm, measurement of depth dose has been made using thermoluminescent dosimeters (TLDs) inserted into a modified International Electrotechnical Commission (IEC) standard dosimetry phantom and also additional TLDs placed on the surface of the phantom. A regression equation-linking dose with distance from the center of the phantom has been formulated, from which dose to a point of interest relative to the surface dose can also be calculated. The approximation reflects the attenuation properties of X-rays in the phantom. Using the equation, an estimate of organ dose can be ascertained for CT examination, assuming water equivalence of human tissue and a known organ position and volume. Using the 4-slice spiral scanner, relative doses to a patients' lung have been calculated, the location and size of the lung in vivo being found from the CT scan image, and the lung being divided into 38 segments to calculate the relative dose. Results from our test case show the dose to the lung to have been 69+/-13% of surface dose. PMID:16979343

Cheung, Tsang; Cheng, Qijun; Feng, Dinghua

2007-02-01

322

Figure 1. Wind and tides mix the ocean to great depths. Thus, because of the thermal inertia of this ocean water, it requires at least several decades for the ocean temperature to respond fully to a climate  

E-print Network

1 Figure 1. Wind and tides mix the ocean to great depths. Thus, because of the thermal inertia of this ocean water, it requires at least several decades for the ocean temperature to respond fully to a climate forcing. Can we defuse The Global Warming Time Bomb? All glaciers in Glacier National Park

Glashausser, Charles

323

Dosimetric validation of the Acuros XB Advanced Dose Calculation algorithm: fundamental characterization in water  

NASA Astrophysics Data System (ADS)

This corrigendum intends to clarify some important points that were not clearly or properly addressed in the original paper, and for which the authors apologize. The original description of the first Acuros algorithm is from the developers, published in Physics in Medicine and Biology by Vassiliev et al (2010) in the paper entitled 'Validation of a new grid-based Boltzmann equation solver for dose calculation in radiotherapy with photon beams'. The main equations describing the algorithm reported in our paper, implemented as the 'Acuros XB Advanced Dose Calculation Algorithm' in the Varian Eclipse treatment planning system, were originally described (for the original Acuros algorithm) in the above mentioned paper by Vassiliev et al. The intention of our description in our paper was to give readers an overview of the algorithm, not pretending to have authorship of the algorithm itself (used as implemented in the planning system). Unfortunately our paper was not clear, particularly in not allocating full credit to the work published by Vassiliev et al on the original Acuros algorithm. Moreover, it is important to clarify that we have not adapted any existing algorithm, but have used the Acuros XB implementation in the Eclipse planning system from Varian. In particular, the original text of our paper should have been as follows: On page 1880 the sentence 'A prototype LBTE solver, called Attila (Wareing et al 2001), was also applied to external photon beam dose calculations (Gifford et al 2006, Vassiliev et al 2008, 2010). Acuros XB builds upon many of the methods in Attila, but represents a ground-up rewrite of the solver where the methods were adapted especially for external photon beam dose calculations' should be corrected to 'A prototype LBTE solver, called Attila (Wareing et al 2001), was also applied to external photon beam dose calculations (Gifford et al 2006, Vassiliev et al 2008). A new algorithm called Acuros, developed by the Transpire Inc. group, was built upon many of the methods in Attila, but represents a ground-up rewrite of the solver where the methods were especially adapted for external photon beam dose calculations, and described in Vassiliev et al (2010). Acuros XB is the Varian implementation of the original Acuros algorithm in the Eclipse planning system'. On page 1881, the sentence 'Monte Carlo and explicit LBTE solution, with sufficient refinement, will converge on the same solution. However, both methods produce errors (inaccuracies). In explicit LBTE solution methods, errors are primarily systematic, and result from discretization of the solution variables in space, angle, and energy. In both Monte Carlo and explicit LBTE solvers, a trade-off exists between speed and accuracy: reduced computational time may be achieved when less stringent accuracy criteria are specified, and vice versa' should cite the reference Vassiliev et al (2010). On page 1882, the beginning of the sub-paragraph The radiation transport model should start with 'The following description of the Acuros XB algorithm is as outlined by Vassiliev et al (2010) and reports the main steps of the radiation transport model as implemented in Eclipse'. The authors apologize for this lack of clarity in our published paper, and trust that this corrigendum gives full credit to Vassiliev et al in their earlier paper, with respect to previous work on the Acuros algorithm. However we wish to note that the entire contents of the data and results published in our paper are original and the work of the listed authors. References Gifford K A, Horton J L Jr, Wareing T A, Failla G and Mourtada F 2006 Comparison of a finite-element multigroup discrete-ordinates code with Monte Carlo for radiotherapy calculations Phys. Med. Biol. 51 2253-65 Vassiliev O N, Wareing T A, Davis I M, McGhee J, Barnett D, Horton J L, Gifford K, Failla G, Titt U and Mourtada F 2008 Feasibility of a multigroup deterministic solution method for three-dimensional radiotherapy dose calculations Int. J. Radiat. Oncol. Biol. Phys. 72 220-7 Vassiliev O N, Wareing T A, McGhee J, Fail

Fogliata, Antonella; Nicolini, Giorgia; Clivio, Alessandro; Vanetti, Eugenio; Mancosu, Pietro; Cozzi, Luca

2011-05-01

324

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

325

GENE EXPRESSION DOSE-RESPONSE IN THE MOUSE BLADDER FOLLOWING EXPOSURE TO ARSENATE IN DRINKING WATER  

EPA Science Inventory

The association between drinking water exposures to inorganic arsenic and life-threatening tumors in the human is strongest for bladder cancer. Moreover, a working model for the pathogenesis of human bladder cancer has been developed. To investigate the mode of action for inorgan...

326

Offsite dose calculation manual guidance: Standard radiological effluent controls for pressurized water reactors  

SciTech Connect

This report contains guidance which may be voluntarily used by licensees who choose to implement the provision of Generic Letter 89-01, which allows Radiological Effect Technical Specifications (RETS) to be removed from the main body of the Technical Specifications and placed in the Offsite Dose Calculation Manual (ODCM). Guidance is provided for Standard Effluent Controls definitions, Controls for effluent monitoring instrumentation, Controls for effluent releases, Controls for radiological environmental monitoring, and the basis for Controls. Guidance on the formulation of RETS has been available in draft from (NUREG-0471 and -0473) for a number of years; the current effort simply recasts those RETS into Standard Radiological Effluent Controls for application to the ODCM. Also included for completeness are: (1) radiological environmental monitoring program guidance previously which had been available as a Branch Technical Position (Rev. 1, November 1979); (2) existing ODCM guidance; and (3) a reproduction of generic Letter 89-01.

Meinke, W.W.; Essig, T.H.

1991-04-01

327

Shipboard Sunphotometer Measurements of Aerosol Optical Depth Spectra and Columnar Water Vapor During ACE-2 and Comparison with Selected Land, Ship, Aircraft, and Satellite Measurements  

NASA Technical Reports Server (NTRS)

Analyses of aerosol optical depth (AOD) and colurnmn 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 airplane flew within 70 km of the ship near the time of a NOAA-14/AVHRR satellite overpass and AOD measurements with the 14-channel Ames Airborne Tracking Sunphotometer (AATS-14) above the marine boundary layer (MBL) permitted calculation of AOD within the MBL from the AATS-6 measurements. A detailed column closure test is performed for MBL AOD on 10 July by comparing the AATS-6 MBL AODs with corresponding values calculated by combining shipboard particle size distribution measurements with models of hygroscopic growth and radiosonde humidity profiles (plus assumptions on the vertical profile of the dry particle size distribution and composition). Large differences (30-80% in the mid-visible) between measured and reconstructed AODs are obtained, in large part because of the high sensitivity of the closure methodology to hygroscopic growth models, which vary considerably and have not been validated over the necessary range of particle size/composition distributions. The wavelength dependence of AATS-6 AODs is compared with the corresponding dependence of aerosol extinction calculated from shipboard measurements of aerosol size distribution and of total scattering mearured by a shipboard integrating nephelometer for several days. Results are highly variable, illustrating further the great difficulty of deriving column values from point measurements. AATS-6 CWV values are shown to agree well with corresponding values derived from radiosonde measurements during 8 soundings on 7 days and also with values calculated from measurements taken on 10 July with the AATS-14 and the University of Washington Passive Humidigraph aboard the Pelican.

