bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of polyvinylidene fluoride on nonisothermal crystallization behavior of polyoxymethylene
Authors: Ding Qiong , Dai Wen‐Li , Zhang Ping
Published: November 2007

The effect of polyvinylidene fluoride (PVDF) on the crystallization behavior of polyoxymethylene (POM) was investigated using polarized light microscopy, wide angle X‐ray diffraction, and differential scanning calorimetry. From these results, it is seen that with the addition of PVDF, the spherulitic size of POM was greatly decreased, but no change occurred for the hexagonal system of POM crystal. Three methods, namely, Avrami, Ozawa, and Mo, were carried out to analyze the nonisothermal crystallization data. The results showed that the PVDF dispersed in POM acted as the heterogenous nuclei and accelerated the rate of nucleation, but hindered the crystal growth rate of POM which can be seen from the activation energy of pure POM and POM/PVDF blend. POLYM. ENG. SCI., 47:2034–2040, 2007. © 2007 Society of Plastics Engineers
Effect of fill factor and validation of characterizing the degree of mixing in polymer nanocomposites
Authors: Kim Dongsik , Lee Jun S. , Barry Carol M.F. , Mead Joey L.
Published: November 2007

Polymer nanocomposites have been studied extensively, but few references mention the importance of processing and how to characterize the degree of mixing. In this work, we report the influence of fill factor on the degree of mixing and thermal properties for a nanocomposite system consisting of alumina nanoparticles in polyethylene terephthalate (PET) prepared in a batch mixer. The degree of mixing for the resultant polymeric nanocomposites was quantified by three different techniques; TEM particle density, Morisita's index, and skewness. All of these methods quantify the degree of mixing based on the number of the particles in selected areas of TEM images using image analysis software. TEM particle density and skewness gave similar results, with a maximum in the degree of mixing around a fill factor of 0.70, while Morisita's index displayed a constant increase in degree of mixing with increasing fill factor. Tg was depressed by the filler and with increasing degree of mixing. The depression of Tg in the composite was maximized at a fill factor of 0.70, confirming that the analysis of TEM particle density and skewness are valid techniques to assess the degree of mixing. POLYM. ENG. SCI., 47:2049–2056, 2007. © 2007 Society of Plastics Engineers
Exploitation of electric field in controlling of nanofiber spinning process
Authors: Heikkilä Pirjo , Söderlund Lasse , Uusimäki Jari , Kettunen Lauri , Harlin Ali
Published: November 2007

Nanofibers can be prepared from a polymer solution utilizing electrospinning, a method exploiting an electrostatic field. In this work the electric field of the electrospinning process was modeled for better understanding and controllability of the fiber deposition in the electrospinning process. The model of the electric field was compared with experimental observations. The model of the electric field explained many phenomena in electrospinning, but did not provide an exclusive control tool for the process. POLYM. ENG. SCI., 47:2065–2074, 2007. © 2007 Society of Plastics Engineers
Shrinkage behavior and mechanical performances of injection molded polypropylene/talc composites
Authors: Shelesh‐Nezhad K. , Taghizadeh A.
Published: November 2007

In this research, the influences of adding talc mineral particles of 10 μm particle size on the shrinkage and the mechanical properties of injection molded polypropylene (PP)/talc composites were investigated. PP has a crystalline molecular structure and hence it possesses nonisotropic shrinkage along and across the flow directions. Addition of the talc mineral filler to PP induced an isotropic shrinkage in the molded part because of the nonisotropic shape of talc particles. The results of experiments indicated that the maximum flexural strength, maximum impact strength, and isotropic shrinkage were achieved by adding 10, 20, and 30 by weight percent of talc respectively. By incorporating of 10 wt% of talc particles into the PP matrix, the tensile strength was hardly affected but the occurrence of cold drawing phenomena in the tensile test was hindered considerably. The flake‐shape structure of talc filler played an important role in determining the molded part shrinkage and mechanical properties. POLYM. ENG. SCI., 47:2124–2128, 2007. © 2007 Society of Plastics Engineers
Thermolyzable polymer networks and star polymers containing a novel, compact, degradable acylal‐based dimethacrylate cross‐linker: Synthesis, characterization, and thermolysis
Authors: Themistou Efrosyni , Kanari Amelia , Patrickios Costas S.
Published: November 2007

A compact, cleavable acylal dimethacrylate cross‐linker, 1,1‐ethylenediol dimethacrylate (EDDMA), was synthesized from the anhydrous iron(III) chloride‐catalyzed reaction between methacrylic anhydride and acetaldehyde. The ability of EDDMA to act as cross‐linker was demonstrated by using it for the preparation of one neat cross‐linker network, four star polymers of methyl methacrylate (MMA), and four randomly cross‐linked MMA polymer networks using group transfer polymerization (GTP). For comparison, the corresponding polymer structures based on the commercially available ethylene glycol dimethacrylate (EGDMA) cross‐linker (isomer of EDDMA) were also prepared via GTP. The number of arms of the EDDMA‐based star polymers was lower than that of the corresponding EGDMA polymers, whereas the degrees of swelling in tetrahydrofuran of the EDDMA‐based MMA networks were higher than those of their EGDMA‐based counterparts. Although none of the EDDMA‐containing polymers could be cleanly hydrolyzed under basic or acidic conditions, they could be thermolyzed at 200 °C within 1 day giving lower molecular weight products. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5811–5823, 2007
Preparation of the amphiphilic macro‐rings of poly(ethylene oxide) with multi‐polystyrene lateral chains and their extraction for dyes
Authors: Pang Xinchang , Wang Guowei , Jia Zhongfan , Liu Chao , Huang Junlian
Published: November 2007

