bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular dynamics in nanostructured polyimide‐silica hybrid materials and their thermal stability
Authors: Bershtein Vladimir A. , Egorova Larisa M. , Yakushev Pavel N. , Georgoussis George , Kyritsis Apostolos , Pissis Polycarpos , Sysel Petr , Brozova Libuse
Published: March 2011

Molecular motion and thermal stability in two series of nanophase‐separated polyimide‐silica (PI‐SiO2) hybrid networks with chemically bound components were studied. The hybrids were prepared via a sol‐gel process and differed in PI structure and chain length, and in SiO2 content ranging from 10 to 50 wt.%. Differential scanning calorimetry, laser‐interferometric creep rate spectroscopy, dielectric relaxation spectroscopy, thermally stimulated depolarization current techniques, and thermogravimetry were used covering, on the whole, the ranges of 100–900 K and 10−3‐109 Hz. Silica domains influenced PI dynamics in two opposite directions. Loosened segmental packing in chains confined to nanovolumes resulted mainly in rise of small‐scale motion below β‐relaxation region, while anchoring of chain ends to ‘rigid walls’ caused, contrarily, a partial or total suppression of segmental motion above Tβ, especially drastically at the temperatures close to and within glass transition. The latter resulted in a large change in thermal stability, e.g., 2.5‐fold increasing of the apparent activation energy of thermooxidative degradation, and more than 100° rise of predicted long‐term thermal stability for the hybrids as compared to that for PI.
The comparison of relaxation events with spectroscopic properties of polymer composites with fibrillar dopings on the basis of low density polyethylene and polypropylene
Authors: Mamedov Shaval V. , Alekperov Vilayet A. , Ozcanh Yesim
Published: March 2011

In this study, the mechanical and electrical degradation properties of the composites of polypropylene (PP)+PP fibers, low‐density polyethylene(LDPE)+PP fiber, and PP+fiber glass have been investigated and the validity of Zhourkov's thermofluctuation theory has been shown.
Alternative theory of hydrodynamic interactions in polymer solutions
Authors: Borodin Igor P. , Khazanovich Teodor N.
Published: March 2011

The model is presented for coarse grained dynamics of macromolecules in dilute solutions. The coarse graining is achieved by dividing the polymer chain into subchains, consisting of many monomers, and spatial averaging over lengths that are large compared to the mean‐square end‐to‐end distance of subchains and small compared to macromolecule size. Kinetic equations of the model are derived from first principles of statistical mechanics under the assumption that subchain center of mass positions and solvent flow velocity field are the only slow variables of the system. In this approach hydrodynamic interactions result from the intercomponent friction forces between polymer and solvent instead of boundary conditions on the bead surfaces as in traditional theories. The integrodifferential diffusion equation is obtained for steady flows with the kernel involving the Oseen tensor multiplied by equilibrium distribution in the space of the subchain center of mass positions.
Computer modelling of structure and dynamics of C‐50 n‐paraffin crystal, hexagonal phase of C‐50 crystal and ethylene/propylene statistical copolymers
Authors: Oleinik Eduard , Karmilov Ilya , Shenogin Sergei , Kalashnikov Alexander , Mazo Michael , Balabaev Nikolai , Chvalun Sergei
Published: March 2011