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

2000-01-01

328

Shipboard Sunphotometer Measurements of Aerosol Optical Depth Spectra and Columnar Water Vapor During ACE-2, and Comparison with Selected Land, Ship, Aircraft, and Satellite Measurements  

NASA Technical Reports Server (NTRS)

Analyses of aerosol optical depth (AOD) and columnar water vapor (CWV) measurements acquired with NASA Ames Research Center's six-channel Airborne Tracking Sunphotometer (AATS-6) operated aboard the R/V (research vehicle) Professor Vodyanitskiy during the second 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 airplane flew within 70 km of the ship near the time of a NOAA (National Oceanographic and Atmospheric Administration)-14/AVHRR (Advanced Very High Resolution Radiometer) satellite overpass and AOD measurements with the 14-channel Ames Airborne Tracking Sunphotometer (AATS-14) above the marine boundary layer (MBL) permitted calculation of AOD within the MBL from the AATS-6 measurements. A detailed column closure test is performed for MBL AOD on 10 July by comparing the AATS-6 MBL AODs with corresponding values calculated by combining shipboard particle size distribution measurements with models of hygroscopic growth and radiosonde humidity profiles (plus assumptions on the vertical profile of the dry particle size distribution and composition). Large differences (30-80% in the mid-visible) between measured and reconstructed AODs are obtained, in large part because of the high sensitivity of the closure methodology to hygroscopic growth models, which vary considerably and have not been validated over the necessary range of particle size/composition distributions. The wavelength dependence of AATS-6 AODs is compared with the corresponding dependence of aerosol extinction calculated from shipboard measurements of aerosol size distribution and of total scattering measured by a shipboard integrating nephelometer for several days. Results are highly variable, illustrating further the great difficulty of deriving column values from point measurements. AATS-6 CWV values are shown to agree well with corresponding values derived from radiosonde measurements during eight soundings on seven days and also with values calculated from measurements taken on 10 July with the AATS-14 and the University of Washington Passive Humidigraph aboard the Pelican.

Livingston, John M.; Kapustin, Vladimir N.; Schmid, Beat; Russell, Philip B.; Quinn, Patricia K.; Bates, Timothy S.; Durkee, Philip A.; Smith, Peter J.; Freudenthaler, Volker; Wiegner, Matthias

2000-01-01

329

Airborne Sunphotometer Measurements of Aerosol Optical Depth and Columnar Water Vapor During the Puerto Rico Dust Experiment, and Comparison with Land, Aircraft, and Satellite Measurements  

NASA Technical Reports Server (NTRS)

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 ASL reproduce the vertical structure measured by coincident aircraft in-situ measurements of total aerosol number and surface area concentration. Calculations show that the spectral dependence of AOD was small (mean Angstrom wavelength exponents of approximately 0.20) within three atmospheric layers defined as the total column beneath the top of each aircraft profile, the region beneath the trade wind inversion, and the region within the Saharan Air Layer (SAL) above the trade inversion. This spectral behavior is consistent with attenuation of incoming solar radiation by large dust particles or by dust plus sea salt. Values of CWV calculated from profile measurements by AATS-6 at 941.9 nm and from aircraft in-situ measurements by a chilled mirror dewpoint hygrometer agree to within approximately 4% (0.13 g/sq cm). AATS-6 AOD values measured on the ground at Roosevelt Roads Naval Air Station and during low altitude aircraft runs over the adjacent Cabras Island aerosol/radiation ground site agree to within 0.004 to 0.030 with coincident data obtained with an AERONET Sun/sky Cimel radiometer located at Cabras Island. For the same observation times, AERONET retrievals of CWV exceed AATS-6 values by a mean of 0.74 g/sq cm (approximately 21 %) for the 2.9-3.9 g/sq cm measured by AATS-6. Comparison of AATS-6 aerosol extinction values obtained during four aircraft ascents over Cabras Island with corresponding values calculated from coincident aerosol backscatter measurements by a ground-based micro-pulse lidar (MPL-Net) located at Cabras yields a similar vertical structure above the trade inversion. Finally, AATS-6 AOD values measured during low altitude aircraft traverses over the ocean are compared with corresponding AOD values retrieved over water from upwelling radiance measurements by the MODIS, TOMS, and GOES-8 Imager satellite sensors, with mixed results. These exercises highlight the need for continued satellite sensor comparison/validation studies to improve satellite AOD retrieval algorithms, and the usefulness of airborne sunphotometer measurements in the validation process.

Livingston, John M.; Russell, Philip B.; Reid, Jeffrey; Redemann, Jens; Schmid, Beat; Allen, Duane A.; Torres, Omar; Levy, Robert C.; Remer, Lorraine A.; Holben, Brent N.; Hipskind, R. Stephen (Technical Monitor)

2002-01-01

330

226Ra and 222Rn concentrations and doses in bottled waters in Spain  

Microsoft Academic Search

Concentrations of 226Ra and 222Rn have been analysed in most of the bottled waters commercially available in Spain. Concentrations up to about 600mBql-1 with a geometric mean of 12mBql-1 were observed for 226Ra. For 222Rn, a geometric mean of 1.2Bql-1 with values ranging from 0.22 to 52Bql-1 were measured. These values are compared with concentrations reported for other countries. An

C. Dueńas; M. C. Fernández; J. Carretero; E. Liger; S. Cańete

1999-01-01

331

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

332

Use of depth information from in-depth photon counting detectors for x-ray spectral imaging: a preliminary simulation study  

NASA Astrophysics Data System (ADS)

Purpose: Photon counting x-ray detectors (PCXD) may improve dose-efficiency but are hampered by limited count rate. They generally have imperfect energy response. Multi-layer ("in-depth") detectors have been proposed to enable higher count rates but the potential benefit of the depth information has not been explored. We conducted a simulation study to compare in-depth detectors against single layer detectors composed of common materials. Both photon counting and energy integrating modes were studied. Methods: Polyenergetic transmissions were simulated through 25cm of water and 1cm of calcium. For PCXD composed of Si, GaAs or CdTe a 120kVp spectrum was used. For energy integrating x-ray detectors (EIXD) made from GaAs, CdTe or CsI, spectral imaging was done using 80 and 140kVp and matched dose. Semi-ideal and phenomenological energy response models were used. To compare these detectors, we computed the Cramér-Rao lower bound (CRLB) of the variance of basis material estimates. Results: For PCXDs with perfect energy response, depth data provides no additional information. For PCXDs with imperfect energy response and for EIXDs the improvement can be significant. E.g., for a CdTe PCXD with realistic energy response, depth information can reduce the variance by ~50%. The improvement depends on the x-ray spectrum. For a semi-ideal Si detector and a narrow x-ray spectrum the depth information has minimal advantage. For EIXD, the in-depth detector has consistent variance reduction (15% and 17%~19% for water and calcium, respectively). Conclusions: Depth information is beneficial to spectral imaging for both PCXD and EIXD. The improvement depends critically on the detector energy response.

Yao, Yuan; Bornefalk, Hans; Hsieh, Scott S.; Danielsson, Mats; Pelc, Norbert J.

2014-03-01

333

Simulating radial dose of ion tracks in liquid water simulated with Geant4-DNA: A comparative study  

NASA Astrophysics Data System (ADS)

An accurate modeling of radial energy deposition around ion tracks is a key requirement of radiation transport software used for simulations in radiobiology at the sub-cellular scale. The work presented in this paper is part of the on-going benchmarking of the “Geant4-DNA” physics processes and models, which are available in the Geant4 Monte Carlo simulation toolkit for the low energy transport of particles in liquid water. We present for the first time radial dose distributions of incident ion tracks simulated with “Geant4-DNA”. Simulation results are compared to other results available in the literature, obtained from analytical calculations, step-by-step Monte Carlo simulations and measurements. They show a reasonable agreement with reference data.

Incerti, S.; Psaltaki, M.; Gillet, P.; Barberet, Ph.; Bardičs, M.; Bernal, M. A.; Bordage, M.-C.; Breton, V.; Davidkova, M.; Delage, E.; El Bitar, Z.; Francis, Z.; Guatelli, S.; Ivanchenko, A.; Ivanchenko, V.; Karamitros, M.; Lee, S. B.; Maigne, L.; Meylan, S.; Murakami, K.; Nieminen, P.; Payno, H.; Perrot, Y.; Petrovic, I.; Pham, Q. T.; Ristic-Fira, A.; Santin, G.; Sasaki, T.; Seznec, H.; Shin, J. I.; Stepan, V.; Tran, H. N.; Villagrasa, C.

2014-08-01

334

Literature and data review for the surface-water pathway: Columbia River and adjacent coastal areas. Hanford Environmental Dose Reconstruction Project  

SciTech Connect

As part of the Hanford Environmental Dose Reconstruction (HEDR) Project, Battelle, Pacific Northwest Laboratories reviewed literature and data on radionuclide concentrations and distribution in the water, sediment, and biota of the Columbia River and adjacent coastal areas. Over 600 documents were reviewed including Hanford reports, reports by offsite agencies, journal articles, and graduate theses. Radionuclide concentration data were used in preliminary estimates of individual dose for the period 1964 through 1966. This report summarizes the literature and database reviews and the results of the preliminary dose estimates.

Walters, W.H.; Dirkes, R.L.; Napier, B.A.

1992-11-01

335

Literature and data review for the surface-water pathway: Columbia River and adjacent coastal areas. Hanford Environmental Dose Reconstruction Project  

SciTech Connect

As part of the Hanford Environmental Dose Reconstruction Project, Pacific Northwest Laboratory reviewed literature and data on radionuclide concentrations and distribution in the water, sediment, and biota of the Columbia River and adjacent coastal areas. Over 600 documents were reviewed including Hanford reports, reports by offsite agencies, journal articles, and graduate theses. Certain radionuclide concentration data were used in preliminary estimates of individual dose for the 1964--1966 time period. This report summarizes the literature and database review and the results of the preliminary dose estimates.

