bluuebunny/crossref_metadata_2025 huggingface dataset:
Miniaturized two‐dimensional capillary electrophoresis on a microchip for analysis of the tryptic digest of proteins
Authors: Cong Yongzheng , Zhang Lihua , Tao Dingyin , Liang Yu , Zhang Weibing , Zhang Yukui
Published: January 2008

A two‐dimensional capillary electrophoresis platform, combining isoelectric focusing (IEF) and capillary zone electrophoresis (CZE), was established on a microchip with the channel width and depth as 100 μm and 40 μm, respectively. With polyacrylamide as permanent coating, EOF in the microchannel, which could impair the separation, was decreased to 3.4×10–9m2·V–1·s–1, about 1/10 of that obtained in the uncoated set‐up. During the separation, peptides were first focused by IEF in the first dimensional channel, and then directly driven into the perpendicular channel by controlling the applied voltages, and separated by CZE. Effects of various experimental parameters, including the electric field strength, channel length, and injection frequency from the first to the second dimensional separation channel, were studied. Under optimized condition, the digests of BSA and proteins extracted fromE. coliwere separated, and a peak capacity of 540 was obtained, which was far greater than that obtained by each single dimensional separation. All these results showed the promise of multidimensional separation on a microchip for the high‐throughput and high‐resolution analysis of complex samples.
Separation and determination of enkephalin‐related peptides by capillary electrophoresis with amperometric detection
Authors: Wang Wei , Yao Sheyue , Qiu Bin , Chen Guonan
Published: January 2008

A simple, reliable, and reproducible method for separation and determination of five enkephalin‐related peptides based on CE with amperometric detection (AD) is described in this paper. A potential of 1.0 V was applied to the carbon disk electrode, which was used as a working electrode in this system. At 15 kV of applied voltage, the five compounds were separated within 18 min in a 20 mmol/L phosphate buffer solution (PBS, pH 7.6) including 2.5% methanol v/v. LOD for five enkephalins were ranged from 6.31 to 54.3 nmol/L. The method was applied successfully to determine the five compounds added in the human cerebrospinal fluid (CSF) and the recoveries were in the range of 95.8–98.2%.
Melt Spinning of Poly(3‐hydroxybutyrate) for Tissue Engineering Using Electron‐Beam‐Irradiated Poly(3‐hydroxybutyrate) as Nucleation Agent
Authors: Vogel Roland , Voigt Dieter , Tändler Bernhard , Gohs Uwe , Häussler Liane , Brünig Harald
Published: January 2008

Electron‐beam‐irradiated poly(3‐hydroxybutyrate) was used as a nucleating agent for poly(3‐hydroxybutyrate) in a melt‐spinning process. Molecular data and thermal properties of the irradiated samples were determined. The thermal properties of the nucleated melts were determined to assess the influence of the nucleation agents, and then spinning tests were carried out. Thermal and textile properties of the spun fibers were also determined. Estimations of the improvement of the crystallization in the spinline and of the inhibition of secondary crystallization in the fibers from the use of the described blood‐compatible nucleation agents are given.

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Synthesis and Biological Evaluation of Disulfide‐Linked HPMA Copolymer‐Mesochlorin e6 Conjugates
Authors: Cuchelkar Vaikunth , Kopečková Pavla , Kopeček Jindřich
Published: January 2008

Novel polymeric delivery systems for the photosensitizer mesochlorin e6 (Mce6) were synthesized to overcome problems of systemic toxicity. A disulfide bond was included to allow for quick release of Mce6 from the N‐(2‐hydroxypropyl)methacrylamide (HPMA) copolymer backbone once internalized in tumor tissue. The synthesized conjugates demonstrated a time‐dependent reductive cleavage with an accompanying increase in the quantum yield of singlet oxygen generation on exposure to DTT. Quicker release kinetics and a higher cytotoxicity in SKOV‐3 human ovarian carcinoma cells were obtained as compared to polymer conjugate with a proteolytically cleavable GFLG spacer. These novel conjugates hold promise as clinically relevant drug delivery systems for photodynamic therapy of cancer.

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Corrosion control of phenylthiourea polymers on aluminium in alkaline medium
Authors: Vasanthi B. J. , Ravikumar L. , Selvaraj A.
Published: January 2008

Simple phenylthiourea compounds are known for their high solubility in alkaline medium and for good corrosion control. The monomer N‐(4‐hydroxy‐3‐methoxybenzal)‐N′‐(4′‐hydroxyphenyl) thiourea was condensed with pimeloylchloride and azeloylchloride through inter‐facial polycondensation method to synthesize the polymers. The polymers were dissolved in 2 N sodium hydroxide and their corrosion controlling efficiency on aluminium was studied through AC impedance and potentiodynamic polarization methods.
Local electrochemical properties of laser beam‐welded high‐strength Al–Zn–Mg–Cu alloys
Authors: Wloka J. , Hack T. , Virtanen S.
Published: January 2008

Butt welds of two high‐strength Al–Zn–Mg–Cu alloys with different zinc contents were welded by a laser beam welding technique. Due to the high energy density of the laser beam, the microstructural changes are confined to very thin regions. Electrochemical properties of the weld heat‐affected zones are investigated by local electrochemical measurement techniques and correlated with microhardness measurements, macroscopic corrosion behaviour and metallographic sections. It turned out that microelectrochemical techniques, especially the EC‐pen is a versatile and easy to handle tool for the resolution of changes in the electrochemical properties across a weld bead. It unveils modifications, which cannot be resolved by hardness measurements. By microcell measurements, local corrosion kinetics can be estimated.
Novel Hyperbranched Poly(aryl ether urethane)s Using AB2‐Type Blocked Isocyanate Monomers and Copolymerization with AB‐Type Monomers
Authors: Shanmugam Thiyagarajan , Nasar A. Sultan
Published: January 2008

A novel AB2‐type blocked isocyanate monomer was synthesized which was de‐blocked to provide a hyperbranched poly(aryl ether urethane). Copolymerization of this monomer with a functionally similar AB monomer yielded polymers with molecular weights in the range 8.0–310 kDa with a DB of 41–59% that underwent two‐stage decomposition above 200 °C. The inherent viscosities of the polymers in DMF ranged from 0.09 to 1.10 dL · g−1. End‐group modification of hyperbranched poly(aryl ether urethane)s was carried out with PEG monomethyl ether and 1‐decanol and affected the thermal properties and solubilities of the polymers. Tg of the polymers was reduced significantly from 201 to 71 °C upon incorporation of AB monomer in the copolymerization.