A novel method for synthesis of amphiphilic macrocyclic graft copolymers with multi‐polystyrene lateral chains is suggested, by combination of anionic ring‐open polymerization (AROP) with atom transfer radical polymerization (ATRP). The anionic ring‐opening copolymerization of ethylene oxide (EO) and ethoxyethyl glycidyl ether (EEGE) was carried out first using triethylene glycol and diphenylmethylpotassium (DPMK) as coinitiators; the monomer reactivity ratio of them are r1(EO) = 1.20 ± 0.01 and r2(EEGE) = 0.76 ± 0.02 respectively. The obtained linear well‐defined α,ω‐dihydroxyl poly(ethylene oxide) with pendant protected hydroxylmethyls (l‐poly(EO‐co‐EEGE)) was cyclized by reaction with tosyl chloride (TsCl) in the presence of solid KOH. The crude cyclized product containing the extended linear chain polymer was hydrolyzed and then purified by treat with α‐CD. The pure cyclic copolymer with multipendant hydroxymethyls [c‐poly(EO‐co‐Gly)] was esterified by reaction with 2‐bromoisobutyryl bromide, and then used as macroinitiators to initiate polymerization of styrene (St), and a series of amphiphilic macrocyclic grafted copolymers composed of a hydrophilic PEO as ring and hydrophobic polystyrene as side chains (c‐PEO‐g‐PS) were obtained. The intermediates and final products were characterized by GPC, NMR and MALDI‐TOF in detail. The experimental results confirmed that c‐PEO‐g‐PS shows stronger conjugation ability with the dyes than the corresponding comb‐PEO‐g‐PS. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5824–5837, 2007
Mechanisms of n‐butanol formation in butyl acrylate latexes
Authors: Goikoetxea Monika , Barandiaran María J. , Asua José M.
Published: November 2007

The mechanisms involved in the formation of n‐butanol during the synthesis of butyl acrylate containing latices were investigated. The experimental results showed that neither the hydrolysis of butyl acrylate nor of the ester bond in the butyl acrylate segments of the polymer played a major role in the formation of n‐butanol, which was mainly generated from the polymer backbone, by transfer reactions to polymer chain followed by cyclization. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5838–5846, 2007
Influence of stereoerrors on the formation of helices during early stage crystallization of isotactic polyproyplene
Authors: Chen Xiaofeng , Ozisik Rahmi , Kumar Sanat K. , Choi Phillip
Published: November 2007

Coarse‐grained, on‐lattice Monte Carlo simulations are performed to investigate the role of stereotacticity defects along an isotactic polypropylene chain on the formation of 31‐helices, which form the basic crystalline order within the chain. For this reason, systems with various stereoerror configurations are studied and are compared to neat isotactic polypropylene. All systems are equilibrated above the melting temperature and are cooled to lower temperatures in a stepwise manner, making sure each system is equilibrated at every temperature. Results indicate that chain ends have the lowest probability of being found in helices. Addition of a single stereoerror (mrm) decreases the probability of five repeat units' participation in helices (the repeat unit that contains the stereoerror and two nearest repeat units on both sides). The probability profile becomes more complicated when the number of stereoerrors increases, however, the results indicate that the effects of many stereoerrors can be explained by a simple addition of the effect of each stereoerror considered individually. The results also indicate that the presence of even a single stereoerror eliminates (within the temperature range studied) the transition to longer, more stable helices observed in neat isotactic polypropylene. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3349–3360, 2007
Conformation of a polymer chain in explicit solvent: A solvation potential approach
Authors: Taylor Mark P. , Ichida Sayuri
Published: November 2007

In much of the theoretical work on polymers in dilute solution the effects of solvent are treated in an implicit fashion: thus one studies an isolated chain interacting via an effective site–site potential. Although a formally exact mapping is possible between the chain‐in‐solvent system and a corresponding isolated effective‐potential‐chain, this mapping involves a many‐site solvation potential which is not practical to compute. Thus, one generally resorts to a two‐site potential approximation. In this article we test the validity of this two‐site approximation for a short hard‐sphere (HS) n‐mer chain (n ≤ 5) in a HS solvent. This test involves computing a set of “exact” site–site solvation potentials for an isolated chain. These potentials are shown to reproduce the conformation of a chain in explicit solvent. We make use of these exact short‐chain results (combining them with the solvent potential of mean force) to construct approximate two‐site solvation potentials for long chains. Monte Carlo simulations have been performed for HS chain‐in‐solvent systems and for the corresponding isolated effective‐potential n‐mer chain with n ≤ 50. These simulations show that our solvation potentials provide a quantitatively accurate description of the conformation of a HS chain in explicit (hard sphere) solvent. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3319–3326, 2007
Dendritic growth of poly(ε‐caprolactone) crystals from compatible blends with poly(t‐butyl acrylate) at the air/water interface
Authors: Li Bingbing , Marand Hervé , Esker Alan R.
Published: November 2007

