bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimization of radiography applications using x‐ray beams emitted by compact accelerators. Part I. Monte Carlo study of the hard x‐ray spectrum
Authors: Marziani M. , Taibi A. , Di Domenico G. , Gambaccini M. 
Published: September 2009

Purpose:A 3‐year project called LABSYNC has been recently funded by the European Commission, with the aim of designing a radiation facility based on a compact light source, i.e., a laboratory‐sized commercial synchrotron, capable of accelerating electrons up to 6 or 20 MeV. An accurate spectral description of hard x rays emitted from thin targets, irradiated by electron beams circulating in the storage ring, is of primary interest for the design and the characterization of a beamline. This article, Part I, aims at optimizing some of the parameters which are critical for the design of medical applications based on the above compact light source. The goal was to evaluate the dependence of photon fluence and beam monochromaticity on electron‐beam energy, target material, and thickness.Methods:The transport of 6 and 20 MeV electrons in a thin molybdenum, rhodium, and tungsten target is studied by means of Monte Carlo simulations usingMCNPX. Configurations of the x‐ray output port, different from the default forward‐directed emission of the beam, are also investigated. A comparison with reference spectra for general diagnostic radiology and mammography is carried out.Results:It is shown that the emitted x‐ray beams can be far more intense than those generated by conventional x‐ray tubes for radiography applications. The profiles of the calculated polychromatic spectra resemble those generated by conventional x‐ray tubes, with x‐ray energies up to the energy of the incident‐electron beam. An appreciable improvement in the monochromaticity of the beams can be obtained by viewing the x‐ray emission from an output port antiparallel to the direction of the incident‐electron beam.Conclusions:The optimum target thickness for tungsten target spectra is practically constrained by a trade‐off between bremsstrahlung efficiency and focal‐spot size requirements. A larger margin for optimization of target thickness is probably available for mammographic spectra. The constraint of a backward‐directed (or, to a lesser extent, orthogonal) output port is to be considered mandatory for minimizing the high‐energy tail of the spectral distribution and keeping the radiation dose to a reasonable level. It is also fundamental to evaluate the impact of the high‐energy tail of the emitted spectra in x‐ray imaging applications, since the energy range involved is significantly beyond the diagnostic range. This topic will be dealt with in Part II of the article.
Comparison of arc‐modulated cone beam therapy and helical tomotherapy for three different types of cancer
Authors: Ulrich Silke , Sterzing Florian , Nill Simeon , Schubert Kai , Herfarth Klaus K. , Debus Jürgen , Oelfke Uwe 
Published: September 2009

Purpose:Arc‐modulated cone beam therapy (AMCBT) is a fast treatment technique deliverable in a single rotation with a conventional C‐arm shaped linac. In this planning study, the authors assess the dosimetric properties of single‐arc therapy in comparison to helical tomotherapy for three different tumor types.Methods:Treatment plans for three patients with prostate carcinoma, three patients with anal cancer, and three patients with head and neck cancer were optimized for helical tomotherapy and AMCBT. The dosimetric comparison of the two techniques is based on physical quantities derived from dose‐volume histograms.Results:For prostate cancer, the quality of dose distributions calculated for AMCBT was of equal quality as that generated for tomotherapy with the additional benefits of a faster delivery and a lower integral dose. For highly complex geometries, the plan quality achievable with helical tomotherapy could not be achieved with arc‐modulated cone beam therapy.Conclusions:Rotation therapy with a conventional linac in a single arc is capable to deliver a high and homogeneous dose to the target and spare organs at risk. Advantages of this technique are a fast treatment time and a lower integral dose in comparison to helical tomotherapy. For highly complex cases, e.g., with several target regions, the dose shaping capabilities of AMCBT are inferior to those of tomotherapy. However, treatment plans for AMCBT were also clinically acceptable.
Dose spread functions in computed tomography: A Monte Carlo study
Authors: Boone John M. 
Published: September 2009

