Reference Depth Research Articles

Nearshore Bathymetry Based on ICESat-2 and Multispectral Images: Comparison Between Sentinel-2, Landsat-8, and Testing Gaofen-2

Accurate bathymetric maps are essential to understand marine and coastal ecosystems. With the development of satellite and sensor technology, satellite-derived bathymetry (SDB) has been widely used to measure the depth of nearshore waters. Employment of physics-based methods requires a series of optical parameters of the water column and seafloor, which limits the application of these methods to shallow-water bathymetry. Due to convenience, low costs, and high efficiency, empirical methods based on <i>in situ</i> measurements and satellite imagery are increasingly used for nearshore bathymetry. These measurements are required to calibrate empirical models, so that reasonable accuracy can be achieved. The Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2), equipped with the advanced topographic laser altimeter system, provides a novel opportunity for nearshore bathymetry. Using the new measurement strategy of photon counting, ICESat-2 can provide accurate bathymetric points from spaceborne observations, which can be used in place of <i>in situ</i> water depth data. In this study, ICESat-2 bathymetric points and multispectral images were used to train four typical models and produce bathymetric maps for Shanhu Island, Ganquan Island, and Lingyang Reef in the Xisha Islands of China. We evaluated the bathymetric results by comparing them with reference depth data from airborne light detection and ranging. All models had a satisfactory accuracy, as well as multimodel and multisource image consistency. With the ICESat-2 bathymetric points, SDB is no longer limited by <i>in situ</i> measurements. Hence, this approach could be extended to a larger scale to obtain nearshore bathymetric maps of coastal areas, surrounding islands, and reefs using free and open-access satellite data.

Testing scenarios on geological models: Local interface insertion in a 2D mesh and its impact on seismic wave simulation

In this work, we propose a local updating method to test different contact depth scenarios and assess their impact on wave propagation in the subsurface. We propose to locally modify a 2D geological model and run time-dependent elastic simulations. The input model triangulation is conforming to geological structures. The 2D meshed model is locally updated, which means that only the reservoir compartment is modified. Several model geometries are generated by inserting a new interface, in this paper a gas–water contact that is defined by a scalar field. We quantitatively evaluate the impact of the gas–water contact depth on elastic wave propagation. We run the numerical simulations with Hou10ni2D code, which is based on a Discontinuous Galerkin method. The simulation results are compared to a reference depth by computing the L2-norm at a set of seismic receivers. Results show a consistent behavior: we observe a positive correlation between the depth difference and global L2-norm for all receivers. This approach could therefore be integrated into an inversion loop to determine the position of the fluid contact and reduce uncertainties in the reservoir model from a few seismic sensors. The algorithms are available on Github and distributed under a GPL license, allowing reproducibility.

Toward accurate evaluation of bulk hardness from nanoindentation testing at low indent depths

Estimations of bulk hardness from nanoindentation are frequently subject to considerable uncertainties due to indentation size effects (ISE), pileup effects, and potential influence of surface quality or test methods. This study examined materials science principles of nanoindentation test methods to enable accurate prediction of bulk hardness for a series of high purity Fe and Fe-(3–25 wt%) Cr alloys. These materials were tested in as-annealed and thermally aged (100–900 h at 475 ℃ to produce Cr-rich α’ precipitates) conditions. Nanoindentation with a Berkovich indenter at constant strain rate (0.05–0.5 /s) and constant loading rate conditions provided comparable bulk equivalent hardness (H0) extracted by Nix-Gao model, indicating a weak strain rate sensitivity at room temperature. Results from electropolished and fine mechanically polished samples gave comparable measured hardness. Pileup corrections produced a 5–14% correction to H0 which agreed with the experimental bulk Vickers hardness within ∼10% for most tested materials. The microstructural model-predicted and measured strength values agreed for aged samples. A derived analytic expression demonstrates that an ISE error, associated with inappropriate methods such as hardness ratios or changes at a reference depth, would be as large as 60% in estimated bulk hardness for the investigated Fe-Cr alloys.

