bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and self‐assembly of novel amphiphilic copolymers poly(lactic acid)‐block‐poly(ascorbyl acrylate)
Authors: Wang Yanzhai , Yang Junjiao , Yang Jing 
Published: July 2011

AbstractIn this study, a novel type of amphiphilic block copolymers poly(lactic acid)‐block‐poly(ascorbyl acrylate) (PLA‐block‐PAAA) with biodegradable poly(lactic acid) as hydrophobic block and poly(ascorbyl acrylate) (PAAA) as hydrophilic block was successfully developed by a combination of ring‐opening polymerization and atom transfer radical polymerization, followed by hydrogenation under normal pressure. The chemical structures of the desired copolymers were characterized by 1H NMR and gel permeation chromatography. The thermal physical properties and crystallinity were investigated by thermogravimetric analysis, differential scanning calorimetry, and wide angle X‐ray diffraction, respectively. Their self‐assembly behavior was monitored by fluorescence‐probe technique and turbidity change using UV–vis spectrometer, and the morphology and size of the nanocarriers via self‐assembly were detected by cryo‐transmission electron microscopy and dynamic light scattering. These polymeric micelles with PAAA shell extending into the aqueous solution have potential abilities to act as promising nanovehicles for targeting drug delivery. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Characterization of resulting network polymer precursors in stepwise crosslinking diepoxide/diamine polymerization
Authors: Matsumoto Akira , Kaneda Yujiro , Aota Hiroyuki 
Published: July 2011

AbstractOur previous mechanistic discussion of network formation in chainwise crosslinking multiallyl polymerization was extended to stepwise crosslinking diepoxide/diamine polymerization, typically including bisphenol‐A diglycidyl ether (BADGE) and 4,4′‐diaminodiphenylmethane (DDM). In allyl polymerization a monomer chain transfer is an essential termination reaction, providing only oligomeric primary polymer chains. Therefore, crosslinking multiallyl polymerization could be in the category of a classical gelation theory. Thus, the gelation behavior was discussed by comparing the actual gel point with the theoretical one. Then the resulting network polymer precursors (NPPs) were characterized by size‐exclusion chromatography‐multiangle laser light scattering‐viscometry to clarify the stepwise crosslinking BADGE/DDM polymerization mechanism. Notably, the intrinsic viscosity ratio [η]NPP/[η]Linear tended to decrease with the progress of crosslinking and finally, it reached less than 0.2. This suggests that the structure of resulting NPP becomes dendritic at a conversion close to the gel point. These dendritic NPPs can collide with each other to form crosslinks between NPPs, eventually leading to gelation as a reflection of the high concentration of NPP. The dilution effect on gelation was marked in polar solvent; no gelation was observed at a dilution of 1/5. However, in nonpolar solvent the gelation was promoted by dilution; this is ascribed to enhanced crosslink formation between NPPs through hydrogen bonding due to abundant hydroxyl groups in the NPP generated by the polyaddition reaction. Finally, the subject of “Is cured epoxy resin inhomogeneous?” is briefly discussed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Synthesis of well‐defined pH‐responsive PPEGMEA‐g‐P2VP double hydrophilic graft copolymer via sequential SET‐LRP and ATRP
Authors: Zhai Sujuan , Song Xuemei , Yang Dong , Chen Wulian , Hu Jianhua , Lu Guolin , Huang Xiaoyu 
Published: July 2011

AbstractA series of well‐defined double hydrophilic graft copolymers containing poly(poly(ethylene glycol) methyl ether acrylate) (PPEGMEA) backbone and poly(2‐vinylpyridine) (P2VP) side chains were synthesized by successive single electron transfer living radical polymerization (SET‐LRP) and atom transfer radical polymerization (ATRP). The backbone was first prepared by SET‐LRP of poly(ethylene glycol) methyl ether acrylate (PEGMEA) macromonomer using CuBr/tris(2‐(dimethylamino)ethyl)amine as catalytic system. The obtained homopolymer then reacted with lithium diisopropylamide and 2‐chloropropionyl chloride at −78 °C to afford PPEGMEA‐Cl macroinitiator. poly(poly(ethylene glycol) methyl ether acrylate)‐g‐poly(2‐vinylpyridine) double hydrophilic graft copolymers were finally synthesized by. ATRP of 2‐vinylpyridine initiated by PPEGMEA‐Cl macroinitiator at 25 °C using CuCl/hexamethyldiethylenetriamine as catalytic system via the grafting‐ from strategy. The molecular weights of both the backbone and the side chains were controllable and the molecular weight distributions kept relatively narrow (Mw/Mn ≤ 1.40). pH‐Responsive micellization behavior was investigated by 1H NMR, dynamic light scattering, and transmission electron microscopy and this kind of double hydrophilic graft copolymer aggregated to form micelles with P2VP‐core while pH of the aqueous solution was above 5.0. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Electro‐optical properties of electropolymerized poly(3‐hexylthiophene)/carbon nanotube composite thin films
Authors: Patel Romesh J. , Tighe Timothy B. , Ivanov Ilia N. , Hickner Michael A. 
Published: July 2011