Purpose:Current CT dosimetry employing CTDI methodology has come under fire in recent years, partially in response to the increasing width of collimated x‐ray fields in modern CT scanners. This study was conducted to provide a better understanding of the radiation dose distributions in CT.Methods:Monte Carlo simulations were used to evaluate radiation dose distributions along the axis arising from CT imaging in cylindrical phantoms. Mathematical cylinders were simulated with compositions of water, polymethyl methacrylate (PMMA), and polyethylene. Cylinder diameters from were studied. X‐ray spectra typical of several CT manufacturers (80, 100, 120, and ) were used. In addition to no bow tie filter, the head and body bow tie filters from modern General Electric and Siemens CT scanners were evaluated. Each cylinder was divided into three concentric regions of equal volume such that the energy deposited is proportional to dose for each region. Two additional dose assessment regions, central and edge locations in diameter, were included for comparisons to measurements. Dose spread functions (DSFs) were computed for a wide number of imaging parameters.Results:DSFs generally exhibit a biexponential falloff from the position. For a very narrow primary beam input , DSFs demonstrated significant low amplitude long range scatter dose tails. For body imaging conditions ( diameter in water), the DSF at the center showed at full width at tenth maximum (FWTM), while at the edge the FWTM was . Polyethylene phantoms exhibited wider DSFs than PMMA or water, as did higher tube voltages in any material. The FWTM were 80, 180, and for 10, 30, and phantom diameters, respectively, at the center in water at with a typical body bow tie filter. Scatter to primary dose ratios (SPRs) increased with phantom diameter from 4 at the center ( diameter) for a diameter cylinder to for a diameter cylinder. The SPRs increased dramatically at the center of the phantom compared to the edge. For the three equal area regions, the edge to center SPRs for a diameter phantom were , 3.5, and 6.3, respectively.Conclusions:DSFs demonstrate low amplitude long ranging tails which reach considerable distances in cylindrical phantoms. The buildup that results from these long‐ranged tails increases at the center of the field (at) with increasing scan length. The DSF distributions lend a better understanding of the trends in CT dose deposition over a range of relevant imaging parameters. The DSFs as well as other related data are available to interested parties using EPAPS at http://www.aip.org/pubservs/epaps.html.
Prediction of decadal slope changes in Canada by glacial isostatic adjustment modellingThis article is one of a series of papers published in this Special Issue on the theme GEODESY.
Authors: van der Wal Wouter , Braun Alexander , Wu Patrick , Sideris Michael G. 
Published: September 2009

In Canada, glacial isostatic adjustment (GIA) is the dominant process to cause vertical motion of the land surface. A GIA model is presented herein that can be used to predict slope changes at given locations in North America where GIA is the primary cause for vertical motion. Uncertainty in Pleistocene ice cover and viscosity in the Earth’s mantle prevent one from picking a single GIA model from the literature to predict uplift rates in the region. Therefore, in this study, a range of mantle viscosity values as well as two different ice-loading histories are used in a forward model of the GIA process. The combination of viscosities and ice model that gives the best fit to recently available continuous and episodic GPS observations is assumed to provide the best prediction of slope changes in North America. This model can be used to quantify GIA-induced vertical deformation in local geomorphologic studies. We show that the predicted differential uplift rate in the Nelson River with respect to Lake Winnipeg reaches 1 mm/year over a 200 km distance using the model that best fits the GPS data whereas the ICE-5Gv1.2/VM2 model gives a slightly larger value. The difference in uplift rate between the northern and southern shore of Lake Michigan amounts up to 3 mm/year (slightly larger than the ICE-5Gv1.2/VM2 model), which could lead to a change in shorelines of tens of metres horizontally over a period of 100 years.
EQUILIBRIUM CONFIGURATIONS OF TWO-DIMENSIONAL STRESSED DOMAINS ON THE SURFACE OF ISOTROPIC AND CUBIC CRYSTALS
Authors: PRÉVOT GEOFFROY , CROSET BERNARD 
Published: September 2009

