bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics and mechanism of oxidation of the drug mephenesin by bis(hydrogenperiodato)argentate(III) complex anion
Authors: Shen Shigang , Shi Hongmei , Sun Hanwen
Published: June 2007

Mephenesin is being used as a central‐acting skeletal muscle relaxant. Oxidation of mephenesin by bis(hydrogenperiodato)argentate(III) complex anion, [Ag(HIO6)2]5−, has been studied in aqueous alkaline medium. The major oxidation product of mephenesin has been identified as 3‐(2‐methylphenoxy)‐2‐ketone‐1‐propanol by mass spectrometry. An overall second‐order kinetics has been observed with first order in [Ag(III)] and [mephenesin]. The effects of [OH−] and periodate concentration on the observed second‐order rate constants k′ have been analyzed, and accordingly an empirical expression has been deduced: k′ = (ka + kb[OH−])K1/{f([OH−])[IO−4]tot + K1}, where [IO−4]tot denotes the total concentration of periodate, ka = (1.35 ± 0.14) × 10−2M−1s−1 and kb = 1.06 ± 0.01 M−2s−1 at 25.0°C, and ionic strength 0.30 M. Activation parameters associated with ka and kb have been calculated. A mechanism has been proposed to involve two pre‐equilibria, leading to formation of a periodato‐Ag(III)‐mephenesin complex. In the subsequent rate‐determining steps, this complex undergoes inner‐sphere electron transfer from the coordinated drug to the metal center by two paths: one path is independent of OH− whereas the other is facilitated by a hydroxide ion. In the appendix, detailed discussion on the structure of the Ag(III) complex, reactive species, as well as pre‐equilibrium regarding the oxidant is provided. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 440–446, 2007
Photonic-crystal-fiber solutions for ultrafast chromium forsterite laser technologies
Authors: Ivanov A A , Alfimov M V , Zheltikov A M
Published: June 2007

Over the past years, photonic-crystal-fiber components and devices have imparted a powerful momentum to the development of femtosecond chromium forsterite laser systems. Fibers of this type allow efficient spectral and temporal transformations of ultrashort light pulses delivered by Cr:forsterite laser sources, enhancing the potential of these lasers as a powerful tool for nanophotonics, biomedical optics, microspectroscopy, telecommunication technologies, semiconductor chip imaging, coherent control, optical metrology, and offering a platform for the creation of an advantageous front end for extreme-intensity laser systems.
Thermal analysis of teeth irradiated with Er,Cr:YSGG at low fluences
Authors: Ana P A , Blay A , Miyakawa W , Zezell D M
Published: June 2007

This study aimed to evaluate the surface and pulp temperature rises when teeth are irradiated with Er,Cr:YSGG laser at low fluences, with or without a photosensitizer. It was chosen 81 third molar human teeth which were randomly divided into six groups, according to the Er,Cr:YSGG laser fluences (2.8 J/cm2, 5.6 J/cm2, and 8.5 J/cm2) and the recovering or not of a photosensitizer (a thin layer of coal paste) over enamel surfaces. All samples were irradiated without coolant. The surface temperatures and heat propagation were recorded by thermographic camera, and the pulpal temperatures were registered by type-K thermocouples. After laser irradiation, enamel surfaces were analyzed by scanning electron microscopy (SEM). The intrapulpal temperature increases were below the threshold for pulp damages (5.6°C), and they were dependent on the fluence applied. The surface recovering with coal paste significantly reduced the intrapulpal temperature increments in 8.5 J/cm2 samples. The coal paste also influenced the surface temperatures, which reached 222.6°C when samples were irradiated at fluence of 8.5 J/cm2. The SEM analysis revealed a micro-ablation pattern for all fluences tested. The photosensitizer was efficient for reducing heat transfer to the pulp chamber, increasing laser absorption into the enamel. The fluences of 8.5 J/cm2 was able to achieve surface temperature rises that suggest crystallographic changes on enamel, which could propitiate an increase of acid-resistance of enamel.
Biphoton spectroscopy of YAG:Er3+ crystal
Authors: Kalachev A A , Kalashnikov D A , Kalinkin A A , Mitrofanova T G , Shkalikov A V , Samartsev V V
Published: June 2007

The absorption spectrum of Er3+ ions in YAG crystal in the range from 645 nm to 655 nm was measured with the resolution of 0.01 nm using the frequency-anticorrelated broadband photon pairs (biphotons) generated by spontaneous parametric down-conversion. The spectrum of the sample was measured by counting the coincidences when the impurity crystal was placed in front of the signal photon detector, whilst the wavelength of the idler photons was resolved by a monochromator which was placed in front of another photon detector. The results are in agreement with those obtained by the usual intensity measurements with a classical light source and a monochromator. It was shown experimentally that the biphoton spectroscopy, unlike the usual single photon spectroscopy, allows one to obtain the spectroscopic information in the presence of an external noise such as background thermal radiation.
Diagram of State of Stiff Amphiphilic Macromolecules
Authors: Markov Vladimir A. , Vasilevskaya Valentina V. , Khalatur Pavel G. , ten Brinke Gerrit , Khokhlov Alexei R.
Published: June 2007

