bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphology, mechanical properties, and durability of poly(lactic acid) plasticized with Di(isononyl) cyclohexane‐1,2‐dicarboxylate
Authors: Wang Ruyin , Wan Chaoying , Wang Shifeng , Zhang Yong 
Published: August 2009

AbstractDi(isononyl) cyclohexane‐1,2‐dicarboxylate (DINCH) was used as a new plasticizer for poly(lactic acid) (PLA), and the effects of DINCH and tributyl citrate ester (TBC) on the morphology, mechanical and thermal properties, and durability of PLA were compared. DINCH has limited compatibility with PLA, leading to PLA/DINCH blends with phase separation in which DINCH forms spherical dispersed phase. TBC is compatible with PLA and evenly distributed in PLA. Plasticized PLA with 10 and 20 phr DINCH have a constant glass transition temperature (Tg) of 50°C and are stiff materials with high elongation at break and impact strength. TBC could significantly decrease the Tg and increase the crystallinity of PLA, and PLA/TBC (100/20) blend is a soft material with a Tg of 24°C. The durability of plasticized PLA was characterized by weight loss measurement under water immersion, mechanical properties, and thermal analysis. The results reveal that PLA/DINCH blends have better water resistance and aging resistance properties than PLA/TBC blends, which is attributed to the relatively high hydrophobicity of DINCH and high Tg of PLA/DINCH blends. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Mechanical properties and water vapor permeability of starch/montmorillonite nanocomposites
Authors: Maksimov Robert D. , Lagzdins Aivars , Lilichenko Nadezda , Plume Egils 
Published: August 2009

AbstractResults of an investigation into an unmodified‐montmorillonite (MMT)‐filled nanocomposite based on plasticized starch are reported. Data on the influence of MMT content on the tensile mechanical properties of the material are presented. Particular attention is given to the water vapor permeability of the nanocomposite. It is found that the resistance to water permeation of plasticized starch can be improved considerably by introducing a rather small amount of the filler into it. Data on the influence of MMT content on the coefficients of moisture diffusion, solubility, and permeability are reported. Also, a simple method for determining the effect of irregularly oriented platelike filler particles on the permeability of the composite material is suggested. The calculation results are compared with experimental data. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Charge storage of electrospun fiber mats of poly(phenylene ether)/polystyrene blends
Authors: Lovera Deliani , Bilbao Cristina , Schreier Philipp , Kador Lothar , Schmidt Hans‐Werner , Altstädt Volker 
Published: August 2009

AbstractNonwoven fiber mats composed of poly(phenylene ether) (PPE) and polystyrene (PS) blends were prepared by electrospinning of PPE/PS solutions in a mixture of chloroform and hexafluoroisopropanol. The blends showed higher electrospinnability and led to thinner fibers (200 nm–1.3 μm) than the pure components, because of a proper balance of electrical conductivity and interaction with the electrospinning solvent. The charge retention of the electrospun fibers was evaluated and related to the blend composition and the electret properties of the components. It was found that the nonwoven mats were able to retain up to 60% of the initial surface potential after several days of annealing at temperatures as high as 140°C, which is markedly higher than the charge retention of corona‐charged compact films. The capability of the electrospinning technique, to inject charges into the bulk of the material and to orientate the dipoles of the PPE phase in the field direction at the same time, was related to the good surface potential stability of the PPE/PS electrospun fiber mats. The possibility of creating thin PPE/PS fibers with excellent charge retention capabilities makes these materials ideal candidates for electret filter and sensing applications. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Single‐walled carbon nanotube/ultrahigh‐molecular‐weight polyethylene composites with percolation at low nanotube contents
Authors: Grady Brian P. , Arthur David J. , Ferguson John 
Published: August 2009