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Functional Mesoporous Polymers From Phenolic Building Oligomers
Authors: Yang Zhenglong , Wang Junwei , Huang Kun , Ma Jin , Yang Zhenzhong , Lu Yunfeng
Published: January 2008

Novel mesoporous polymers functionalized with carboxylic, sulfonic, and amino groups were synthesized by self‐organization of surfactant and functionalized phenolic building oligomers followed by surfactant removal. These materials have relatively large surface area, with a large number of functional groups on the pore walls, which may provide this new class of materials with enhanced adsorption capability and selectivity.

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Prozessüberwachung beim thermischen Spritzen durch die Analyse akustischer Emissionen verifiziert durch die Methoden der CFD zur Berechnung der Schallemission beim HVOF‐Verfahren
Authors: Wielage B. , Rupprecht C. , Paczkowski G.
Published: January 2008

Die zunehmende Automatisierung in der Thermischen Spritztechnik erfordert zuverlässige Prozessdiagnostikverfahren zur Sicherung der Beschichtungsqualität. Bisher kommen in der Industrie hauptsächlich optische Messverfahren zur Analyse der Spritzstrahlgeometrie und ‐partikelparameter zum Einsatz. Diese Verfahren sind im Gegensatz zur Akustikanalyse kostenintensiv und für schwach lichtemittierende Systeme wie HVOF‐ oder Kaltgasspritzen meist ungeeignet [1]. Da die starken akustischen Emissionen beim Thermischen Spritzen durch strömungsdynamische Effekte hervorgerufen werden, enthalten sie Informationen, die zur Bewertung der Funktionsfähigkeit und zur Weiterentwicklung von Spritzsystemen herangezogen werden können. Die vorliegende Arbeit zeigt Möglichkeiten, die akustischen Signale beim Lichtbogenspritzen und den Verbrennungslärm im HVOF‐Prozess messtechnisch zu erfassen. Dabei gewonnene Ergebnisse werden durch gekoppelte Methoden der Computed Fluid Dynamics (CFD) und Computed Akustik (CA) numerisch verifiziert. Da das Verständnis von akustischen Phänomenen auf der Physik der Schallausbreitung (Fluidschallakustik) basiert, erfolgt auszugsweise eine Darstellung der theoretischen Grundlagen.
Beurteilung von Loten und Lötverbindungen unter dem Einfluss steigender Kupfergehalte in verunreinigten bleifreien Lotbädern
Authors: Wielage B. , Weber D. , Lampke Th.
Published: January 2008

Zuverlässigkeit und Degradationsverhalten bleifreier Lote sind aufgrund von Widersprüchlichkeiten und notwendiger Problemlösungen nach wie vor Aspekte weiterer Untersuchungen. Die vorliegende Arbeit zeigt anhand von Phasenselektion der intermetallischen Phasen Ag3Sn und Cu6Sn5sowie (Cu,Ni)6Sn5und (Ni,Cu)3Sn4morphologisch‐mikrostrukturelle Zusammenhänge in Verbindung mit mechanischen Eigenschaften auf. Dazu wurden insbesondere das metallografische Tiefätzen und die instrumentierte Eindringprüfung genutzt. Die Lotlegierungen SnAg3,8CuX und SnCuXNi0,07 und deren Lötverbindungen wurden durch verschiedene Methoden komplex evaluiert. Es konnte nachgewiesen werden, dass das Zulegieren von Nickel als degradationsvermindernde Maßnahme des Kupfer‐Leachings zur Versprödung der Legierung durch das Wachstum der Phase (Cu,Ni)6Sn5führen kann.
ZnNi – Beschichtung hochfester Bauteile aus Stahl
Authors: Paatsch W. , Landgrebe R. , Lohrengel M. M.
Published: January 2008

Die galvanotechnische Beschichtung hochfester Bauteile aus Stahl erfordert in der ganzen Prozesskette der Vorbehandlung, Beschichtung und Nachbehandlung im allgemeinen besondere Maßnahmen, um die Möglichkeit eines wasserstoffinduzierten verzögerten Sprödbruches mit der erforderlichen Sicherheit auszuschalten. Entscheidend ist hierbei, dass der durch die Oberflächenbehandlung in den Werkstoff eingedrungene Wasserstoff in jedem Fall in einer bezüglich des Mechanismus der Wasserstoffversprödung unterkritischen Konzentration vorliegt. Im Allgemeinen wird dies dadurch erreicht, dass nach einer spezifischen Vorbehandlung und einer galvanotechnischen Beschichtung mit sehr hoher Stromausbeute der Metallabscheidung eine nachfolgende Temperaturbehandlung der beschichteten Bauteile durchgeführt wird. Letztere kann nach vorliegenden Praxisergebnissen offensichtlich unter speziellen Bedingungen bei der alkalischen ZnNi‐Beschichtung entfallen. Es wird hierzu erklärend auf elektrochemische Untersuchungen zur Keimbildung und zum Kristallwachstum, zur Ermittlung des Diffusionsverhaltens von Wasserstoff durch ZnNi‐Schichten, zu Messungen des lokalen Tiefenprofils von Wasserstoff an beschichteten Bauteilen sowie zum mechanischen Verhalten beschichteter Bauteile eingegangen.
B compensation in 3T cardiac imaging using short 2DRF pulses
Authors: Sung Kyunghyun , Nayak Krishna S.
Published: January 2008