Thermodynamic analyses of surface pressure‐area (Π‐A) isotherms and Brewster angle microscopy (BAM) reveal that poly(ε‐caprolactone) (PCL) with a weight average molar mass of Mw = 10 kg mol−1 and polydispersity index of Mw/Mn = 1.25 and poly(t‐butyl acrylate) (PtBA, Mw = 25.7 kg mol−1; Mw/Mn = 1.07) form compatible blends as Langmuir films below the dynamic collapse transition for PCL at Π = 11 mN m−1. For PCL‐rich blends, in situ BAM studies reveal growth of PCL crystals for compression past the PCL collapse transition. PCL crystals grown in the plateau regime of the Π‐A isotherm exhibit a dendritic morphology presumably resulting from the rejection of PtBA from the growing PCL crystals and hindered diffusion of PCL from the surrounding monolayer to the crystal growth fronts. The ability to transfer the PCL dendrites as Langmuir–Schaefer films onto silicon substrates spincoated with a polystyrene layer facilitates detailed morphological characterization by optical and atomic force microscopy (AFM). AFM reveals that the dendritic branching occurs along the {100} and {110} sector boundaries and is essentially independent of composition. AFM also reveals that the average thickness of PCL dendrites formed at room temperature (22.5 °C), ∼7–8 nm, is comparable with that of PCL crystals grown from single‐component PCL Langmuir films and spincoated thin films. In contrast, for PtBA‐rich blend films PCL crystallization is suppressed. These findings establish PCL blends as an ideal system for exploring the interplay between chain diffusion and crystal growth in a two‐dimensional confined geometry. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3300–3318, 2007
Mechanical hole burning spectroscopy in an SIS tri‐block copolymer
Authors: Qin Qian , Shi Xiangfu , McKenna Gregory B.
Published: November 2007

We have previously developed a mechanical hole burning spectroscopy (MSHB) technique that promises to be a powerful tool for the investigation of dynamic heterogeneity of polymeric materials. This is because, unlike its dielectric analogue, MSHB can be used to characterize materials having a weak dielectric response, a particular feature of polymeric materials. However, while both mechanical and dielectric hole burning show behaviors that are consistent with dynamic heterogeneity in the materials, it is still unclear what the relationship between the hole properties, for example, frequency and amplitude, and the actual nature of the heterogeneity and particularly the length scale being probed. Here, we provide first evidence that a known length scale can be probed by the MSHB method by using a tri‐block copolymer as a “calibration” sample. The heterogeneity of a styrene‐isoprene‐styrene copolymer was investigated in the vicinity of the order‐disorder transition temperature (ODT). It was found that the amplitudes of the mechanical holes gradually decrease as the order‐disorder transition is traversed from the region with ordered structures. In the disordered state of the block copolymer, no apparent mechanical holes were detected. In contrast, mechanical holes were burned in the heterogeneous region and the hole amplitude increased as the depth into the ordered structure increased. Hence, the MSHB technique provides a qualitative correlation between the amplitude of the burned holes and the corresponding heterogeneity. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3277–3284, 2007
Control of the block copolymer morphology in templated epoxy thermosets
Authors: Hermel‐Davidock Theresa J. , Tang H. Sean , Murray Daniel J. , Hahn Stephen F.
Published: November 2007

It has been found that by the addition of low concentrations of an amphiphilic block copolymer to an epoxy resin, novel disordered morphologies can be formed and preserved through curing. This article will focus on characterizing the influence of the block copolymer and casting solvent on the templated morphology achieved in the thermoset sample. The ultimate goal of this work is to determine the parameters that would control the microphase morphology produced. Epoxy resins blended with a series of amphiphilic block copolymers based on hydrogenated polyisoprene (polyethylene‐alt‐propylene or PEP) and polyethylene oxide (PEO), specifically, were investigated. In this article, the cure‐induced order–order phase transition from the spherical to wormlike micelle morphology will also be discussed. It is proposed that the formation of the wormlike micelle structure from the spherical micelle structure is similar to the phase transition behavior that occurs in dilute block copolymer solutions as a function of the influence of the solvent on micelle morphology. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3338–3348, 2007
An efficient conformational sampling method for homology modeling
Authors: Han Rongsheng , Leo‐Macias Alejandra , Zerbino Daniel , Bastolla Ugo , Contreras‐Moreira Bruno , Ortiz Angel R.
Published: November 2007

The structural refinement of protein models is a challenging problem in protein structure prediction (Moult et al., Proteins 2003;53(Suppl 6):334–339). Most attempts to refine comparative models lead to degradation rather than improvement in model quality, so most current comparative modeling procedures omit the refinement step. However, it has been shown that even in the absence of alignment errors and using optimal templates, methods based on a single template have intrinsic limitations, and that refinement is needed to improve model accuracy. It is thought that failure of current methods originates on one hand from the inaccuracy of the effective free energy functions adopted, which do not represent properly the energetic balance in the native state, and on the other hand from the difficulty to sample the high dimensional and rugged free energy landscape of protein folding, in the search for the global minimum. Here, we address this second issue. We define the evolutionary and vibrational armonics subspace (EVA), a reduced sampling subspace that consists of a combination of evolutionarily favored directions, defined by the principal components of the structural variation within a homologous family, plus topologically favored directions, derived from the low frequency normal modes of the vibrational dynamics, up to 50 dimensions. This subspace is accurate enough so that the cores of most proteins can be represented within 1 Å accuracy, and reduced enough so that Replica Exchange Monte Carlo (Hukushima and Nemoto, J Phys Soc Jpn 1996;65:1604–1608; Hukushima et al., Int J Mod Phys C: Phys Comput 1996;7:337–344; Mitsutake et al., J Chem Phys 2003;118:6664–6675; Mitsutake et al., J Chem Phys 2003;118:6676–6688) (REMC) can be applied. REMC is one of the best sampling methods currently available, but its applicability is restricted to spaces of small dimensionality. We show that the combination of the EVA subspace and REMC can essentially solve the optimization problem for backbone atoms in the reduced sampling subspace, even for rather rugged free energy landscapes. Applications and limitations of this methodology are finally discussed. Proteins 2008. © 2007 Wiley‐Liss, Inc.
Comparison of vertebrate and invertebrate CLIC proteins: The crystal structures of Caenorhabditis elegans EXC‐4 and Drosophila melanogaster DmCLIC
Authors: Littler Dene R. , Harrop Stephen J. , Brown Louise J. , Pankhurst Greg J. , Mynott Andrew V. , Luciani Paolo , Mandyam Ramya A. , Mazzanti Michele , Tanda Soichi , Berryman Mark A. , Breit Samuel N. , Curmi Paul M. G.
Published: November 2007