3D crystal of n‐paraffin C‐50 was created by computer molecular dynamics method. The crystal consists of 48 chain molecules containing 48 ‐CH2‐groups and two ‐CH3 end groups each. Constant temperature‐constant pressure calculations, spatially periodic boundary conditions, integration step 0.001 ps were used. Chemical bonds were treated as absolutely rigid, bond angles bending were treated trough U(θ)=½Kθ(θ‐θ0)2 function and torsion rotations trough Uφ=Cφ/2[1+Zφ(3cos3(φ)‐2cos(φ))] function. Non‐bonded interactions were represented as truncated and shifted L‐D 6–12 potential function. All atoms were introduced explicitly. At 200K and 36 ps of relaxation we got computer C‐50 crystal with orthorhombic symmetry (o‐phase) and cell parameters a=7,416Å, b=4,723Å, c=2,625Å and density ρ=1,014 g/cm3 which are close to known from literature. Heating of the crystal up to 450K have shown thermal expansion along all crystallographic axes well coinciding with known experiment. At 400K the system posses transition to hexagonal phase (h‐phase). At 450K the crystal melts, but high orientation of chain axes still exists in the system. Analysis of rotational and translation mobility of h‐phase at 400K have shown that all chains undergo fast rotation around chain axes for angles about 200–3600 during 15 ps. Quenching of the h‐phase to 200K decrease the rotation amplitude up to ±12° corresponding to vibrations. The same type vibration motions (around chain axes) exists in o‐phase at 200K. Replacing of some H‐atoms in chains of initial crystal by ‐CH3 groups gave us the possibility to mimic Ethylene/Propylene copolymers. In this work we have created only random E/P copolymers with propylene (PP) units content up to 20%. At constant temperature (200K) increase of PP units in the copolymer produce a disordering initially perfect C‐50 crystal. The process goes anisotropically: long range order becomes violated along b‐direction of the initial crystal at [PP]=3,5% and along a‐direction pronounced order still exists at [PP]=10%. Analysis of structural alterations which appear in the system upon introduction of chemical defects (‐CH3 groups) was done by calculations of local volumes (Vloc) of each site containing three chain carbon atoms with the closest neighbours from the surrounding chains. Increase of [PP] concentration in copolymer increases Vloc and broaden it up considerably. The result shows broad distribution of crystalline cell sizes in copolymers. Local volumes of cells containing ‐CH3 groups might be larger or smaller than mean Vloc value. Some conclusions about conformation defects in chains appearing due to “copolymerisation” (appearing of PP‐units in chains) are drawn.
New conformations and new types of helix sense reversals and defects in the chains of nonchiral poly(alkyl isocyanates)
Authors: Lukasheva Natalia V. , Niemela Satu , Neelov Igor M. , Darinskii Anatolii A. , Sundholm Franciska , Cook Robert
Published: March 2011

Molecular mechanics studies of helix sense reversals and defects of the regularity in the helices of the same sense in the chains of poly(alkylisocyanates) were performed. The effect of medium was studied by using different values of the dielectric constant. Additionally to the reversals between the helix mirror images (MI) considered in the literature new types of reversals have been investigated. These reversals connect the helices having backbone torsion angles not only with opposite signs but also with inverse angle values (MII). For the MI reversals we report in addition to the small angle break conformations known from literature the discovery of new conformations of similar energy but with large angle breaks. Large angle reversals can be responsible for up to 50% of the chain persistence length in non‐polar solvents. In vacuum MII reversals and defects have energies higher than MI reversals because of the strong electrostatic repulsion. At ϵ = 3.5 some defects have energy even lower that that of MI reversals.
The anharmonic character of Tg and Tm transition
Authors: Hlaváček B. , Křesálek V. , Souček J.
Published: March 2011

The idea of anharmonic oscillations has been extended to explain the glass transition or melting point. All ideas of free volume, vacancy transport, etc., have been respected but are treated as minor phenomena relative to harmonic‐anharmonic vibration transition. A simple model of coupled oscillators is studied. It is shown that coupled anharmonic oscillators can produce vibrations on entirely different levels of amplitudes, which explains the highly different coefficients of thermal expansion and cp values for solid and liquid states. At higher temperatures, for polymers in the rubber‐like zone, the theory of anharmonic coupled oscillators brings certain justification for the theories of De Gennes, Doi and Edwards or Rouse. The solid‐liquid transition seems to be connected on microlevel mainly with the enlargement of vibrational amplitudes of monomer or dimer units in polymer chain as the temperature increases.
Heterogeneity of crystalline structure of injection‐moulded and drawn isotactic polypropylene studied by DSC
Authors: Kratochvil J. , Kotek J. , Sikora A. , Raab M.
Published: March 2011

