bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and HPLC application of chiral stationary phase from 4‐tert‐butylphenylcarbamates of cellulose and amylose immobilized onto silica gel
Authors: Li Jun‐qing , Ikai Tomoyuki , Okamoto Yoshio
Published: August 2009

The 4‐tert‐butylphenylcarbamates of cellulose and amylose bearing a small amount of 3‐(triethoxysilyl)propyl residues were synthesized by a one‐pot process and efficiently immobilized onto a silica gel through intermolecular polycondensation of the triethoxysilyl groups. The obtained chiral packing materials (CPMs) were evaluated by HPLC. The polysaccharide derivatives containing about 1–2% of the 3‐(triethoxysilyl)propyl residue were efficiently immobilized with a high chiral recognition ability. The immobilized CPMs could be used with the eluents containing chloroform and tetrahydrofuran (THF), which cannot be used with the conventional coated‐type CPMs. By using these eluents, the chiral recognition for many racemates was improved.
Prediction of the chromatographic signal in gradient elution ion chromatography
Authors: Bolanča Tomislav , Stefanović Štefica Cerjan , Ukić Šime , Rogošić Marko , Luša Melita
Published: August 2009

This study describes the development of a signal prediction model in gradient elution ion chromatography. The proposed model is based on a retention model and generalized logistic peak shape function which guarantees simplicity of the model and its easy implementation in method development process. Extensive analysis of the model predictive ability has been performed for ion chromatographic determination of bromate, nitrite, bromide, iodide, and perchlorate, using KOH solutions as eluent. The developed model shows good predictive ability (average relative error of gradient predictions 1.94%). The developed model offers short calculation times as well as low experimental effort (only nine isocratic runs are used for modeling).
The management of obesity
Authors: Stanley John C.
Published: August 2009

The prevalence and incidence of obesity is rising as current ways of managing obesity are proving to be ineffective. The preferred approach is to induce an energy deficit by decreasing energy intake through a low calorie diet and increasing energy expenditure through exercise. In order to provoke body weight loss the changes in lifestyle that this approach involves have to be sustained and while some individuals have the motivation to do this the vast majority of the population has not. Very low calorie diets are ineffective as the body adapts to them by lowering energy expenditure and altering the macronutrient composition of low calorie diets has no additional effect. The anti‐obesity drugs orlistat, sibutramine and rimonabant can provoke body weight loss but all suffer from side effects. However, the explosion in our understanding of the factors that regulate energy intake is likely to lead to the development of more effective drugs with fewer side effects. Bariatric or weight reducing surgery is highly effective at provoking body weight loss but there are obvious barriers to its widespread use.
The Design of Biodegradable Microcarriers for Induced Cell Aggregation
Authors: Tan Huaping , Wu Jindan , Huang Dejuan , Gao Changyou
Published: August 2009

PLLA microspheres were aminolyzed in hexanediamine/propanol solution to introduce free amino groups on their surface, which were further transferred into aldehyde groups by a treatment of glutaraldehyde. Chitosan‐graft‐lactose was then covalently coupled via Schiff base formation. Morphological variation and chitosan‐graft‐lactose immobilization were characterized. In vitro culture of rabbit auricular chondrocytes demonstrated that the PLLA microcarriers could effectively support the cell attachment and particularly induce cell aggregation on their surface. The formed cell aggregates/microcarriers composite showed higher viability and extracellular matrix production. Thus, the PLLA microcarriers can be potentially used as an injectable delivery system for cartilage repair.

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Self‐Assembly Behavior and Optical Properties of Poly(3‐thiopheneacetate)/Dialkyldimethylammonium Complexes
Authors: Yoon Young‐Sik , Park Kwang‐Han , Lee Jong‐Chan
Published: August 2009

Poly(3‐thiopheneacetate)/dialkyldimethylammonium complexes (PTA‐Cn) were prepared by mixing regiorandom poly(3‐thiopheneacetic acid) with dialkyldimethylammonium bromide to study the effect of their self‐assembled structures on the optical properties. The lengths of the alkyl groups in the ammonium salts were varied from decyl (C10) to octadecyl (C18) groups. These complexes showed fully developed layer structures with ordered mesophases. PTA‐C16 and PTA‐C18 with longer alkyl groups showed side‐chain crystalline phases, and PTA‐C10, PTA‐C12, and PTA‐C14 with shorter alkyl groups showed side‐chain crystalline and liquid crystalline phases at room temperature. When PTA‐C18 was heated, a melting transition from side‐chain crystalline to smectic liquid crystalline phase was observed at 41.5 °C. The maximum absorption and emission wavelengths of these complexes increased with increasing alkyl chain length indicating that the π‐conjugated structure of the regiorandom thiophene backbone changes according to the alkyl groups.