The crystal structures of two CLIC family members DmCLIC and EXC‐4 from the invertebrates Drosophila melanogaster and Caenorhabditis elegans, respectively, have been determined. The proteins adopt a glutathione S‐transferase (GST) fold. The structures are highly homologous to each other and more closely related to the known structures of the human CLIC1 and CLIC4 than to GSTs. The invertebrate CLICs show several unique features including an elongated C‐terminal extension and a divalent metal binding site. The latter appears to alter the ancestral glutathione binding site, and thus, the invertebrate CLICs are unlikely to bind glutathione in the same manner as the GST proteins. Purified recombinant DmCLIC and EXC‐4 both bind to lipid bilayers and can form ion channels in artificial lipid bilayers, albeit at low pH. EXC‐4 differs from other CLIC proteins in that the conserved redox‐active cysteine at the N‐terminus of helix 1 is replaced by an aspartic acid residue. Other key distinguishing features of EXC‐4 include the fact that it binds to artificial bilayers at neutral pH and this binding is not sensitive to oxidation. These differences with other CLIC family members are likely to be due to the substitution of the conserved cysteine by aspartic acid. Proteins 2008. © 2007 Wiley‐Liss, Inc.
Characterization of local geometry of protein surfaces with the visibility criterion
Authors: Li Bin , Turuvekere Srinivasan , Agrawal Manish , La David , Ramani Karthik , Kihara Daisuke
Published: November 2007

Experimentally determined protein tertiary structures are rapidly accumulating in a database, partly due to the structural genomics projects. Included are proteins of unknown function, whose function has not been investigated by experiments and was not able to be predicted by conventional sequence‐based search. Those uncharacterized protein structures highlight the urgent need of computational methods for annotating proteins from tertiary structures, which include function annotation methods through characterizing protein local surfaces. Toward structure‐based protein annotation, we have developed VisGrid algorithm that uses the visibility criterion to characterize local geometric features of protein surfaces. Unlike existing methods, which only concerns identifying pockets that could be potential ligand‐binding sites in proteins, VisGrid is also aimed to identify large protrusions, hollows, and flat regions, which can characterize geometric features of a protein structure. The visibility used in VisGrid is defined as the fraction of visible directions from a target position on a protein surface. A pocket or a hollow is recognized as a cluster of positions with a small visibility. A large protrusion in a protein structure is recognized as a pocket in the negative image of the structure. VisGrid correctly identified 95.0% of ligand‐binding sites as one of the three largest pockets in 5616 benchmark proteins. To examine how natural flexibility of proteins affects pocket identification, VisGrid was tested on distorted structures by molecular dynamics simulation. Sensitivity decreased ∼20% for structures of a root mean square deviation of 2.0 Å to the original crystal structure, but specificity was not much affected. Because of its intuitiveness and simplicity, the visibility criterion will lay the foundation for characterization and function annotation of local shape of proteins. Proteins 2008. © 2007 Wiley‐Liss, Inc.
Structural analysis of protein dynamics by MD simulations and NMR spin‐relaxation
Authors: Trbovic Nikola , Kim Byungchan , Friesner Richard A. , Palmer Arthur G.
Published: November 2007

Molecular dynamics (MD) simulations and nuclear magnetic resonance spin‐relaxation measurements provide detailed insights into ps‐ns structural dynamics of proteins. An analysis of discrepancies between the two methods is presented for the B3 immunoglobulin‐binding domain of streptococcal protein G. MD simulations using three MD force fields (OPLS‐AA, AMBER ff99SB, and AMBER ff03) overestimate the flexibility of backbone NH vectors at the borders of secondary structure and in loops when compared with experimentally determined backbone amide generalized order parameters (Hall and Fushman, J Am Chem Soc 2006; 12:7855–7870). Comparison with a previous study of residual dipolar coupling constants (Bouvignies et al., Proc Natl Acad Sci USA 2005;102:13885–13890) indicates that slower timescale motions do not account for the discrepancies. Structural analysis reveals that relative imbalance between the description of hydrogen bonding and other terms of modern force fields may be responsible for disagreement. Proteins 2008. © 2007 Wiley‐Liss, Inc.
Exploring the molecular basis of heme coordination in human neuroglobin
Authors: Nadra Alejandro D. , Martí Marcelo A. , Pesce Alessandra , Bolognesi Martino , Estrin Darío A.
Published: November 2007