In this paper, we derive analytical formulations of the elastic energy of a stressed domain on a crystalline substrate. Taking care of the singularity of the elastic Green function at r = 0, we obtain a universal expression for the isotropic case. By using the analogy between electric dipolar and elastic interactions, we developed similar analytical calculations for the (001) surface of a cubic crystal.We showed that the anisotropy of the boundary energy and the anisotropy of the substrate govern the shape of the domains, favoring either compact shapes or stripe configurations. The analytical approach adopted in this paper also allows us to discuss the role of elastic anisotropy for the existence of attractive interactions between domains.
Development of a Methanol SOFC APU Demonstration System
Authors: Rechberger Juergen , Schauperl Richard , Hansen John Bo̸gild , Larsen Peter K. 
Published: September 2009

In mid 2007 it was decided to develop a SOFC APU demonstration system in the power range of 7 kWel and fuelled by methanol. Target application of the system should be an APU on board of ships. The main development goals were: •	demonstration of fully automated and transient operation •	electrical efficiency > 40% •	thermally integrated in a gas-tight box •	start-up time below 1 hour •	project duration 8 months
Multidecadal Trends in Instrumental SST and Coral Proxy Sr/Ca Records
Authors: Scott Robert B. , Holland Christina L. , Quinn Terrence M. 
Published: September 2009

Abstract
Historical ship observations of sea surface temperature (SST) from 1850 to present were used to compute linear 40-yr trends for all 5° latitude by 5° longitude grid cells with sufficient data. Trends from throughout the twentieth century were centered about a 7 mK yr−1 warming trend with standard deviation 14 mK yr−1. Although different with high statistical significance from a distribution with zero mean, the warming trends were not unusual in amplitude compared to the available nineteenth-century trends. Trends at the same grid points from the latter half of the nineteenth century were distributed about near-zero mean with standard deviation 17 mK yr−1. The shift in mean is robust to accounting for the biases arising from differing observational methods prior to 1942. The 40-yr trends from the latter half of the twentieth century were centered about 10 ± 4 mK yr−1 and more clearly distinct from earlier trends. Linear 40-yr trends were computed at different locations and times from all publicly available coral skeleton records of the concentration ratio of Sr to Ca. The pre-twentieth-century distribution of 40-yr trends in the Sr/Ca ratio was significantly different from the twentieth-century trends, consistent with the warming found in the instrumental SST. The interpretation of the coral Sr/Ca 40-yr trends cannot yet be reduced to a single factor. Major uncertainties were due to (i) the correlation of modern Sr/Ca records with instrumental SST being dominated by seasonal effects, with correlations on time scales longer than the annual cycle much lower, and (ii) the poor quality instrumental SST on long time scales in remote locations. Based on the NOAA extended reconstructed instrumental SST dataset since 1870 and 499 yr of Sr/Ca data from 13 different coral records, the authors found a Pearson correlation coefficient r = −0.77 for 40-yr low-pass-filtered times series. Interpreting the change in distribution of trends in Sr/Ca will require further study of the factors affecting Sr/Ca on time scales longer than seasonal.
Localization of Deep Water Formation: Role of Atmospheric Moisture Transport and Geometrical Constraints on Ocean Circulation
Authors: Ferreira David , Marshall John , Campin Jean-Michel 
Published: September 2009

