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Sample records for water depth dose

  1. The antiproton depth-dose curve in water.

    PubMed

    Bassler, N; Holzscheiter, M H; Jäkel, O; Knudsen, H V; Kovacevic, S

    2008-02-01

    We have measured the depth-dose curve of 126 MeV antiprotons in a water phantom using ionization chambers. Since the antiproton beam provided by CERN has a pulsed structure and possibly carries a high-LET component from the antiproton annihilation, it is necessary to correct the acquired charge for ion recombination effects. The results are compared with Monte Carlo calculations and were found to be in good agreement. Based on this agreement we calculate the antiproton depth-dose curve for antiprotons and compare it with that for protons and find a doubling of the physical dose in the peak region for antiprotons. PMID:18199915

  2. Neon-20 depth-dose relations in water

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.; Townsend, L. W.; Bidasaria, H. B.; Schimmerling, W.; Wong, M.; Howard, J.

    1984-01-01

    The dose from heavy ion beams has been calculated using a one-dimensional transport theory and evaluated for 670 MeV/amu 20 Ne beams in water. The result is presented so as to be applicable to arbitrary ions for which the necessary interaction data are known. The present evaluation is based on thar Silberg-Tsao fragmentation parameters augmented with light fragment production from intranuclear cascades, recently calculated nuclear absorption cross sections, and evaluated stopping power data. Comparison with recent experimental data obtained at the Lawrence Berkeley Laboratory reveals the need for more accurate fragmentation data.

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

    NASA Astrophysics Data System (ADS)

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

    2009-08-01

    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.

  4. Physical approach to depth dose distributions in a water phantom irradiated by a teleisotope photon beam

    SciTech Connect

    Ahuja, S.D.; Stroup, S.L.; Bolin, M.G.; Gibbs, S.J.

    1980-03-01

    The physical basis of deposition of radiation dose within a homogeneous phantom irradiated by a monoenergetic photon beam has been studied in terms of photon attenuation and energy-absorption properties of the phantom material. A semi-empirical model based on the Klein--Nishina formula for Compton scattering, and the ratio of multiply scattered to singly scattered photon fluences, has been developed for the scatter dose component within a realistic phantom to determine the central-axial percent depth dose (PDD) and off-central-axis ratios (OCR). Differences between the predicted and measured values of PDD and OCR for cobalt-60 and cesium-137 beams are less than 3% for fields of equivalent-square-side less than 20 cm, and less than 5% for larger fields. Beam profiles of all field sizes can be well simulated by this model and reasonable agreement has been found between the predicted and tabulated values of scatter functions and the backscatter factor for cobalt-60 beams. This formulation involves no variable parameters, and is valid for all values of the source-to-surface distance, field length and width, and field shape. However, the algorithm developed is not suitable for routine multiple-field treatment planning because it requires large computer memory size.

  5. Monte Carlo study of the energy response and depth dose water equivalence of the MOSkin radiation dosimeter at clinical kilovoltage photon energies.

    PubMed

    Lian, C P L; Othman, M A R; Cutajar, D; Butson, M; Guatelli, S; Rosenfeld, A B

    2011-06-01

    Skin dose is often the quantity of interest for radiological protection, as the skin is the organ that receives maximum dose during kilovoltage X-ray irradiations. The purpose of this study was to simulate the energy response and the depth dose water equivalence of the MOSkin radiation detector (Centre for Medical Radiation Physics (CMRP), University of Wollongong, Australia), a MOSFET-based radiation sensor with a novel packaging design, at clinical kilovoltage photon energies typically used for superficial/orthovoltage therapy and X-ray CT imaging. Monte Carlo simulations by means of the Geant4 toolkit were employed to investigate the energy response of the CMRP MOSkin dosimeter on the surface of the phantom, and at various depths ranging from 0 to 6 cm in a 30 × 30 × 20 cm water phantom. By varying the thickness of the tissue-equivalent packaging, and by adding thin metallic foils to the existing design, the dose enhancement effect of the MOSkin dosimeter at low photon energies was successfully quantified. For a 5 mm diameter photon source, it was found that the MOSkin was water equivalent to within 3% at shallow depths less than 15 mm. It is recommended that for depths larger than 15 mm, the appropriate depth dose water equivalent correction factors be applied to the MOSkin at the relevant depths if this detector is to be used for depth dose assessments. This study has shown that the Geant4 Monte Carlo toolkit is useful for characterising the surface energy response and depth dose behaviour of the MOSkin. PMID:21559885

  6. Depth from water reflection.

    PubMed

    Linjie Yang; Jianzhuang Liu; Xiaoou Tang

    2015-04-01

    The scene in a water reflection image often exhibits bilateral symmetry. In this paper, we design a framework to reconstruct the depth from a single water reflection image. This problem can be regarded as a special case of two-view stereo vision. It is challenging to obtain correspondences from the real scene and the mirror scene due to their large appearance difference. We first propose an appearance adaptation method to transform the appearance of the mirror scene so that it is much closer to the real scene. We then present a stereo matching algorithm to obtain the disparity map of the real scene. Compared with other depth-from-symmetry work that deals with man-made objects, our algorithm can recover the depth maps of a variety of scenes, where both natural and man-made objects may exist. PMID:25643408

  7. Controllability of depth dose distribution for neutron capture therapy at the Heavy Water Neutron Irradiation Facility of Kyoto University Research Reactor.

    PubMed

    Sakurai, Yoshinori; Kobayashi, Tooru

    2002-10-01

    The updating construction of the Heavy Water Neutron Irradiation Facility of the Kyoto University Research Reactor has been performed from November 1995 to March 1996 mainly for the improvement in neutron capture therapy. On the performance, the neutron irradiation modes with the variable energy spectra from almost pure thermal to epi-thermal neutrons became available by the control of the heavy-water thickness in the spectrum shifter and by the open-and-close of the cadmium and boral thermal neutron filters. The depth distributions of thermal, epi-thermal and fast neutron fluxes were measured by activation method using gold and indium, and the depth distributions of gamma-ray absorbed dose rate were measured using thermo-luminescent dosimeter of beryllium oxide for the several irradiation modes. From these measured data, the controllability of the depth dose distribution using the spectrum shifter and the thermal neutron filters was confirmed. PMID:12408308

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

    SciTech Connect

    Zilio, Valery Olivier; Joneja, Om Parkash; Popowski, Youri; Rosenfeld, Anatoly; Chawla, Rakesh

    2006-06-15

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

  9. Electron spectra derived from depth dose distributions.

    PubMed

    Faddegon, B A; Blevis, I

    2000-03-01

    The technique of extracting electron energy spectra from measured distributions of dose along the central axis of clinical electron beams is explored in detail. Clinical spectra measured with this simple spectroscopy tool are shown to be sufficient in accuracy and resolution for use in Monte Carlo treatment planning. A set of monoenergetic depth dose curves of appropriate energy spacing, precalculated with Monte Carlo for a simple beam model, are unfolded from the measured depth dose curve. The beam model is comprised of a point electron and photon source placed in vacuum with a source-to-surface distance of 100 cm. Systematic error introduced by this model affects the calculated depth dose curve by no more than 2%/2 mm. The component of the dose due to treatment head bremsstrahlung, subtracted prior to unfolding, is estimated from the thin-target Schiff spectrum within 0.3% of the maximum total dose (from electrons and photons) on the beam axis. Optimal unfolding parameters are chosen, based on physical principles. Unfolding is done with the public-domain code FERDO. Comparisons were made to previously published spectra measured with magnetic spectroscopy and to spectra we calculated with Monte Carlo treatment head simulation. The approach gives smooth spectra with an average resolution for the 27 beams studied of 16+/-3% of the mean peak energy. The mean peak energy of the magnetic spectrometer spectra was calculated within 2% for the AECL T20 scanning beam accelerators, 3% for the Philips SL25 scattering foil based machine. The number of low energy electrons in Monte Carlo spectra is estimated by unfolding with an accuracy of 2%, relative to the total number of electrons in the beam. Central axis depth dose curves calculated from unfolded spectra are within 0.5%/0.5 mm of measured and simulated depth dose curves, except near the practical range, where 1%/1 mm errors are evident. PMID:10757603

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

    PubMed

    Schimmack, W; Steindl, H; Bunzl, K

    1998-04-01

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

  11. Polarization lidar for shallow water depth measurement.

    PubMed

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

    2010-12-20

    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

  12. Water depth penetration film test

    NASA Technical Reports Server (NTRS)

    Lockwood, H. E.; Perry, L.; Sauer, G. E.; Lamar, N. T.

    1974-01-01

    As part of the National Aeronautics and Space Administration Earth Resources Program, a comparative and controlled evaluation of nine film-filter combinations was completed to establish the relative effectiveness in recording water subsurface detail if exposed from an aerial platform over a typical water body. The films tested, with one exception, were those which prior was suggested had potential. These included an experimental 2-layer positive color film, a 2-layer (minus blue layer) film, a normal 3-layer color film, a panchromatic black-and-white film, and a black-and-white infrared film. Selective filtration was used with all films.

  13. Water depth estimation with ERTS-1 imagery

    NASA Technical Reports Server (NTRS)

    Ross, D. S.

    1973-01-01

    Contrast-enhanced 9.5 inch ERTS-1 images were produced for an investigation on ocean water color. Such images lend themselves to water depth estimation by photographic and electronic density contouring. MSS-4 and -5 images of the Great Bahama Bank were density sliced by both methods. Correlation was found between the MSS-4 image and a hydrographic chart at 1:467,000 scale, in a number of areas corresponding to water depth of less than 2 meters, 5 to 10 meters and 10 to about 20 meters. The MSS-5 image was restricted to depths of about 2 meters. Where reflective bottom and clear water are found, ERTS-1 MSS-4 images can be used with density contouring by electronic or photographic methods for estimating depths to 5 meters within about one meter.

  14. SUPERFUND GROUND WATER ISSUE - ACCURACY OF DEPTH TO WATER MEASUREMENTS

    EPA Science Inventory

    Accuracy of depth to water measurements is an issue identified by the Forum as a concern of Superfund decision-makers as they attempt to determine directions of ground-water flow, areas of recharge of discharge, the hydraulic characteristics of aquifers, or the effects of manmade...

  15. Depth-dose relations for heavy ion beams

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.

    1977-01-01

    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.

  16. Anchoring International sets new water depth record

    SciTech Connect

    Noble, H.J.

    1983-07-01

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

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

    USGS Publications Warehouse

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

    2007-01-01

    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.

  18. Percentage depth dose evaluation in heterogeneous media using thermoluminescent dosimetry.

    PubMed

    da Rosa, L A R; Cardoso, S C; Campos, L T; Alves, V G L; Batista, D V S; Facure, A

    2010-01-01

    The purpose of this study is to investigate the influence of lung heterogeneity inside a soft tissue phantom on percentage depth dose (PDD). PDD curves were obtained experimentally using LiF:Mg,Ti (TLD-100) thermoluminescent detectors and applying Eclipse treatment planning system algorithms Batho, modified Batho (M-Batho or BMod), equivalent TAR (E-TAR or EQTAR), and anisotropic analytical algorithm (AAA) for a 15 MV photon beam and field sizes of 1 x 1, 2 x 2, 5 x 5, and 10 x 10 cm 2 . Monte Carlo simulations were performed using the DOSRZnrc user code of EGSnrc. The experimental results agree with Monte Carlo simulations for all irradiation field sizes. Comparisons with Monte Carlo calculations show that the AAA algorithm provides the best simulations of PDD curves for all field sizes investigated. However, even this algorithm cannot accurately predict PDD values in the lung for field sizes of 1 x 1 and 2 x 2 cm 2 . An overdosage in the lung of about 40% and 20% is calculated by the AAA algorithm close to the interface soft tissue/lung for 1 x 1 and 2 x 2 cm 2 field sizes, respectively. It was demonstrated that differences of 100% between Monte Carlo results and the algorithms Batho, modified Batho, and equivalent TAR responses may exist inside the lung region for the 1 x 1 cm 2 field. PMID:20160687

  19. Orthovoltage radiation of normal canine nasal passages: assessment of depth dose

    SciTech Connect

    Feeney, D.A.; Johnston, G.R.; Williamson, J.F.; Jessen, C.R.

    1983-08-01

    Frozen heads of 9 clinically normal dogs were irradiated with orthovoltage x-rays. Surface doses and nasal cavity depth doses were measured, and the percentage of surface dose (depth dose) was calculated at random depths from the dorsal cutaneous surface in transverse planes through the medial and lateral canthi. Depth dose of 2 orthovoltage x-ray beams having half-value layers of 1.5 mm of Cu (96 keV) and 2.6 mm of Cu (134 keV) were compared with and found to resemble that reported in depth dose tables based on soft tissue equivalent material. Any differences (identified graphically) in depth dose, compared with that described using a uniform (soft tissue equivalent) phantom, were explained by the variations in tissue composition and the presence of air within the normal nasal and paranasal cavities.

  20. Measurement of depth-dose of linear accelerator and simulation by use of Geant4 computer code

    PubMed Central

    Sardari, D.; Maleki, R.; Samavat, H.; Esmaeeli, A.

    2010-01-01

    Radiation therapy is an established method of cancer treatment. New technologies in cancer radiotherapy need a more accurate computation of the dose delivered in the radiotherapy treatment plan. This study presents some results of a Geant4-based application for simulation of the absorbed dose distribution given by a medical linear accelerator (LINAC). The LINAC geometry is accurately described in the Monte Carlo code with use of the accelerator manufacturer's specifications. The capability of the software for evaluating the dose distribution has been verified by comparisons with measurements in a water phantom; the comparisons were performed for percentage depth dose (PDD) and profiles for various field sizes and depths, for a 6-MV electron beam. Experimental and calculated dose values were in good agreement both in PDD and in transverse sections of the water phantom. PMID:24376926

  1. Statistical classification of vegetation and water depths in montane wetlands

    USGS Publications Warehouse

    Sharp, Julia L.; Sodja, Richard S.; Greenwood, Mark; Rosenberry, Donald O.; Warren, Jeffrey M.

    2013-01-01

    Relationships between water depths and density of submergent vegetation were studied in montane wetlands using statistical techniques based on clustering and an extension of regression trees. Sago pondweed (Stuckenia pectinata) was associated with lower average water depths than water milfoil (Myriophyllum sibiricum). We detected a nonlinear relationship when average water depths were used to predict percent cover in S. pectinata, with depths of 30–40 cm, producing the highest predicted average percent cover of S. pectinata; higher and lower depths resulted in lower percent cover predictions. For M. sibiricum, higher water depths were monotonically associated with higher average percent cover. To foster more S. pectinata and less M. sibiricum, managers might employ water control structures to reduce water depths below 1 m, using both temporary drawdowns and average depths of 30–40 cm. Other species responded less markedly to water depth variation. Should decreased water depths become more common, these results suggest an increase in S. pectinata and a decrease in M. sibiricum.

  2. Photometric and polarimetric mapping of water turbidity and water depth

    NASA Technical Reports Server (NTRS)

    Halajian, J.; Hallock, H.

    1973-01-01

    A Digital Photometric Mapper (DPM) was used in the Fall of 1971 in an airborne survey of New York and Boston area waters to acquire photometric, spectral and polarimetric data. The object of this study is to analyze these data with quantitative computer processing techniques to assess the potential of the DPM in the measurement and regional mapping of water turbidity and depth. These techniques have been developed and an operational potential has been demonstrated. More emphasis is placed at this time on the methodology of data acquisition, analysis and display than on the quantity of data. The results illustrate the type, quantity and format of information that could be generated operationally with the DPM-type sensor characterized by high photometric stability and fast, accurate digital output. The prototype, single-channel DPM is suggested as a unique research tool for a number of new applications. For the operational mapping of water turbidity and depth, the merits of a multichannel DPM coupled with a laser system are stressed.

  3. Evaluation of detectors for acquisition of pristine depth-dose curves in pencil beam scanning.

    PubMed

    Bäumer, Christian; Koska, Benjamin; Lambert, Jamil; Timmermann, Beate; Mertens, Thierry; Takoukam Talla, Patrick

    2015-01-01

    Acquisition of quasi-monoenergetic ("pristine") depth-dose curves is an essential task in the frame of commissioning and quality assurance of a proton therapy treatment head. For pencil beam scanning delivery modes this is often accomplished by measuring the integral ionization in a plane perpendicular to the axis of an unscanned beam. We focus on the evaluation of three integral detectors: two of them are plane-parallel ionization chambers with an effective radius of 4.1 cm and 6.0 cm, respectively, mounted in a scanning water phantom. The third integral detector is a 6.0 cm radius multilayer ionization chamber. The experimental results are compared with the corresponding measurements under broad field conditions, which are performed with a small radius plane-parallel chamber and a small radius multilayer ionization chamber. We study how a measured depth-dose curve of a pristine proton field depends on the detection device, by evaluating the shape of the depth-dose curve, the relative charge collection efficiency, and intercomparing measured ranges. Our results show that increasing the radius of an integral chamber from 4.1 cm to 6.0 cm increases the collection efficiency by 0%-3.5% depending on beam energy and depth. Ranges can be determined by the large electrode multilayer ionization chamber with a typical uncertainty of 0.4 mm on a routine basis. The large electrode multilayer ionization chamber exhibits a small distortion in the Bragg Peak region. This prohibits its use for acquisition of base data, but is tolerable for quality assurance. The good range accuracy and the peak distortion are characteristics of the multilayer ionization chamber design, as shown by the direct comparison with the small electrode counterpart. PMID:26699567

  4. Improvement of depth dose distribution using multiple-field irradiation in boron neutron capture therapy.

    PubMed

    Fujimoto, N; Tanaka, H; Sakurai, Y; Takata, T; Kondo, N; Narabayashi, M; Nakagawa, Y; Watanabe, T; Kinashi, Y; Masunaga, S; Maruhashi, A; Ono, K; Suzuki, M

    2015-12-01

    It is important that improvements are made to depth dose distribution in boron neutron capture therapy, because the neutrons do not reach the innermost regions of the human body. Here, we evaluated the dose distribution obtained using multiple-field irradiation in simulation. From a dose volume histogram analysis, it was found that the mean and minimum tumor doses were increased using two-field irradiation, because of improved dose distribution for deeper-sited tumors. PMID:26282566

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

    PubMed

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

    2015-01-01

    In treatment planning of charged-particle therapy, tissue heterogeneity is conventionally modeled as water with various densities, i.e. stopping effective densities ρ(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, ρ(S) of the patient is converted to nuclear effective density ρ(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 Φ(w)(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 ρ(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 Φ(w)(p), and corrected that from lighter fragments as inversely proportional to Φ(w)(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

  6. X-ray depth-dose characteristics of the Toshiba LMR-16.

    PubMed

    Mantel, J; Perry, H; Weinkam, J J

    1979-01-01

    The depth-dose characteristics of the Toshiba LMR-16 linear accelerator for 14-MeV x rays have been measured at an SSD of 100 cm using diodes and ion chambers. The surface dose and build-up depth both exhibit a considerable variation with field size. A new central axis model has been developed which takes account of these variations, and the agreement between the measured and computed data using this model is found to be excellent. Formulas are also presented to estimate the surface dose, buildup depth, and output factor as a function of field size. PMID:460069

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

    SciTech Connect

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

    1986-02-01

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

  8. Possibility of using cylindrical ionization chambers for percent depth-dose measurements in clinical electron beams

    SciTech Connect

    Ono, Takeshi; Araki, Fujio; Yoshiyama, Fumiaki

    2011-08-15

    Purpose: This study investigated the possibility of using cylindrical ionization chambers for percent depth-dose (PDD) measurements in high-energy clinical electron beams. Methods: The cavity correction factor, P{sub cav}, for cylindrical chambers with various diameters was calculated as a function of depth from the surface to R{sub 50}, in the energy range of 6-18 MeV electrons with the EGSnrc C ++ -based user-code CAVITY. The results were compared with those for IBA NACP-02 and PTW Roos parallel-plate ionization chambers. The effective point of measurement (EPOM) for the cylindrical chamber and the parallel-plate chamber was positioned according to the IAEA TRS-398 code of practice. The overall correction factor, P{sub Q}, and the percent depth-ionization (PDI) curve for a PTW30013 Farmer-type chamber were also compared with those of NACP-02 and Roos chambers. Results: The P{sub cav} values at depths between the surface and R{sub 50} for cylindrical chambers were all lower than those with parallel-plate chambers. However, the variation in depth for cylindrical chambers equal to or less than 4 mm in diameter was equivalent to or smaller than that for parallel-plate chambers. The P{sub Q} values for the PTW30013 chamber mainly depended on P{sub cav}, and for parallel-plate chambers depended on the wall correction factor, P{sub wall}, rather than P{sub cav}. P{sub Q} at depths from the surface to R{sub 50} for the PTW30013 chamber was consequently a lower value than that with parallel-plate chambers. However, the variation in depth was equivalent to that of parallel-plate chambers at electron energies equal to or greater than 9 MeV. The shift to match calculated PDI curves for the PTW30013 chamber and water (perturbation free) varied from 0.65 to 0 mm between 6 and 18 MeV beams. Similarly, the shifts for NACP-02 and Roos chambers were 0.5-0.6 mm and 0.2-0.3 mm, respectively, and were nearly independent of electron energy. Conclusions: Calculated PDI curves for PTW

  9. A depth-dependent formula for shallow water propagation.

    PubMed

    Sertlek, Hüseyin Özkan; Ainslie, Michael A

    2014-08-01

    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

  10. Development of a fibre-optic dosemeter to measure the skin dose and percentage depth dose in the build-up region of therapeutic photon beams.

    PubMed

    Kim, K-A; Yoo, W J; Jang, K W; Moon, J; Han, K-T; Jeon, D; Park, J-Y; Cha, E-J; Lee, B

    2013-03-01

    In this study, a fibre-optic dosemeter (FOD) using an organic scintillator with a diameter of 0.5 mm for photon-beam therapy dosimetry was fabricated. The fabricated dosemeter has many advantages, including water equivalence, high spatial resolution, remote sensing and real-time measurement. The scintillating light generated from an organic-dosemeter probe embedded in a solid-water stack phantom is guided to a photomultiplier tube and an electrometer via 20 m of plastic optical fibre. Using this FOD, the skin dose and the percentage depth dose in the build-up region according to the depths of a solid-water stack phantom are measured with 6- and 15-MV photon-beam energies with field sizes of 10 × 10 and 20 × 20 cm(2), respectively. The results are compared with those measured using conventional dosimetry films. It is expected that the proposed FOD can be effectively used in radiotherapy dosimetry for accurate measurement of the skin dose and the depth dose distribution in the build-up region due to its high spatial resolution. PMID:22764176

  11. Degradation of proton depth dose distributions attributable to microstructures in lung-equivalent material

    SciTech Connect

    Titt, Uwe Mirkovic, Dragan; Mohan, Radhe; Sell, Martin; Unkelbach, Jan; Bangert, Mark; Oelfke, Uwe

    2015-11-15

    Purpose: The purpose of the work reported here was to investigate the influence of sub-millimeter size heterogeneities on the degradation of the distal edges of proton beams and to validate Monte Carlo (MC) methods’ ability to correctly predict such degradation. Methods: A custom-designed high-resolution plastic phantom approximating highly heterogeneous, lung-like structures was employed in measurements and in Monte Carlo simulations to evaluate the degradation of proton Bragg curves penetrating heterogeneous media. Results: Significant differences in distal falloff widths and in peak dose values were observed in the measured and the Monte Carlo simulated curves compared to pristine proton Bragg curves. Furthermore, differences between simulations of beams penetrating CT images of the phantom did not agree well with the corresponding experimental differences. The distal falloff widths in CT image-based geometries were underestimated by up to 0.2 cm in water (corresponding to 0.8–1.4 cm in lung tissue), and the peak dose values of pristine proton beams were overestimated by as much as ~35% compared to measured curves or depth-dose curves simulated on the basis of true geometry. The authors demonstrate that these discrepancies were caused by the limited spatial resolution of CT images that served as a basis for dose calculations and lead to underestimation of the impact of the fine structure of tissue heterogeneities. A convolution model was successfully applied to mitigate the underestimation. Conclusions: The results of this study justify further development of models to better represent heterogeneity effects in soft-tissue geometries, such as lung, and to correct systematic underestimation of the degradation of the distal edge of proton doses.

  12. Degradation of proton depth dose distributions attributable to microstructures in lung-equivalent material

    PubMed Central

    Titt, Uwe; Sell, Martin; Unkelbach, Jan; Bangert, Mark; Mirkovic, Dragan; Oelfke, Uwe; Mohan, Radhe

    2015-01-01

    Purpose: The purpose of the work reported here was to investigate the influence of sub-millimeter size heterogeneities on the degradation of the distal edges of proton beams and to validate Monte Carlo (MC) methods’ ability to correctly predict such degradation. Methods: A custom-designed high-resolution plastic phantom approximating highly heterogeneous, lung-like structures was employed in measurements and in Monte Carlo simulations to evaluate the degradation of proton Bragg curves penetrating heterogeneous media. Results: Significant differences in distal falloff widths and in peak dose values were observed in the measured and the Monte Carlo simulated curves compared to pristine proton Bragg curves. Furthermore, differences between simulations of beams penetrating CT images of the phantom did not agree well with the corresponding experimental differences. The distal falloff widths in CT image-based geometries were underestimated by up to 0.2 cm in water (corresponding to 0.8–1.4 cm in lung tissue), and the peak dose values of pristine proton beams were overestimated by as much as ˜35% compared to measured curves or depth-dose curves simulated on the basis of true geometry. The authors demonstrate that these discrepancies were caused by the limited spatial resolution of CT images that served as a basis for dose calculations and lead to underestimation of the impact of the fine structure of tissue heterogeneities. A convolution model was successfully applied to mitigate the underestimation. Conclusions: The results of this study justify further development of models to better represent heterogeneity effects in soft-tissue geometries, such as lung, and to correct systematic underestimation of the degradation of the distal edge of proton doses. PMID:26520732

  13. SU-E-T-561: Development of Depth Dose Measurement Technique Using the Multilayer Ionization Chamber for Spot Scanning Method

    SciTech Connect

    Takayanagi, T; Fujitaka, S; Umezawa, M; Ito, Y; Nakashima, C; Matsuda, K

    2014-06-01

    Purpose: To develop a measurement technique which suppresses the difference between profiles obtained with a multilayer ionization chamber (MLIC) and with a water phantom. Methods: The developed technique multiplies the raw MLIC data by a correction factor that depends on the initial beam range and water equivalent depth. The correction factor is derived based on a Bragg curve calculation formula considering range straggling and fluence loss caused by nuclear reactions. Furthermore, the correction factor is adjusted based on several integrated depth doses measured with a water phantom and the MLIC. The measured depth dose profiles along the central axis of the proton field with a nominal field size of 10 by 10 cm were compared between the MLIC using the new technique and the water phantom. The spread out Bragg peak was 20 cm for fields with a range of 30.6 cm and 6.9 cm. Raw MLIC data were obtained with each energy layer, and integrated after multiplying by the correction factor. The measurements were performed by a spot scanning nozzle at Nagoya Proton Therapy Center, Japan. Results: The profile measured with the MLIC using the new technique is consistent with that of the water phantom. Moreover, 97% of the points passed the 1% dose /1mm distance agreement criterion of the gamma index. Conclusion: We have demonstrated that the new technique suppresses the difference between profiles obtained with the MLIC and with the water phantom. It was concluded that this technique is useful for depth dose measurement in proton spot scanning method.

