bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isometric composition operators on the weighted Hardy spaces
Authors: Jaoua Nizar 
Published: September 2010

AbstractWe investigate the composition operators on the weighted Hardy spaces H2(β). For any bounded weight sequence β, we give necessary conditions for those operators to be isometric. The sufficiency of those conditions is well‐known for the classical space H2. In the case where β is non‐decreasing or non‐increasing, their sufficiency holds only for very few weighted spaces. We find out such spaces by characterizing the isometric monomial composition operators, first for a general β, then for any β as before. With no restriction on β, we provide a complete description of all isometric composition operators. We also prove that the unitary monomial ones are the same as those acting on H2. Such a fact extends to general symbols in the case where β is bounded (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On second order weakly hyperbolic equations with oscillating coefficients and regularity loss of the solutions
Authors: Hirosawa Fumihiko 
Published: September 2010

AbstractRegularity of the solution for the wave equation with constant propagation speed is conserved with respect to time, but such a property is not true in general if the propagation speed is variable with respect to time. The main purpose of this paper is to describe the order of regularity loss of the solution due to the variable coefficient by the following four properties of the coefficient: “smoothness”, “oscillations”, “degeneration” and “stabilization”. Actually, we prove the Gevrey and C∞ well‐posedness for the wave equations with degenerate coefficients taking into account the interactions of these four properties. Moreover, we prove optimality of these results by constructing some examples (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Blowup phenomena for a new periodic nonlinearly dispersive wave equation
Authors: Hu Qiaoyi , Yin Zhaoyang 
Published: September 2010

AbstractWe first establish the local well‐posedness for a new periodic nonlinearly dispersive wave equation. We then present a precise blowup scenario and several blowup results of strong solutions to the equation. The obtained blowup results on the equation improve considerably recent results on the Camassa‐Holm equation and the rod equation (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the completeness of the generalized eigenfunctions of elliptic operators on manifolds with conical singularities
Authors: Krainer Thomas 
Published: September 2010

AbstractWe show the completeness of the system of generalized eigenfunctions of closed extensions of elliptic cone operators under suitable conditions on the symbols (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
In vivo observation of intracellular oximetry in perfluorocarbon‐labeled glioma cells and chemotherapeutic response in the CNS using fluorine‐19 MRI
Authors: Kadayakkara Deepak K. K. , Janjic Jelena M. , Pusateri Lisa K. , Young Won‐Bin , Ahrens Eric T. 
Published: September 2010

AbstractPreclinical development of therapeutic agents against cancer could greatly benefit from noninvasive markers of tumor killing. Potentially, the intracellular partial pressure of oxygen (pO2) can be used as an early marker of antitumor efficacy. Here, the feasibility of measuring intracellular pO2 of central nervous system glioma cells in vivo using 19F magnetic resonance techniques is examined. Rat 9L glioma cells were labeled with perfluoro‐15‐crown‐5‐ether ex vivo and then implanted into the rat striatum. 19F MRI was used to visualize tumor location in vivo. The mean 19F T1 of the implanted cells was measured using localized, single‐voxel spectroscopy. The intracellular pO2 in tumor cells was determined from an in vitro calibration curve. The basal pO2 of 9L cells (day 3) was determined to be 45.3 ± 5 mmHg (n = 6). Rats were then treated with a 1× LD10 dose of bischloroethylnitrosourea intravenously and changes in intracellular pO2 were monitored. The pO2 increased significantly (P = 0.042, paired T‐test) to 141.8 ± 3 mmHg within 18 h after bischloroethylnitrosourea treatment (day 4) and remained elevated (165 ± 24 mmHg) for at least 72 h (day 6). Intracellular localization of the perfluoro‐15‐crown‐5‐ether emulsion in 9L cells before and after bischloroethylnitrosourea treatment was confirmed by histological examination and fluorescence microscopy. Overall, noninvasive 19F magnetic resonance techniques may provide a valuable preclinical tool for monitoring therapeutic response against central nervous system or other deep‐seated tumors. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Brain MR perfusion‐weighted imaging with alternate ascending/descending directional navigation
Authors: Park Sung‐Hong , Duong Timothy Q. 
Published: September 2010

