bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrous Oxide Reductase
Authors: Eady Robert R , Antonyuk Svetlana V , Hasnain S Samar
Published: September 2007

(N
2
O) is a major greenhouse gas and is thought to be some 300 times more potent than CO
2
in promoting global warming due to its inert chemical nature. The difficult chemistry of N
2
O reduction to gaseous nitrogen (N
2
) in biology is catalyzed by the novel µ
4
‐sulfide‐bridged tetranuclear Cu

z

cluster of the N
2
O reductases (N
2
ORs). These enzymes, in common with cytochrome c oxidase (CCO), also contain an electron‐donating Cu
A
site. During the past five years, several structures of this enzyme, from a number of species, have emerged, providing the details of structural elements responsible for this fascinating chemistry. These aspects are discussed in the light of extensive spectroscopic and functional data, providing an up‐to‐date review from these perspectives.
Octaheme Tetrathionate Reductase
Authors: Mowat Christopher G. , Atkinson Sally J. , Reid Graeme A.
Published: September 2007

Octaheme tetrathionate reductase (OTR) fromShewanella oneidensisis a soluble cytochrome with eight covalently attached heme groups. The gene encoding the protein has been cloned and overexpressed, and characterization of the protein is ongoing. From the crystal structure it can be seen that one of the hemes displays novel ligation of the iron atom by the ɛ‐amino group of a lysine residue. This occurs despite the heme attachment being via a typical CXXCH motif. It is believed that this heme represents the active site for tetrathionate reduction, a reaction which is catalyzed efficiently by the enzyme. Recent work has also suggested a multifunctional role for OTR, with the enzyme being demonstrated to catalyze the reduction of nitrite, hydroxylamine and nitric oxide.
Cytosolic Aconitase
Authors: Volbeda Anne , Moulis Jean‐Marc , Dupuy Jérôme , Walden William , Volz Karl , Fontecilla‐Camps Juan Carlos
Published: September 2007

Cytosolic aconitases (cAcns) have the remarkable property that they can function either as an enzyme or as a messenger (m) RNA‐binding protein. In the first case they contain a [4Fe–4S] cluster that is directly involved in the catalysis of the isomerization between citrate and isocitrate via acis‐aconitate intermediate. Upon loss of the cluster the enzymatic function is lost, the protein undergoes a substantial structural rearrangement and becomes capable of recognizing, with very high affinity, the so‐called iron‐responsive elements (IREs) in mRNAs. The latter code for proteins that are either dependent on Fe or are involved in the regulation of iron levels in the cell. The nonenzymatic form of cAcn is known as iron‐regulatory protein 1 or IRP1. Here we review the most recent structural data on the two forms, cAcn and IRP1, and correlate these with their respective functional properties. In addition, a comparison is made with closely related proteins like IRP2 and mitochondrial and bacterial aconitases.
Metal ions in cyanobacterial photosystem I
Authors: Saenger Wolfram , Biesiadka Jacek , Loll Bernhard
Published: September 2007

Photosystems I (PSI) and photosystem II (PSII) are large multi‐subunit protein–cofactor complexes located in the photosynthetic thylakoid membrane and acting in series. They are fueled by sunlight, PSII oxidizing water to atmospheric O2, H+, and electrons that are delivered at the lumenal side of the membrane. The electrons are transferred to PSI where their reducing potential is increased sufficiently to finally produce reduced nicotinamide adenine dinucleotide phosphate (NADPH) at oxidized form of nicotinamide adenine dinucleotide phosphate (NADP+) reductase while the H+form a gradient across the membrane that drives adenosine triphosphate (ATP‐)synthetase and both, NADPH and ATP, convert CO2to carbohydrates in the Calvin cycle.

PSI is composed of 12 different protein subunits of which 9 are embedded in the thylakoid membrane and 3 are located on the cytoplasmic (stromal) side of the membrane. Sunlight is absorbed by a large internal antenna composed of 90 chlorophylla(Chla), and the photons are guided to the electron transfer chain (ETC) formed by two symmetry‐related branches where the ‘special pair P 700′ located close to the lumenal side of the membrane is excited and expels an electron to form the cation radical P700+. The electron is guided from P700 to the stromal side along the ETC consisting of pairs of accessory Chla, of the primary electron acceptors (Chla), of the secondary acceptors phylloquinone (PQ), to the terminal acceptors formed by three Fe4S4clusters FX, FA, FB. Since each Chlacoordinates one Mg2+, PSI harbors a plethora of Mg and Fe cations and one structural Ca2+. We describe the coordination of these cations and their function in the photosynthetic process carried out by PSI.
4‐Hydroxybutyryl‐
Co
A
Dehydratase
Authors: Martins Berta M. , Messerschmidt Albrecht , Friedrich Peter , Zhang Jin , Buckel Wolfgang
Published: September 2007

Dehydratases catalyze the cleavage of a carbon–oxygen bond yielding an unsaturated product via α,β‐elimination of water. The α‐hydrogen (p
K
 ∼ 8) to be removed as proton is activated by an adjacent electron‐withdrawing group, and the hydroxyl group leaves from the β‐position. In contrast, anaerobic organisms possess 2‐ or 4‐hydroxyacyl‐CoA dehydratases that use radicals to lower the p
K
of the unactivated β‐carbons by 26 units. An example is 4‐hydroxybutyryl‐CoA dehydratase (4‐BUDH) from