AbstractTo mix single‐walled carbon nanotubes (SWCNTs) with a polymer and to achieve low percolation thresholds, a low‐viscosity liquid has been required in order to achieve sufficiently good dispersion. In this article, data are presented which show that percolation occurs at ∼0.14 wt % carbon nanotubes and the dispersion procedure does not involve dispersing the SWCNTs in a low‐viscosity liquid. Specifically, ultrahigh‐molecular‐weight polyethylene powder was mixed with a powder containing nanotubes and catalyst support, e.g., the powder contains 93% silica and 7% SWCNTs. The powder blend is compression molded into sheets using high pressure and temperature. Because of the very high viscosity of the resin, the nanotube/silica mixture largely stays segregated at the interface as shown by scanning electron microscopy. A significant drop in tensile properties (modulus, tensile strength, and elongation at break) occurs with filler incorporation. Non isothermal crystallization measurements indicate that this filler does not nucleate crystallinity when mixed in this manner; although there is a definite sharpening of the melt endotherm indicating that crystallites with smaller lamellar thicknesses are reduced significantly with filler addition. The addition of filler also slightly reduces the overall fractional crystallinity measured after a constant cooling rate. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Isothermal crystallization behavior of polyamide 6,6/multiwalled carbon nanotube nanocomposites
Authors: Lin Shi‐Ya , Chen Erh‐Chiang , Liu Kuang‐Yu , Wu Tzong‐Ming 
Published: August 2009

AbstractThe good dispersion of functionalized multiwalled carbon nanotube (f‐MWCNT) in polyamide 6,6 (PA 6,6) matrix was prepared by solution mixing techniques. The crystalline structure and crystallization behaviors of PA 6,6 and PA 6,6/f‐MWCNT nanocomposites were studied by X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and polarized optical microscopy (POM) analysis. DSC isothermal results revealed that the overall isothermal crystallization rates of PA 6,6 increased as well as the activation energy of PA 6,6 extensively decreased by adding f‐MWCNT into PA 6,6, suggesting that the addition of f‐MWCNT probably induces the heterogeneous nucleation. The effect of f‐MWCNT on the chain arrangement for the crystallization of PA 6,6/f‐MWCNT nanocomposites was also discussed. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Tribological behavior of polyamide 66‐based binary and ternary composites
Authors: Hu Haixia , Yu Sirong , Wang Mingyu , Liu Kaixin 
Published: August 2009

AbstractFriction and wear characteristics of polyamide 66 (PA66) and the composites of organoclay modified by styrene–ethylene/butylene–styrene triblock copolymer grafted with 1.84 wt% of maleic anhydride (SEBS‐g‐MA) were studied using an Universal Micro Tribometer reciprocating friction and wear tester. The morphologies of the wear tracks of PA66 and the composites were observed using a scanning electron microscope. The results showed that plastic deformation induced by the traction of the harder steel ball occurred on the worn surfaces of PA66 and the composite which were reinforced by SEBS‐g‐MA copolymer. It was found that the average frictional coefficient and specific wear rate of PA66/SEBS‐g‐MA binary composite are lowest under the same conditions. This indicates that toughness and wear resistance of PA66 matrix are improved with the incorporation of SEBS‐g‐MA copolymer. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Morphology and properties of SAN‐clay nanocomposites prepared principally by water‐assisted extrusion
Authors: Mainil Michaël , Urbanczyk Laetitia , Calberg Cédric , Germain Albert , Jerome Christine , Bourbigot Serge , Devaux Jacques , Sclavons Michel 
Published: August 2009

AbstractAn efficient extrusion process involving the injection of water while processing was used to prepare poly (styrene‐co‐acrylonitrile) (SAN)/clay nanocomposites with a high degree of nanoclay delamination. The usefulness of water‐assisted extrusion is highlighted here, in comparison with classical extrusion and roll mill processes. Cloisite® 30B (C30B), a montmorillonite clay organomodified with alkylammonium cations bearing 2‐hydroxyethyl chains, and pristine montmorillonite were melt blended with SAN (25 wt% AN) in a semi‐industrial scale extruder specially designed to allow water injection. XRD analysis, visual and TEM observations were used to evaluate the quality of clay dispersion. The relationship between the nanocomposite morphology and its mechanical and thermal properties was then investigated. The superiority of the SAN/C30B nanocomposite extruded with water has been evidenced by cone calorimetry tests and thermogravimetric measurements (TGA). These analyses showed a substantial improvement of the fire behavior and the thermal properties, while a 20% increase of the Young modulus was recorded. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers
Nitric oxide conduction by the brain aquaporin AQP4
Authors: Wang Yi , Tajkhorshid Emad 
Published: August 2009