Summary: We studied coil‐globule transitions in stiff‐chain amphiphilic macromolecules via computer modeling and constructed phase diagrams for such molecules in terms of solvent quality and persistence length. We showed that the shape of the phase diagram essentially depends on the macromolecule degree of polymerization. Relatively short amphiphilic molecules always form a spherical globule in a poor solvent, and the coil‐globule transition includes one or two intermediate conformations, depending on the chain's stiffness. These are a disk‐like globule in case of high enough Kuhn segment length, and a pearl necklace‐like structure of spherical micelles and a disk‐like globule in case of relatively flexible chains. The phase diagram of a long stiff amphiphilic chain was found to be more complex still. Thus three specific regions can be distinguished in the poor solvent region, depending on the chain stiffness. These correspond to a cylindrical globule without any specific backbone ordering, a cylindrical globule containing blobs with collagen‐like ordering of the chain, and co‐existence of collagen‐like and toroidal globules. In the intermediate transition region in this case, apart from the pearl necklace‐like conformations with spherical micelles, necklace conformations can be also observed where the polymeric chain has collagen‐like ordering within each bead.
Evolutionary Approach in Copolymer Sequence Design
Authors: Khalatur Pavel G. , Khokhlov Alexei R. , Krotova Maria K.
Published: June 2007

Summary: In this work, we discuss a simple evolutionary algorithm that introduces a “selection pressure” under which two‐letter (AB) copolymer sequences can mutate and transform into the sequences tuned to microphase separation transition (MIST). In particular, we are interested in determining how a sequence of A and B units should be organized in order to reach maximum length scale for MIST at a given AB composition. It is found that such sequences are similar to those known for tapered or gradient copolymers exhibiting strong composition inhomogeneity along their chain. The problems of the evolution of copolymer sequences are considered from the viewpoint of emerging of information complexity in the sequences in the course of this evolution.
Ordering of Diblock Copolymer Materials on Patterned Substrates: a Single Chain in Mean Field Simulation Study
Authors: Müller Marcus , Daoulas Kostas
Published: June 2007

Summary: The directed assembly of diblock copolymers on patterned substrates is a way to create nanoscopically structured materials. We study the structure and kinetics of diblock copolymers on patterned substrates by simulating a large ensemble of independent chains in an external field. This external field depends on the density created by the ensemble of molecules and it is frequently updated as to mimic the instantaneous interactions of a molecule with its neighbors. This approximate, particle‐based field theoretical method allows (i) to incorporate arbitrary chain architecture (ii) to include fluctuations and (iii) the explicit propagation of the chain conformations in time permits us to study the kinetics of structure formation. The factors that control the accuracy of the method are quantitatively discussed and the reconstruction of the soft morphology at substrate patterns that deviate from the periodic morphology of the diblock in the bulk are illustrated.
Theory of Liquid‐crystalline Ordering in Polymer Brushes
Authors: Mercurieva Anna A. , Birshtein Tatiana M. , Amoskov Victor M.
Published: June 2007

Summary: We present a review of the works devoted to investigation of LC ordering in polymer brushes. This series has been carried out by the group of T. M. Birshtein and covers the following aspects of the problem: thermotropic LC phase transition in LCP brushes, microphase segregation, homeotropic and planar LC phases, LC polymer in LC solvent, lyotropic LCP brushes, LC transitions under normal or lateral force (shear flow). Analytical theory is developed for simplified model of polymer brush with accounting for thermotropic attraction in Mayer‐Saupe approximation and lyotropic repulsion in DiMarzio formalism; numerical calculations are fulfilled in self‐consistent field approximation (method of Scheutjens and Fleer). Brownian dynamics simulations are applied for modeling polymer brush in a shear flow.
Fluctuating Interfaces in Liquid Crystals
Authors: Schmid Friederike , Germano Guido , Wolfsheimer Stefan , Schilling Tanja
Published: June 2007

Summary: We review and compare recent work on the properties of fluctuating interfaces between isotropic and nematic liquid‐crystalline phases. Molecular dynamics and Monte Carlo simulations have been carried out for systems of ellipsoids and hard rods with aspect ratio 15:1, and the fluctuation spectrum of interface positions (the capillary wave spectrum) has been analyzed. In addition, the capillary wave spectrum has been calculated analytically within the Landau‐de Gennes theory. The theory predicts that the interfacial fluctuations can be described in terms of a wave vector dependent interfacial tension, which is anisotropic at small wavelengths (stiff director regime) and becomes isotropic at large wavelengths (flexible director regime). After determining the elastic constants in the nematic phase, theory and simulation can be compared quantitatively. We obtain good agreement for the stiff director regime. The crossover to the flexible director regime is expected at wavelengths of the order of several thousand particle diameters, which was not accessible to our simulations.
Hierarchical Modeling of Entangled Polymers
Authors: Ramírez Jorge , Sukumaran Sathish K. , Likhtman Alexei E.
Published: June 2007

Summary: We demonstrate that it is possible to link multi‐chain molecular dynamics simulations with the tube model using a single chain slip‐links model as a bridge. This hierarchical approach allows significant speed up of simulations, permitting us to span the time scales relevant for a comparison with the tube theory. Fitting the mean‐square displacement of individual monomers in molecular dynamics simulations with the slip‐spring model, we show that it is possible to predict the stress relaxation. Then, we analyze the stress relaxation from slip‐spring simulations in the framework of the tube theory. In the absence of constraint release, we establish that the relaxation modulus can be decomposed as the sum of contributions from fast and longitudinal Rouse modes, and tube survival. Finally, we discuss some open questions regarding possible future directions that could be profitable in rendering the tube model quantitative, even for mildly entangled polymers.
The Viscoelastic Coarse‐Grained Dynamic Model of the Polymer Network with Embedded Rod‐Like Particles. Relaxation Spectra and Mobility of Different Scales.
Authors: Gotlib Yuli Ya. , Torchinskii Isaak A. , Toshchevikov Vladimir P. , Shevelev Vladimir A.
Published: June 2007