The purpose of this study was to determine if tailored 2DRF pulses could be used to compensate for in‐plane variations of the transmitted RF field at 3T. Excitation pulse profiles were designed to approximate the reciprocal of the measured RF transmit variation where the variation over the left ventricle was approximated as unidirectional. A simple 2DRF pulse design utilizing three subpulses was used, such that profiles could be quickly and easily adapted to different regions of interest. Results are presented from phantom and in vivo cardiac imaging. Compared with conventional slice‐selective excitation, the average flip angle variation over the left ventricle (measured as the standard deviation divided by the mean flip angle) was reduced with P < 0.001 and the average reduction was 41% in cardiac studies at 3T. Magn Reson Med, 2008. © 2008 Wiley‐Liss, Inc.
A geometrically adjustable 16‐channel transmit/receive transmission line array for improved RF efficiency and parallel imaging performance at 7 Tesla
Authors: Adriany Gregor , Van de Moortele Pierre‐Francois , Ritter Johannes , Moeller Steen , Auerbach Edward J. , Akgün Can , Snyder Carl J. , Vaughan Thomas , Uğurbil Kâmil
Published: January 2008

A novel geometrically adjustable transceiver array system is presented. A key feature of the geometrically adjustable array was the introduction of decoupling capacitors that allow for automatic change in capacitance dependent on neighboring resonant element distance. The 16‐element head array version of such an adjustable coil based on transmission line technology was compared to fixed geometry transmission line arrays (TLAs) of various sizes at 7T. The focus of this comparison was on parallel imaging performance, RF transmit efficiency, and signal‐to‐noise ratio (SNR). Significant gains in parallel imaging performance and SNR were observed for the new coil and attributed to its adjustability and to the design of the individual elements with a three‐sided ground plane. Magn Reson Med, 2008. © 2008 Wiley‐Liss, Inc.
High‐pass GRAPPA: An image support reduction technique for improved partially parallel imaging
Authors: Huang Feng , Li Yu , Vijayakumar Sathya , Hertel Sarah , Duensing George R.
Published: January 2008

Partially parallel imaging (PPI) is a widely used technique in clinical applications. A limitation of this technique is the strong noise and artifact in the reconstructed images when high reduction factors are used. This work aims to increase the clinical applicability of PPI by improving its performance at high reduction factors. A new concept, image support reduction, is introduced. A systematic filter‐design approach for image support reduction is proposed. This approach shows more advantages when used with an important existing PPI technique, GRAPPA. An improved GRAPPA method, high‐pass GRAPPA (hp‐GRAPPA), was developed based on this approach. The new technique does not involve changing the original GRAPPA kernel and performs reconstruction in almost the same amount of time. Experimentally, it is demonstrated that the reconstructed images using hp‐GRAPPA have much lower noise/artifact level than those reconstructed using GRAPPA. Magn Reson Med, 2008. © 2008 Wiley‐Liss, Inc.
Smooth contact strategies with emphasis on the modeling of balloon angioplasty with stenting
Authors: Kiousis D. E. , Gasser T. C. , Holzapfel G. A.
Published: January 2008

Critical to the simulation of balloon angioplasty is the modeling of the contact between the artery wall and the medical devices. In standard approaches, the 3D contact surfaces are described by means of C0‐continuous facet‐based techniques, which may lead to numerical problems. This work introduces a novel contact algorithm where the target surfaces are described by polynomial expressions with C2‐continuity. On the basis of uniform cubic B‐splines, two different parametrization techniques are presented and compared, while the related implementation of the algorithm into a finite element analysis program is described. Two numerical examples are selected to demonstrate the special merits of the proposed contact formulation. The first example is a benchmark contact problem selected to point out the special features of the proposed strategies. The second example is concerned with the simulation of balloon angioplasty and stenting, where the contact between the balloon, the stent and the artery wall is numerically modeled. A patient‐specific 3D model of a stenotic femoral artery serves as a basis. The study concludes by identifying the changes in the mechanical environment of the artery in terms of contact forces and strains by considering two different stent designs. Copyright © 2008 John Wiley & Sons, Ltd.
An artificial compressibility method for viscous incompressible and low Mach number flows
Authors: Rahman M. M. , Siikonen T.
Published: January 2008

Within the framework of the pressure‐based algorithm, an artificial compressibility method is developed on a non‐orthogonal grid for incompressible and low Mach number fluid flow problems, using cell‐centered finite‐volume approximation. Resorting to the traditional pseudo‐compressibility concept, the continuity constraint is perturbed by the time derivative of pressure, the physical relevance of which is to invoke matrix preconditionings. The approach provokes density perturbations, assisting the transformation between primitive and conservative variables. A dual‐dissipation scheme for the pressure–velocity coupling is contrived, which has the expediences of greater flexibility and increased accuracy in a way similar to the monotone upstream‐centered schemes for conservation laws approach. To account for the flow directionality in the upwinding, a rotational matrix is introduced to evaluate the convective flux. Numerical experiments in reference to a few well‐documented laminar flows demonstrate that the entire contrivance expedites enhanced robustness and improved overall damping properties of the factored pseudo‐time integration procedure. Copyright © 2008 John Wiley & Sons, Ltd.
Supplementary data collection with case‐cohort analysis to address potential confounding in a cohort study of thromboembolism in oral contraceptive initiators matched on claims‐based propensity scores
Authors: Eng P. Mona , Seeger John D. , Loughlin Jeanne , Clifford C. Robin , Mentor BA. Sherry , Walker Alexander M.
Published: January 2008

Purpose

Residual confounding is a potential limitation of pharmacoepidemiologic studies, and in particular, studies based on administrative claims data that do not capture lifestyle and clinical confounders. We describe an application of the case‐cohort design to assess residual confounding by thromboembolic risk factors (e.g., smoking and obesity) not captured in claims data in a claims‐based cohort study of thromboembolism among matched oral contraceptive (OC) initiators.