Neuroglobin (Ngb), a recently discovered ancient heme protein, presents the typical globin fold and is around 20% identical to myoglobin (Mb). In contrast with Mb, however, its heme is hexacoordinated (6c). It is expressed in the nervous system and has been the subject of numerous investigations in the last years, but its function is still unclear. The proposed roles include oxygen transport, reactive oxygen species (ROS) detoxification, hypoxia protection, and redox state sensing. All proposed functions require distal histidine dissociation from the heme to yield a reactive iron. With the aim of understanding the 6c to 5c transition, we have performed molecular dynamics simulations for ferrous Ngb in the 6c, 5c, and oxy states. We also computed free energy profiles associated with the transition employing an advanced sampling technique. Finally, we studied the effect of the redox state of CysCD7 and CysD5, which are known to form a disulfide bridge. Our results show that protein oxidation promotes a stabilization of the pentacoordinated species, thus favoring the protein to adopt the more reactive state and supporting the existence of a molecular mechanism whereby O2 would be released under hypoxic conditions, thereby suggesting an O2 storage function for Ngb. Taken together, our results provide structural information not available experimentally which may shed light on the protein proposed functions, particularly as a redox sensor. Proteins 2008. © 2007 Wiley‐Liss, Inc.
Fitting models for the joint action of two drugs using SAS(R)
Authors: Whitehead Anne , Whitehead John , Todd Susan , Zhou Yinghui , Smith Michael K
Published: November 2007

Combinations of drugs are increasingly being used for a wide variety of diseases and conditions. A pre‐clinical study may allow the investigation of the response at a large number of dose combinations. In determining the response to a drug combination, interest may lie in seeking evidence of ‘synergism’, in which the joint action is greater than the actions of the individual drugs, or of ‘antagonism’, in which it is less. Two well‐known response surface models representing no interaction are Loewe additivity and Bliss independence, and Loewe or Bliss synergism or antagonism is defined relative to these. We illustrate an approach to fitting these models for the case in which the marginal single drug dose–response relationships are represented by four‐parameter logistic curves with common upper and lower limits, and where the response variable is normally distributed with a common variance about the dose–response curve. When the dose–response curves are not parallel, the relative potency of the two drugs varies according to the magnitude of the desired effect and the models for Loewe additivity and synergism/antagonism cannot be explicitly expressed. We present an iterative approach to fitting these models without the assumption of parallel dose–response curves. A goodness‐of‐fit test based on residuals is also described. Implementation using the SAS NLIN procedure is illustrated using data from a pre‐clinical study. Copyright © 2007 John Wiley & Sons, Ltd.
The even‐electron rule in electrospray mass spectra of pesticides
Authors: Thurman E. Michael , Ferrer Imma , Pozo Oscar J. , Sancho Juan V. , Hernandez Felix
Published: November 2007

A study of the fragmentation and ion formation of three major families of pesticides (including herbicides, insecticides, and fungicides) by liquid chromatography/time‐of‐flight mass spectrometry (LC/TOF‐MS) and liquid chromatography/quadrupole time‐of‐flight mass spectrometry (LC/Q‐TOF‐MS) was carried out using positive electrospray ionization (ESI) and the results compared with those by gas chromatography (GC)/TOF‐MS with electron ionization (EI) in order to test the validity of the even‐electron rule in electrospray ionization. First, the majority of the fragmenta ions by positive ion ESI were even electron (EE) ions (93% of the fragment ions). Secondly, the formation of odd‐electron (OE) fragment ions was greater with EI, where the fragment ions were present in a ratio of approximately 1:2 (35% OE ions and 65% EE ions). Thirdly, in‐source collision‐induced dissociation (CID) fragmentation by LC/TOF‐MS and CID fragmentation in the collision cell by LC/Q‐TOF‐MS/MS resulted in 95% of the fragment ions being identical between the two types of fragmentation. As ESI in the positive ion mode yields an EE precursor ion (normally a protonated molecule), this commonly leads to EE fragment ions by elimination of molecules – a process called the even‐electron rule. Neutral radical losses were less common in ESI but were common in the EI spectra of the same compounds. The structures that did lead to OE ions in ESI (exceptions to the even‐electron rule ∼7% of all ESI ions) favored electronegative radical losses in approximately the following order: ·SO2CH3, ·NO2, ·CH3, ·Cl, ·SCH3, ·CH2CH, and ·OH. Copyright © 2007 John Wiley & Sons, Ltd.
How many dimensions does sustainable development have?
Authors: Pawłowski Artur
Published: November 2007

There is only a scant possibility of today's environmental problems being solved solely by technical means, with no account being taken of the social or economic aspects. Thus, three generally recognized dimensions of sustainable development have been devised: ecological, social and economic. However, the basis for them is moral reflection regarding humankind's responsibility for nature. Is this all? Perhaps we should also include technical, legal and political dimensions. All of them are important and all of them are characterized in this paper. Since they are connected with one another, examples of the degree to which they can overlap are also discussed. Copyright © 2007 John Wiley & Sons, Ltd and ERP Environment.
Evaluating a surrogate endpoint at three levels, with application to vaccine development
Authors: Gilbert Peter B. , Qin Li , Self Steven G.
Published: November 2007