Summary: The viscoelastic coarse‐grained dynamic model of a polymer network with rod‐like particles included into the network is considered. The rods are regularly distributed in the network. The entanglements of rods in a polymer network lead to quasielastic interactions between the rods and network fragments. The structure of the relaxation spectrum is considered. The dependence of the relaxation properties of the network with included rods on the viscoelastic parameters of the network without rods, on the length and the friction of the rods are investigated at different strength of the interaction between rods and network fragments. The differences between collective types of relaxation of the rods and the network and localized motions of the rods on the background of immobile network fragments are discussed. The results of the theory are applied to the description of the rotational and translational motions of the rods appearing in dielectric relaxation, NMR and other phenomena.
Molecular Dynamics of Pectin Extension
Authors: Neelov Igor , Adolf David , McLeish Tom
Published: June 2007

Summary: A pectin 10mer under constant pulling speed and constant force was studied using the atomistic simulations. Molecular dynamics (MD) with the Amber99 and Amber‐Glycam04 forcefields were performed. The main result of the present Amber‐based MD simulations is that the two plateaux of the experimental force‐ extension dependence for pectin can be explained by transitions between three conformational states of pectin monomer ring (first from a chair (4C1) to boat conformation and second from boat to an inverted chair (1C4) conformation). A multi‐state dynamical model of single biopolymer extension under external force was elaborated and applied to extension of polymers with three‐state monomers relevant to pectin.
Models and mechanisms in malignant melanoma
Authors: Benjamin Cara L. , Melnikova Vladislava O. , Ananthaswamy Honnavara N.
Published: June 2007

Human melanoma represents the fastest growing malignancy in the US. The etiology of melanoma is highly debated as is the role of ultraviolet (UV) radiation in the initiation and progression of melanoma. This article discusses data from UV exposure and its relationship to the development of melanoma from various models of melanoma as well as various genetic alterations seen in oncogenic transformation of melanocytes. Genetic alterations such as the p16INK4a deletion, melanocortin 1 receptor (MC1R), RAS, and v‐raf murine sarcoma viral oncogene homolog B1 (BRAF) may be indicative of a predisposition to melanoma development. Historical research as well as current data on the significance of the hot spot mutation in BRAF is discussed in its relative potential to the activating mutation in RAS. © 2007 Wiley‐Liss, Inc.
Reinforcement of a thin plate by a thin layer
Authors: Rahmani Leila , Vial Grégory
Published: June 2007

We study the bending of a thin plate, stiffened with a thin elastic layer, of thickness δ. We describe the complete construction of an asymptotic expansion with respect to δ of the solution of the Kirchhoff–Love model and give optimal estimates for the remainder. We identify approximate boundary conditions, which take into account the effect of the stiffener at various orders. Thanks to the tools of multi‐scale analysis, we give optimal estimates for the error between the approximate problems and the original one. We deal with a layer of constant stiffness, as well as with a stiffness in δ−1. Copyright © 2007 John Wiley & Sons, Ltd.
1H and 13C NMR spectra of methylmaleimido‐ and methylsuccinimidoanthranilate esters of 1‐hydroxymethyl‐6‐methoxy‐3‐azabicyclo[3.3.1]nonanes
Authors: Goodall Kirsten J. , Brimble Margaret A. , Barker David
Published: June 2007

The 1H and 13C NMR data for 3‐azabicyclo[3.3.1]nonanes having C‐1 methylsuccinimidoanthranilate esters and C‐6 methyl ethers were measured and assigned using 1D (DEPT) and 2D (COSY, HSQC, HMBC, NOESY) experiments. Comparison of this with previously published data illustrates the effects of stereochemistry and substitution on the basic heterocyclic framework. Copyright © 2007 John Wiley & Sons, Ltd.
Xylocarpins A and B, two new mexicanolides from the seeds of a Chinese mangrove Xylocarpus granatum: NMR investigation in mixture
Authors: Li Minyi , Wu Jun , Zhang Si , Xiao Qiang , Li Qingxin
Published: June 2007

Xylocarpins A and B, two new mexicanolides with a tiglate group at C‐3, have been identified in the mixture using NMR spectroscopy. Both compounds were isolated in the mixture from the seeds of a Chinese mangrove Xylocarpus granatum. The first complete assignments of 1H and 13C NMR data for these mexicanolides were achieved by means of 2D NMR techniques, including 1H1H COSY, HSQC, HMBC and NOESY spectra. In order to separate xylocarpins A (1) and B (2) by chemical method, the mixture of two compounds was reduced with sodium borohydride in anhydrous methanol. However, the reduction led to the opening of the δ‐lactone ring in xylocarpin B and afforded compound 3 as the main product. The complete NMR assignments of compound 3 were also achieved by means of the above 2D NMR techniques. Moreover, xylocarpin A was easily transformed into xylocarpin B during our normal liquid column chromatography. From this point of view, xylocarpin A was deemed to be the genuine natural product and xylocarpin B might be an artifact. Copyright © 2007 John Wiley & Sons, Ltd.
The 1‐minimax and 1‐maximin problems with demand weights of general probability distributions
Authors: Berman Oded , Wang Jiamin
Published: June 2007