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A Phase Blending Study on Rubber Blends Based on the Solubility Preference of Curatives
Authors: Guo Rui , Talma Auke G. , Datta Rabin N. , Dierkes Wilma K. , Noordermeer Jacques W. M.
Published: August 2009

Using previously obtained data on the solubilities of curatives in SBR, EPDM and in NBR, different mixing procedures were performed on 50/50 SBR/EPDM and NBR/EPDM blends. In contrast to a previous phase‐mixing study, the curatives were added to separate phases before final blending, in an attempt to control the curative distributions in the blends for optimal mechanical properties. Fillers were not applied in the system to exclude their influence on the dispersion of the curatives. The properties of such blends compounded by selective phase mixing are superior to those of blends compounded with normal mixing procedures.

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Fabrication of Aligned Poly(L‐lactide) Fibers by Electrospinning and Drawing
Authors: Afifi Amalina M. , Nakajima Hajime , Yamane Hideki , Kimura Yoshiharu , Nakano Shigeyuki
Published: August 2009

A new target collector was designed for taking up aligned nanofibers by electrospinning. The collector consists of a rotor around which several fins were attached for winding electrospun filaments continuously in large amounts. The alignment of the nanofibers wound on the collector was affected by the electrospinning conditions, such as the needle‐to‐collector distance and the applied voltage, but not by the rotation speed of the collector. At a voltage of 0.5 kV · cm−1, about 60% of the fibers were found to be aligned within an angle of ± 5° relative to the rotational direction of the collector. The fiber alignment was improved to 90% by drawing the fiber bundle 2–3 times at 110 °C. The drawing was also effective for crystal orientation of the fibers as revealed by WAXD. The drawn fibers show improved mechanical properties.

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Acorn‐Shape Polymeric Nano‐Colloids: Synthesis and Self‐Assembled Films
Authors: Misra Anuradha , Urban Marek W.
Published: August 2009

These studies show for the first time that the synthesis of two distinct phase‐separated copolymers within one colloidal particle, i.e., poly(methyl methacrylate) (PMMA)/n‐butylacrylate (nBA) and poly(nBA)/pentafluorostyrene (p‐PFS) phases, results in unique acorn‐shaped morphologies and are capable of coalescence. Spectroscopic and morphological analysis combined with contact angle measurements as well as thermodynamic modeling reveal that in an effort to create stable heterogeneous two‐phase particle morphologies it is essential to provide desirable interfacial energetic conditions during polymerization and to utilise monomers that have a similar glass transition temperature (Tg). Such colloidal particles are stable and are able to self‐assemble during coalescence, depending upon the surface energy of a substrate. When a particle monolayer coalesces on a high surface tension substrate, the p‐PFS phase expresses itself near the film–air interface, whereas for low surface energy substrates, the p‐PFS phase dominates the film–substrate interfacial regions.

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Precise Control of Photoinduced Birefringence in Azobenzene‐Containing Liquid‐Crystalline Polymers by Post Functionalization
Authors: Yu Haifeng , Kobayashi Takaomi , Ge Ziyi
Published: August 2009

A series of functionalized liquid‐crystalline polymer materials with different degrees of functionality was synthesized by a post Sonogashira cross‐coupling reaction of a polymer precursor. The post‐functionalization was carried out under mild conditions and showed a high yield. Although a highly birefringent azotolane group was introduced into the polymer precursor, the photoresponse of the functionalized liquid‐crystalline materials was not obviously changed. By adjusting the content of azotolane groups, precise control of the photoinduced birefringence was successfully obtained after thermal enhancement upon annealing. The present method to gain precise control of photoinduced birefringence might enable one to finely photocontrol the optical performances of materials, and may have a potential application as an advanced process for photonic materials.