Clostridium aminobutyricum

that interconverts 4‐hydroxybutyryl‐CoA to crotonyl‐CoA. 4‐BUDH is functional as a homotetramer with two active sites per dimer and displays a distinctive active site architecture with the [4Fe–4S]
2+
cluster, coordinated by three cysteine and one histidine residues, located 7 Å from the
Re
‐side of the flavin adenine dinucleotide (FAD). Albeit requiring the cluster and an oxidized FAD for catalysis, the overall reaction occurs with no net redox change. The unexpected structural relation of 4‐BUDH with medium chain acyl‐CoA dehydrogenases suggests a radical‐based mechanism for both flavoproteins. The biochemical and structural characterization of 4‐BUDH is an important step toward a detailed study of the structural bases how enzymes regulate the generation and reactivity of radical species at a molecular level, which is a fundamental but still poorly understood problem.
Tetraheme CytochromesC3
Authors: Bento Isabel , Louro Ricardo O , Soares Cláudio M , Carrondo M Arménia
Published: September 2007

Tetraheme cytochromesc3constitute the best‐studied group among the multiheme cytochromes belonging to the class III of Ambler's classification. Since 1954, when cytochromec3was isolated fromDesulfovibrio vulgarisfor the first time by Postgate, these proteins have been widely characterized, especially those from theDesulfovibrio(D.) genus. All these cytochromes have their heme group attached to the polypeptide chain by cysteine residues and show bis‐histidinyl coordination of the heme iron and a highly conserved heme‐binding motif (CXXCH or CXXXXCH). Cytochromesc3show a wide variety of redox potentials, ranging from 0 to −400 mV, are usually periplasmatic proteins, and are believed to play key roles in the electron transfer chains. Recently, the cytochromec3group was divided into two main types on the basis of structural, functional, and genetic differences: type I cytochromec3(TpI‐c3) and type II cytochromec3(TpII‐c3). This paper reviews their structural, spectroscopic, and functional properties, based on the wealth of information currently available. These include physicochemical properties, redox mechanisms, coupling between electron and proton transfer, and data concerning the interaction with their redox partners obtained by experimental and molecular modeling methods.
Optical Biosensing Based on Metal and Semiconductor Colloidal Nanocrystals
Authors: Comparelli Roberto , Curri Maria Lucia , Cozzoli Pantaleo Davide , Striccoli Marinella
Published: September 2007

The sections in this article are

Overview

Introduction

Colloidal Nanocrystals

Size‐dependent Optical Properties

Chemical Synthesis

Nanocrystal Functionalization for Biosensing

Surface Capping Exchange

Coating with a Silica Shell

Surface Modification through Hydrophobic Interactions

Optical Techniques

Colorimetric Tests

Fluorescence

Fluorescence Resonance Energy Transfer

Fluorescence Lifetime

Multiphoton Techniques

Metal‐enhanced Fluorescence

Surface Plasmon Resonance

Surface‐enhanced Resonance Spectroscopy

Advantages and Disadvantages of Nanocrystals in Optical Detection

Applications

Biosensing with Semiconductor Nanocrystals

Biosensing with Metallic Nanoparticles

Towards Marketing

Conclusions
Direct Ink‐Jet Printing of Ag–Cu Nanoparticle and Ag‐Precursor Based Electrodes for OFET Applications
Authors: Gamerith S. , Klug A. , Scheiber H. , Scherf U. , Moderegger E. , List E. J. W.
Published: September 2007

The field of organic electronics has seen tremendous progress over the last years and all‐solution‐based processes are believed to be one of the key routes to ultra low‐cost roll‐to‐roll device and circuit fabrication. In this regard a variety of functional materials has been successfully designed for inkjet printing. While orthogonal‐solvent approaches have frequently been used to tackle the solubility issue in multilayer solution processing, the focus of this work lies on printed metal electrodes for organic field‐effect transistors (OFET) and their curing concepts. Two metallic inkjet‐printable materials are studied: i) a silver‐copper nanoparticle based dispersion and ii) a soluble organic silver‐precursor. Photoelectron spectroscopy reveals largely metallic properties of the cured materials, which are compared with respect to OFET performance and process‐related issues. Contact resistance of the prepared metal electrodes is significantly larger than that of evaporated top‐contact gold electrodes. As direct patterning via inkjet printing limits the reliably achievable channel length to values well above 10 μm, the influence of contact resistance is rather small, however, and overall device performance is comparable.
Transparent Nanometric Cubic and Tetragonal Zirconia Obtained by High‐Pressure Pulsed Electric Current Sintering
Authors: Anselmi‐Tamburini U. , Woolman J. N. , Munir Z. A.
Published: September 2007

Transparent samples of cubic (8 mol % yttria) and tetragonal (3 mol % yttria) zirconia were prepared from nanometric powders by the pulsed electric current sintering process. The crystallite size of the resulting dense samples was about 50 nm in both cases. The consolidation pressure had a positive effect on the occurrence of transparency for both modifications. Transmittance in the near infrared for 1 mm thick samples is above the 60 % for the cubic (8 %YSZ) and above 50 % for the tetragonal (3 % YSZ) zirconia, representing between 70 and 80 % of the theoretical values of the two modifications. Samples had a yellowish‐brown coloration which was attributed to the presence of color centers. Annealing in oxygen improved transmittance initially, but prolonged annealing resulted in translucent samples. The role of porosity in transmittance is analyzed.
Chalcogenide Glasses Based on Germanium Disulfide for Second Harmonic Generation
Authors: Guignard M. , Nazabal V. , Smektala F. , Adam J.‐L. , Bohnke O. , Duverger C. , Moréac A. , Zeghlache H. , Kudlinski A. , Martinelli G. , Quiquempois Y.
Published: September 2007

