bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sliding characteristic and material compressibility of human lung: Parametric study and verification
Authors: Al‐Mayah A. , Moseley J. , Velec M. , Brock K. K. 
Published: September 2009

Purpose:To find and verify the optimum sliding characteristics and material compressibility that provide the minimum error in deformable image registration of the lungs.Methods:A deformable image registration study has been conducted on a total of 16 lung cancer patients. Patient specific three dimensional finite element models have been developed to model left and right lungs, chest (body), and tumor based on 4D CT images. Contact surfaces have been applied to lung‐chest cavity interfaces. Experimental test data are used to model nonlinear material properties of lungs. A parametric study is carried out on seven patients, 20 conditions for each, to investigate the sliding behavior and the tissue compressibility of lungs. Three values of coefficient of friction of 0, 0.1, and 0.2 are investigated to model lubrication and sliding restriction on the lung‐chest cavity interface. The effect of material compressibility of lungs is studied using Poisson's ratios of 0.35, 0.4, 0.45, and 0.499. The model accuracy is examined by calculating the difference between the image‐based displacement of bronchial bifurcation points identified in the lung images and the calculated corresponding model‐based displacement. Furthermore, additional bifurcation points around the tumor and its center of mass are used to examine the effect of the mentioned parameters on the tumor localization.Results:The frictionless contact model with 0.4 Poisson's ratio provides the smallest residual errors of, , and in the LR, AP, and SI directions, respectively. Similarly, this optimum model provides the most accurate location of the tumor with residual errors of , , and in all three directions. The accuracy of this model is verified on an additional nine patients with average errors of , , and in the LR, AP, and SI directions, respectively.Conclusions:The optimum biomechanical model with the smallest registration error is when frictionless contact model and 0.4 Poisson's ratio are applied. The overall accuracies of all bifurcation points in all 16 patients including tumor points are, , and in the LR, AP, and SI directions, respectively.
Assessment of three dead detector correction methods for cone‐beam computed tomography
Authors: Nelms David W. , Shukla Hemant I. , Nixon Earl , Bayouth John E. , Flynn Ryan T. 
Published: September 2009

Purpose:Dead detectors due to manufacturing defects or radiation damage in the electronic portal imaging devices (EPIDs) used for cone‐beam computed tomography (CBCT) can lead to image degradation and ring artifacts. In this work three dead detector correction methods were assessed using megavoltage CBCT (MVCBCT) as a test system, with the goals of assessing the relative effectiveness of the three methods and establishing the conditions for which they fail.Methods:MVCBCT projections acquired with four linacs at 8 and 60 MU (monitor units) were degraded with varying percentages (2%–95%) of randomly distributed dead single detectors (RDSs), randomly distributed dead detector clusters (RDCs) of 2 mm diameter, and nonrandomly distributed dead detector disks (NRDDs) of varying diameter (4–16 mm). Correction algorithms were bidirectional linear interpolation (BLI), quad‐directional linear interpolation (QLI), and a Laplacian solution (LS) method. Correction method failure was defined to occur if ring artifacts were present in the reconstructed phantom images from any linac or if the modulation transfer function (MTF) for any linac dropped below baseline with a value, calculated with the two sample test, of less than 0.01.Results:All correction methods failed at the same or lower RDC/RDS percentages and NRDD diameters for the 60 MU as for the 8 MU cases. The LS method tended to outperform or match the BLI and QLI methods. If ring artifacts anywhere in the images were considered unacceptable, the LS method failed for 60 MU at RDS, RDC, and NRDD. If ring artifacts within 4 mm longitudinally of the phantom section interfaces were considered acceptable, the LS method failed for 60 MU at RDS, RDC, and NRDD. LS failed due to MTF drop for 60 MU at RDS, RDC, and NRDD.Conclusions:The LS method is superior to the BLI and QLI methods, and correction algorithm effectiveness decreases as imaging dose increases. All correction methods failed first due to ring artifacts and second due to MTF drop. If ring artifacts in axial slices within a 4 mm longitudinal distance from phantom section interfaces are acceptable, statistically significant loss in spatial resolution does not occur until over 25% of the EPID is covered in randomly distributed dead detectors, or NRDDs of 4 mm diameter are present.
An iterative technique to segment PET lesions using a Monte Carlo based mathematical model
Authors: Nehmeh S. A. , El‐Zeftawy H. , Greco C. , Schwartz J. , Erdi Y. E. , Kirov A. , Schmidtlein C. R. , Gyau A. B. , Larson S. M. , Humm J. L. 
Published: September 2009