Methods

This study was conducted using the Ingenix Research Data Mart, a database containing medical claims for approximately 12 million members of a large health plan of the United States. We randomly sampled 701 OC initiators from cohorts of ethinyl estradiol/drospirenone (n = 22 429) and other OC initiators (n = 44 858) identified in the years 2001–2004 and matched by propensity score in a claims‐based cohort study. Supplementary data on risk factors not measured in the cohort study were collected from medical records for the sample. We estimated the risk ratio of thromboembolism adjusted for the supplementary variables using Cox regression modified for a case‐cohort design, and compared it to the rate ratio from the cohort study.

Results

The risk ratio adjusted for the supplementary variables was 0.90 (95 per cent (%) confidence interval (CI): 0.49, 1.68) which was similar to the rate ratio (0.92; 95%CI: 0.50, 1.63), indicating negligible confounding by the supplementary variables in the cohort study.

Conclusions

Case‐cohort methods were used to assess residual confounding in a claims‐based cohort study. This approach adds to a growing number of methods to evaluate residual confounding in cohort studies. Copyright © 2008 John Wiley & Sons, Ltd.
Magnetite‐coated polystyrene hybrid microspheres prepared by miniemulsion polymerization
Authors: Wen Hui‐Ying , Gao Ge , Han Zhao‐Rang , Liu Feng‐Qi
Published: January 2008

Hybrid microspheres with a polystyrene core coated with magnetite nanoparticles were prepared by miniemulsion polymerization. Acrylic acid was used as a comonomer to promote the anchoring of the magnetite nanoparticles onto the polymeric surface. The addition of a hydrophobic agent prevents effectively the monomer from diffusing into the aqueous phase. Magnetite was treated with a silane coupling agent in order to introduce some interactions with the polymers. The morphology and the structure of the hybrid microspheres were characterized using X‐ray diffraction, infrared spectroscopy, transmission electron microscopy and thermogravimetric analysis. The results show that the morphology of the hybrid microspheres was influenced by the concentrations of acrylic acid, hydrophobic agent and surfactant, and that the degree of coating can be tuned by changing these parameters. The miniemulsion polymerization technique is adaptable to the synthesis of magnetite‐coated polymer particles, and the synthesis can be scaled up. Copyright © 2008 Society of Chemical Industry
Preparation and characterisation of polyamide–polyimide organoclay nanocomposites
Authors: Varley Russell J , Groth Andrew M , Leong KH
Published: January 2008

BACKGROUND: Ternary nanocomposites containing an organomodified layered silicate polyimide additive within a polyamide matrix have been investigated to gain greater insight into structure–property relationships and potential high‐temperature automotive applications.

RESULTS: Polyamide nanocomposite blends, containing 3 wt% of organoclay, were prepared and compared with organoclay‐reinforced polyamide and neat polyamide. Nanoclay addition significantly increased heat distortion temperature, as well as both the tensile and flexural moduli and strength. The addition of polyimide demonstrated further increases in heat distortion temperature, glass transition temperature and the flexural and tensile moduli by about 17, 21 and 40%, respectively. The tensile and flexural strengths were either unaffected or decreased modestly, although the strain‐to‐failure decreased substantially. Morphological studies using transmission electron microscopy (TEM) and X‐ray diffraction showed that the nanoclay was dispersed within the ternary blends forming highly intercalated nanocomposites, regardless of the presence and level of polyimide. However, TEM revealed clay agglomeration at the polyamide–polyimide interface which degraded the mechanical properties.

CONCLUSIONS: A range of improvements in mechanical properties have been achieved through the addition of a polyimide additive to a polyamide nanocomposite. The decrease in ductility, arising from the poor polyamide–polyimide interface and nanoclay clustering, clearly requires improving for this deficiency to be overcome. Copyright © 2008 Society of Chemical Industry
Kinetics of isothermal and non‐isothermal degradation of cellulose: model‐based and model‐free methods
Authors: Dahiya Jai Bhagwan , Kumar Krishan , Muller‐Hagedorn Matthias , Bockhorn Henning
Published: January 2008

BACKGROUND: The kinetics of the thermal decomposition of cellulosic materials is of interest from the viewpoint of flame retardancy for safety, optimization of incineration processes and reducing energy production from fossil sources and associated pollution. One essential step in these processes is the thermal degradation through mass and energy transport, which determines the rate of evolution of various types of products from cellulosic materials.

RESULTS: Kinetic parameters have been determined using various model‐based and model‐free methods in the thermal degradation of cellulose up to 700 °C in helium atmosphere. The values of the activation energy obtained in isothermal processes and non‐isothermal processes have been found to be not far from each other. From the integral method, the random nucleation (F1)‐type mechanism has been found most probable for cellulose degradation having an activation energy, Ea, in the range 156.5–166.5 kJ mol−1, lnA = 20–23 min−1, for first‐order reaction during its decomposition process at heating rates of 2, 5 and 10 °C min−1. Based on the high correlation coefficient, many types of mechanisms seem equally good for non‐isothermal degradation of cellulose.