Differential scanning calorimetry (DSC) was used to characterize crystalline structure of injection‐moulded specimens of isotactic polypropylene and corresponding materials prepared by solid‐state drawing at various temperatures. It was shown that the DSC can assess the differences between individual specimens and structural gradients and heterogeneities within one typical test piece. In particular, relative proportions of the crystalline α and β modifications in different locations of an injection‐moulded specimen and structural transformation in the neck shoulder could be established. Variations of the crystalline structure along the edge of drawn specimens were interpreted as a record of temperature and stress fluctuations in the propagating neck shoulder.
Mechanical properties of recycled polymers
Authors: La Mantia Francesco Paolo
Published: March 2011

Modifications of structure and morphology of the polymers induced by the thermomechanical stress (or by the presence of water for some polymers) during reprocessing can cause a drastic deterioration of mechanical properties of the recycled material. The property ‐ reprocessing relationships are an important tool to determine not only the properties of the recycled polymers but also the strategies to use (processing conditions, stabilizers, fillers, compatibilizers, etc) in order to obtain recycled polymers with good mechanical properties. In this work, typical behaviour of some mechanical properties as a function of the number of reprocessing operations is discussed and correlated with their structure and morphology. The influences of the type of apparatus and of the processing conditions are also considered.
Lignocellulose ‐ polymer composites
Authors: Mansour Olfat , El‐Hady Bothina Abd , Ibrahim Samir K. , Goda Magda
Published: March 2011

Water hyacinth and its mechanical pulps were used as lignocellulose to produce composites together with polystyrene or urea‐formaldehyde resins. The bending strength of the composites increased with increasing concentration of the resin. The temperatures of the treatment of water hyacinth to obtain the pulps affect the strength and densities of the composites. This may be attributed to the behavior of lignin at temperatures higher than 135°C. The composites produced using urea‐formaldehyde resins showed slight increase in bending strengths compared with those produced using polystyrene, which may be attributed to the ability of formaldehyde to make crosslinks with the free OH groups of cellulose and hemicellulose. Contrary to water hyacinth, the use of ground palm leaves together with 10% urea‐formaldehyde resin produced composite with high density and low bending strength, while the ground water hyacinth failed. The pulp from palm leaves when processed into composites using 10% urea‐formaldehyde resin show bending and densities affected by its preparation and by the amount of the composite mixture to be pressed. Hence the type of the substrate defined the type of the polymers or resin used to obtain composites with proper mechanical properties. The effect of the pressure used to produce composites from ground palm leaves or their pulp together with polystyrene was investigated. Linear relationships between the bending strength and pressure were obtained, the bending strength and densities increasing with increasing pressure. Thus, the increased pressures enhance mechanical properties of the composites.
Conformational transformations in chiral polythiophene derivatives aggregated in polymethacrylate matrices: Experiments and molecular dynamics simulations
Authors: Bjornholm Thomas , Brostow Witold , Schaumburg Kjeld , Shibaev Peter V. , Sinani Vladimir , Vinokur Rostislav
Published: March 2011

Chiral derivatives of poly(3‐(S‐3',7'‐dimethyloctyl)thiophene) embedded in either poly(methyl methacrylate) (PMMA) or poly(butyl methacrylate) (PBMA) were studied by polarization optical microscopy, UV absorption and circular dichroism (CD) spectroscopy as well as simulated using the Molecular Dynamics procedure. CD spectra change on heating to mirror spectra; for PMMA‐containing blends the changes in heating/cooling cycles are reversible. The signs of CD spectra depend on free volume, the packing of side groups in particular. Since in the melt there are no restrictions on the positions of the chiral groups, those groups appears with equal probabilities at any locations with respect to the thiophene ring. By contrast, in clusters restrictions imposed by other alkyl chains result in positioning of chiral methyl groups preferentially on the left or right sides of the thiophene rings. The consequence is the formation of right or left twists in molecular backbones.
Compatibility of a statistical copolymer p(EMA‐CO‐MMA) with PS and PMMA
Authors: Schubert Dirk W. , Pannek Michael , Müller Axel H. E.
Published: March 2011