Walters, W.H.; Dirkes, R.L.; Napier, B.A.

1992-04-01

336

Radiation doses to individuals due to ˛ł?U, ˛ł˛Th and ˛˛˛Rn from the immersion in thermal waters and to radon progeny from the inhalation of air inside thermal stations.  

PubMed

In Morocco, thermal waters have been used for decades for the treatment of various diseases. To explore the exposure pathway of (238)U, (232)Th and (222)Rn to the skin of bathers from the immersion in thermal waters, these radionuclides were measured inside waters collected from different Moroccan thermal springs, by means of CR-39 and LR-115 type II solid-state nuclear track detectors (SSNTDs), and corresponding annual committed effective doses to skin were determined. Accordingly, to assess radiation dose due to radon short-lived decay products from the inhalation of air by individuals, concentrations of these radionuclides were measured in indoor air of two thermal stations by evaluating mean critical angles of etching of the CR-39 and LR-115 II SSNTDs. Committed effective doses due to the short-lived radon decay products (218)Po and (214)Po by bathers and working personnel inside the thermal stations studied were determined. PMID:22729272

Misdaq, M A; Ghilane, M; Ouguidi, J; Outeqablit, K

2012-11-01

337

Influence of increasing active-layer depth and continued permafrost degradation on carbon, water and energy fluxes over two forested permafrost landscapes in the Taiga Plains, NWT, Canada  

NASA Astrophysics Data System (ADS)

Recent research suggests an increase in active-layer depth (ALD) in the continuous permafrost zone and degradation of the discontinuous permafrost zone into seasonally frozen. Increasing ALD and continued permafrost degradation will have far-reaching consequences for northern ecosystems including altered regional hydrology and the exposure of additional soil organic carbon (C) to microbial decomposition. These changes might cause positive or negative net feedbacks to the climate system by altering important land surface properties and/or by releasing stored soil organic C to the atmosphere as CO2 and/or CH4. Knowledge gaps exist regarding the links between increasing ALD and/or permafrost degradation, regional hydrology, vegetation composition and structure, land surface properties, and CO2 and CH4 sink-source strengths. The goal of our interdisciplinary project is to shed light on these links by providing a mechanistic understanding of permafrost-thawing consequences for hydrological, ecophysiological and biogeochemical processes at two forested permafrost landscapes in the Taiga Plains, NWT, Canada: Scotty Creek and Havikpak Creek in the discontinuous and in the continuous permafrost zones, respectively (Fig.). The sites will be equipped with identical sets of instrumentation (start: 2013), to measure landscape-scale net exchanges of CO2, CH4, water and energy with the eddy covariance technique. These measurements will be complemented by repeated surveys of surface and frost table topography and vegetation, by land cover-type specific fluxes of CO2 and CH4 measured with a static chamber technique, and by remote sensing-based footprint analysis. With this research we will address the following questions: What is the net effect of permafrost thawing-induced biophysical and biogeochemical feedbacks to the climate system? How do these two different types of feedback differ between the discontinuous and continuous permafrost zones? Is the decrease (increase) in net CO2 (CH4) exchange measured over mostly tundra sites in the continuous permafrost zone generalizable to forested landscapes in both the discontinuous and continuous permafrost zones? With this contribution, we report on the project status, present its objectives and hypotheses, and outline its timeline and sampling design.

Sonnentag, O.; Baltzer, J.; Chasmer, L. E.; Detto, M.; Marsh, P.; Quinton, W. L.

2012-12-01

338

External dose-rate conversion factors of radionuclides for air submersion, ground surface contamination and water immersion based on the new ICRP dosimetric setting.  

PubMed

For the assessment of external doses due to contaminated environment, the dose-rate conversion factors (DCFs) prescribed in Federal Guidance Report 12 (FGR 12) and FGR 13 have been widely used. Recently, there were significant changes in dosimetric models and parameters, which include the use of the Reference Male and Female Phantoms and the revised tissue weighting factors, as well as the updated decay data of radionuclides. In this study, the DCFs for effective and equivalent doses were calculated for three exposure settings: skyshine, groundshine and water immersion. 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. The transport calculations were performed for the source volume within the cut-off distances practically contributing to the dose rates, which were determined by a simplified calculation model. For small tissues for which the reduction of variances are difficult, the equivalent dose ratios to a larger tissue (with lower statistical errors) nearby were employed to make the calculation efficient. Empirical response functions relating photon energies, and the organ equivalent doses or the effective doses were then derived by the use of cubic-spline fitting of the resulting doses for 26 energy points. The DCFs for all radionuclides considered important were evaluated by combining the photon emission data of the radionuclide and the empirical response functions. Finally, 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 three exposure settings were within ±10 % when compared with DCFs in FGR 13. PMID:23542764

Yoo, Song Jae; Jang, Han-Ki; Lee, Jai-Ki; Noh, Siwan; Cho, Gyuseong

2013-01-01

339

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

NASA Astrophysics Data System (ADS)

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 fields ranging from 5 × 5 cm2 to 20 × 20 cm2 for 6 MV, 10 MV and 18 MV photon beams. The variation of the surface dose with angle of incidence and field size was investigated. Also, the exit dose was computed and measured for the same fields and angles of incidence. The dose at the ICRU reference depth was computed. Good agreement (±5%) was achieved between measurements and calculations. The surface dose at the entrance increased with the angle of incidence and/or the field size. The exit dose decreased with the angle of incidence but it increased with field size. The dose at the surface of the patient is mostly dependent on the beam energy, modality and beam obliquity rather than the field size and field separation. By correlating TLD measurements with Monte Carlo calculations, we were able to predict the dose at the skin surface with good accuracy. Knowing the dose received at the surface of the patient can lead to prediction of skin reactions helping with the design of new treatment techniques and alternative dose fractionation schemes.

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

2006-07-01

340

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

341

Clutter depth discrimination using the wavenumber spectrum.  

PubMed

Clutter depth is a key parameter in mid-frequency active sonar systems to discriminate between sources of clutter and targets of interest. A method is needed to remotely discriminate clutter depth by information contained in the backscattered signal-without a priori knowledge of that depth. Presented here is an efficient approach for clutter depth estimation using the structure in the wavenumber spectrum. Based on numerical simulations for a simple test case in a shallow water waveguide, this technique demonstrates the potential capability to discriminate between a clutter source in the water column vs one on the seabed. PMID:24437850

Benjamin Reeder, D

2014-01-01

342

Draft Genome Sequence of Pseudoalteromonas sp. Strain ND6B, an Oil-Degrading Isolate from Eastern Mediterranean Sea Water Collected at a Depth of 1,210 Meters.  

PubMed

Here, we report the draft genome of Pseudoalteromonas sp. strain ND6B, which is able to grow with crude oil as a carbon source. Strain ND6B was isolated from eastern Mediterranean Sea deep water at a depth of 1,210 m. The genome of strain ND6B provides insight into the oil-degrading ability of the Pseudoalteromonas species. PMID:25428968

Harris, Austin P; Techtmann, Stephen M; Stelling, Savannah C; Utturkar, Sagar M; Alshibli, Noor K; Brown, Steven D; Hazen, Terry C

2014-01-01

343

Draft Genome Sequence of Pseudoalteromonas sp. Strain ND6B, an Oil-Degrading Isolate from Eastern Mediterranean Sea Water Collected at a Depth of 1,210 Meters  

PubMed Central

Here, we report the draft genome of Pseudoalteromonas sp. strain ND6B, which is able to grow with crude oil as a carbon source. Strain ND6B was isolated from eastern Mediterranean Sea deep water at a depth of 1,210 m. The genome of strain ND6B provides insight into the oil-degrading ability of the Pseudoalteromonas species. PMID:25428968

Harris, Austin P.; Stelling, Savannah C.; Utturkar, Sagar M.; Alshibli, Noor K.; Brown, Steven D.

2014-01-01

344

Calibration of a TLD-100 powder dosimetric system to verify the absorbed dose to water imparted by 137Cs sources in low dose rate brachytherapy at the oncology unit in the Hospital General de Mexico.  

PubMed

A thermoluminescence dosimetry (TLD) system was characterised at SSDL-ININ to verify the air-kerma strength (S(K)) and dose-to-water (D(W)) values for (137)Cs sources used in low dose rate (LDR) brachytherapy treatments at the Hospital General de Mexico (HGM). It consists of a Harshaw 3500 reader and a set of TLD-100 powder capsules. The samples of TLD-100 powder were calibrated in terms of D(W) vs. nC or nC mg(-1), and their dose response curves were corrected for supralinearity. The D(W) was calculated using the AAPM TG-43 formalism using S(K) for a CDCSM4 (137)Cs reference source. The S(K) value was obtained by using a NE 2611 chamber, and with two well chambers. The angular anisotropy factor was measured with the NE 2611 chamber for this source. The HGM irradiated TLD-100 powder capsules to a reference dose D(W) of 2 Gy with their (137)Cs sources. The percent deviations between the imparted and reference doses were 1.2% < or = Delta < or = 6.5%, which are consistent with the combined uncertainties: 5.6% < or = u(c) < or = 9.8% for D(W). PMID:16644958

Alvarez Romero, J T; Tovar Muńoz, V M; de León, B Salinas; Oviedo, J O Hernández; Barcenas, L Santillán; Milo, C Molero; Monterrubio, J Montoya

2006-01-01

345

KEY COMPARISON: Final report of the SIM 60Co absorbed-dose-to-water comparison SIM.RI(I)-K4  

Microsoft Academic Search

Transfer chambers were used to compare the standards for 60Co absorbed dose to water maintained by seven laboratories. Six of the laboratories were members of the Sistema Interamericano de Metrología (SIM) regional metrology organization while the seventh was the International Atomic Energy Agency (IAEA) laboratory in Vienna. The National Research Council (NRC) acted as the pilot laboratory for the comparison.

