bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reduced blood flow artifact in intraplaque hemorrhage imaging using CineMPRAGE
Authors: Mendes Jason , Parker Dennis L. , Kim Seong‐Eun , Treiman Gerald S. 
Published: July 2012

AbstractMagnetization prepared rapid acquisition gradient echo (3D MPRAGE) has been shown to be a sensitive method to image carotid intraplaque hemorrhage. As the MPRAGE sequence used to identify potential intraplaque hemorrhage does not utilize cardiac gating, it is difficult to optimize the inversion times due to the dynamic nature of flowing blood. As a result, a best fit inversion time is often determined experimentally and then used for in vivo clinical examination. This results in compromised blood suppression and occasional hemorrhage mimicking flow artifacts. We demonstrate that a retrospective cardiac correlated reconstruction can be applied to the conventional MPRAGE sequence (CineMPRAGE) to more accurately identify blood signal. This CineMPRAGE reconstruction uses the data from a standard nongated MPRAGE sequence to generate a full sequence of cardiac correlated images throughout the cardiac cycle and, therefore, provides a dynamic view of the carotid artery and a better ability to discern blood signal from potential intraplaque hemorrhage. In our preliminary study of 35 patients, signal from potential hemorrhage was constant over the cardiac cycle, whereas any signal from blood flow artifact was observed as an oscillating signal over the cardiac cycle. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.
Multidirectional high‐moment encoding in phase contrast MRI
Authors: Zwart Nicholas R. , Pipe James G. 
Published: July 2012

AbstractThe use of phase contrast MRI to measure vascular flow provides a unique method for acquiring quantitative estimates of flow as well as morphological imaging. The quantitative aspects of phase contrast magnetic resonance angiography (PC‐MRA) provide unique relationships between measurement parameters and resulting signal to noise ratio of the velocity measurements. This article introduces a new method to exploit these relationships providing increased efficiency, and therefore, higher vessel conspicuity. Signal to noise ratio gains in high‐moment PC‐MRA are limited by the ability to unalias phase measurements that fall outside the −π to π interval. Unaliasing phase on a per pixel basis is limited by errors in the measurements due to noise and intravoxel flow distributions. Current dual‐VENC methods have been shown to be robust to these errors and provide high velocity to noise ratio gains, however, the collection of a required high‐VENC set can be inefficient. The presented method provides more time efficient gains in velocity to noise ratio compared to a dual‐VENC approach by eliminating the high‐VENC acquisitions and using shared information between nonorthogonal measurements. Simulations, phantom, and in vivo angiography are used to characterize the noise performance of each method. The velocity to noise ratio efficiency of the proposed method is shown to be ∼1.7 times greater than the dual‐VENC method at the same gradient moment. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.
The synthesis of covalent bonded single‐walled carbon nanotube/polyvinylimidazole composites by in situ polymerization and their physical characterization
Authors: Tekin Nalan , Beyaz Saadet Kayiran , Kara Ali , Şimşek Eyüp , Lamari Farida Darkrim , Çakmak Gülbeden , Güney Hasan Yüksel 
Published: July 2012

AbstractSingle‐walled carbon nanotube (SWCNT) polyvinylimidazole (PVI) composites have been prepared by in situ emulsion polymerization. Dispersion of raw SWCNTs in the PVI matrix was improved by surface modification of the SWCNTs using nitric acid treatment and air oxidation. The carbonyl‐terminated SWCNTs were covalently bonded to PVI by in situ polymerization and the SWCNT/PVI composite was thus obtained. The morphological and structural characterizations of the surface‐functionalized SWCNTs and SWCNT/PVI composites were carried out by Fourier transform infrared spectroscopy, X‐ray diffraction, conductivity measurements, scanning, and transmission electron microscopy. Thermograms of the materials were determined by the differential scanning calorimetry technique. The characterization results indicate that PVI was covalently bonded to SWCNTs and a new material was then obtained. The functionalized SWCNTs showed homogenous dispersion in the composites, whereas purified SWCNT resulted in poor dispersion and nanotube agglomeration. SWCNT/PVI composites exhibited chemical stability enhancement in many common solvents. I–V curves of the samples exhibit an ohmic character. Conductivity values for pure SWCNTs, pure PVI and SWCNT/PVI composite were measured to be 3.47, 2.11 × 10−9, and 2.3 × 10−3 S/m, respectively. Because of resonance, a large dielectric constant is obtained for SWCNT/PVI composite, which is not observed for ordinary materials. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers
Film formation from PS/AL2O3 nanocomposites prepared by dip‐drawing method
Authors: Uğur Şaziye , Kışlak Yusuf 
Published: July 2012