  14. Determination of half-dose depth in skin for soft x-rays

    SciTech Connect

    Harley, N.H.; Kolber, A.B.; Altman, S.M.; Gladstein, A.H.; Buchanan, S.; Marx, J.; Grisewood, E.; Kopf, A.

    1982-09-01

    Unlike superficial x-rays, the soft x-rays normally used in dermatologic practice spare unaffected underlying organs during treatment of cutaneous malignancies. However, since the dose with depth from soft x-rays varies markedly, it is important to know this relationship for optimal therapeutic results. The peak kilovoltage, and thus the energy of the beam, is generally selected so that the dose to the base of the lesion is one-half the surface dose. An absorbed dose of 3,400 rads to the surface and a dose of about one-half this amount to the base of most malignant lesions is one standard protocol for optimal therapeutic results. An accurate value of half-depth dose in skin is therefore necessary and is readily obtained from ordinary half-value layer measurements using the technic described.

  15. 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...

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

    PubMed

    Ma, C-M; Li, Jinsheng

    2011-05-21

    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. PMID:21508447

  17. Depth

    PubMed Central

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

    2011-01-01

    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

  18. [Effect of water depths on hydraulic performance of pond wetlands].

    PubMed

    Guo, Chang-Qiang; Dong, Bin; Liu, Jun-Jie; Liu, Chun-Guo; Feng, Da-Peng; Liu, Fang-Ping

    2014-11-01

    Pond wetlands have been widely used in the treatment of drainage water from paddy fields. However, wetland hydraulic performance and purification effects are affected by many factors, such as water depth, flow rate, aspect ratio and vegetation distribution, and the better understanding of these factors would be helpful to improve the quality of wetland design, operation and management. This paper analyzed the effect of three different water depths (20, 40 and 60 cm) on the hydraulic performance of pond wetland through the dye tracer experiments with Rhodamine WT. The hydraulic indices, i. e., effective volume ratio, nominal serial complete mixing tanks (N), hydraulic efficiency (λ), were selected for analysis through the hydraulic residence time distribution (RTD) curve. The results showed that the effective volume rate rose from 0.421 to 0.844 and the hydraulic efficiency from 0.281 to 0.604 when the water depth declined from 60 cm to 20 cm. This indicated that the wetland hydraulic performance improved as the water depth decreased. In addition, the hydraulic performance of the first half of the wetland was significantly better than that of the second half. The flow regime of the first half approached complete mixing because of the mixing index (N) approaching 1 and its effective volume rate was above 0.9 when the water depth was relatively low (20 and 40 cm). The normalized RTD curves demonstrated a good agreement between moment analysis parameters and hydraulic parameters, and a great consistency between the hydraulic parameters and moment index which was not affected by tail truncation error. The experimental study concluded that a lower water depth was favorable to improve the hydraulic performance of pond wetlands. PMID:25898628

  19. Linking carbon and nitrogen metabolism to depth distribution of submersed macrophytes using high ammonium dosing tests and a lake survey

    PubMed Central

    Yuan, Guixiang; Cao, Te; Fu, Hui; Ni, Leyi; Zhang, Xiaolin; Li, Wei; Song, Xin; Xie, Ping; Jeppesen, Erik

    2013-01-01

    Strategies of carbon (C) and nitrogen (N) utilisation are among the factors determining plant distribution. It has been argued that submersed macrophytes adapted to lower light environments are more efficient in maintaining C metabolic homeostasis due to their conservative C strategy and ability to balance C shortage. We studied how depth distributions of 12 submersed macrophytes in Lake Erhai, China, were linked to their C-N metabolic strategies when facing acute dosing. dosing changed C-N metabolism significantly by decreasing the soluble carbohydrate (SC) content and increasing the -N and free amino acid (FAA) content of plant tissues.The proportional changes in SC contents in the leaves and FAA contents in the stems induced by dosing were closely correlated (positive for SC and negative for FAA) with the colonising water depths of the plants in Lake Erhai, the plants adapted to lower light regimes being more efficient in maintaining SC and FAA homeostasis.These results indicate that conservative carbohydrate metabolism of submersed macrophytes allowed the plants to colonise greater water depths in eutrophic lakes, where low light availability in the water column diminishes carbohydrate production by the plants. PMID:25810562

  20. Mapping water table depth using geophysical and environmental variables.

    PubMed

    Buchanan, S; Triantafilis, J

    2009-01-01

    Despite its importance, accurate representation of the spatial distribution of water table depth remains one of the greatest deficiencies in many hydrological investigations. Historically, both inverse distance weighting (IDW) and ordinary kriging (OK) have been used to interpolate depths. These methods, however, have major limitations: namely they require large numbers of measurements to represent the spatial variability of water table depth and they do not represent the variation between measurement points. We address this issue by assessing the benefits of using stepwise multiple linear regression (MLR) with three different ancillary data sets to predict the water table depth at 100-m intervals. The ancillary data sets used are Electromagnetic (EM34 and EM38), gamma radiometric: potassium (K), uranium (eU), thorium (eTh), total count (TC), and morphometric data. Results show that MLR offers significant precision and accuracy benefits over OK and IDW. Inclusion of the morphometric data set yielded the greatest (16%) improvement in prediction accuracy compared with IDW, followed by the electromagnetic data set (5%). Use of the gamma radiometric data set showed no improvement. The greatest improvement, however, resulted when all data sets were combined (37% increase in prediction accuracy over IDW). Significantly, however, the use of MLR also allows for prediction in variations in water table depth between measurement points, which is crucial for land management. PMID:18793206

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

    SciTech Connect

    Li Shidong . E-mail: sli1@hfhs.org; Aref, Ibrahim; Walker, Eleanor; Movsas, Benjamin

    2007-03-15

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

  2. A holistic water depth simulation model for small ponds

    NASA Astrophysics Data System (ADS)

    Ali, Shakir; Ghosh, Narayan C.; Mishra, P. K.; Singh, R. K.

    2015-10-01

    Estimation of time varying water depth and time to empty of a pond is prerequisite for comprehensive and coordinated planning of water resource for its effective utilization. A holistic water depth simulation (HWDS) and time to empty (TE) model for small, shallow ephemeral ponds have been derived by employing the generalized model based on the Green-Ampt equation in the basic water balance equation. The HWDS model includes time varying rainfall, runoff, surface water evaporation, outflow and advancement of wetting front length as external inputs. The TE model includes two external inputs; surface water evaporation and advancement of wetting front length. Both the models also consider saturated hydraulic conductivity and fillable porosity of the pond's bed material as their parameters. The solution of the HWDS model involved numerical iteration in successive time intervals. The HWDS model has successfully evaluated with 3 years of field data from two small ponds located within a watershed in a semi-arid region in western India. The HWDS model simulated time varying water depth in the ponds with high accuracy as shown by correlation coefficient (R2 ⩾ 0.9765), index of agreement (d ⩾ 0.9878), root mean square errors (RMSE ⩽ 0.20 m) and percent bias (PB ⩽ 6.23%) for the pooled data sets of the measured and simulated water depth. The statistical F and t-tests also confirmed the reliability of the HWDS model at probability level, p ⩽ 0.0001. The response of the TE model showed its ability to estimate the time to empty the ponds. An additional field calibration and validation of the HWDS and TE models with observed field data in varied hydro-climatic conditions could be conducted to increase the applicability and credibility of the models.

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

    NASA Astrophysics Data System (ADS)

    Matsumoto, T.

    2007-09-01

    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.

  4. Water depth measurement using an airborne pulsed neon laser system

    SciTech Connect

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

    1980-03-15

    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 taken at the same time as the air craft overflights to aid in determining the system's operational performance. Beam attenuation coefficient and depth d product d was established early in the program as the performance criterion index. A performance product of 6 was determined to be the goal. This performance goal was successfully met or exceeded in the large number of field tests executed. Included are selected data from nadir-angle tests conducted at 0, 5, 10, and 15. Field-of-view data chosen from the 2-, 5-, 10-, and 20-mrad tests are also presented. Depth measurements obtained to altitudes of 456 m are given for additional comparison. This laser bathymetry system represents a significant improvement over prior models in that (1) the complete surface-to-bottom pulse waveform is digitally recorded on magnetic tape at a rate of 400 pulse waveforms/sec, and (2) wide-swath mapping data may be routinely acquired using the 30 full-angle conical scanner. Space does not allow all the 5,000,000 laser soundings to be included. Qualified interested users may obtain complete data sets for their own in-depth analysis. 15 references, 9 figures, 1 table.

  5. Absorption depth profile of water on thermoplastic starch films

    SciTech Connect

    Bonno, B.; Laporte, J.L.; Paris, D.; D'Leon, R.T.

    2000-01-01

    It is well known that petroleum derived polymers are primary environmental contaminants. The study of new packing biodegradable materials has been the object of numerous papers in past years. Some of these new materials are the thermoplastic films derived from wheat starch. In the present paper, the authors study some of properties of wheat starch thermoplastic films, with various amounts of absorbed water, using photoacoustic spectroscopy techniques. The absorption depth profile of water in the starch substrate is determined for samples having a variable water level.

  6. Adsorption depth profile of water on thermoplastic starch films

    SciTech Connect

    Bonno, B.; Laporte, J.L.; Paris, D.; D'Leon, R.T.

    2000-01-01

    It is well known that petroleum derived polymers are primary environmental contaminants. The study of new packing biodegradable materials has been the object of numerous papers in past years. Some of these new materials are the thermoplastic films derived from wheat starch. In the present paper, the authors study some of properties of wheat starch thermoplastic films, with various amounts of absorbed water, using photoacoustic spectroscopy techniques. The absorption depth profile of water in the starch substrate is determined for samples having a variable water level.

  7. Deglacial Evolution of Atlantic Mid-Depth and Intermediate-Depth Water Variability

    NASA Astrophysics Data System (ADS)

    Oppo, D.; Gebbie, G.; Huang, K. F.; Guo, W.; Schmittner, A.; Liu, Z.; Curry, W. B.

    2014-12-01

    Deglacial variations in the Atlantic Meridional Overturning Circulation (AMOC) feature prominently in hypotheses of deglacial climate variability and atmospheric CO2rise. However, there is lingering uncertainty in the glacial deepwater mass configuration (e.g. Gebbie, 2014) and deglacial AMOC variability is even more poorly understood. For example, the deglacial evolution of the contribution of northern and southern source waters to the middle and intermediate depths of the Atlantic is still vigorously debated. Here, we evaluate the evolution of subsurface Atlantic ventilation, emphasizing middle and intermediate depths, by comparing new and published records of water mass variability to output from transient model simulations designed to provide insight into the climatic and oceanographic effects of a dramatic reduction in the AMOC, such as apparently occurred during Heinrich Stadial 1 (Liu et al., 2009; Schmittner and Lund, 2014). Gebbie, G. (2014), How much did Glacial North Atlantic Water shoal? Paleoceanography, 29, 190-209, doi: 10.1002/2013PA002557. Liu, Z., B. Otto-Bliesner, F. He, E. Brady, R. Thomas, P. U. Clark, A. E. Carlson, J. Lynch-Stieglitz, W. Curry, E. Brook, D. Erickson, R. Jacob, J. Kutzbach, J., and J. Chen (2009), Transient climate simulation of last deglaciation with a new mechanism for Bølling-Allerød warming, Science, 325, 310-314. Schmittner, A., and Lund, D. C. (submitted), Carbon Isotopes Support Atlantic Meridional Overturning Circulation Decline as a Trigger for Early Deglacial CO2 rise Climate of the Past Discussions.

  8. A comparison of depth dependence of dose and linear energy transfer spectra in aluminum and polyethylene

    NASA Technical Reports Server (NTRS)

    Badhwar, G. D.; Cucinotta, F. A.

    2000-01-01

    A set of four tissue-equivalent proportional counters (TEPCs), with their detector heads at the centers of 0 (bare), 3, 7 and 9-inch-diameter aluminum spheres, were flown on Shuttle flight STS-89. Five such detectors at the centers of polyethylene spheres were flown 1 year earlier on STS-81. The results of dose-depth dependence for the two materials convincingly show the merits of using material rich in hydrogen to decrease the radiation exposure to the crew. A comparison of the calculated galactic cosmic radiation (GCR) absorbed dose and dose-equivalent rates using the radiation transport code HZETRN with nuclear fragmentation model NUCFRG2 and the measured GCR absorbed dose rates and dose-equivalent rates shows that they agree within root mean square (rms) error of 12.5 and 8.2%, respectively. However, there are significant depth-dependent differences in the linear energy transfer (LET) spectra. A comparison for trapped protons using the proton transport code BRYNTRN and the AP-8 MIN trapped-proton model shows a systematic bias, with the model underpredicting dose and dose-equivalent rates. These results show the need for improvements in the radiation transport and/or fragmentation models.

  9. Water depth measurement using an airborne pulsed neon laser system

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

    The paper presents the water depth measurement using an airborne pulsed neon laser system. The results of initial base-line field test results of NASA airborne oceanographic lidar in the bathymetry mode are given, with water-truth measurements of depth and beam attenuation coefficients by boat taken at the same time as overflights to aid in determining the system's operational performance. The nadir-angle tests and field-of-view data are presented; this laser bathymetry system is an improvement over prior models in that (1) the surface-to-bottom pulse waveform is digitally recorded on magnetic tape, and (2) wide-swath mapping data may be routinely acquired using a 30 deg full-angle conical scanner.

  10. Water-depth dependent infiltration into burnt forest soils

    NASA Astrophysics Data System (ADS)

    Langhans, Christoph; Sheridan, Gary; Noske, Phil; Metzen, Daniel; Lane, Patrick

    2014-05-01

    Infiltration into severely burnt forest soils in South Eastern Australia exhibits a behaviour that is at odds with traditional infiltration theories that assumes a coherent soil matrix, which has important implications for upscaling from plot to hillslope. Infiltration patterns were studied at three severely burnt sites with different soils by applying a blue dye solution during rainfall and runon experiments, and subsequent profile excavation. Rainfall and runon rates were varied on each plot, runoff measured, and orthogonal photos taken during quasi-steady states. From transects on these photos average inundation fractions of the surface were measured, and 1.5 mm horizontal resolution DEMs were generated with image-based software. This information was combined in a DEM inundation algorithm that calculated water depth maps for each plot and rainfall and runon rate. At all three sites, nearly 100% of infiltration occurred through macropores that bypass the matrix of a water repellent layer. Average fractions of subsoil dye staining were 3% in shallow soils with a northerly aspect and low trees, 60% in deep soils with southerly aspects and high trees, and 20% in an intermediate soil. This was consistent with runoff coefficients of 0.94 for the shallow soil, 0.08 for the deep soil, and 0.71 for the intermediate soil. Irrespective of the runoff coefficient or dyed fraction there was a positive relationship between average water depth and infiltration rates on a given plot. Functions of water depth vs. bypass infiltration were derived inversely for each plot by matching average infiltration rates with the rates derived from sampling the water depth distributions. Additionally, characteristic bypass infiltration rates for all sites as function of runon and rainfall intensity were derived, normalized by the maximum infiltration rate at full inundation. These infiltration functions represent the water depth-dependent dynamics of runoff generation in bypass infiltration

  11. Fractal behavior of soil water storage at multiple depths

    NASA Astrophysics Data System (ADS)

    Ji, Wenjun; Lin, Mi; Biswas, Asim; Si, Bing C.; Chau, Henry W.; Cresswell, Hamish P.

    2016-08-01

    Spatiotemporal behavior of soil water is essential to understand the science of hydrodynamics. Data intensive measurement of surface soil water using remote sensing has established that the spatial variability of soil water can be described using the principle of self-similarity (scaling properties) or fractal theory. This information can be used in determining land management practices provided the surface scaling properties are kept at deep layers. The current study examined the scaling properties of sub-surface soil water and their relationship to surface soil water, thereby serving as supporting information for plant root and vadose zone models. Soil water storage (SWS) down to 1.4 m depth at seven equal intervals was measured along a transect of 576 m for 5 years in Saskatchewan. The surface SWS showed multifractal nature only during the wet period (from snowmelt until mid- to late June) indicating the need for multiple scaling indices in transferring soil water variability information over multiple scales. However, with increasing depth, the SWS became monofractal in nature indicating the need for a single scaling index to upscale/downscale soil water variability information. In contrast, all soil layers during the dry period (from late June to the end of the growing season in early November) were monofractal in nature, probably resulting from the high evapotranspirative demand of the growing vegetation that surpassed other effects. This strong similarity between the scaling properties at the surface layer and deep layers provides the possibility of inferring about the whole profile soil water dynamics using the scaling properties of the easy-to-measure surface SWS data.

  12. SU-E-T-443: Developmental Technique for Proton Pencil Beam Measurements: Depth Dose

    SciTech Connect

    Arjomandy, B; Lee, T; Schultz, T; Hsi, W; Park, S

    2014-06-01

    Purpose: Measurements of depth dose distribution (DDD) of pencil beam in proton therapy can be challenging and time consuming. We have developed a technique that uses two Bragg peak chambers to expedite these measurements with a high accuracy. Methods and Material: We used a PTW water tank and two PTW 10.5 cm3 Bragg peak chambers; one as a field chamber and the other as a reference chamber to measure DDDs for 100–250 MeV proton pencil beams. The reference chamber was positioned outside of the water tank upstream with respect to field chamber. We used Geant4 Monte Carlo Simulation (MCS) to model the ProTom proton beam to generate DDDs. The MCS generated DDDs were used to account for halo effects of proton pencil beam that are not measureable with Bragg peak chambers. We also used PTW PEAKFINDER to measure DDDs for comparison purpose. Results: We compared measured and MCS DDDs with Continuous Slowing Down Approximation (CSDA) ranges to verify the range of proton beams that were supplied by the manufacturer. The agreements between all DDD with respect to CSDA were within ±0.5 mm. The WET for Bragg peak chamber for energies between 100–250 MeV was 12.7 ± 0.5 mm. The correction for halo effect was negligible below 150 MeV and was in order of ∼5-10% for 150–250 MeV. Conclusion: Use of Bragg Peak chamber as a reference chamber can facilitate DDD measurements in proton pencil beam with a high accuracy. Some corrections will be required to account for halo effect in case of high energy proton beams due to physical size of chamber.

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    Significant absorbed dose levels exceeding 1.0 Gy day(exp -1) have been measured on the external surface of the Cosmos 1887 biosatellite as functions of depth in stacks of thin thermoluminescent detectors (TLD's) made in U.S.S.R. and U.S.A. 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.

  15. Turbid water measurements of remote sensing penetration depth at visible and near-infrared wavelength

    NASA Technical Reports Server (NTRS)

    Morris, W. D.; Witte, W. G.; Whitlock, C. H.

    1980-01-01

    Remote sensing of water quality is dicussed. Remote sensing penetration depth is a function both of water type and wavelength. Results of three tests to help demonstrate the magnitude of this dependence are presented. The water depth to which the remote-sensor data was valid was always less than that of the Secchi disk depth, although not always the same fraction of that depth. The penetration depths were wavelength dependent and showed the greatest variation for the water type with largest Secchi depth. The presence of a reflective plate, simulating a reflective subsurface, increased the apparent depth of light penetration from that calculated for water of infinite depth.

  16. The distribution of absorbed dose from x-rays as a function of depth

    NASA Astrophysics Data System (ADS)

    Cummings, Frederick

    2000-08-01

    Organizations responsible for monitoring the occupational exposure to radiation workers in the U.S. are directed to measure the dose to specific depths in tissue. The knowledge of the depth distribution of energy deposited by radiation in materials is essential to the interpretation of devices used to measure occupational exposure In this work, the quantities used to convert the reference transfer quantity for x-ray fields, air kerma, to the regulatory quantity, dose equivalent, for mono- energetic x-ray fields and poly-energetic x-ray fields specified by the National Institute of Standards and Technology are cogenerated for European x-ray fields are indicated and consistent conversion factors for use in the U.S. are recommended. For the mono-energetic x-ray beams conversion factors ranged from 0.9 to 1.7 at the 7 mg/cm2 depth and from 0.03 to 1.9 at the 1000 mg/cm2 depth in tissue specified by the International Commission of Radiation Units and Measurements. The conversion factors for the NIST x-ray fields were reasonably consistent with values in an unpublished draft standard by the American National Standards Institute, but exhibited sufficient disagreement to warrant a re-evaluation of the factors in that document prior to publication.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    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.

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

    SciTech Connect

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

    1989-05-01

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

  19. Estimating plant water uptake source depths with optimized stable water isotope labeling

    NASA Astrophysics Data System (ADS)

    Seeger, Stefan; Weiler, Markus

    2016-04-01

    Depth profiles of pore water stable isotopes in soils in conjunction with measurements of stable water isotopes (SWI) in plant transpiration allow the estimation of the contributions of different soil depths to plant water uptake (PWU).
 However, SWI depth profiles that result from the variations of SWI in natural precipitation may lead to highly ambiguous results, i.e. the same SWI signature in transpiration could result from different PWU patterns or SWI depth profiles. The aim of this study was to find an optimal stable water isotope depth profile to estimate plant water uptake patterns and to compare different PWU source depth estimation methods. We used a new soil water transport model including fractionation effects of SWI and exchange between the vapor and liquid phase to simulate different irrigation scenarios. Different amounts of water with differing SWI signatures (glacier melt water, summer precipitation water, deuterated water) were applied in order to obtain a wide variety of SWI depth profiles. Based on these simulated SWI depth profiles and a set of hypothetical PWU patterns, the theoretical SWI signatures of the respective plant transpiration were computed. In the next step, two methods - Bayesian isotope mixing models (BIMs) and optimization of a parametric distribution function (beta function) - were used to estimate the PWU patterns from the different SWI depth profiles and their respective SWI signatures in the resulting transpiration. Eventually, the estimated and computed profiles were compared to find the best SWI depth profile and the best method. The results showed, that compared to naturally occurring SWI depth profiles, the application of multiple, in terms of SWI, distinct labeling pulses greatly improves the possible spatial resolution and at the same time reduces the uncertainty of PWU estimates.
 For the PWU patterns which were assumed for this study, PWU pattern estimates based on an optimized parametric distribution function

  20. Vertical distribution of radiation dose rates in the water of a brackish lake in Aomori Prefecture, Japan.

    PubMed

    Ohtsuka, Yoshihito; Iyogi, Takashi; Ueda, Shinji; Hisamatsu, Shun'ichi

    2015-11-01

    Seasonal radiation dose rates were measured with glass dosemeters housed in watertight cases at various depths in the water of Lake Obuchi, a brackish lake in Aomori Prefecture, Japan, during fiscal years 2011-2013 to assess the background external radiation dose to aquatic biota in the lake. The mean radiation dose in the surface water of the lake was found to be 27 nGy h(-1), which is almost the same as the absorption dose rate due to cosmic ray reported in the literature. Radiation dose rates decreased exponentially with water depth down to a depth of 1 m above the bottom sediment. In the water near the sediment, the dose rate increased with depth owing to the emission of γ-rays from natural radionuclides in the sediment. PMID:25944958

  1. Remote sensing of water depths in shallow waters via artificial neural networks

    NASA Astrophysics Data System (ADS)

    Ceyhun, Özçelik; Yalçın, Arısoy

    2010-09-01

    Determination of the water depths in coastal zones is a common requirement for the majority of coastal engineering and coastal science applications. However, production of high quality bathymetric maps requires expensive field survey, high technology equipment and expert personnel. Remotely sensed images can be conveniently used to reduce the cost and labor needed for bathymetric measurements and to overcome the difficulties in spatial and temporal depth provision. An Artificial Neural Network (ANN) methodology is introduced in this study to derive bathymetric maps in shallow waters via remote sensing images and sample depth measurements. This methodology provides fast and practical solution for depth estimation in shallow waters, coupling temporal and spatial capabilities of remote sensing imagery with modeling flexibility of ANN. Its main advantage in practice is that it enables to directly use image reflectance values in depth estimations, without refining depth-caused scatterings from other environmental factors (e.g. bottom material and vegetation). Its function-free structure allows evaluating nonlinear relationships between multi-band images and in-situ depth measurements, therefore leads more reliable depth estimations than classical regressive approaches. The west coast of the Foca, Izmir/Turkey was used as a test bed. Aster first three band images and Quickbird pan-sharpened images were used to derive ANN based bathymetric maps of this study area. In-situ depth measurements were supplied from the General Command of Mapping, Turkey (HGK). Two models were set, one for Aster and one for Quickbird image inputs. Bathymetric maps relying solely on in-situ depth measurements were used to evaluate resultant derived bathymetric maps. The efficiency of the methodology was discussed at the end of the paper. It is concluded that the proposed methodology could decrease spatial and repetitive depth measurement requirements in bathymetric mapping especially for

  2. TLP production risers for 1200-m water depth

    SciTech Connect

    Delgado, J.H.; Erb, P.R. ); Moe, G. )

    1988-11-01

    A number of technically feasible alternative riser systems exist for tension leg platform (TLP) production systems in deep water. These include conventional steel, steel with added buoyancy, titanium, and carbon-fiber composite. The last three of these options provide substantial reductions in required riser tension for a 1200-m (3,935-ft) depth. For a minimum-size TLP, these reduced tensions translate into substantial reductions in fabricated steel weight. Replacing conventional top tensioners with a hard-mount or gimbal arrangement requires a relatively small increase in top tension, which would be balanced out by weight savings on the tensioning equipment. Operational concerns related to pressure and temperature changes must be addressed to ensure feasibility of the hard-mount or gimbal approach.