C. K. Ross; K. R. Shortt; M. Saravi; A. Meghzifene; V. M. Tovar; R. A. Barbosa; C. N. da Silva; L. Carrizales; S. M. Seltzer

2008-01-01

346

Historical Doses from Tritiated Water and Tritiated Hydrogen Gas Released to the Atmosphere from Lawrence Livermore National Laboratory (LLNL). Part 5. Accidental Releases  

Microsoft Academic Search

Over the course of fifty-three years, LLNL had six acute releases of tritiated hydrogen gas (HT) and one acute release of tritiated water vapor (HTO) that were too large relative to the annual releases to be included as part of the annual releases from normal operations detailed in Parts 3 and 4 of the Tritium Dose Reconstruction (TDR). Sandia National

2007-01-01

347

A Monte Carlo study of absorbed dose distributions in both the vapor and liquid phases of water by intermediate energy electrons based on different condensed-history transport schemes  

NASA Astrophysics Data System (ADS)

Monte Carlo transport calculations of dose point kernels (DPKs) and depth dose profiles (DDPs) in both the vapor and liquid phases of water are presented for electrons with initial energy between 10 keV and 1 MeV. The results are obtained by the MC4 code using three different implementations of the condensed-history technique for inelastic collisions, namely the continuous slowing down approximation, the mixed-simulation with ?-ray transport and the addition of straggling distributions for soft collisions derived from accurate relativistic Born cross sections. In all schemes, elastic collisions are simulated individually based on single-scattering cross sections. Electron transport below 10 keV is performed in an event-by-event mode. Differences on inelastic interactions between the vapor and liquid phase are treated explicitly using our recently developed dielectric response function which is supplemented by relativistic corrections and the transverse contribution. On the whole, the interaction coefficients used agree to better than ~5% with NIST/ICRU values. It is shown that condensed phase effects in both DPKs and DDPs practically vanish above 100 keV. The effect of ?-rays, although decreases with energy, is sizeable leading to more diffused distributions, especially for DPKs. The addition of straggling for soft collisions is practically inconsequential above a few hundred keV. An extensive benchmarking with other condensed-history codes is provided.

Bousis, C.; Emfietzoglou, D.; Hadjidoukas, P.; Nikjoo, H.

2008-07-01

348

Surface-water-quality assessment of the Upper Illinois River basin in Illinois, Indiana, and Wisconsin; cross-sectional and depth variation of water-quality constituents and properties in the Upper Illinois River basin, 1987-88  

USGS Publications Warehouse

Data on water velocity, temperature, specific con- ductance, pH, dissolved oxygen concentration, chlorophyll concentration, suspended sediment con- centration, fecal-coliform counts, and the percen- tage of suspended sediment finer than 62 micrometers ranged up to 21 percent; and cross-section coefficients of variation of the concentrations of suspended sediment, fecal coliform, and chlorophyll ranged from 7 to 115 percent. Midchannel measure- ments of temperature, specific conductance, and pH were within 5 percent of mean cross-sectional values of these properties at the eight sampling sites, most of which appear well mixed because of the effect of dams and reservoirs. Measurements of the concentration of dissolved oxygen at various cross- section locations and at variable sampling depths are required to obtain a representative value of this constituent at these sites. The large varia- bility of concentrations of chlorophyll and suspended sediment, and fecal-coliform counts at the eight sampling sites indicates that composite rather than midchannel or mean values of these constituents are likely to be most representative of the channel cross section.

Marron, Donna C.; Blanchard, Stephen F.

1995-01-01

349

A Study on the Dose Distributions in Various Materials from an Ir-192 HDR Brachytherapy Source  

PubMed Central

Dose distributions of 192Ir HDR brachytherapy in phantoms simulating water, bone, lung tissue, water-lung and bone-lung interfaces using the Monte Carlo codes EGS4, FLUKA and MCNP4C are reported. Experiments were designed to gather point dose measurements to verify the Monte Carlo results using Gafchromic film, radiophotoluminescent glass dosimeter, solid water, bone, and lung phantom. The results for radial dose functions and anisotropy functions in solid water phantom were consistent with previously reported data (Williamson and Li). The radial dose functions in bone were affected more by depth than those in water. Dose differences between homogeneous solid water phantoms and solid water-lung interfaces ranged from 0.6% to 14.4%. The range between homogeneous bone phantoms and bone-lung interfaces was 4.1% to 15.7%. These results support the understanding in dose distribution differences in water, bone, lung, and their interfaces. Our conclusion is that clinical parameters did not provide dose calculation accuracy for different materials, thus suggesting that dose calculation of HDR treatment planning systems should take into account material density to improve overall treatment quality. PMID:22957078

Hsu, Shih-Ming; Wu, Chin-Hui; Lee, Jeng-Hung; Hsieh, Ya-Ju; Yu, Chun-Yen; Liao, Yi-Jen; Kuo, Li-Cheng

2012-01-01

350

Historical Doses from Tritiated Water and Tritiated Hydrogen Gas Released to the Atmosphere from Lawrence Livermore National Laboratory (LLNL). Part 2. LLNL Annual Site-specific Data, 1953 - 2003  

Microsoft Academic Search

It is planned to use the tritium dose model, DCART (Doses from Chronic Atmospheric Releases of Tritium), to reconstruct dose to the hypothetical maximally exposed individual from annual routine releases of tritiated water (HTO) and tritiated hydrogen gas (HT) from all Lawrence Livermore National Laboratory (LLNL) facilities and from the Sandia National (SNL) Laboratory's Tritium Research Laboratory over the last

2005-01-01

351

Dose rate table for a 32P intravascular brachytherapy source from Monte Carlo calculations.  

PubMed

Studies of intravascular brachytherapy to prevent restenosis following angioplasty have shown many promising results. Accurate dose rate tables based on detailed models of the brachytherapy sources are necessary for treatment planning. This work will present an away and along dose rate table for a 27 mm long catheter based 32P beta source. MD-55-2 radiochromic film has been exposed at five different depths (0.5 mm-4 mm) in a polystyrene phantom using a 27 mm long Guidant 32P beta source. The total dose to the active region of the film was determined using the absolute detector response of the MD-55-2 radiochromic film. The Monte Carlo code MCNP4B2 was also used to calculate the dose to the active region of the film using a detailed model of the source, encapsulation, and radiochromic film. The dose to film calculations showed good agreement with the measurements presented in this work with an average difference of 7%. The Monte Carlo calculations were also verified against previously published depth dose in water measurements determined using radiochromic film and plastic scintillator. The depth dose calculations in water showed good agreement with the previously published measurements with the calculations being about 2.5% lower than the film measurements and about 2.5% higher than the scintillator measurements. This work then uses the verified Monte Carlo code to present a dose rate table for the 32P intravascular beta source. PMID:11548948

Bohm, T D; Mourtada, F A; Das, R K

2001-08-01

352

Monte-Carlo-derived insights into dose–kerma–collision kerma inter-relationships for 50?keV–25?MeV photon beams in water, aluminum and copper  

NASA Astrophysics Data System (ADS)

The relationships between D, K and Kcol are of fundamental importance in radiation dosimetry. These relationships are critically influenced by secondary electron transport, which makes Monte-Carlo (MC) simulation indispensable; we have used MC codes DOSRZnrc and FLURZnrc. Computations of the ratios D/K and D/Kcol in three materials (water, aluminum and copper) for large field sizes with energies from 50?keV to 25?MeV (including 6–15?MV) are presented. Beyond the depth of maximum dose D/K is almost always less than or equal to unity and D/Kcol greater than unity, and these ratios are virtually constant with increasing depth. The difference between K and Kcol increases with energy and with the atomic number of the irradiated materials. D/K in ‘sub-equilibrium’ small megavoltage photon fields decreases rapidly with decreasing field size. A simple analytical expression for \\overline{X} , the distance ‘upstream’ from a given voxel to the mean origin of the secondary electrons depositing their energy in this voxel, is proposed: {{\\overline{X}}\\text{emp}}? 0.5{{R}\\text{csda}}(\\overline{{{E}0}}) , where \\overline{{{E}0}} is the mean initial secondary electron energy. These {{\\overline{X}}\\text{emp}} agree well with ‘exact’ MC-derived values for photon energies from 5–25?MeV for water and aluminum. An analytical expression for D/K is also presented and evaluated for 50?keV–25?MeV photons in the three materials, showing close agreement with the MC-derived values.