High second‐order susceptibilities are created by thermal poling in bulk germanium disulfide based chalcogenide glasses. Experimental conditions of the poling treatment (temperature, voltage, time) were optimized for each glass composition. The second‐order nonlinear signals were recorded by using the Maker fringes experiment and a second‐order coefficient χ(2) up to 8 pm V–1 was measured in the Ge25Sb10S65 glass. This value is obtained using a simulation based on accurate knowledge of the thickness of the nonlinear layer. Two mechanisms are proposed to explain the creation of a nonlinear layer under the anode: the formation and the migration of charged defects towards the anode may mainly occur in Ge20Ga5Sb10S65 and Ge25Ga5S70 glasses, whereas the migration of Na+ ions towards the cathode may be responsible for the accumulation of negative charges under the anode in Ge33S67 and Ge25Sb10S65 glasses. Different electronic conductivity behaviors seem to be at the origin of the phenomenon. In parallel, the potential effect of the poling treatment on the structural and electronic properties is studied using Raman spectroscopy and secondary ion mass spectroscopy measurements.
Periodically Ordered Meso‐ and Macroporous SiO2 Thin Films and Their Induced Electrochemical Activity as a Function of Pore Hierarchy
Authors: Sel O. , Sallard S. , Brezesinski T. , Rathouský J. , Dunphy D. R. , Collord A. , Smarsly B. M.
Published: September 2007

Silica thin films with variable pore hierarchy (different combinations of small meso‐, large meso‐, and macropores) were produced via evaporation induced self‐assembly in a one‐pot synthesis. A suitable block copolymer and an ionic liquid served as porogens for the generation of different types of mesopores whereas polymethylmethacrylate particles were used as macrotemplate. The silica architectures were characterized by various state‐of‐the‐art techniques, such as 2D‐SAXS, TEM, SEM, AFM, krypton and nitrogen sorption. Moreover, electrochemical functionalization was utilized as a tool to study the hierarchy‐property relationship. Thus, hierarchically porous films prepared on FTO‐coated glass were post‐synthetically silylated and electrochemically active ferrocene groups subsequently grafted onto the pore walls. Cyclic voltammetry was used to monitor the induced electrochemical activity as a function of variations in the pore hierarchy. It turned out that multimodal pore systems possess a relatively higher electrochemical response due to better connection between the pores and higher surface area.
Organic Field‐Effect Devices as Tool to Characterize the Bipolar Transport in Polymer‐Fullerene Blends: The Case of P3HT‐PCBM
Authors: Morana M. , Koers P. , Waldauf C. , Koppe M. , Muehlbacher D. , Denk P. , Scharber M. , Waller D. , Brabec C.
Published: September 2007

In organic bulk heterojunction solar cells (oBHJ) the blend morphology in combination with the charge transport properties of the individual components controls the extracted photocurrent. The organic field‐effect transistor (OFET) has been proved as a powerful instrument to evaluate the unipolar carrier transport properties in a wide range of cases. In our work we extend the OFET concept to the evaluation of the bipolar transport properties in polymer‐fullerenes blends and propose a method to improve the accuracy of the evaluation. The method is based on capacitance–voltage (C–V) measurements on MOS structures prepared on the same blends and delivers complementary information on the bulk heterojunction to the one obtained with FETs. The relevance for photovoltaic applications is investigated through the correlation between the current–voltage behavior of solar cells and the bipolar mobility for composites with varying polymer molecular weight and processed from different solvents. In particular the transport features of solar cells produced from o‐Xylene (oX), a non chlorinated solvent more suitable to production requirements, have been compared to the one of devices cast from Chlorobenzene (CB) solution. For the P3HT‐PCBM blend a consistent correlation between the mobility and the electrical fill factor and power performance was found. A significant asymmetry in the bipolar carrier mobility, together with low electron mobility dependent on the Mw value, affects the performances of thick o‐Xylene cast devices. In the case of devices processed from Chlorobenzene the slower carrier has higher mobility and the small electrical losses detected are eventually more related to the formation of space‐charge and eventually to surface recombination. This results in an efficient charge collection that is almost thickness independent. We report a dependence of the slow‐carrier type (electrons or holes) and their mobility on the specific combination of molecular weight and solvent. The mobility data and the solar cell performance coherently fit to the prediction of a device model only based on the drift of carriers under the built‐in electric field originated in the donor‐acceptor oBHJ.
Formation of Gold and Silver Nanoparticle Arrays and Thin Shells on Mesostructured Silica Nanofibers
Authors: Zhang S. , Ni W. , Kou X. , Yeung M. H. , Sun L. , Wang J. , Yan C.
Published: September 2007