Impact of the warm eddy on planktonic ciliate, with an emphasis on tintinnids as bioindicator species

Mesoscale eddies are a common feature of world oceans. However, their influence on microzooplankton has not been well studied. This study investigated the impact of warm eddies (originating from the Kuroshio Current) on planktonic ciliates in the northern South China Sea and the western North Pacific. We found more tintinnid species in warm eddies than in reference areas in both seas. All species categorized as abundant (maximum abundance > 5 ind. L−1 and occurrence frequency > 10%) could be divided into subsurface-peak and surface-peak groups (highest abundance appeared in subsurface and surface layers, respectively). Subsurface-peak tintinnid species vertical distribution together with temperature-salinity-plankton diagrams at each sampling points revealed higher abundance in warm eddies than in reference areas, which suggested that they can act as warm eddy bioindicator species. Surface-peak tintinnid species were mainly distributed in both warm eddy and reference areas, depth and temperature were the main influence factors. The vertical distribution in warm eddies showed a bimodal pattern in both the South China Sea and North Pacific, with abundance peaks in surface and subsurface layers; whereas in reference areas, abundance peaks in surface layers. The average abundance of ciliate and tintinnids in subsurface layers were higher in warm eddies than in reference areas. Our study contributed to a better understanding of the impact of the warm eddy on microzooplankton and tintinnids function as usefully bioindicator species. Further research is needed to fully understand the ecological influence of eddies on the microzooplankton community.

Aspects about bouncing of plough caused by random

In this paper the author deals aspects about the vertical motion (named bouncing) of a tractor with plough mounted on the rear frame, during displacement over the random excitation surface of the agricultural land. Final results of the simulation process, performed on the model of tractor-plough with 3 degree of freedoms, show the difference between digging depth function as velocity motion and longitudinal profile of the terrain. Thus, the deviation of the plough depth from the reference depth is evaluated.

Electrodes Adaptive Model in Estimating the Depth of Motor Unit: A Motor Unit Action Potential Based Approach.

High-density surface electromyography (EMG) has been proposed to overcome the lower selectivity with respect to needle EMG and to provide information on a wide area over the considered muscle. Motor units decomposed from surface EMG signal of different depths differ in the distribution of action potentials detected in the skin surface. We propose a noninvasive model for estimating the depth of motor unit. We find that the depth of motor unit is linearly related to the Gaussian RMS width fitted by data points extracted from motor unit action potential. Simulated and experimental signals are used to evaluate the model performance. The correlation coefficient between reference depth and estimated depth is 0.92 ± 0.01 for simulated motor unit action potentials. Due to the symmetric nature of our model, no significant decrease is detected during the electrode selection procedure. We further checked the estimation results from decomposed motor units, the correlation coefficient between reference depth and estimated depth is 0.82 ± 0.07. For experimental signals, high discrimination of estimated depth vector is detected across gestures among trials. These results show the potential for a straightforward assessment of depth of motor units inside muscles. We discuss the potential of a non-invasive way for the location of decomposed motor units.

Binaural amplitude modulation fusion as a function of modulation depth

Binaural fusion occurs when two different signals presented dichotically are perceived as one sound. In previous studies, binaural fusion was studied for stimuli differing in pitch. In this pilot study, binaural fusion was measured for amplitude-modulated tones differing in amplitude modulation (AM) depth in normal-hearing listeners. AM fusion ranges were measured with dichotic AM tones of matched carrier and AM rate but different modulation depths: specifically a reference signal with a fixed AM depth presented at the left ear, and a comparison signal with AM depth varied across trials presented at the right ear. Subjects were asked if they heard one or two sounds. AM fusion ranges were calculated as the range of comparison AM depths that fused with the reference AM depth. Carrier frequencies tested were 500 and 1600 Hz and AM rates tested were 16 and 64 Hz. Preliminary data showed that the closer the comparison depth is to the reference depth, the more likely the subject is to perceive one sound. In other words, the AM fusion range is centered on the reference AM depth. [This research was funded by NIH-NIDCD-R01-DC013307 and supported by the SURIEA program.]