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Model Development and Validation of Crystallization Behavior in Injection Molding Prototype Flows
Authors: Custódio Frederico J. M. F. , Steenbakkers Rudi J. A. , Anderson Patrick D. , Peters Gerrit W. M. , Meijer Han E. H.
Published: August 2009

To control the final properties of semi‐crystalline polymer products, an accurate prediction of the material microstructure developed upon processing is required. For that purpose a model for flow‐enhanced nucleation of semi‐crystalline polymers is proposed, which relates molecular deformation with the enhancement of crystallization. Flow kinematics, computed in a decoupled fashion, are used to solve a coupled viscoelastic stress—crystallization problem. Morphological features concerning the number, size, and shape of crystalline structures are predicted and a comparison is made with experimental results reported by Housmans et al.1,2 in which the morphology development of an isotactic polypropylene (iPP) resin was studied.

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New insights into small‐molecule inhibitors of Bcr‐Abl
Authors: Schenone S. , Bruno O. , Radi M. , Botta M.
Published: August 2009

Chronic myelogenous leukemia (CML) is a myeloproliferative disease associated with a defined genetic abnormality, the Bcr‐Abl fusion gene on the Philadelphia chromosome that expresses the constitutively activated tyrosine kinase (TK) Bcr‐Abl. This enzyme leads to the malignant transformation of primitive hematopoietic cells and to the consequent disease. The central role of Bcr‐Abl in the pathogenesis of CML culminated in the discovery of imatinib (an ATP‐competitive inhibitor), which is currently the frontline therapy for CML. Unfortunately, the initial enthusiasm generated by its high response rate has been dampened by the development of resistance, especially in the advanced phases of CML. To overcome imatinib resistance, several second‐generation ATP‐competitive inhibitors endowed with increased potency against imatinib‐resistant mutants have been developed: the dual Src/Abl inhibitor dasatinib and the Abl inhibitor nilotinib have been recently approved by US‐FDA for the treatment of imatinib‐resistant CML, and many other compounds are currently in clinical trial. Although second‐generation TK inhibitors have shown to be clinically effective against most of the imatinib‐resistant mutants, to date poor results have been obtained in the treatment of the Bcr‐Abl T315I mutant. In this review we will report the most interesting second‐generation Abl and dual Src/Abl inhibitors recently entered in clinical trial, but also the new ATP‐competitive and uncompetitive inhibitors published in the last few years, focusing on their chemical structure, mechanism of action, and structure–activity relationship.  © 2009 Wiley Periodicals, Inc. Med Res Rev, 31, No. 1, 1–41, 2010
The human rhinovirus: human‐pathological impact, mechanisms of antirhinoviral agents, and strategies for their discovery
Authors: Rollinger Judith M. , Schmidtke Michaela
Published: August 2009

As the major etiological agent of the common cold, human rhinoviruses (HRV) cause millions of lost working and school days annually. Moreover, clinical studies proved an association between harmless upper respiratory tract infections and more severe diseases e.g. sinusitis, asthma, and chronic obstructive pulmonary disease. Both the medicinal and socio‐economic impact of HRV infections and the lack of antiviral drugs substantiate the need for intensive antiviral research. A common structural feature of the approximately 100 HRV serotypes is the icosahedrally shaped capsid formed by 60 identical copies of viral capsid proteins VP1‐4. The capsid protects the single‐stranded, positive sense RNA genome of about 7,400 bases in length. Both structural as well as nonstructural proteins produced during the viral life cycle have been identified as potential targets for blocking viral replication at the step of attachment, entry, uncoating, RNA and protein synthesis by synthetic or natural compounds. Moreover, interferon and phytoceuticals were shown to protect host cells. Most of the known inhibitors of HRV replication were discovered as a result of empirical or semi‐empirical screening in cell culture. Structure–activity relationship studies are used for hit optimization and lead structure discovery. The increasing structural insight and molecular understanding of viral proteins on the one hand and the advent of innovative computer‐assisted technologies on the other hand have facilitated a rationalized access for the discovery of small chemical entities with antirhinoviral (anti‐HRV) activity. This review will (i) summarize existing structural knowledge about HRV, (ii) focus on mechanisms of anti‐HRV agents from synthetic and natural origin, and (iii) demonstrate strategies for efficient lead structure discovery. © 2009 Wiley Periodicals, Inc. Med Res Rev, 31, No. 1, 42–92, 2010
Probability or frequency? Expressing forecast uncertainty in public weather forecasts
Authors: Joslyn Susan L. , Nichols Rebecca M.
Published: August 2009