CONCLUSION: The linear correlation coefficient has a limitation for verifying the correctness of a reaction mechanism in the study of degradation kinetics. Therefore, the correctness of a mechanism should be considered on the basis of comparing the kinetic parameters obtained from isothermal as well as non‐isothermal methods. Copyright © 2008 Society of Chemical Industry
Effect of Lewis acids on the Diels–Alder reaction in ionic liquids with different activation modes
Authors: Vidiš Ana , Küsters Ernst , Sedelmeier Gottfried , Dyson Paul J.
Published: January 2008

The Diels–Alder reaction has been examined in room temperature ionic liquids with high molar concentrations of Lewis acids under various conditions. A molar ratio of 10% catalyst gave a large increase in the selectivity and the yield of the reaction. The effect of catalysts on reaction rates was also examined under 100 MPa of pressure which leads to modest improvements in reaction rates. Ultrasound and microwave dielectric heating were also shown to improve the rate and, to a minor extent, selectivity of the examined reactions. Copyright © 2008 John Wiley & Sons, Ltd.
Kinetics and mechanism of the anilinolysis of dimethyl and diethyl chloro(thiono)phosphates
Authors: Kumar Dey Nilay , Hoque Md. Ehtesham Ul , Kim Chan Kyung , Lee Bon‐Su , Lee Hai Whang
Published: January 2008

The deuterium kinetic isotope effects (KIEs) involving deuterated aniline nucleophiles (XC6H4ND2) are reported for the reactions of dimethyl chlorophosphate (1), dimethyl chlorothionophosphate (2), diethyl chlorophosphate (3) and diethyl chlorothionophosphate (4) in acetonitrile at 55.0 °C. The obtained kH/kD values are 0.798–0.979, 0.945–1.06, 0.714–0.919 and 1.01–1.10 for 1, 2, 3 and 4, respectively. A concerted mechanism with dominant backside nucleophilic attack is proposed for the reactions of 1 and 3. A concerted mechanism involving partial frontside attack through a hydrogen‐bonded four‐centre‐type transition state (TS) is proposed for the reactions of 2 and 4. Copyright © 2008 John Wiley & Sons, Ltd.
Proteins multi‐funnel energy landscape and misfolding diseases
Authors: Cruzeiro L.
Published: January 2008

The problem of how a given α‐amino acid sequence, in cells, most of the times, assumes the native structure, is a fundamental problem in Biology, known as the protein folding problem. Here, evidence is presented that suggests that the same α‐amino acid sequence can assume several, very different, structures that have the same Gibbs energy as the native structure, in the same thermodynamic conditions. These results lend support to a multi‐funnel Gibbs energy landscape for proteins in which Anfinsen's thermodynamic hypothesis alone cannot explain protein folding. How then do proteins fold? In a multi‐funnel picture, transient deterministic forces are needed to select the native funnel from all other funnels that the protein can potentially fall into. The suggestion here is that such transient, deterministic forces arise from specific vibrational excited states (VES) that constitute the first step in protein folding and function (the VES hypothesis). An application of the VES hypothesis to calculate the energy absorbed, from water molecules, by a protein α‐helix with extensive glutamine (gln) repeats is made, which can explain the structural instability of these proteins and their association with many misfolding diseases. Copyright © 2008 John Wiley & Sons, Ltd.
Confined space regulated polymerization
Authors: You Ye‐Zi , Pan Cai‐Yuan
Published: January 2008

The confined space produced during the polymerization has access for all small organic molecules or oligomers with small size to enter this confined space; however, it can prevent the macromolecules with big size from entering. Therefore, the reaction between two branched macromolecules is excluded in A2+B3 polymerization system, resulting uncrosslinked branched polymers, and there was no gel point observed throughout the polymerization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1730–1737, 2008
Permeability control in electro‐sensitive microcapsules with immobilized ferroelectric liquid crystalline segments
Authors: Yoshida Masahiro , Matsui Tsutomu , Hatate Yasuo , Takei Takayuki , Shiomori Koichiro , Kiyoyama Shiro
Published: January 2008

Nylon‐polystyrene microcapsules with immobilized ferroelectric liquid crystalline segments were prepared, and permeability control of an encapsulated core material was investigated under an external electric field. A ferroelectric liquid crystal monomer possessing both mesogenicity and chirality responded effectively to the external electrical field. Permeation of the material (oxprenolol) contained in the inner aqueous core of the microcapsules was enhanced under a weak electric field (2 V). Furthermore, the permeability of oxprenolol did not depend on the external electric field in the absence of the ferroelectric liquid crystal segments. To clarify the controlled‐release mechanism of the core material, the light transmittance of the polymer membranes was quantitatively evaluated under an external electric field using a handmade polarized light transmittance apparatus. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1749–1757, 2008
Synthesis and characterization of sulfonated poly(phthalazinone ether phosphine oxide)s by direct polycondensation for proton exchange membranes
Authors: Ma Xuhui , Zhang Chunjie , Xiao Guyu , Yan Deyue , Sun Guoming
Published: January 2008

A series of sulfonated poly(phthalazinone ether phosphine oxide)s (sPPEPO) were prepared via aromatic nucleophilic substitution polycondensation of 4‐(4‐hydroxyphenyl) phthalazinone (HPPZ) with sulfonated bis(4‐fluorophenyl)phenyl phosphine oxide (sBFPPO) and bis(4‐fluorophenyl)phenyl phosphine oxide (BFPPO) at various ratios. The properties such as molecular weight, ion exchange capacity (IEC), swelling, thermal stability, proton conductivity, and morphology were investigated. sPPEPO with high IEC exhibited high proton conductivity while they still showed low swelling. Typically, sPPEPO with IEC of 1.54 and 1.69 meq/g exhibited high conductivity of 0.091 and 0.19 S/cm, and low swelling ratios of 14.3% and 19.5% at 80 °C, respectively. The low swelling was attributed to the strong intermolecular interaction including the electrostatic force and hydrogen bond. sPPEPO would be promising candidates used as polyelectrolyte membranes for fuel cells. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1758–1769, 2008
Solvent and concentration effects on the properties of electrospun poly(ethylene terephthalate) nanofiber mats
Authors: Veleirinho Beatriz , Rei Manuel F. , Lopes‐DA‐Silva J. A.
Published: January 2008