AbstractIn this study, steady state fluorescence (SSF) and UV–vis (UVV) techniques were used to examine film formation from pyrene (P) labeled polystyrene (PS) latex/Al2O3 (PS/Al2O3) composites prepared by the dip‐drawing method. The effects of dip‐drawing rates and dipping time in Al2O3 sol on film formation behavior and the morphology of PS/Al2O3 films were investigated. Films were prepared first by casting PS dispersion on clean glass substrates which creates a close‐packed array of PS sphere (203 nm) templates. These templates were then covered with Al2O3 utilizing the dip‐drawing method for various dip‐drawing rates and dipping times in Al2O3 sol. The film formation of these composites was studied by annealing them at a temperature range of 100°C to 270°C and monitoring the scattered light (Isc), fluorescence (IP), and transmitted light (Itr) intensities after each annealing step. The structural properties of the composite films were analyzed with a scanning electron microscope (SEM). The results demonstrated that the film formation behavior and morphology of composites depended mainly on dipping time, and no dependence on the dip‐drawing rate was observed. The optical results indicated that PS/Al2O3 films undergo complete film formation independent of the dip‐drawing rate and dipping time. Additionally, the film formation stages were modeled and the corresponding activation energies were determined. After completion of film formation, PS polymers were extracted to obtain porous Al2O3 thin films. Highly ordered porous structures were observed for long dipping time in Al2O3 sol but no change was observed for different dip‐drawing rates, confirming the optical data. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers
Electrical conductivity of polyurethane/MWCNT nanocomposite foams
Authors: Athanasopoulos N. , Baltopoulos A. , Matzakou M. , Vavouliotis A. , Kostopoulos V. 
Published: July 2012

AbstractPolymeric foams with electrical conductivity represent a novel and very interesting class of materials rather sporadically studied. In this study, the feasibility to prepare electrically conductive Rigid Polyurethane (PUR) foams at various densities using multiwall carbon nanotubes (MWCNT) at varying contents was investigated. The produced PUR/MWCNT foams exhibited electrical conductivity over a wide range of densities and nanofiller contents. The effect of these two parameters on the electrical conductivity of the final foam system was studied. To explain the behavior, Statistical Percolation laws were employed. Model parameters were elaborated for both cases showing that the percolation model can adequately describe the behavior. The foaming process is analyzed in further detail to assist in the explanation and understanding of theexperimental observations. Finally, a material design map is proposed for the preparation of electrically conductive foams. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers
Analysis of synergistic effect of nanozinc/nanoclay additives on the corrosion performance of zinc‐rich polyurethane nanocomposite coatings
Authors: Arianpouya N. , Shishesaz M. , Ashrafi A. 
Published: July 2012

AbstractThe aim of this study was to analyze the synergistic effect of clay and zinc nanopigments. Therefore different percentages of Montmorillonite clay nanolayers were added to zinc‐rich polyurethane nanocomposites. Ultrasonication process was used to prepare polyurethane/nanozinc/nanoclay nanocomposites. Then coatings were applied on steel panels with composition of 10 wt% nanozinc and 0.5, 1, 1.5, and 2 wt% nanoclay. TEM and XRD were used to analyze the structural characteristics of the nanocomposites. The results of the structure analysis revealed the size of nanomaterials and confirmed the appropriate dispersion in polymer matrix. The anticorrosive properties of the nanocomposites were investigated using salt fog test and electrochemical impedance spectroscopy (EIS). The results of EIS showed that addition of clay nanolayers improves the corrosion resistance of coatings and the best corrosion performance obtained for the nanocomposite sample with 2 wt% nanoclay. Also, according to the results of the salt spray test, the sample with 2 wt% nanoclay showed the least H2O penetration and exfoliation adjacent to the scratches. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers
Relative stabilities of IgG1 and IgG4 Fab domains: Influence of the light–heavy interchain disulfide bond architecture
Authors: Heads James T. , Adams Ralph , D'Hooghe Lena E. , Page Matt J. T. , Humphreys David P. , Popplewell Andrew G. , Lawson Alastair D. , Henry Alistair J. 
Published: July 2012