Abstract3‐hexylthiophene was electropolymerized on a carbon nanotube (CNT)‐laden fluorine‐doped tin oxide substrate. Scanning electron microscopy and Raman spectroscopy revealed that the polymer was infused throughout the thickness of the 150‐nm thick CNT mat, resulting in a conducting composite film with a dense CNT network. The electropolymerized poly(3‐hexylthiophene) (e‐P3HT)/CNT composites exhibited photoluminescence intensity quenching by as much as 92% compared to the neat e‐P3HT, which provided evidence of charge transfer from the polymer phase to the CNT phase. Through‐film impedance and J‐V measurements of the composites gave a conductivity (σ) of 1.2 × 10−10 S cm−1 and zero‐field mobility (μ0) of 8.5 × 10−4 cm2 V−1 s−1, both of which were higher than those of neat e‐P3HT films (σ = 9.9 × 10−12 S cm−1, μ0 = 3 × 10−5 cm2 V−1 s−1). In electropolymerized samples, the thiophene rings were oriented in the (010) direction (thiophene rings parallel to substrate), which resulted in a broader optical absorbance than for spin coated samples, however, the lack of long‐range conjugation caused a blueshift in the absorbance maximum from 523 nm for unannealed regioregular P3HT (rr‐P3HT) to 470 nm for e‐P3HT. Raman spectroscopy revealed that π‐π stacking in e‐P3HT was comparable to that in rr‐P3HT and significantly higher than in regiorandom P3HT (ran‐P3HT) as shown by the principal Raman peak shift from 1444 to 1446 cm−1 for e‐P3HT and rr‐P3HT to 1473 cm−1 for ran‐P3HT. This work demonstrates that these polymer/CNT composites may have interesting properties for electro‐optical applications. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1269–1275, 2011
The oligomeric state of the truncated mechanosensitive channel of large conductance shows no variance in vivo
Authors: Iscla Irene , Wray Robin , Blount Paul 
Published: July 2011

AbstractThe mechanosensitive channel of large conductance (MscL) from E. coli serves as an emergency release valve allowing the cell to survive acute osmotic downshock. It is one of the best studied mechanosensitive channels and serves as a paradigm for how a protein can sense and respond to membrane tension. Two MscL crystal structures of the orthologs M. tuberculosis and S. aureus have been solved showing pentameric and tetrameric structures, respectively. Several studies followed to understand whether the discrepancy in their stoichiometry was a species difference or a consequence of the protein manipulation for crystallization. Two independent studies now agree that the full‐length S. aureus MscL is actually a pentamer, not tetramer. While detergents appear to play a role in modifying the oligomeric state of the protein, a cytoplasmic helical bundle has also been implicated. Here, we evaluate the role of the C‐terminal region of S. aureus MscL in the oligomerization of the channel in native membranes by using an in vivo disulfide‐trapping technique. We find that the oligomeric state of S. aureus MscLs with different C‐terminal truncations, including the one used to obtain the tetrameric S. aureus MscL crystal structure, are pentamers in vivo. Thus, the C‐terminal domain of the S. aureus protein only plays a critical role in the oligomeric state of the SaMscL protein when it is solubilized in detergent.
Extent of enthalpy–entropy compensation in protein–ligand interactions
Authors: Olsson Tjelvar S. G. , Ladbury John E. , Pitt Will R. , Williams Mark A. 
Published: July 2011

