bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improper hydrogen bonding and motional narrowing in binary mixtures of 2‐ and 3‐bromopyridine in methanol probed by polarized Raman study and DFT calculations
Authors: Ojha Animesh K. , Srivastava Sunil K. , Schlücker S. , Kiefer W. , Asthana B. P. , Singh Ranjan K. 
Published: December 2007

AbstractA concentration‐dependent Raman study of the ν(CBr) stretching and trigonal bending modes of 2‐ and 3‐Br‐pyridine (2Br‐p and 3Br‐p) in CH3OH was performed at different mole fractions of the reference molecule, 2Br‐p/3Br‐p, from 0.1 to 0.9 in order to understand the origin of blue/red wavenumber shifts of the vibrational modes due to hydrogen‐bond formation. The appearance of additional Raman bands in these binary systems at ∼617 cm−1in the case of 2Br‐p and at ∼618 cm−1 in the case of 3Br‐p compared to neat bromopyridine derivatives were attributed to specific hydrogen‐bonded complexes formed in the mixtures. The interpretation of experimental results is supported by density functional calculations on optimized geometries and vibrational wavenumbers of 2Br‐p and 3Br‐p and a series of hydrogen‐bonded complexes with methanol. The parameters obtained from these calculations were used for a qualitative explanation of the blue/red shifts. The wavenumber shifts and linewidth changes for the ν(CBr) stretching and trigonal bending modes as a function of concentration reveal that the caging effects leading to motional narrowing and diffusion‐causing line broadening are simultaneously operative, in addition to the blue shift caused due to hydrogen bonding. Copyright © 2007 John Wiley & Sons, Ltd.
Variable echo time imaging: Signal characteristics of 1‐M gadobutrol contrast agent at 1.5 and 3T
Authors: Stalder A.F. , Elverfeldt D. v. , Paul D. , Hennig J. , Markl M. 
Published: December 2007

AbstractGadobutrol (Gd‐Bt; Gadovist®, Schering AG) is a 1‐M Gadolinium (Gd)‐based contrast agent. Its higher Gd concentration allows for reduction of injection volumes in first pass contrast‐enhanced MR angiography (CE‐MRA) and should increase bolus sharpness and image quality. However, ambivalent results were reported. In order to explore the performance of 1‐M contrast agents such as Gd‐Bt and its dependence on molecular environment and temperature, signal characteristics were analyzed for a series of increasing Gd‐Bt concentrations for different temperature‐controlled samples in water and human blood plasma. Relaxation times, relaxivities, and signal‐concentration curves were assessed for several Gd‐Bt concentrations in water at 20°C and 37°C and in plasma at 37°C for 1.5T and 3T. Gd‐Bt concentration influence on signal intensity (SI) could be effectively simulated and compared with experimental measurements as well as simulations with other contrast agents at realistic in vivo concentrations. Particular attention was given to T2‐ and T‐induced losses at high concentrations, which annihilate benefits from T1 shortening. Based on these findings, variable echo time (VTE) approaches with readout bandwidth varying with k‐space position were explored in order to enhance the signal to noise performance of gradient echo imaging at high contrast agent concentrations. Results indicate the potential of VTE for imaging with increased SNR at high contrast agent concentrations. Magn Reson Med, 2007. © 2007 Wiley‐Liss, Inc.
Iterative projection reconstruction of time‐resolved images using highly‐constrained back‐projection (HYPR)
Authors: O'Halloran Rafael L. , Wen Zhifei , Holmes James H. , Fain Sean B. 
Published: December 2007