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

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

    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

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

    PubMed

    Kurz, C; Mairani, A; Parodi, K

    2012-08-01

    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 (16)O 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

  5. Irrigation depth far exceeds water uptake depth in an oasis cropland in the middle reaches of Heihe River Basin

    PubMed Central

    Yang, Bin; Wen, Xuefa; Sun, Xiaomin

    2015-01-01

    Agricultural irrigation in the middle reaches of the Heihe River Basin consumes approximately 80% of the total river water. Whether the irrigation depth matches the water uptake depth of crops is one of the most important factors affecting the efficiency of irrigation water use. Our results indicated that the influence of plastic film on soil water δ18O was restricted to 0–30 cm soil depth. Based on a Bayesian model (MixSIR), we found that irrigated maize acquired water preferentially from 0–10 cm soil layer, with a median uptake proportion of 87 ± 15%. Additionally, maize utilised a mixture of irrigation and shallow soil water instead of absorbing the irrigation water directly. However, only 24.7 ± 5.5% of irrigation water remained in 0–10 cm soil layer, whereas 29.5 ± 2.8% and 38.4 ± 3.3% of the irrigation water infiltrated into 10–40 cm and 40–80 cm layers. During the 4 irrigation events, approximately 39% of the irrigation and rainwater infiltrated into soil layers below 80 cm. Reducing irrigation amount and developing water-saving irrigation methods will be important strategies for improving the efficiency of irrigation water use in this area. PMID:26463010

  6. Irrigation depth far exceeds water uptake depth in an oasis cropland in the middle reaches of Heihe River Basin.

    PubMed

    Yang, Bin; Wen, Xuefa; Sun, Xiaomin

    2015-01-01

    Agricultural irrigation in the middle reaches of the Heihe River Basin consumes approximately 80% of the total river water. Whether the irrigation depth matches the water uptake depth of crops is one of the most important factors affecting the efficiency of irrigation water use. Our results indicated that the influence of plastic film on soil water δ(18)O was restricted to 0-30 cm soil depth. Based on a Bayesian model (MixSIR), we found that irrigated maize acquired water preferentially from 0-10 cm soil layer, with a median uptake proportion of 87 ± 15%. Additionally, maize utilised a mixture of irrigation and shallow soil water instead of absorbing the irrigation water directly. However, only 24.7 ± 5.5% of irrigation water remained in 0-10 cm soil layer, whereas 29.5 ± 2.8% and 38.4 ± 3.3% of the irrigation water infiltrated into 10-40 cm and 40-80 cm layers. During the 4 irrigation events, approximately 39% of the irrigation and rainwater infiltrated into soil layers below 80 cm. Reducing irrigation amount and developing water-saving irrigation methods will be important strategies for improving the efficiency of irrigation water use in this area. PMID:26463010

  7. Irrigation depth far exceeds water uptake depth in an oasis cropland in the middle reaches of Heihe River Basin

    NASA Astrophysics Data System (ADS)

    Yang, Bin; Wen, Xuefa; Sun, Xiaomin

    2015-10-01

    Agricultural irrigation in the middle reaches of the Heihe River Basin consumes approximately 80% of the total river water. Whether the irrigation depth matches the water uptake depth of crops is one of the most important factors affecting the efficiency of irrigation water use. Our results indicated that the influence of plastic film on soil water δ18O was restricted to 0-30 cm soil depth. Based on a Bayesian model (MixSIR), we found that irrigated maize acquired water preferentially from 0-10 cm soil layer, with a median uptake proportion of 87 ± 15%. Additionally, maize utilised a mixture of irrigation and shallow soil water instead of absorbing the irrigation water directly. However, only 24.7 ± 5.5% of irrigation water remained in 0-10 cm soil layer, whereas 29.5 ± 2.8% and 38.4 ± 3.3% of the irrigation water infiltrated into 10-40 cm and 40-80 cm layers. During the 4 irrigation events, approximately 39% of the irrigation and rainwater infiltrated into soil layers below 80 cm. Reducing irrigation amount and developing water-saving irrigation methods will be important strategies for improving the efficiency of irrigation water use in this area.

  8. Limited accuracy of dose calculation for large fields at deep depths using the BrainSCAN v5.21 treatment planning system.

    PubMed

    Hsi, Wen C; Zhang, Yunkai; Kirk, Michael C; Bernard, Damian; Chu, James C H

    2005-01-01

    The Varian 120 multileaf collimator (MLC) has a leaf thickness of 5 mm projected at the isocenter plane and can deliver a radiation beam of large field size (up to 30 cm) to be used in intensity-modulated radiotherapy (IMRT). Often the dose must be delivered to depths greater than 20 cm. Therefore, during the commissioning of the BrainSCAN v5.21 or any radiation treatment-planning (RTP) systems, extensive testing of dose and monitor unit calculations must encompass the field sizes (1 cm to 30 cm) and the prescription depths (1 cm to 20 cm). Accordingly, the central-axis percent depth doses (PDDs) and off-axis percentage profiles must be measured at several depths for various field sizes. The data for this study were acquired with a 6-MV X-ray beam from a Varian 2100EX LINAC with a water phantom at a source-to-surface distance (SSD) of 100 cm. These measurements were also used to generate a photon beam module, based on a photon pencil beam dose-calculation algorithm with a fast-Fourier transform method. To commission the photon beam module used in our BrainSCAN RTP system, we performed a quantitative comparison of measured and calculated central-axis depth doses and off-axis profiles. Utilizing the principles of dose difference and distance-to-agreement introduced by Van Dyk et al. [Commissioning and quality assurance of treatment planning computers. Int J Radiat Oncol Biol Phys. 1993; 26:261-273], agreements between calculated and measured doses are <2% and <2 mm for the regions of low- and high-dose gradients, respectively. However, large errors (up to approximately 5% and approximately 7% for 20-cm and 30-cm fields, respectively, at the depth 20 cm) were observed for monitor unit calculations. For a given field size, the disagreement increased with the depth. Similarly, for a given depth the disagreement also increase with the field size. These large systematic errors were caused by using the tissue maximum ratio (TMR) in BrainSCAN v5.21 without considering

  9. Final Aperture Superposition Technique applied to fast calculation of electron output factors and depth dose curves

    SciTech Connect

    Faddegon, B.A.; Villarreal-Barajas, J.E.

    2005-11-15

    The Final Aperture Superposition Technique (FAST) is described and applied to accurate, near instantaneous calculation of the relative output factor (ROF) and central axis percentage depth dose curve (PDD) for clinical electron beams used in radiotherapy. FAST is based on precalculation of dose at select points for the two extreme situations of a fully open final aperture and a final aperture with no opening (fully shielded). This technique is different than conventional superposition of dose deposition kernels: The precalculated dose is differential in position of the electron or photon at the downstream surface of the insert. The calculation for a particular aperture (x-ray jaws or MLC, insert in electron applicator) is done with superposition of the precalculated dose data, using the open field data over the open part of the aperture and the fully shielded data over the remainder. The calculation takes explicit account of all interactions in the shielded region of the aperture except the collimator effect: Particles that pass from the open part into the shielded part, or visa versa. For the clinical demonstration, FAST was compared to full Monte Carlo simulation of 10x10,2.5x2.5, and 2x8 cm{sup 2} inserts. Dose was calculated to 0.5% precision in 0.4x0.4x0.2 cm{sup 3} voxels, spaced at 0.2 cm depth intervals along the central axis, using detailed Monte Carlo simulation of the treatment head of a commercial linear accelerator for six different electron beams with energies of 6-21 MeV. Each simulation took several hours on a personal computer with a 1.7 Mhz processor. The calculation for the individual inserts, done with superposition, was completed in under a second on the same PC. Since simulations for the pre calculation are only performed once, higher precision and resolution can be obtained without increasing the calculation time for individual inserts. Fully shielded contributions were largest for small fields and high beam energy, at the surface, reaching a

  10. Studies on depth-dose-distribution controls by deuteration and void formation in boron neutron capture therapy.

    PubMed

    Sakurai, Yoshinori

    2004-08-01

    Physical studies on (i) replacement of heavy water for body water (deuteration), and (ii) formation of a void in human body (void formation) were performed as control techniques for dose distribution in a human head under neutron capture therapy. Simulation calculations were performed for a human-head-size cylindrical phantom using a two-dimensional transport calculation code for mono-energetic incidences of higher-energy epi-thermal neutrons (1.2-10 keV), lower-energy epi-thermal neutrons (3.1-23 eV) and thermal neutrons (1 meV to 0.5 eV). The deuteration was confirmed to be effective both in thermal neutron incidence and in epi-thermal neutron incidence from the viewpoints of improvement of the thermal neutron flux distribution and elimination of the secondary gamma rays. For the void formation, a void was assumed to be 4 cm in diameter and 3 cm in depth at the surface part in this study. It was confirmed that the treatable depth was improved almost 2 cm for any incident neutron energy in the case of the 10 cm irradiation field diameter. It was made clear that the improvement effect was larger in isotropic incidence than in parallel incidence, in the case that an irradiation field size was delimited fitting into a void diameter. PMID:15379019

  11. Experimental depth dose curves of a 67.5 MeV proton beam for benchmarking and validation of Monte Carlo simulation

    PubMed Central

    Faddegon, Bruce A.; Shin, Jungwook; Castenada, Carlos M.; Ramos-Méndez, José; Daftari, Inder K.

    2015-01-01

    Purpose: To measure depth dose curves for a 67.5 ± 0.1 MeV proton beam for benchmarking and validation of Monte Carlo simulation. Methods: Depth dose curves were measured in 2 beam lines. Protons in the raw beam line traversed a Ta scattering foil, 0.1016 or 0.381 mm thick, a secondary emission monitor comprised of thin Al foils, and a thin Kapton exit window. The beam energy and peak width and the composition and density of material traversed by the beam were known with sufficient accuracy to permit benchmark quality measurements. Diodes for charged particle dosimetry from two different manufacturers were used to scan the depth dose curves with 0.003 mm depth reproducibility in a water tank placed 300 mm from the exit window. Depth in water was determined with an uncertainty of 0.15 mm, including the uncertainty in the water equivalent depth of the sensitive volume of the detector. Parallel-plate chambers were used to verify the accuracy of the shape of the Bragg peak and the peak-to-plateau ratio measured with the diodes. The uncertainty in the measured peak-to-plateau ratio was 4%. Depth dose curves were also measured with a diode for a Bragg curve and treatment beam spread out Bragg peak (SOBP) on the beam line used for eye treatment. The measurements were compared to Monte Carlo simulation done with geant4 using topas. Results: The 80% dose at the distal side of the Bragg peak for the thinner foil was at 37.47 ± 0.11 mm (average of measurement with diodes from two different manufacturers), compared to the simulated value of 37.20 mm. The 80% dose for the thicker foil was at 35.08 ± 0.15 mm, compared to the simulated value of 34.90 mm. The measured peak-to-plateau ratio was within one standard deviation experimental uncertainty of the simulated result for the thinnest foil and two standard deviations for the thickest foil. It was necessary to include the collimation in the simulation, which had a more pronounced effect on the peak-to-plateau ratio for the

  12. Leaching of pesticides from biobeds: effect of biobed depth and water loading.

    PubMed

    Fogg, Paul; Boxall, Alistair B A; Walker, Allan; Jukes, Andrew

    2004-10-01

    Pesticides may be released to farmyard surfaces as a result of spillages, leakages, and the decontamination of tractors and sprayers. Biobeds can be used to intercept and treat contaminated runoff, thus minimizing losses to the environment. Previous studies using lined and unlined biobeds showed that water management was the limiting factor for both systems. While lined biobeds effectively retained pesticides, the system rapidly became water logged and degradation was slow. Studies using unlined biobeds showed that >99% of the applied pesticides were removed by the system, with a significant proportion degraded within 9 months. However, peak concentrations of certain pesticides (Koc < 125) were unacceptable to the regulatory authorities. These experiments were designed to optimize the design and management of unlined biobeds. Experiments performed to investigate the relationship between biobed depth and water loading showed that biobeds need to have a minimum depth of 1-1.5 m. The surface area dimension of the biobed depends on the water loading, which is controlled by the nature and frequency of pesticide handling activities on the farm. Leaching losses of all but the most mobile (Koc < 15) pesticides were <0.32% of the applied dose from 1.5 m deep biobeds subject to a water loading of 1175 L m(-2). These were reduced to <0.06% when a water loading of 688 L m(-2) was applied and down to <0.0001% for a water loading of 202 L m(-2). On the basis of these data, a 1.5 m deep biobed, subject to a maximum water loading of 1121 L m(-2) and with a surface area of 40 m(2) should be able to treat < or =44000 L of pesticide waste and washings such that the average concentration of all pesticides, other than those classified as very mobile, does not exceed 5 microg L(-1). This level of treatment can be improved by further reduction in the hydraulic loading. PMID:15453690

  13. Comparison of depth-dose distributions of proton therapeutic beams calculated by means of logical detectors and ionization chamber modeled in Monte Carlo codes

    NASA Astrophysics Data System (ADS)

    Pietrzak, Robert; Konefał, Adam; Sokół, Maria; Orlef, Andrzej

    2016-08-01

    The success of proton therapy depends strongly on the precision of treatment planning. Dose distribution in biological tissue may be obtained from Monte Carlo simulations using various scientific codes making it possible to perform very accurate calculations. However, there are many factors affecting the accuracy of modeling. One of them is a structure of objects called bins registering a dose. In this work the influence of bin structure on the dose distributions was examined. The MCNPX code calculations of Bragg curve for the 60 MeV proton beam were done in two ways: using simple logical detectors being the volumes determined in water, and using a precise model of ionization chamber used in clinical dosimetry. The results of the simulations were verified experimentally in the water phantom with Marcus ionization chamber. The average local dose difference between the measured relative doses in the water phantom and those calculated by means of the logical detectors was 1.4% at first 25 mm, whereas in the full depth range this difference was 1.6% for the maximum uncertainty in the calculations less than 2.4% and for the maximum measuring error of 1%. In case of the relative doses calculated with the use of the ionization chamber model this average difference was somewhat greater, being 2.3% at depths up to 25 mm and 2.4% in the full range of depths for the maximum uncertainty in the calculations of 3%. In the dose calculations the ionization chamber model does not offer any additional advantages over the logical detectors. The results provided by both models are similar and in good agreement with the measurements, however, the logical detector approach is a more time-effective method.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

  15. Solar Inactivation of Enterococci and Escherichia coli in Natural Waters: Effects of Water Absorbance and Depth.

    PubMed

    Maraccini, Peter A; Mattioli, Mia Catharine M; Sassoubre, Lauren M; Cao, Yiping; Griffith, John F; Ervin, Jared S; Van De Werfhorst, Laurie C; Boehm, Alexandria B

    2016-05-17

    The decay of sewage-sourced Escherichia coli and enterococci was measured at multiple depths in a freshwater marsh, a brackish water lagoon, and a marine site, all located in California. The marine site had very clear water, while the waters from the marsh and lagoon contained colored dissolved organic matter that not only blocked light but also produced reactive oxygen species. First order decay rate constants of both enterococci and E. coli were between 1 and 2 d(-1) under low light conditions and as high as 6 d(-1) under high light conditions. First order decay rate constants were well correlated to the daily average UVB light intensity corrected for light screening incorporating water absorbance and depth, suggesting endogenous photoinactivation is a major pathway for bacterial decay. Additional laboratory experiments demonstrated the presence of colored dissolved organic matter in marsh water enhanced photoinactivation of a laboratory strain of Enterococcus faecalis, but depressed photoinactivation of sewage-sourced enterococci and E. coli after correcting for UVB light screening, suggesting that although the exogenous indirect photoinactivation mechanism may be active against Ent. faecalis, it is not for the sewage-source organisms. A simple linear regression model based on UVB light intensity appears to be a useful tool for predicting inactivation rate constants in natural waters of any depth and absorbance. PMID:27119980

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

    USGS Publications Warehouse

    Snyder, Daniel T.

    2008-01-01

    Reliable information on the configuration of the water table in the Portland metropolitan area is needed to address concerns about various water-resource issues, especially with regard to potential effects from stormwater injection systems such as UIC (underground injection control) systems that are either existing or planned. To help address these concerns, this report presents the estimated depth-to-water and water-table elevation maps for the Portland area, along with estimates of the relative uncertainty of the maps and seasonal water-table fluctuations. The method of analysis used to determine the water-table configuration in the Portland area relied on water-level data from shallow wells and surface-water features that are representative of the water table. However, the largest source of available well data is water-level measurements in reports filed by well constructors at the time of new well installation, but these data frequently were not representative of static water-level conditions. Depth-to-water measurements reported in well-construction records generally were shallower than measurements by the U.S. Geological Survey (USGS) in the same or nearby wells, although many depth-to-water measurements were substantially deeper than USGS measurements. Magnitudes of differences in depth-to-water measurements reported in well records and those measured by the USGS in the same or nearby wells ranged from -119 to 156 feet with a mean of the absolute value of the differences of 36 feet. One possible cause for the differences is that water levels in many wells reported in well records were not at equilibrium at the time of measurement. As a result, the analysis of the water-table configuration relied on water levels measured during the current study or used in previous USGS investigations in the Portland area. Because of the scarcity of well data in some areas, the locations of select surface-water features including major rivers, streams, lakes, wetlands, and

  17. Relationship between body condition of American alligators and water depth in the Everglades, Florida

    USGS Publications Warehouse

    Fujisaki, Ikuko; Rice, Kenneth G.; Pearlstine, Leonard G.; Mazzotti, Frank J.

    2009-01-01

    Feeding opportunities of American alligators (Alligator mississippiensis) in freshwater wetlands in south Florida are closely linked to hydrologic conditions. In the Everglades, seasonally and annually fluctuating surface water levels affect populations of aquatic organisms that alligators consume. Since prey becomes more concentrated when water depth decreases, we hypothesized an inverse relationship between body condition and water depth in the Everglades. On average, condition of adult alligators in the dry season was significantly higher than in the wet season, but this was not the case for juveniles/subadults. The correlation between body condition and measured water depth at capture locations was weak; however, there was a significant negative correlation between the condition and predicted water depth prior to capture for all animals except for spring juveniles/subadults which had a weak positive condition-water depth relationship. Overall, a relatively strong inverse correlation occurred at 10-49 days prior to the capture day, suggesting that current body condition of alligators may depend on feeding opportunities during that period. Fitted regression of body condition on water depth (mean depth of 10 days when condition-water depth correlation was greatest) resulted in a significantly negative slope, except for spring adult females and spring juveniles/subadults for which slopes were not significantly different from zero. Our results imply that water management practices may be critical for alligators in the Everglades since water depth can affect animal condition in a relatively short period of time.

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

    NASA Astrophysics Data System (ADS)

    Pshenichnov, Igor; Mishustin, Igor; Greiner, Walter

    2008-04-01

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

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

    SciTech Connect

    Chung, Hyun-Tai; Park, Youngho; Hyun, Sangil; Choi, Yongsoo; Kim, Gi Hong; Kim, Dong Gyu; Chun, Kook Jin

    2011-04-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

    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.

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

    PubMed Central

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

    2013-01-01

    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

  2. Regression analysis of growth responses to water depth in three wetland plant species

    PubMed Central

    Sorrell, Brian K.; Tanner, Chris C.; Brix, Hans

    2012-01-01

    Background and aims Plant species composition in wetlands and on lakeshores often shows dramatic zonation, which is frequently ascribed to differences in flooding tolerance. This study compared the growth responses to water depth of three species (Phormium tenax, Carex secta and Typha orientalis) differing in depth preferences in wetlands, using non-linear and quantile regression analyses to establish how flooding tolerance can explain field zonation. Methodology Plants were established for 8 months in outdoor cultures in waterlogged soil without standing water, and then randomly allocated to water depths from 0 to 0.5 m. Morphological and growth responses to depth were followed for 54 days before harvest, and then analysed by repeated-measures analysis of covariance, and non-linear and quantile regression analysis (QRA), to compare flooding tolerances. Principal results Growth responses to depth differed between the three species, and were non-linear. Phormium tenax growth decreased rapidly in standing water >0.25 m depth, C. secta growth increased initially with depth but then decreased at depths >0.30 m, accompanied by increased shoot height and decreased shoot density, and T. orientalis was unaffected by the 0- to 0.50-m depth range. In P. tenax the decrease in growth was associated with a decrease in the number of leaves produced per ramet and in C. secta the effect of water depth was greatest for the tallest shoots. Allocation patterns were unaffected by depth. Conclusions The responses are consistent with the principle that zonation in the field is primarily structured by competition in shallow water and by physiological flooding tolerance in deep water. Regression analyses, especially QRA, proved to be powerful tools in distinguishing genuine phenotypic responses to water depth from non-phenotypic variation due to size and developmental differences. PMID:23259044

  3. Borehole sounding device with sealed depth and water level sensors

    DOEpatents

    Skalski, Joseph C.; Henke, Michael D.

    2005-08-02

    A borehole device having proximal and distal ends comprises an enclosure at the proximal end for accepting an aircraft cable containing a plurality of insulated conductors from a remote position. A water sensing enclosure is sealingly attached to the enclosure and contains means for detecting water, and sending a signal on the cable to the remote position indicating water has been detected. A bottom sensing enclosure is sealingly attached to the water sensing enclosure for determining when the borehole device encounters borehole bottom and sends a signal on the cable to the remote position indicating that borehole bottom has been encountered.

  4. Sugarcane Response to Water-Table Depth and Periodic Flooding

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sugarcane (Saccharum spp.) in the Everglades Agricultural Area (EAA) of Florida is often exposed to high water tables and periodic floods. Growers are concerned that elevated water tables for prolonged periods and during certain phases of growth reduce yields. However, these wet conditions help redu...

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

    PubMed

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

    2005-03-01

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

  6. Measurement of LET (linear energy transfer) spectra using CR-39 at different depths of water irradiated by 171 MeV protons: A comparison with Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Sahoo, G. S.; Tripathy, S. P.; Molokanov, A. G.; Aleynikov, V. E.; Sharma, S. D.; Bandyopadhyay, T.

    2016-05-01

    In this work, we have used CR-39 detectors to estimate the LET (linear energy transfer) spectrum of secondary particles due to 171 MeV proton beam at different depths of water including the Bragg peak region. The measured LET spectra were compared with those obtained from FLUKA Monte Carlo simulation. The absorbed dose (DLET), dose equivalent (HLET) were estimated using the LET spectra. The values of DLET and HLET per incident proton fluence were found to increase with the increase in depth of water and were maximum at Bragg peak.

  7. Links between climate change, water-table depth, and water chemistry in a mineralized mountain watershed

    USGS Publications Warehouse

    Manning, Andrew H.; Verplanck, Philip L.; Caine; Todd, Andrew S.

    2013-01-01

    Recent studies suggest that climate change is causing rising solute concentrations in mountain lakes and streams. These changes may be more pronounced in mineralized watersheds due to the sensitivity of sulfide weathering to changes in subsurface oxygen transport. Specific causal mechanisms linking climate change and accelerated weathering rates have been proposed, but in general remain entirely hypothetical. For mineralized watersheds, a favored hypothesis is that falling water tables caused by declining recharge rates allow an increasing volume of sulfide-bearing rock to become exposed to air, thus oxygen. Here, we test the hypothesis that falling water tables are the primary cause of an increase in metals and SO4 (100-400%) observed since 1980 in the Upper Snake River (USR), Colorado. The USR drains an alpine watershed geologically and climatologically representative of many others in mineralized areas of the western U.S. Hydrologic and chemical data collected from 2005 to 2011 in a deep monitoring well (WP1) at the top of the USR watershed are utilized. During this period, both water table depths and groundwater SO4 concentrations have generally increased in the well. A numerical model was constructed using TOUGHREACT that simulates pyrite oxidation near WP1, including groundwater flow and oxygen transport in both saturated and unsaturated zones. The modeling suggests that a falling water table could produce an increase in metals and SO4 of a magnitude similar to that observed in the USR (up to 300%). Future water table declines may produce limited increases in sulfide weathering high in the watershed because of the water table dropping below the depth of oxygen penetration, but may continue to enhance sulfide weathering lower in the watershed where water tables are shallower. Advective air (oxygen) transport in the unsaturated zone caused by seasonally variable recharge and associated water table fluctuations was found to have little influence on pyrite

  8. Exposure dose reduction during lateral spine test with water filter.

    PubMed

    Kim, Chang-Gyu

    2016-05-18

    To minimize exposure dose during lateral spine X-Ray testing and obtain optimal image for diagnosis a water filter was made to measure and evaluate dose distribution. When applying the water filter, as thickness increased exposure dose decreased. When applying 2 cm of water filter, clarity of contrast and boundary was found to be 4.5 ± 0.5 and resolution was found to be 2.00 ± 0.5 Lp/mm which was almost identical image quality compared to not applying water filter which showed clarity of contrast and boundary of 5.0 ± 0.0, and resolution of 2.50 ± 0.0 Lp/mm, while reducing exposure dose by 55%. This result is expected to have many uses as important basic data to predict exposure dose of patients and to minimize medical exposure dose through applying water filters during lateral spine X-Ray testing. PMID:26684401

  9. Deep water drilling and production Articulated Column - Water depth 350m

    SciTech Connect

    Baduel, F.; Figenschou, A.

    1985-01-01

    An Articulated Tower for drilling and production in the Norwegian Sea for 350m water depth is presented. Main features are: Christmas trees at the deck-level, 17,000 tonnes deck payload, limited motions, steel structure including main float and lattice, low stressed mechanical articulation with anti-torque device and controlled bending risers. The extensive study has considered in detail the behaviour in extreme conditions, the fatigue of main structural parts and risers, operating procedures, fabrication and installation. General results are given concerning behaviour, structural design, articulation, bending riser, fabrication and installation. A fabrication and installation schedule is also given.