This paper investigates the 1‐minimax and 1‐maximin problems when demand weights are random variables with general continuous probability distributions. Properties of the optimal solutions are presented and solution procedures are developed. We also identify some known probability distributions under which it is easier to search for an optimal solution. © 2007 Wiley Periodicals, Inc. NETWORKS, Vol. 50(2), 127–135 2007
Panpositionable hamiltonicity of the alternating group graphs
Authors: Teng Yuan‐Hsiang , Tan Jimmy J.M. , Hsu Lih‐Hsing
Published: June 2007

The alternating group graph AGn is an interconnection network topology based on the Cayley graph of the alternating group. There are some interesting results concerning the hamiltonicity and the fault tolerant hamiltonicity of the alternating group graphs. In this article, we propose a new concept called panpositionable hamiltonicity. A hamiltonian graph G is panpositionable if for any two different vertices x and y of G and for any integer l satisfying d(x,y) ≤ l ≤ ∣V(G)∣−d(x,y), there exists a hamiltonian cycle C of G such that the relative distance between x, y on C is l. We show that AGn is panpositionable hamiltonian if n ≥ 3. © 2007 Wiley Periodicals, Inc. NETWORKS, Vol. 50(2), 146–156 2007
Applications of high‐resolution schemes based on normalized variable formulation for 3D indoor airflow simulations
Authors: Ng K. C. , Ng E. Y. K. , Yusoff M. Z. , Lim T. K.
Published: June 2007

Computational fluid dynamics (CFD) has been used in a routine manner for the design of indoor environments. The quality of these CFD studies varies from poor to excellent, and only in year 2003 Sørensen and Nielsen recommend a detailed guideline
on imposing quality control in the CFD‐related works for indoor airflow simulations. One of these recommendations is to use monotone high‐resolution (HR) schemes that apply flux limiters to ensure solution boundedness while preserving the high‐order accuracy of the differencing schemes. In this paper, based on the
γ‐formulations derived from the normalized variable formulation, four recently developed HR schemes, GAMMA, CUBISTA, AVLSMART and HOAB, are applied to several indoor airflow problems such as (1) Smith–Hutton problem (dead‐end channel); (2) forced convection problem (horizontal/oblique inflow) in a parallelepiped room; (3) mixing ventilation problem focusing on the prediction of local mean age of air; (4) flow in a two‐room chamber with internal partition and (5) displacement ventilation in a mockup office. Based on the flow results, the aspects of accuracy and robustness of these HR schemes are addressed for appropriate selection of an ‘ideal’ differencing scheme to improve the quality of 3D indoor CFD calculations. Copyright © 2007 John Wiley & Sons, Ltd.
A numerical procedure to solve non‐linear kinematic problems in spatial mechanisms
Authors: Petuya V. , Gutiérrez J. M. , Alonso A. , Altuzarra O. , Hernández A.
Published: June 2007

This paper presents a numerical method to solve the forward position problem in spatial mechanisms. The method may be incorporated in a software for the kinematic analysis of mechanisms, where the procedure is systematic and can be easily implemented, achieving a high degree of automation in simulation. The procedure presents high computational efficiency, enabling its incorporation in the control loop to solve the forward position problem in the case of a velocity control scheme. Also, in this paper preliminary results on the convergence of the proposed procedure are shown, and efficiency results of the method applied to representative spatial mechanisms are presented. Copyright © 2007 John Wiley & Sons, Ltd.
Orthogonal spline collocation methods for the stream function‐vorticity formulation of the Navier–Stokes equations
Authors: Fairweather Graeme , Ma Heping , Sun Weiwei
Published: June 2007

An orthogonal spline collocation (OSC) spatial discretization is proposed for the solution of the fully coupled stream function‐vorticity formulation of the Navier–Stokes equations in two dimensions. For the time‐stepping, a three‐level leapfrog scheme is employed. This method is algebraically linear, and, at each time step, gives rise to a system of linear equations of the form arising in the OSC approximation of the biharmonic Dirichlet problem and can be solved by a fast direct method. Error estimates in the Hl–norm in space, l = 1,2, are derived for the semi‐discrete method and the fully‐discrete leapfrog scheme which is also shown to be second order accurate in time. Numerical results are presented which confirm the theoretical analysis and exhibit superconvergence phenomena, which provide superconvergent approximations to the components of the velocity. © John Wiley & Sons, Inc. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2008
Safety, efficacy, and immune reconstitution after rituximab therapy in pediatric patients with chronic or refractory hematologic autoimmune cytopenias
Authors: Rao Aarati , Kelly Michael , Musselman Mark , Ramadas Jagadeesh , Wilson David , Grossman William , Shenoy Shalini
Published: June 2007

Background

Autoimmune hematologic cytopenias in children often require therapeutic intervention. We report a prospective pediatric multicenter trial of rituximab for refractory or steroid‐dependent patients.

Methods

Four doses of rituximab (375 mg/m2/dose) were administered weekly. Patients without response after three doses were offered dose escalation to 750 mg/m2/dose/week × 3. Safety, efficacy, and immunologic tests were evaluated after therapy.

Results

Twenty‐nine of 30 children (2–18 years) with thrombocytopenia (21), hemolytic anemia (6), Evans syndrome (2), and neutropenia (1) received at least four doses of rituximab. One developed anaphylaxis with the first dose. One patient was subsequently diagnosed with monosomy 7 myelodysplasia. Of 28 remaining patients, 9 received dose escalation. Responders discontinued other therapy following rituximab. The overall response rate was 72% with median follow‐up of 18 months. Complete remission was observed in 14 (50%); all received four doses of rituximab. Partial remission (PR) was observed in six (22%); five had received dose escalation. Of four relapses, 4–24 months after therapy, two were retreated with rituximab and achieved second remission. No major infections were encountered. Circulating B‐cells were depleted by 1 month and normalized by 1 year. IgM, Ig A, and IgG levels decreased 6, 9, and 12 months after therapy, respectively, but remained near normal range. Tetanus toxoid antibody titers remained detectable.