AbstractHighly‐constrained back‐projection (HYPR) is a technique for the reconstruction of sparse, highly‐undersampled time‐resolved image data. A novel iterative HYPR (I‐HYPR) algorithm is presented and validated in computer simulations. The reconstruction method is then applied to cerebral perfusion MRI simulated as a radial acquisition and contrast‐enhanced angiography of the head to assess feasibility in accelerating acquisitions requiring high temporal resolution and accurate representation of contrast kinetics. The I‐HYPR algorithm is shown to be more robust than standard HYPR in these applications in which the sparsity condition is not met or in which quantitative information is required. Specifically, iterative reconstruction of undersampled perfusion and contrast‐enhanced angiography data improved accuracy of the representation of contrast kinetics and increased the temporal separation of arterial and venous contrast kinetics. The I‐HYPR reconstruction may have important diagnostic applications in settings requiring high temporal resolution and quantitative signal dynamics. Because I‐HYPR allows relaxation of the sparsity requirements for the composite frame, the iterative reconstruction can enable novel acquisition strategies that independently optimize the quality of the composite and temporal resolution of the dynamic frames. Magn Reson Med, 2007. © 2007 Wiley‐Liss, Inc.
Unsupervised estimation of myocardial displacement from tagged MR sequences using nonrigid registration
Authors: Ledesma‐Carbayo Maria J. , Derbyshire J. Andrew , Sampath Smita , Santos Andrés , Desco Manuel , McVeigh Elliot R. 
Published: December 2007

AbstractWe propose a fully automatic cardiac motion estimation technique that uses nonrigid registration between temporally adjacent images to compute the myocardial displacement field from tagged MR sequences using as inputs (sources) both horizontally and vertically tagged images. We present a new multisource nonrigid registration algorithm employing a semilocal deformation model that provides controlled smoothness. The method requires no segmentation. We apply a multiresolution optimization strategy for better speed and robustness. The accuracy of the algorithm is assessed on experimental data (animal model) and healthy volunteer data by calculating the root mean square (RMS) difference in position between the estimated tag trajectories and manual tracings outlined by an expert. For the ∼20000 tag lines analyzed (45 slices over 20–40 time frames), the RMS difference between the automatic tag trajectories and the manually segmented tag trajectories was 0.51 pixels (0.25 mm) for the animal data and 0.49 pixels (0.49 mm) for the human volunteer data. The RMS difference in the separation between adjacent tag lines (RMS_TS) was also assessed, resulting in an RMS_TS of 0.40 pixels (0.19 mm) in the experimental data and 0.52 pixels (0.56 mm) in the volunteer data. These results confirm the subpixel accuracy achieved using the proposed methodology. Magn Reson Med 2007. © 2007 Wiley‐Liss, Inc.
Lifetime course of myasthenia gravis
Authors: Grob David , Brunner Norman , Namba Tatsuji , Pagala Murali 
Published: December 2007

AbstractBetween 1940 and 2000 a total of 1976 patients with myasthenia gravis (MG) were studied. Diagnosis was made by improvement in weakness after anticholinesterase medication. The historical developments in diagnosis and treatment of MG are reviewed. We analyzed the clinical course of MG as influenced by age, gender, thymectomy, thymomectomy, and the presence of antibodies to acetylcholine receptors (AChR). The clinical course of MG was significantly influenced by age and gender, and these need special attention in managing patients. The most severe level of weakness and high mortality occurred during the first 1 to 2 years of the disease, after which many patients experienced improvement. For treating MG patients the usefulness of thymectomy remains to be proven, and novel drugs need to be developed to increase the number as well as normal functioning of the AChRs and other components of the neuromuscular system. Muscle Nerve, 2007
Reconciliation of income and consumption data in poverty measurement
Authors: Bavier Richard 
Published: December 2007

AbstractA recent series of papers has renewed interest in the question of whether consumption data are superior to income data for poverty measurement. Although the Census Bureau has provided researchers with an experimental series of variables that can produce a comprehensive income measure, this resource has not been fully exploited in previous analyses. When poverty is measured by a comprehensive income measure, income poverty rates and trends are similar to consumption poverty rates. Arguments that income is measured with more error than consumption at the bottom of the distribution are shown to be based upon inferior income data. © 2008 by the Association for Public Policy Analysis and Management.
The relationship between income and material hardship
Authors: Sullivan James X. , Turner Lesley , Danziger Sheldon 
Published: December 2007