AbstractInvolvement of aquaporins in gas conduction across the membrane and the physiological significance of this process have attracted marked attention from both experimental and theoretical studies. Previous work demonstrated that AQP1 is permeable to both CO2 and O2. Here we employ various simulation techniques to examine the permeability of the brain aquaporin AQP4 to NO and O2 and to describe energetics and pathways associated with these phenomena. The energy barrier to NO and O2 permeation through AQP4 central pore is found to be only ∼3 kcal mol−1. The results suggest that the central pore of AQP4, similar to that of AQP1, can indeed conduct gas molecules. Interestingly, despite a longer and narrower central pore, AQP4 appears to provide an energetically more favorable permeation pathway for gas molecules than AQP1, mainly due to the different orientation of its charged residues near the pore entrance. Although the low barrier against gas permeation through AQP4 indicates that it can participate in gas conduction across the cellular membrane, physiological relevance of the phenomenon remains to be established experimentally, particularly since pure lipid bilayers appear to present a more favorable pathway for gas conduction across the membrane. With an energy well of −1.8 kcal mol−1, the central pore of AQP4 may also act as a reservoir for NO molecules to accumulate in the membrane. Proteins 2010. © 2009 Wiley‐Liss, Inc.
TrimethylamineN‐oxide influence on the backbone of proteins: An oligoglycine model
Authors: Hu Char Y. , Lynch Gillian C. , Kokubo Hironori , Pettitt B. Montgomery 
Published: August 2009

AbstractThe study of organic osmolytes has been pivotal in demonstrating the role of solvent effects on the protein backbone in the folding process. Although a thermodynamic description of the interactions between the protein backbone and osmolyte has been well defined, the structural analysis of the effect of osmolyte on the protein backbone has been incomplete. Therefore, we have performed simulations of a peptide backbone model, glycine15, in protecting osmolyte trimethylamineN‐oxide (TMAO) solution, in order to determine the effect of the solution structure on the conformation of the peptide backbone. We show that the models chosen show that the ensemble of backbone structures shifts toward a more collapsed state in TMAO solution as compared with pure water solution. The collapse is consistent with preferential exclusion of the osmolyte caused by unfavorable interactions between osmolyte and peptide backbone. The exclusion is caused by strong triplet correlations of osmolyte, water, and peptide backbone. This provides a clear mechanism showing that even a modest concentration of TMAO forces the protein backbone to adopt a more collapsed structure in the absence of side chain effects. Proteins 2010. © 2009 Wiley‐Liss, Inc.
The use of post‐translationally modified peptides for detection of biomarkers of immune‐mediated diseases
Authors: Papini Anna Maria 
Published: August 2009

AbstractBiomarkers are decision‐making tools at the basis of clinical diagnostics and essential for guiding therapeutic treatments. In this context, autoimmune diseases represent a class of disorders that need early diagnosis and steady monitoring. These diseases are usually associated with humoral or cell‐mediated immune reactions against one or more of the body's own constituents. Autoantibodies fluctuating in biological fluids can be used as disease biomarkers and they can be, thus, detected by diagnostic immunoassays using native autoantigens. However, it is now accepted that post‐translational modifications may affect the immunogenicity of self‐protein antigens, triggering an autoimmune response and creating neo‐antigens. In this case, post‐translationally modified peptides represent a more valuable tool with respect to isolated or recombinant proteins. In fact, synthetic peptides can be specifically modified to mimic neo‐antigens and to selectively detect autoantibodies as disease biomarkers. A ‘chemical reverse approach’ to select synthetic peptides, bearing specific post‐translational modifications, able to fishing out autoantibodies from patients' biological fluids, can be successfully applied for the development of specific in vitro diagnostic/prognostic assays of autoimmune diseases. Herein, we report the successful application of this approach to the identification of biomarkers in different autoimmune diseases, such as systemic lupus erythematosus, rheumatoid arthritis and multiple sclerosis. Copyright © 2009 European Peptide Society and John Wiley & Sons, Ltd.
Determining near‐boundary departure points in semi‐Lagrangian models
Authors: Wood Nigel , Staniforth Andrew , White Andy 
Published: August 2009