Abstract
A series of coupled atmosphere–ocean–ice aquaplanet experiments is described in which topological constraints on ocean circulation are introduced to study the role of ocean circulation on the mean climate of the coupled system. It is imagined that the earth is completely covered by an ocean of uniform depth except for the presence or absence of narrow barriers that extend from the bottom of the ocean to the sea surface. The following four configurations are described: Aqua (no land), Ridge (one barrier extends from pole to pole), Drake (one barrier extends from the North Pole to 35°S), and DDrake (two such barriers are set 90° apart and join at the North Pole, separating the ocean into a large basin and a small basin, connected to the south). On moving from Aqua to Ridge to Drake to DDrake, the energy transports in the equilibrium solutions become increasingly “realistic,” culminating in DDrake, which has an uncanny resemblance to the present climate. Remarkably, the zonal-average climates of Drake and DDrake are strikingly similar, exhibiting almost identical heat and freshwater transports, and meridional overturning circulations. However, Drake and DDrake differ dramatically in their regional climates. The small and large basins of DDrake exhibit distinctive Atlantic-like and Pacific-like characteristics, respectively: the small basin is warmer, saltier, and denser at the surface than the large basin, and is the main site of deep water formation with a deep overturning circulation and strong northward ocean heat transport. A sensitivity experiment with DDrake demonstrates that the salinity contrast between the two basins, and hence the localization of deep convection, results from a deficit of precipitation, rather than an excess of evaporation, over the small basin. It is argued that the width of the small basin relative to the zonal fetch of atmospheric precipitation is the key to understanding this salinity contrast.
Finally, it is argued that many gross features of the present climate are consequences of two topological asymmetries that have profound effects on ocean circulation: a meridional asymmetry (circumpolar flow in the Southern Hemisphere; blocked flow in the Northern Hemisphere) and a zonal asymmetry (a small basin and a large basin).
Radiometric and Spectral Characteristics of the ScaRaB-3 Instrument on Megha-Tropiques: Comparisons with ERBE, CERES, and GERB
Authors: Viollier Michel , Raberanto Patrick 
Published: September 2009

Abstract
The Indian–French Megha-Tropiques mission, scheduled to be launched in 2010, will carry radiation and microwave sensors to study the energy and water cycle in the tropics. The radiation sensor, the third model of the Scanner for Radiation Budget (ScaRaB-3), is dedicated to the earth’s radiation budget, the difference between the solar absorbed flux and the terrestrial emitted flux. These fluxes are calculated from satellite measurements of outgoing shortwave (SW) and longwave (LW) radiances using angular distribution models (ADMs). For practical reasons, the LW radiation is calculated from the difference between a total (T) channel (0.2–100 μm) and an SW channel (0.2–4 μm). With the ADM application, the radiance calibration remains the most critical issue in the radiation budget estimation. The 1% accuracy goal is difficult to achieve, specifically in the SW domain. The authors explain their efforts to improve the radiometric calibration of ScaRaB-3. The internal calibration module is improved: the sensor is switched between SW and T channels by rotating the filter wheel on which the SW filter is now installed. Because the pyroelectric detector is sensitive to the thermal effect of the electromagnetic radiation independently of its spectral range, this plan allows calibrating the SW channel as a T channel by viewing a blackbody. Indeed, the transfer of the T calibration to the SW domain requires perfect knowledge of the total spectral response and of the transmittance of the SW filter, which is discussed in the article. Spectral errors are calculated with updated data. In the SW domain, they are found to be the smallest compared to those of the Earth Radiation Budget Experiment (ERBE), the Clouds and the Earth’s Radiant Energy System (CERES), and the Geostationary Earth Radiation Budget (GERB).
Observations of Gulf of Tehuantepec Gap Wind Events from QuikSCAT: An Updated Event Climatology and Operational Model Evaluation
Authors: Brennan Michael J. , Cobb Hugh D. , Knabb Richard D. 
Published: September 2009