Mesostructured silica nanofibers synthesized in high yields with cetyltrimethylammonium bromide as the structure‐directing agent in HBr solutions are used as templates for the assembly of Au and Ag nanoparticles and the formation of thin Au shells along the fiber axis. Presynthesized spherical Au and Ag nanoparticles are adsorbed in varying amounts onto the silica nanofibers through bifunctional linking molecules. Nonspherical Au nanoparticles with sharp tips are synthesized on the nanofibers through a seed‐mediated growth approach. The number density of nonspherical Au nanoparticles is controlled by varying the amount of seeded nanofibers relative to the amount of supplied Au precursor. This seed‐mediated growth is further used to form continuous Au shells around the silica nanofibers. Both the Au‐ and Ag‐nanoparticle/silica‐nanofiber hybrid nanostructures and silica/Au core/shell fibers exhibit extinction spectra that are distinct from the spectra of Au and Ag nanoparticles in solution, indicating the presence of new surface plasmon resonance modes in the silica/Au core/shell fibers and surface plasmon coupling between closely spaced metal nanoparticles assembled on silica nanofibers. Spherical Au‐ and Ag‐nanoparticle/silica‐nanofiber hybrid nanostructures are further used as substrates for surface‐enhanced Raman spectroscopy, and the enhancement factors of the Raman signals obtained on the Ag‐nanoparticle/silica‐nanofiber hybrid nanostructures are 2 × 105 for 4‐mercaptobenzoic acid and 4‐mercaptophenol and 7 × 107 for rhodamine B isothiocyanate. These hybrid nanostructures are therefore potentially useful for ultrasensitive chemical and biological sensing by using molecular vibrational signatures.
Patterning Semiconductor Nanocrystals in Polymer Films
Authors: Paquet C. , Kumacheva E.
Published: September 2007

This paper reports a method of patterning semiconductor nanocrystals (NCs) in a polymer film. By combining lithographic concept with polymerization‐induced phase separation in a NC‐monomer mixture, we produced topographic and lateral compositional patterns in NC‐polymer films. The quality of the patterns was controlled by the competition between the rate of polymerization‐induced phase separation and the change in viscosity of the polymerizing mixture.
Polymer‐Bound Pyridine‐Bis(oxazoline). Preparation through Click Chemistry and Evaluation in Asymmetric Catalysis
Authors: Tilliet Mélanie , Lundgren Stina , Moberg Christina , Levacher Vincent
Published: September 2007

A pyridine‐bis(oxazoline) ligand was efficiently immobilized by copper(I)‐catalyzed azide‐alkyne cycloaddition onto a polystyrene resin. The so obtained click‐pybox resin 1a was associated with various metal salts (YbCl3, LuCl3, CuOTf) and the resulting resin‐bound catalysts were explored in ring‐opening of cyclohexene oxide, silylcyanation of benzaldehyde and alkynylation of imines. These new polymer‐supported catalysts exhibit good to excellent performances in terms of catalytic activity, enantioselectivity and recyclability.
PuPHOS and CamPHOS Ligands in the Intermolecular Catalytic Pauson–Khand Reaction
Authors: Lledó Agustí , Solà Jordi , Verdaguer Xavier , Riera Antoni , Maestro Miguel A.
Published: September 2007

The first asymmetric intermolecular cobalt‐catalyzed Pauson–Khand reaction is described. The use of the hemilabile CamPHOS ligand provides good conversions and selectivity up to 28 % ee. The catalytic process was studied by in situ FT‐IR and it was found that both bridged and non‐bridged complexes were present in the reaction mixture. Our results suggest that recognition between the alkyne substrate and the ligand is essential to attain stereocontrol in the catalytic cyclization.
Adaptive multiobjective optimization of process conditions for injection molding using a Gaussian process approach
Authors: Zhou Jian , Turng Lih‐Sheng
Published: September 2007

Selecting the proper process conditions for the injection‐molding process is treated as a multiobjective optimization problem, where different objectives, such as minimizing the injection pressure, volumetric shrinkage/warpage, or cycle time, present trade‐off behaviors. As such, various optima may exist in the objective space. This paper presents the development of an integrated simulation‐based optimization system that incorporates the design of computer experiments, Gaussian process (GP) for regression, multiobjective genetic algorithm (MOGA), and levels of adjacency to adaptively and automatically search for the Pareto‐optimal solutions for different objectives. Since the GP approach can provide both the predictions and the estimations of the predictions simultaneously, a nondominated sorting procedure on the predicted variances at each iteration step is performed to intelligently select extra samples that can be used as additional training samples to improve the GP surrogate models. At the same time, user‐defined adjacency constraint percentages are employed for evaluating the convergence of iteration. The illustrative applications in this paper show that the proposed optimization system can help mold designers to efficiently and effectively identify optimal process conditions. © 2007 Wiley Periodicals, Inc. Adv Polym Techn 26:71–85, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20092
Unified model for nonideal multicomponent molecular diffusion coefficients
Authors: Leahy‐Dios Alana , Firoozabadi Abbas
Published: September 2007

Multicomponent diffusion is important in a variety of applications. In order to calculate diffusion flux, molecular diffusion coefficients are required, where fluid nonideality and the multicomponent nature of the mixture have a significant effect. A unified model for the calculation of diffusion coefficients of gas, liquid and supercritical states of nonpolar multicomponent mixtures is presented. A new correlation is proposed for the binary infinite dilution‐diffusion coefficients. The generalized Vignes relation is used in multicomponent mixtures. Nonideality is rigorously described by the fugacity derivatives evaluated by the volume‐translated Peng‐Robinson equation of state. Predictions for highly nonideal gas and liquid multicomponent mixtures demonstrate the reliability of the proposed methodology. © 2007 American Institute of Chemical Engineers AIChE J, 2007
Successful treatment of cytomegalovirus‐associated hemophagocytic syndrome by intravenous immunoglobulins
Authors: Hot Arnaud , Madoux Marie Hélène Girard , Viard Jean P. , Coppéré Brigitte , Ninet Jacques
Published: September 2007