Kumar, Sudhir; Deshpande, Deepak D.; Nahum, Alan E.

2015-01-01

353

Monte-Carlo-derived insights into dose-kerma-collision kerma inter-relationships for 50?keV-25?MeV photon beams in water, aluminum and copper.  

PubMed

The relationships between D, K and Kcol are of fundamental importance in radiation dosimetry. These relationships are critically influenced by secondary electron transport, which makes Monte-Carlo (MC) simulation indispensable; we have used MC codes DOSRZnrc and FLURZnrc. Computations of the ratios D/K and D/Kcol in three materials (water, aluminum and copper) for large field sizes with energies from 50?keV to 25?MeV (including 6-15?MV) are presented. Beyond the depth of maximum dose D/K is almost always less than or equal to unity and D/Kcol greater than unity, and these ratios are virtually constant with increasing depth. The difference between K and Kcol increases with energy and with the atomic number of the irradiated materials. D/K in 'sub-equilibrium' small megavoltage photon fields decreases rapidly with decreasing field size. A simple analytical expression for [Formula: see text], the distance 'upstream' from a given voxel to the mean origin of the secondary electrons depositing their energy in this voxel, is proposed: [Formula: see text], where [Formula: see text] is the mean initial secondary electron energy. These [Formula: see text] agree well with 'exact' MC-derived values for photon energies from 5-25?MeV for water and aluminum. An analytical expression for D/K is also presented and evaluated for 50?keV-25?MeV photons in the three materials, showing close agreement with the MC-derived values. PMID:25548933

Kumar, Sudhir; Deshpande, Deepak D; Nahum, Alan E

2015-01-21

354

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

355

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 Agency?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...

356

Historical Doses from Tritiated Water and Tritiated Hydrogen Gas Released to the Atmosphere from Lawrence Livermore National Laboratory (LLNL). Part 6. Summary  

SciTech Connect

Throughout fifty-three years of operations, an estimated 792,000 Ci (29,300 TBq) of tritium have been released to the atmosphere at the Livermore site of Lawrence Livermore National Laboratory (LLNL); about 75% was tritium gas (HT) primarily from the accidental releases of 1965 and 1970. Routine emissions contributed slightly more than 100,000 Ci (3,700 TBq) HT and about 75,000 Ci (2,800 TBq) tritiated water vapor (HTO) to the total. A Tritium Dose Reconstruction was undertaken to estimate both the annual doses to the public for each year of LLNL operations and the doses from the few accidental releases. Some of the dose calculations were new, and the others could be compared with those calculated by LLNL. Annual doses (means and 95% confidence intervals) to the potentially most exposed member of the public were calculated for all years using the same model and the same assumptions. Predicted tritium concentrations in air were compared with observed mean annual concentrations at one location from 1973 onwards. Doses predicted from annual emissions were compared with those reported in the past by LLNL. The highest annual mean dose predicted from routine emissions was 34 {micro}Sv (3.4 mrem) in 1957; its upper confidence limit, based on very conservative assumptions about the speciation of the release, was 370 {micro}Sv (37 mrem). The upper confidence limits for most annual doses were well below the current regulatory limit of 100 {micro}Sv (10 mrem) for dose to the public from release to the atmosphere; the few doses that exceeded this were well below the regulatory limits of the time. Lacking the hourly meteorological data needed to calculate doses from historical accidental releases, ingestion/inhalation dose ratios were derived from a time-dependent accident consequence model that accounts for the complex behavior of tritium in the environment. Ratios were modified to account for only those foods growing at the time of the releases. The highest dose from an accidental release was calculated for a release of about 1,500 Ci HTO that occurred in October 1954. The likely dose for this release was probably less than 360 {micro}Sv (36 mrem), but, because of many unknowns (e.g., release-specific meteorological and accidental conditions) and conservative assumptions, the uncertainty was very high. As a result, the upper confidence limit on the predictions, considered a dose that could not have been exceeded, was estimated to be 2 mSv (200 mrem). The next highest dose, from the 1970 accidental release of about 290,000 Ci (10,700 TBq) HT when wind speed and wind direction were known, was one-third as great. Doses from LLNL accidental releases were well below regulatory reporting limits. All doses, from both routine and accidental releases, were far below the level (3.6 mSv [360 mrem] per year) at which adverse health effects have been documented in the literature.

Peterson, S

2007-09-05

357

Historical Doses from Tritiated Water and Tritiated Hydrogen Gas Released to the Atmosphere from Lawrence Livermore National Laboratory (LLNL). Part 5. Accidental Releases  

SciTech Connect

Over the course of fifty-three years, LLNL had six acute releases of tritiated hydrogen gas (HT) and one acute release of tritiated water vapor (HTO) that were too large relative to the annual releases to be included as part of the annual releases from normal operations detailed in Parts 3 and 4 of the Tritium Dose Reconstruction (TDR). Sandia National Laboratories/California (SNL/CA) had one such release of HT and one of HTO. Doses to the maximally exposed individual (MEI) for these accidents have been modeled using an equation derived from the time-dependent tritium model, UFOTRI, and parameter values based on expert judgment. All of these acute releases are described in this report. Doses that could not have been exceeded from the large HT releases of 1965 and 1970 were calculated to be 43 {micro}Sv (4.3 mrem) and 120 {micro}Sv (12 mrem) to an adult, respectively. Two published sets of dose predictions for the accidental HT release in 1970 are compared with the dose predictions of this TDR. The highest predicted dose was for an acute release of HTO in 1954. For this release, the dose that could not have been exceeded was estimated to have been 2 mSv (200 mrem), although, because of the high uncertainty about the predictions, the likely dose may have been as low as 360 {micro}Sv (36 mrem) or less. The estimated maximum exposures from the accidental releases were such that no adverse health effects would be expected. Appendix A lists all accidents and large routine puff releases that have occurred at LLNL and SNL/CA between 1953 and 2005. Appendix B describes the processes unique to tritium that must be modeled after an acute release, some of the time-dependent tritium models being used today, and the results of tests of these models.

Peterson, S

2007-08-15

358

Dose prediction accuracy of anisotropic analytical algorithm and pencil beam convolution algorithm beyond high density heterogeneity interface  

PubMed Central

Purpose: It is well known that photon beam radiation therapy requires dose calculation algorithms. The objective of this study was to measure and assess the ability of pencil beam convolution (PBC) and anisotropic analytical algorithm (AAA) to predict doses beyond high density heterogeneity. Materials and Methods: An inhomogeneous phantom of five layers was created in Eclipse planning system (version 8.6.15). Each layer of phantom was assigned in terms of water (first or top), air (second), water (third), bone (fourth), and water (fifth or bottom) medium. Depth doses in water (bottom medium) were calculated for 100 monitor units (MUs) with 6 Megavoltage (MV) photon beam for different field sizes using AAA and PBC with heterogeneity correction. Combinations of solid water, Poly Vinyl Chloride (PVC), and Styrofoam were then manufactured to mimic phantoms and doses for 100 MUs were acquired with cylindrical ionization chamber at selected depths beyond high density heterogeneity interface. The measured and calculated depth doses were then compared. Results: AAA's values had better agreement with measurements at all measured depths. Dose overestimation by AAA (up to 5.3%) and by PBC (up to 6.7%) was found to be higher in proximity to the high-density heterogeneity interface, and the dose discrepancies were more pronounced for larger field sizes. The errors in dose estimation by AAA and PBC may be due to improper beam modeling of primary beam attenuation or lateral scatter contributions or combination of both in heterogeneous media that include low and high density materials. Conclusions: AAA is more accurate than PBC for dose calculations in treating deep-seated tumor beyond high-density heterogeneity interface. PMID:24455541

Rana, Suresh B.

2013-01-01

359

Oxygen depth profiling with subnanometre depth resolution  

NASA Astrophysics Data System (ADS)

A High-depth Resolution Elastic Recoil Detection (HR-ERD) set-up using a magnetic spectrometer has been taken into operation at the Helmholtz-Zentrum Dresden-Rossendorf for the first time. This instrument allows the investigation of light elements in ultra-thin layers and their interfaces with a depth resolution of less than 1 nm near the surface. As the depth resolution is highly influenced by the experimental measurement parameters, sophisticated optimisation procedures have been implemented. Effects of surface roughness and sample damage caused by high fluences need to be quantified for each kind of material. Also corrections are essential for non-equilibrium charge state distributions that exist very close to the surface. Using the example of a high-k multilayer SiO2/Si3N4Ox/SiO2/Si it is demonstrated that oxygen in ultra-thin films of a few nanometres thickness can be investigated by HR-ERD.

Kosmata, Marcel; Munnik, Frans; Hanf, Daniel; Grötzschel, Rainer; Crocoll, Sonja; Möller, Wolfhard

2014-10-01

360

Layered Depth Images  

Microsoft Academic Search

In this paper we present a set of efficient image based rendering methods capable of rendering multiple frames per second on a PC.The first method warps Sprites with Depth representing smooth surfaces without the gaps found in other techniques. A second method for more general scenes performswarping from an intermediate representation called a Layered Depth Image (LDI). An LDI is

Jonathan Shade; Steven J. Gortler; Li-wei He; Richard Szeliski

1998-01-01

361

Depth from diffracted rotation.  