  10. 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...

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

    USGS Publications Warehouse

    Cade, B.S.; Dong, Q.

    2008-01-01

    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.

  12. Water waves as a spatial dynamical system; infinite depth case.

    PubMed

    Barrandon, Matthieu; Iooss, Gérard

    2005-09-01

    We review the mathematical results on traveling waves in one or several superposed layers of potential flow, subject to gravity, with or without surface and interfacial tension, where the bottom layer is infinitely deep. The problem is formulated as a "spatial dynamical system," and it is shown that the linearized operator of the resulting reversible system has an essential spectrum filling the real line. We consider three cases where bifurcation occurs. (i) The first case is when, in moving a parameter, two pairs of imaginary eigenvalues merge into one pair of double eigenvalues, and then split into four symmetric complex conjugate eigenvalues. (ii) The second case is when one pair of imaginary eigenvalues meet in 0, and disappear; (iii) the third case is when the phenomenon described in (ii) is superposed to the presence of another pair of imaginary eigenvalues sitting at finite distance from 0. We give a physical example for each case and more specially study the solitary waves and generalized solitary waves, emphasizing the differences, in the methods and in the results, between these cases and the finite depth case. PMID:16253007

  13. Cylindrical semi can produce in 300-meter water depths

    SciTech Connect

    Not Available

    1984-01-01

    This integrated modular floating production system, IMFP 300, has a storage capacity of 50,000 bbl. It combines oil production, storage, and crew accommodations for 20 within a central cylinder and 10 peripheral cylinders. The peripheral cylinders are used to store oil, with water as ballast. The structure was designed for Brazilian waters, where the strongest environmental forces are 72-knot winds, 14.2-m waves and surface currents of 3.3 knots. Crude oil is run through flexible pipes from the seabed to the on-board manifold, heated within two exchangers, and run through two serial separator units. When the field is exhausted, the unit is towed to a new site.

  14. Tracking water pathways in steep hillslopes by δ18O depth profiles of soil water

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    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 (δ18O) 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 δ18O values of precipitation (ranging from -24.7 to -2.9‰) as input data to simulate the δ18O profiles of soil water. The variability of δ18O values with depth within each soil profile and a comparison of the simulated and measured δ18O profiles were used to infer information about subsurface hydrological pathways. The temporal pattern of δ18O 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 δ18O profiles revealed spatially highly variable infiltration patterns during the snowmelt periods: The δ18O value of snow (-17.7 ± 1.9‰) was absent in several measured δ18O profiles but present in the respective simulated δ18O profiles. This indicated overland flow and/or preferential flow through the soil profile during the melt period. The applied

  15. 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...

  16. Multivariate modeling of settling depth of apple fruit (Red Delicious variety) in water.

    PubMed

    Kheiralipour, Kamran; Marzbani, Farshid

    2016-03-01

    Settling depth of apple was determined by a water column and a digital camera. The depth was experimentally modeled using multivariate regression using a coded program in MATLAB software. The best models were based on the density, dropping height volume/mass with coefficient of determination and mean square error of 0.90 and 4.08, respectively. PMID:27004104

  17. Detecting spatio-temporal controls on depth distributions of root water uptake using soil moisture patterns

    NASA Astrophysics Data System (ADS)

    Blume, Theresa; Heidbüchel, Ingo; Simard, Sonia; Güntner, Andreas; Weiler, Markus

    2016-04-01

    Landscape scale soil moisture patterns show a pronounced shift when plants become active during the growing season. Soil moisture patterns are then not only controlled by soils, topography and related abiotic site characteristics as well as site characteristic throughfall patterns but also by root water uptake. In this study root water uptake from different soil depths is estimated based on diurnal fluctuations in soil moisture content and was investigated with a setup of 15 field sites in a forest in northeastern Germany. These sites cover different topographic positions and forest stands. Vegetation types include pine forest (young and old) and different deciduous forest stands. Available data at all sites includes information at high temporal resolution from 5 soil moisture and soil temperature profiles, matric potential, piezometers and sapflow sensors as well as standard climate data. The resulting comprehensive data set of depth distributed root water uptake shows differences in overall amounts as well as in uptake depth distributions between different forest stands, but also related to slope position and thus depth to groundwater. Temporal dynamics of signal strength within the profile suggest a locally shifting spatial distribution of root water uptake depending on water availability. The relative contributions of the different depths to overall root water uptake shift as the summer progresses. However, the relationship of these depth resolved uptake rates to overall soil water availability varies considerably between tree species. This unique data set of depth specific contributions to root water uptake down to a depth of 2 m allows a much more detailed analysis of tree response to water availability than the more common transpiration estimates generated by sapflow or eddy flux measurements.

  18. Determination of water depth with high-resolution satellite imagery over variable bottom types

    USGS Publications Warehouse

    Stumpf, Richard P.; Holderied, Kristine; Sinclair, Mark

    2003-01-01

    A standard algorithm for determining depth in clear water from passive sensors exists; but it requires tuning of five parameters and does not retrieve depths where the bottom has an extremely low albedo. To address these issues, we developed an empirical solution using a ratio of reflectances that has only two tunable parameters and can be applied to low-albedo features. The two algorithms--the standard linear transform and the new ratio transform--were compared through analysis of IKONOS satellite imagery against lidar bathymetry. The coefficients for the ratio algorithm were tuned manually to a few depths from a nautical chart, yet performed as well as the linear algorithm tuned using multiple linear regression against the lidar. Both algorithms compensate for variable bottom type and albedo (sand, pavement, algae, coral) and retrieve bathymetry in water depths of less than 10-15 m. However, the linear transform does not distinguish depths >15 m and is more subject to variability across the studied atolls. The ratio transform can, in clear water, retrieve depths in >25 m of water and shows greater stability between different areas. It also performs slightly better in scattering turbidity than the linear transform. The ratio algorithm is somewhat noisier and cannot always adequately resolve fine morphology (structures smaller than 4-5 pixels) in water depths >15-20 m. In general, the ratio transform is more robust than the linear transform.

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

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

    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.

  20. Percentage depth dose calculation accuracy of model based algorithms in high energy photon small fields through heterogeneous media and comparison with plastic scintillator dosimetry.

    PubMed

    Alagar, Ananda Giri Babu; Kadirampatti Mani, Ganesh; Karunakaran, Kaviarasu

    2016-01-01

    Small fields smaller than 4 × 4 cm2 are used in stereotactic and conformal treatments where heterogeneity is normally present. Since dose calculation accuracy in both small fields and heterogeneity often involves more discrepancy, algorithms used by treatment planning systems (TPS) should be evaluated for achieving better treatment results. This report aims at evaluating accuracy of four model-based algorithms, X-ray Voxel Monte Carlo (XVMC) from Monaco, Superposition (SP) from CMS-Xio, AcurosXB (AXB) and analytical anisotropic algorithm (AAA) from Eclipse are tested against the measurement. Measurements are done using Exradin W1 plastic scintillator in Solid Water phantom with heterogeneities like air, lung, bone, and aluminum, irradiated with 6 and 15 MV photons of square field size ranging from 1 to 4 cm2. Each heterogeneity is introduced individually at two different depths from depth-of-dose maximum (Dmax), one setup being nearer and another farther from the Dmax. The central axis percentage depth-dose (CADD) curve for each setup is measured separately and compared with the TPS algorithm calculated for the same setup. The percentage normalized root mean squared deviation (%NRMSD) is calculated, which represents the whole CADD curve's deviation against the measured. It is found that for air and lung heterogeneity, for both 6 and 15 MV, all algorithms show maximum deviation for field size 1 × 1 cm2 and gradually reduce when field size increases, except for AAA. For aluminum and bone, all algorithms' deviations are less for 15 MV irrespective of setup. In all heterogeneity setups, 1 × 1 cm2 field showed maximum deviation, except in 6MV bone setup. All algorithms in the study, irrespective of energy and field size, when any heterogeneity is nearer to Dmax, the dose deviation is higher compared to the same heterogeneity far from the Dmax. Also, all algorithms show maximum deviation in lower-density materials compared to high-density materials. PMID:26894345

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

    NASA Astrophysics Data System (ADS)

    Ohuchi, Yoshito; Nakazono, Yoichi

    2014-06-01

    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.

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

    USGS Publications Warehouse

    Blankenbaker, G.G.

    1978-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Mihevc, T. M.; Rajagopal, S.

    2012-12-01

    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.

  4. Ground-water contribution to dose from past Hanford operations

    SciTech Connect

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

    1992-01-01

    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

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

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

    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

  6. The unique chemistry of Eastern Mediterranean water masses selects for distinct microbial communities by depth.

    PubMed

    Techtmann, Stephen M; Fortney, Julian L; Ayers, Kati A; Joyner, Dominique C; Linley, Thomas D; Pfiffner, Susan M; Hazen, Terry C

    2015-01-01

    The waters of the Eastern Mediterranean are characterized by unique physical and chemical properties within separate water masses occupying different depths. Distinct water masses are present throughout the oceans, which drive thermohaline circulation. These water masses may contain specific microbial assemblages. The goal of this study was to examine the effect of physical and geological phenomena on the microbial community of the Eastern Mediterranean water column. Chemical measurements were combined with phospholipid fatty acid (PLFA) analysis and high-throughput 16S rRNA sequencing to characterize the microbial community in the water column at five sites. We demonstrate that the chemistry and microbial community of the water column were stratified into three distinct water masses. The salinity and nutrient concentrations vary between these water masses. Nutrient concentrations increased with depth, and salinity was highest in the intermediate water mass. Our PLFA analysis indicated different lipid classes were abundant in each water mass, suggesting that distinct groups of microbes inhabit these water masses. 16S rRNA gene sequencing confirmed the presence of distinct microbial communities in each water mass. Taxa involved in autotrophic nitrogen cycling were enriched in the intermediate water mass suggesting that microbes in this water mass may be important to the nitrogen cycle of the Eastern Mediterranean. The Eastern Mediterranean also contains numerous active hydrocarbon seeps. We sampled above the North Alex Mud Volcano, in order to test the effect of these geological features on the microbial community in the adjacent water column. The community in the waters overlaying the mud volcano was distinct from other communities collected at similar depths and was enriched in known hydrocarbon degrading taxa. Our results demonstrate that physical phenomena such stratification as well as geological phenomena such as mud volcanoes strongly affect microbial

  7. The Unique Chemistry of Eastern Mediterranean Water Masses Selects for Distinct Microbial Communities by Depth

    PubMed Central

    Techtmann, Stephen M.; Fortney, Julian L.; Ayers, Kati A.; Joyner, Dominique C.; Linley, Thomas D.; Pfiffner, Susan M.; Hazen, Terry C.

    2015-01-01

    The waters of the Eastern Mediterranean are characterized by unique physical and chemical properties within separate water masses occupying different depths. Distinct water masses are present throughout the oceans, which drive thermohaline circulation. These water masses may contain specific microbial assemblages. The goal of this study was to examine the effect of physical and geological phenomena on the microbial community of the Eastern Mediterranean water column. Chemical measurements were combined with phospholipid fatty acid (PLFA) analysis and high-throughput 16S rRNA sequencing to characterize the microbial community in the water column at five sites. We demonstrate that the chemistry and microbial community of the water column were stratified into three distinct water masses. The salinity and nutrient concentrations vary between these water masses. Nutrient concentrations increased with depth, and salinity was highest in the intermediate water mass. Our PLFA analysis indicated different lipid classes were abundant in each water mass, suggesting that distinct groups of microbes inhabit these water masses. 16S rRNA gene sequencing confirmed the presence of distinct microbial communities in each water mass. Taxa involved in autotrophic nitrogen cycling were enriched in the intermediate water mass suggesting that microbes in this water mass may be important to the nitrogen cycle of the Eastern Mediterranean. The Eastern Mediterranean also contains numerous active hydrocarbon seeps. We sampled above the North Alex Mud Volcano, in order to test the effect of these geological features on the microbial community in the adjacent water column. The community in the waters overlaying the mud volcano was distinct from other communities collected at similar depths and was enriched in known hydrocarbon degrading taxa. Our results demonstrate that physical phenomena such stratification as well as geological phenomena such as mud volcanoes strongly affect microbial

  8. 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...

  9. 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...

  10. Maximum Age Predictions for Optical Dating on Mars Based on Dose/Depth Models and Martian Meteorite Compositions

    NASA Astrophysics Data System (ADS)

    Franklund, R. T.; Lepper, K.

    2004-12-01

    A fundamental need in the Mars exploration portfolio is in-situ absolute dating. Optical dating has been proposed for determining the age of Mars surface features and landforms as well as the rates of martian surface processes. On Earth, the method is employed for Quaternary studies because the technique currently has a terrestrial maximum age limit of approximately 350 ka. This maximum age limit is a function of the saturation dose of the dosimeter material (silicate sediments) and the local ionizing radiation dose rate. The sources of ionizing radiation germane to optical dating are K, Rb, U, Th in the sediment/soil environment and cosmic rays. On Mars the near surface dose rate will be dominated by cosmic rays, however, at depth the decay of radioisotopes will be the principle contributor of ionizing radiation. In this work we present an evaluation of the maximum age limits for OSL dating on Mars as a function of depth. At this time we have considered only static burial. Our calculations are based on published models of and data for: (i) Mars surface cosmic dose rate and its attenuation by martian regolith, (ii) elemental analyses of Mars meteorites, (iii) an experimental evaluation of the saturation dose for the martian soil simulant JSC Mars-1. Our analysis confirms earlier inferences that optical dating should have a greater effective age range on Mars than on Earth. At depths easily accessible by penetrators or moles (1-3 m), maximum optical ages greater than 600 ka are possible. Geochronology on this scale would include at least two stadial/interstadial cycles within Mars' last "Glacial Epoch" (synchronized insolation variations between the poles). A wide range of landforms and surface processes associated with climate variability -- e.g. outwash and lacustrine deposition, large-scale eolian activation -- could potentially be optically dated. At greater depths, that could be reached by mobile drilling rigs or cryobots (10-30m), optical age maximums of 4

  11. Long-term variability of the water transparency (Secchi Depth) in the Sea of Azov

    NASA Astrophysics Data System (ADS)

    Sorokina, V. V.; Kulygin, V. V.

    2013-05-01

    The spatial, seasonal, and interannual variability of the water's transparency (Secchi depth) in the Sea of Azov is studied using the database of long term transparency measurements for the 1922-2009 period and relevant materials on the meteorological, hydrological, and hydrobiological parameters of the environment. We identified four main types of seasonal variability of the water's transparency depending on the local conditions. The mean values of the Secchi depth are calculated for the different periods, which are distinguished by the differences in the relative role of the water transparency factors associated both with the climatic variations and the human activities.

  12. Relations between erythemal UV dose, global solar radiation, total ozone column and aerosol optical depth at Uccle, Belgium

    NASA Astrophysics Data System (ADS)

    De Bock, V.; De Backer, H.; Van Malderen, R.; Mangold, A.; Delcloo, A.

    2014-06-01

    At Uccle, a long time series (1991-2013) of simultaneous measurements of erythemal ultraviolet (UV) dose, global solar radiation, total ozone column (TOC) and Aerosol Optical Depth (AOD) (at 320.1 nm) is available which allows for an extensive study of the changes in the variables over time. A change-point analysis, which determines whether there is a significant change in the mean of the time series, is applied to the monthly anomalies time series of the variables. Only for erythemal UV dose and TOC, a significant change point (without any known instrumental cause) was present in the time series around February 1998 and March 1998 respectively. The change point in TOC corresponds with results found in literature, where the change in ozone levels (around 1997) is attributed to the recovery of ozone. Linear trends were determined for the different (monthly anomalies) time series. Erythemal UV dose, global solar radiation and TOC all increase with respectively 7, 4 and 3% per decade. AOD shows an (insignificant) negative trend of -8% per decade. These trends agree with results found in literature for sites with comparable latitudes. A multiple linear regression (MLR) analysis is applied to the data in order to study the influence of global solar radiation, TOC and AOD on the erythemal UV dose. Together these parameters are able to explain 94% of the variation in erythemal UV dose. Most of the variation (56%) in erythemal UV dose is explained by global solar radiation. The regression model performs well with a slight tendency to underestimate the measured erythemal UV doses and with a Mean Absolute Bias Error (MABE) of 18%. However, in winter, negative erythemal UV dose values are modeled. Applying the MLR to the individual seasons solves this issue. The seasonal models have an adjusted R2 value higher than 0.8 and the correlation between modeled and measured erythemal UV dose values is higher than 0.9 for each season. The summer model gives the best performance, with

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

    SciTech Connect

    Hanlon, Justin Chell, Erik; Firpo, Michael; Koruga, Igor

    2014-02-15

    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

  14. Effect of plant-uptake representation on the water-optimal root depth

    NASA Astrophysics Data System (ADS)

    Guswa, A. J.

    2008-12-01

    The depth of roots depends on a variety of conditions, including soil properties, plant type, nutrient availability, and climate. A focus on water enables the determination of a water-optimal root depth by equating the marginal carbon cost of deeper roots with the benefit of those roots to continued transpiration and carbon assimilation. Calculation of the transpiration benefit requires the mathematical representation of plant uptake as a function of root depth and soil moisture. This work compares the effect of two bounding representations of plant uptake on the water-optimal root depth and the response of that depth to changes in precipitation. Soil-moisture dynamics are driven by precipitation events that arrive as a Poisson process and are characterized by a mean frequency and depth. Infiltration and drainage are instantaneous, filling the root zone up to a maximum field capacity. Plant uptake is represented in one case as a step function of soil moisture; transpiration proceeds at a potential rate until the wilting-point saturation is reached when uptake drops to zero. Until that critical threshold, soil moisture has no effect on transpiration. In the second case, transpiration decreases linearly from its potential at field capacity to zero at the wilting point; soil moisture exerts a continuous and gradual influence on plant uptake throughout the drying cycle. With both the linear and step-function representations, the water-optimal root depth is more sensitive to changes in precipitation depth than frequency under dry conditions and more sensitive to precipitation frequency when the climate is wet. Under wet conditions, optimal root depths predicted with the step function show a greater sensitivity to climate than do those based on the linear model. Under dry conditions, the reverse is true; the water-optimal root depth is slightly more sensitive to changes in precipitation when the linear model is employed than when the step function is used. For all

  15. Monte Carlo calculation of dose to water of a 106Ru COB-type ophthalmic plaque

    NASA Astrophysics Data System (ADS)

    Šolc, J.

    2008-02-01

    The concave eye applicators with 106Ru/106Rh or 90Sr/90Y beta-ray sources are worldwide used in brachytherapy for treating intraocular tumors. It raises the need to know the exact dose delivered by beta radiation to tumors but measurement of the dose to water (or tissue) is very difficult due to short range of electrons. The Monte Carlo technique provides a powerful tool for calculation of the dose and dose distributions which helps to predict and determine the doses from different shapes of various types of eye applicators more accurately. The Monte Carlo code MCNPX has been used to calculate dose distributions from a COB-type 106Ru/106Rh ophthalmic applicator manufactured by Eckert & Ziegler BEBIG GmbH. This type of a concave eye applicator has a cut-out whose purpose is to protect the eye nerve which makes the dose distribution more complicated. Several calculations have been performed including depth dose along the applicator central axis and various dose distributions. The depth dose along the applicator central axis and the dose distribution on a spherical surface 1 mm above the plaque inner surface have been compared with measurement data provided by the manufacturer. For distances from 0.5 to 4 mm above the surface, the agreement was within 2.5 % and from 5 mm the difference increased from 6 % up to 25 % at 10 mm whereas the uncertainty on manufacturer data is 20 % (2s). It is assumed that the difference is caused by nonuniformly distributed radioactivity over the applicator radioactive layer.

  16. Estimation of missing water-level data for the Everglades Depth Estimation Network (EDEN), 2013 update

    USGS Publications Warehouse

    Petkewich, Matthew D.; Conrads, Paul A.

    2013-01-01

    The Everglades Depth Estimation Network is an integrated network of real-time water-level gaging stations, a ground-elevation model, and a water-surface elevation model designed to provide scientists, engineers, and water-resource managers with water-level and water-depth information (1991-2013) for the entire freshwater portion of the Greater Everglades. The U.S. Geological Survey Greater Everglades Priority Ecosystems Science provides support for the Everglades Depth Estimation Network in order for the Network to provide quality-assured monitoring data for the U.S. Army Corps of Engineers Comprehensive Everglades Restoration Plan. In a previous study, water-level estimation equations were developed to fill in missing data to increase the accuracy of the daily water-surface elevation model. During this study, those equations were updated because of the addition and removal of water-level gaging stations, the consistent use of water-level data relative to the North American Vertical Datum of 1988, and availability of recent data (March 1, 2006, to September 30, 2011). Up to three linear regression equations were developed for each station by using three different input stations to minimize the occurrences of missing data for an input station. Of the 667 water-level estimation equations developed to fill missing data at 223 stations, more than 72 percent of the equations have coefficients of determination greater than 0.90, and 97 percent have coefficients of determination greater than 0.70.

  17. Trimethylamine oxide accumulation as a function of depth in Hawaiian mid-water fishes

    NASA Astrophysics Data System (ADS)

    Bockus, Abigail B.; Seibel, Brad A.

    2016-06-01

    Trimethylamine oxide (TMAO) is a common osmolyte and counteracting solute. It is believed to combat the denaturation induced by hydrostatic pressure as some deep-sea animals contain higher TMAO levels than their shallow water counterparts. It has also been proposed that TMAO may accumulate passively during lipid storage resulting in a correlation between lipid content and TMAO levels in some groups. Previous research showed that lipid content decreased with depth in species of Hawaiian fishes presenting a novel test of these competing hypotheses. TMAO ranged from 20.4 to 92.8 mmol/kg. Lipid content ranged from 0.50 to 4.7% WW. After completing a comprehensive search for depths available in the literature, provided here, we analyzed TMAO and lipid as a function of average, minimum and maximum depth of occurrence for 27 species of fishes from nine orders. We found that TMAO is positively correlated with all measures of habitat depth (hydrostatic pressure) but the relationship is strongest with average depth. We further showed using phylogenetic independent contrasts that this relationship was not influenced by the evolutionary relatedness of these species. Interestingly, we found that lipid content increased with depth, in direct contrast to previous studies. TMAO is thus also positively correlated with lipid content. While we are unable to distinguish between these hypotheses, we show that TMAO is strongly correlated with depth in mid-water fishes.

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

    PubMed Central

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

    2015-01-01

    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

  19. SU-E-T-540: MCNPX Simulation of Proton Dose Distributions in a Water Phantom

    SciTech Connect

    Lee, C; Chen, S; Chiang, B; Tung, C; Chao, T

    2015-06-15

    Purpose: In this study, fluence and energy deposition of proton and proton by-products and dose distributions were simulated. Lateral dose distributions were also been discussed to understand the difference between Monte Carlo simulations and pencil beam algorithm. Methods: MCNPX codes were used to build a water phantom by using “repeated structures” technique and the doses and fluences in each cell was recorded by mesh tally. This study includes, proton equilibrium and proton disequilibrium case. For the proton equilibrium case, the doses difference between proton and proton by-products were studied. A 160 MeV proton pencil beam was perpendicularly incident into a 40 × 40 × 50 cm{sup 3} water phantom and the scoring volume was 20 × 20 × 0.2 cm{sup 3}. Energy deposition and fluence were calculated from MCNPX with (1) proton only; and (2) proton and secondary particles. For the proton disequilibrium case, the dose distribution variation using different multiple Coulomb scattering were studied. A 70 MeV proton pencil beam was perpendicularly incident into a 40 × 40 × 10 cm{sup 3} water phantom and two scoring voxel sizes of 0.1 × 0.1 × 0.05 cm{sup 3} and 0.01 × 0.01 × 0.05 cm{sup 3} were used for the depth dose distribution, and 0.01 × 0.01 × 0.05 cm{sup 3} for the lateral profile distribution simulations. Results: In the water phantom, proton fluence and dose in depths beyond the Bragg peak were slightly perturbed by the choice of the simulated particle types. The dose from secondary particles was about three orders smaller, but its simulation consumed significant computing time. The depth dose distributions and lateral dose distributions of 70 MeV proton pencil beam obtained from MCNPX, GEANT4, and the pencil beam algorithm showed the significant deviations, probably caused by multiple Coulomb scattering. Conclusion: Multiple Coulomb scattering is critical when there is in proton disequilibrium.

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

    NASA Astrophysics Data System (ADS)

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

    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

  1. Fluctuating water depths affect American alligator (Alligator mississippiensis) body condition in the Everglades, Florida, USA

    USGS Publications Warehouse

    Brandt, Laura A.; Beauchamp, Jeffrey S.; Jeffery, Brian M.; Cherkiss, Michael S.; Mazzotti, Frank J.