Conclusions

Rituximab was well tolerated, and induced sustained remissions in children with refractory immune cytopenias. Dose escalation and re‐treatment after relapse elicited additional responses. Rituximab therapy should be considered prior to potential interventions with higher toxicity. Pediatr Blood Cancer 2008;50:822–825. © 2007 Wiley‐Liss, Inc.
Adherence to multiple drug therapies: refill adherence to concomitant use of diabetes and asthma/COPD medication
Authors: Krigsman Kristin , Nilsson J. Lars G. , Ring Lena
Published: June 2007

Purpose

To investigate whether patients with drugs for two chronic diseases, type 2 diabetes and asthma/chronic obstructive pulmonary diseases (COPD), showed the same refill adherence pattern in relation to their drug treatments during a 3‐year period.

Methods

Patients 50 years and older who had been dispensed diabetes and asthma/COPD drugs in the county of Jämtland during 2001–2003 were included. The refill adherence was calculated based either on prescribed dosage or defined daily dose (DDD). A patient profile graph for each patient was constructed including the date of each dispensation and the time period covered by the dispensed drugs. For each patient, the dispensation pattern and the treatment persistency over time were determined.

Results

In total, 56 patients were included in the study. Satisfactory refill adherence was found for 68% of the repeat prescriptions for diabetes drugs and for 42% of the repeat prescriptions for asthma/COPD drugs. About half (52%; 29/56) of the patients showed the same dispensation patterns for both diabetes and asthma/COPD drugs, and 86% (25/29) of these patients had a satisfactory refill adherence. However, there was no correlation or agreement regarding the dispensation patterns for diabetes and asthma/COPD drugs.

Conclusions

Patients showed higher refill adherence for their diabetes drugs than their asthma/COPD drugs. Our hypothesis that patients with satisfactory refill adherence to antihyperglycaemic drugs would also have satisfactory refill adherence to asthma/COPD drugs, was not supported. Copyright © 2007 John Wiley & Sons, Ltd.
Surface and thermodynamic parameters of polymeric surfactants from recycled poly(ethylene terephthalate)
Authors: Atta Ayman M
Published: June 2007

Poly(ethylene terephthalate) waste was recycled to oligomers in the presence of diethanolamine and manganese acetate as a catalyst. The oligomers produced were reacted with stearic acid and poly(ethylene glycol) with different number average molecular weights of 400, 1000 and 4000 g mol−1 to produce nonionic polymeric surfactants having different hydrophile–hydrophobe balances. The surface tension, critical micelle concentration and surface activities were determined at different temperatures. Surface parameters such as surface excess concentration (Γmax), the area per molecule at interface (Amin) and the effectiveness of surface tension reduction (ΠCMC) were determined from the adsorption isotherms of the prepared surfactants. Some thermodynamic data for the adsorption process were calculated and are discussed. Copyright © 2007 Society of Chemical Industry
Correlation of chemical shrinkage of polyacrylonitrile fibres with kinetics of cyclization
Authors: Simitzis Johannis , Soulis Spyridon
Published: June 2007

It has been established that the most important step in the production of carbon fibres from polyacrylonitrile (PAN) precursor fibres is the oxidative thermal treatment applied. During this treatment, physical phenomena and chemical reactions take place accompanied by the shrinkage of the fibres, which has a physical or chemical origin, depending on the nitrile cyclization reactions. The aim of the present study is to establish a correlation between the chemical shrinkage of PAN fibres and the kinetics of cyclization reactions. Based on the isothermal treatment of PAN fibres, we developed a method in order to distinguish between physical and chemical shrinkages. The onset time for the chemical shrinkage follows a relationship with temperature. Chemical shrinkage versus cyclization time data were fitted with the exponential rise to the maximum of the curves. Furthermore, the cyclization kinetics was studied using differential scanning calorimetry and the kinetic parameters determined were identical to those calculated from the chemical shrinkage, demonstrating that the latter is directly related to the kinetics of the cyclization reactions. It was therefore concluded that according to the method developed to distinguish the physical from the chemical shrinkages: (1) there exists a certain onset time for a given treatment temperature to trigger the chemical shrinkage; (2) cyclization reactions do not start below a limiting temperature of 168 °C; (3) at 340 °C, the temperature where the cyclization reactions are completed, the maximum shrinkage is 24%; and (4) the oxidized PAN fibres contain mainly ladder polymer structures with approximately symmetrical sequences connected in angled positions. Copyright © 2007 Society of Chemical Industry
An improved method of sample preparation on AnchorChip™ targets for MALDI‐MS and MS/MS and its application in the liver proteome project
Authors: Zhang Xumin , Shi Liang , Shu Shaokung , Wang Yuan , Zhao Kang , Xu Ningzhi , Liu Siqi , Roepstorff Peter
Published: June 2007