Is uncertainty expressed as frequency easier for non‐experts to understand than uncertainty expressed as probability? The experiment reported here compared participants' responses to the same wind speed forecast expressed several different ways. Three different uncertainty expressions were tested (90%, 9 times in 10, or 90 out of 100%). Also tested was whether understanding was improved by including a short phrase explaining, in lay terms, how the forecast was derived (adding a reference class). Results suggested that, contrary to prior research, participants better understood the forecast when it was presented in a probability format rather than a frequency format. Furthermore, specifying a reference class did not facilitate understanding. Copyright © 2009 Royal Meteorological Society
Neuromuscular morphometry of the vaginal wall in women with anterior vaginal wall prolapse
Authors: Inal Hasan Ali , Kaplan Petek Balkanlı , Usta Ufuk , Taştekin Ebru , Aybatlı Aysun , Tokuc Burcu
Published: August 2009

Introduction and Hypothesis

The aim of this study was to compare the changes in hystomorphometry and innervation of the anterior vaginal wall in women with and without anterior vaginal wall prolapse.

Methods

Eighty‐nine biopsy specimens were obtained from the anterior vaginal wall of women having a cystocele repaired (stage ≥II; prolapse group, 49) and the same location in patients with no prolapse (stage <II; control group, 40). Routine H&E staining and immunohistochemical staining for protein gene product 9.5 (PGP‐9.5) and smooth muscle α‐actin (SMA) were performed for all specimens.

Results

Number and diameter of the submucosal nerve fibers were significantly lower, submucosal distance to muscular region was significantly higher in the vaginal wall of patients with cystocele than in women with normal vaginal support. We found that there was a negative correlation between the vaginal delivery and the nerve number and diameter measurements, and positive correlation between the vaginal delivery and submucosal distance of muscular level.

Conclusions

Results indicate that women with a cystocele have a significantly lower total innervation and higher muscular distance of the anterior vaginal epithelium than the control subjects. Neurourol. Urodynam. 29:458–463, 2010. © 2009 Wiley‐Liss, Inc.
The effects of thermoform molding conditions on polyvinylchloride and polyethylene double layer package materials
Authors: Oksuz Mustafa , Alsac Cafer , Ates Murat
Published: August 2009

This work reports the effects of thermoform molding process conditions on polyvinylchloride (PVC) and polyethylene (PE) double layer package materials. Mechanical and microstructural properties of the package material were examined by different test methods which are tensile properties, tear resistances and scanning electron microscopy (SEM). Furthermore, package materials, which are produced in different conditions by thermoform molding. Effect of different mold depths and process temperatures on the samples are determined by thermal aging process at 60°C in first, third, and seventh days. With increase in mold depth from 25 mm to 75 mm, there is a significant increase in tensile strength from ∼45 MPa to ∼55 MPa, thermoform temperature at 150°C. The highest elongation of the material was obtained thermoform temperature at 165°C as 80%, mold depth at 35 mm. Tensile strength and elongation (%) of the material generally decrease by aging time with changing of mold depth (25, 35, and 75 mm) of the double layer package material. In addition, tear resistances of the material decrease via aging time in various thermoform temperatures (150°C, 165°C, and 175°C) due to the orientation of the segments. Scanning electron microscopic (SEM) images of the materials were taken for aging process in first, third, and seventh days. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Stability of ABS compounds subjected to repeated cycles of extrusion processing
Authors: Karahaliou E.‐K. , Tarantili P.A.
Published: August 2009

In this work, poly(acrylonitrile‐butadiene‐styrene) (ABS) was subjected to five subsequent extrusion cycles and the effect of prolonged exposure to heat and shear stresses on its structural and performance properties was investigated. More specifically, the resulting chemical changes were studied by attenuated total reflectance Fourier transform infrared spectroscopy, the thermal response was recorded on differential scanning calorimetry thermographs, whereas the thermal stability of reprocessed samples was detected with thermogravimetric analysis. Also, the rheological properties of the aforementioned compounds were investigated via melt flow index tests, to assess their processability during melt mixing and molding processes. Furthermore, the mechanical properties of the obtained composites were investigated and the observed interactions were interpreted in terms of the influence of each component on the functional properties of the final mixture. This attempt might be a contribution to recycling of ABS by means of techniques that include multiple reprocessing. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Improving the exfoliation of layered silicate in a poly(ethylene terephthalate) matrix using supercritical carbon dioxide
Authors: Samaniuk Joseph , Litchfield David , Baird Donald
Published: August 2009