AbstractThis paper examines the relationship between income and the extent of material hardship and explores other factors that might affect hardship. Using panel data from the Women's Employment Study, we examine the incidence of material hardship from 1997 to 2003 among current and former welfare recipients. We then consider the extent to which income is associated with hardship. We show that hardship decreases monotonically across quintiles of the income distribution for several income measures. When we measure income as the average across the 6‐year study period, a 10 percent increase in average income is associated with a 1.1 percentage point decrease in the likelihood of experiencing a hardship, a drop of about 3.4 percent. We also find that the relationship between transitory changes in income and hardship is weak. These results are consistent with findings based on a nationally representative sample of disadvantaged households from the Survey of Income and Program Participation. Our results indicate that observable factors, such as measures of mental health, are more strongly related to hardship than current income. © 2008 by the Association for Public Policy Analysis and Management.
Direct certification in the national school lunch program expands access for children
Authors: Gleason Philip 
Published: December 2007

AbstractUnder the policy of direct certification for free school meals, school districts use information shared by state agencies about household eligibility for means‐tested programs in the state in order to determine the potential eligibility for free meals of students enrolled in the district. This information allows districts to automatically approve students in these eligible households for free meals without requiring the household to complete the application process. This paper examines the impacts of direct certification on students' likelihood of becoming certified for free meals, using data from a national survey of school food service directors as well as statelevel administrative data on program participation. A state‐level fixed effects model is estimated to account for the possibility of selection bias. The key finding is that direct certification leads to a statistically significant increase in the number of children getting free school meals. More generally, this finding highlights a promising approach for improving access to means‐tested programs without compromising program integrity. © 2008 by the Association for Public Policy Analysis and Management.
The negative impacts of starting middle school in sixth grade
Authors: Cook Philip J. , MacCoun Robert , Muschkin Clara , Vigdor Jacob 
Published: December 2007

AbstractUsing administrative data on public school students in North Carolina, we find that sixth grade students attending middle schools are much more likely to be cited for discipline problems than those attending elementary school. That difference remains after adjusting for the socioeconomic and demographic characteristics of the students and their schools. Furthermore, the higher infraction rates recorded by sixth graders who are placed in middle school persist at least through ninth grade. An analysis of end‐of‐grade test scores provides complementary findings. A plausible explanation is that sixth graders are at an especially impressionable age; in middle school, the exposure to older peers and the relative freedom from supervision have deleterious consequences. These findings are relevant to the current debate over the best school configuration for incorporating the middle grades. Based on our results, we suggest that there is a strong argument for separating sixth graders from older adolescents. © 2008 by the Association for Public Policy Analysis and Management.
An effectiveness‐based evaluation of five state pre‐kindergarten programs
Authors: Wong Vivian C. , Cook Thomas D. , Barnett W. Steven , Jung Kwanghee 
Published: December 2007

AbstractSince 1980, the number of state pre‐kindergarten (pre‐K) programs has more than doubled, with 38 states enrolling more than one million children in 2006 alone. This study evaluates how five state pre‐K programs affected children's receptive vocabulary, math, and print awareness skills. Taking advantage of states' strict enrollment policies determined by a child's date of birth, a regression‐discontinuity design was used to estimate effects in Michigan, New Jersey, Oklahoma, South Carolina, and West Virginia. For receptive vocabulary, only New Jersey and Oklahoma yielded significant standardized impacts, though two of the three other coefficients were in a direction indicating positive effects. For math, all the coefficients were positive but only Michigan and New Jersey yielded reliable results. The largest impacts were for print awareness, where all five coefficients were positive and four were reliable in Michigan, New Jersey, South Carolina, and West Virginia. The five states were not randomly selected and, on average, have higher quality program standards than non‐studied states, precluding formal extrapolation to the nation at large. However, our sample of states differed in many other ways, permitting the conclusion that state pre‐K programs can have positive effects on children's cognitive skills, though the magnitude of these effects varies by state and outcome. © 2008 by the Association for Public Policy Analysis and Management.
Mental health and substance abuse insurance parity for federal employees: How did health plans respond?
Authors: Barry Colleen L. , Ridgely M. Susan 
Published: December 2007