AbstractThe extent of enthalpy–entropy compensation in protein–ligand interactions has long been disputed because negatively correlated enthalpy (ΔH) and entropy (TΔS) changes can arise from constraints imposed by experimental and analytical procedures as well as through a physical compensation mechanism. To distinguish these possibilities, we have created quantitative models of the effects of experimental constraints on isothermal titration calorimetry (ITC) measurements. These constraints are found to obscure any compensation that may be present in common data representations and regression analyses (e.g., in ΔH vs. –TΔS plots). However, transforming the thermodynamic data into ΔΔ‐plots of the differences between all pairs of ligands that bind each protein diminishes the influence of experimental constraints and representational bias. Statistical analysis of data from 32 diverse proteins shows a significant and widespread tendency to compensation. ΔΔH versus ΔΔG plots reveal a wide variation in the extent of compensation for different ligand modifications. While strong compensation (ΔΔH and −TΔΔS opposed and differing by < 20% in magnitude) is observed for 22% of modifications (twice that expected without compensation), 15% of modifications result in reinforcement (ΔΔH and −TΔΔS of the same sign). Because both enthalpy and entropy changes arise from changes to the distribution of energy states on binding, there is a general theoretical expectation of compensated behavior. However, prior theoretical studies have focussed on explaining a stronger tendency to compensation than actually found here. These results, showing strong but imperfect compensation, will act as a benchmark for future theoretical models of the thermodynamic consequences of ligand modification.
Altered prostate epithelial development in mice lacking the androgen receptor in stromal fibroblasts
Authors: Yu Shengqiang , Yeh Chiuan‐Ren , Niu Yuanjie , Chang Hong‐Chiang , Tsai Yu‐Chieh , Moses Harold L , Shyr Chih‐Rong , Chang Chawnshang , Yeh Shuyuan 
Published: July 2011

AbstractBACKGROUNDAndrogens and the androgen receptor (AR) play important roles in the development of male urogenital organs. We previously found that mice with total AR knockout (ARKO) and epithelial ARKO failed to develop normal prostate with loss of differentiation. We have recently knocked out AR gene in smooth muscle cells and found the reduced luminal infolding and IGF‐1 production in the mouse prostate. However, AR roles of stromal fibroblasts in prostate development remain unclear.METHODSTo further probe the stromal fibroblast AR roles in prostate development, we generated tissue‐selective knockout mice with the AR gene deleted in stromal fibroblasts (FSP‐ARKO). We also used primary culture stromal cells to confirm the in vivo data and investigate mechanisms related to prostate development.RESULTSThe results showed cellular alterations in the FSP‐ARKO mouse prostate with decreased epithelial proliferation, increased apoptosis, and decreased collagen composition. Further mechanistic studies demonstrated that FSP‐ARKO mice have defects in the expression of prostate stromal growth factors. To further confirm these in vivo findings, we prepared primary cultured mouse prostate stromal cells and found knocking down the stromal AR could result in growth retardation of prostate stromal cells and co‐cultured prostate epithelial cells, as well as decrease of some stromal growth factors.CONCLUSIONSOur FSP‐ARKO mice not only provide the first in vivo evidence in Cre‐loxP knockout system for the requirement of stromal fibroblast AR to maintain the normal development of the prostate, but may also suggest the selective knockdown of stromal AR might become a potential therapeutic approach to battle prostate hyperplasia and cancer. Prostate 72:437–449, 2012. © 2011 Wiley Periodicals, Inc.
Raman spectroscopic investigation of phase separation and compositional fluctuations in nanocrystalline InxGa1−xN thin films prepared by modified activated reactive evaporation
Authors: Meher S. R. , Biju K. P. , Jain M. K. 
Published: July 2011

AbstractNano‐crystalline c‐axis oriented InxGa1−xN (x = 0.93, 0.63, 0.5, 0.36 and 0.18) thin films were prepared by modified activated reactive evaporation technique. Phase segregation was clearly observed for x = 0.5 composition. Scanning electron microscopy images reveal the average grain size for all the films to be varying from 40 to 85 nm. From, the absorption spectra the band gaps for the InGaN films were found to be varying from 1.89 to 2.92 eV. Micro‐Raman scattering at two different excitation energies (1.96 and 2.54 eV) were used to study the phase separation and compositional fluctuations of InGaN layers across their thickness. All the spectra exhibit the characteristic A1(LO) and E2 (high) modes corresponding to hexagonal wurtzite structure for both the excitations. No appreciable change in the peak positions for the two excitations confirms the absence of any significant phase separation across the thickness of InGaN films with x = 0.36 and 0.18 composition. However, for x = 0.93 and 0.63 films, gallium rich minority phase could be detected with 1.96 eV excitation. The changes in the area and FWHM of the two characteristic Raman peaks for different excitations are attributed to the increased structural defects across the sample depth and also to the near resonance effects.
Effects of annealing on the structural and photoluminescence properties of Zn0.98Cr0.02O thin films prepared by magnetron sputtering
Authors: Fu C. F. , Han L. F. , Liu C. 
Published: July 2011