AbstractIn this study, a new arterial spin labeling technique that requires no separate spin preparation pulse was developed. Sequential two‐dimensional slices were acquired in ascending and descending orders by turns using balanced steady state free precession for pair‐wise subtraction. Simulation studies showed this new technique, alternate ascending/descending directional navigation (ALADDIN), has high sensitivity to both slow‐ (1–10 cm/sec) and fast‐moving (>10 cm/sec) blood because of the presence of multiple labeling planes proximal to imaging planes and sensitivity of balanced steady state free precession to initial magnetization differences. ALADDIN provided high‐resolution multislice perfusion‐weighted images in ∼3 min. About 80–90% of signals in a slice were ascribed to spins saturated in the four prior slices. Three to five edge slices on each side of imaging group were affected by transient magnetization transfer effects and incomplete T1 recovery between successive acquisitions. ALADDIN signals were dependent on many imaging parameters, implying room for improvement. Sagittal and coronal ALADDIN images demonstrated perfusion direction in gray matter regions was mostly from center to lateral, anterior, or posterior, whereas that in some white matter regions was reversed. ALADDIN is likely useful for many studies requiring perfusion‐weighted imaging with short scan time, insensitiveness to arterial transit time, directional information, high resolution, and/or wide coverage. Magn Reson Med, 2011. © 2010 Wiley‐Liss, Inc.
Longitudinal MR assessment of hypoxic ischemic injury in the immature rat brain
Authors: van de Looij Yohan , Chatagner Alexandra , Hüppi Petra S. , Gruetter Rolf , Sizonenko Stéphane V. 
Published: September 2010

AbstractExtremely preterm infants commonly show brain injury with long‐term structural and functional consequences. Three‐day‐old (P3) rat pups share some similarities in terms of cerebral development with the very preterm infant (born at 24–28 weeks of gestation). The aim of this study was to assess longitudinally the cerebral structural and metabolic changes resulting from a moderate neonatal hypoxic ischemic injury in the P3 rat pup using high‐field (9.4 T) MRI and localized 1H magnetic resonance spectroscopy techniques. The rats were scanned longitudinally at P3, P4, P11, and P25. Volumetric measurements showed that the percentage of cortical loss in the long term correlated with size of damage 6 h after hypoxia–ischemia, male pups being more affected than female. The neurochemical profiles revealed an acute decrease of most of metabolite concentrations and an increase in lactate 24 h after hypoxia–ischemia, followed by a recovery phase leading to minor metabolic changes at P25 in spite of an abnormal brain development. Further, the increase of lactate concentration at P4 correlated with the cortical loss at P25, giving insight into the early prediction of long‐term cerebral alterations following a moderate hypoxia–ischemia insult that could be of interest in clinical practice. Magn Reson Med, 2011. © 2010 Wiley‐Liss, Inc.
An analytical description of balanced steady‐state free precession with finite radio‐frequency excitation
Authors: Bieri Oliver 
Published: September 2010

AbstractConceptually, the only flaw in the standard steady‐state free precession theory is the assumption of quasi‐instantaneous radio‐frequency pulses, and 10–20% signal deviations from theory are observed for common balanced steady‐state free precession protocols. This discrepancy in the steady‐state signal can be resolved by a simple T2 substitution taking into account reduced transverse relaxation effects during finite radio‐frequency excitation. However, finite radio‐frequency effects may also affect the transient phase of balanced steady‐state free precession, its contrast or its spin‐echo nature and thereby have an adverse effect on common steady‐state free precession magnetization preparation methods. As a result, an in‐depth understanding of finite radio‐frequency effects is not only of fundamental theoretical interest but also has direct practical implications. In this article, an analytical solution for balanced steady‐state free precession with finite radio‐frequency pulses is derived for the transient phase (under ideal conditions) and in the steady state demonstrating that balanced steady‐state free precession key features are preserved but revealing an unexpected dependency of finite radio‐frequency effects on relaxation times for the transient decay. Finally, the mathematical framework reveals that finite radio‐frequency theory can be understood as a generalization of alternating repetition time and fluctuating equilibrium steady‐state free precession sequence schemes. Magn Reson Med, 2011. © 2010 Wiley‐Liss, Inc.
Quantitative dynamic nuclear polarization‐NMR on blood plasma for assays of drug metabolism
Authors: Lerche Mathilde H. , Meier Sebastian , Jensen Pernille R. , Hustvedt Svein‐Olaf , Karlsson Magnus , Duus Jens Ø. , Ardenkjær‐Larsen Jan H. 
Published: September 2010