AbstractA fundamental concern with competitive health insurance markets is that they will not supply efficient levels of coverage for treatment of costly, chronic, and predictable illnesses, such as mental illness. Since the inception of employer‐based health insurance, coverage for mental health services has been offered on a more limited basis than coverage for general medical services. While mental health advocates view insurance limits as evidence of discrimination, adverse selection and moral hazard can also explain these differences in coverage. The intent of parity regulation is to equalize private insurance coverage for mental and physical illness (an equity concern) and to eliminate wasteful forms of competition due to adverse selection (an efficiency concern). In 2001, a presidential directive requiring comprehensive parity was implemented in the Federal Employees Health Benefits (FEHB) Program. In this study, we examine how health plans responded to the parity directive. Results show that in comparison with a set of unaffected health plans, federal employee plans were significantly more likely to augment managed care through contracts with managed behavioral health “carve‐out” firms after parity. This finding helps to explain the absence of an effect of the FEHB Program directive on total spending, and is relevant to the policy debate in Congress over federal parity. © 2008 by the Association for Public Policy Analysis and Management
Synthesis and characterization of surface‐initiated polymer brushes on silicon substrates by reversible addition fragmentation chain transfer polymerization
Authors: Wang Li‐Ping , Wang Yun‐Pu , Yuan Kun , Lei Zi‐Qiang 
Published: December 2007

AbstractPolymer brushes were prepared by using the reversible addition fragmentation chain transfer (RAFT) technique. The silicon substrates (Si (111) surface) were modified with ethyl xanthate groups which were introduced by the treatment of Si (111) surface with sodium ethyl xanthate. The polymer brushes were then prepared under RAFT conditions from the Si (111) wafer. Its “living” characteristics were determined by a series of characterizations including gel permeation chromatography (GPC), ellipsometry, and contact angle measurements. The results showed a well‐defined graft layer consisting of polymer brushes with low‐polydispersity could be prepared directly on Si (111)‐X surface (where X represents an ethyl xanthate groups). The structure of the polymer brushes was characterized and confirmed with the surface sensitive techniques such as X‐ray photoelectron spectroscopy (XPS) and scanning probe microscopy (SPM). Copyright © 2007 John Wiley & Sons, Ltd.
Synthesis and photopolymerization kinetics of benzophenone piperazine one‐component initiator
Authors: Xiao Pu , Wang Ying , Dai Mingzhi , Wu Gangqiang , Shi Suqing , Nie Jun 
Published: December 2007

AbstractA one‐component type II photoinitiator (PDBP), based on 4‐hydroxybenzophenone (HBP), acryloyl chloride, and piperazine, was synthesized and its structure was confirmed by 1H‐NMR. The photopolymerization kinetics of the photoinitiator was studied by real‐time Infrared spectroscopy (FT‐IR). It indicated that PDBP was a more effective photoinitiator than that of BP/triethylamine (TEA). The rate of polymerization, final conversion increased and the induction period shortened with increase in PDBP concentration, light intensity, and amine concentration. The kinetics of photopolymerization for TPGDA incorporating PDBP in the presence of different tertiary amines as the initiating system indicated that the PDBP/TEA combination exhibited the highest polymerization rates among the PDBP/amine combinations. Copyright © 2007 John Wiley & Sons, Ltd.
Stability of β‐galactosidase immobilized on composite microspheres of artemisia seed gum and chitosan
Authors: Zhang Ji , Zhang Shengtang , Wang Yunpu , Gao Sufang 
Published: December 2007

AbstractIn this work, composite microspheres were prepared by using artemisia seed gum and chitosan as a source. The composite microspheres have activated aldehyde groups by using glutaraldehyde. β‐Galactosidase was covalently bound on these activated microspheres. The properties of the immobilized enzyme were investigated and compared with those of the free enzyme, for which o‐nitrophenol β‐D‐galactopyranoside (ONPG) was chosen as a substrate. The results showed that the pH and thermal stability of the immobilized β‐galactosidase were higher than those of the soluble one. Apart from these, the Michaelis constant Km was evaluated for the immobilized β‐galactosidase and the soluble enzyme. The immobilized β‐galactosidase exhibited better environmental adaptability and reusability than the soluble one. POLYM. COMPOS., 29:9–14, 2008. © 2007 Society of Plastics Engineers
Preparation of polyaniline–polypyrrole composite sub‐micro fibers via interfacial polymerization
Authors: Xing Shuangxi , Zhao Guoku , Yuan Yong 
Published: December 2007