    2016-01-01

    Successful restoration of wetland ecosystems requires knowledge of wetland hydrologic patterns and an understanding of how those patterns affect wetland plant and animal populations.Within the Everglades, Florida, USA restoration, an applied science strategy including conceptual ecological models linking drivers to indicators is being used to organize current scientific understanding to support restoration efforts. A key driver of the ecosystem affecting the distribution and abundance of organisms is the timing, distribution, and volume of water flows that result in water depth patterns across the landscape. American alligators (Alligator mississippiensis) are one of the ecological indicators being used to assess Everglades restoration because they are a keystone species and integrate biological impacts of hydrological operations through all life stages. Alligator body condition (the relative fatness of an animal) is one of the metrics being used and targets have been set to allow us to track progress. We examined trends in alligator body condition using Fulton’s K over a 15 year period (2000–2014) at seven different wetland areas within the Everglades ecosystem, assessed patterns and trends relative to restoration targets, and related those trends to hydrologic variables. We developed a series of 17 a priori hypotheses that we tested with an information theoretic approach to identify which hydrologic factors affect alligator body condition. Alligator body condition was highest throughout the Everglades during the early 2000s and is approximately 5–10% lower now (2014). Values have varied by year, area, and hydrology. Body condition was positively correlated with range in water depth and fall water depth. Our top model was the “Current” model and included variables that describe current year hydrology (spring depth, fall depth, hydroperiod, range, interaction of range and fall depth, interaction of range and hydroperiod). Across all models, interaction

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

    NASA Astrophysics Data System (ADS)

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

    2004-12-01

    The objective of this paper is to interpret microwave scattering signatures over snow cover as observed by the Advanced Microwave Sounding Unit (AMSU) for the retrievals of snow water equivalent and snow depth. A case study involving seasonal snow cover over the U.S. Great Plains was analyzed in detail. Area-wide analysis of the relationship between snow depth and the AMSU scattering signatures in the 23-150 GHz window region showed weak correlation, deteriorated by the dependence of these signatures on snow metamorphism. The lower frequency scattering index, computed as the difference in the brightness temperature between 23 and 31 GHz channels, was low and insensitive to fresh snow predominant in December, but increased later in the season, and thus was more sensitive to snow depth for older snow cover. However, this seasonal increase in microwave scattering was observed for every snow depth range, suggesting a strong dependence on snow metamorphism. In contrast, the 89 GHz scattering index responded to relatively shallow snow cover in December, but was less sensitive to snow depth variability later in the season. A snow hydrology model was applied at specific locations to estimate snow water equivalent (other than snow depth) for comparisons with the AMSU measurements. Overall, the lower frequency index was the best predictor of snow water equivalent and snow depth. However, correlation was higher for snow density and snow water equivalent. This was attributed to the response of this scattering index to the grain size evolution with time, which correlated better with the snow density and water equivalent changes in the snow cover than snow depth. Correlation between the snow water equivalent and the lower frequency index for fresh snow cover was significantly improved by switching to the higher frequency index at 89 GHz as predictor when the lower frequency index at 31 GHz was less than the 5 K threshold. Correlation further improved for fresh snow cover

  3. Behaviors of the percentage depth dose curves along the beam axis of a phantom filled with different clinical PTO objects, a Monte Carlo Geant4 study

    NASA Astrophysics Data System (ADS)

    EL Bakkali, Jaafar; EL Bardouni, Tarek; Safavi, Seyedmostafa; Mohammed, Maged; Saeed, Mroan

    2016-08-01

    The aim of this work is to assess the capabilities of Monte Carlo Geant4 code to reproduce the real percentage depth dose (PDD) curves generated in phantoms which mimic three important clinical treatment situations that include lung slab, bone slab, bone-lung slab geometries. It is hoped that this work will lead us to a better understanding of dose distributions in an inhomogeneous medium, and to identify any limitations of dose calculation algorithm implemented in the Geant4 code. For this purpose, the PDD dosimetric functions associated to the three clinical situations described above, were compared to one produced in a homogeneous water phantom. Our results show, firstly, that the Geant4 simulation shows potential mistakes on the shape of the calculated PDD curve of the first physical test object (PTO), and it is obviously not able to successfully predict dose values in regions near to the boundaries between two different materials. This is, surely due to the electron transport algorithm and it is well-known as the artifacts at interface phenomenon. To deal with this issue, we have added and optimized the StepMax parameter to the dose calculation program; consequently the artifacts due to the electron transport were quasi disappeared. However, the Geant4 simulation becomes painfully slow when we attempt to completely resolve the electron artifact problems by considering a smaller value of an electron StepMax parameter. After electron transport optimization, our results demonstrate the medium-level capabilities of the Geant4 code to modeling dose distribution in clinical PTO objects.

  4. The role of depth in regulating water quality and fish assemblages in oxbow lakes

    USGS Publications Warehouse

    Goetz, Daniel B.; Miranda, Leandro E.; Kroger, Robert; Andrews, Caroline S.

    2015-01-01

    We evaluated water quality and fish assemblages in deep (> 3.0 m; N = 7) and shallow (< 1.5 m; N = 6) floodplain lakes in the intensively cultivated Yazoo River Basin (Mississippi, USA) using indirect gradient multivariate procedures. Shallow lakes displayed wide diel oxygen fluctuations, some reaching hypoxic/anoxic conditions for extended periods of time, high suspended solids, and extreme water temperatures. Conversely, deeper lakes were represented by higher visibility, stable oxygen levels, and cooler water temperatures. Fish assemblages in shallow lakes were dominated by tolerant, small-bodied fishes and those able to breathe atmospheric oxygen. Deeper lakes had a greater representation of predators and other large-bodied fishes. Our evaluation suggests fish assemblages are reflective of oxbow lakes water quality, which is shaped by depth. Understanding the interactions between depth, water quality, and fish assemblages may facilitate development of effective management plans for improving conditions necessary to sustain diverse fish assemblages in agriculturally dominated basins.

  5. Measurements of total column ozone, precipitable water content and aerosol optical depth at Sofia

    NASA Astrophysics Data System (ADS)

    Kaleyna, P.; Kolev, N.; Savov, P.; Evgenieva, Ts.; Danchovski, V.; Muhtarov, P.

    2016-03-01

    This article reports the results of a study related to variations in total ozone content, aerosol optical depth, water vapor content and Ångström coefficients from summer campaign carried out in June-July 2014, at two sites in the city of Sofia (Astronomical Observatory in the Borisova Gradina Park and National Institute of Geophysics, Geodesy and Geography (NIGGG)). The results of data analysis indicate the following: Spectral dependence of aerosol optical depth (AOD); Greater AOD values due to greater portion of aerosols; Inverse relationship between the time variations of AOD or water vapor and ozone.

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

    USGS Publications Warehouse

    Austin, Jane E.; Buhl, Deborah A.

    2011-01-01

    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.

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

    USGS Publications Warehouse

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

    1999-01-01

    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.

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

    PubMed Central

    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

    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

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

    SciTech Connect

    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.

    2013-04-15

    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

  10. MCNP simulation of radiation doses distributions in a water phantoms simulating interventional radiology patients

    NASA Astrophysics Data System (ADS)

    He, Wenjun; Mah, Eugene; Huda, Walter; Selby, Bayne; Yao, Hai

    2011-03-01

    Purpose: To investigate the dose distributions in water cylinders simulating patients undergoing Interventional Radiological examinations. Method: The irradiation geometry consisted of an x-ray source, dose-area-product chamber, and image intensifier as currently used in Interventional Radiology. Water cylinders of diameters ranging between 17 and 30 cm were used to simulate patients weighing between 20 and 90 kg. X-ray spectra data with peak x-ray tube voltages ranging from 60 to 120 kV were generated using XCOMP3R. Radiation dose distributions inside the water cylinder (Dw) were obtained using MCNP5. The depth dose distribution along the x-ray beam central axis was normalized to free-in-air air kerma (AK) that is incident on the phantom. Scattered radiation within the water cylinders but outside the directly irradiated region was normalized to the dose at the edge of the radiation field. The total absorbed energy to the directly irradiated volume (Ep) and indirectly irradiated volume (Es) were also determined and investigated as a function of x-ray tube voltage and phantom size. Results: At 80 kV, the average Dw/AK near the x-ray entrance point was 1.3. The ratio of Dw near the entrance point to Dw near the exit point increased from ~ 26 for the 17 cm water cylinder to ~ 290 for the 30 cm water cylinder. At 80 kV, the relative dose for a 17 cm water cylinder fell to 0.1% at 49 cm away from the central ray of the x-ray beam. For a 30 cm water cylinder, the relative dose fell to 0.1% at 53 cm away from the central ray of the x-ray beam. At a fixed x-ray tube voltage of 80 kV, increasing the water cylinder diameter from 17 to 30 cm increased the Es/(Ep+Es) ratio by about 50%. At a fixed water cylinder diameter of 24 cm, increasing the tube voltage from 60 kV to 120 kV increased the Es/(Ep+Es) ratio by about 12%. The absorbed energy from scattered radiation was between 20-30% of the total energy absorbed by the water cylinder, and was affected more by patient size

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

    PubMed

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

    1999-06-01

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

  12. Soil Water Content Sensors as a Method of Measuring Ice Depth

    NASA Astrophysics Data System (ADS)

    Whitaker, E.; Reed, D. E.; Desai, A. R.

    2015-12-01

    Lake ice depth provides important information about local and regional climate change, weather patterns, and recreational safety, as well as impacting in situ ecology and carbon cycling. However, it is challenging to measure ice depth continuously from a remote location, as existing methods are too large, expensive, and/or time-intensive. Therefore, we present a novel application that reduces the size and cost issues by using soil water content reflectometer sensors. Analysis of sensors deployed in an environmental chamber using a scale model of a lake demonstrated their value as accurate measures of the change in ice depth over any time period, through measurement of the liquid-to-solid phase change. A robust correlation exists between volumetric water content in time as a function of environmental temperature. This relationship allows us to convert volumetric water content into ice depth. An array of these sensors will be placed in Lake Mendota, Madison, Wisconsin in winter 2015-2016, to create a temporally high-resolution ice depth record, which will be used for ecological or climatological studies while also being transmitted to the public to increase recreational safety.

  13. Attenuation properties and percentage depth dose of tannin-based Rhizophora spp. particleboard phantoms using computed tomography (CT) and treatment planning system (TPS) at high energy x-ray beams

    NASA Astrophysics Data System (ADS)

    Yusof, M. F. Mohd; Abdullah, R.; Tajuddin, A. A.; Hashim, R.; Bauk, S.

    2016-01-01

    A set of tannin-based Rhizophora spp. particleboard phantoms with dimension of 30 cm x 30 cm was fabricated at target density of 1.0 g/cm3. The mass attenuation coefficient of the phantom was measured using 60Co gamma source. The phantoms were scanned using Computed Tomography (CT) scanner and the percentage depth dose (PDD) of the phantom was calculated using treatment planning system (TPS) at 6 MV and 10 MV x-ray and compared to that in solid water phantoms. The result showed that the mass attenuation coefficient of tannin-based Rhizohora spp. phantoms was near to the value of water with χ2 value of 1.2. The measured PDD also showed good agreement with solid water phantom at both 6 MV and 10 MV x-ray with percentage deviation below 8% at depth beyond the maximum dose, Zmax.

  14. 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....

  15. 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...

  16. Growth and Physiological Responses to Water Depths in Carex schmidtii Meinsh

    PubMed Central

    Yan, Hong; Liu, Ruiquan; Liu, Zinan; Wang, Xue; Luo, Wenbo; Sheng, Lianxi

    2015-01-01

    A greenhouse experiment was performed to investigate growth and physiological responses to water depth in completely submerged condition of a wetland plant Carex schmidtii Meinsh., one of the dominant species in the Longwan Crater Lake wetlands (China). Growth and physiological responses of C. schmidtii were investigated by growing under control (non-submerged) and three submerged conditions (5 cm, 15 cm and 25 cm water level). Total biomass was highest in control, intermediate in 5 cm treatment and lowest in the other two submerged treatments. Water depth prominently affected the first-order lateral root to main root mass ratio. Alcohol dehydrogenase (ADH) activity decreased but malondialdehyde (MDA) content increased as water depth increased. The starch contents showed no differences among the various treatments at the end of the experiment. However, soluble sugar contents were highest in control, intermediate in 5 cm and 15 cm treatments and lowest in 25 cm treatment. Our data suggest that submergence depth affected some aspects of growth and physiology of C. schmidtii, which can reduce anoxia damage not only through maintaining the non-elongation strategy in shoot part but also by adjusting biomass allocation to different root orders rather than adjusting root-shoot biomass allocation. PMID:26009895

  17. A unit for collection of dissolved oxygen and water column temperature at multiple depths

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A 2004 field study conducted during actual channel catfish Ictalurus punctatus harvests, and a small-scale research study conducted in 2005, required continuous collection of dissolved oxygen concentration and temperature at two depths in the water column. The on-farm study required data collection...

  18. SU-E-T-499: Comparison of Measured Tissue Phantom Ratios (TPR) Against Calculated From Percent Depth Doses (PDD) with and Without Peak Scatter Factor (PSF) in 6MV Open Beam

    SciTech Connect

    Narayanasamy, G; Cruz, W; Gutierrez, Alonso; Mavroidis, Panayiotis; Papanikolaou, N; Stathakis, S; Breton, C

    2014-06-01

    Purpose: To examine the accuracy of measured tissue phantom ratios (TPR) values with TPR calculated from percentage depth dose (PDD) with and without peak scatter fraction (PSF) correction. Methods: For 6MV open beam, TPR and PDD values were measured using PTW Semiflex (31010) ionization field and reference chambers (0.125cc volume) in a PTW MP3-M water tank. PDD curves were measured at SSD of 100cm for 7 square fields from 3cm to 30cm. The TPR values were measured up to 22cm depth for the same fields by continuous water draining method with ionization chamber static at 100cm from source. A comparison study was performed between the (a) measured TPR, (b) TPR calculated from PDD without PSF, (c) TPR calculated from PDD with PSF and (d) clinical TPR from RadCalc (ver 6.2, Sun Nuclear Corp). Results: There is a field size, depth dependence on TPR values. For 10cmx10cm, the differences in surface dose (DDs), dose at 10cm depth (DD10) <0.5%; differences in dmax (Ddmax) <2mm for the 4 methods. The corresponding values for 30cmx30cm are DDs, DD10 <0.2% and Ddmax<3mm. Even though for 3cmx3cm field, DDs and DD10 <1% and Ddmax<1mm, the calculated TPR values with and without PSF correction differed by 2% at >20cm depth. In all field sizes at depths>28cm, (d) clinical TPR values are larger than that from (b) and (c) by >3%. Conclusion: Measured TPR in method (a) differ from calculated TPR in methods (b) and (c) to within 1% for depths < 28cm in all 7 fields in open 6MV beam. The dmax values are within 3mm of each other. The largest deviation of >3% was observed in clinical TPR values in method (d) for all fields at depths < 28cm.

  19. Vegetative Propagule Pressure and Water Depth Affect Biomass and Evenness of Submerged Macrophyte Communities

    PubMed Central

    Li, Hong-Li; Wang, Yong-Yang; Zhang, Qian; Wang, Pu; Zhang, Ming-Xiang; Yu, Fei-Hai

    2015-01-01

    Vegetative propagule pressure may affect the establishment and structure of aquatic plant communities that are commonly dominated by plants capable of clonal growth. We experimentally constructed aquatic communities consisting of four submerged macrophytes (Hydrilla verticillata, Ceratophyllum demersum, Elodea nuttallii and Myriophyllum spicatum) with three levels of vegetative propagule pressure (4, 8 and 16 shoot fragments for communities in each pot) and two levels of water depth (30 cm and 70 cm). Increasing vegetative propagule pressure and decreasing water level significantly increased the growth of the submerged macrophyte communities, suggesting that propagule pressure and water depth should be considered when utilizing vegetative propagules to re-establish submerged macrophyte communities in degraded aquatic ecosystems. However, increasing vegetative propagule pressure and decreasing water level significantly decreased evenness of the submerged macrophyte communities because they markedly increased the dominance of H. verticillata and E. nuttallii, but had little impact on that of C. demersum and M. spicatum. Thus, effects of vegetative propagule pressure and water depth are species-specific and increasing vegetative propagule pressure under lower water level can facilitate the establishment success of submerged macrophyte communities. PMID:26560705

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

    SciTech Connect

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

    1992-08-01

    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.

  1. SU-E-T-562: Scanned Percent Depth Dose Curve Discrepancy for Photon Beams with Physical Wedge in Place (Varian IX) Using Different Sensitive Volume Ion Chambers

    SciTech Connect

    Zhao, H; Sarkar, V; Rassiah-Szegedi, P; Huang, Y; Szegedi, M; Huang, L; Salter, B

    2014-06-01

    Purpose: To investigate and report the discrepancy of scanned percent depth dose (PDD) for photon beams with physical wedge in place when using ion chambers with different sensitive volumes. Methods/Materials: PDD curves of open fields and physical wedged fields (15, 30, 45, and 60 degree wedge) were scanned for photon beams (6MV and 10MV, Varian iX) with field size of 5x5 and 10x10 cm using three common scanning chambers with different sensitive volumes - PTW30013 (0.6cm3), PTW23323 (0.1cm3) and Exradin A16 (0.007cm3). The scanning system software used was OmniPro version 6.2, and the scanning water tank was the Scanditronix Wellhoffer RFA 300.The PDD curves from the three chambers were compared. Results: Scanned PDD curves of the same energy beams for open fields were almost identical between three chambers, but the wedged fields showed non-trivial differences. The largest differences were observed between chamber PTW30013 and Exradin A16. The differences increased as physical wedge angle increased. The differences also increased with depth, and were more pronounced for 6MV beam. Similar patterns were shown for both 5x5 and 10x10 cm field sizes. For open fields, all PDD values agreed with each other within 1% at 10cm depth and within 1.62% at 20 cm depth. For wedged fields, the difference of PDD values between PTW30013 and A16 reached 4.09% at 10cm depth, and 5.97% at 20 cm depth for 6MV with 60 degree physical wedge. Conclusion: We observed a significant difference in scanned PDD curves of photon beams with physical wedge in place obtained when using different sensitive volume ion chambers. The PDD curves scanned with the smallest sensitive volume ion chamber showed significant difference from larger chamber results, beyond 10cm depth. We believe this to be caused by varying response to beam hardening by the wedges.

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

    PubMed

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

    2010-10-14

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

  3. Ground-water contribution to dose from past Hanford Operations

    SciTech Connect

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

    1992-08-01

    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.

  4. Oblique wave-free potentials for water waves in constant finite depth

    NASA Astrophysics Data System (ADS)

    Maiti, Rajdeep; Basu, Uma; Mandal, B. N.

    2015-06-01

    In this paper, a method to construct oblique wave-free potentials in the linearised theory of water waves for water with uniform finite depth is presented in a systematic manner. The water has either a free surface or an ice-cover modelled as a thin elastic plate. For the case of free surface, the effect of surface tension may be neglected or taken into account. Here, the wave-free potentials are singular solutions of the modified Helmholtz equation, having singularity at a point in the fluid region and they satisfy the conditions at the upper surface and the bottom of water region and decay rapidly away from the point of singularity. These are useful in obtaining solutions to oblique water wave problems involving bodies with circular cross-sections such as long horizontal cylinders submerged or half-immersed in water of uniform finite depth with a free surface or an ice-cover modelled as a floating elastic plate. Finally, the forms of the upper surface related to the wave-free potentials constructed here are depicted graphically in a number of figures to visualize the wave motion. The results for non-oblique wave-free potentials and the upper surface wave-free potentials are obtained. The wave-free potentials constructed here will be useful in the mathematical study of water wave problems involving infinitely long horizontal cylinders, either half-immersed or completely immersed in water.

  5. The Depths of Hydraulic Fracturing and Accompanying Water Use Across the United States.

    PubMed

    Jackson, Robert B; Lowry, Ella R; Pickle, Amy; Kang, Mary; DiGiulio, Dominic; Zhao, Kaiguang

    2015-08-01

    Reports highlight the safety of hydraulic fracturing for drinking water if it occurs "many hundreds of meters to kilometers underground". To our knowledge, however, no comprehensive analysis of hydraulic fracturing depths exists. Based on fracturing depths and water use for ∼44,000 wells reported between 2010 and 2013, the average fracturing depth across the United States was 8300 ft (∼2500 m). Many wells (6900; 16%) were fractured less than a mile from the surface, and 2600 wells (6%) were fractured above 3000 ft (900 m), particularly in Texas (850 wells), California (720), Arkansas (310), and Wyoming (300). Average water use per well nationally was 2,400,000 gallons (9,200,000 L), led by Arkansas (5,200,000 gallons), Louisiana (5,100,000 gallons), West Virginia (5,000,000 gallons), and Pennsylvania (4,500,000 gallons). Two thousand wells (∼5%) shallower than one mile and 350 wells (∼1%) shallower than 3000 ft were hydraulically fractured with >1 million gallons of water, particularly in Arkansas, New Mexico, Texas, Pennsylvania, and California. Because hydraulic fractures can propagate 2000 ft upward, shallow wells may warrant special safeguards, including a mandatory registry of locations, full chemical disclosure, and, where horizontal drilling is used, predrilling water testing to a radius 1000 ft beyond the greatest lateral extent. PMID:26196164

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

    USGS Publications Warehouse

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

    2006-01-01

    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.

  7. Effects of the tissue-air interface in calculations of beta-particle skin dose at a depth of 70 microns.

    PubMed

    Crawford, O H; Turner, J E; Hamm, R N; Ashley, J C

    1991-11-01

    The effects that the tissue-air interface has on the basal-layer dose at a depth of 70 microns from beta emitters on the skin surface are studied using Monte Carlo calculations. The dose is decreased at small lateral distances from a point source but is increased at large distances. PMID:1752748

  8. Direct absorbed dose to water determination based on water calorimetry in scanning proton beam delivery

    SciTech Connect

    Sarfehnia, A.; Clasie, B.; Chung, E.; Lu, H. M.; Flanz, J.; Cascio, E.; Engelsman, M.; Paganetti, H.; Seuntjens, J.

    2010-07-15

    Purpose: The aim of this manuscript is to describe the direct measurement of absolute absorbed dose to water in a scanned proton radiotherapy beam using a water calorimeter primary standard. Methods: The McGill water calorimeter, which has been validated in photon and electron beams as well as in HDR {sup 192}Ir brachytherapy, was used to measure the absorbed dose to water in double scattering and scanning proton irradiations. The measurements were made at the Massachusetts General Hospital proton radiotherapy facility. The correction factors in water calorimetry were numerically calculated and various parameters affecting their magnitude and uncertainty were studied. The absorbed dose to water was compared to that obtained using an Exradin T1 Chamber based on the IAEA TRS-398 protocol. Results: The overall 1-sigma uncertainty on absorbed dose to water amounts to 0.4% and 0.6% in scattered and scanned proton water calorimetry, respectively. This compares to an overall uncertainty of 1.9% for currently accepted IAEA TRS-398 reference absorbed dose measurement protocol. The absorbed dose from water calorimetry agrees with the results from TRS-398 well to within 1-sigma uncertainty. Conclusions: This work demonstrates that a primary absorbed dose standard based on water calorimetry is feasible in scattered and scanned proton beams.

  9. (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

    Brunzendorf, Jens

    2012-08-01

    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

  10. Depth conversion in rapidly deepening water with application to the Seychelles

    SciTech Connect

    Davis, B.K.; Binks, R.

    1994-12-31

    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.

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

    USGS Publications Warehouse

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

    2010-01-01

    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

  12. SU-E-T-589: A Comparison of Field Size Dependence of Electron Depth Dose From Different Linacs

    SciTech Connect

    Kim, M; Zhu, T

    2014-06-01

    Purpose: For accurate dose calculation in electron beam therapy, it is important to know the percentage depth dose (PDD) for each beam. This can vary depending on the machine make and model and the field size. Three different linear accelerators were compared in this study. Methods: PDD data was collected for different output beam energies and different field sizes for three different linear accelerators (Siemens Primus, Varian 2300ix, Varian Truebeam). Data was compared for the same energy with the same field size to see if the PDD differed among manufacturers. Furthermore, PDD was compared for different field sizes of the same machine at the same energy. Results: For the same beam energy and the same field size, the PDD curves were comparable for the three linacs with variations within 13%. PDD curves for different field sizes and beam energies were compared to verify this result. At higher beam energies, the disagreement between PDD curves is more pronounced between different field sizes for all three of the linacs compared. Conclusions: For the same energy and field size, the variation between different machines was within 13%. For the same manufacturer (Varian Clinac 2300ix and Truebeam), the agreement is within 3% with a standard deviation of less than 2.5%. PDD curves for different field sizes for the same energy were also investigated for the three linacs.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    Water table depth is the key parameter controlling the fluxes of CO2, CH4 and N2O from organic soils (peatlands and other organic soils). Therefore, a good estimation of the spatial distribution of water table depth is crucial in any upscaling approach for these greenhouse gases (GHGs). It is further the prerequisite to assess the effects of re-wetting measures. There are attempts to obtain maps of water table depth at large scales (e.g. national or continental) by using process-based hydrological model concepts. However, major problem of the process-based approach is the representation of the water management (ditches, tile drains, pumping and weir management), which is at the best known spatially just for the ditch patterns. Thus, this approach is hardly applicable to the diversely-drained and -used organic soils in central Europe. Here, we present an alternative, data-driven approach for upscaling annual mean and dynamics of water table depth in organic soils. Groundwater level data of a unique dataset from about 60 peatlands, 1100 dipwells and around 8000 annual data sets, is the basis of this approach. Time series were used to calculate long-term annual means, average annual amplitudes and ponding durations. In case of continuous observations, shape parameters of the annual frequency distribution of water table depths were calculated. For each well, numerous site characteristics were collected as possible explanatory variables. This collection was restricted to nationally-available data. For each dipwell, land use is taken from official land use maps (German database ATKIS), and the soil type from the national geological map (1:200.000). In case of reliable site information, maps were corrected accordingly. Additionally, from these maps, topological indicators such as the ditch distance and density, the distance to the edge of the peatland and the peatland area within different buffers were calculated. Meteorological data (precipitation, potential

  14. Influence of Water Table Depth on Pore Water Chemistry and Trihalomethane Formation Potential in Peatlands.

    PubMed

    Gough, Rachel; Holliman, Peter J; Fenner, Nathalie; Peacock, Mike; Freeman, Christopher

    2016-02-01

    Drained peatland catchments are reported to produce more colored, dissolved organic carbon (DOC)-rich water, presenting problems for potable water treatment. The blocking of peatland drainage ditches to restore the water table is increasingly being considered as a strategy to address this deterioration in water quality. However, the effect of ditch blocking on the potential of DOC to form trihalomethanes (THMs) has not been assessed. In this study, the effect of peat rewetting on pore water DOC concentration and characteristics (including THM formation potential [THMFP]) was assessed over 12 months using peat cores collected from two drained peatland sites. The data show little evidence of differences in DOC concentration or characteristics between the different treatments. The absence of any difference in the THMFP of pore water between treatments suggests that, in the short term at least, ditch blocking may not have an effect on the THMFP of waters draining peatland catchments. PMID:26803099

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

    NASA Astrophysics Data System (ADS)

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

    2009-05-01

    There are millions of wetlands in shallow depressions on the North American prairies but the quantity of water stored in these depressions remains poorly understood. Hayashi and van der Kamp (2000) used the relationship between volume (V), area (A) and depth (h) to develop an equation for estimating wetland storage. We tested the robustness of their full and simplified V-A-h methods to accurately estimate volume for the range of wetland shapes occurring across the Prairie Pothole Region. These results were contrasted with two commonly implemented V-A regression equations to determine which method estimates volume most accurately. We used detailed topographic data for 27 wetlands in Smith Creek and St. Denis watersheds, Saskatchewan that ranged in surface area and basin shape. The full V-A-h method was found to accurately estimate storage (errors <3%) across wetlands of various shapes, and is therefore suitable for calculating water storage in the variety of wetland surface shapes found in the prairies. Both V-A equations performed poorly, with volume underestimated by an average of 15% and 50% Analysis of the simplified V-A-h method showed that volume errors of <10% can be achieved if the basin and shape coefficients are derived properly. This would involve measuring depth and area twice, with sufficient time between measurements that the natural fluctuations in water storage are reflected. Practically, wetland area and depth should be measured in spring, following snowmelt when water levels are near the peak, and also in late summer prior to water depths dropping below 10 cm. These guidelines for applying the simplified V-A-h method will allow for accurate volume estimations when detailed topographic data are not available. Since the V-A equations were outperformed by the full and simplified V-A-h methods, we conclude that wetland depth and basin morphology should be considered when estimating volume. This will improve storage estimations of natural and human

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

    SciTech Connect

    Bierwirth, P.N.; Lee, T.J.; Burne, R.V. Michigan Environmental Research Inst., Ann Arbor )

    1993-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Vassilakos, Gregory J.