AbstractThe stability of therapeutic antibodies is a prime pharmaceutical concern. In this work we examined thermal stability differences between human IgG1 and IgG4 Fab domains containing the same variable regions using the thermofluor assay. It was found that the IgG1 Fab domain is up to 11°C more stable than the IgG4 Fab domain containing the same variable region. We investigated the cause of this difference with the aim of developing a molecule with the enhanced stability of the IgG1 Fab and the biological properties of an IgG4 Fc. We found that replacing the seven residues, which differ between IgG1 CH1 and IgG4 CH1 domains, while retaining the native IgG1 light‐heavy interchain disulfide (L–H) bond, did not affect thermal stability. Introducing the IgG1 type L–H interchain disulfide bond (DSB) into the IgG4 Fab resulted in an increase in thermal stability to levels observed in the IgG1 Fab with the same variable region. Conversely, replacement of the IgG1 L–H interchain DSB with the IgG4 type L–H interchain DSB reduced the thermal stability. We utilized the increased stability of the IgG1 Fab and designed a hybrid antibody with an IgG1 CH1 linked to an IgG4 Fc via an IgG1 hinge. This construct has the expected biophysical properties of both the IgG4 Fc and IgG1 Fab domains and may therefore be a pharmaceutically relevant format.
The crystal structure of the periplasmic domain of Vibrio parahaemolyticus CpxA
Authors: Kwon Eunju , Kim Dong Young , Ngo Tri Duc , Gross Carol A. , Gross John D. , Kim Kyeong Kyu 
Published: July 2012

AbstractThe Cpx two‐component system of Gram‐negative bacteria senses extracytoplasmic stresses using the histidine kinase CpxA, a membrane‐bound sensor, and controls the transcription of the genes involved in stress response by the cytosolic response regulator CpxR, which is activated by the phosphorelay from CpxA. CpxP, a CpxA‐associated protein, also plays an important role in the regulation of the Cpx system by inhibiting the autophosphorylation of CpxA. Although the stress signals and physiological roles of the Cpx system have been extensively studied, the lack of structural information has limited the understanding of the detailed mechanism of ligand binding and regulation of CpxA. In this study, we solved the crystal structure of the periplasmic domain of Vibrio parahaemolyticus CpxA (VpCpxA‐peri) to a resolution of 2.1 Å and investigated its interaction with CpxP. VpCpxA‐peri has a globular Per‐ARNT‐SIM (PAS) domain and a protruded C‐terminal tail, which may be required for ligand sensing and CpxP binding, respectively. The direct interaction of the PAS core of VpCpxA‐peri with VpCpxP was not detected by NMR, suggesting that the C‐terminal tail or other factors, such as the membrane environment, are necessary for the binding of CpxA to CpxP.
Cloning, characterisation and expression profiling of the cDNA encoding the ryanodine receptor in diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae)
Authors: Guo Lei , Tang Baozhen , Dong Wei , Liang Pei , Gao Xiwu 
Published: July 2012

AbstractBACKGROUND: The rynodine receptors (RyRs) are the main targets of diamide insecticides such as chlorantraniliprole. To provide the basis for a good understanding of the molecular mechanisms of diamide insecticide resistance, an RyR gene from Plutella xylostella was cloned and characterised in the present paper.RESULTS: A full‐length cDNA sequence of RyR was cloned from P. xylostella through RT‐PCR and rapid amplification of cDNA ends (RACE). The gene (named PxRyR1) is 15 753 bp long, with an open reading frame of 15 354 bp, encoding a predicted RyR of 5117 amino acids. An alternative splicing of the PxRyR1 was also cloned and named PxRyR2. The PxRyR1 shares 77–93% identity with other insect RyRs. Quantitative real‐time PCR analysis showed that the PxRyR was expressed at a high level in second‐instar larvae and adults, at a low level in prepupae and pupae and abundantly in the body wall muscle and head (respectively 6.00 and 3.12 times the expression in the gut). Western blot analysis with anti‐RyR antibodies showed that the RyR was mainly present in the body wall muscle and head, but barely present in the haemocyte and gut.CONCLUSIONS: There are at least two alternative splices of PxRyR expressed in all developmental stages and tissues in P. xylostella at various levels. The results provided the basis for further understanding of the mechanisms of resistance to diamide insecticides in P. xylostella. Copyright © 2012 Society of Chemical Industry
High gravity‐wave activity observed in Patagonia, Southern America: generation by a cyclone passage over the Andes mountain range
Authors: Pulido M. , Rodas C. , Dechat D. , Lucini M. M. 
Published: July 2012