SATELLITE-DERIVED BATHYMETRY USING CONVOLUTIONAL NEURAL NETWORKS AND MULTISPECTRAL SENTINEL-2 IMAGES

Abstract. Satellite-Derived Bathymetry (SDB) has been used in many applications related to coastal management. SDB can efficiently fill data gaps obtained from traditional measurements with echo sounding. However, it still requires numerous training data, which is not available in many areas. Furthermore, the accuracy problem still arises considering the linear model could not address the non-relationship between reflectance and depth due to bottom variations and noise. Convolutional Neural Networks (CNN) offers the ability to capture the connection between neighbouring pixels and the non-linear relationship. These CNN characteristics make it compelling to be used for shallow water depth extraction. We investigate the accuracy of different architectures using different window sizes and band combinations. We use Sentinel-2 Level 2A images to provide reflectance values, and Lidar and Multi Beam Echo Sounder (MBES) datasets are used as depth references to train and test the model. A set of Sentinel-2 and in-situ depth subimage pairs are extracted to perform CNN training. The model is compared to the linear transform and applied to two other study areas. Resulting accuracy ranges from 1.3 m to 1.94 m, and the coefficient of determination reaches 0.94. The SDB model generated using a window size of 9x9 indicates compatibility with the reference depths, especially at areas deeper than 15 m. The addition of both short wave infrared bands to the four visible bands in training improves the overall accuracy of SDB. The implementation of the pre-trained model to other study areas provides similar results depending on the water conditions.

GoRG: Towards a GPU-Accelerated Multiview Hyperspectral Depth Estimation Tool for Medical Applications.

HyperSpectral (HS) images have been successfully used for brain tumor boundary detection during resection operations. Nowadays, these classification maps coexist with other technologies such as MRI or IOUS that improve a neurosurgeon’s action, with their incorporation being a neurosurgeon’s task. The project in which this work is framed generates an unified and more accurate 3D immersive model using HS, MRI, and IOUS information. To do so, the HS images need to include 3D information and it needs to be generated in real-time operating room conditions, around a few seconds. This work presents Graph cuts Reference depth estimation in GPU (GoRG), a GPU-accelerated multiview depth estimation tool for HS images also able to process YUV images in less than 5.5 s on average. Compared to a high-quality SoA algorithm, MPEG DERS, GoRG YUV obtain quality losses of −0.93 dB, −0.6 dB, and −1.96% for WS-PSNR, IV-PSNR, and VMAF, respectively, using a video synthesis processing chain. For HS test images, GoRG obtains an average RMSE of 7.5 cm, with most of its errors in the background, needing around 850 ms to process one frame and view. These results demonstrate the feasibility of using GoRG during a tumor resection operation.

Skin dose assessment at diagnostic and therapeutic photon energies: A Monte Carlo study on TLDs

In radiotherapy but also as a part of quality assurance in diagnostic imaging, assessment of radiation dose to the skin of the patient is of particular importance. While skin dose is recommended to be measured at a reference depth of 70 μm, in practice in both diagnostic radiology as well as therapeutic applications, the dosimeter is placed on the skin surface, the measured dose depending in large part on dosimeter thickness. Thermoluminescent dosimeters (TLDs) are commonly applied as skin dosimeters, most of the commercial forms being thicker than 140 μm, also with a density greater than that of soft tissue, accordingly representing in effective point of measurement deeper than 70 μm. On the other hand, Monte Carlo (MC) simulations can be used to accurately calculate the dose at an intended depth. In this work we first validate our MC simulations, comparison being made with a previously published correction factor for LiF TLD of dimensions 3 × 3 × 0.1 mm3. Then correction factors to convert the dose measured by various commercial LiF-based TLDs (with thicknesses ranging from 0.15 to 1 mm) to skin dose at 70 μm depth are calculated for RQR reference diagnostic photon spectra and some common MV photon therapy spectra. These results are useful for correction of TLD responses in various clinical situations.