AbstractAnalytical platforms for the fast detection, identification and quantification of circulating drugs with a narrow therapeutic range are vital in clinical pharmacology. As a result of low drug concentrations, analytical tools need to provide high sensitivity and specificity. Dynamic nuclear polarization‐NMR (DNP‐NMR) in the form of the hyperpolarization–dissolution method should afford the sensitivity and spectral resolution for the direct detection and quantification of numerous isotopically labeled circulating drugs and their metabolites in single liquid‐state NMR transients. This study explores the capability of quantitativein vitroDNP‐NMR to assay drug metabolites in blood plasma. The lower limit of detection for the anti‐epileptic drug13C‐carbamazepine and its pharmacologically active metabolite13C‐carbamazepine‐10,11‐epoxide is 0.08 µg/mL in rabbit blood plasma analyzed by single‐scan13C DNP‐NMR. An internal standard is used for the accurate quantification of drug and metabolite. Comparison of quantitative DNP‐NMR data with an established analytical method (liquid chromatography‐mass spectrometry) yields a Pearson correlation coefficientrof 0.99. Notably, all DNP‐NMR determinations were performed without analyte derivatization or sample purification other than plasma protein precipitation. Quantitative DNP‐NMR is an emerging methodology which requires little sample preparation and yields quantitative data with high sensitivity for therapeutic drug monitoring. Copyright © 2010 John Wiley & Sons, Ltd.
Blood flow quantification of the human retina with MRI
Authors: Maleki Nasim , Dai Weiying , Alsop David C. 
Published: September 2010

AbstractThe purpose of this study was to investigate the feasibility of measuring blood flow to the retina using arterial spin labeling MRI, a quantitative, noninvasive tomographic technique. Blood flow imaging was performed in a single axial slice through both eyes of five healthy volunteers with no history of retinal diseases. The imaging was optimized to minimize the errors from motion and nonuniform magnetic fields caused by proximity to the sinuses. Key hemodynamic factors for flow quantification, including arterial transit delay and the apparent decay time of the signal, were estimated by repeated measurements with different arterial spin labeling timing. A clearly elevated signal, consistent with the anatomical location of the retina, was observed in all subjects. The measured blood flow to a 1 cm × 1.47 cm section of the retina, centered on the fovea, was 1.75 ± 0.54 µL/mm2/min (total blood flow of 261 ± 87 µL/min). The arterial transit delay from a labeling plane 5 cm below the slice was 1137 ± 288 ms. These results establish the feasibility of measuring blood flow to the retina with MRI, and support the future characterization of the healthy and diseased ocular circulation with this method. Copyright © 2010 John Wiley & Sons, Ltd.
Clinical characteristics and biomarkers of breast cancer associated with choline concentration measured by 1H MRS
Authors: Chen J.‐H. , Mehta R.S. , Baek H.‐M. , Nie K. , Liu H. , Lin M.Q. , Yu H.J. , Nalcioglu O. , Su M.‐Y. 
Published: September 2010

AbstractThis study investigated the association between the total choline (tCho) concentration and the clinical characteristics and biomarker status of breast cancer. Sixty‐two patients with breast cancer, 1.5 cm or larger in size on MR images, were studied. The tCho concentration was correlated with the MRI features, contrast enhancement kinetics, clinical variables and biomarkers. Pairwise two‐tailed Spearman's nonparametric test was used for statistical analysis. The tCho concentration was higher in high‐grade than moderate‐/low‐grade tumors (p = 0.04) and in tumors with higher Ktrans and kep (p < 0.001 for both). The association of tCho concentration with age (p = 0.05) and triple negative biomarker (p = 0.09) approached significance. tCho was not detected in 17 patients, including 15 with invasive ductal cancer and two with infiltrating lobular cancer. Fifteen of the 17 patients had moderate‐ to low‐grade cancers, and 11 had human epidermal growth factor‐2‐negative cancer, suggesting that these two factors might lead to false‐negative choline. Higher tCho concentration in high‐grade tumors and tumors with higher Ktrans and kep indicates that choline is associated with cell proliferation and tumor angiogenesis. The higher choline level in younger women may be caused by their more aggressive tumor type. The results presented here may aid in the better interpretation of 1H MRS for the diagnosis of breast lesions. Copyright © 2010 John Wiley & Sons, Ltd.
Fast, reproducible measurement of the vascular input function in mice using constrained reconstruction and cardiac sampling
Authors: Ragan Dustin K. , Lai Stephen Y. , Bankson James A. 
Published: September 2010