AbstractThe Antarctic peninsula and Patagonia region (the south of South America) have recently been identified as the regions with the highest gravity‐wave activity in the world. In this work, the generation and propagation of gravity waves in the Patagonia region in an event of strong wave activity from 30 October 1995–1 November 1995 is examined by means of radiosonde measurements and simulations with the Weather Research and Forecasting (WRF) model. The waves are generated by strong surface winds found near the Andes mountains at a latitude of 49–51°S. The strong low‐level winds are related to an extratropical cyclone that propagates southeastward in the South Pacific ocean and approaches the western coast of the continent. The waves propagate southeast toward Tierra del Fuego and they continue their propagation over the Drake Passage. They are found to propagate long meridional (lateral) distances due to the shear background conditions. This fact is corroborated with WRF simulations and a novel technique that combines wavelet analysis and backward ray‐tracing. Therefore, this work provides further evidence that high gravity‐wave activity found by several studies over Drake Passage may have an orographic origin. During the orographic wave event, which lasts about 72 hours, the horizontal wavelength is unexpectedly found to change day‐to‐day. The analysis shows that changes in the near‐surface meteorological conditions produced by the cyclone passage may trigger different components of the forcing orography. The orographic waves propagate toward their critical levels, which are found at 25 km and above. The radiosonde measurements show that the wave is breaking continuously along a wide altitude range; this finding from measurements supports the picture of continuous wave erosion along the ray path instead of abrupt wave‐breaking for the examined wave event. Copyright © 2012 Royal Meteorological Society
Flow during the evening transition over steep Alpine slopes
Authors: Nadeau Daniel F. , Pardyjak Eric R. , Higgins Chad W. , Huwald Hendrik , Parlange Marc B. 
Published: July 2012

AbstractA field campaign, the Slope Experiment near La Fouly (SELF‐2010), was conducted to monitor the evening transition of slope flows on clear‐sky days from July to September 2010 in a narrow valley of the Swiss Alps. A steep west‐facing slope with inclinations ranging from 25° to 45° was instrumented from 1900 m to 2200 m above sea‐level. Detailed measurements were made along a linear transect of the slope with two turbulence towers, two weather stations, five surface temperature measurement stations and a tethered balloon system. The present study focuses on nine exemplary ‘convective’ days, characterized by weak synoptic flow and clear‐sky conditions, during which thermal circulations prevail. The analysis of the observational data shows that topographic shading triggers the evening transition. The topographic configuration around the experimental site results in a sharply defined ‘shading front’ propagating upslope, causing a sudden decrease in incoming short‐wave radiation on the order of several hundreds of W m−2 within a few minutes. The slope surface rapidly responds to the advancing shading front; in some cases, reductions in surface temperatures of some 10°C in less than 10 min are observed. This is rapidly followed by an early‐evening calm period with very small turbulent kinetic energy (TKE< 0.05 m 2 s−2) and extremely light wind speeds (< 0.5 m s−1). When the inertia‐driven upslope flow is fully stopped by the katabatic acceleration, a shallow local drainage flow forms and reaches a quasi‐equilibrium 1.5 h after the local sunset. An analysis of the TKE budget close to the surface shows that the buoyancy flux is much greater than the shear production in the last hours before the local sunset, possibly due to valley curvature effects. Copyright © 2012 Royal Meteorological Society
Variation of compound‐specific hydrogen isotope ratios under changing temperature program in gas chromatography/thermal conversion/isotope ratio mass spectrometry
Authors: Liu Weiguo , Wang Zheng , Cui Linlin , Sauer Peter E. , Cao Yunning 
Published: July 2012