Purpose:The need for an accurate lesion segmentation tool in PET is a prerequisite for the estimation of lesion response to therapy, for radionuclide dosimetry, and for the application of PET to radiotherapy planning. In this work, the authors have developed an iterative method based on a mathematical fit deduced from Monte Carlo simulations to estimate tumor segmentation thresholds.Methods:The GATE software, a GEANT4 based Monte Carlo tool, was used to model the GE Advance PET scanner geometry. Spheres ranging between 1 and in diameters were simulated in a high and in diameter cylinder. The spheres were filled with water‐equivalent density and simulated in both water and lung equivalent background. The simulations were performed with an infinite, , and target‐to‐background ratio (T/B). A mathematical fit describing the correlation between the lesion volume and the corresponding optimum threshold value was then deduced through analysis of the reconstructed images. An iterative method, based on this mathematical fit, was developed to determine the optimum threshold value. The effects of the lesion volume and T/B on the threshold value were investigated. This method was evaluated experimentally using the NEMA NU2‐2001 IEC phantom, the ACNP cardiac phantom, a randomly deformed aluminum can, and a spheroidal shape phantom implemented artificially in the lung, liver, and brain of patient PET images. Clinically, the algorithm was evaluated in six lesions from five patients. Clinical results were compared to CT volumes.Results:This mathematical fit predicts an existing relationship between the PET lesion size and the percent of maximum activity concentration within the target volume (or threshold). It also showed a dependence of the threshold value on the T/B, which could be eliminated by background subtraction. In the phantom studies, the volumes of the segmented PET targets in the PET images were within 10% of the nominal ones. Clinically, the PET target volumes were also within 10% of those measured from CT images.Conclusions:This iterative algorithm enabled accurately segment PET lesions, independently of their contrast value.
TG‐43 U1 based dosimetric characterization of model 67‐6520 Cs‐137 brachytherapy source
Authors: Meigooni Ali S. , Wright Clarissa , Koona Rafiq A. , Awan Shahid B. , Granero Domingo , Perez‐Calatayud Jose , Ballester Facundo 
Published: September 2009

Purpose:Brachytherapy treatment has been a cornerstone for management of various cancer sites, particularly for the treatment of gynecological malignancies. In low dose rate brachytherapy treatments, sources have been used for several decades. A new source design has been introduced (model 67‐6520, source B3‐561) by Isotope Products Laboratories (IPL) for clinical application. The goal of the present work is to implement the TG‐43 U1 protocol in the characterization of the aforementioned source.Methods:The dosimetric characteristics of the IPL source are measured using LiF thermoluminescent dosimeters in a Solid Water™ phantom material and calculated using Monte Carlo simulations with the GEANT4 code in Solid Water™ and liquid water. The dose rate constant, radial dose function, and two‐dimensional anisotropy function of this source model were obtained following the TG‐43 U1 recommendations. In addition, the primary and scatter dose separation(PSS) formalism that could be used in convolution/superposition methods to calculate dose distributions around brachytherapy sources in heterogeneous media was studied.Results:The measured and calculated dose rate constants of the IPL source in Solid Water™ were found to be and , respectively. The agreement between these two methods was within our experimental uncertainties. The Monte Carlo calculated value in liquid water of the dose rate constant was . Similarly, the agreement between measured and calculated radial dose functions and the anisotropy functions was found to be within ±5%. In addition, the tabulated data that are required to characterize the source using the PSS formalism were derived.Conclusions:In this article the complete dosimetry of the newly designed IPL source following the AAPM TG‐43 U1 dosimetric protocol and the PSS formalism is provided.
Modeling topographical density for geoid determinationThis article is one of a series of papers published in this Special Issue on the themeGEODESY.
Authors: Kingdon Robert , Vaníček Petr , Santos Marcelo 
Published: September 2009