AbstractDynamic contrast‐enhanced MRI is often used to assess the response to therapy in small animal models of cancer. Rigorous quantification of dynamic contrast‐enhanced MRI data using common pharmacokinetic models requires dynamic determination of the concentration of contrast in tumor tissue and in blood. Measurement of the blood concentration, or vascular input function (VIF), requires high temporal resolution and is prone to distortion as a result of flow and partial volume artifacts when measured in local blood vessels. We have developed a strategy for the robust measurement of VIF in mice that uses a constrained reconstruction algorithm to enable sampling from the left ventricle of the heart. The feasibility of the algorithm and its resistance to cardiac motion are demonstrated in vivo and through numerical simulations. VIF sampling is interleaved with slices dedicated to tumor coverage to yield a fast VIF sampling period (81 ms) that is decoupled from the temporal resolution of tumor data (3.9 s). The algorithm provides results that agree with fully encoded measurements in the slowly varying component of VIF to within a 4% root‐mean‐square signal difference. Analysis of a parametric representation of VIFs measured in a population of mice showed a significant reduction in variations observed within subjects (5%–58% over four parameters; p < 0.05) and a reduction in variations between subjects (19%–62%) when using this technique. Preliminary dynamic measurements in an orthotopic xenograft model of anaplastic thyroid cancer revealed a decrease in the variation of pharmacokinetic parameters between mice by a factor of two. Copyright © 2010 John Wiley & Sons, Ltd.
Surface modification of spruce wood flour and effects on the dynamic fragility of PLA/wood composites
Authors: Gregorova Adriana , Hrabalova Marta , Kovalcik Rene , Wimmer Rupert 
Published: September 2010

AbstractPoly (lactic acid) (PLA), a biodegradable aliphatic semicrystalline polyester was filled with 40 wt% spruce wood flour (WF), to produce composite materials. Hydrothermal treatment, as well as maleic anhydride, vinyltrimethoxysilane, and stearic acid surface treatments were applied. The influence of surface modifications for WF was tested in terms of thermal, mechanical, and viscoelastic properties. The recorded results show that in both, the untreated and treated PLA/WF composites, the rigid amorphous phase content has been enhanced. The presence of WF causes a stiffness increase of the PLA/WF composites, while damping factor was decreased. The effect of wood surface modifications on interfacial compatibility with PLA was estimated by dynamic fragility parameter m calculated according the Williams‐Landel‐Ferry equation. The incorporation of untreated WF increased dynamic fragility of PLA/WF composites markedly, whereas used silane, maleic anhydride and hydrothermal treatments lead to lower values of parameter m. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers
Producing continuous twisted yarn from well‐aligned nanofibers by water vortex
Authors: Yousefzadeh Maryam , Latifi Masoud , Teo Wee‐Eong , Amani‐Tehran Mohammad , Ramakrishna Seeram 
Published: September 2010

AbstractA new technology based on the liquid support system is introduced for fabricating continuous twisted nanofibrous yarn. In this novel technique, the electrospun yarn was collected from the top of the water vortex such that it can be twisted simultaneously during yarn production. Our study demonstrated the feasibility of the technique for producing continuous twisted yarn from well aligned nanofibers. It is shown that the system can be modified to have different yarn counts with various twists. Further, significant improvement can be seen in the strength and strain when nanofibrous yarn is twisted compared to non‐twisted yarn. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers
A Device for Testing Thermal Impact Sensitivity of High Explosives
Authors: Zhang Gengxin , Weeks Brandon L. 
Published: September 2010