AbstractPolyaniline–polypyrrole (PANI–PPy) composite sub‐micro fibers were prepared via interfacial polymerization of aniline and pyrrole using ammonium persulfate (APS) as oxidant. Carbon tetrachloride was used as the organic solvent to dissolve the monomers and APS was dissolved in HCl aqueous solution. The reaction was carried out at the interface formed by the two above solutions. Scanning electron microscopy, Fourier transformation infrared spectra and differential thermal analysis were conducted to characterize the morphology, structure and thermostability of the resulting composites. Dodecyl benzene sulfonic acid was also used as medium to make comparison with that using HCl in the reaction system. The guidance of the formation of the PANI nanofibers at the first step and the interaction between PANI and PPy were considered as the drive forces to yield the composite sub‐micro fibers. POLYM. COMPOS., 29:22–26, 2008. © 2007 Society of Plastics Engineers
Effect of curing agent on the properties of mineral silica filled epoxy composites
Authors: Teh P.L. , Mariatti M. , Wagiman A.N.R. , Beh K.S. 
Published: December 2007

AbstractPolymer materials have been used extensively as the organic substrate materials in electronic packaging industry. The mechanical, thermal, and morphology properties of the alternative low cost composites have been investigated in this article. One of the materials is epoxy resin cured by aliphatic amine, and the other is cured by aromatic amine. It was found that the physical, mechanical, and thermal properties of epoxy resins are strongly depended on the curing agents. Morphology changed differently in these two epoxy‐curing systems. Crosslink density obtained from rubbery modulus in dynamic flexural storage modulus showed aromatic amine functionality group that gives higher crosslink density and increased in physical, mechanical, and thermal properties. POLYM. COMPOS., 29:27–36, 2008. © 2007 Society of Plastics Engineers
Thermal and electrical behavior of vinylester resin matrix composites filled with fly ash particles
Authors: Ray Dipa , Banerjee Sourish , Mohanty Amar K. , Misra Manjusri 
Published: December 2007

AbstractVinylester resin matrix composites were fabricated with 30, 40, 50, and 60% fly ash loading by room temperature casting method. The composites were subjected to thermogravimetric analysis. The 30 and the 60% composites showed a faster degradation at a lower temperature, whereas, the 40 and the 50% composites showed a higher onset temperature. The activation energy was calculated following Broido's equation and was found to be lowered in all the composites compared to the unfilled resin. The residue increased in all the composites proportionately with the increase in the fly ash content. The temperature variation resistance of the unfilled resin, 30 and 60% filled composites were measured and all the samples showed semi conducting nature in 40–60°C temperature range. POLYM. COMPOS., 29:58–62, 2008. © 2007 Society of Plastics Engineers
Curing behavior of epoxy/POSS/DDS hybrid systems
Authors: Zhang Zengping , Liang Guozheng , Ren Penggang , Wang Jieliang 
Published: December 2007

AbstractThe curing behavior of a difunctional epoxy resin/octa(aminopropyl)silsesquioxanes hybrid resin system using 4,4′′‐diaminodiphenyl sulfone as curing agent was studied. Fourier transform infrared (FTIR) spectroscopy was used to evidence the formation of the hybrid resin and to monitor the curing process. Results showed that the reactivity of the hybrid resin system was slightly lower than that of the pristine epoxy resin. Differential scanning calorimetry was used to study the curing kinetics of the hybrid resin. The curing kinetics of the pristine and hybrid resins was analyzed by two methods: Kissinger and Flynn‐Wall‐Ozawa methods. The FTIR analysis accorded well with the results of the kinetics study. POLYM. COMPOS., 29:77–83, 2008. © 2007 Society of Plastics Engineers