Identification of an immune response to vaccination that reliably predicts protection from clinically significant infection, i.e. an immunological surrogate endpoint, is a primary goal of vaccine research. Using this problem of evaluating an immunological surrogate as an illustration, we describe a hierarchy of three criteria for a valid surrogate endpoint and statistical analysis frameworks for evaluating them. Based on a placebo‐controlled vaccine efficacy trial, the first level entails assessing the correlation of an immune response with a study endpoint in the study groups, and the second level entails evaluating an immune response as a surrogate for the study endpoint that can be used for predicting vaccine efficacy for a setting similar to that of the vaccine trial. We show that baseline covariates, innovative study design, and a potential outcomes formulation can be helpful for this assessment. The third level entails validation of a surrogate endpoint via meta‐analysis, where the goal is to evaluate how well the immune response can be used to predict vaccine efficacy for new settings (building bridges). A simulated vaccine trial and two example vaccine trials are presented, one supporting that certain anti‐influenza antibody levels are an excellent surrogate for influenza illness and another supporting that certain anti‐HIV antibody levels are not useful as a surrogate for HIV infection. Copyright © 2007 John Wiley & Sons, Ltd.
Predicting and measuring alliance performance: a multidimensional analysis
Authors: Lunnan Randi , Haugland Sven A.
Published: November 2007

The strategic alliance literature demonstrates that alliances create value for the partners, but also that many alliances fall short of expectations. This study addresses the complex issue of alliance performance. We follow 100 contractual alliances over a 5‐year period, and study their performance in terms of abrupt termination, short‐term performance, and long‐term performance. The results indicate that alliances that are considered strategically important are less likely to be abruptly terminated. We also find that newly established alliances have a higher termination rate than older alliances. Short‐term performance is primarily affected by access to complementary and strategically important resources, whereas long‐term performance is related to specific investments in human capital combined with the partners' ability to develop and expand alliance activities over time. Copyright © 2007 John Wiley & Sons, Ltd.
Impacts of Organizational Culture and Personality Traits on Decision‐making in Technical Organizations
Authors: Briggs Clark , Little Patrick
Published: November 2007

Technical organizations in industries such as aerospace or automotive regularly make major decisions regarding software and other tools to support mission‐critical activities. These decisions take place at the enterprise level where functional departments must work together in ways not common before. Usually, these are high‐impact, tension‐filled decision activities that have long term effects. The organization needs a successful decision that stands the test of implementation and a sustained period of effective operation. The processes used in such cases generally follow analytical decision methods aimed at maximizing objectives. Understanding the characteristics of the organization, including the culture and the affected parties, in addition to the technical aspects of the decision may significantly increase the likelihood of success. © 2007 Wiley Periodicals, Inc. Syst Eng
Profiles of freshman physics students' views on the nature of science
Authors: Ibrahim Bashirah , Buffler Andy , Lubben Fred
Published: November 2007

The views on various aspects of the nature of science (NOS) of 179 novice undergraduate physics students were investigated using six open‐ended, written probes. These views were consolidated within compact NOS “profiles,” which were designed based on the students' responses to the probes. These profiles may be understood as sets of key descriptors, which represented the variation in the views of individual students in a succinct way. The views of 86% of the sample were found to be represented by four profiles, each containing five descriptors. The consequences for the teaching and learning of tertiary science, and advantages for linking NOS views to other research observables were explored. © 2007 Wiley Periodicals, Inc. J Res Sci Teach 46: 248–264, 2009
Umbilical artery half peak systolic velocity deceleration time throughout pregnancy and its role in fetuses with bradycardia
Authors: Bustos J. C. , Paublo M. , Ramirez P. , Sepulveda W.
Published: November 2007

Objectives

To describe a new technique for Doppler waveform quantification of the fetal umbilical artery, the half peak systolic velocity (h‐PSV) deceleration time, which measures the time that it takes a single flow velocity waveform to halve its maximum systolic velocity. As this measurement is independent of fetal heart rate, its role in the evaluation of placental vascular resistance in fetuses with bradycardia was also explored.

Methods

The umbilical artery impedance indices and the h‐PSV deceleration time were measured in 532 normal singleton fetuses from 17 to 41 weeks of gestation. A nomogram was established and its usefulness in assessing fetuses with bradycardia was evaluated.

Results

The relationship between umbilical artery h‐PSV deceleration time and gestational age was best described by a linear formula (y = 6.5523x + 12.41; R2 = 0.6346), h‐PSV deceleration time increasing by 6.6 ms per week. The correlation coefficients for the 95th, 50th and 5th centiles were 0.97, 0.98 and 0.98, respectively. Measurement of h‐PSV deceleration time was reproducible, with interobserver and intraobserver variabilities of 10.7% and 7.4%, respectively. Among fetuses with bradycardia (n = 7), the h‐PSV deceleration time was above the 5th centile in all cases, suggesting normal placental function in spite of abnormally increased impedance indices obtained with traditional Doppler indices in six.