Assessment of skin doses in small field radiotherapy for 6 MV photons and beam spectral analysis at skin surface: an EGSnrc based Monte Carlo study.

This study aims at the estimation of skin doses during small field radiotherapy with 6 MV photons and analysis of beam spectra at skin surface. The EGSnrc Monte Carlo code was used for spectral analysis and dose scoring in a water phantom. Percent skin dose (PSD) was calculated at a depth of 70µm (relative to 10cm depth), and the effects of field size, collimation, source-to-surface distance, and tissue inhomogeneity (bone/air) below the skin were evaluated. Low-energy photons and contaminant electrons from the machine head or back-scattered from underlying tissue were found to be the major contributors to skin dose. As the field size was reduced, the beam hardened, while the photon and electron fluences at the skin decreased compared to those at the reference depth of 10cm. This resulted in a PSD reduction for fields smaller than the reference field size. Multi leaf collimators increased the PSD (up to 4%) while variation in source-to-skin dose showed a negligible effect. A substantial increase in PSD has been observed (up to 6%) when high Z material like bone was placed below the skin. In contrast, air as underlying material decreased the skin dose. The skin dose varied considerably with various clinical and geometric parameters. It is concluded that, although the skin doses were low for small fields compared to those for the reference field, skin doses may become substantial when escalated target doses are delivered with multi leaf collimators. Moreover, the presence of high Z materials such as bones or metallic implants below the skin can result in significant enhancement of the skin dose.

Passive Protection of Unarmoured Objects

This article presents problems related to passive composite protection of unarmoured objects (helicopters, vehicles, etc.). It is focused on building and testing the different add-on armours (panels) protecting unarmoured objects against small-arms armour piercing projectiles (kinetic energy - KE). It has been illustrated how to increase ballistic protection of composite armours with minimum mass for unarmoured objects. The selection of appropriate materials and their parameters affects the improvement of the protection capability of these panels. The different parameters of ceramic samples (Al2O3, SiC, Ti3SiC2, B4C) which were used for the panels are presented. Panels sized of 100×100 mm contained the different types of layers, eg. polyethylene, aluminum sheet and small sized ceramics plates (50×50 mm and thickness of 6 mm, 8 mm and 9 mm), etc. The tested panels were placed in a small frame and the rear surfaces of the panels were at a distance from „witness RHA” (Rolled Homogeneous Armour). The protection capability of panels for all types of tests were defined with the use of 5.56×45 mm SS109 HC projectiles (STANAG 4569), which reference depth of penetration was DP ref=8 mm RHA.

Understanding the effects of Digital Elevation Model resolution in urban fluvial flood modelling

With the extensive use of 2D flood models, the resolution and quality of Digital Elevation Models (DEMs) have come under greater focus especially in urban hydrology. One of the major research areas, in this regard, is the effect of DEM resolution on flood modelling. This study first investigates the root causes of the impact of DEM resolution on urban fluvial flood modelling outputs using DEMs with grid resolutions ranging from 1 m to 50 m. The study then investigates how DEM resolution affects the definition and characterisation of the river channel and the consequences of this for the modelled results. For this purpose, a separate set of merged DEMs was generated where the river channel as defined by the 1 m resolution DEM is merged with coarser resolution DEMs. Data obtained during the flood event caused by Storm Desmond (2015) in Cockermouth (Cumbria, UK) was used for this study. The HEC-RAS 2D model was used for all of the simulations. The benchmark model obtained with the 1 m resolution DEM was calibrated using measured water levels at two locations within the rivers. Results show that there is a 30% increase in flood extent from 58.9 ha to 79.0 ha and a 150% increase in mean flood depth from 1.74 m to 4.30 m when the resolution reduces from a 1 m grid to a 50 m grid. The main reason for this is the increasing lack of definition of the river channel with an associated reduction in the estimated depth of the river resulting in reduced river channel conveyance. This then leads to an increase in the flood extent and depth especially in the immediate vicinity of the river. This effect is amplified when the DEM grid size is greater than the river width. When the 1 m resolution DEM for the river channel is used in conjunction with coarser resolution DEMs for the surrounding areas (merged DEMs), there is a significant improvement in the agreement between the modelled and the reference case (obtained from the benchmark model) flood extents and depths. The use of merged DEMs reduces the error in mean flood depth from 90% to 4% and reduces the overall RMSE in flood depths from 2.6 m to 0.9 m at 30 m resolution. The use of merged DEMs, where a higher resolution DEM is used to characterise the river channel in conjunction with, for example, a 30 m resolution DEM (e.g., the freely available NASA Shuttle Radar Topography Mission DEMs) for the wider area could be a cost-effective solution for locations where higher resolution DEMs may not be available.