In geoid computation, effects of real three-dimensional topographic masses on the Earth’s gravity field must be accurately quantified and, in the Stokes–Helmert scheme, replaced with effects of those masses condensed on the geoid. The most comprehensive modern schemes for evaluation of topographical effects account for terrain effects, use a spherical model of topography, and incorporate two-dimensionally varying models of topographical mass density. In this contribution, we employ a three-dimensionally varying model of topographical density. We use Newton’s integration to determine the direct topographical effect (DTE) on gravity and primary indirect topographical effect (PITE) on gravity potential. Lastly, we apply Stokes’ integration to calculate the DTE, PITE, and secondary indirect topographical effect (SITE) on geoidal height. We focus here on validation of our results and demonstration of our software’s capabilities. We present results for the simple geometrical shape of a disc under various rotations and for the anomalous density of lake waters. Effects on geoidal height for these simulations reach centimetre level, up to 2.2 cm in magnitude. For a simulation of the effects of neglected mass anomalies of the lakes, we find results reaching 0.8 cm in magnitude. We examine the behavior of our results as calculated using various step sizes for numerical integration and by comparing numerical results with analytical results for the specific case of a disc. These results suggest that the maximum percent error of our results is about 23.5% for the DTE on gravity and 7.6% for the PITE on gravity potential.
A late-glacial – Holocene palaeoecological record from Pye Lake on the eastern shore of Nova Scotia, CanadaGeological Survey of Canada Contribution 20080395.
Authors: Mott Robert J. , Walker Ian R. , Palmer Samantha L. , Lavoie Martin 
Published: September 2009

Pollen and chironomid analyses and radiocarbon dating at Pye Lake on the eastern shore of Nova Scotia are used to outline the vegetation and climatic history of the area. The coast was deglaciated prior to ∼12 200 14C BP (14 300 cal BP), and herbaceous tundra vegetation invaded the area. Midge-inferred maximum summer surface-water temperatures in the lake ranged between 9 and 11 °C. Subsequent gradual warming to ∼18 °C by 10 800 14C BP (12 725 cal BP) favoured the migration of a variety of herbaceous and shrub taxa into the region. Rapid cooling to ∼10 °C saw vegetation revert to herbaceous tundra communities. This interval, related to the Younger Dryas cold interval of the North Atlantic and Europe, lasted until ∼10 000 14C BP (11 630 cal BP). The climate then warmed again to conditions similar to those that prevailed immediately before onset of Younger Dryas cooling. Further warming saw successive tree species migrate into the area until, by the mid-Holocene, the forests contained most of the taxa prevalent today. Since ∼3500 years ago, cooling of the climate has favoured conifer species over broad-leaved taxa. Agriculture and logging practices in the last 150 years have altered the forest composition, but pollen analysis of the most recent sediments cannot resolve these changes adequately.
SOLUTIONS OF THE DIVERGENCE AND ANALYSIS OF THE STOKES EQUATIONS IN PLANAR HÖLDER-α DOMAINS
Authors: DURÁN RICARDO G. , LÓPEZ GARCÍA FERNANDO 
Published: September 2009

If Ω ⊂ ℝn is a bounded domain, the existence of solutions [Formula: see text] of div u = f for f ∈ L2(Ω) with vanishing mean value, is a basic result in the analysis of the Stokes equations. In particular, it allows to show the existence of a solution [Formula: see text], where u is the velocity and p the pressure. It is known that the above-mentioned result holds when Ω is a Lipschitz domain and that it is not valid for arbitrary Hölder-α domains. In this paper we prove that if Ω is a planar simply connected Hölder-α domain, there exist solutions of div u = f in appropriate weighted Sobolev spaces, where the weights are powers of the distance to the boundary. Moreover, we show that the powers of the distance in the results obtained are optimal. For some particular domains with an external cusp, we apply our results to show the well-posedness of the Stokes equations in appropriate weighted Sobolev spaces obtaining as a consequence the existence of a solution [Formula: see text] for some r < 2 depending on the power of the cusp.
Si Wafer Analysis of Light Elements by TXRF
Authors: Sasamori Sato , Meirer Florian , Zoeger Norbert , Streli Christina , Kregsamer Peter , Smolek Stephan , Mantler Claus , Wobrauschek Peter 
Published: September 2009