A technique for improving the exfoliation of organically modified layered silicate (OMLS) in a poly(ethylene terephthalate) (PET) matrix using super critical carbon dioxide (scCO2) is compared to traditional direct melt blending. The process relies on the rapid expansion of a scCO2/OMLS mixture directly into the second stage of a single screw extruder where the clay and scCO2 mixture is subsequently melt blended with the PET matrix. The simple, environmentally benign process results in a more highly delaminated system than traditional direct melt compounding. X‐ray diffraction analysis is used to reveal improved clay morphologies and the resulting mechanical properties are examined. Rheology is used as a tool to draw conclusions about the effect that scCO2 has on reducing PET matrix degradation during processing. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Study of the cellular structure heterogeneity and anisotropy of polypropylene and polypropylene nanocomposite foams
Authors: Antunes Marcelo , Velasco Jose Ignacio , Realinho Vera , Solórzano Eusebio
Published: August 2009

This article presents the analysis of the processing parameters influence on the foaming behavior and cellular structure of PP‐montmorillonite foams. Polypropylene nanocomposites containing 5.0 phr of an organically‐modified montmorillonite (MMT) were initially melt‐compounded in a twin‐screw extruder with azodicarbonamide (ADC) and later foamed using a one‐step compression‐molding process. The cellular structure and morphology of the foams was assessed using both scanning and transmission electron microscopies. A time‐dependant double‐effect was observed during foaming: (1) first of all, the melt strength of the polymer, too high for shorter times, not allowing full cell growth, and too low for high foaming times due to thermal oxidation; (2) and polymer degradation, clearly observed for very high foaming times, directly affecting polymer's melt resistance. Comparatively, PP‐MMT foams exhibited a broader foaming time processing window, a more isometric type of cellular structure and decreased open‐cell contents, indicating an effective nucleation and cell wall stabilization induced by the exfoliated MMT particles. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
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

Di(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

Results 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

Nonwoven 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

To 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

The 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

Friction 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

An 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

Involvement 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

The 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

Biomarkers 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

When 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

In 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

This 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

Nuclear 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

One 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
Adaptively biased molecular dynamics: An umbrella sampling method with a time‐dependent potential
Authors: Babin Volodymyr , Karpusenka Vadzim , Moradi Mahmoud , Roland Christopher , Sagui Celeste
Published: August 2009

We discuss an adaptively biased molecular dynamics (ABMD) method for the computation of a free energy surface for a set of reaction coordinates. The ABMD method belongs to the general category of umbrella sampling methods with an evolving biasing potential. It is characterized by a small number of control parameters and an O(t) numerical cost with simulation time t. The method naturally allows for extensions based on multiple walkers and replica exchange mechanism. The workings of the method are illustrated with a number of examples, including sugar puckering, and free energy landscapes for polymethionine and polyproline peptides, and for a short β‐turn peptide. ABMD has been implemented into the latest version (Case et al., AMBER 10; University of California: San Francisco, 2008) of the AMBER software package and is freely available to the simulation community. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Electronic structure of the Li2 [X 1Σ] Li [2p] excited 2A″ surface
Authors: Byrd Jason N. , Montgomery John A. , Michels H. Harvey , Côté Robin
Published: August 2009

Potential energy surface calculations are reported for the lowest 2A″ surface arising from the Li2 [X 1Σ] + Li* [2P] interaction. The 2A″ surface with Cs symmetry, which correlates to the 2B1 surface in C2v symmetry and to the 2Pi surface in C∞v, has been calculated using second order restricted open‐shell Møller–Plesset theory. Our calculated surface has a minimum in C2v symmetry that resembles the ground state surface but does not exhibit the Jahn–Teller splitting found for the ground state potential energy surface. Dipole transition moments are calculated in C2v geometry near the 2A″ minima using the internally contracted multireference singles and doubles configuration interaction theory. We have also analyzed the long range behavior of this 2A″ surface by fitting the ab initio calculations at long range with a functional series of the form ±Cn/Rn. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Computing vibrational properties in hydrogen‐bonded systems using quantum wavepacket ab initio molecular dynamics
Authors: Iyengar Srinivasan S.
Published: August 2009

The recently developed quantum wavepacket ab initio molecular dynamics method is discussed. The approach combines quantum wavepacket dynamics with ab initio molecular dynamics and is useful in studying problems where nuclear quantum effects play an important role. Computational bottlenecks and associated solutions are outlined. Chemical applications dealing with vibrational properties in hydrogen‐bonded clusters are discussed. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009