PubMed

The accuracy of depth estimation based on defocus effects has been essentially limited by the depth of field of the imaging system. We show that depth estimation can be improved significantly relative to classical methods by exploiting three-dimensional diffraction effects. We formulate the problem by using information theory analysis and present, to the best of our knowledge, a new paradigm for depth estimation based on spatially rotating point-spread functions (PSFs). Such PSFs are fundamentally more sensitive to defocus thanks to their first-order axial variation. Our system acquires a frame by using a rotating PSF and jointly processes it with an image acquired by using a standard PSF to recover depth information. Analytical, numerical, and experimental evidence suggest that the approach is suitable for applications such as microscopy and machine vision. PMID:16441023

Greengard, Adam; Schechner, Yoav Y; Piestun, Rafael

2006-01-15

362

Monte carlo computation of the energy deposited by protons in water, bone and adipose  

NASA Astrophysics Data System (ADS)

Protons are most suitable for treating deeply-seated tumors due to their unique depth dose distribution. The maximum dose of protons is a pronounced peak, called the Bragg peak, with zero dose behind the peak. The objective of radiation therapy with protons is to deliver the dose to the target volume by using this type of distribution. This is achieved with a finite number of Bragg peaks at the depth of the target volume. The location of the peak in terms of depth depends on the energy of the protons. Simulations are used to determine the depth dose distribution of proton beams passing through tissue, so it is important that experimental data agree with the simulation data. In this study, we used the FLUKA computer code to determine the correct position of the Bragg peak for proton beams passing through water, bone and adipose, and the results were compared with experimental data.

Küçer, Rahmi; Küçer, Nermin; Türemen, Görkem

2013-02-01

363

Impact of tetrachloroethylene-contaminated drinking water on the risk of breast cancer: Using a dose model to assess exposure in a case-control study  

PubMed Central

Background A population-based case-control study was undertaken in 1997 to investigate the association between tetrachloroethylene (PCE) exposure from public drinking water and breast cancer among permanent residents of the Cape Cod region of Massachusetts. PCE, a volatile organic chemical, leached from the vinyl lining of certain water distribution pipes into drinking water from the late 1960s through the early 1980s. The measure of exposure in the original study, referred to as the relative delivered dose (RDD), was based on an amount of PCE in the tap water entering the home and estimated with a mathematical model that involved only characteristics of the distribution system. Methods In the current analysis, we constructed a personal delivered dose (PDD) model that included personal information on tap water consumption and bathing habits so that inhalation, ingestion, and dermal absorption were also considered. We reanalyzed the association between PCE and breast cancer and compared the results to the original RDD analysis of subjects with complete data. Results The PDD model produced higher adjusted odds ratios than the RDD model for exposures > 50th and >75th percentile when shorter latency periods were considered, and for exposures < 50th and >90th percentile when longer latency periods were considered. Overall, however, the results from the PDD analysis did not differ greatly from the RDD analysis. Conclusion The inputs that most heavily influenced the PDD model were initial water concentration and duration of exposure. These variables were also included in the RDD model. In this study population, personal factors like bath and shower temperature, bathing frequencies and durations, and water consumption did not differ greatly among subjects, so including this information in the model did not significantly change subjects' exposure classification. PMID:15733317

Vieira, Verónica; Aschengrau, Ann; Ozonoff, David

2005-01-01

364

The Depth of Earthquakes  

NSDL National Science Digital Library

This map of world seismicity illustrates earthquake data for the years 1991 through 1996. It is intended to provide a sense of the depth distribution of earthquakes. Plate boundaries are shown, along with diffuse regions of seismicity, such as in central Asia, and earthquake locations are color-coded to indicate the depths at which they occurred. In addition to the map, selected cross-sections of subduction zones in South America, Tonga, Japan, and the Aleutian Islands are provided. They feature a map showing the orientation of the cross-section and graphs illustrating distribution of earthquake depth versus longitude and number of earthquakes.

365

The Depth of Earthquakes  

NSDL National Science Digital Library

This map of world seismicity illustrates earthquake data for the years 1991 through 1996. It is intended to provide a sense of the depth distribution of earthquakes. Plate boundaries are shown, along with diffuse regions of seismicity, such as in central Asia, and earthquake locations are color-coded to indicate the depths at which they occurred. In addition to the map, selected cross-sections of subduction zones in South America, Tonga, Japan, and the Aleutian Islands are provided. They feature a map showing the orientation of the cross-section and graphs illustrating distribution of earthquake depth versus longitude and number of earthquakes.

2011-05-05

366

Absorbed Dose and Dose Equivalent Calculations for Modeling Effective Dose  

NASA Technical Reports Server (NTRS)

While in orbit, Astronauts are exposed to a much higher dose of ionizing radiation than when on the ground. It is important to model how shielding designs on spacecraft reduce radiation effective dose pre-flight, and determine whether or not a danger to humans is presented. However, in order to calculate effective dose, dose equivalent calculations are needed. Dose equivalent takes into account an absorbed dose of radiation and the biological effectiveness of ionizing radiation. This is important in preventing long-term, stochastic radiation effects in humans spending time in space. Monte carlo simulations run with the particle transport code FLUKA, give absorbed and equivalent dose data for relevant shielding. The shielding geometry used in the dose calculations is a layered slab design, consisting of aluminum, polyethylene, and water. Water is used to simulate the soft tissues that compose the human body. The results obtained will provide information on how the shielding performs with many thicknesses of each material in the slab. This allows them to be directly applicable to modern spacecraft shielding geometries.

Welton, Andrew; Lee, Kerry

2010-01-01

367

Depth estimation for ordinary high water of streams in the Mobile District of the U.S. Army Corps of Engineers, Alabama and adjacent states  

USGS Publications Warehouse

Drainage areas for about 1,600 surface-water sites on streams and lakes in Florida are contained in this report. The sites are generally either U.S. Geological Survey gaging stations or the mouths of gaged streas. Each site is identified by latitude and longitude, by the general stream type, and by the U.S. Geological Survey 7.5-minute topographic map on which it can be located. The gaging stations are furhter identified by a downstream order number, a county code, and a nearby city or town. In addition to drainage areas, the surface areas of lakes are shown for the elevation given on the topographic map. These data were retrieved from the Surface Water Index developed and maintained by the Hydrologic Surveillance section of the Florida District Office, U.S. Geological Survey. (USGS)

Harkins, Joe R.; Green, Mark E.

1981-01-01

368

Integral T-Shaped Phantom-Dosimeter System to Measure Transverse and Longitudinal Dose Distributions Simultaneously for Stereotactic Radiosurgery Dosimetry  

PubMed Central

A T-shaped fiber-optic phantom-dosimeter system was developed using square scintillating optical fibers, a lens system, and a CMOS image camera. Images of scintillating light were used to simultaneously measure the transverse and longitudinal distributions of absorbed dose of a 6 MV photon beam with field sizes of 1 × 1 and 3 × 3 cm2. Each optical fiber has a very small sensitive volume and the sensitive material is water equivalent. This allows the measurements of cross-beam profile as well as the percentage depth dose of small field sizes. In the case of transverse dose distribution, the measured beam profiles were gradually become uneven and the beam edge had a gentle slope with increasing depth of the PMMA phantom. In addition, the maximum dose values of longitudinal dose distribution for 6 MV photon beam with field sizes of 1 × 1 and 3 × 3 cm2 were found to be at a depth of approximately 15 mm and the percentage depth dose of both field sizes were nearly in agreement at the skin dose level. Based on the results of this study, it is anticipated that an all-in-one phantom-dosimeter can be developed to accurately measure beam profiles and dose distribution in a small irradiation fields prior to carrying out stereotactic radiosurgery. PMID:22778649

Yoo, Wook Jae; Moon, Jinsoo; Jang, Kyoung Won; Han, Ki-Tek; Shin, Sang Hun; Jeon, Dayeong; Park, Jang-Yeon; Park, Byung Gi; Lee, Bongsoo

2012-01-01

369

Dose contributions from large-angle scattered particles in therapeutic carbon beams  

SciTech Connect

In carbon therapy, doses at center of spread-out Bragg peaks depend on field size. For a small field of 5x5 cm{sup 2}, the central dose reduces to 96% of the central dose for the open field in case of 400 MeV/n carbon beam. Assuming the broad beam injected to the water phantom is made up of many pencil beams, the transverse dose distribution can be reconstructed by summing the dose distribution of the pencil beams. We estimated dose profiles of this pencil beam through measurements of dose distributions of broad uniform beams blocked half of the irradiation fields. The dose at a distance of a few cm from the edge of the irradiation field reaches up to a few percent of the central dose. From radiation quality measurements of this penumbra, the large-angle scattered particles were found to be secondary fragments which have lower LET than primary carbon beams. Carbon ions break up in beam modifying devices or in water phantom through nuclear interaction with target nuclei. The angular distributions of these fragmented nuclei are much broader than those of primary carbon particles. The transverse dose distribution of the pencil beam can be approximated by a function of the three-Gaussian form. For a simplest case of mono-energetic beam, contributions of the Gaussian components which have large mean deviations become larger as the depth in the water phantom increases.