An improved method for sample preparation for MALDI‐MS and MS/MS using AnchorChip™ targets is presented. The method, termed the SMW method (sample, matrix wash), results in better sensitivity for peptide mass fingerprinting as well as for sequencing by MS/MS than previously published methods. The method allows up‐concentration and desalting directly on the mass spectrometric target and should be amenable for automation. A draw back caused by extensive oxidation of methionine and tryptophan in the SMW method can be alleviated by the addition of n‐octyl glucopyranoside and DTT to the sample solution. The method was validated for protein identification from a 2‐DE based liver proteome study. The SMW method resulted in identification of many more proteins and in most cases with a better score than the previously published methods.
Proteomic analysis of core breakdown disorder in Conference pears (Pyrus communisL.)
Authors: Pedreschi Romina , Vanstreels Els , Carpentier Sebastien , Hertog Maarten , Lammertyn Jeroen , Robben Johan , Noben Jean‐Paul , Swennen Rony , Vanderleyden Jozef , Nicolaï Bart M.
Published: June 2007

2‐DE was applied to study core breakdown disorder in controlled atmosphere stored ’︁Conference' pears. This physiological disorder is characterized by internal browning of the fruit tissue and the development of cavities. Suitable protein phenol extraction/ammonium acetate‐methanol precipitation and 2‐DE protocols for a wide pH range were established for pear tissue. The protein expression profiles of healthy, sound (intact tissue of pears with core breakdown) and brown tissue were analyzed with the univariate non‐parametric Kolmogorov‐Smirnov test and multivariate statistical techniques such as principal component analysis and partial least square discriminant analysis. Both statistical approaches revealed interesting differentially expressed proteins between healthy and disordered pears. LC‐ESI‐MS/MS identification of differentially expressed proteins between healthy and sound tissue revealed their participation in the energy metabolism, the antioxidant system and ethylene biosynthesis. Up‐regulated characteristic proteins in brown tissue were mainly involved in energy metabolism and defense mechanisms. Proteomics coupled to univariate and multivariate statistical techniques seems to be an efficient approach to get a better insight into the different mechanisms and pathways leading to the core breakdown disorder.
Efficient on‐chip proteolysis system based on functionalized magnetic silica microspheres
Authors: Li Yan , Yan Bo , Deng Chunhui , Yu Wenjia , Xu Xiuqing , Yang Pengyuan , Zhang Xiangmin
Published: June 2007

An easily replaceable enzymatic microreactor has been fabricated based on the glass microchip with trypsin‐immobilized magnetic silica microspheres (MS microspheres). Magnetic microspheres with small size (∼300 nm in diameter) and high magnetic responsivity to magnetic field (68.2 emu/g) were synthesized and modified with tetraethyl orthosilicate (TEOS). Aminopropyltriethoxysilane (APTES) and glutaraldehyde (GA) were then introduced to functionalize the MS microspheres for enzyme immobilization. Trypsin was stably immobilized onto the MS microspheres through the reaction of primary amines of the proteins with aldehyde groups on the MS microspheres. The trypsin‐immobilized MS microspheres were then locally packed into the microchannel by the application of a strong field magnet to form an on‐chip enzymatic microreactor. The digestion efficiency and reproducibility of the microreactor were demonstrated by using cytochrome c (Cyt‐C) as a model protein. When compared with an incubation time of 12 h by free trypsin in the conventional digestion approach, proteins can be digested by the on‐chip microreactor in several minutes. This microreactor was also successfully applied to the analysis of an RPLC fraction of the rat liver extract. This opens a route for its further application in top‐down proteomic analysis.
Characterization of proteomic changes in cardiac mitochondria in streptozotocin‐diabetic rats using iTRAQ™ isobaric tags
Authors: Jüllig Mia , Hickey Anthony J. , Middleditch Martin J. , Crossman David J. , Lee Stanley C. , Cooper Garth J. S.
Published: June 2007

Diabetes now affects more than 5% of the world's population and heart failure is the most common cause of death amongst diabetic patients. Accumulating evidence supports a view that myocardial mitochondrial structural and functional changes are central to the onset of diabetic heart failure, but the exact nature of these changes at the proteomic level remains unclear.Here we report on proteomic changes in diabetic rat heart mitochondria following 120 days of streptozotocin‐diabetes using the recently developed iTRAQ™ labeling method, which permits quantification of proteins directly from complex mixtures, bypassing the limitations associated with gel‐based methods such as 2‐DE. Of 252 unique proteins identified, 144 were represented in at least three of six individual paired experiments. Relative amounts of 65 proteins differed significantly between the groups, confirming that the cardiac mitochondrial proteome is indeed impacted by diabetes. The most significant changes were increased protein levels of enzymes involved in mitochondrial oxidation of long‐chain fatty acids, which was also confirmed by enzyme assays, and decreased levels of multiple enzymes involved in oxidative phosphorylation and catabolism of short‐chain fatty acids and branched‐chain amino acids. We also found significant changes in levels of several enzymes linked to oxidative stress.
Recent Advances in the Chemistry of N5+, N5− and High‐Oxygen Compounds
Authors: Christe Karl O.
Published: June 2007

An overview of our work in the areas of polynitrogen and high‐nitrogen and high‐oxygen chemistry is given. Areas of interest include the synthesis and characterization of novel polynitrogen ions, such as N5+ and N5−. Efforts are discussed to combine the N5+ cation with energetic counter‐ions, such as N3−, NO3−, ClO4−, B(N3)4− and P(N3)6−. In the area of high‐oxygen carriers, complex nitrato anions were successfully combined with tetrazolium cations to yield CO/H2O balanced ionic liquids of interest for liquid monopropellants.
An Advanced GAP/AN/TAGN Propellant. Part II: Stability and Storage Life
Authors: Judge Michael D. , Badeen Christopher M. , Jones David E. G.
Published: June 2007