Application of radiochromic gel dosimetry to commissioning of a megavoltage research linear accelerator for small-field animal irradiation studies.

To develop and implement an efficient and accurate commissioning procedure for small-field static beam animal irradiation studies on an MV research linear accelerator (Linatron-M9) using radiochromic gel dosimetry. The research linear accelerator (Linatron-M9) is a 9MV linac with a static fixed collimator opening of 5.08cm diameter. Lead collimators were manually placed to create smaller fields of 2×2cm2 , 1×1cm2 , and 0.5×0.5cm2 . Relative dosimetry measurements were performed, including profiles, percent depth dose (PDD) curves, beam divergence, and relative output factors using various dosimetry tools, including a small volume ionization chamber (A14), GAFCHROMIC™ EBT3 film, and Clearview gel dosimeters. The gel dosimeter was used to provide a 3D volumetric reference of the irradiated fields. The Linatron profiles and relative output factors were extracted at a reference depth of 2cm with the output factor measured relative to the 2×2cm2 reference field. Absolute dosimetry was performed using A14 ionization chamber measurements, which were verified using a national standards laboratory remote dosimetry service. Absolute dosimetry measurements were confirmed within 1.4% (k=2, 95% confidence=5%). The relative output factor of the small fields measured with films and gels agreed with a maximum relative percent error difference between the two methods of 1.1 % for the 1×1cm2 field and 4.3 % for the 0.5×0.5cm2 field. These relative errors were primarily due to the variability in the collimator positioning. The measured beam profiles demonstrated excellent agreement for beam size (measured as FWHM), within approximately 0.8mm (or less). Film measurements were more accurate in the penumbra region due to the film's finer resolution compared with the gel dosimeter. Following the van Dyk criteria, the PDD values of the film and gel measurements agree within 11% in the buildup region starting from 0.5cm depth and within 2.6 % beyond maximum dose and into the fall-off region for depths up to 5cm. The 2D beam profile isodose lines agree within 0.5mm in all regions for the 0.5×0.5cm2 and the 1×1cm2 fields and within 1mm for the larger field of 2×2cm2 . The 2D PDD curves agree within approximately 2% of the maximum in the typical therapy region (1-4cm) for the 1×1cm2 and 2×2cm2 and within 5% for the 0.5×0.5cm2 field. This work provides a commissioning process to measure the beam characteristics of a fixed beam MV accelerator with detailed dosimetric evaluation for its implementation in megavoltage small animal irradiation studies. Radiochromic gel dosimeters are efficient small-field relative dosimetry tools providing 3D dose measurements allowing for full representation of dose, dosimeter misalignment corrections and high reproducibility with low inter-dosimeter variability. Overall, radiochromic gels are valuable for fast, full relative dosimetry commissioning in comparison to films for application in high-energy small-field animal irradiation studies.