    2014-01-01

    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.

  19. Spatio-temporal representativeness of euphotic depth in situ sampling in transitional coastal waters

    NASA Astrophysics Data System (ADS)

    Luhtala, Hanna; Tolvanen, Harri

    2016-06-01

    In dynamic coastal waters, the representativeness of spot sampling is limited to the measurement time and place due to local heterogeneity and irregular water property fluctuations. We assessed the representativeness of in situ sampling by analysing spot-sampled depth profiles of photosynthetically active radiation (PAR) in dynamic coastal archipelago waters in the south-western Finnish coast of the Baltic Sea. First, we assessed the role of spatio-temporality within the underwater light dynamics. As a part of this approach, an anomaly detection procedure was tested on a dataset including a large archipelago area and extensive temporal coverage throughout the ice-free season. The results suggest that euphotic depth variability should be treated as a spatio-temporal process rather than considering spatial and temporal dimensions separately. Second, we assessed the representativeness of spot sampling through statistical analysis of comparative data from spatially denser sampling on three test sites on two optically different occasions. The datasets revealed variability in different dimensions and scales. The suitability of a dataset to reveal wanted phenomena can usually be improved by careful planning and by clearly defining the data sampling objectives beforehand. Nonetheless, conducting a sufficient in situ sampling in dynamic coastal area is still challenging: detecting the general patterns at all the relevant dimensions is complicated by the randomness effect, which reduces the reliability of spot samples on a more detailed scale. Our results indicate that good representativeness of a euphotic depth sampling location is not a stable feature in a highly dynamic environment.

  20. Using Baseflow to Constrain Water Table Depth Simulations in the NCAR Community Land Model (CLM)

    NASA Astrophysics Data System (ADS)

    Lo, M.; Yeh, P.; Famiglietti, J.

    2007-12-01

    Several recent studies have shown the importance of representing groundwater in land surface hydrologic simulations. However, optimal methods for model calibration in order to realistically simulate baseflow and groundwater depth have received little attention. Moreover, due to model parameter interactions, various parameter combinations are found to exhibit equifinality in simulated total runoff. In this study a simple lumped groundwater model was incorporated into the Community Land Model (CLM), in which the water table is interactively coupled to soil moisture through the groundwater recharge fluxes. The coupled model (CLMGW) is successfully validated in Illinois against a 22-year (1984~2005) monthly observational dataset. The advantage obtained from incorporating baseflow calibration in addition to traditional calibration based on measured streamflow alone is demonstrated. Using the optimal Pareto parameter sets identified from baseflow and total flow calibration, the flow partitioning and water table depth simulation by the CLMGW are improved, and the equifinality problem is alleviated. For other regions that lack observations of water table depth, the baseflow estimates can be used to enhance parameter estimation. The calibrated CLMGW is applied to the entire US to study the impact of groundwater on land hydrologic memory.

  1. Modeling relationships between water table depth and peat soil carbon loss in Southeast Asian plantations

    NASA Astrophysics Data System (ADS)

    Carlson, Kimberly M.; Goodman, Lael K.; May-Tobin, Calen C.

    2015-07-01

    Plantation-associated drainage of Southeast Asian peatlands has accelerated in recent years. Draining exposes the upper peat layer to oxygen, leading to elevated decomposition rates and net soil carbon losses. Empirical studies indicate positive relationships between long-term water table (WT) depth and soil carbon loss rate in peatlands. These correlations potentially enable using WT depth as a proxy for soil carbon losses from peatland plantations. Here, we compile data from published research assessing WT depth and carbon balance in tropical plantations on peat. We model net carbon loss from subsidence studies, as well as soil respiration (heterotrophic and total) from closed chamber studies, as a function of WT depth. WT depth across all 12 studies and 59 sites is 67 ± 20 cm (mean ± standard deviation). Mean WT depth is positively related to net carbon loss, as well as soil respiration rate. Our models explain 45% of net carbon loss variation and 45-63% of soil respiration variation. At a 70 cm WT depth, the subsidence model suggests net carbon loss of 20 tC ha-1 yr-1 (95% confidence interval (CI) 18-22 tC ha-1 yr-1) for plantations drained for >2 yr. Closed chamber-measured total soil respiration at this depth is 20 tC-CO2 ha-1 yr-1 (CI 17-24 tC-CO2 ha-1 yr-1) while heterotrophic respiration is 17 tC-CO2 ha-1 yr-1 (CI 14-20 tC-CO2 ha-1 yr-1), ˜82% of total respiration. While land use is not a significant predictor of soil respiration, WT depths are greater at acacia (75 ± 16 cm) than oil palm (59 ± 15 cm) sample sites. Improved spatio-temporal sampling of the full suite of peat soil carbon fluxes—including fluvial carbon export and organic fertilizer inputs—will clarify multiple mechanisms leading to carbon loss and gain, supporting refined assessments of the global warming potential of peatland drainage.

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

  3. Testing peatland water-table depth transfer functions using high-resolution hydrological monitoring data

    NASA Astrophysics Data System (ADS)

    Swindles, Graeme T.; Holden, Joseph; Raby, Cassandra L.; Turner, T. Edward; Blundell, Antony; Charman, Dan J.; Menberu, Meseret Walle; Kløve, Bjørn

    2015-07-01

    Transfer functions are now commonly used to reconstruct past environmental variability from palaeoecological data. However, such approaches need to be critically appraised. Testate amoeba-based transfer functions are an established method for the quantitative reconstruction of past water-table variations in peatlands, and have been applied to research questions in palaeoclimatology, peatland ecohydrology and archaeology. We analysed automatically-logged peatland water-table data from dipwells located in England, Wales and Finland and a suite of three year, one year and summer water-table statistics were calculated from each location. Surface moss samples were extracted from beside each dipwell and the testate amoebae community composition was determined. Two published transfer functions were applied to the testate-amoeba data for prediction of water-table depth (England and Europe). Our results show that estimated water-table depths based on the testate amoeba community reflect directional changes, but that they are poor representations of the real mean or median water-table magnitudes for the study sites. We suggest that although testate amoeba-based reconstructions can be used to identify past shifts in peat hydrology, they cannot currently be used to establish precise hydrological baselines such as those needed to inform management and restoration of peatlands. One approach to avoid confusion with contemporary water-table determinations is to use residuals or standardised values for peatland water-table reconstructions. We contend that our test of transfer functions against independent instrumental data sets may be more powerful than relying on statistical testing alone.

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

    NASA Astrophysics Data System (ADS)

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

    2002-11-01

    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 χ2 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.

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

    SciTech Connect

    Moyers, M. F.; Vatnitsky, A. S.; Vatnitsky, S. M.

    2011-10-15

    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.

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

    SciTech Connect

    Arjomandy, Bijan; Tailor, Ramesh; Zhao Li; Devic, Slobodan

    2012-02-15

    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.

  7. Sensible heat measurements indicating depth and magnitude of subsurface soil water evaporation

    NASA Astrophysics Data System (ADS)

    Heitman, J. L.; Xiao, X.; Horton, R.; Sauer, T. J.

    2008-04-01

    Most measurement approaches for determining evaporation assume that the latent heat flux originates from the soil surface. Here, a new method is described for determining in situ soil water evaporation dynamics from fine-scale measurements of soil temperature and thermal properties with heat pulse sensors. A sensible heat balance is computed using soil heat flux density at two depths and change in sensible heat storage in between; the sensible heat balance residual is attributed to latent heat from evaporation of soil water. Comparisons between near-surface soil heat flux density and Bowen ratio energy balance measurements suggest that evaporation originates below the soil surface several days after rainfall. The sensible heat balance accounts for this evaporation dynamic in millimeter-scale depth increments within the soil. Comparisons of sensible heat balance daily evaporation estimates to Bowen ratio and mass balance estimates indicate strong agreement (r2 = 0.96, root-mean-square error = 0.20 mm). Potential applications of this technique include location of the depth and magnitude of subsurface evaporation fluxes and estimation of stage 2-3 daily evaporation without requirements for large fetch. These applications represent new contributions to vadose zone hydrology.

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

    NASA Astrophysics Data System (ADS)

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

    2011-01-01

    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 (ψ) 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 ψR1--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 ψR1 can be generalized as a noninvasive optical proxy for screening depth changes on subsurface optical layers.

  9. Historical Tracking of Nitrate in Contrasting Vineyard Using Water Isotopes and Nitrate Depth Profiles

    NASA Astrophysics Data System (ADS)

    Sprenger, M.; Erhardt, M.; Riedel, M.; Weiler, M.

    2015-12-01

    The European Water Framework Directive (EWFD) aims to achieve a good chemical status for the groundwater bodies in Europe by the year 2015. Despite the effort to reduce the nitrate pollution from agriculture within the last two decades, there are still many groundwater aquifers that exceed nitrate concentrations above the EWFD threshold of 50 mg/l. Viticulture is seen as a major contributor of nitrate leaching and sowing of a green cover was shown to have a positive effect on lowering the nitrate loads in the upper 90 cm of the soil. However, the consequences for nitrate leaching into the subsoil were not yet tested. We analyzed the nitrate concentrations and pore water stable isotope composition to a depth of 380 cm in soil profiles under an old vineyard and a young vineyard with either soil tillage or permanent green cover in between the grapevines. The pore water stable isotopes were used to calibrate a soil physical model, which was then used to infer the age of the soil water at different depths. This way, we could relate elevated nitrate concentrations below an old vineyard to tillage processes that took place during the winter two years before the sampling. We further showed that the elevated nitrate concentration in the subsoil of a young vineyard can be related to the soil tillage prior to the planting of the new vineyard. If the soil is kept bare due to tillage, a nitrate concentration of 200 kg NO3--N/ha is found in 290 to 380 cm depth 2.5 years after the installation of the vineyard. The amount of nitrate leaching is considerably reduced due to a seeded green cover between the grapevines that takes up a high share of the mobilized nitrate reducing a potential contamination of the groundwater.

  10. Determining the depth of a sound source in shallow water against intense background noise

    NASA Astrophysics Data System (ADS)

    Besedina, T. N.; Kuznetsov, G. N.; Kuz'kin, V. M.; Pereselkov, S. A.

    2015-11-01

    We consider a method for estimating the depth of a sound source in a shallow water acoustic waveguide for a weak signal, based on information on the ratio of the amplitude of neighboring modes of the wave field. Results of a numerical experiment using a single receiver and a horizontal linear array in the lowfrequency region are given. We demonstrate the stability of the method to errors in measuring the amplitudes of filtered modes and variations of the waveguide model, as well as high noise immunity. It is established that the error in reconstructing the depth of a source with increasing noise tends to the established value. We give a qualitative and quantitative explanation of the simulation results.

  11. Rooting depth: a key trait connecting water and carbon metabolism of trees

    NASA Astrophysics Data System (ADS)

    Savi, Tadeja; Dal Borgo, Anna; Casolo, Valentino; Bressan, Alice; Stenni, Barbara; Zini, Luca; Bertoncin, Paolo; Nardini, Andrea

    2015-04-01

    Drought episodes accompanied by heat waves are thought to be the main cause of increasing rates of tree decline and mortality in several biomes with consequent ecological/economical consequences. Three possible and not mutually exclusive mechanisms have been proposed to be the drivers of this phenomenon: hydraulic failure caused by massive xylem cavitation and leading to strong reduction of root-to-leaf water transport, carbon starvation caused by prolonged stomatal closure and leading to impairment of primary and secondary metabolism, and finally attacks of biotic agents. The different mechanisms have been reported to have different relevance in the different species. We analyzed the seasonal changes of water relations, xylem sap isotopic composition, and concentration of non-structural carbohydrates in four different woody species co-occurring in the same habitat during a summer drought. Analysis of rain and deep soil water isotopic composition were also performed. Different species showed differential access to deep water sources which influences the gas exchanges and the concentration of non structural carbohydrates (NSC) during the dry season. Species with access to deeper water maintained higher NSC content and were also able to better preserve the integrity of the water transport pathway. On the basis of our results, we propose that rooting depth is a key trait connecting water and carbon plant metabolism, thus mediating the likelihood of hydraulic failure vs carbon starvation in trees subjected to global warming.

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

    USGS Publications Warehouse

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

    2001-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    Bulk density is a fundamental property of snow relating its depth and mass. Previously, two simple models of bulk density (depending on snow depth, date, and location) have been developed to convert snow depth observations to snow water equivalent (SWE) estimates. However, these models were not intended for application at the daily time step. We develop a new model of bulk density for the daily time step and demonstrate its improved skill over the existing models. Snow depth and density are negatively correlated at short (10 days) timescales while positively correlated at longer (90 days) timescales. We separate these scales of variability by modeling smoothed, daily snow depth (long timescales) and the observed positive and negative anomalies from the smoothed time series (short timescales) as separate terms. A climatology of fit is also included as a predictor variable. Over half a million daily observations of depth and SWE at 345 snowpack telemetry (SNOTEL) sites are used to fit models and evaluate their performance. For each location, we train the three models to the neighboring stations within 70 km, transfer the parameters to the location to be modeled, and evaluate modeled time series against the observations at that site. Our model exhibits improved statistics and qualitatively more-realistic behavior at the daily time step when sufficient local training data are available. We reduce density root mean square error (RMSE) by 9.9 and 4.5% compared to previous models while increasing R2 from 0.46 to 0.52 to 0.56 across models. Focusing on the 21-day window around peak SWE in each water year, our model reduces density RMSE by 24 and 17.4% relative to the previous models, with R2 increasing from 0.55 to 0.58 to 0.71 across models. Removing the challenge of parameter transfer over the full observational record increases R2 scores for both the existing and new models, but the gain is greatest for the new model (R2 = 0.75). Our model shows general improvement over

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

    NASA Astrophysics Data System (ADS)

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

    2000-03-01

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

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

    PubMed Central

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

    2009-01-01

    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

  16. Dose assessment for process water tunnels at Hanford Site.

    SciTech Connect

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

    2000-01-01

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

  17. Effect of depth of flooding on the rice water weevil, Lissorhoptrus oryzophilus, and yield of rice.

    PubMed

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

    2013-01-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    Fluxes of the three main greenhouse gases (GHG) CO2, CH4 and N2O from peat and other organic soils 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 dataset 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 of it (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 insights 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

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

    USGS Publications Warehouse

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

    2012-01-01

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

  20. Evaluation of HCMM data for assessing soil moisture and water table depth. [South Dakota

    NASA Technical Reports Server (NTRS)

    Moore, D. G.; Heilman, J. L.; Tunheim, J. A.; Westin, F. C.; Heilman, W. E.; Beutler, G. A.; Ness, S. D. (Principal Investigator)

    1981-01-01

    Soil moisture in the 0-cm to 4-cm layer could be estimated with 1-mm soil temperatures throughout the growing season of a rainfed barley crop in eastern South Dakota. Empirical equations were developed to reduce the effect of canopy cover when radiometrically estimating the soil temperature. Corrective equations were applied to an aircraft simulation of HCMM data for a diversity of crop types and land cover conditions to estimate the soil moisture. The average difference between observed and measured soil moisture was 1.6% of field capacity. Shallow alluvial aquifers were located with HCMM predawn data. After correcting the data for vegetation differences, equations were developed for predicting water table depths within the aquifer. A finite difference code simulating soil moisture and soil temperature shows that soils with different moisture profiles differed in soil temperatures in a well defined functional manner. A significant surface thermal anomaly was found to be associated with shallow water tables.

  1. The influence of water table depth and the free atmospheric state on convective rainfall predisposition

    NASA Astrophysics Data System (ADS)

    Bonetti, Sara; Manoli, Gabriele; Domec, Jean-Christophe; Putti, Mario; Marani, Marco; Katul, Gabriel G.

    2015-04-01

    A mechanistic model for the soil-plant system is coupled to a conventional slab representation of the atmospheric boundary layer (ABL) to explore the role of groundwater table (WT) variations and free atmospheric (FA) states on convective rainfall predisposition (CRP) at a Loblolly pine plantation site situated in the lower coastal plain of North Carolina. Predisposition is quantified using the crossing between modeled lifting condensation level (LCL) and convectively grown ABL depth. The LCL-ABL depth crossing is necessary for air saturation but not sufficient for cloud formation and subsequent convective rainfall occurrence. However, such crossing forms the main template for which all subsequent dynamical processes regulating the formation (or suppression) of convective rainfall operate on. If the feedback between surface fluxes and FA conditions is neglected, a reduction in latent heat flux associated with reduced WT levels is shown to enhance the ABL-LCL crossing probability. When the soil-plant system is fully coupled with ABL dynamics thereby allowing feedback with ABL temperature and humidity, FA states remain the leading control on CRP. However, vegetation water stress plays a role in controlling ABL-LCL crossing when the humidity supply by the FA is within an intermediate range of values. When FA humidity supply is low, cloud formation is suppressed independent of surface latent heat flux. Similarly, when FA moisture supply is high, cloud formation can occur independent of surface latent heat flux. In an intermediate regime of FA moisture supply, the surface latent heat flux controlled by soil water availability can supplement (or suppress) the necessary water vapor leading to reduced LCL and subsequent ABL-LCL crossing. It is shown that this intermediate state corresponds to FA values around the mode in observed humidity lapse rates γw (between -2.5 × 10-6 and -1.5 × 10-6 kg kg-1m-1), suggesting that vegetation water uptake may be controlling CRP at

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

    PubMed

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

    2012-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

  4. Evaluation of the depth-integration method of measuring water discharge in large rivers

    NASA Astrophysics Data System (ADS)

    Moody, John A.; Troutman, Brent M.

    1992-07-01

    The depth-integration method oor measuring water discharge makes a continuos measurement of the water velocity from the water surface to the bottom at 20 to 40 locations or verticals across a river. It is especially practical for large rivers where river traffic makes it impractical to use boats attached to taglines strung across the river or to use current meters suspended from bridges. This method has the additional advantage over the standard two- and eight-tenths method in that a discharge-weighted suspended-sediment sample can be collected at the same time. When this method is used in large rivers such as the Missouri, Mississippi and Ohio, a microwave navigation system is used to determine the ship's position at each vertical sampling location across the river, and to make accurate velocity corrections to compensate for shift drift. An essential feature is a hydraulic winch that can lower and raise the current meter at a constant transit velocity so that the velocities at all depths are measured for equal lengths of time. Field calibration measurements show that: (1) the mean velocity measured on the upcast (bottom to surface) is within 1% of the standard mean velocity determined by 9-11 point measurements; (2) if the transit velocity is less than 25% of the mean velocity, then average error in the mean velocity is 4% or less. The major source of bias error is a result of mounting the current meter above a sounding weight and sometimes above a suspended-sediment sampling bottle, which prevents measurement of the velocity all the way to the bottom. The measured mean velocity is slightly larger than the true mean velocity. This bias error in the discharge is largest in shallow water (approximately 8% for the Missouri River at Hermann, MO, where the mean depth was 4.3 m) and smallest in deeper water (approximately 3% for the Mississippi River at Vickbsurg, MS, where the mean depth was 14.5 m). The major source of random error in the discharge is the natural

  5. Evaluation of the depth-integration method of measuring water discharge in large rivers

    USGS Publications Warehouse

    Moody, J.A.; Troutman, B.M.

    1992-01-01

    The depth-integration method oor measuring water discharge makes a continuos measurement of the water velocity from the water surface to the bottom at 20 to 40 locations or verticals across a river. It is especially practical for large rivers where river traffic makes it impractical to use boats attached to taglines strung across the river or to use current meters suspended from bridges. This method has the additional advantage over the standard two- and eight-tenths method in that a discharge-weighted suspended-sediment sample can be collected at the same time. When this method is used in large rivers such as the Missouri, Mississippi and Ohio, a microwave navigation system is used to determine the ship's position at each vertical sampling location across the river, and to make accurate velocity corrections to compensate for shift drift. An essential feature is a hydraulic winch that can lower and raise the current meter at a constant transit velocity so that the velocities at all depths are measured for equal lengths of time. Field calibration measurements show that: (1) the mean velocity measured on the upcast (bottom to surface) is within 1% of the standard mean velocity determined by 9-11 point measurements; (2) if the transit velocity is less than 25% of the mean velocity, then average error in the mean velocity is 4% or less. The major source of bias error is a result of mounting the current meter above a sounding weight and sometimes above a suspended-sediment sampling bottle, which prevents measurement of the velocity all the way to the bottom. The measured mean velocity is slightly larger than the true mean velocity. This bias error in the discharge is largest in shallow water (approximately 8% for the Missouri River at Hermann, MO, where the mean depth was 4.3 m) and smallest in deeper water (approximately 3% for the Mississippi River at Vickbsurg, MS, where the mean depth was 14.5 m). The major source of random error in the discharge is the natural

  6. Dose specification for 192Ir high dose rate brachytherapy in terms of dose-to-water-in-medium and dose-to-medium-in-medium

    NASA Astrophysics Data System (ADS)

    Paiva Fonseca, Gabriel; Carlsson Tedgren, Åsa; Reniers, Brigitte; Nilsson, Josef; Persson, Maria; Yoriyaz, Hélio; Verhaegen, Frank

    2015-06-01

    Dose calculation in high dose rate brachytherapy with 192Ir is usually based on the TG-43U1 protocol where all media are considered to be water. Several dose calculation algorithms have been developed that are capable of handling heterogeneities with two possibilities to report dose: dose-to-medium-in-medium (Dm,m) and dose-to-water-in-medium (Dw,m). The relation between Dm,m and Dw,m for 192Ir is the main goal of this study, in particular the dependence of Dw,m on the dose calculation approach using either large cavity theory (LCT) or small cavity theory (SCT). A head and neck case was selected due to the presence of media with a large range of atomic numbers relevant to tissues and mass densities such as air, soft tissues and bone interfaces. This case was simulated using a Monte Carlo (MC) code to score: Dm,m, Dw,m (LCT), mean photon energy and photon fluence. Dw,m (SCT) was derived from MC simulations using the ratio between the unrestricted collisional stopping power of the actual medium and water. Differences between Dm,m and Dw,m (SCT or LCT) can be negligible (<1%) for some tissues e.g. muscle and significant for other tissues with differences of up to 14% for bone. Using SCT or LCT approaches leads to differences between Dw,m (SCT) and Dw,m (LCT) up to 29% for bone and 36% for teeth. The mean photon energy distribution ranges from 222 keV up to 356 keV. However, results obtained using mean photon energies are not equivalent to the ones obtained using the full, local photon spectrum. This work concludes that it is essential that brachytherapy studies clearly report the dose quantity. It further shows that while differences between Dm,m and Dw,m (SCT) mainly depend on tissue type, differences between Dm,m and Dw,m (LCT) are, in addition, significantly dependent on the local photon energy fluence spectrum which varies with distance to implanted sources.

  7. The impact of water temperature on the measurement of absolute dose

    NASA Astrophysics Data System (ADS)

    Islam, Naveed Mehdi

    To standardize reference dosimetry in radiation therapy, Task Group 51 (TG 51) of American Association of Physicist's in Medicine (AAPM) recommends that dose calibration measurements be made in a water tank at a depth of 10 cm and at a reference geometry. Methodologies are provided for calculating various correction factors to be applied in calculating the absolute dose. However the protocol does not specify the water temperature to be used. In practice, the temperature of water during dosimetry may vary considerably between independent sessions and different centers. In this work the effect of water temperature on absolute dosimetry has been investigated. Density of water varies with temperature, which in turn may impact the beam attenuation and scatter properties. Furthermore, due to thermal expansion or contraction air volume inside the chamber may change. All of these effects can result in a change in the measurement. Dosimetric measurements were made using a Farmer type ion chamber on a Varian Linear Accelerator for 6 MV and 23 MV photon energies for temperatures ranging from 10 to 40 °C. A thermal insulation was designed for the water tank in order to maintain relatively stable temperature over the duration of the experiment. Dose measured at higher temperatures were found to be consistently higher by a very small magnitude. Although the differences in dose were less than the uncertainty in each measurement, a linear regression of the data suggests that the trend is statistically significant with p-values of 0.002 and 0.013 for 6 and 23 MV beams respectively. For a 10 degree difference in water phantom temperatures, which is a realistic deviation across clinics, the final calculated reference dose can differ by 0.24% or more. To address this effect, first a reference temperature (e.g.22 °C) can be set as the standard; subsequently a correction factor can be implemented for deviations from this reference. Such a correction factor is expected to be of similar

  8. Lipid composition and molecular interactions change with depth in the avian stratum corneum to regulate cutaneous water loss.