Kusano, Yohsuke; Kanai, Tatsuaki; Kase, Yuki; Matsufuji, Naruhiro; Komori, Masataka; Kanematsu, Nobuyuki; Ito, Atsushi; Uchida, Hirohisa [Tokai University Unified Graduate School, Graduate School of Science and Technology, 1117 Kitakaname, Hiratsuka, Kanagawa, 259-1292, Japan and Accelerator Engineering Co., 2-13-1 Konakadai, Inage-ku, Chiba 263-0043 (Japan); Department of Accelerator and Medical Physics, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan, and Tokyo Institute of Technology, Interdisciplinary Graduate School of Science and Engineering, 4259 Nagatsuta-cho, Midori-ku, Yokohama-shi, Kanagawa 226-8503 (Japan); Tokyo Institute of Technology, Interdisciplinary Graduate School of Science and Engineering, 4259 Nagatsuta-cho, Midori-ku, Yokohama-shi, Kanagawa 226-8503 (Japan); Department of Accelerator and Medical Physics, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan); Department of Energy Science and Engineering, School of Engineering, Tokai University, 1117 Kitakaname, Hiratsuka, Kanagawa 259-1292 (Japan)

2007-01-15

370

The effect of administered dose of lipid-based formulations on the in vitro and in vivo performance of cinnarizine as a model poorly water-soluble drug.  

PubMed

The influence of varying the amount of lipid co-administered with the drug on drug solubilisation and absorption is poorly understood. In the current study, the effect of lipid dose on the in vitro drug distribution is compared with the in vivo absorption of cinnarizine (CZ) when formulated using long-chain triacylglyceride (LCT) and medium-chain triacylglycerides (MCT). At a fixed drug-lipid ratio, in the closed in vitro model, the drug concentrations in the aqueous phase increased and decreased for MCT and LCT, respectively, with increasing lipid dose. However, in vivo, the oral bioavailability (F%) of CZ was independent of the quantity of lipid administered for both MCT and LCT, but was higher for LCT (32.1 ± 2.3%) than for MCT (16.6 ± 2.3%). Increasing the quantity of lipid relative to the dose of CZ resulted in an increase in the oral F% when the lipid mass was increased from 125 to 250 mg, but was no greater at 500 mg lipid dose. The results confirm the limitations of the in vitro model but positively indicate that the use of the rat as a pre-clinical model for studying the bioavailability of poorly water-soluble drugs is not compromised by the mass of formulation administered. PMID:23242691

Lee, Kathy Wai Yu; Porter, Christopher J H; Boyd, Ben J

2013-02-01

371

When depth is no refuge: cumulative thermal stress increases with depth in Bocas del Toro, Panama  

NASA Astrophysics Data System (ADS)

Coral reefs are increasingly affected by high-temperature stress events and associated bleaching. Monitoring and predicting these events have largely utilized sea surface temperature data, due to the convenience of using large-scale remotely sensed satellite measurements. However, coral bleaching has been observed to vary in severity throughout the water column, and variations in coral thermal stress across depths have not yet been well investigated. In this study, in situ water temperature data from 1999 to 2011 from three depths were used to calculate thermal stress on a coral reef in Bahia Almirante, Bocas del Toro, Panama, which was compared to satellite surface temperature data and thermal stress calculations for the same area and time period from the National Oceanic and Atmospheric Administration Coral Reef Watch Satellite Bleaching Alert system. The results show similar total cumulative annual thermal stress for both the surface and depth-stratified data, but with a striking difference in the distribution of that stress among the depth strata during different high-temperature events, with the greatest thermal stress unusually recorded at the deepest measured depth during the most severe bleaching event in 2005. Temperature records indicate that a strong density-driven temperature inversion may have formed in this location in that year, contributing to the persistence and intensity of bleaching disturbance at depth. These results indicate that depth may not provide a stress refuge from high water temperature events in some situations, and in this case, the water properties at depth appear to have contributed to greater coral bleaching at depth compared to near-surface locations. This case study demonstrates the importance of incorporating depth-stratified temperature monitoring and small-scale oceanographic and hydrologic data for understanding and predicting local reef responses to elevated water temperature events.

Neal, B. P.; Condit, C.; Liu, G.; dos Santos, S.; Kahru, M.; Mitchell, B. G.; Kline, D. I.

2014-03-01

372

Evaluation of a new commercial Monte Carlo dose calculation algorithm for electron beams  

SciTech Connect

Purpose: In this report the authors present the validation of a Monte Carlo dose calculation algorithm (XiO EMC from Elekta Software) for electron beams. Methods: Calculated and measured dose distributions were compared for homogeneous water phantoms and for a 3D heterogeneous phantom meant to approximate the geometry of a trachea and spine. Comparisons of measurements and calculated data were performed using 2D and 3D gamma index dose comparison metrics. Results: Measured outputs agree with calculated values within estimated uncertainties for standard and extended SSDs for open applicators, and for cutouts, with the exception of the 17 MeV electron beam at extended SSD for cutout sizes smaller than 5 × 5 cm{sup 2}. Good agreement was obtained between calculated and experimental depth dose curves and dose profiles (minimum number of measurements that pass a 2%/2 mm agreement 2D gamma index criteria for any applicator or energy was 97%). Dose calculations in a heterogeneous phantom agree with radiochromic film measurements (>98% of pixels pass a 3 dimensional 3%/2 mm ?-criteria) provided that the steep dose gradient in the depth direction is considered. Conclusions: Clinically acceptable agreement (at the 2%/2 mm level) between the measurements and calculated data for measurements in water are obtained for this dose calculation algorithm. Radiochromic film is a useful tool to evaluate the accuracy of electron MC treatment planning systems in heterogeneous media.

Vandervoort, Eric J., E-mail: evandervoort@toh.on.ca; Cygler, Joanna E. [Department of Medical Physics, The Ottawa Hospital Cancer Centre, The University of Ottawa, Ottawa, Ontario K1H 8L6 (Canada) [Department of Medical Physics, The Ottawa Hospital Cancer Centre, The University of Ottawa, Ottawa, Ontario K1H 8L6 (Canada); The Faculty of Medicine, The University of Ottawa, Ottawa, Ontario K1H 8M5 (Canada); Department of Physics, Carleton University, Ottawa, Ontario K1S 5B6 (Canada); Tchistiakova, Ekaterina [Department of Medical Physics, The Ottawa Hospital Cancer Centre, The University of Ottawa, Ottawa, Ontario K1H 8L6 (Canada) [Department of Medical Physics, The Ottawa Hospital Cancer Centre, The University of Ottawa, Ottawa, Ontario K1H 8L6 (Canada); Department of Medical Biophysics, University of Toronto, Ontario M5G 2M9 (Canada); Heart and Stroke Foundation Centre for Stroke Recovery, Sunnybrook Research Institute, University of Toronto, Ontario M4N 3M5 (Canada); La Russa, Daniel J. [Department of Medical Physics, The Ottawa Hospital Cancer Centre, The University of Ottawa, Ottawa, Ontario K1H 8L6 (Canada) [Department of Medical Physics, The Ottawa Hospital Cancer Centre, The University of Ottawa, Ottawa, Ontario K1H 8L6 (Canada); The Faculty of Medicine, The University of Ottawa, Ottawa, Ontario K1H 8M5 (Canada)

2014-02-15

373

Derivation of a Bisphenol a Oral Reference Dose (RfD) and Drinking-Water Equivalent Concentration  

Microsoft Academic Search

Human exposure to bisphenol A (BPA) is due to that found in the diet, and BPA and its metabolites were detected at parts per billion (or less) concentrations in human urine, milk, saliva, serum, plasma, ovarian follicular fluid, and amniotic fluid. Adverse health effects in mice and rats may be induced after parenteral injection or after massive oral doses. Controlled

Calvin C. Willhite; Gwendolyn L. Ball; Clifton J. McLellan

2008-01-01

374

Absorbed dose simulations in near-surface regions using high dose rate Iridium-192 sources applied for brachytherapy  

NASA Astrophysics Data System (ADS)

Brachytherapy treatment with Iridium-192 high dose rate (HDR) sources is widely used for various tumours and it could be developed in many anatomic regions. Iridium-192 sources are inserted inside or close to the region that will be treated. Usually, the treatment is performed in prostate, gynaecological, lung, breast and oral cavity regions for a better clinical dose coverage compared with other techniques, such as, high energy photons and Cobalt-60 machines. This work will evaluate absorbed dose distributions in near-surface regions around Ir-192 HDR sources. Near-surface dose measurements are a complex task, due to the contribution of beta particles in the near-surface regions. These dose distributions should be useful for non-tumour treatments, such as keloids, and other non-intracavitary technique. For the absorbed dose distribution simulations the Monte Carlo code PENELOPE with the general code penEasy was used. Ir-192 source geometry and a Polymethylmethacrylate (PMMA) tube, for beta particles shield were modelled to yield the percentage depth dose (PDD) on a cubic water phantom. Absorbed dose simulations were realized at the central axis to yield the Ir-192 dose fall-off along central axis. The results showed that more than 99.2% of the absorbed doses (relative to the surface) are deposited in 5 cm depth but with slower rate at higher distances. Near-surface treatments with Ir-192 HDR sources yields achievable measurements and with proper clinical technique and accessories should apply as an alternative for treatment of lesions where only beta sources were used.