Elastic Wave Vector Decomposition for Common-Shot Multicomponent Data Using Pure Wave Equation in Transversely Isotropic Media

Anisotropic elastic wave vector decomposition for common-shot multicomponent data is a critical step in multicomponent seismic exploration. It is more difficult than the separation for elastic wavefield snapshots because the spatial derivatives along vertical direction cannot be calculated directly. In this letter, we propose an effective workflow to implement elastic wave vector decomposition for common-shot multicomponent data based on the pure-wave equation in transversely isotropic (TI) media. First, we extrapolate the multicomponent data backward in time to a reference surface using an anisotropic elastic wave equation, implement wave-mode separation by the projection of the extrapolated anisotropic elastic wavefields onto the polarization vectors of P- and S-wave-modes, and record the separated pure-wave data at the reference depth. Second, we extrapolate the separated anisotropic pure-wave data forward in time using the anisotropic pure-wave equations, perform the vector decomposition by the projection of the extrapolated pure-wave wavefields onto the polarization vectors of P- and S-modes, and record the vector anisotropic pure-wave data at the recording surface. This method can produce vector pure-mode data from the anisotropic medium with relatively high accuracy. Synthetic examples show the feasibility of this method.

Challenges to Accurate Evaluation of Bulk Hardness from Nanoindentation Testing at Low Indent Depths

Estimations of bulk hardness from nanoindentation data are frequently subject to considerable uncertainties, due to indentation size effects, potential pileup effects, and potential influence of surface quality or test methods. In this study, we examined materials science principles of nanoindentation test methods to enable accurate prediction of bulk hardness for a series of high purity Fe and Fe alloys containing 3-25 wt. %Cr. These materials were tested in as-annealed and thermally aged (100-900 hours at 475 oC for 14-25 wt. %Cr) conditions to produce Cr-rich a’ precipitates of varying size and density (bulk Vickers hardness values of ~50 to 350 VHN). Nanoindentation performed with a Berkovich indenter using constant strain rate (0.05 to 0.5 /s) and constant loading rate test methods provided comparable bulk equivalent hardness (H0) extracted by Nix-Gao model, indicating a weak strain rate sensitivity of the investigated materials at room temperature. Results from electropolished and fine mechanically polished samples were found to give comparable measured hardness. Conversely, material pileup adjacent to the indented area produced a 7-20% correction to the indent contact area. The Nix-Gao fitted nanoindentation H0 after pileup corrections agreed quantitatively better with the bulk Vickers hardness than the uncorrected H0 values. The model-predicted (dispersed barrier hardening superposition) and measured strength values agreed for aged Fe18Cr, indicating that Nix-Gao model combined with pileup corrections significantly improved the accuracy of hardness evaluation by nanoindentation. Analytic and experimental analyses demonstrate that inappropriate methods such as hardness ratios or changes at a reference depth (applied in many prior nanoindentation studies) can cause quantitative errors in bulk hardness estimates as large as 60% due to indentation size effects.

Modeling of digital marketing systems construction using olap – technologies

The provision of information to the marketing information system is investigated in this paper. The collection of information on the server side and on network nodes is considered. It is stated that the addition of any information collection software to the server is not possible or can slow down the server. It is proposed to place sensors in network nodes on the approach to the server, which unloads the server from unnecessary software. An example of such Web Traffic Warehouse system is considered. Here the work is carried out at the level of protocols and data collection takes place at the level of TCP/IP packets. Three different approaches to the analysis of transactions are analyzed: identification of transactions taking into account the visits duration, identification of transactions by the method of maximum reference depth and division of transactions according to temporal principles. The scheme of the system of operative processing of Internet data on the basis of OLAP-technologies which is based on the principle of collecting operative data from various sources which then are cleared, integrated and put in relational storage is constructed. Also, the definition of OLAP as a set of tools for multidimensional analysis of data stored in the repository is investigated. It provides the company with the most convenient and fast means of accessing, viewing and analyzing business information, and provides the user with natural, intuitive data model, organizing them into multidimensional cubes, the axes of the multidimensional coordinate system are the main attributes of the analyzed business process. The problem of integration of data warehouses (accounting system) with formation systems (data showcases) is analyzed. Based on the analysis, the model of the distribution-order-sale data show window is built, which is based on two types of tables – fact tables and measurement tables is constructed. Thus, the table of sales facts in the developed system contains such fields as Cusomerfact ID, Salesperson, Product ID, Quantity Sold, Discount, Total Amount, etc. Due to the model it is highlighted that while creating show windows there is the organization of three key stages – obtaining data from the source systems, converting them into the desired form and then loading them into the target system.