RATIONALEIn recent experiments, we found that compound‐specific δ2H values can vary as a result of changing the gas chromatography temperature program under common pyrolysis conditions. To achieve better precision, it is necessary to examine the details and find a solution to this problem when using gas chromatography/thermal conversion/isotope ratio mass spectrometry (GC‐TC‐IRMS) for hydrogen isotope analysis.METHODSA test was designed to find the possible temperature effect under four different GC temperature ramp rates using n‐alkanes (n‐C21, n‐C27, and n‐C31) and fatty acids (n‐C12, n‐C18, and n‐C24). The common 'hexane' method was used initially to condition the pyrolysis reactor. Experiments were then carried out using the 'methane condition' method because it was considered to improve pyrolysis efficiency.RESULTSUnder the 'hexane condition' the measured hydrogen isotope ratios of the n‐alkanes and n‐fatty acids became more positive with increasing GC temperature ramp rate. The ion current intensity of hydrogen also generally increased. However, when the 'methane condition' method was used, the measured δ2H values of the n‐alkanes and n‐fatty acids showed little change under different GC temperature ramp rates.CONCLUSIONSHigher pyrolysis efficiency could reduce the tailing of the H2 peak and the related isotopic variations at increased GC temperature ramp rates. In addition, too slow a temperature ramp rate could broaden the peak width and thus increase the background effect and possible isotopic fractionations in the split interface; this could also influence the hydrogen isotope values. We therefore suggest that the appropriate temperature ramp rate is an important factor in improving the precision in analyzing compound‐specific hydrogen isotopes. Copyright © 2012 John Wiley & Sons, Ltd.
Elimination of nitrogen interference during online oxygen isotope analysis of nitrogen‐doped organics using the “NiCat” nickel reduction system
Authors: Hagopian William M. , Jahren A. Hope 
Published: July 2012

RATIONALEAccurate online analysis of the δ18O values of nitrogen‐bearing organic compounds is of interest to several emergent fields, including ecology, forensics and paleontology. During online analysis, high‐temperature conversion (HTC) of nitrogen‐bearing organics produces N2 gas which creates isobaric interference with the isotopic measurement. Specifically, N2 reacts with trace amounts of oxygen in the mass spectrometer source to form 14N16O (m/z 30), which prevents accurate evaluation of the sample 12C18O peak (m/z 30).METHODSWe present an alternative system to the conventional HTC, which uses a nickel‐catalyzed (“NiCat”) reduction furnace to convert HTC‐produced CO into CO2, allowing for δ18O measurement using signal intensities at m/z 44 and 46.RESULTSThis system yields identical δ18O values for nitrogen‐doped and undoped sucrose and cellulose compounds up to molar yield ratios of N2:CO = 0.22. In contrast, our conventional HTC system configured to factory recommendations with the stock gas chromatography (GC) column produced a discrepancy of ~5‰ between nitrogen‐doped and undoped samples.CONCLUSIONSBecause of its ability to eliminate isobaric interference, the NiCat system is a viable alternative to conventional HTC for δ18O measurement, and can be constructed from relatively inexpensive and readily available materials. As an additional advantage, the CO2 analyte produced by NiCat may be cryofocused, to allow for oxygen‐isotope determinations on very small amounts of sample substrate. Copyright © 2012 John Wiley & Sons, Ltd.
RESTORING SALMON HABITAT FOR A CHANGING CLIMATE
Authors: Beechie T. , Imaki H. , Greene J. , Wade A. , Wu H. , Pess G. , Roni P. , Kimball J. , Stanford J. , Kiffney P. , Mantua N. 
Published: July 2012

ABSTRACTAn important question for salmon restoration efforts in the western USA is ‘How should habitat restoration plans be altered to accommodate climate change effects on stream flow and temperature?’ We developed a decision support process for adapting salmon recovery plans that incorporates (1) local habitat factors limiting salmon recovery, (2) scenarios of climate change effects on stream flow and temperature, (3) the ability of restoration actions to ameliorate climate change effects, and (4) the ability of restoration actions to increase habitat diversity and salmon population resilience. To facilitate the use of this decision support framework, we mapped scenarios of future stream flow and temperature in the Pacific Northwest region and reviewed literature on habitat restoration actions to determine whether they ameliorate a climate change effect or increase life history diversity and salmon resilience. Under the climate change scenarios considered here, summer low flows decrease by 35–75% west of the Cascade Mountains, maximum monthly flows increase by 10–60% across most of the region, and stream temperatures increase between 2 and 6°C by 2070–2099. On the basis of our literature review, we found that restoring floodplain connectivity, restoring stream flow regimes, and re‐aggrading incised channels are most likely to ameliorate stream flow and temperature changes and increase habitat diversity and population resilience. By contrast, most restoration actions focused on in‐stream rehabilitation are unlikely to ameliorate climate change effects. Finally, we illustrate how the decision support process can be used to evaluate whether climate change should alter the types or priority of restoration actions in a salmon habitat restoration plan. Copyright © 2012 John Wiley & Sons, Ltd.