This study describes the preparation and characterization of nanofibrous mats obtained by electrospinning poly(ethylene terephthalate) (PET) solutions in trifluoroacetic acid/dichloromethane (TFA/DCM). Special attention was paid to the effect of polymer concentration and solvent properties on the morphology, structure, and mechanical and thermal properties of the electrospun nonwovens. The results show that the spinnable concentration of PET solution in TFA/DCM solvents is above 10 wt %. Mats have nanofibrous morphology with fibers having an average diameter in the range of 200–700 nm (depending on polymer concentration and solvent composition) and an interconnected pore structure. Higher solution concentration favors the formation of uniform fibers without beads and with higher diameter. Morphology and fiber assembly changed with the solvent properties. Solvent mixtures rich in TFA, i.e., those with higher dielectric constant and lower surface tension, originated fibers with small diameter. However, due to the lower volatility, those solvent mixtures also produced more branched and crosslinking fibers, with less morphologic uniformity. Mechanical properties (Young's modulus, ultimate strength, and elongation at break) and thermal properties (glass transition, crystallization, and melting) have been studied for the PET electrospun nanomats and compared with those of the original polymer. Solvent effect on fiber crystallinity was not significant, but a complex effect was observed on the mechanical properties of the electrospun mats, as a consequence of the different structural organization of the fibers within the mat network. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 460–471, 2008
Molecular motion, morphology, and thermal properties of multiwall carbon nanotube/polysilsesquioxane composite
Authors: Yuen Siu‐Ming , Ma Chen‐Chi M. , Teng Chih‐Chun , Wu Hsin‐Ho , Kuan Hsu‐Chiang , Chiang Chin‐Lung
Published: January 2008

Diglycidyl ether of bisphenol A (DGEBA)‐bridged polyorganosiloxane precursors have been prepared successfully by reacting diglycidyl ether of bisphenol A epoxy resin with 3‐aminopropyltriethoxysilane. Acid‐modified and unmodified multiwalled carbon nanotube (MWCNT) were dispersed in the diglycidyl ether of bisphenol A‐bridged polyorganosiloxane precursors and cured to prepare the carbon nanotube/diglycidyl ether of bisphenol A‐bridged polysilsesquioxane (MWCNT/DGEBA‐PSSQ) composites. The molecular motion of MWCNT/DGEBA‐PSSQ nanocomposites was studied by high‐resolution solid‐state 13C NMR. Acid‐modification can improve the affinity between MWCNT and the polymer matrix. The molecular motion of the DGEBA‐PSSQ decreased with acid‐modified MWCNT content. However, when unmodified MWCNT was used, the molecular motion of the DGEBA‐PSSQ was increased. SEM and TEM microphotographs confirm that acid‐modified MWCNT exhibits better dispersion than unmodified MWCNT in DGBEA‐PSSQ. The dynamic mechanical properties of acid‐modified MWCNT/DGBEA‐PSSQ composites are more favorable than those of unmodified MWCNT. Tg of the DGEBA‐PSSQ decreased from 174.0 °C (neat DGEBA‐PSSQ) to 159.0 °C (1 wt % unmodified MWCNT) and 156.0 °C (1 wt % acid‐modified MWCNT). The storage modulus (at 30 °C) of the DGEBA‐PSSQ increased from 1.23 × 109 Pa (neat DGEBA‐PSSQ) to 1.65 × 109 Pa (1 wt % acid‐modified MWCNT). However, when unmodified MWCNT was used, the storage modulus of the DGEBA‐PSSQ decreased to 6.88 × 108 Pa (1 wt % unmodified MWCNT). At high temperature, above 150 °C, storage modulus of nanocomposites was higher than that of neat polymer system. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 472–482, 2008
Current drug therapies for the secondary prevention of MI
Authors: Lang Ninian , Fox Keith
Published: January 2008

Current approaches to the secondary prevention of myocardial infarction include the use of both well‐established and newer agents. Our Drug review considers their mode of action and properties and the evidence base for their efficacy, followed by sources of further information and the Datafile. Copyright © 2008 Wiley Interface Ltd
Experimental investigation into the cushioning properties of honeycomb paperboard
Authors: Wang Dong‐Mei , Wang Zhi‐Wei
Published: January 2008

The cushioning properties of honeycomb paperboards are studied by means of experimental analysis. Experimental results indicate that the cushioning behaviour of paper honeycombs with and without liners are similar, but the cushioning capability is significantly larger for the material with liners. Experiment and theory show that the relative density of paper honeycomb core has a significant effect on the cushioning properties of honeycomb paperboards; however, the basis weight of the liner has only little effect. Experimental results also show that the energy absorption properties of multilayer honeycomb paperboards are not always higher than those of monolayer honeycomb paperboards, and that the height of honeycomb paperboard has an effect on its cushioning properties. These results can be used to characterize and improve the cushioning properties of honeycomb paperboard pads efficiently. Copyright © 2008 John Wiley & Sons, Ltd.
Quantitative analysis of small molecules by desorption electrospray ionization mass spectrometry from polytetrafluoroethylene surfaces
Authors: Ifa Demian R. , Manicke Nicholas E. , Rusine Allison L. , Cooks R. Graham
Published: January 2008