Conclusions

The h‐PSV deceleration time increases linearly during the second and third trimesters of pregnancy. As its measurement is reproducible and independent of heart rate, it may be useful in the assessment of well‐being in fetuses with bradycardia. Copyright © 2007 ISUOG. Published by John Wiley & Sons, Ltd.
Influence of GaAs Substrate Orientation on InAs Quantum Dots: Surface Morphology, Critical Thickness, and Optical Properties
Authors: Liang BL , Wang Zh M , Sablon KA , Mazur Yu I , Salamo GJ
Published: November 2007

InAs/GaAs heterostructures have been simultaneously grown by molecular beam epitaxy on GaAs (100), GaAs (100) with a 2° misorientation angle towards [01−1], and GaAs (n 11)B (n = 9, 7, 5) substrates. While the substrate misorientation angle increased from 0° to 15.8°, a clear evolution from quantum dots to quantum well was evident by the surface morphology, the photoluminescence, and the time-resolved photoluminescence, respectively. This evolution revealed an increased critical thickness and a delayed formation of InAs quantum dots as the surface orientation departed from GaAs (100), which was explained by the thermal-equilibrium model due to the less efficient of strain relaxation on misoriented substrate surfaces.
Dietary Structured Lipids and Phytosteryl Esters: Blood Lipids and Cardiovascular Status in Spontaneously Hypertensive Rats
Authors: Kim Byung Hee , Sandock Kevin D. , Robertson Tom P. , Lewis Stephen J. , Akoh Casimir C.
Published: November 2007

This study examined the dietary effects of enzymatically modified sesame oil with caprylic acid (structured lipids, SL) and phytosteryl esters (PE) on blood lipid profiles and cardiovascular parameters of spontaneously hypertensive rats (SHR) fed high‐fat and high‐cholesterol (HFHC) diets. The dietary groups were: normal diet (control), sesame oil (SO), SL, SO fortified with PE (SOP), and SL fortified with PE (SLP). After 9 weeks of feeding, the body weights, liver weights, and liver weight/body weight ratios in all HFHC‐fed groups were higher than controls. Plasma total and LDL cholesterol levels in all HFHC‐fed groups were similar to one another but higher than those in controls. Plasma HDL cholesterol levels in rats fed SOP and SLP were higher than those in controls or rats fed SO and SL. Plasma HDL/total cholesterol ratios in rats fed SOP and SLP were similar to those in controls and were higher than those in rats fed SO and SL. There was no difference in plasma lipid profiles between rats fed SO and SL. Arterial blood pressures (BP) in conscious HFHC‐fed rats were similar to those in controls whereas heart rates (HR) in all HFHC‐fed groups were similar to one another but were higher than that in controls. These findings demonstrate that (1) the dietary effects of SL on plasma lipid profiles and resting BP and HR are similar to those of SO, (2) PE had positive effects on plasma lipid profiles, and (3) 9‐week intake of SL and PE did not have pronounced effects on resting BP but induced tachycardia in SHR.
Flaxseed Treatments to Reduce Biohydrogenation of α‐Linolenic Acid by Rumen Microbes in Cattle
Authors: Kronberg S. L. , Scholljegerdes E. J. , Barceló‐Coblijn G. , Murphy E. J.
Published: November 2007

Enrichment of beef muscle with n‐3 fatty acids (FA) is one means to introduce these FA into the diet, but ruminal biohydrogenation limits their bioavailability. To address this problem, we evaluated the ability of condensed tannin (quebracho), in the presence or absence of casein, to protect 18:3n‐3 in flaxseed from hydrogenation by ruminal microbes in cattle using an in vitro fermentation approach coupled with evaluation in cattle in vivo. Treated and untreated flaxseed was incubated with bovine rumen fluid for 0 and 24 h. With tannin treated flaxseed, hydrogenation of 18:3n‐3 was limited to only 13% over 24 h compared to 43% for untreated flaxseed, while addition of casein to the tannin added no additional protection. To determine if a similar level of protection would occur in vivo, we used two groups of five steers fed either a grain‐based or forage‐based diet. Five steers were given a grain‐based diet during the trial and were fed either ground flaxseed or tannin treated flaxseed for 15 days prior to blood collection for plasma lipid fatty acid analysis. The forage fed steers followed the same regimen. Ingestion of tannin‐treated flaxseed did not increase 18:3n‐3 and 20:5n‐3 in plasma neutral lipids as compared to non‐treated flaxseed. Thus, we demonstrated that treating ground flaxseed with quebracho tannin is not useful for increasing 18:3n‐3 in the neutral lipid of bovine blood plasma, and suggest caution when interpreting results from in vitro trials that test potential treatments for protecting fatty acids from hydrogenation by ruminal microbes.
Effects of milk fermented byLactobacillusgasseriSBT2055 on adipocyte size in rats
Authors: Sato Masao , Uzu Kazunori , Yoshida Takeshi , Hamad Essam M. , Kawakami Hiroshi , Matsuyama Hiroaki , Abd El-Gawad Ibrahim A. , Imaizumi Katsumi
Published: November 2007

Despite adequate scientific evidence of the potential benefits of probiotics to human health or disease prevention, their contribution to the growth of adipose tissue remains to be established. Four-week-old male Sprague-Dawley rats were fed a diet containing skim milk (control diet) or skim milk fermented byLactobacillus gasseriSBT2055 (LGSP diet) for 4 weeks. Their body weight gain, adipose tissue weight, adipocyte size distribution profile, blood and hepatic lipids, and serum leptin, glucose and adiponectin levels were determined. There was a significant reduction in average adipocyte size in mesenteric white adipose tissue (P = 0·004). Moreover, the rats fed the LGSP diet displayed greater numbers of small adipocytes from mesenteric and retroperitoneal adipose tissues than did those on the control diet. Whereas adiponectin concentrations did not differ between the groups, serum leptin concentrations were decreased to 32 % in the LGSP diet group compared with the control group. Concentrations of serum glucose and lipids, and liver lipids, except for the liver TAG level, were similar in the two groups. These results indicate a possible role for a fermented milk product in the regulation of adipose tissue growth.
Sex differences in fat storage, fat metabolism, and the health risks from obesity: possible evolutionary origins
Authors: Power Michael L. , Schulkin Jay
Published: November 2007

