bluuebunny/crossref_metadata_2025_split huggingface dataset:
Middle East climate simulation and dominant precipitation processes
Authors: Evans Jason P. , Smith Ronald B. , Oglesby Robert J. 
Published: November 2004

AbstractThe ability of both the ECMWF‐TOGA analyses and regional model RegCM2 to simulate the climate of the Middle East is examined. The climate of the region displays high spatial, seasonal and interannual variability, providing a strong test of a climate model's abilities. The higher resolution of RegCM2, compared with the ECMWF analyses, allows it to capture the spatial variability of temperature and precipitation better despite model biases being present. Both RegCM2 and the analyses have a cold bias, exacerbated in RegCM2 by a bias present in the prescribed sea‐surface‐temperature forcing. RegCM2 does not capture the annual cycle of precipitation on the Black and Caspian Sea coasts, where very steep topography exists, nor on the eastern Mediterranean coast, where the coastal mountains are not resolved. RegCM2 does capture the seasonal cycle in the Fertile Crescent and Zagros Mountains, where it is strongly influenced by a plateau circulation above the Iranian plateau. It is shown that accurate simulation of precipitation in these regions requires the correct simulation of storm tracks, topographic interactions and atmospheric stability. RegCM2 is better able to simulate the interannual variability averaged over the entire domain compared with the ECMWF analyses; however, they both have difficulty reproducing the interannual variability in particular subregions. It is also shown that processes controlling the seasonality of precipitation differ in different subregions and are often different from the processes controlling interannual variability. This suggests that, in order to model precipitation successfully, a horizontal scale that allows differentiation of precipitation zones dominated by different precipitation processes, both seasonally and interannually, is required. Copyright © 2004 Royal Meteorological Society
Study of the adsorption of benzimidazole and 2‐mercaptobenzothiazole on an iron surface by confocal micro‐Raman spectroscopy
Authors: Wang G. , Harrison A. , Li X. , Whittaker G. , Shi J. , Wang X. , Yang H. , Cao P. , Zhang Z. 
Published: November 2004

AbstractBenzimidazole (BIMH) and 2‐mercaptobenzothiazole (HMBT) dissolved in ethanol were chosen for the investigation of the interaction between organic molecules and surface atoms of iron or iron oxide by confocal micro‐Raman spectroscopy. Both BIMH and HMBT show enhanced and highly structured spectra in the 200–1500 cm−1 region when the iron is at a potential of ca −0.7 to −0.9 V in a neutral medium. BIMH had a weak interaction with the iron surface in a basic medium but it was chemically adsorbed in a neutral medium. HMBT was chemically adsorbed on the iron via the exocyclic S and N atoms in acidic and neutral solutions, whereas in basic media it was bound electrostatically. Copyright © 2004 John Wiley & Sons, Ltd.
New Developments in Photoinitiators
Authors: Dietliker Kurt , Jung Tunja , Benkhoff Johannes , Kura Hisatoshi , Matsumoto Akira , Oka Hidetaka , Hristova Daniela , Gescheidt Georg , Rist Günther 
Published: November 2004

AbstractNew developments of photoinitiators are the base for the further extension of the radiation curing technology. Three different approaches are presented: The optimized combination of a bisacylphosphine oxide photoinitiator with a suitable stabilizer package allows the UV curing of clear coatings with an excellent performance in outdoor use. The design of new oxime ester derivatives allowed the introduction of a new tailor‐made photoinitiator for color filter resists applications that considerably improves the color quality of the color filter. A novel photoinitiator class capable of releasing strong amine bases opens new opportunities for expanding radiation curing into resins types that crosslink by base‐catalyzed processes.
Water Soluble, Photocurable Resins for Rapid Prototyping Applications
Authors: Stampfl J. , Wöß A. , Seidler S. , Fouad H. , Pisaipan A. , Schwager F. , Liska R. 
Published: November 2004