    PubMed

    Champagne, Alex M; Allen, Heather C; Williams, Joseph B

    2015-10-01

    The outermost 10-20 µm of the epidermis, the stratum corneum (SC), consists of flat, dead cells embedded in a matrix of intercellular lipids. These lipids regulate cutaneous water loss (CWL), which accounts for over half of total water loss in birds. However, the mechanisms by which lipids are able to regulate CWL and how these mechanisms change with depth in the SC are poorly understood. We used attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) to measure lipid-lipid and lipid-water interactions as a function of depth in the SC of house sparrows (Passer domesticus Linnaeus) in the winter and summer. We then compared these molecular interactions at each depth with lipid composition at the same depth. We found that in both groups, water content increased with depth in the SC, and likely contributed to greater numbers of gauche defects in lipids in deeper levels of the SC. In winter-caught birds, which had lower rates of CWL than summer-caught birds, water exhibited stronger hydrogen bonding in deeper layers of the SC, and these strong hydrogen bonds were associated with greater amounts of polar lipids such as ceramides and cerebrosides. Based on these data, we propose a model by which polar lipids in deep levels of the SC form strong hydrogen bonds with water molecules to increase the viscosity of water and slow the permeation of water through the SC. PMID:26447196

  9. Fish communities associated with cold-water corals vary with depth and substratum type

    NASA Astrophysics Data System (ADS)

    Milligan, Rosanna J.; Spence, Gemma; Roberts, J. Murray; Bailey, David M.

    2016-08-01

    Understanding the processes that drive the distribution patterns of organisms and the scales over which these processes operate are vital when considering the effective management of species with high commercial or conservation value. In the deep sea, the importance of scleractinian cold-water corals (CWCs) to fish has been the focus of several studies but their role remains unclear. We propose this may be due to the confounding effects of multiple drivers operating over multiple spatial scales. The aims of this study were to investigate the role of CWCs in shaping fish community structure and individual species-habitat associations across four spatial scales in the NE Atlantic ranging from "regions" (separated by >500 km) to "substratum types" (contiguous). Demersal fish and substratum types were quantified from three regions: Logachev Mounds, Rockall Bank and Hebrides Terrace Seamount (HTS). PERMANOVA analyses showed significant differences in community composition between all regions which were most likely caused by differences in depths. Within regions, significant variation in community composition was recorded at scales of c. 20-3500 m. CWCs supported significantly different fish communities to non-CWC substrata at Rockall Bank, Logachev and the HTS. Single-species analyses using generalised linear mixed models showed that Sebastes sp. was strongly associated with CWCs at Rockall Bank and that Neocyttus helgae was more likely to occur in CWCs at the HTS. Depth had a significant effect on several other fish species. The results of this study suggest that the importance of CWCs to fish is species-specific and depends on the broader spatial context in which the substratum is found. The precautionary approach would be to assume that CWCs are important for associated fish, but must acknowledge that CWCs in different depths will not provide redundancy or replication within spatially-managed conservation networks.

  10. Relations between erythemal UV dose, global solar radiation, total ozone column and aerosol optical depth at Uccle, Belgium

    NASA Astrophysics Data System (ADS)

    De Bock, V.; De Backer, H.; Van Malderen, R.; Mangold, A.; Delcloo, A.

    2014-11-01

    At Uccle, Belgium, a long time series (1991-2013) of simultaneous measurements of erythemal ultraviolet (UV) dose (Sery), global solar radiation (Sg), total ozone column (QO3) and aerosol optical depth (τaer) (at 320.1 nm) is available, which allows for an extensive study of the changes in the variables over time. Linear trends were determined for the different monthly anomalies time series. Sery, Sg and QO3 all increase by respectively 7, 4 and 3% per decade. τaer shows an insignificant negative trend of -8% per decade. These trends agree with results found in the literature for sites with comparable latitudes. A change-point analysis, which determines whether there is a significant change in the mean of the time series, is applied to the monthly anomalies time series of the variables. Only for Sery and QO3, was a significant change point present in the time series around February 1998 and March 1998, respectively. The change point in QO3 corresponds with results found in the literature, where the change in ozone levels around 1997 is attributed to the recovery of ozone. A multiple linear regression (MLR) analysis is applied to the data in order to study the influence of Sg, QO3 and τaer on Sery. Together these parameters are able to explain 94% of the variation in Sery. Most of the variation (56%) in Sery is explained by Sg. The regression model performs well, with a slight tendency to underestimate the measured Sery values and with a mean absolute bias error (MABE) of 18%. However, in winter, negative Sery are modeled. Applying the MLR to the individual seasons solves this issue. The seasonal models have an adjusted R2 value higher than 0.8 and the correlation between modeled and measured Sery values is higher than 0.9 for each season. The summer model gives the best performance, with an absolute mean error of only 6%. However, the seasonal regression models do not always represent reality, where an increase in Sery is accompanied with an increase in QO3 and

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

    USGS Publications Warehouse

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

    2012-01-01

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

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

    SciTech Connect

    Bolton, J.C. )

    1990-08-01

    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.

  13. Cathodic protection upgrade of the 1,050 ft water depth Cognac platform

    SciTech Connect

    Goolsby, A.D.; McGuire, D.P.

    1997-09-01

    This paper reports the steps of a cathodic protection upgrade of a three year old deep water platform (the Cognac structure, Mississippi Canyon 194A) installed in 1977/78. These steps include obtaining results from an ROV survey, using the survey data to calculate added currents needed to upgrade cathodic protection of the platform, achieving retrofit anode installation using then novel methods, and following-up with CP surveys showing the success of the upgrade. The authors calculated that 3,100 amperes of additional current applied at depths from 250 to 1,050 feet would be needed to achieve full cathodic protection of the well conductors and jacket of Cognac. Approximately 1,100 additional aluminum anodes were installed during the early 1980`s, using two novel installation methods. Installed cost was estimated at $5.4MM. Potentials since the time of the upgrade have been very satisfactory.

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

    SciTech Connect

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

    2005-09-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

    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

  16. Primary and secondary particle contributions to the depth dose distribution in a phantom shielded from solar flare and Van Allen protons

    NASA Technical Reports Server (NTRS)

    Santoro, R. T.; Claiborne, H. C.; Alsmiller, R. G., Jr.

    1972-01-01

    Calculations have been made using the nucleon-meson transport code NMTC to estimate the absorbed dose and dose equivalent distributions in astronauts inside space vehicles bombarded by solar flare and Van Allen protons. A spherical shell shield of specific radius and thickness with a 30-cm-diam. tissue ball at the geometric center was used to simulate the spacecraft-astronaut configuration. The absorbed dose and the dose equivalent from primary protons, secondary protons, heavy nuclei, charged pions, muons, photons, and positrons and electrons are given as a function of depth in the tissue phantom. Results are given for solar flare protons with a characteristic rigidity of 100 MV and for Van Allen protons in a 240-nautical-mile circular orbit at 30 degree inclination angle incident on both 20-g/sq cm-thick aluminum and polyethylene spherical shell shields.

  17. An absorbed dose to water calorimeter for collimated radiation fields

    NASA Astrophysics Data System (ADS)

    Brede, H. J.; Hecker, O.; Hollnagel, R.

    2000-12-01

    A transportable calorimeter of compact design has been developed as a device for the absolute determination of the absorbed dose to water. The ease of operation of the calorimeter allows the application in clinical therapy beams of various energies, specifically for neutron, proton and heavy ion beams. The calorimeter requires collimated radiation fields with diameters lesser than 40 mm. The temperature rise caused by radiation is measured with a thermistor probe which is located in the centre of the calorimeter core. The calorimeter core consists of a cylindrical water-filled gilded aluminium can suspended by three thin nylon threads in a vacuum block in order to reduce the heat transfer by conduction. In addition, it operates at a temperature of 4°C, preventing heat transfer in water by convection. Heat transfer from the core to the surrounding by radiation is minimised by the use of two concentric temperature-controlled jackets, the inner jacket being operated at core temperature. A description of the mechanical and electrical design, of the construction and operation of the water calorimeter is given. In addition, calculations with a finite-element program code performed to determine correction factors for various radiation conditions are included.

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

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

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

  19. 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)

    Bowin, C.

    1982-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Whitlock, C. H.

    1976-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

  2. Evaluation of CALIOP 532-nm Aerosol Optical Depth Over Opaque Water Clouds

    NASA Technical Reports Server (NTRS)

    Liu, Z.; Winker, D.; Omar, A.; Vaughan, M.; Kar, J.; Trepte, C.; Hu, Y.; Schuster, G.

    2015-01-01

    With its height-resolved measurements and near global coverage, the CALIOP lidar onboard the CALIPSO satellite offers a new capability for aerosol retrievals in cloudy skies. Validation of these retrievals is difficult, however, as independent, collocated and co-temporal data sets are generally not available. In this paper, we evaluate CALIOP aerosol products above opaque water clouds by applying multiple retrieval techniques to CALIOP Level 1 profile data and comparing the results. This approach allows us to both characterize the accuracy of the CALIOP above-cloud aerosol optical depth (AOD) and develop an error budget that quantifies the relative contributions of different error sources. We focus on two spatial domains: the African dust transport pathway over the tropical North Atlantic and the African smoke transport pathway over the southeastern Atlantic. Six years of CALIOP observations (2007-2012) from the northern hemisphere summer and early fall are analyzed. The analysis is limited to cases where aerosol layers are located above opaque water clouds so that a constrained retrieval technique can be used to directly retrieve 532 nm aerosol optical depth and lidar ratio. For the moderately dense Sahara dust layers detected in the CALIOP data used in this study, the mean/median values of the lidar ratios derived from a constrained opaque water cloud (OWC) technique are 45.1/44.4 +/- 8.8 sr, which are somewhat larger than the value of 40 +/- 20 sr used in the CALIOP Level 2 (L2) data products. Comparisons of CALIOP L2 AOD with the OWC-retrieved AOD reveal that for nighttime conditions the L2 AOD in the dust region is underestimated on average by approx. 26% (0.183 vs. 0.247). Examination of the error sources indicates that errors in the L2 dust AOD are primarily due to using a lidar ratio that is somewhat too small. The mean/median lidar ratio retrieved for smoke is 70.8/70.4 +/- 16.2 sr, which is consistent with the modeled value of 70 +/- 28 sr used in the

  3. Waveguide invariant active sonar target detection and depth classification in shallow water

    NASA Astrophysics Data System (ADS)

    Goldhahn, Ryan A.

    Reverberation and clutter are two of the principle obstacles to active sonar target detection in shallow water. Diffuse seabed backscatter can obscure low energy target returns, while clutter discretes, specific features of the sea floor, produce temporally compact returns which may be mistaken for targets of interest. Detecting weak targets in the presence of reverberation and discriminating water column targets from bottom clutter are thus critical to good performance in active sonar. Both problems are addressed in this thesis using the time-frequency interference pattern described by a constant known as the waveguide invariant which summarizes in a scalar parameter the dispersive properties of the ocean environment. Conventional active sonar detection involves constant false alarm rate (CFAR) normalization of the reverberation return which does not account for the frequency-selective fading in a wideband pulse caused by multipath propagation. An alternative to conventional reverberation estimation is presented, motivated by striations observed in time-frequency analysis of active sonar data. A mathematical model for these reverberation striations is derived using waveguide invariant theory. This model is then used to motivate waveguide invariant reverberation estimation which involves averaging the time-frequency spectrum along these striations. An evaluation of this reverberation estimate using real Mediterranean data is given and its use in a generalized likelihood ratio test (GLRT) based CFAR detector is demonstrated. CFAR detection using waveguide invariant reverberation estimates is shown to out-perform conventional cell-averaged and frequency-invariant CFAR detection methods in shallow water environments producing strong reverberation returns which exhibit the described striations. Results are presented on simulated and real Mediterranean data from the SCARAB98 experiment. The ability to discriminate between water column targets and clutter discretes is

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

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    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

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

    NASA Astrophysics Data System (ADS)

    Velpuri, N.; Senay, G. B.

    2011-12-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Carlsson Tedgren, Åsa; Alm Carlsson, Gudrun

    2013-04-01

    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.

  9. 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)

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

    2014-12-01

    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.

  10. Depth dependence of absorbed dose, dose equivalent and linear energy transfer spectra of galactic and trapped particles in polyethylene and comparison with calculations of models

    NASA Technical Reports Server (NTRS)

    Badhwar, G. D.; Cucinotta, F. A.; Wilson, J. W. (Principal Investigator)

    1998-01-01

    A matched set of five tissue-equivalent proportional counters (TEPCs), embedded at the centers of 0 (bare), 3, 5, 8 and 12-inch-diameter polyethylene spheres, were flown on the Shuttle flight STS-81 (inclination 51.65 degrees, altitude approximately 400 km). The data obtained were separated into contributions from trapped protons and galactic cosmic radiation (GCR). From the measured linear energy transfer (LET) spectra, the absorbed dose and dose-equivalent rates were calculated. The results were compared to calculations made with the radiation transport model HZETRN/NUCFRG2, using the GCR free-space spectra, orbit-averaged geomagnetic transmission function and Shuttle shielding distributions. The comparison shows that the model fits the dose rates to a root mean square (rms) error of 5%, and dose-equivalent rates to an rms error of 10%. Fairly good agreement between the LET spectra was found; however, differences are seen at both low and high LET. These differences can be understood as due to the combined effects of chord-length variation and detector response function. These results rule out a number of radiation transport/nuclear fragmentation models. Similar comparisons of trapped-proton dose rates were made between calculations made with the proton transport model BRYNTRN using the AP-8 MIN trapped-proton model and Shuttle shielding distributions. The predictions of absorbed dose and dose-equivalent rates are fairly good. However, the prediction of the LET spectra below approximately 30 keV/microm shows the need to improve the AP-8 model. These results have strong implications for shielding requirements for an interplanetary manned mission.

  11. Evaluating the value of ENVISAT ASAR Data for the mapping and monitoring of peatland water table depths

    NASA Astrophysics Data System (ADS)

    Bechtold, Michel; Schlaffer, Stefan

    2015-04-01

    The Advanced Synthetic Aperture Radar (ASAR) onboard ENVISAT collected C-Band microwave backscatter data from 2005 to 2012. Backscatter in the C-Band depends to a large degree on the roughness and the moisture status of vegetation and soil surface with a penetration depth of ca. 3 cm. In wetlands with stable high water levels, the annual soil surface moisture dynamics are very distinct compared to the surrounding areas, which allows the monitoring of such environments with ASAR data (Reschke et al. 2012). Also in drained peatlands, moisture status of vegetation and soil surface strongly depends on water table depth due to high hydraulic conductivities of many peat soils in the low suction range (Dettmann et al. 2014). We hypothesize that this allows the characterization of water table depths with ASAR data. Here we analyze whether ASAR data can be used for the spatial and temporal estimation of water table depths in different peatlands (natural, near-natural, agriculturally-used and rewetted). Mapping and monitoring of water table depths is of crucial importance, e.g. for upscaling greenhouse gas emissions and evaluating the success of peatland rewetting projects. Here, ASAR data is analyzed with a new map of water table depths for the organic soils in Germany (Bechtold et al. 2014) as well as with a comprehensive data set of monitored peatland water levels from 1100 dip wells and 54 peatlands. ASAR time series from the years 2005-2012 with irregular temporal sampling intervals of 3-14 days were processed. Areas covered by snow were masked. Primary results about the accuracy of spatial estimates show significant correlations between long-term backscatter statistics and spatially-averaged water table depths extracted from the map at the resolution of the ASAR data. Backscatter also correlates with long-term averages of point-scale water table depth data of the monitoring wells. For the latter, correlation is highest between the dry reference backscatter values and

  12. Direct MC conversion of absorbed dose to graphite to absorbed dose to water for 60Co radiation.

    PubMed

    Lye, J E; Butler, D J; Franich, R D; Harty, P D; Oliver, C P; Ramanathan, G; Webb, D V; Wright, T

    2013-06-01

    The ARPANSA calibration service for (60)Co gamma rays is based on a primary standard graphite calorimeter that measures absorbed dose to graphite. Measurements with the calorimeter are converted to the absorbed dose to water using the calculation of the ratio of the absorbed dose in the calorimeter to the absorbed dose in a water phantom. ARPANSA has recently changed the basis of this calculation from a photon fluence scaling method to a direct Monte Carlo (MC) calculation. The MC conversion uses an EGSnrc model of the cobalt source that has been validated against water tank and graphite phantom measurements, a step that is required to quantify uncertainties in the underlying interaction coefficients in the MC code. A comparison with the Bureau International des Poids et Mesures (BIPM) as part of the key comparison BIPM.RI(I)-K4 showed an agreement of 0.9973 (53). PMID:23152147

  13. Mars Orbiter Laser Altimeter Radiometry: Phase Functions and the Optical Depth of Nocturnal Water Ice Clouds

    NASA Astrophysics Data System (ADS)

    Neumann, G. A.; Barker, M. K.; Sun, X.

    2014-12-01

    Over the course of more than 3 Mars years the MOLA instrument on board Mars Global Surveyor (from 1999 to the loss of MGS in Nov. 2006) obtained passive reflectance measurements of Mars at 1064 nm wavelength from the solar background. As an altimeter, the quantity of light removed from a laser beam by scattering or absorption during the roundtrip to the surface may be calculated knowing the energy returned, the surface geometric albedo and the instrument parameters for each laser shot. These opacity measurements indicate the combined effects of dust and condensates, particularly those seen during during the night. The measure of opacity, to optical depths exceeding unity, correlates well with daytime measurements by the Hubble Space Telescope and with the broadband Thermal Emission Spectrometer. Applying a simple phase function to passive radiometric observations obtained at emission angles varying from 0 to 80 degrees, upper and lower limits are obtained for atmospheric opacity as a function of season and time of day. The implications for the effects of nocturnal water ice clouds on radiative transfer, and for future applications to the detection of icy plumes from moons of the outer solar system will be discussed.

  14. Evaluation of HCMM data for assessing soil moisture and water table depth

    NASA Technical Reports Server (NTRS)

    Moore, D. G.; Heilman, J. L.; Tunheim, J. A.; Westin, F. C.; Heilman, W. E.; Beutler, G. A.; Ness, S. D. (Principal Investigator)

    1981-01-01

    Data were analyzed for variations in eastern South Dakota. Soil moisture in the 0-4 cm layer could be estimated with 1-mm soil temperatures throughout the growing season of a rainfed barley crop (% cover ranging from 30% to 90%) with an r squared = 0.81. Empirical equations were developed to reduce the effect of canopy cover when radiometrically estimating the 1-mm soil temperature, r squared = 0.88. The corrective equations were applied to an aircraft simulation of HCMM data for a diversity of crop types and land cover conditions to estimate the 0-4 cm soil moisture. The average difference between observed and measured soil moisture was 1.6% of field capacity. HCMM data were used to estimate the soil moisture for four dates with an r squared = 0.55 after correction for crop conditions. Location of shallow alluvial aquifers could be accomplished with HCMM predawn data. After correction of HCMM day data for vegetation differences, equations were developed for predicting water table depths within the aquifer (r=0.8).

  15. Analysis of small field percent depth dose and profiles: Comparison of measurements with various detectors and effects of detector orientation with different jaw settings

    PubMed Central

    Godson, Henry Finlay; Ravikumar, M.; Sathiyan, S.; Ganesh, K. M.; Ponmalar, Y. Retna; Varatharaj, C.

    2016-01-01

    The advent of modern technologies in radiotherapy poses an increased challenge in the determination of dosimetric parameters of small fields that exhibit a high degree of uncertainty. Percent depth dose and beam profiles were acquired using different detectors in two different orientations. The parameters such as relative surface dose (DS), depth of dose maximum (Dmax), percentage dose at 10 cm (D10), penumbral width, flatness, and symmetry were evaluated with different detectors. The dosimetric data were acquired for fields defined by jaws alone, multileaf collimator (MLC) alone, and by MLC while the jaws were positioned at 0, 0.25, 0.5, and 1.0 cm away from MLC leaf-end using a Varian linear accelerator with 6 MV photon beam. The accuracy in the measurement of dosimetric parameters with various detectors for three different field definitions was evaluated. The relative DS(38.1%) with photon field diode in parallel orientation was higher than electron field diode (EFD) (27.9%) values for 1 cm ×1 cm field. An overestimation of 5.7% and 8.6% in D10 depth were observed for 1 cm ×1 cm field with RK ion chamber in parallel and perpendicular orientation, respectively, for the fields defined by MLC while jaw positioned at the edge of the field when compared to EFD values in parallel orientation. For this field definition, the in-plane penumbral widths obtained with ion chamber in parallel and perpendicular orientation were 3.9 mm, 5.6 mm for 1 cm ×1 cm field, respectively. Among all detectors used in the study, the unshielded diodes were found to be an appropriate choice of detector for the measurement of beam parameters in small fields. PMID:27051165

  16. Analysis of small field percent depth dose and profiles: Comparison of measurements with various detectors and effects of detector orientation with different jaw settings.

    PubMed

    Godson, Henry Finlay; Ravikumar, M; Sathiyan, S; Ganesh, K M; Ponmalar, Y Retna; Varatharaj, C

    2016-01-01

    The advent of modern technologies in radiotherapy poses an increased challenge in the determination of dosimetric parameters of small fields that exhibit a high degree of uncertainty. Percent depth dose and beam profiles were acquired using different detectors in two different orientations. The parameters such as relative surface dose (D S), depth of dose maximum (D max), percentage dose at 10 cm (D 10), penumbral width, flatness, and symmetry were evaluated with different detectors. The dosimetric data were acquired for fields defined by jaws alone, multileaf collimator (MLC) alone, and by MLC while the jaws were positioned at 0, 0.25, 0.5, and 1.0 cm away from MLC leaf-end using a Varian linear accelerator with 6 MV photon beam. The accuracy in the measurement of dosimetric parameters with various detectors for three different field definitions was evaluated. The relative D S(38.1%) with photon field diode in parallel orientation was higher than electron field diode (EFD) (27.9%) values for 1 cm ×1 cm field. An overestimation of 5.7% and 8.6% in D 10 depth were observed for 1 cm ×1 cm field with RK ion chamber in parallel and perpendicular orientation, respectively, for the fields defined by MLC while jaw positioned at the edge of the field when compared to EFD values in parallel orientation. For this field definition, the in-plane penumbral widths obtained with ion chamber in parallel and perpendicular orientation were 3.9 mm, 5.6 mm for 1 cm ×1 cm field, respectively. Among all detectors used in the study, the unshielded diodes were found to be an appropriate choice of detector for the measurement of beam parameters in small fields. PMID:27051165

  17. A Geant4 simulation of the depth dose percentage in brain tumors treatments using protons and carbon ions

    NASA Astrophysics Data System (ADS)

    José A. Diaz, M.; Torres, D. A.

    2016-07-01

    The deposited energy and dose distribution of beams of protons and carbon over a head are simulated using the free tool package Geant4 and the data analysis package ROOT-C++. The present work shows a methodology to understand the microscopical process occurring in a session of hadron-therapy using advance simulation tools.

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

    PubMed Central

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

    2014-01-01

    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

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

    PubMed

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

    2014-01-01

    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

  20. Effects of water depth and spectral bandwidth on Stokes drift estimation based on short-term variation of wave conditions

    NASA Astrophysics Data System (ADS)

    Myrhaug, Dag; Wang, Hong; Holmedal, Lars Erik

    2016-04-01

    The Stokes drift represents an important transport component of ocean circulation models. Locally it is responsible for transport of e.g. contaminated ballast water from ships, oil spills, plankton and larvae. It also plays an important role in mixing processes across the interphase between the atmosphere and the ocean. The Stokes drift is the mean Lagrangian velocity obtained from the water particle trajectory in the wave propagation direction; it is maximum at the surface, decreasing rapidly with the depth below the surface. The total mean mass transport is obtained by integrating the Stokes drift over the water depth; this is also referred to as the volume Stokes transport. The paper provides a simple analytical method which can be used to give estimates of the Stokes drift in moderate intermediate water depth based on short-term variation of wave conditions. This is achieved by using a joint distribution of individual wave heights and wave periods together with an explicit solution of the wave dispersion equation. The mean values of the surface Stokes drift and the volume Stokes transport for individual random waves within a sea state are presented, and the effects of water depth and spectral bandwidth parameter are discussed. Furthermore, example of results corresponding to typical field conditions are presented to demonstrate the application of the method, including the Stokes drift profile in the water column beneath the surface. Thus, the present analytical method can be used to estimate the Stokes drift in moderate intermediate water depth for random waves within a sea state based on available wave statistics.

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    Floodplain environments can exhibit strong gradients in soil moisture availability, from very dry to saturated, with important consequences for riparian vegetation transpiration and productivity and therefore ecohydrologic flowpaths. These gradients are often driven by geomorphic features that themselves can be affected by vegetation change over relatively short timescales. The Rio Grande has undergone substantial change in the past half century, including channel narrowing and significant expansion of non-native vegetation, often across previously unvegetated sandbars and natural levees. The objective of this study was to assess water sources for Arundo donax L. (giant reed), a now common invasive grass growing along the floodplains of the Rio Grande. Our hypotheses were: a) Arundo would switch from primarily shallow soil moisture to groundwater during periods of soil moisture deficit, but that this access would be limited by increasing groundwater depths, and b) transpiration would decline with floodplain elevation and decreasing surface soil moisture because of increasing depth to groundwater and surface soil moisture deficits. We used natural-abundance stable isotopes of oxygen (δ18O) and hydrogen (δ2H) to determine the water sources of Arundo along four approximately 100-meter transects arrayed perpendicular to the Rio Grande in southwest Texas. Surface soil water, river water, groundwater, precipitation and rhizome sections were collected every month from summer 2010 until summer 2011 to assess potential source water isotopic composition for Arundo. Mixing models were used to estimate Arundo dependence on surface soil moisture or groundwater. The isotopic compositions of groundwater and river water were similar throughout the year, indicating significant hyporheic exchange. As expected, the isotopic composition of precipitation events and a large flood event were distinct from the slowly-changing river and allowed an assessment of Arundo use of these

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

    ERIC Educational Resources Information Center

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

    2013-01-01

    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.)

  5. Effects of harvest regime and water depth on nutrient recovery from swine wastewater by growing Spirodela oligorrhiza.

    PubMed

    Xu, Jiele; Shen, Genxiang

    2011-11-01

    Harvest regime and water depth were investigated to determine their effects on nutrient recovery from swine wastewater by a Spirodela oligorrhiza system. The results show that harvesting less duckweed at shorter intervals favored nutrient removal and total biomass production. Harvesting 20% of duckweed twice a week led to 66.3 and 109.4% higher total nitrogen and total phosphorus removals, respectively, and a duckweed production of 20.0 g fresh biomass/m2 x d--39.6% higher than that of harvesting 80% of duckweed once every 4 weeks. The water depth of duckweed system was of great importance to total nutrient removal. At the water depth of 40 cm, total nitrogen and total phosphorus removals were 2.05 and 2.16 times higher, respectively, than those at the water depth of 10 cm. However, because of the larger amount of nutrients in a deeper system, it took a longer time for the nutrient concentrations to decrease. PMID:22195427

  6. Water Relations and Foliar Isotopic Composition of Prosopis tamarugo Phil., an Endemic Tree of the Atacama Desert Growing at Three Levels of Water Table Depth.