Abstract
A climatology of gale- and storm-force gap wind events in the Gulf of Tehuantepec is constructed for the first time using 10 yr of ocean surface vector wind data from the SeaWinds scatterometer on board NASA’s Quick Scatterometer (QuikSCAT) satellite. These wind events are among the most severe that occur within the National Hurricane Center’s (NHC) area of marine forecasting responsibility outside of tropical cyclones. The 10-yr climatology indicates that on average 11.9 gale-force events and 6.4 storm-force events occur in the Gulf of Tehuantepec each cold season. About 84% of these events occur between November and March, with the largest number of gale-force events occurring in December. Storm-force events are most frequent in January.
Operational numerical weather prediction model forecasts of these events from the NCEP Global Forecast System (GFS) and North American Mesoscale (NAM) models were evaluated during the 2006/07 cold season. Results show that neither model is able to consistently forecast storm-force Tehuantepec wind events; however, the models do have some ability to forecast gale-force events. The NAM model showed a significant increase in probability of detection over the GFS, possibly due to increased horizontal and vertical resolutions as well as differences in boundary layer mixing and surface flux schemes.
Finally, the prospects of observing these gap wind events in the post-QuikSCAT era will be discussed.
Towards Development of a Performance Standard for Assessing the Effectiveness of Wall-Window Interface Details to Manage Rainwater Intrusion
Authors: Lacasse M. A. , Cornick S. M. , Rousseau M. , Armstrong M. , Ganapathy G. , Nicholls M. , Plescia S. 
Published: September 2009

Abstract
Laboratory water spray testing identifies the performance of a component or assembly under a specified set of simulated wind-driven rain conditions. Well-developed water spray test protocols can also help identify where an assembly is vulnerable to water entry, the test loads at which water entry occurs, and whether the water entry is managed by the installation details in such a way that it does not result in within-wall damage. This paper presents a proposed laboratory test protocol for assessing the effectiveness of wall-window interface details with regard to management of rainwater and provides a rationale for a performance-based approach to the evaluation method. An overview of the test approach is provided, and details of the test apparatus and test specimen are given, including information on implementation of the test method. Examples of testing performed according to the proposed protocol are provided. Finally additional tests for evaluating the performance of installation details are suggested. The additional tests are for field evaluation of installation details and for laboratory evaluation of installation details with regard to the risk of condensation along window frames.
An Analysis of Head Impact Profiles and Safe Hockey Behaviors in Youth Hockey Players
Authors: McPherson Moira N. , Montelpare William J. , Keightley Michelle , Reed Nicholas , Sutherland Malcolm , Taha Tim , McAuliffe Jim , Baker Joseph R. , Cubos Jeff , Faught Brent 
Published: September 2009

Abstract
Although injury risk factors can be described in biomechanical terms, previous research has not described the relationship between style of play and the frequency and magnitude of head impacts. This paper is focused on the analysis of head impact profiles and safe hockey behaviors demonstrated during contact situations in a cohort of 13 Bantam-aged minor hockey players. Head impacts sustained at 27 home games during the 2006–2007 season were measured using the Head Impact Telemetry System (HITS). Hockey helmets (Canadian Standards Association approved) were equipped with six linear accelerometers and a wireless system that transmitted data to a receiver interfaced with a computer. Nine games were recorded using a field videography system to capture player collisions. A HITS profile was determined, which included the number of impacts (&gt;10 g) (“g”=m/sec2) by player, the total number of impacts, the average number of impacts per game, and the mean linear acceleration value for all impacts per player. Based on these results, ten taped trials for the players sustaining greater than 180 total impacts over the season were qualitatively analyzed using a checklist to examine the safe hockey behaviors associated with body contacts. We captured 2753 head impacts over the season, with the average number of impacts per player per game ranging from 3 to 16 with a mean linear acceleration of 15.8 g (standard deviation=13.76). The checklist of safe hockey behaviors was used to analyze skating performance for a group of five players who experienced more than 180 impacts, with some impact magnitudes exceeding 98 g. In general, differences in indicators of skating skill, body position prior to check/contact, and actions during the contact were observed. While specific players may be predisposed to head impacts of a greater frequency and magnitude because of their style of play, these characteristics can be changed to reduce risk of potential injury.