A solid rocket propellant based on glycidyl azide polymer (GAP) binder plasticized with nitrate esters and oxidized with a mixture of ammonium nitrate (AN) and triaminoguanidine nitrate (TAGN) and including non‐lead ballistic modifiers, was formulated. The propellant was designed so as to produce non‐acidic and non‐toxic exhaust products while still providing reasonably good burning rate and impulse. This propellant was characterized with respect to thermal and chemical stability and storage life by a variety of test methods. The data indicate that the propellant exhibits good stability and is suitably safe for prolonged storage. Characterization data for this propellant with regard to processing parameters, tensile properties, and ballistic performance are presented in a companion paper.
A Flow Time Model for Melt‐Cast Insensitive Explosive Process
Authors: Guillemin Jean‐Philippe , Brunet Luc , Bonnefoy Olivier , Thomas Gérard
Published: June 2007

Diphasic flows of concentrated suspensions of melt‐cast insensitive explosives exhibit specific rheological properties. In order to limit the handling of pyrotechnical products presenting a risk with respect to the mechanical and thermal shocks, a lot of work has been undertaken for many years in the civil engineering sector. The objective of this study is to propose a predictive model of the flow time of a concentrated suspension through a nozzle located at the bottom of a tank. Similar to our industrial process, the suspension is made out of insensitive energetic materials and flows under gravity. Experimental results are compared to three models (Quemada, Krieger‐Dougherty, and Mooney) predicting the viscosity μ of a suspension as a function of the solid volume fraction ϕ, the maximum packing density ϕm and the viscosity μ0 of the interstitial liquid. De Larrard's model is used to calculate ϕm. The value of viscosity measured for the pure liquid is close to the one predicted by the Bernoulli theorem, where liquids are considered as incompressible and inviscid. Finally, it was found that the Quemada's model gives a fair agreement between predictions and experiments.
The impact of birth weight on prostate cancer incidence and mortality in a population‐based study of men born in 1913 and followed up from 50 to 85 years of age
Authors: Eriksson Margaretha , Wedel Hans , Wallander Mari‐Ann , Krakau Ingvar , Hugosson Jonas , Carlsson Sture , Svärdsudd Kurt
Published: June 2007

BACKGROUND

Insulin‐like growth factor‐I (IGF‐I) hormone is directly associated with birth weight (BW), and high IGF‐I measured in adults is associated with increased risk of prostate cancer (PCA). Whether BW and PCA are related is inconclusive to date.

METHODS

BW and PCA incidence and mortality data for a population‐based cohort of 1,436 singleton Swedish men born in 1913 and followed until 85 years of age were obtained.

RESULTS

BW ≥ 4,250 g was associated with significantly higher PCA incidence [62% (CI: 4%–151%)] and PCA mortality [82% (CI: 3%–221%)] than BW 3,001–4,249 g, even when other potential effect modifiers were taken into account. The hazards ratio for PCA incidence fell from approximately 3 at age 50 to unity at age 85. Approximately one out of every six PCA incident cases between 50 and 70 years of age could be attributed to BW ≥ 4,250 g.

CONCLUSIONS

In the current study PCA incidence and mortality rate appears to increase with BW. Prostate 67: 1247–1254, 2007. © 2007 Wiley‐Liss, Inc.
Propanil and swep inhibit 4‐coumarate:CoA ligase activity in vitro
Authors: Yun Min‐Soo , Chen Weijun , Deng Fan , Yogo Yasuhiro
Published: June 2007

4‐Coumarate:CoA ligase (4CL, EC 6.2.1.12) in the phenylpropanoid pathway in plants has attracted interest as a novel target for developing effective plant growth inhibitors (PGIs). In a previous study in which the 4CL inhibitory activity of 28 existing herbicides was investigated using an optimized in vitro screening assay, 4CL activity was found to be strongly inhibited by propanil and swep at 100 µM. Here, further experimental evidence is provided to substantiate the previous result. Using 4‐coumaric acid as substrate, tobacco 4CL activity was inhibited by propanil or swep in a concentration‐dependent manner, with 50% inhibition concentrations (I50) of 39.6 and 6 µM respectively. These herbicides also exhibited uncompetitive inhibition towards 4‐coumaric acid. Furthermore, 4CLs from several plant species were inhibited by the herbicides within a range from 1 to 50 µM. It is proposed that these herbicides have another site of action as a result of the inhibition of 4CL in the phenylpropanoid pathway, and this enzyme represents a new target site for the development of PGI. Copyright © 2007 Society of Chemical Industry
Efficient three‐wave mixing via intersubband transitions in a semiconductor quantum well
Authors: Li Jiahua
Published: June 2007

We put forward an efficient three‐wave mixing (TWM) scheme in an asymmetric semiconductor quantum well (SQW) based on intersubband transitions. Using the coupled Schrödinger–Maxwell approach, we derive the corresponding explicit analytical expressions for the input probe and generated TWM signal fields. Such a nonlinear optical process may be used for efficiently generating coherent short‐wavelength radiation in the SQW solid‐state system, which is much more practical than that in atomic system because of its flexible design and the controllable interference strength. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Low‐refractive‐index materials: A new class of optical thin‐film materials
Authors: Schubert E. F. , Kim J. K. , Xi J.‐Q.
Published: June 2007

The refractive index, a most fundamental quantity in optics and optoelectronics, determines many figures of merit of optical components such as reflectors, filters, and resonators. Here we present a new class of optical thin‐film materials that have a very low refractive index. Specular films of high optical quality with refractive indices as low as 1.05 are demonstrated. A single pair DBR incorporating low‐n material is demonstrated to have enhanced reflectivity, showing the great potential of low‐refractive‐index films for many photonic device applications. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Direct synthesis of II–VI compound nanocrystals in polymer matrix
Authors: Antolini F. , Di Luccio T. , Laera A. M. , Mirenghi L. , Piscopiello E. , Re M. , Tapfer L.
Published: June 2007