The determination of light elements (Z<14) requires a set of precautions and experimental modifications in comparison to the analysis of higher Z elements. All measurements have to be performed in vacuum around 1mbar pressure as achieved from a membrane pump. A high resolution energy dispersive detector with ultra thin window and efficiency high enough from 200eV upward is required. The analysis is performed under x-ray total reflection conditions (TXRF) and mechanical components for translation and rotation have to be foreseen for the adjustment.	The measurement set-up consisted of a modified vacuum chamber suitable to accommodate 6"- 8" wafers on a rotatable sample carrier and will be described. Droplets containing Mg and two types of elemental matrices consisting of a) medium Z elements (Ti-Zn) and b) light elements (Na, Mg, Al) were prepared on 6" Si wafers in the laboratory of Siltronic AG in Freiberg. For the low Z elements concentrations of 10ng, 100ng, and 1000ng were taken and for the medium Z elements a variable concentration range from 1ng to 100ng was chosen. It was assumed that the presence of medium Z elements causes a stronger absorption of the light elements' fluorescence, whereas light elements affect each other non-serious. The results with respect to the made assumptions and detection limits for the new set-up will be shown.
Electrode Properties of Pr0.7Sr0.3Fe0.8Al0.2O3-δ Thin Film Prepared by Pulsed Laser Deposition
Authors: Takahashi Hiroo , Takamura Hitoshi 
Published: September 2009

A mixed conductive Pr0.7Sr0.3Fe0.8Al0.2O3-δ (PSFA) thin film has been prepared by using pulsed laser deposition (PLD) and its electrochemical properties have been investigated. A dense PSFA target for PLD was prepared at 1130 oC for 10 h. By using the target, 285 nm-thick PSFA thin film was deposited on an 8mol%Y2O3-doped ZrO2 substrate at 625 oC. The PSFA thin film was well crystallized and its grain size was in the range of 5 to 10 nm. The PSFA thin film showed an area specific resistance (ASR) of 0.37	Ω•cm2 at 900 oC. The activation energy of ASR was approximately 1.6 eV at temperature range of 600 to 900 oC.
Simulation and Interpretation of the Genesis of Tropical Storm Gert (2005) as Part of the NASA Tropical Cloud Systems and Processes Experiment
Authors: Braun Scott A. , Montgomery Michael T. , Mallen Kevin J. , Reasor Paul D. 
Published: September 2009

Abstract
Several hypotheses have been put forward for the mechanisms of generation of surface circulation associated with tropical cyclones. This paper examines high-resolution simulations of Tropical Storm Gert (2005), which formed in the Gulf of Mexico during NASA’s Tropical Cloud Systems and Processes Experiment, to investigate the development of low-level circulation and its relationship to the precipitation evolution. Two simulations are examined: one that better matches available observations but underpredicts the storm’s minimum sea level pressure and a second one that somewhat overintensifies the storm but provides a set of simulations that encapsulates the overall genesis and development characteristics of the observed storm. The roles of convective and stratiform precipitation processes within the mesoscale precipitation systems that formed Gert are discussed. During 21–25 July, two episodes of convective system development occurred. In each, precipitation system evolution was characterized by intense and deep convective upward motions followed by increasing stratiform-type vertical motions (upper-level ascent, low-level descent). Potential vorticity (PV) in convective regions was strongest at low levels while stratiform-region PV was strongest at midlevels, suggesting that convective processes acted to spin up lower levels prior to the spinup of middle levels by stratiform processes. Intense vortical hot towers (VHTs) were prominent features of the low-level cyclonic vorticity field. The most prominent PV anomalies persisted more than 6 h and were often associated with localized minima in the sea level pressure field. A gradual aggregation of the cyclonic PV occurred as existing VHTs near the center continually merged with new VHTs, gradually increasing the mean vorticity near the center. Nearly concurrently with this VHT-induced development, stratiform precipitation processes strongly enhanced the mean inflow and convergence at middle levels, rapidly increasing the midlevel vorticity. However, the stratiform vertical motion profile is such that while it increases midlevel vorticity, it decreases vorticity near the surface as a result of low-level divergence. Consequently, the results suggest that while stratiform precipitation regions may significantly increase cyclonic circulation at midlevels, convective vortex enhancement at low to midlevels is likely necessary for genesis.
Intraseasonal Variation of Winter Precipitation over the Western United States Simulated by 14 IPCC AR4 Coupled GCMs
Authors: Lin Jia-Lin , Shinoda Toshiaki , Qian Taotao , Han Weiqing , Roundy Paul , Zheng Yangxing 
Published: September 2009