Moura, E. S.; Zeituni, C. A.; Sakuraba, R. K.; Gonçalves, V. D.; Cruz, J. C.; Júnior, D. K.; Souza, C. D.; Rostelato, M. E. C. M.

2014-02-01

375

The water equivalence of solid phantoms for low energy photon beams  

SciTech Connect

Purpose: To compare and evaluate the dosimetric water equivalence of several commonly used solid phantoms for low energy photon beams. Methods: A total of ten different solid phantom materials was used in the study. The PENELOPE Monte Carlo code was used to calculate depth doses and beam profiles in all the phantom materials as well as the dose to a small water voxel at the surface of the solid phantom. These doses were compared to the corresponding doses calculated in a water phantom. The primary photon beams used ranged in energy from 50 to 280 kVp. Results: A number of phantom materials had excellent agreement in dose compared to water for all the x-ray beam energies studied. RMI457 Solid Water, Virtual Water, PAGAT, A150, and Plastic Water DT all had depth doses that agreed with those in water to within 2%. For these same phantom materials, the dose changes in the water voxel at the surface of the solid phantom were within 2%, except for A150, which agreed to within 2.7%. By comparison, the largest differences in depth doses occurred for Plastic Water (-21.7%) and polystyrene (17.6%) for the 50 kVp energy photon beam and 8 cm diameter field size. Plastic Water gave the largest difference in the normalized beam profiles with differences of up to 3.5% as compared to water. Surface dose changes, due to the presence of the solid phantom acting as the backscatter material, were found to be up to 9.1% for polystyrene with significant differences also found for Plastic Water, PMMA, and RW3 phantoms. Conclusions: The following solid phantoms can be considered water equivalent and are recommended for relative dosimetry of low energy photon beams: A150, PAGAT, Plastic Water DT, RMI457 Solid Water, and Virtual Water. However, the following solid phantoms give significant differences, compared to water, in depth doses, profiles, and/or in surface doses due to backscatter changes: Plastic Water, PMMA, polystyrene, PRESAGE, and RW3.

Hill, Robin; Kuncic, Zdenka; Baldock, Clive [Institute of Medical Physics, School of Physics, University of Sydney, NSW 2006 (Australia) and Department of Radiation Oncology, Royal Prince Alfred Hospital, Camperdown NSW 2050 (Australia); Institute of Medical Physics, School of Physics, University of Sydney, NSW 2006 (Australia)

2010-08-15

376

238U, 234U, 226Ra, 210Po concentrations of bottled mineral waters in Italy and their dose contribution  

Microsoft Academic Search

Due to the importance of bottled mineral water in human diet with special regard to children in lactation period, a monitoring of natural radioactivity in some bottled mineral waters produced in Italy was performed. Gross alpha and beta activities and 226Ra, 238U, 234U, and 210Po concentrations were measured. Gross alpha and beta activities were determined by standards ISO 9696 and

D. Desideri; M. A. Meli; L. Feduzi; C. Roselli; A. Rongoni; D. Saetta

2007-01-01

377

Extreme skin depth waveguides  

E-print Network

Recently, we introduced a paradigm shift in light confinement strategy and introduced a class of extreme skin depth (e-skid) photonic structures (S. Jahani and Z. Jacob, "Transparent sub-diffraction optics: nanoscale light confinement without metal," Optica 1, 96-100 (2014)). Here, we analytically establish that figures of merit related to light confinement in dielectric waveguides are fundamentally tied to the skin depth of waves in the cladding. We contrast the propagation characteristics of the fundamental mode of e-skid waveguides and conventional waveguides to show that the decay constant in the cladding is dramatically larger in e-skid waveguides, which is the origin of sub-diffraction confinement. Finally, we propose an approach to verify the reduced skin depth in experiment using the decrease in the Goos-H\\"anchen phase shift.

Jahani, Saman

2014-01-01

378

Use of Fluka to Create Dose Calculations  

NASA Technical Reports Server (NTRS)

Monte Carlo codes provide an effective means of modeling three dimensional radiation transport; however, their use is both time- and resource-intensive. The creation of a lookup table or parameterization from Monte Carlo simulation allows users to perform calculations with Monte Carlo results without replicating lengthy calculations. FLUKA Monte Carlo transport code was used to develop lookup tables and parameterizations for data resulting from the penetration of layers of aluminum, polyethylene, and water with areal densities ranging from 0 to 100 g/cm^2. Heavy charged ion radiation including ions from Z=1 to Z=26 and from 0.1 to 10 GeV/nucleon were simulated. Dose, dose equivalent, and fluence as a function of particle identity, energy, and scattering angle were examined at various depths. Calculations were compared against well-known results and against the results of other deterministic and Monte Carlo codes. Results will be presented.

Lee, Kerry T.; Barzilla, Janet; Townsend, Lawrence; Brittingham, John

2012-01-01

379

Limitations of the TG-43 formalism for skin high-dose-rate brachytherapy dose calculations  

SciTech Connect

Purpose: In skin high-dose-rate (HDR) brachytherapy, sources are located outside, in contact with, or implanted at some depth below the skin surface. Most treatment planning systems use the TG-43 formalism, which is based on single-source dose superposition within an infinite water medium without accounting for the true geometry in which conditions for scattered radiation are altered by the presence of air. The purpose of this study is to evaluate the dosimetric limitations of the TG-43 formalism in HDR skin brachytherapy and the potential clinical impact. Methods: Dose rate distributions of typical configurations used in skin brachytherapy were obtained: a 5 cm × 5 cm superficial mould; a source inside a catheter located at the skin surface with and without backscatter bolus; and a typical interstitial implant consisting of an HDR source in a catheter located at a depth of 0.5 cm. Commercially available HDR{sup 60}Co and {sup 192}Ir sources and a hypothetical {sup 169}Yb source were considered. The Geant4 Monte Carlo radiation transport code was used to estimate dose rate distributions for the configurations considered. These results were then compared to those obtained with the TG-43 dose calculation formalism. In particular, the influence of adding bolus material over the implant was studied. Results: For a 5 cm × 5 cm{sup 192}Ir superficial mould and 0.5 cm prescription depth, dose differences in comparison to the TG-43 method were about ?3%. When the source was positioned at the skin surface, dose differences were smaller than ?1% for {sup 60}Co and {sup 192}Ir, yet ?3% for {sup 169}Yb. For the interstitial implant, dose differences at the skin surface were ?7% for {sup 60}Co, ?0.6% for {sup 192}Ir, and ?2.5% for {sup 169}Yb. Conclusions: This study indicates the following: (i) for the superficial mould, no bolus is needed; (ii) when the source is in contact with the skin surface, no bolus is needed for either {sup 60}Co and {sup 192}Ir. For lower energy radionuclides like {sup 169}Yb, bolus may be needed; and (iii) for the interstitial case, at least a 0.1 cm bolus is advised for {sup 60}Co to avoid underdosing superficial target layers. For {sup 192}Ir and {sup 169}Yb, no bolus is needed. For those cases where no bolus is needed, its use might be detrimental as the lack of radiation scatter may be beneficial to the patient, although the 2% tolerance for dose calculation accuracy recommended in the AAPM TG-56 report is not fulfilled.

Granero, Domingo, E-mail: dgranero@eresa.com [Department of Radiation Physics, ERESA, Hospital General Universitario, 46014 Valencia (Spain)] [Department of Radiation Physics, ERESA, Hospital General Universitario, 46014 Valencia (Spain); Perez-Calatayud, Jose [Radiotherapy Department, La Fe University and Polytechnic Hospital, Valencia 46026 (Spain)] [Radiotherapy Department, La Fe University and Polytechnic Hospital, Valencia 46026 (Spain); Vijande, Javier [Department of Atomic, Molecular and Nuclear Physics, University of Valencia, Burjassot 46100, Spain and IFIC (UV-CSIC), Paterna 46980 (Spain)] [Department of Atomic, Molecular and Nuclear Physics, University of Valencia, Burjassot 46100, Spain and IFIC (UV-CSIC), Paterna 46980 (Spain); Ballester, Facundo [Department of Atomic, Molecular and Nuclear Physics, University of Valencia, Burjassot 46100 (Spain)] [Department of Atomic, Molecular and Nuclear Physics, University of Valencia, Burjassot 46100 (Spain); Rivard, Mark J. [Department of Radiation Oncology, Tufts University School of Medicine, Boston, Massachusetts 02111 (United States)] [Department of Radiation Oncology, Tufts University School of Medicine, Boston, Massachusetts 02111 (United States)

2014-02-15

380

Calculate Your Radiation Dose  

MedlinePLUS

... Ionizing & Non-Ionizing Radiation Understanding Radiation: Calculate Your Radiation Dose Health Effects Main Page Exposure Pathways Calculate ... of the US do you live in? Internal radiation (in your body): From food and water, (e. ...