Human beings are susceptible to sustained weight gain in the modern environment. Although both men and women can get fat, they get fat in different ways, and suffer different consequences. We review differences between men and women in the incidence of obesity, fat deposition patterns, fat metabolism, and the health consequences of obesity, and examine potential evolutionary explanations for these differences. Women generally have a larger proportion of body mass as fat, and are more likely to deposit fat subcutaneously and on their lower extremities; men are more likely to deposit fat in the abdominal region. Excess adipose tissue in the abdominal region, especially visceral fat, is associated with more health risks. Women have higher rates of reuptake of NEFA into adipose tissue; however, they also have higher rates of fat oxidation during prolonged exercise. Oestrogen appears to underlie many of these differences. Women bear higher nutrient costs during reproduction. Fat and fertility are linked in women, through leptin. Low leptin levels reduce fertility. Ovarian function of adult women is associated with their fatness at birth. In our evolutionary past food insecurity was a frequent occurrence. Women would have benefited from an increased ability to store fat in easily metabolisable depots. We suggest that the pattern of central obesity, more commonly seen in men, is not adaptive, but rather reflects the genetic drift hypothesis of human susceptibility to obesity. Female obesity, with excess adiposity in the lower extremities, reflects an exaggeration of an adaptation for female reproductive success.
Flavanol monomer-induced changes to the human faecal microflora
Authors: Tzounis Xenofon , Vulevic Jelena , Kuhnle Gunter G. C. , George Trevor , Leonczak Jadwiga , Gibson Glenn R. , Kwik-Uribe Catherine , Spencer Jeremy P. E.
Published: November 2007

We have investigated the bacterial-dependent metabolism of ( − )-epicatechin and (+)-catechin using a pH-controlled, stirred, batch-culture fermentation system reflective of the distal region of the human large intestine. Incubation of ( − )-epicatechin or (+)-catechin (150 mg/l or 1000 mg/l) with faecal bacteria, led to the generation of 5-(3′,4′-dihydroxyphenyl)-γ-valerolactone, 5-phenyl-γ-valerolactone and phenylpropionic acid. However, the formation of these metabolites from (+)-catechin required its initial conversion to (+)-epicatechin. The metabolism of both flavanols occurred in the presence of favourable carbon sources, notably sucrose and the prebiotic fructo-oligosaccharides, indicating that bacterial utilisation of flavanols also occurs when preferential energy sources are available. (+)-Catechin incubation affected the growth of select microflora, resulting in a statistically significant increase in the growth of theClostridium coccoides–Eubacterium rectalegroup,Bifidobacteriumspp. andEscherichia coli, as well as a significant inhibitory effect on the growth of theC. histolyticumgroup. In contrast, the effect of ( − )-epicatechin was less profound, only significantly increasing the growth of theC. coccoides–Eubacterium rectalegroup. These potential prebiotic effects for both (+)-catechin and ( − )-epicatechin were most notable at the lower concentration of 150 mg/l. As both ( − )-epicatechin and (+)-catechin were converted to the same metabolites, the more dramatic change in the growth of distinct microfloral populations produced by (+)-catechin incubation may be linked to the bacterial conversion of (+)-catechin to (+)-epicatechin. Together these data suggest that the consumption of flavanol-rich foods may support gut health through their ability to exert prebiotic actions.
VARIATION OF VIEW ON ENGLISH LEGAL DISTINCTIONS BETWEEN PUBLIC AND PRIVATE
Authors: Allison J. W. F.
Published: November 2007

The debate about distinguishing public law and private law has been wide-ranging and variously focused. It has contributed to a paradox (or contradiction) in legal thinking, described by Peter Cane in his contribution to Public Law in a Multi-Layered Constitution. On the one hand, Cane stresses that the distinction between public and private “seems alive and well”––manifest, inter alia, in judicial review procedure and the establishment of an Administrative Court in England, in EC law (demarcating the scope of directives with direct effect), in the provisions applicable to public authorities in the Human Rights Act 1998, in the “state action” doctrine of the US Supreme Court, and in the statutory demarcation of the Administrative Appeals Tribunal's jurisdiction in Australia. On the other hand, he stresses the extent of scholarly criticism of the distinction––that it is outmoded, descriptively inaccurate or normatively undesirable. In his view, the resolution of the paradox lies in recognition that “the supporters and the opponents of the public/private distinction are talking about different things”. He concludes that, for its opponents, as a result of institutional and functional hybridisation, “the distinction misrepresents the way power is distributed and exercised” but that, for its supporters, “it embodies an attractive normative theory of the way power ought to be distributed and its exercise controlled”. In his presentation of the paradox and its resolution, Cane thus brings together various views and distinctions––English, American and Australian––and suggests that a contrast between descriptive criticism and normative evaluation is crucial to understanding the public/private debate. By the breadth and inclusivity of his analysis, however, he also brings into question the desirability of unitary analytical treatment of various distinctions in various contexts, supported and opposed by people talking about “different things”.