Abstract
This study evaluates the intraseasonal variation of winter precipitation over the western United States in 14 coupled general circulation models (GCMs) participating in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). Eight years of each model’s twentieth-century climate simulation are analyzed. The focus is on the two dominant intraseasonal modes for the western U.S. precipitation: the 40-day mode and the 22-day mode.
The results show that the models tend to overestimate the northern winter (November–April) seasonal mean precipitation over the western United States and Canada. The models also tend to produce overly strong intraseasonal variability in western U.S. wintertime precipitation, in spite of the overly weak tropical intraseasonal variability in most of the models. All models capture both the 40-day mode and the 22-day mode, usually with overly large variances. For the 40-day mode, models tend to reproduce its deep barotropic vertical structure and three-cell horizontal structure, but only 5 of the 14 models capture its northward propagation, and only 2 models simulate its teleconnection with the Madden–Julian oscillation in the tropical Pacific. For the 22-day mode, 8 of the 14 models reproduce its coherent northward propagation, and 9 models capture its teleconnection with precipitation in the tropical Pacific.
PARSIVEL Snow Observations: A Critical Assessment
Authors: Battaglia Alessandro , Rustemeier Elke , Tokay Ali , Blahak Ulrich , Simmer Clemens 
Published: September 2009

Abstract
The performance of the laser-optical Particle Size Velocity (PARSIVEL) disdrometer is evaluated to determine the characteristics of falling snow. PARSIVEL’s measuring principle is reexamined to detect its limitations and pitfalls when applied to solid precipitation. This study uses snow observations taken during the Canadian Cloudsat/Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) Validation Project (C3VP) campaign, when two PARSIVEL instruments were collocated with a single two-dimensional disdrometer (2-DVD), which allows more detailed observation of snowflakes. When characterizing the snowflake size, PARSIVEL instruments inherently retrieve only one size parameter, which is approximately equal to the widest horizontal dimension (more accurately with large snowflakes) and that has no microphysical meaning. Unlike for raindrops, the equivolume PARSIVEL diameter—the PARSIVEL output variable—has no physical counterpart for snowflakes.
PARSIVEL’s fall velocity measurement may not be accurate for a single snowflake particle. This is due to the internally assumed relationship between horizontal and vertical snow particle dimensions. The uncertainty originates from the shape-related factor, which tends to depart more and more from unity with increasing snowflake sizes and can produce large errors. When averaging over a large number of snowflakes, the correction factor is size dependent with a systematic tendency to an underestimation of the fall speed (but never exceeding 20%).
Compared to a collocated 2-DVD for long-lasting events, PARSIVEL seems to overestimate the number of small snowflakes and large particles. The disagreement between PARSIVEL and 2-DVD snow measurements can only be partly ascribed to PARSIVEL intrinsic limitations (border effects and sizing problems), but it has to deal with the difficulties and drawbacks of both instruments in fully characterizing snow properties.
Resistance of Adhesive Bonding of Ultra-High Performance Concrete to Hygrothermal, Corrosive, and Freeze-Thaw Cycling Environments
Authors: Krelaus R. , Wisner G. , Freisinger-Schadow S. , Schmidt M. , Böhm S. , Dilger K. 
Published: September 2009

Abstract
Ultra-high performance concrete (UHPC) with its unique material properties is suitable for the application of adhesive bonding as a joining technique. The results presented in this paper were generated as part of a research project aimed at investigating the properties of UHPC adhesive joints in terms of reliability, safety, and load bearing capacity. Fourteen adhesives were tested for strength and durability considering varying conditions of substrate surface pretreatment and different UHPC compositions. Tests under hygrothermal, freezing, and salt-spraying exposures were performed to investigate the long-term durability under different climatic conditions.