Virus‐associated hemophagocytic syndrome (VAHS) is a rare complication in early cytomegalovirus (CMV) infection. There is no standard therapy for VAHS and the clinical course is variable. Data on the use of intravenous immunoglobulin (IVIG) in the treatment of CMV‐associated VAHS are limited. We report a previously healthy, 32‐year‐old woman who presented with general malaise, fever, chills, and splenomegaly. Laboratory examination showed marked elevation of aminotransferase, leucopoenia, and thrombocytopenia. Acute CMV‐infection was documented by the presence of immunoglobulin M anti‐CMV and positive viremia in blood sample. Bone marrow examination revealed extensive hemophagocytosis. IVIG was administered after the diagnosis of CMV‐associated VAHS. Her symptoms and laboratory abnormalities improved dramatically after the onset of the treatment and she did not require antiviral agent. Am. J. Hematol., 2008. © 2007 Wiley‐Liss, Inc.
Studies of age‐correlated features of cognitive‐behavioral development in children and adolescents with genetic disorders
Authors: Fisch Gene S. , Carpenter Nancy , Howard‐Peebles Patricia N. , Holden Jeanette J.A. , Tarleton Jack , Simensen Richard , Nance Walter
Published: September 2007

Studies of age‐related features of cognitive‐behavioral deficits produced by genetic mutations permit us to draw inferences about how brain development may be related cognitive ability as the child ages. Except for Down syndrome (DS) and the fragile X mutation (FRAXA), little is known about the longitudinal changes in cognitive‐behavioral development in individuals with genetic abnormalities producing learning disabilities (LD) or mental retardation (MR). The purpose of this prospective study was to compare and contrast age related to cognitive abilities, adaptive and maladaptive behaviors in children and adolescents in the same age range, diagnosed with one of three genetic disorders: the FRAXA mutation, Neurofibromatosis type 1 (NF1) or Williams–Beuren syndrome (WBS). We also sought to examine whether cognitive‐behavioral abilities associated with these three genetic disorders were related systematically to age. We examined 108 children, ages 4–15 years, with FRAXA, WBS, or NF1. Results show that there is a significant negative correlation between age and IQ, and between age and adaptive behavior (DQ) scores, in children with FRAXA and WBS, but not in children with NF1. All three groups of children have unusually high proportions of maladaptive behavior, ranging from 1/6 children with NF1 to 2/3 children with FRAXA. Cognitive and adaptive behavior profiles of children with FRAXA and WBS were also surprisingly similar. Our findings suggest the need for examining longitudinal developmental cognitive‐behavioral changes in children and adolescents with all genetic disorders that produce LD or MR. © 2007 Wiley‐Liss, Inc.
Clinical phenotype of lathosterolosis
Authors: Rossi Massimiliano , D'Armiento Maria , Parisi Ida , Ferrari Paola , Hall Christine M. , Cervasio Mariarosaria , Rivasi Francesco , Balli Fiorella , Vecchione Raffaella , Corso Gaetano , Andria Generoso , Parenti Giancarlo
Published: September 2007

Lathosterolosis (LS) is a defect of cholesterol biosynthesis due to the deficiency of the enzyme sterol‐C5‐desaturase. Only two patients have been described to date, both presenting with multiple malformations, mental retardation, and liver involvement. In addition in one of them pathological examination revealed mucolipidosis‐like inclusions on optic microscopy analysis, and peculiar lysosomal lamellar bodies on electron microscopy analysis. This study is focused on a better characterization of the clinical phenotype of LS. We describe a further case in a fetus, sibling of the first patient reported, presenting with neural tube defect, craniofacial and limb anomalies, and prenatal liver involvement. The fetal phenotype suggests the possible occurrence of significant intrafamilial variability in LS, and expands the phenotypic spectrum of the disease. Histological examination of autopsy samples from the fetus and skin fibroblasts from the living sibling suggested that the mucolipidosis‐like picture previously reported is not a constant feature of LS, being possibly associated with the most severe biochemical defects, but confirmed the ultrastructural finding of lamellar inclusions. The LS phenotype appears to be characterized by the distinctive association of a recognizable pattern of congenital anomalies, involving axial and appendicular skeleton, liver, central nervous and urogenital systems, and lysosomal storage. This condition partially overlaps with other defects of sterol metabolism, suggesting intriguing pathogenic links among these conditions. © 2007 Wiley‐Liss, Inc.
MYO15A (DFNB3) mutations in Turkish hearing loss families and functional modeling of a novel motor domain mutation
Authors: Kalay Ersan , Uzumcu Abdullah , Krieger Elmar , Çaylan Refik , Uyguner Oya , Ulubil‐Emiroglu Melike , Erdol Hidayet , Kayserili Hülya , Hafiz Gunter , Başerer Nermin , Heister Angelien J.G.M. , Hennies Hans C. , Nürnberg Peter , Başaran Seher , Brunner Han G. , Cremers Cor W.R.J. , Karaguzel Ahmet , Wollnik Bernd , Kremer Hannie
Published: September 2007