AbstractRapid Prototyping (RP) is a suitable manufacturing method for fabricating structures with high geometric complexity and heavily undercut features. A special class of such structures which cannot easily be fabricated with traditional manufacturing methods are cellular materials [1].Rapid Prototyping allows the fabrication of cellular materials on a similar size scale like in natural material‐structures (e.g. trabecular bone). By using appropriate moulding techniques, these structures can be fabricated out of a wide variety of materials (polymers, ceramics, composites). In this work, several RP techniques are investigated regarding their suitability for the fabrication of cellular solids. The main focus is on using digital light projection (DLP, a variant of stereolithography) in combination with gelcasting [2] as a moulding technique. Besides using commercial light‐sensitive resins, a class of newly developed water soluble resins has been evaluated regarding its usability as sacrificial mould material. These water soluble resins are compatible with a wide range of moulding techniques and therefore offer new routes for the fabrication of complex shapes out of more advanced materials than it is possible with currently used manufacturing techniques.
Bifunctional Adhesion Promoter for Grafting Polypyrrole Films on Metal/Metal Oxide Surfaces
Authors: Oberoi Sonia , Jähne Evelin , Adler Hans‐Jürgen P. 
Published: November 2004

AbstractA new class of pyrrole derivatives, ω‐[(3‐phenyl) pyrrol‐1‐yl] alkyl phosphonic acids with long chains of 10 and 12 carbon atoms were synthesised to graft polypyrrole layers on metal/metal oxide surfaces. These compounds are bifunctional containing two reactive moieties, pyrrole as the polymerisable group and phosphonic acid as the anchoring group. Contact angle measurements and X‐ray photoelectron spectroscopy (XPS) confirmed adsorption with phosphonic acid group attached to the surface. Surface plasmon resonance (SPR) spectroscopy indicated that adsorption starts in seconds and is completed in few hours. Adsorption is followed by surface induced polymerisation with further monomer. We obtained dense and homogeneous polypyrrole films, which were characterised for their morphology and thickness by atomic force microscopy (AFM). The derivatives form a strongly bonded composite of metal with polymer.
Properties of Star‐Branched Polymer Chains Near a Surface
Authors: Sikorski Andrzej , Romiszowski Piotr 
Published: November 2004

AbstractWe considered two model systems of star‐branched polymers near an impenetrable surface. The model chains were constructed on a simple cubic lattice. Each star polymer consisted of f = 3 arms of equal length and the total number of segments was up to 799. The excluded volume effect was included into these models only and therefore the system was studied at good solvent conditions. In the first model system polymer chain was terminally attached with one arm to the surface. The grafted arm could slide along the surface. In the second system the star‐branched chain was adsorbed on the surface and the strength of adsorption was were varied. The simulations were performed using the dynamic Monte Carlo method with local changes of chain conformations. The internal and local structures of a polymer layer were determined. The lateral diffusion and internal mobility of star‐branched chains were studied as a function of strength of adsorption and the chain length. The lateral diffusion and internal mobility of star‐branched chains were studied as a function of strength of adsorption and the chain length. It was shown that the behavior of grafted and weakly adsorbed chains was similar to that of a free three‐dimensional polymer, while the strongly adsorbed chains behave as a two‐dimensional system.
Computer Simulations of Grafted Amphiphilic Polymer Chains
Authors: Sikorski Andrzej , Romiszowski Piotr 
Published: November 2004

AbstractWe designed a simple model of a polymer layer formed by many chains. Each chain was built on a flexible [310] lattice. All chains were terminally attached to an impenetrable surface and the lateral motion of the entire chain was enabled. The force field used consisted of the contact potential regarding attractive interaction as well as the excluded volume effect. between polymer segments with short‐range repulsion. It was assumed that the chains were built of hydrophilic and hydrophobic segments. The Monte Carlo simulations of this model were carried out using the Metropolis algorithm. The influence of both the grafting density and the temperature on static properties of the system were studied and discussed. The size, shape and structure of the polymer film formed near the surface were determined. The low temperature structures formed by the brush were described.
Electrospinning P(LLA‐CL) Nanofiber: A Tubular Scaffold Fabrication with Circumferential Alignment
Authors: Mo Xiumei , Weber Hans‐Joachim 
Published: November 2004