AbstractWhen the trajectory equation is discretised in semi‐Lagrangian models, the departure points can be spuriously located outside the model domain. Historically this has been addressed in an ad hoc manner by relocating any such departure point to the domain boundary. This procedure, whilst convenient, is not physically justified and is inaccurate. It is of particular concern for mass‐conserving, finite‐volume, semi‐Lagrangian schemes that use the locations of departure points to determine upstream volumes, since it can lead to spuriously massless or near‐massless volumes, and large errors in mass transport. This weakness of current discretisations is discussed. An improved near‐boundary discretisation of the trajectory equation is then proposed and analysed via an example. Crown Copyright © 2009. Reproduced with the permission of HMSO. Published by John Wiley & Sons Ltd.
The statistical properties of tropical ice clouds generated by the West African and Australian monsoons, from ground‐based radar–lidar observations
Authors: Protat A. , Delanoë J. , Plana‐Fattori A. , May P. T. , O'Connor E. J. 
Published: August 2009

AbstractIn the present paper we characterize the statistical properties of non‐precipitating tropical ice clouds (deep ice anvils resulting from deep convection and cirrus clouds) over Niamey, Niger, West Africa, and Darwin, northern Australia, using ground‐based radar–lidar observations from the Atmospheric Radiation Measurement (ARM) programme. The ice cloud properties analysed in this paper are the frequency of ice cloud occurrence, cloud fraction, the morphological properties (cloud‐top height, base height, and thickness), the microphysical and radiative properties (ice water content, visible extinction, effective radius, terminal fall speed, and concentration), and the internal cloud dynamics (in‐cloud vertical air velocity). The main highlight of the paper is that it characterizes for the first time the probability density functions of the tropical ice cloud properties, their vertical variability and their diurnal variability at the same time. This is particularly important over West Africa, since the ARM deployment in Niamey provides the first vertically resolved observations of non‐precipitating ice clouds in this crucial area in terms of redistribution of water and energy in the troposphere. The comparison between the two sites also provides an additional observational basis for the evaluation of the parametrization of clouds in large‐scale models, which should be able to reproduce both the statistical properties at each site and the differences between the two sites.The frequency of ice cloud occurrence is found to be much larger over Darwin when compared to Niamey, and with a much larger diurnal variability, which is well correlated with the diurnal cycle of deep convective activity. The diurnal cycle of the ice cloud occurrence over Niamey is also much less correlated with that of deep convective activity than over Darwin, probably owing to the fact that Niamey is further away from the deep convective sources of the region. The frequency distributions of cloud fraction are strongly bimodal and broadly similar over the two sites, with a predominance of clouds characterized either by a very small cloud fraction (less than 0.3) or a very large cloud fraction (larger than 0.9). The ice clouds over Darwin are also much thicker (by 1 km or more statistically) and are characterized by a much larger diurnal variability than ice clouds over Niamey. Ice clouds over Niamey are also characterized by smaller particle sizes and fall speeds but in much larger concentrations, thereby carrying more ice water and producing more visible extinction than the ice clouds over Darwin. It is also found that there is a much larger occurrence of downward in‐cloud air motions less than 1 m s−1 over Darwin, which together with the larger fall speeds retrieved over Darwin indicates that the life cycle of ice clouds is probably shorter over Darwin than over Niamey. Copyright © 2009 Royal Meteorological Society
DFT plus PCM calculation for pairing specificity of Watson–Crick‐type bases in aqueous solutions
Authors: Pacureanu Liliana , Simon Zeno 
Published: August 2009

AbstractThis study is aimed at explaining the preference for AT and CG pairings and the possible insertion of other tautomeric DNA base pairs such as GenolT, that respect energetic and steric requirements including at least two hydrogen bonds and 11 ± 0.5Å distance between the 9‐CH3 of purine and 5‐CH3 of pyrimidine. The calculated free energy of formation ΔΔG at the DFT B3LYP/6‐31G*‐PCM/BEM level pointed out the CG and AT pairs as the most favored, followed closely by GenolT, in good agreement with Michaelis–Menten first order kinetics (CG ≈ AT > GenolT). Unusual DNA base pairs complexes such as AG (BEM) and CT (PCM) resulted to be stable, but it is very difficult to assume that they are likely to be included in the double strand DNA. The calculated enthalpy and dipole moments of isolated DNA bases agree well with experiment. The free energy of hydration, ΔGhyd, was found to depend on the electrostatic term, while cavitation‐dispersion components are almost constant. The stability of DNA complexes in water resulted from PCM calculations is markedly influenced by the free energy of hydration. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
C++ OPPS, a new software for the interpretation of protein dynamics from nuclear magnetic resonance measurements
Authors: Zerbetto Mirco , Polimeno Antonino , Meirovitch Eva 
Published: August 2009