Myosin XVA is an unconventional myosin which has been implicated in autosomal recessive nonsyndromic hearing impairment (ARNSHI) in humans. In Myo15A mouse models, vestibular dysfunction accompanies the autosomal recessive hearing loss. Genomewide homozygosity mapping and subsequent fine mapping in two Turkish families with ARNSHI revealed significant linkage to a critical interval harboring a known deafness gene MYO15A on chromosome 17p13.1‐17q11.2. Subsequent sequencing of the MYO15A gene led to the identification of a novel missense mutation, c.5492G → T (p.Gly1831Val) and a novel splice site mutation, c.8968 − 1G → C. These mutations were not detected in additional 64 unrelated ARNSHI index patients and in 230 Turkish control chromosomes. Gly1831 is a conserved residue located in the motor domains of the different classes of myosins of different species. Molecular modeling of the motor head domain of the human myosin XVa protein suggests that the Gly1831Val mutation inhibits the powerstroke by reducing backbone flexibility and weakening the hydrophobic interactions necessary for signal transmission to the converter domain. © 2007 Wiley‐Liss, Inc.
Effects of hyperbranched poly(amido‐amine)s structures on synthesis of Ag particles
Authors: Sun Youyi , Liu Yaqing , Guizhe Zhao , Zhang Qijin
Published: September 2007

The synthesis of Ag particles stabilized poly (N,N′‐methylene bisacrylamide N‐aminoethyl piperazine) (MBA‐AEPZ) and poly(N,N′‐dodecyl diacrylamide N‐aminoethyl piperazine) (MDA‐AEPZ) was reported. The effects of hyperbranched polymer structures and hyperbranched polymer concentrations were studied on the size and size distribution of Ag particles, which were determined from the UV plasmon absorption band and transmission electronmicroscopic analyses. The data show that slight change (10.3 and 9.7 nm) and large change on particle size (3.9 and ∼ 200 nm) were observed with increase in concentrations of poly(MBA‐AEPZ) and poly(MDA‐AEPZ) at the same M:D, respectively. The difference is explained in terms of a mechanism of structure‐dependent stabilization. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Reactive extrusion to synthesize intumescent flame retardant with a solid acid as catalyst and the flame retardancy of the products in polypropylene
Authors: Liu Yuan , Wang Qi
Published: September 2007

Reactive extrusion and solid acid catalysis technologies were adopted in the pentaerythritol–melamine phosphate (PER‐MP) reaction to synthesize intumescent flame retardant, melamine salt of pentaerythritol phosphate (MPP), which was applied in flame retardant polypropylene (PP). This environment‐friendly synthesis method provided a solution to the problems of conventional methods. On one hand, reactive extrusion in a twin screw extruder can effectively mix and transfer viscous materials that usually results in a tough stir in a conventional reactor, and achieve a continuous synthesis process. On the other hand, the solid acid, silicotungstic acid (STA) serving as a catalyst, can maintain a satisfactory conversion even with a low extrusion temperature and a short residence time, thus effectively suppressing foaming in the process of the reaction. Furthermore, without removal like other catalysts in general chemical reactions, STA was kept in produced MPP to constitute a synergism flame retardant system, therefore further improved the flame retardancy. LOI and UL94 test showed that the STA‐catalyzed MPP (by reactive extrusion) possessed much better flame retardancy in PP when compared with the noncatalyzed MPP (by reactive extrusion), as well as present commercial MPP (by POCl3 method). In our investigation, the catalytic and synergistic effects of STA, as well as the related factors of the reactive extrusion affecting the conversion of the PER‐MP reaction, flame retardancy and mechanical performance of the corresponding flame retardant PP, were systematically investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Insulation performance and microstructure in modified polyethylene by MPE
Authors: Wang X. , Tu D. M. , Lei C. , Du Q. G.
Published: September 2007

Electrical measurements have shown to be able to provide useful information on physical, chemical, and microstructural properties of dielectric material. In this article, the depolarization characteristics of low‐density polyethylene blended with a small amount of metallocene catalyzed polyethylene were measured by pulsed electro‐acoustic method under various stresses. According to space charge limited current theory, the derivation of quantities such as mean volume density of space charge, apparent trap‐controlled mobility, trap depth distribution, and threshold stress were discussed. The test results showed that low‐density polyethylene blended with 1 wt % metallocene catalyzed polyethylene could effectively decrease deep trap density, increase shallow trap density, and then improve the mobility of charges. We also measured the breakdown voltage and tensile strength of the blends. It was found that low‐density polyethylene blended with a small amount of metallocene catalyzed polyethylene could effectively improve its breakdown voltage and tensile strength but reduce the material tenacity. Finally, mechanical relax and crystalline morphology of blends were studied by dynamic mechanical measurement, wide‐angle X‐ray diffraction, and small‐angle X‐ray scattering experiments. The results showed that the improvement of electrical properties and mechanical strength in the blends were relevant to the crystalline morphology. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
FTIR spectroscopic study of the effect of microwave heating on the transformation of cellulose I into cellulose II during mercerization
Authors: Moharram M. A. , Mahmoud Osama M.
Published: September 2007

Fourier transform infrared (FTIR) spectroscopy techniques were used in the study of the effect of microwave (MW) heating on the structural properties of cotton fibers and on the mercerization mechanism of these fibers. Samples of the fibers were microwave heated for different times and different microwave powers. Also, mixtures of cotton fibers and aqueous solution of NaOH with different concentrations were exposed to microwave radiation for different times and different powers. It was found that microwave heating of cotton fibers under these experimental conditions causes no observable changes in their spectral features apart from slight changes in the intensities of the absorption bands. The determined values of the absorbances ratio A1375 cm−1/A2900 cm−1revealed that microwave heating for short periods and at low powers decreases the crystallinity of cotton as the result of the drying effect of microwave heating, while microwave heating for longer periods and at higher power results in recristallyzation of the fibers. The analysis of the experimentally obtained data revealed that microwave heating that causes molecular motions by migration of ions and rotations of the dipoles produces no considerable effects on the mechanism of mercerization but only reduces the concentration of NaOH in the solution and the time of treatment which are needed for the complete transformation of cellulose lattice type I into cellulose lattice type II without any heating. Also it was found that the magnitude of reductions depends on the applied power. Moreover the results proved that the deconvolution and the second derivatives of the FTIR spectra of cotton fibers can be used as a useful tool for distinguishing cellulose lattice type II from cellulose lattice type I. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Surface characterization and properties of functionalized nonwoven
Authors: Wei Qufu , Yu Liangyan , Hou Dayin , Huang Fenglin
Published: September 2007