AbstractCr‐doped ZnO thin films have been prepared on silicon substrates by magnetron sputtering method. The effects of annealing on the compositions, crystallographic structures, and optical properties of the thin films are systematically investigated by energy dispersive spectroscopy, X‐ray diffraction, and photoluminescence, respectively. The results show that the intensity of ZnO(002) peak firstly increases and then decreases with increasing the annealing temperature, whereas the full width at half maximum and the stress firstly decrease and then increase with the annealing temperature increasing. The higher crystallization quality and minimum stress was found for the samples annealed at 600 °C in oxygen ambient. It is also found from the photoluminescence spectra that the ultraviolet emission peak and green emission band are located at 380 nm and 500 nm, respectively. Further investigations indicate that the nature of the green emission is connected with the concentration of oxygen vacancies. In addition, the excellent luminescence performance of Cr‐doped ZnO thin films can be obtained by high temperature annealing at 600 °C in oxygen ambient, which can make green emission weakened gradually and even disappeared.
Dislocation reactions in hetero‐epitaxial (0001) GaN layers
Authors: Meng F. Y. , Mahajan S. 
Published: July 2011

AbstractDislocation reactions in hetero‐epitaxial GaN layers grown on (0001) sapphire were analyzed using weak beam dark field technique in transmission electron microscopy. Examples of the four basic reactions were observed. The average capture radius of the reactions was estimated from these observations.
Local structure determination of the nonlinear optical material LiNbO3using XRD
Authors: Saravanan R. , Thirumalaisamy T. K. , Kajitani T. 
Published: July 2011

AbstractThe ultimate crystal and electronic structure will give complete information of nonlinear materials for their potential applications. The electron density distribution and local structure of the nonlinear optical material LiNbO3have been studied and analyzed. Powder X‐ray data of LiNbO3is analyzed in terms of local structure. The bonding between the atoms has been studied using maximum entropy method and the bond‐length distribution using pair distribution function. The three‐dimensional, two‐dimensional electron density maps, and one‐dimensional electron density profiles have been constructed and analyzed. The particle size of LiNbO3has been analyzed using X‐ray diffractometer and SEM. The band gap energy has also been calculated using UV–visible absorption spectra.
Magnetic properties of exchange‐spring composite films
Authors: Kronmüller Helmut , Goll Dagmar 
Published: July 2011

AbstractHigh‐density magnetic recording in the Tbit/inch2 range is based on single bit, single domain particles in the nanometer range. In order to fulfil the prerequisites for high‐density recording the following magnetic properties must be guaranteed: Easy axis perpendicular to recording plane, thermal stability up to 200 °C, reversal fields of 1–2 T and switching times in the sub‐ns range. Composite nanoparticles composed of a soft and a hard magnetic layer are suitable to fulfil the above conditions. The magnetic ground states of exchange coupled bilayers are determined by micromagnetism and the corresponding reversal fields determined as a function of the soft magnetic film thickness. It is shown that the magnetic ground states are characterized by three configurations: in‐plane, oblique, and perpendicular magnetization depending on the thickness of the soft magnetic layer. These three ground states are characterized by reversal fields of different magnetization processes: Depinning of a charged Néel wall at the phase boundary for soft layer thicknesses Ls larger than the exchange length of the soft layer, spontaneous rotation of magnetization by a nucleation process for soft layer thicknesses smaller than the exchange length.
Atmospheric conservation properties in ERA‐Interim
Authors: Berrisford P. , Kållberg P. , Kobayashi S. , Dee D. , Uppala S. , Simmons A. J. , Poli P. , Sato H. 
Published: July 2011