AbstractIn this paper a synthetic Poly(L‐lactic‐co‐ϵ‐caprolactone) [P(LLA‐CL)] (75:25) copolymer has been fabricated into a nanofibrous structure by electrospinning. The polymer crystal structure has been investigated by DSC and x‐ray diffraction method. During electrospinning at room temperature, a crystallization of LLA sequence in the P(LLA‐CL) copolymer could not form, while a relatively regular arrangement of CL sequence was observed. In order to obtain a tubular scaffold, a rotating mandrel was designed to collect the fiber, so that the tubular scaffold can be retrieved from the mandrel with an inner diameter same as that of the outer diameter of the mandrel. An auxiliary electrode with a sharp edge and a negative charge was set under the mandrel to guide the fiber deposition on the mandrel. When the sharp edge bar was vertical to the rotating axle of the mandrel and just beneath the spinning nozzle, nanofibers with circumferential alignment were obtained. With this method it is possible to obtain a tubular scaffold with suitable fiber alignment for blood vessel tissue engineering.
Surface wave scattering by a rectangular impedance cylinder located on a reactive plane
Authors: Tayyar İsmail Hakkı , Aksoy Serkan , Alkumru Ali 
Published: November 2004

AbstractThe electromagnetic scattering of the surface wave by a rectangular impedance cylinder located on an infinite reactive plane is considered for the case that the impedances of the horizontal and vertical sides of the cylinder can have different values. Firstly, the diffraction problem is reduced into a modified Wiener–Hopf equation of the third kind and then solved approximately. The solution contains branch‐cut integrals and two infinite sets of constants satisfying two infinite systems of linear algebraic equations. The approximate analytical or numerical evaluations of corresponding integrals and numerical solution of the linear algebraic equation systems are obtained for various values of parameters such as the surface reactance of the plane, the vertical and horizontal wall impedances, the width and the height of the cylinder. Copyright © 2004 John Wiley & Sons, Ltd.
Reduction of residual dipolar interaction in cartilage by spin‐lock technique
Authors: Akella Sarma V.S. , Regatte Ravinder R. , Wheaton Andrew J. , Borthakur Arijitt , Reddy Ravinder 
Published: November 2004

AbstractThe influence of radiofrequency (RF) spin‐lock pulse on the laminar appearance of articular cartilage in MR images was investigated. Spin‐lock MRI experiments were performed on bovine cartilage plugs on a 4.7 Tesla small‐bore MRI scanner, and on human knee cartilage in vivo on a 1.5 Tesla clinical scanner. When the normal to the surface of cartilage was parallel to B0, a typical laminar appearence was exhibited in T2‐weighted images of cartilage plugs, but was absent in T1ρ‐weighted images of the same plugs. At the “magic angle” orientation (when the normal to the surface of cartilage was 54.7° with respect to B0), neither the T2 nor the T1ρ images demonstrated laminae. At the same time, T1ρ values were greater than T2 at both orientations throughout the cartilage. T1ρ dispersion (i.e., the dependence of the relaxation rate on the spin‐lock frequency ω1) was observed, which reached a steady‐state value of close to 2 kHz in both parallel and magic‐angle orientations. These results suggest that residual dipolar interaction from motionally‐restricted water and relaxation processes, such as chemical exchange, contribute to T1ρ dispersion in cartilage. Further, one can reduce the laminar appearance in human articular cartilage by applying spin‐lock RF pulses, which may lead to a more accurate diagnosis of degenerative changes in cartilage. Magn Reson Med 52:1103–1109, 2004. © 2004 Wiley‐Liss, Inc.
RF‐induced temperature elevation along metallic wires in clinical magnetic resonance imaging: Influence of diameter and length
Authors: Armenean Cristina , Perrin Emmanuel , Armenean Mircea , Beuf Olivier , Pilleul Frank , Saint‐Jalmes Hervé 
Published: November 2004

AbstractWith the development of interventional MRI, heating of biological tissues along the metallic wires in the MRI scanner has become an important issue. To assess thermal response to RF exposure during MRI, we studied the temperature elevation near nonmagnetic metallic wires. All tests were performed on a 1.5 T clinical scanner. Four experiments were conducted to investigate the effects of the wire diameter, the excitation flip angle, the temperature distribution along the wire, and the wire length. Electromagnetic simulations of the experimental setup were made with the use of commercial method of moments (MoM) software and numerical simulations of Hallén's equations. Comparisons between measured and calculated values of the electric field are presented. This study demonstrates that 1) temperature decreases with the diameter of the wire,2)temperature increases quadratically with the excitation flip angle, 3) heating occurs not only at the tip but also along the wire, and 4) the heating peaks are not obtained for the classical resonant length multiple of λ/4 (where λ is the RF field wavelength). In addition, significant and rapid heating increases were observed in the close vicinity of the wire. Magn Reson Med 52:1200–1206, 2004. © 2004 Wiley‐Liss, Inc.
Calibration of echo‐planar 2D‐selective RF excitation pulses
Authors: Oelhafen Markus , Pruessmann Klaas P. , Kozerke Sebastian , Boesiger Peter 
Published: November 2004