Nonwoven materials have been increasingly used in many industries. The surface properties of nonwoven materials are of importance in these applications. In this study, functional nonwoven materials were prepared by sputtering deposition of copper (Cu), zinc oxide (ZnO), and polytetrafluoroethylene (PTFE) on the surface of polypropylene (PP) fibers. Atomic Force Microscopy (AFM) and Environmental Scanning Electron Microscopy (ESEM) were employed to study the surface morphology and chemical compositions. The observations by AFM revealed the formation of functional nanostructures on the fibre surfaces and the ESEM examination confirmed the formation of functional compositions on the fiber surface. The metallic coating of Cu significantly improved the surface conductivity of the material. The transmittance analysis indicated that the ZnO coating obviously increased the ultra‐violet absorption of the material. The surface hydrophobicity of the nonwoven material was enhanced by the sputter coating of PTFE. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Real‐time ultrasonic monitoring of the injection‐molding process
Authors: He Bobing , Zhang Xiaoqing , Zhang Qin , Fu Qiang
Published: September 2007

In this study, a noninvasive and nondestructive ultrasonic technique has been used to monitor the polymer injection‐molding process in an attempt to establish a fundamental understanding of the processing/morphology/ultrasonic signal relationships. The ultrasonic technique not only can provide information on solidification affected by various temperatures and pressures but also can reflect the evolution of the crystal morphology and phase morphology of polymer blends. In addition, the periodic vibration of the dynamic‐packing injection‐molding process, in which the melt is forced to move repeatedly in a chamber by two pistons that move reversibly with the same frequency as the solidification progressively occurs from the mold wall to the molding core part, can also be monitored with the ultrasonic velocity and attenuation. Our results indicate that the ultrasonic technique is sensitive and promising for the real‐time monitoring of the injection‐molding process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Poly(ether urethane) flexible cyanate ester resins: Synthesis, characterization, and performance in commercial epoxy and polyurethane applications
Authors: Kumar T. Pazhani , Sivasankar B.
Published: September 2007

A poly(ether urethane)‐based cyanate ester resin (PEUCER) with a biphenyl polyether backbone obtained from polymeric 4,4′‐diphenylmethanediisocyanate, bisphenol A, polyether polyols of three different molecular weights, and cyanogen bromide was synthesized to obtain a polymer with better functional and physical properties, such as adhesion, flexibility, and thermal stability. The synthesis of the poly(ether urethane)‐based 4,4′‐(oxybiphenyl propane) cyanate ester involved three steps: the formation of the poly(ether urethane) NCO‐terminated prepolymer, the formation of the OH‐terminated poly (ether urethane) prepolymer (PEU–PP), and the esterification reaction of cyanate to produce PEUCER. PEUCER was cyclotrimerized to yield a triazine‐ring‐containing polymer, which possessed better adhesion at high temperatures and better impact resistance. PEU–PP and PEUCER were characterized with wet chemical analysis, spectral methods, and thermal methods. PEUCER showed better performance with respect to thermal and adhesion properties with a single‐part polyurethane lamination adhesive and also showed better performance as a toughening agent in a two‐part epoxy laminate system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis of silver nanocrystals by a modified polyol method
Authors: Bregado‐Gutiérrez Julio , Saldívar‐García Armando J. , López Hugo F.
Published: September 2007

A modification of the polyol method has been shown to result in improved efficiency and enhanced kinetics for the synthesis of silver nanocrystals when compared with the traditional polyol method. The Ag nanocrystals produced were characterized using X‐ray diffraction and transmission electron microscopy. Accordingly, the exhibited Ag crystal structure, corresponding lattice constants, and resultant particle sizes were determined by these means. In addition, using Fourier transform infrared spectroscopy, it was found that a solid‐state reaction between the AgNO3 and the Poly (vinylpyrrolidone) (PVP) takes place prior to their dissolution in ethylene glycol. Moreover, when crystals grow under total rest conditions, they do not develop a spherical morphology as in the traditional polyol method, but a well‐defined geometric shape showing preferential crystallographic growth directions. Under the experimental conditions of this work, the exhibited nanocrystal shapes were quasi‐planar hexagonal. Apparently, PVP interacts with the FCC crystal structure promoting growth on the {100} preferential direction by playing the role of an atomic arranger. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
A novel imidazole derivative curing agent for epoxy resin: Synthesis, characterization, and cure kinetic
Authors: Fang Wang , Jun Xiao , Jing‐Wen Wang , Shu‐Qin Li
Published: September 2007