AbstractWe study the global atmospheric budgets of mass, moisture, energy and angular momentum in the latest reanalysis from the European Centre for Medium‐Range Weather Forecasts (ECMWF), ERA‐Interim, for the period 1989–2008 and compare with ERA‐40. Most of the measures we use indicate that the ERA‐Interim reanalysis is superior in quality to ERA‐40. In ERA‐Interim the standard deviation of the monthly mean global dry mass of 0.7 kg m−2 (0.007%) is slightly worse than in ERA‐40, and long time‐scale variations in dry mass originate predominately in the surface pressure field. The divergent winds are improved in ERA‐Interim: the global standard deviation of the time‐averaged dry mass budget residual is 10 kg m−2 day−1 and the quality of the cross‐equatorial mass fluxes is improved. The temporal variations in the global evaporation minus precipitation (E − P) are too large but the global moisture budget residual is 0.003 kg m−2 day−1 with a spatial standard deviation of 0.3 kg m−2 day−1. Both the E − P over ocean and P − E over land are about 15% larger than the 1.1 Tg s−1 transport of water from ocean to land. The top of atmosphere (TOA) net energy losses are improved, with a value of 1 W m−2, but the meridional gradient of the TOA net energy flux is smaller than that from the Clouds and the Earth's Radiant Energy System (CERES) data. At the surface the global energy losses are worse, with a value of 7 W m−2. Over land however, the energy loss is only 0.5 W m−2. The downwelling thermal radiation at the surface in ERA‐Interim of 341 W m−2 is towards the higher end of previous estimates. The global mass‐adjusted energy budget residual is 8 W m−2 with a spatial standard deviation of 11 W m−2, and the mass‐adjusted atmospheric energy transport from low to high latitudes (the sum for the two hemispheres) is 9.5 PW. Copyright © 2011 Royal Meteorological Society
The relevance of facilitation in group decision making supported by a simulation model
Authors: Borštnar Mirjana Kljajić , Kljajić Miroljub , Škraba Andrej , Kofjač Davorin , Rajkovič Vladislav 
Published: July 2011

AbstractThis paper addresses the impact of feedback information and facilitation on a decision‐making process supported by a system dynamics model. We conducted the Solomon Four‐Group Experiment under four conditions: (a1) interrupted individual determination of a strategy supported by a simulation model and a facilitator; (a2) interrupted individual determination of a strategy supported by a simulation model and a facilitator plus group information feedback (GIF); (a3) continuous individual determination of a strategy supported by a simulation model; and (a4) continuous individual determination of a strategy supported by a simulation model plus GIF. The observed variables were criteria function (CF), frequency of simulation runs (FSR), and insight into GIF. The hypotheses that a simulation model supports individual learning and additional GIF contributes to faster learning were confirmed. The importance of the facilitator and structure of feedback information was demonstrated and a model explaining learning in the decision process was developed. Copyright © 2011 System Dynamics Society.
Analysing antibody response based on data obtained from serial dilution methods
Authors: Chan Linda S. , Overturf Gary D. , Selzer Jeffrey 
Published: July 2011

AbstractWe identify several problem areas in statistical analyses of data obtained from serial dilution methods in serology. We provide the mathematical backgrounds of the key elements involved in this field of study and discuss the statistical considerations. The problem areas include the use of the geometric mean as an expression of the average of a set of observations, the use of fold increase to measure antibody response, and the statistical analysis of the change in antibody response with respect to other variables, such as age and pretiter levels.
Adjusting proportional mortality ratios for the influence of extraneous causes of death
Authors: McDowall Michael 
Published: July 2011

AbstractProportional mortality ratios (PMRs) are frequently used where denominators of the population at risk are not available or are known to be seriously biased. The interpretation of proportional measures requires care and can be complicated by the fact that a PMR of a cause of interest may be affected by disproportionate mortality from one or more other causes of death. This problem is examined using occupational mortality data for England and Wales. A method of allowing for the influence of other causes of death on a PMR of interest is proposed and it is argued that this approach is a useful aid to the general interpretation of PMRs.
Concise Review: Expanding Roles for Hematopoietic Cellular Therapy and the Blood Transfusion Services
Authors: Hodby Katharine , Pamphilon Derwood 
Published: July 2011

AbstractHematopoietic stem cells (HSCs) have remained at the forefront of stem cell research for the past 50 years, since the therapeutic potential of bone marrow transplantation was realized. Uniquely, among stem and progenitor cells, research progress has been made in parallel between the laboratory benchtop and hospital bedside during this period. Integral to this work has been the role of the transfusion medicine services in the collection, storage, and processing of HSCs. The next decade promises to bring further developments: with new fields of cellular therapies, stem cell vaccination, and stem cell drug testing opening up. This article summarizes exciting areas of research concerning the behavior and potential clinical applications of HSCs. For the purposes of clarity, we describe in turn the trafficking and transfer of HSCs; ex vivo expansion of HSC units from different sources; and finally, applications of specifically selected subsets of hematopoietic cells and their progeny.