Desorption electrospray ionization mass spectrometry (DESI‐MS) is an emerging technique for ambient analysis. However, its application to routine quantitation has not been explored extensively and this is undertaken here. We present studies that utilize a particularly suitable surface, porous polytetrafluoroethylene (porous PTFE), which shows less cross contamination between samples and improved sensitivity and signal stability compared to other surfaces. Quantitative experiments for 1 µL spotted solutions of the β‐blocker propranolol, using isotopically labeled propranolol as internal standard, showed a good linear correlation (r2 > 0.996) over the range 0.01–100 µM. The inter‐day precision, based on the relative standard deviation, for replicates analyzed on three different days was 13% for 0.01 µM and better than 7% for the remainder of the calibration points. The inter‐day accuracy, expressed as relative error, was better than ±7% for all calibration points along the curve. These day‐to‐day measurements suggest that DESI‐MS can be successfully employed for routine quantitative analysis. The use of the analog atenolol as an internal standard and further considerations that should improve quantitation by DESI‐MS are also presented. Copyright © 2008 John Wiley & Sons, Ltd.
Determination of D/L‐amino acids by zero needle voltage electrospray ionisation
Authors: Sørensen Morten B. , Aaslo Per , Egsgaard Helge , Lund Torben
Published: January 2008

Ion formation may be made more efficient than in normal electrospray ionization (ESI) for certain classes of compounds, such as the polar amino acids Glu, Asn, His, Ser, Asp, Arg, Tyr and Lys, by adjusting the voltage of a normal ESI interface needle to zero voltage. For aspartic acid (Asp) the gain in signal‐to‐noise (S/N) ratio of the liquid chromatography/mass spectrometry (LC/MS) chromatograms obtained in the selective ion monitoring (SIM) mode (m/z 134) with zero needle potential was 40–50 times higher than detection at 4 kV. Ion formation at zero potential is likely to follow a mechanism related to sonic spray ionization. The utility of the zero needle voltage ESI was illustrated by determining the age of a human tooth by the aspartic acid epimerization method. The procedure involved separating the D‐ and L‐aspartic acid of a tooth extract on a chiral HPLC column and detection by zero voltage ESI‐MS3. Copyright © 2008 John Wiley & Sons, Ltd.
A novel ‘peak parking’ strategy for ultra‐performance liquid chromatography/tandem mass spectrometric detection for enhanced performance of bioanalytical assays
Authors: Li Fumin , Maguigad Jacob , Pelzer Mary , Jiang Xiangyu , Ji Qin C.
Published: January 2008

Sensitive and high‐throughput bioanalytical assays are of vital importance to drug discovery and development. Ultra‐performance liquid chromatography (UPLC), utilizing sub‐2‐µm particles, greatly increases the separation throughput and efficiency, resulting in LC peaks as narrow as or less than 1 s (full width at half maxima, FWHM). This, however, could pose practical challenges for bioanalytical applications using quadrupole mass spectrometry (MS) to acquire sufficient data points to ensure accurate and reliable quantitation. Here, we present a novel ‘peak parking’ strategy to reduce the flow rate during UPLC peak elution, therefore extending the useful MS acquisition window. The high‐throughput advantage of UPLC is maintained since no significant increase of the overall UPLC run time is needed. This strategy was demonstrated in an assay development for lansoprazole, a gastric proton‐pump inhibitor, in human plasma employing liquid‐liquid extraction. The method was validated from 50.0 to 50 000 pg/mL. Copyright © 2008 John Wiley & Sons, Ltd.
Recognizing mechanistic reasoning in student scientific inquiry: A framework for discourse analysis developed from philosophy of science
Authors: Russ Rosemary S. , Scherr Rachel E. , Hammer David , Mikeska Jamie
Published: January 2008

Science education reform has long focused on assessing student inquiry, and there has been progress in developing tools specifically with respect to experimentation and argumentation. We suggest the need for attention to another aspect of inquiry, namelymechanistic reasoning. Scientific inquiry focuses largely on understanding causal mechanisms that underlie natural phenomena. We have adapted an account of mechanism from philosophy of science studies in professional science [Machamer, P., Darden, D., & Craver, C. F., (2000). Thinking about mechanisms. Philosophy of Science, 67, 1–25] to develop a framework for discourse analysis that aids in identifying and analyzing students' mechanistic reasoning. We analyze a discussion among first‐grade students about falling objects (1) to illustrate the generativity of the framework, (2) to demonstrate that mechanistic reasoning is abundantly present even in these young students, and (3) to show that mechanistic reasoning is episodic in their discourse. © 2008 Wiley Periodicals, Inc.Sci Ed92:499–525, 2008
Preservice elementary teachers' views of their students' prior knowledge of science
Authors: Otero Valerie K. , Nathan Mitchell J.
Published: January 2008

Pre‐service teachers face many challenges as they learn to teach in ways that are different from their own educational experiences. Pre‐service teachers often enter teacher education courses with pre‐conceptions about teaching and learning that may or may not be consistent with contemporary learning theory. To build on preservice teachers' prior knowledge, we need to identify the types of views they have when entering teacher education courses and the views they develop throughout these courses. The study reported here focuses specifically on preservice teachers' views of their own students' prior knowledge and the implications these views have on their understanding of the formative assessment process. Sixty‐one preservice teachers were studied from three sections of a science methods course. Results indicate that preservice teachers exhibited a limited number of views about students' prior knowledge. These views tended to privilege either academic or experience‐based concepts for different aspects of formative assessment, in contrast to contemporary perspectives on teaching for understanding. Rather than considering these views as misconceptions, it is argued that it is more useful to consider them as resources for further development of a more flexible concept of formative assessment. Four common views are discussed in detail and applied to science teacher education. © 2008 Wiley Periodicals, Inc. J Res Sci Teach 45: 497–523, 2008
Ethnic identity, externalizing problem behaviour and the mediating role of self‐esteem among Dutch, Turkish‐Dutch and Moroccan‐Dutch adolescents
Authors: Wissink Inge B. , Deković Maja , Yağmur Şengül , Stams Geert Jan , de Haan Mariëtte
Published: January 2008

