bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractSummary: 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

AbstractSummary: 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

AbstractSummary: 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

AbstractSummary: 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

AbstractSummary: 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

AbstractSummary: 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

AbstractSummary: 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

AbstractSummary: 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

AbstractHuman 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

AbstractWe 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

AbstractThe 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

AbstractXylocarpins 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

AbstractThis 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

AbstractThe 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

AbstractComputational 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

AbstractThis 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

AbstractAn 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

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

AbstractPurposeTo 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.MethodsPatients 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.ResultsIn 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.ConclusionsPatients 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

AbstractPoly(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