AbstractEcho‐planar radiofrequency (RF) pulses (EPP) are increasingly being used for 2D‐selective excitation in MRI. Pulse schemes of this kind are susceptible to eddy‐current effects, timing imperfections, and anisotropy of the gradient system. As a consequence, practical EPP implementations have been restricted to robust fly‐back strategies that use only every other leg of the echo‐planar trajectory for RF transmission. The present work is dedicated to enabling forward‐backward EPP with RF transmission during each k‐space segment, hence doubling the pulses' time efficiency. This is accomplished by comprehensive pulse calibration based on preparatory measurements of the system imperfections, including potential gradient anisotropy. The effectiveness of the method is demonstrated in vitro and in vivo. By doubling the speed of k‐space coverage, the proposed method enhances the potential of EPP for numerous applications. For example, motion‐sensitive techniques benefit from shorter feasible echo times (TEs) and improved excitation profiles resulting from reduced in‐pulse motion. In sequences with fast repetition, shorter EPP help reduce the overall scan duration. Alternatively, the higher time efficiency of forward‐backward EPP can enhance their spatial selectivity. Magn Reson Med 52:1136–1145, 2004. © 2004 Wiley‐Liss, Inc.
Point spread function mapping with parallel imaging techniques and high acceleration factors: Fast, robust, and flexible method for echo‐planar imaging distortion correction
Authors: Zaitsev M. , Hennig J. , Speck O. 
Published: November 2004

AbstractEcho‐planar imaging (EPI) is an ultrafast magnetic resonance (MR) imaging technique prone to geometric distortions. Various correction techniques have been developed to remedy these distortions. Here improvements of the point spread function (PSF) mapping approach are presented, which enable reliable and fully automated distortion correction of echo‐planar images at high field strengths. The novel method is fully compatible with EPI acquisitions using parallel imaging. The applicability of parallel imaging to further accelerate PSF acquisition is shown. The possibility of collecting PSF data sets with total acceleration factors higher than the number of coil elements is demonstrated. Additionally, a new approach to visualize and interpret distortions in the context of various imaging and reconstruction methods based on the PSF is proposed. The reliable performance of the PSF mapping technique is demonstrated on phantom and volunteer scans at field strengths of up to 4 T. Magn Reson Med 52:1156–1166, 2004. © 2004 Wiley‐Liss, Inc.
Human myeloperoxidase: A potential target for molecular MR imaging in atherosclerosis
Authors: Chen John W. , Pham Wellington , Weissleder Ralph , Bogdanov Alexei 
Published: November 2004

AbstractPlaque rupture in atherosclerotic disease is the major cause of morbidity and correlates well with myeloperoxidase (MPO) secretion by activated neutrophils and macrophages in humans. We hypothesized that paramagnetic electron donor compounds that rapidly oxidize and polymerize in the presence of MPO could be designed to enable imaging of local MPO activity levels in arterial segments at risk. Several potential substrates for MPO were synthesized and tested. One lead compound consisting of a covalent conjugate of GdDOTA and serotonin (3‐(2‐aminoethyl)‐5‐hydroxyindole) was efficiently polymerized in the presence of human neutrophil MPO resulting in a 70–100% increase in proton relaxivity. As a result, we were able to demonstrate MPO activity in enzyme solutions and in a model tissue‐like system. These studies suggest that activatable paramagnetic MR imaging agents can be used to directly image MPO activity. Magn Reson Med 52:1021–1028, 2004. © 2004 Wiley‐Liss, Inc.
New modeling and experimental framework to characterize hindered and restricted water diffusion in brain white matter
Authors: Assaf Yaniv , Freidlin Raisa Z. , Rohde Gustavo K. , Basser Peter J. 
Published: November 2004