The present study examined whether self‐esteem mediates the relationship between two aspects of ethnic identity (i.e. ethnic identity exploration and ethnic identity commitment–affirmation) and externalizing problem behaviour in Dutch, Turkish‐Dutch and Moroccan‐Dutch adolescents living in the Netherlands. A total number of 345 adolescents (115 Dutch, 115 Turkish‐Dutch, 115 Moroccan‐Dutch) with a mean age of 14.5 filled in questionnaires at school. Turkish‐Dutch and Moroccan‐Dutch adolescents reported higher levels of both aspects of ethnic identity than their native Dutch counterparts, but there were no ethnic differences in self‐esteem and externalizing problem behaviour. Only in the Moroccan‐Dutch group was support found for the mediational model: stronger ethnic identity commitment–affirmation was related to a higher level of self‐esteem, which, in turn, was related to a lower level of externalizing problem behaviour.
Convergence and divergence among multiple methods for assessing adolescent romantic relationships
Authors: Galliher Renee V. , Enno Angela M. , Wright Robert
Published: January 2008

The problem solving conversations of 92 adolescent romantic couples were analyzed using two innovative techniques for capturing the meaning‐making processes in couples’ interactions. Couples were coded using the narrative coding system developed by the Family Narrative Consortium [Fiese, B. H. & Sameroff, A. J. (Eds.), (1999). The stories that families tell: Narrative coherence, narrative interaction, and relationship beliefs. With commentary from Philip A. Cowan.Monographs of the Society for Research on Child Development, 64(2, serial no. 257)], yielding measures of narrative coherence for each couple member and an assessment of couples’ capacity to engage in the interaction in a coordinated and mutually respectful manner. In addition, a video‐recall procedure captured couple members’ own subjective understanding of their own and their partners’ behaviors during the interaction. Moderate associations were observed between trained coders’, boyfriends’, and girlfriends’ perspectives, with more consistent links in some domains between girlfriends’ ratings and observers’ codes. In addition, indices of the quality of the interaction were linked to couple member global self reports of both positive and negative relationship quality, with many associations between observed interaction and global self reports of relationship quality achieving moderate effect sizes.
A subpopulation of capsaicin‐sensitive porcine dorsal root ganglion neurons is lacking hyperpolarization‐activated cyclic nucleotide‐gated channels
Authors: Obreja Otilia , Klusch Andreas , Ponelies Norbert , Schmelz Martin , Petersen Marlen
Published: January 2008

Hyperpolarization‐activated cyclic nucleotide‐gated (HCN) channels contribute to stabilizing resting membrane potential, thus controlling neuron excitability. Subclasses of nociceptive neurons differ in their excitability, therefore, these channels could be a distinguishing marker.

We investigated isolated dorsal root ganglion neurons from a non‐rodent species, the pig, Sus scrofa domesticus. Single labeling revealed capsaicin‐induced cobalt‐uptake in 54.3% and transient receptor potential V1 (TRPV1) immunoreactivity in 55.1% of all neurons. Ruthenium red and capsazepine suppressed capsaicin‐induced cobalt‐uptake. HCN‐1 and HCN‐2 channel isoform immunoreactivity was detected in 82.6% and 88.3%, respectively, and binding of IB4 in 29.4% of all neurons. Double labeling revealed that out of the capsaicin‐positive neurons, 42.3% were IB4‐positive, 80.0% immunoreactive for the HCN‐1, and 77.3% for the HCN‐2 channel isoform, respectively. Neurons lacking HCN‐1 or HCN‐2 channel isoforms were mostly capsaicin‐positive and IB4‐negative. The soma size of neurons lacking HCN‐1 and/or HCN‐2 channels was small to medium.

Western blot analysis showed protein products of sizes similar to those of HCN‐1 and HCN‐2 channel isoforms. Functionally, in patch‐clamp experiments, some neurons were unresponsive to membrane hyperpolarization, thus, probably lacking HCN channels.

In conclusion, in porcine dorsal root ganglion neurons there is a subset of capsaicin‐positive, IB4‐negative neurons lacking HCN‐1 and/or HCN‐2 channel isoforms.
Inter-specific parasite competition: mixed infections ofSchistosoma mansoniandS. rodhainiin the definitive host
Authors: NORTON A. J. , WEBSTER J. P. , KANE R. A. , ROLLINSON D.
Published: January 2008

Competition between parasite species has been predicted to be an important force shaping parasite and host ecology and evolution, although empirical data are often lacking. Using theMus musculus-Schistosoma mansoniandSchistosoma rodhainihost-parasite systems we characterized mate choice and inter-specific competition between these two schistosome species. Simultaneous infections revealed species-specific mate preferences for both species as well as suggesting mating competition, with maleS. rodhainiappearing dominant over maleS. mansoni.S. rodhainihomologous pairs were also shown to have increased reproduction per paired female in the presence of a competitor in simultaneous infections. Overall total reproductive success was, however, similar between the two species under conditions of direct competition due to the greater initial infectivity ofS. mansoniin comparison toS. rodhaini. Inter-specific competition was also implicated as increased parasite virulence to the host. The potential effects of such interactions on parasite and host ecology and evolution in nature are discussed.