The production of II–VI semiconductor compound – polymer matrix nanocomposites by a direct in‐situ thermolysis process is described. Metal‐thiolate precursor molecules embedded in a polymer matrix decompose by a thermal annealing and the nucleation of semiconductor nanocrystals occurs. It is shown that the nucleation of nanoparticles and the formation of the nanocomposite can be also achieved by laser beam irradiation; this opens the way towards a “lithographic” in‐situ nanocomposite production process. A possible growth and nanocomposite formation mechanism, describing the structural and chemical transformation of the precursor molecules, their decomposition and the formation of the nanoparticles, is presented. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrostatic electron piston pump with in‐plane gate transistors
Authors: Draghici M. , Salloch D. , Melnikov A. , Wieck A. D.
Published: June 2007

We have demonstrated an electron pump with in‐plane gate (IPG) transistors fabricated by focused ion beam (FIB) implantation on GaAs–Alx Ga1–x As modulation‐doped heterostructure with a two‐dimensional electron gas (2DEG). The maskless fabrication process does not require any alignment between the circuit elements including the sources, the drains and the gates of the IPG transistors. Although, the device is operating at low frequencies (tens of kHz), it is capable to produce a current more than one order of magnitude higher than other electron pumps based on Coulomb blockade and single electron tunneling effects. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Progress in the growth of nonpolar gallium nitride
Authors: Haskell B. A. , Nakamura S. , DenBaars S. P. , Speck J. S.
Published: June 2007

The active regions of conventional c ‐plane (Al,In,Ga)N optoelectronic devices suffer from deleterious polarization effects. These polarization effects can be eliminated by growing devices on alternative GaN planes, such as {1$ \bar 1 $00} m ‐plane or {11$ \bar 2 $0} a ‐plane films. Previous attempts to grow nonpolar GaN by vapor phase and molecular beam epitaxy methods yielded rough and faceted surfaces that were unsuitable for device use. Beginning with Waltereit et al.'s work [Nature 406, 865 (2000)], significant progress has been made in improving nonpolar GaN structural quality and morphology. This paper reviews the structural and morphological characteristics of planar, nonpolar a ‐plane and m ‐plane GaN films grown by vapor phase and molecular beam epitaxy techniques. Defect reduction via lateral epitaxial overgrowth, and the influence of extended defects on surface morphology will be further discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Confidence intervals for the comparison of variability estimates for a mixed model
Authors: Daniels Lorraine , Borror Connie M. , Burdick Richard K.
Published: June 2007

In this paper, we develop methods for generating confidence intervals for the comparison of variability estimates in a mixed‐effects model. A generalized confidence interval (GCI) is developed and contrasted to the modified large sample (MLS) method with an adjustment for a fixed effect. The methods are assessed using a computer simulation. Recommendations are provided for selecting an appropriate method. Copyright © 2007 John Wiley & Sons, Ltd.
Monitoring autocorrelated processes using variable sampling schemes at fixed‐times
Authors: Zou Changliang , Wang Zhaojun , Tsung Fugee
Published: June 2007

Traditional control charts for process monitoring are based on taking samples of fixed size from the process using a fixed sampling interval. A recent development in control charts is the use of adaptive control charts, i.e. the variable sampling interval (VSI) and variable sampling size charts. This paper extends this idea to the autocorrelated process. We consider a time series model which is a first‐order autoregressive process plus a random error. With variable intervals, the sampling time may be inconvenient, so using only two intervals, referred to as ‘variable sampling interval at fix times’ makes the method easier to use in practice. The sampling rate can also be adjusted by the number of samples collected, VSRFT, for ‘variable sampling rate at fixed times’. We
study what we call ‘variable sampling at fixed times’, VSFT, which includes both VSIFT and VSRFT schemes, using a Markov chain model and integral equations. We show that our methods detect process shifts faster, on average, than fixed sampling X‐bar charts, and at least comparable detection ability with the less practical VSI charts. Copyright © 2007 John Wiley & Sons, Ltd.
Flavonoid profile in soybeans by high‐performance liquid chromatography/tandem mass spectrometry
Authors: Cavaliere Chiara , Cucci Francesca , Foglia Patrizia , Guarino Chiara , Samperi Roberto , Laganà Aldo
Published: June 2007

Flavonoid profiling of a soybean sample has been performed by liquid chromatography/positive electrospray tandem mass spectrometry (LC/ESI+‐MS/MS) using a quadrupole‐linear ion trap (QLIT) instrument with an information‐dependent data acquisition (IDA) protocol that looped, in a single run, an enhanced MS scan and an enhanced product ion scan. As compromise between time and obtainable information, spectra acquisition was split into two distinct runs: 220–450 Th and 400–800 Th, respectively. The isoflavones daidzein and genistein were identified as aglycones, monoglycosides, diglycosides, triglycosides, acetylglycosides, malonylglycosides, malonyl diglycosides, and dimalonyl diglycosides, whereas glycitein triglycosides, acetylglycosides, and dimalonyl diglycosides were not detected. Also kaempferol di‐ and triglycosides, malonylglycosides and malonyl diglycosides, previously reported in soy leaves and pods, and four naringenin malonylglycosides were identified. Copyright © 2007 John Wiley & Sons, Ltd.