AbstractTo characterize anisotropic water diffusion in brain white matter, a theoretical framework is proposed that combines hindered and restricted models of water diffusion (CHARMED) and an experimental methodology that embodies features of diffusion tensor andq‐space MRI. This model contains a hindered extra‐axonal compartment, whose diffusion properties are characterized by an effective diffusion tensor, and an intra‐axonal compartment, whose diffusion properties are characterized by a restricted model of diffusion within cylinders. The hindered model primarily explains the Gaussian signal attenuation observed at lowbvalues; the restricted non‐Gaussian model does so at highb. Both high and lowbdata obtained along different directions are required to estimate various microstructural parameters of the composite model, such as the nerve fiber orientation(s), theT2‐weighted extra‐ and intra‐axonal volume fractions, and principal diffusivities. The proposed model provides a description of restricted diffusion in 3D given by a 3D probability distribution (average propagator), which is obtained by 3D Fourier transformation of the estimated signal attenuation profile. The new model is tested using synthetic phantoms and validated on excised spinal cord tissue. This framework shows promise in determining the orientations of two or more fiber compartments more precisely and accurately than with diffusion tensor imaging. Magn Reson Med 52:965–978, 2004. Published 2004 Wiley‐Liss, Inc.
Automatic spatial and temporal temperature control for MR‐guided focused ultrasound using fast 3D MR thermometry and multispiral trajectory of the focal point
Authors: Mougenot Charles , Salomir Rares , Palussière Jean , Grenier Nicolas , Moonen Chrit T.W. 
Published: November 2004

AbstractOf the different modalities to induce local hyperthermia, focused ultrasound is the only noninvasive technology available at the moment. In addition to the 3D localization of the target region, it has been shown that MRI can provide real‐time thermometry and allows online, automatic control of temperature evolution of the focal point. Treatment of a large tissue volume (as compared to the focal spot size, i.e., the ultrasound wavelength) can be achieved rapidly by moving the focal point along an inside‐out spiral trajectory. It has been shown previously that under linear conditions of energy deposition versus temperature, the spatial profile of the temperature within a large area can be controlled. In this study, a proportional, integral, and derivative (PID) spatial‐and‐temporal controller is described for the control of the temperature evolution within the target region under more variable conditions. The aim was to reach a predefined temperature profile after a few successive trajectories. Heat conduction in tissue is exploited to obtain a uniform temperature increase in a volume using discrete sonications without any waiting time. Input data sets consisted of 3D temperature maps provided online by a MR scanner. For each new trajectory, the controller recalculates the number of sonications per surface unit (spatial density of points describing the trajectory) and the applied power. Its performance was tested ex vivo and in vivo. Diameters of the target region ranged from 9 mm to 19 mm. Targeted temperature increase ranged from +8°C to +18°C. Spatiotemporal temperature control showed good stability and fast convergence, for both circular and elliptic ROIs. Magn Reson Med 52:1005–1015, 2004. © 2004 Wiley‐Liss, Inc.
Intravoxel distribution of DWI decay rates reveals C6 glioma invasion in rat brain
Authors: Bennett Kevin M. , Hyde James S. , Rand Scott D. , Bennett Raoqiong , Krouwer Hendrikus G. J. , Rebro Kelly J. , Schmainda Kathleen M. 
Published: November 2004

AbstractThe hypothesis was tested that the intravoxel distribution of water diffusion rates, as measured with a stretched‐exponential model of diffusion‐weighted imaging (DWI), is a marker of brain tumor invasion. Eight rats underwent intracerebral inoculation of C6 glioma cells. In three rats, cells were labeled with a fluorescent dye for microscopy. One rat was inoculated with a saline solution, and five more rats were imaged without inoculation as controls. Five healthy uninoculated rats were also imaged. DWI was performed 14–15 days after inoculation, with diffusion‐weighting factor b = 500 to 6500 sec/mm2, and the resulting signal attenuation was fitted with the stretched‐exponential model. The heterogeneity index values were significantly lower (P < 0.05) in the peritumor ROI than in normal gray matter and significantly higher than in normal white matter. The distributed diffusion coefficient values were significantly lower than in normal white matter or normal gray matter. Fluorescence microscopy confirmed the presence of tumors in the peritumor region that could be histologically distinguished from the main tumor mass. There was no change in proton density or T2‐weighted images in the peritumor region, making vasogenic edema unlikely as a source of contrast. It is therefore thought that the heterogeneity parameter α is a marker of brain tumor invasion. Magn Reson Med 52:994–1004, 2004. © 2004 Wiley‐Liss, Inc.