Effects of Shallow Saline Groundwater Table Depth and Evaporative Flux on Soil Salinity Dynamics using Hydrus-1D

Soil salinization is a major environmental problem and critical concern in arid and semiarid regions. Hydrus-1D model was used to simulate effects of shallow saline groundwater table depth and evaporative flux on soil salinity movement in a saline environment. After successful calibration and validation with recorded soil moisture and soil salinity data, the model was used to evaluate two hypothetical scenarios for managing soil salinity, i.e., with 5 groundwater table depths (WTD) (WTD as on 2015, 25% and 50% rise; 25% and 50% decline in WTD based on the 2015 reference depth) and 3 different evaporative flux conditions (25, 50 and 75% reduction in evaporative flux). The model was calibrated, validated and run for scenarios with 2015 weather and WTD condition for the periods of 288 days. During calibration periods, root mean square error (RMSE) value of soil moisture content was 0.023 cm3 cm−3 and for soil salinity was 2.58 dS m−1, while during validation period RMSE of 0.023 cm3 cm−3 and 1.5 dS m−1, respectively, was recorded for soil moisture and soil salinity. Simulation results indicated that summer season (March to May, 60–150 Julian days) is the most important time to control soil salinity in this region. Considerable upward salt movement occurred during this period with 25 and 50% rise in groundwater table depth. Average root zone soil salinity increased by 6 and 12 dS m−1 when WTD raised by 25 and 50%, respectively, but negligible change in soil salinity was observed when groundwater table declined by 25 and 50%. The effective way to control this upward salt movement was reducing evaporative demands. Simulation study indicated that reducing evaporative flux of 25, 50 and 75% reduced profile soil salinity by 3.53, 6.95 and 12.38 dS m−1, respectively, during peak summer period.

Calibration of MTT assay in proton beams using radiochromic films.

This study provides methodology of calibrating as well as controlling the output for an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) colorimetric assay irradiated in a low energy proton beam using EBT3-model GAFCHROMICTM film, without correcting for quenching effect. A calibrated Markus ionization chamber was used to measure the depth dose and beam output for 26.5 MeV protons produced by a CS30 cyclotron. A time-controlled aluminum cylinder was added in front of the horizontal beam-exit serving as a radiation shutter. Following the TRS-398 reference dosimetry protocol for proton beams, the output was calibrated in water at a reference depth of 3 mm. EBT3 film was calibrated for doses up to 8 Gy at the same depth. To verify the dose distribution for each 96-well MTT assay plate, EBT3 film was placed at the reference depth during irradiation and cell doses were scaled by measured percent depth dose (PDD) data. The radiochromic film dosimetry system in this study provides dose measurements with an uncertainty better than 3.3% for doses higher than 1 Gy. From a single exposure and utilizing the Gaussian shape of the beam, multiple dose points can be obtained within different wells of the same plate ranging from 6.9 Gy (sigma ∼4%) in the central well, and 2 Gy (sigma ∼8%) for wells positioned closer to the periphery. We described a methodology for radiochromic film-based dose monitoring system, using low-energy protons, which can be used for the MTT assay in any proton beam, except within Bragg peak region.

Dosimetry formalism and calibration procedure for electronic brachytherapy sources in terms of absorbed dose to water

The LNE-LNHB has developed a methodology to standardize electronic brachytherapy sources in terms of absorbed dose to water. It is based on the measurement of the air-kerma rate at a given distance from the source and the Monte Carlo calculation of a conversion factor. This factor converts the air-kerma in measurement conditions into absorbed dose to water at a 1 cm reference depth in a water phantom. As a first application, the method was used to calibrate a Zeiss INTRABEAM system equipped with its 4 cm diameter spherical applicator. The absorbed-dose rate value obtained in the current study was found significantly higher than that provided by the manufacturer in line with the observations already reported by a few other teams.