AbstractA drop‐weight instrument is described to investigate the impact sensitivity of high explosives at elevated temperatures. This test is typically performed to discover potential safety aspects of either newly synthesized materials of unknown behavior. Normally, drop‐weight impact sensitivity tests are conducted at room temperature, since high explosives are often stored or handled at room temperature. The instrument described here has the capability of heating the samples from ambient to 300 °C prior to impact. The thermal impact sensitivities of PETN, TATP, HMX, and silver azide (AgN3) as a function of temperature are obtained. The phase transition of HMX can clearly be observed by a significant decrease in the impact height in situ.
Automated minimization of steric clashes in protein structures
Authors: Ramachandran Srinivas , Kota Pradeep , Ding Feng , Dokholyan Nikolay V. 
Published: September 2010

AbstractMolecular modeling of proteins including homology modeling, structure determination, and knowledge‐based protein design requires tools to evaluate and refine three‐dimensional protein structures. Steric clash is one of the artifacts prevalent in low‐resolution structures and homology models. Steric clashes arise due to the unnatural overlap of any two nonbonding atoms in a protein structure. Usually, removal of severe steric clashes in some structures is challenging since many existing refinement programs do not accept structures with severe steric clashes. Here, we present a quantitative approach of identifying steric clashes in proteins by defining clashes based on the Van der Waals repulsion energy of the clashing atoms. We also define a metric for quantitative estimation of the severity of clashes in proteins by performing statistical analysis of clashes in high‐resolution protein structures. We describe a rapid, automated, and robust protocol, Chiron, which efficiently resolves severe clashes in low‐resolution structures and homology models with minimal perturbation in the protein backbone. Benchmark studies highlight the efficiency and robustness of Chiron compared with other widely used methods. We provide Chiron as an automated web server to evaluate and resolve clashes in protein structures that can be further used for more accurate protein design. Proteins 2010. © 2010 Wiley‐Liss, Inc.
Exploring coumarin egress channels in human cytochrome p450 2a6 by random acceleration and steered molecular dynamics simulations
Authors: Li Weihua , Shen Jie , Liu Guixia , Tang Yun , Hoshino Tyuji 
Published: September 2010

AbstractThe kinetic analysis of coumarin oxidation by CYP2A6 suggested that substrate binding and release occurred in the multiple steps and such events proceeded rapidly. However, the crystal structure of the CYP2A6‐coumarin complex reveals that no obvious channel is open enough to allow coumarin to pass through. Thus, an intriguing and important question arises: how coumarin enters and exits the active site, which is deeply buried at the center of CYP2A6 fold. In this study, geometric analysis of the potential openings was first performed on all the available crystal structures of CYP2A6. And then, random acceleration molecular dynamics simulations were used to explore the possible substrate egress channels in CYP2A6. Two channels were most frequently observed. Afterwards, steered molecular dynamics simulations were performed and potentials of mean force were constructed to compare the preference of the two channels serving as the substrate egress channel. The results showed that channel 2c, which is located between helices I and G and the helix B'‐C region, was the most likely channel for coumarin egress. The opening of channel 2c was characterized by a rotation of Phe111 together with a bending of helix B'. Our findings will not only be helpful for understanding the unbinding mechanism of coumarin and for identifying structural determinants related to the biological function of CYP2A6, but also provide further insight into the channel selectivity of P450s. Proteins 2010. © 2010 Wiley‐Liss, Inc.
Theoretical study of NMR chemical shift induced by H/D isotope effect
Authors: Sugimori Kimikazu , Kawabe Hiroyuki 
Published: September 2010

AbstractThe isotope effect induced by deuterium substituted species is observed in molecular properties, such as geometry, kinetics, and electronic state, of the molecules through nuclear‐electron interaction. Theoretical considerations and experimental alignments have been studied by ab initio molecular orbital, density functional theory, and other empirical strategies. The Born‐Oppenheimer approximation with nuclear vibrational wavefunction can treat isotope effect because nuclear mass effect account for the average distance of vibrational motion. In this study, we introduce Morse anharmonic oscillator model to calculate average internuclear distance of diatomic molecules having X‐H bonding and X‐D bonding. Morse parameters are determined by fitting to potential energy surface of molecular orbital and/or density functional calculations, and then the average distance are obtained as the expectation value of the analytical Morse vibrational wavefunction. Nuclear magnetic resonance shielding constants of the H/D isotopomer are calculated again on the average distance by using GIAO with B3LYP and CCSD calculation. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010