    PubMed

    Garrido, Marco; Silva, Paola; Acevedo, Edmundo

    2016-01-01

    Prosopis tamarugo Phil. is a strict phreatophyte tree species endemic to the "Pampa del Tamarugal", Atacama Desert. The extraction of water for various uses has increased the depth of the water table in the Pampa aquifers threatening its conservation. This study aimed to determine the effect of the groundwater table depth on the water relations of P. tamarugo and to present thresholds of groundwater depth (GWD) that can be used in the groundwater management of the P. tamarugo ecosystem. Three levels of GWD, 11.2 ± 0.3 m, 10.3 ± 0.3 m, and 7.1 ± 0.1 m, (the last GWD being our reference) were selected and groups of four individuals per GWD were studied in the months of January and July of the years 2011 through 2014. When the water table depth exceeded 10 m, P. tamarugo had lower pre-dawn and mid-day water potential but no differences were observed in minimum leaf stomatal resistance when compared to the condition of 7.1 m GWD; the leaf tissue increased its δ(13)C and δ(18)O composition. Furthermore, a smaller green canopy fraction of the trees and increased foliage loss in winter with increasing water table depth was observed. The differences observed in the physiological behavior of P. tamarugo trees, attributable to the ground water depth; show that increasing the depth of the water table from 7 to 11 m significantly affects the water status of P. tamarugo. The results indicate that P. tamarugo has an anisohydric stomatal behavior and that given a reduction in water supply it regulates the water demand via foliage loss. The growth and leaf physiological activities are highly sensitive to GWD. The foliage loss appears to prevent the trees from reaching water potentials leading to complete loss of hydraulic functionality by cavitation. The balance achieved between water supply and demand was reflected in the low variation of the water potential and of the variables related to gas exchange over time for a given GWD. This acclimation capacity of P. tamarugo after

  7. Water Relations and Foliar Isotopic Composition of Prosopis tamarugo Phil., an Endemic Tree of the Atacama Desert Growing at Three Levels of Water Table Depth

    PubMed Central

    Garrido, Marco; Silva, Paola; Acevedo, Edmundo

    2016-01-01

    Prosopis tamarugo Phil. is a strict phreatophyte tree species endemic to the “Pampa del Tamarugal”, Atacama Desert. The extraction of water for various uses has increased the depth of the water table in the Pampa aquifers threatening its conservation. This study aimed to determine the effect of the groundwater table depth on the water relations of P. tamarugo and to present thresholds of groundwater depth (GWD) that can be used in the groundwater management of the P. tamarugo ecosystem. Three levels of GWD, 11.2 ± 0.3 m, 10.3 ± 0.3 m, and 7.1 ± 0.1 m, (the last GWD being our reference) were selected and groups of four individuals per GWD were studied in the months of January and July of the years 2011 through 2014. When the water table depth exceeded 10 m, P. tamarugo had lower pre-dawn and mid-day water potential but no differences were observed in minimum leaf stomatal resistance when compared to the condition of 7.1 m GWD; the leaf tissue increased its δ13C and δ18O composition. Furthermore, a smaller green canopy fraction of the trees and increased foliage loss in winter with increasing water table depth was observed. The differences observed in the physiological behavior of P. tamarugo trees, attributable to the ground water depth; show that increasing the depth of the water table from 7 to 11 m significantly affects the water status of P. tamarugo. The results indicate that P. tamarugo has an anisohydric stomatal behavior and that given a reduction in water supply it regulates the water demand via foliage loss. The growth and leaf physiological activities are highly sensitive to GWD. The foliage loss appears to prevent the trees from reaching water potentials leading to complete loss of hydraulic functionality by cavitation. The balance achieved between water supply and demand was reflected in the low variation of the water potential and of the variables related to gas exchange over time for a given GWD. This acclimation capacity of P. tamarugo after

  8. Root plasticity of Populus euphratica seedlings in response to different water table depths and contrasting sediment types.

    PubMed

    Wang, Lijuan; Zhao, Chengyi; Li, Jun; Liu, Zhihui; Wang, Jianghong

    2015-01-01

    Riparian plants in arid regions face a highly variable water environment controlled by hydrological processes. To understand whether riparian plants adapt to such environments through plastic responses, we compared the root traits, biomass allocation and growth of Populus euphratica Oliv. Seedlings grown in lysimeters filled with clay or clay/river sand sediments under inundation and varying water table conditions. We hypothesized that adaptive phenotypic plasticity is likely to develop or be advantageous in seedlings of this species to allow them to adapt desert floodplain environments. Growth was significantly reduced by inundation. However, rather than following relatively fixed trait and allocation patterns, the seedlings displayed adaptive mechanisms involving the development of adventitious roots to enhance plant stability and obtain oxygen, together with a lower proportion of root biomass. At the whole-plant level, at deeper water table depths, seedlings allocated more biomass to the roots, and total root length increased with decreasing water table depths, regardless of the sediment, consistent with optimal partitioning theory. The sediment type had a significant effect on seedling root traits. P. euphratica displayed very different root traits in different sediment types under the same hydrological conditions, showing a greater first-order root number in clay sediment under shallower water table conditions, whereas rooting depth was greater in clay/river sand sediment under deep water table conditions. In clay sediment, seedlings responded to lower water availability via greater root elongation, while the root surface area was increased through increasing the total root length in clay/river sand sediment, suggesting that seedlings facing deeper water tables are not always likely to increase their root surface area to obtain more water. Our results indicate that P. euphratica seedlings are able to adapt to a range of water table conditions through plastic

  9. Root Plasticity of Populus euphratica Seedlings in Response to Different Water Table Depths and Contrasting Sediment Types

    PubMed Central

    Wang, Lijuan; Zhao, Chengyi; Li, Jun; Liu, Zhihui; Wang, Jianghong

    2015-01-01

    Riparian plants in arid regions face a highly variable water environment controlled by hydrological processes. To understand whether riparian plants adapt to such environments through plastic responses, we compared the root traits, biomass allocation and growth of Populus euphratica Oliv. Seedlings grown in lysimeters filled with clay or clay/river sand sediments under inundation and varying water table conditions. We hypothesized that adaptive phenotypic plasticity is likely to develop or be advantageous in seedlings of this species to allow them to adapt desert floodplain environments. Growth was significantly reduced by inundation. However, rather than following relatively fixed trait and allocation patterns, the seedlings displayed adaptive mechanisms involving the development of adventitious roots to enhance plant stability and obtain oxygen, together with a lower proportion of root biomass. At the whole-plant level, at deeper water table depths, seedlings allocated more biomass to the roots, and total root length increased with decreasing water table depths, regardless of the sediment, consistent with optimal partitioning theory. The sediment type had a significant effect on seedling root traits. P. euphratica displayed very different root traits in different sediment types under the same hydrological conditions, showing a greater first-order root number in clay sediment under shallower water table conditions, whereas rooting depth was greater in clay/river sand sediment under deep water table conditions. In clay sediment, seedlings responded to lower water availability via greater root elongation, while the root surface area was increased through increasing the total root length in clay/river sand sediment, suggesting that seedlings facing deeper water tables are not always likely to increase their root surface area to obtain more water. Our results indicate that P. euphratica seedlings are able to adapt to a range of water table conditions through plastic

  10. Effects of water depth, seasonal exposure, and substrate orientation on microbial bioerosion in the Ionian Sea (Eastern Mediterranean).

    PubMed

    Färber, Claudia; Wisshak, Max; Pyko, Ines; Bellou, Nikoleta; Freiwald, André

    2015-01-01

    The effects of water depth, seasonal exposure, and substrate orientation on microbioerosion were studied by means of a settlement experiment deployed in 15, 50, 100, and 250 m water depth south-west of the Peloponnese Peninsula (Greece). At each depth, an experimental platform was exposed for a summer period, a winter period, and about an entire year. On the up- and down-facing side of each platform, substrates were fixed to document the succession of bioerosion traces, and to measure variations in bioerosion and accretion rates. In total, 29 different bioerosion traces were recorded revealing a dominance of microborings produced by phototrophic and organotrophic microendoliths, complemented by few macroborings, attachment scars, and grazing traces. The highest bioerosion activity was recorded in 15 m up-facing substrates in the shallow euphotic zone, largely driven by phototrophic cyanobacteria. Towards the chlorophyte-dominated deep euphotic to dysphotic zones and the organotroph-dominated aphotic zone the intensity of bioerosion and the diversity of bioerosion traces strongly decreased. During summer the activity of phototrophs was higher than during winter, which was likely stimulated by enhanced light availability due to more hours of daylight and increased irradiance angles. Stable water column stratification and a resulting nutrient depletion in shallow water led to lower turbidity levels and caused a shift in the photic zonation that was reflected by more phototrophs being active at greater depth. With respect to the subordinate bioerosion activity of organotrophs, fluctuations in temperature and the trophic regime were assumed to be the main seasonal controls. The observed patterns in overall bioeroder distribution and abundance were mirrored by the calculated carbonate budget with bioerosion rates exceeding carbonate accretion rates in shallow water and distinctly higher bioerosion rates at all depths during summer. These findings highlight the relevance

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

    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 MALÅ 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.

  12. Effects of Water Depth, Seasonal Exposure, and Substrate Orientation on Microbial Bioerosion in the Ionian Sea (Eastern Mediterranean)

    PubMed Central

    Färber, Claudia; Wisshak, Max; Pyko, Ines; Bellou, Nikoleta; Freiwald, André

    2015-01-01

    The effects of water depth, seasonal exposure, and substrate orientation on microbioerosion were studied by means of a settlement experiment deployed in 15, 50, 100, and 250 m water depth south-west of the Peloponnese Peninsula (Greece). At each depth, an experimental platform was exposed for a summer period, a winter period, and about an entire year. On the up- and down-facing side of each platform, substrates were fixed to document the succession of bioerosion traces, and to measure variations in bioerosion and accretion rates. In total, 29 different bioerosion traces were recorded revealing a dominance of microborings produced by phototrophic and organotrophic microendoliths, complemented by few macroborings, attachment scars, and grazing traces. The highest bioerosion activity was recorded in 15 m up-facing substrates in the shallow euphotic zone, largely driven by phototrophic cyanobacteria. Towards the chlorophyte-dominated deep euphotic to dysphotic zones and the organotroph-dominated aphotic zone the intensity of bioerosion and the diversity of bioerosion traces strongly decreased. During summer the activity of phototrophs was higher than during winter, which was likely stimulated by enhanced light availability due to more hours of daylight and increased irradiance angles. Stable water column stratification and a resulting nutrient depletion in shallow water led to lower turbidity levels and caused a shift in the photic zonation that was reflected by more phototrophs being active at greater depth. With respect to the subordinate bioerosion activity of organotrophs, fluctuations in temperature and the trophic regime were assumed to be the main seasonal controls. The observed patterns in overall bioeroder distribution and abundance were mirrored by the calculated carbonate budget with bioerosion rates exceeding carbonate accretion rates in shallow water and distinctly higher bioerosion rates at all depths during summer. These findings highlight the relevance

  13. 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

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

    1998-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

    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.

  15. Accurate Focal Depth Determination of Oceanic Earthquakes Using Water-column Reverberation and Some Implications for the Shrinking Plate Hypothesis

    NASA Astrophysics Data System (ADS)

    Niu, F.; Huang, J.; Gordon, R. G.

    2015-12-01

    Investigation of oceanic earthquakes can play an important role in constraining the lateral and depth variations of the stress and strain-rate fields in oceanic lithosphere and of the thickness of the seismogenic layer as a function of lithosphere age, thereby providing us with critical insight into thermal and dynamic processes associated with the cooling and evolution of oceanic lithosphere. With the goal of estimating hypocentral depths more accurately, we observe clear water reverberations after the direct P wave on teleseismic records of oceanic earthquakes and develop a technique to estimate earthquake depths by using these reverberations. The Z-H grid search method allows the simultaneous determination of the sea floor depth (H) and earthquake depth (Z) with an uncertainty less than 1 km, which compares favorably with alternative approaches. We apply this method to two closely located earthquakes beneath the eastern Pacific. These earthquakes occur in ≈25 Ma-old lithosphere and were previously estimated to have very similar depths of ≈10-12 km. We find that the two events actually occurred at dissimilar depths of 2.5 km and 16.8 km beneath the seafloor, respectively within the oceanic crust and lithospheric mantle. The shallow and deep events are determined to be a thrust and normal earthquake, respectively, indicating that the stress field within the oceanic lithosphere changes from horizontal compression to horizontal extension as depth increases, which is consistent with the prediction of the lithospheric cooling model. Furthermore, we show that the P-axis of the newly investigated thrust-faulting earthquake is roughly perpendicular to that of the previously studied thrust event, consistent with the predictions of the shrinking-plate hypothesis.

  16. Accurate focal depth determination of oceanic earthquakes using water-column reverberation and some implications for the shrinking plate hypothesis

    NASA Astrophysics Data System (ADS)

    Huang, Jianping; Niu, Fenglin; Gordon, Richard G.; Cui, Chao

    2015-12-01

    Investigation of oceanic earthquakes is useful for constraining the lateral and depth variations of the stress and strain-rate fields in oceanic lithosphere, and the thickness of the seismogenic layer as a function of lithosphere age, thereby providing us with critical insight into thermal and dynamic processes associated with the cooling and evolution of oceanic lithosphere. With the goal of estimating hypocentral depths more accurately, we observe clear water reverberations after the direct P wave on teleseismic records of oceanic earthquakes and develop a technique to estimate earthquake depths by using these reverberations. The Z-H grid search method allows the simultaneous determination of the sea floor depth (H) and earthquake depth (Z) with an uncertainty less than 1 km, which compares favorably with alternative approaches. We apply this method to two closely located earthquakes beneath the eastern Pacific. These earthquakes occurred in ∼25 Ma-old lithosphere and were previously estimated to have similar depths of ∼10-12 km. We find that the two events actually occurred at dissimilar depths of 2.5 km and 16.8 km beneath the seafloor, respectively, within the oceanic crust and lithospheric mantle. The shallow and deep events are determined to be a thrust and normal earthquake, respectively, indicating that the stress field within the oceanic lithosphere changes from horizontal deviatoric compression to horizontal deviatoric tension as depth increases, which is consistent with the prediction of lithospheric cooling models. Furthermore, we show that the P-axis of the newly investigated thrust-faulting earthquake is perpendicular to that of the previously studied thrust event, consistent with the predictions of the shrinking-plate hypothesis.

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

    SciTech Connect

    Handford, C.R. )

    1990-08-01

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

  18. Using heat as a tracer to estimate the depth of rapid porewater advection below the sediment-water interface

    NASA Astrophysics Data System (ADS)

    Wilson, Alicia M.; Woodward, Gwendolyn L.; Savidge, William B.

    2016-07-01

    Rapid exchange of surface waters and porewaters in shallow sediments has important biogeochemical implications for streams and marine systems alike, but mapping these important reaction zones has been difficult. As a means of bridging the gap between the stream and submarine groundwater discharge communities we suggest that the rapid, transient mixing in this zone be called "hydrodynamic exchange". We then present a new model, MATTSI, which was developed to estimate the timing, depth and magnitude of hydrodynamic exchange below the sediment-water interface by inverting thermal time-series observations. The model uses an effective thermal dispersion term to emulate 3-D hydrodynamic exchange in a 1-D model. The effective dispersion is assumed to decline exponentially below the sediment water interface. Application of the model to a synthetic dataset and two field datasets from 50 km offshore in the South Atlantic Bight shows that exchange events can be clearly identified from thermal data. The model is relatively insensitive to realistic errors in sensor depth and thermal conductivity. Although the datasets tested here were too shallow to fully span the depth of flushing, we were able to estimate the depth of hydrodynamic exchange via sensitivity studies.

  19. 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

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

    2013-01-01

    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

  20. Cumulative soil water evaporation as a function of depth and time

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil water evaporation is an important component of the surface water balance and the surface energy balance. Accurate and dynamic measurements of soil water evaporation enhance the understanding of water and energy partitioning at the land-atmosphere interface. The objective of this study is to mea...

  1. Water column depth and light intensity modulate the zebrafish preference response in the black/white test.

    PubMed

    Córdova, Sandro Daniel; Dos Santos, Thainá Garbino; de Oliveira, Diogo Losch

    2016-04-21

    Currently, the black/white preference test has been used to evaluate anxiety-like behaviors in zebrafish. However, several inconsistent results have been reported across literature. Since animal behavior can be influenced by several environmental factors, the main goal of the present study was to investigate the influence of different water column depths and light intensities on zebrafish behavioral responses in the black/white test. On a 4cm water column depth, animals spent more time in the black than in the white compartment. However, when animals were tested in an 8cm water column, no significant difference was found. Using an inclined acrylic floor inside the aquarium, animals spent more time in the deep compartment when this was black. However, there is no difference in time spent in each compartment when the deeper compartment was white. For light intensity test, animals showed preference for the white compartment only when both compartments were illuminated with 100lx. For the others illumination settings, there was no difference in the compartment preference. In conclusion, our results suggest that variations in water column depth and light intensity can modulate zebrafish preference in the black/white test. These variations may be implicated in the discrepancies observed in literature. PMID:26960010

  2. Discharge and water-depth estimates for ungauged rivers: Combining hydrologic, hydraulic, and inverse modeling with stage and water-area measurements from satellites

    NASA Astrophysics Data System (ADS)

    Liu, Ganming; Schwartz, Franklin W.; Tseng, Kuo-Hsin; Shum, C. K.

    2015-08-01

    Anticipating future global freshwater scarcity and providing mitigation require timely knowledge of spatiotemporal dynamics of discharge for gauged and, more challengingly, ungauged rivers. This study describes a coupled hydrologic (SWAT) and hydraulic (XSECT) modeling approach set in a genetic algorithm framework for estimating discharge and water depth for ungauged rivers from space. The method was tested in the Red River of the North basin by comparing simulated discharges and depths from 2006 to 2010 to in situ observations from across the basin. Results showed that calibration using only remotely sensed data (i.e., water levels from ENVISAT altimetry and water extents from LANDSAT) along the main stem of the Red River yielded daily and monthly estimates of river discharge, which correlated to measured discharges at three gaging stations on the main stem with R2 values averaging 0.822 and 0.924, respectively. The comparisons of modeled and measured discharges were also extended to smaller tributaries, yielding a mean R2 of 0.809 over seven gaging stations. The modeling approach also provided estimates of water depth that correlated to observations at four stations with an average R2 of 0.831. We conclude that the integrated modeling approach is able to estimate discharge and water depth from space for larger ungauged rivers. This study also implies that in situ discharge data may not be necessary for successful hydrologic model calibration.

  3. Effects of water depth and substrate color on the growth and body color of the red sea cucumber, Apostichopus japonicus

    NASA Astrophysics Data System (ADS)

    Jiang, Senhao; Dong, Shuanglin; Gao, Qinfeng; Ren, Yichao; Wang, Fang

    2015-05-01

    Three color variants of the sea cucumber, Apostichopus japonicus are recognized, the red one is highly valued in the market. When the red variant is cultured in ponds in China, its body color changes from red to celadon in 3-6 months. The effects of water depth and substrate color on the growth and body color of this animal were investigated. Juveniles of red A. japonicus were cultured in cages suspended at a range of water depths (20, 50, 100, 150 and 200 cm). The specific growth rate of red sea cucumbers was significantly higher in animals cultured at deeper water layers compared with those grown at shallowers. Body weights were greatest for sea cucumbers cultured at a depth of 150 cm and their survival rates were highest at a depth of 200 cm. A scale to evaluate the color of red sea cucumbers ( R value) was developed using a Pantone standard color card. All stocked animals in the 9-month trial retained a red color, however the red body color was much more intense in sea cucumbers cultured at shallower depths, while animals suspended in deeper layers became pale. In a separate trial, A. japonicus were cultured in suspended cages with seven different colored substrates. Substrate color had a significant effect on the growth and body-color of red A. japonicus. The yield were greatest for A. japonicus cultured on a yellow substrate, followed by green > white > orange > red > black and blue. All sea cucumbers in the 7-month trial retained a red color, although the red was most intense (highest R value) in animals cultured on a blue substrate and pale (lowest R value) for animals cultured on a green substrate.

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

    SciTech Connect

    Ikenberry, T.A.

    1992-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-10-01

    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.

  6. Offshore permafrost decay and massive seabed methane escape in water depths >20 m at the South Kara Sea shelf

    NASA Astrophysics Data System (ADS)

    Portnov, A.; Mienert, J.; Cherkashov, G. A.

    2013-12-01

    We study the West-Yamal Shelf in the Kara Sea, offshore Western Russia. We present new high-resolution seismic data (2-16 kHz) and gas geochemical data from 2012 cruises. In high-resolution seismic data, we found extensive acoustic anomalies in the water column, which we interpreted to be gas (bubble) flares rising from the seafloor. These anomalies were widespread throughout the study area, but seemed to be limited to water depths > 20 meters below sea level (mbsl). One seepage site in ~6m water depth released gas that reached almost to the sea surface. The hydroacoustic anomalies are limited by the 20 m isobaths, and it may be controlled by the extension of permafrost that is still present below the seafloor at these depths providing an impermeable layer through which gas and other fluids cannot migrate. We detected acoustically transparent zones in sediments in the upper 2-5 meters below seafloor (mbsf). We interpret these acoustic anomalies to record the presence of free gas. Deeper seismic data show that acoustic anomalies in sediments near the seafloor are connected to gas chimneys that extend to depths >2000 mbsf. This suggests that gas is migrating from deeper hydrocarbon reservoirs and therefore it has very likely a thermogenic origin. In addition to the more widespread and disperse acoustically transparent zones, we discovered two prominent transparent mounds that are 1.5-2 km in diameter and that are elevated 10-15 meters above the seafloor. These features bear striking resemblance to the pingo-like features (PLF) that have been studied on the Beaufort Shelf (e.g. Shearer et al., 1971; Paull et al., 2007), and Pechora Sea (Rokos, 2009). Tentative results of numerical modelling estimate the thickness of permafrost, which was during the last sea level regression 170-300 meters thick. Based on the model of permafrost melting we state, that continuous sub-seabed permafrost may extend to water depths of ~20 m offshore creating a seal through which gas cannot

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

    NASA Astrophysics Data System (ADS)

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

    2011-02-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    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.

  9. Depth Estimation of Submerged Aquatic Vegetation in Clear Water Streams Using Low-Altitude Optical Remote Sensing.

    PubMed

    Visser, Fleur; Buis, Kerst; Verschoren, Veerle; Meire, Patrick

    2015-01-01

    UAVs and other low-altitude remote sensing platforms are proving very useful tools for remote sensing of river systems. Currently consumer grade cameras are still the most commonly used sensors for this purpose. In particular, progress is being made to obtain river bathymetry from the optical image data collected with such cameras, using the strong attenuation of light in water. No studies have yet applied this method to map submergence depth of aquatic vegetation, which has rather different reflectance characteristics from river bed substrate. This study therefore looked at the possibilities to use the optical image data to map submerged aquatic vegetation (SAV) depth in shallow clear water streams. We first applied the Optimal Band Ratio Analysis method (OBRA) of Legleiter et al. (2009) to a dataset of spectral signatures from three macrophyte species in a clear water stream. The results showed that for each species the ratio of certain wavelengths were strongly associated with depth. A combined assessment of all species resulted in equally strong associations, indicating that the effect of spectral variation in vegetation is subsidiary to spectral variation due to depth changes. Strongest associations (R²-values ranging from 0.67 to 0.90 for different species) were found for combinations including one band in the near infrared (NIR) region between 825 and 925 nm and one band in the visible light region. Currently data of both high spatial and spectral resolution is not commonly available to apply the OBRA results directly to image data for SAV depth mapping. Instead a novel, low-cost data acquisition method was used to obtain six-band high spatial resolution image composites using a NIR sensitive DSLR camera. A field dataset of SAV submergence depths was used to develop regression models for the mapping of submergence depth from image pixel values. Band (combinations) providing the best performing models (R²-values up to 0.77) corresponded with the OBRA

  10. Depth Estimation of Submerged Aquatic Vegetation in Clear Water Streams Using Low-Altitude Optical Remote Sensing

    PubMed Central

    Visser, Fleur; Buis, Kerst; Verschoren, Veerle; Meire, Patrick

    2015-01-01

    UAVs and other low-altitude remote sensing platforms are proving very useful tools for remote sensing of river systems. Currently consumer grade cameras are still the most commonly used sensors for this purpose. In particular, progress is being made to obtain river bathymetry from the optical image data collected with such cameras, using the strong attenuation of light in water. No studies have yet applied this method to map submergence depth of aquatic vegetation, which has rather different reflectance characteristics from river bed substrate. This study therefore looked at the possibilities to use the optical image data to map submerged aquatic vegetation (SAV) depth in shallow clear water streams. We first applied the Optimal Band Ratio Analysis method (OBRA) of Legleiter et al. (2009) to a dataset of spectral signatures from three macrophyte species in a clear water stream. The results showed that for each species the ratio of certain wavelengths were strongly associated with depth. A combined assessment of all species resulted in equally strong associations, indicating that the effect of spectral variation in vegetation is subsidiary to spectral variation due to depth changes. Strongest associations (R2-values ranging from 0.67 to 0.90 for different species) were found for combinations including one band in the near infrared (NIR) region between 825 and 925 nm and one band in the visible light region. Currently data of both high spatial and spectral resolution is not commonly available to apply the OBRA results directly to image data for SAV depth mapping. Instead a novel, low-cost data acquisition method was used to obtain six-band high spatial resolution image composites using a NIR sensitive DSLR camera. A field dataset of SAV submergence depths was used to develop regression models for the mapping of submergence depth from image pixel values. Band (combinations) providing the best performing models (R2-values up to 0.77) corresponded with the OBRA findings