AbstractNuclear magnetic resonance (NMR) is a powerful tool for elucidating protein dynamics because of the possibility to interpret nuclear spin relaxation properties in terms of microdynamic parameters. Magnetic relaxation times T1, T2, and NOE depend on dipolar and quadrupolar interactions, on chemical shift anisotropy and cross‐correlation effects. Within the framework of given motional model, it is possible to express the NMR relaxation times as functions of spectral densities (Abragam, The Principles of Nuclear Magnetism; Oxford University Press: Clarendon, London, 1961), obtaining the connection between macroscopic observables and microscopic properties. In this context, recently Meirovitch et al. (Shapiro et al., Biochemistry 2002, 41, 6271, Meirovitch et al., J Phys Chem B 2006, 110, 20615, Meirovitch et al., J Phys Chem B 2007, 111, 12865) applied the dynamical model introduced by Polimeno and Freed (Polimeno and Freed, Adv Chem Phys 1993, 83, 89, Polimeno and Freed, J Phys Chem 1995, 99, 10995), known as the slowly relaxing local structure (SRLS) model, to the study of NMR data.The program C++OPPS (http://www.chimica.unipd.it/licc/), developed in our laboratory, implements the SRLS model in an user‐friendly way with a graphical user interface (GUI), introduced to simplify the work to users who do not feel at ease with the complex mathematics of the model and the difficulties of command line based programs. The program is an evolution of the old FORTRAN 77 implementation COPPS (COupled Protein Probe Smoluchowski) and presents a number of new features: the presence of an easy to use GUI written in JAVA; high calculation performance thanks to features of C++ language, employment of BLAS (basic linear algebra subprograms) library (Blackford et al., Trans Math Soft 2002, 28, 135) in handling matrix‐vector operations and parallelization of the code under the MPI (message passing interface) paradigm (Gropp et al., Parallel Comput 1996, 22, 789, Gropp and Lusk, User's Guide for mpich, a Portable Implementation of MPI Mathematics and Computer Science Division; Argonne National Laboratory, 1996); possibility to predict the diffusion tensor of the protein via a hydrodynamic approach (Barone et al., J Comp Chem, in press). A cluster version of C++OPPS was also developed, which can be easily accessed by users via the web. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Ab initio and DFT study of 31P‐NMR chemical shifts of sphingomyelin and dihydrosphingomyelin lipid molecule
Authors: Sugimori K. , Kawabe H. , Nagao H. , Nishikawa K. 
Published: August 2009

AbstractOne of the phospholipids, sphingomyelin (SM, N‐acyl‐sphingosine‐1‐phosphorylcholine) is the most abundant component of mammalian membranes in brain, nervous tissues, and human ocular lens. It plays an important role for apoptosis, aging, and signal transduction. Recently, Yappert and coworkers have shown that human lens sphingomyelin and its hydrogenated derivative, dihydrosphingomyelin (DHSM) are interacted with Ca2+ ions to develop human cataracts. Previously, we have investigated conformational differences between an isolated SM/DHSM molecule and Ca2+‐coordinated form by using density functional theory (DFT) for geometry optimization and normal mode analysis. As a result, one of stable conformers of SMs has a hydrogen bonding between hydroxyl group and phosphate group, whereas another conformer has a hydrogen bonding between hydroxyl and phosphate amide group. In this study, 31P‐Nuclear Magnetic Resonance (NMR) shielding constants of the obtained conformers are investigated by using ab initio and DFT with NMR‐gauge invariant atomic orbitals (NMR‐GIAO) calculations. The experimental 31P‐NMR chemical shifts of SMs and DHSMs have significant small value around 0.1 ppm. We consider the relative conformational changes between SMs and DHSMs affect the slight deviations of 31P‐NMR chemical shifts, and discuss intramolecular hydrogen bondings and the solvent effect in relation to NMR experimental reference. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009