A novel imidazole derivative (named as EMI‐g‐BGE) was synthesized through the reaction of 2‐ethyl‐4‐methyl imidazole (EMI) and butyl glycidyl ether (BGE) and characterized by elemental analysis, FTIR spectroscopy, and 1H NMR spectroscopy. The curing kinetic of diglycidyl ether of bisphenol A (DGEBA) epoxy resin with EMI‐g‐BGE as curing agent was studied by nonisothermal DSC technique at different heating rates. Dynamic DSC scans indicated that EMI‐g‐BGE was an effective curing agent of epoxy resin. The apparent activation energy Ea was 71.8 kJ mol−1 calculated through Kissinger method, and the kinetic parameters were determined by Málek method for the kinetic analysis of the thermal treatment obtained by DSC measurement. A two‐parameter (m, n) autocatalytic model (Šesták‐Berggren equation) was found to be the most adequate selected kinetic model. In addition, the predicted curves from the kinetic model fit well with the nonisothermal DSC thermogram. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Effect of crystallization temperature on crystal modifications and crystallization kinetics of poly(L‐lactide)
Authors: Pan Pengju , Zhu Bo , Kai Weihua , Dong Tungalag , Inoue Yoshio
Published: September 2007

The crystalline structure of poly(L‐lactide) (PLLA) have been found to quite depend on the crystallization temperatures (Tcs), especially in the range of 100−120°C, which is usually used as the crystallization temperature for the industrial process of PLLA. The analysis of wide‐angle X‐ray diffraction and Fourier transformed infrared spectroscopy revealed that 110°C is a critical temperature for PLLA crystallization. At Tc < 110°C and Tc ≥ 110°C, the α′ and α crystals were mainly produced, respectively. Besides, the structural feature of the α′‐form was illustrated, and it was found that the α′‐form has the larger unit cell dimension than that of the α‐form. Moreover, the crystallization kinetics of the α′ and α crystals are different, resulting in the discontinuousness of the curves of spherulite radius growth rate (G) versus Tc and the half time in the melt‐crystallization (t1/2) versus Tc investigated by Polarized optical microscope and Differential scanning calorimetry, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Effect of solvent plasticization on polypropylene microcellular foaming process and foam characteristics
Authors: Kaewmesri W. , Rachtanapun P. , Pumchusak J.
Published: September 2007

In this research, the effect of crystalline fraction of polypropylene (PP) on cell nucleation behavior was overcome by an introduction of solvent‐plasticized step to the microcellular foaming in a solid‐state batch‐foaming process. Utilizing the plasticization performance of the solvent facilitated the PP to be foamed at the temperatures lower than its melting point with the dramatic development in the cellular morphology of the final foams. In consequence of the heterogeneous cell nucleation sites induction and the crystalline loss, which were induced by solvent, a high cell density (i.e., 109–1010cells/cm3) was promoted without the cell sacrificing at the elevated temperatures (155 and 165°C) and favorable PP microcellular foams were accomplished. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Mechanical properties and porosity of polylactide for biomedical applications
Authors: Sawalha Hassan , Schroën Karin , Boom Remko
Published: September 2007

In this study, the strength, ductility, and porosity of polylactide films prepared by immersion precipitation and film casting in air were investigated. To induce extra porosity in the films, dodecane was added to the polymer casting solution. The structure, porosity, and mechanical properties of the films were evaluated. The ultimate strength and elastic modulus of neat poly(L‐lactide) prepared by film casting were at least twice those of the same film prepared in methanol, whereas the ductility of these films was considerably higher than that for air. The porosity, size of pores, and interconnectivity of pores increased gradually with increasing dodecane concentration. This dodecane‐induced porosity (as high as 80%), progressively reduced the ultimate strength and modulus of practically all films but remarkably improved the ductility of films prepared in air, and this can be related to a decrease in the crystallization temperature. For films prepared in water or poly(D,L‐lactide) films in general, the ultimate strength, modulus, and ductility of films prepared in water were significantly lower than those of air‐cast poly(L‐lactide) films. In summary, the results obtained in this research show that it is possible to tailor the properties of films for various biomedical applications through the use of the polymer type, preparation method, and dodecane‐induced porosity as tools. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Mast Cells Appearing in Long‐term Skeletal Muscle Cell Cultures of Rat
Authors: Cheng Chang‐xie , Li Yong‐nan , Ohno Hiroshi , Sawanobori Kazuko , Li Yan‐chao , Shimada Osamu , Atsumi Saoko
Published: September 2007

Mast cells are known to be involved in type I allergy and to be localized in almost all tissues in the body. However, they have slightly different properties depending on their tissue of residence. Although mast cells are found in skeletal muscle tissue, there have been no reports of their appearance in cultured skeletal muscles. We report here that mast cells appear in long‐term cultures of skeletal muscles from neonatal rats and rat fetuses. When muscle cells were disseminated and cultured in minimum essential medium with 10% fetal calf serum and 10% horse serum, oval cells containing large granules started to appear on myotube sheets at 5 days of culture. These oval cells continued to proliferate for 2–3 months, and showed immunoreactivity for histamine, tryptase, FcεRI, and c‐kit. They showed metachromatic staining with 0.5% toluidine blue at pH 0.5 and were stained with both Alcian blue and safranin. Biochemically measured histamine content per dish was significantly higher in 2‐month than in 5‐day culture. From these results, we concluded that these oval cells were mast cells. Because proteases from mast cells have been reported previously to affect myoblast proliferation, the present findings suggest that there may be some interaction between mast cells and muscle cell proliferation or differentiation. The present finding that mast cells are easily obtained from ordinary skeletal muscle cultures provides a useful method for the study of the diverse functions of mast cells. Anat Rec, 1424‐1430, 2007. © 2007 Wiley‐Liss, Inc.