The compositions of coexisting phases and the interface widths in blends of a statistical copolymer of poly(ethylmethacrylate — co — methylmethacrylate) (P(EMA1,x‐co‐MMAx)) and a deuterated polystyrene (PS(D)) as well as a deuterated poly(methylmethacrylate) (PMMA(D)) have been investigated by neutron reflectometry (NR). Interaction parameters are calculated from the compositions of coexisting phases and the interface width values. Utilizing a novel two dimensional scheme for graphical representation of the interaction parameters, the results are in very good agreement with studies on the interaction parameters for PS/PMMA, PS/PEMA and PEMA/PMMA blends. In particular, XEMA/MMA deduced from a NR experiment on a P(EMA‐block‐MMA(D)) diblock copolymer fits excellent into the scheme.
Oriented crosslinked polyethylene pipes by a novel extrusion method
Authors: Järvenkylä Jyri , Johansson Bengt , Ek Carl‐Gustaf , Palmlöf Magnus , Ahjopalo Lisbeth , Kuutti Lauri , Pietilä Lars‐Olof , Neway Bereket , Gedde Ulf W.
Published: March 2011

Crosslinking and stretching (2.5 times along the circumferential direction) of the molten polymer during extrusion produced pipes with dominantly circumferential orientation and a lower degree of axial chain orientation. Differential scanning calorimetry (crystallinity and crystal thickness), density measurements (crystallinity), X‐ray diffraction (c‐axis orientation), infrared dichroism measurements (crystalline and amorphous chain orientation) and contraction measurements (molecular draw ratio) assessed the microstructure of the pipe material. The mechanical properties of the oriented material were assessed by uniaxial tensile tests. The orientation was biaxial with the main orientation in the circumferential direction and a lesser orientation in the axial direction. The maximum degree of circumferential orientation was obtained at the inner wall of the pipe. The lower degree of crosslinking of the core material allowed slippage of chains during the stretching of the molten polymer and it is suggested that this is the cause of the lower degree of orientation of the core material. The oriented pipe material exhibited a 5‐10% higher degree of crystallinity and higher crystal thickness than conventionally crosslinked material. The tensile modulus and the tensile strength of the oriented, cross‐linked material was greater along the axial direction than along the circumferential direction. The circumferential and axial moduli for the oriented, crosslinked pipe were greater than the corresponding moduli of the non‐oriented cross‐linked pipe material. Another pipe based on crosslinked PE that were first circumferentially stretched 2.5 times and later axially stretched 10 times (in the molten state) showed, despite the fact that it exhibited pronounced axial orientation almost a balanced tensile modulus (4.3±0.2 GPa) in the axial‐circumferential plane. Atomistic modelling showed that the orientational dependence of the density of the amorphous phase is small.
Study of dye diffusion in fibers by laser scanning confocal microscopy
Authors: Song Ye , Srinivasarao Mohan , Tonelli Alan
Published: March 2011

The diffusion of a fluorescent dye in nylon 66 fibers was studied by using a laser scanning confocal microscope (LSCM) and by a conventional method. The diffusion coefficients were determined by both methods and they were in close agreement. The study of dye diffusion in fibers by LSCM is simple, quick and also able to provide high resolution images of fiber cross‐sections and 3D images of the dye distribution in fibers. To our knowledge this is the first report of using a LSCM to study dye diffusion in polymeric fibers.
Characterization of acrylic dental polymers
Authors: Vera‐Graziano Ricardo , Martínez‐Richa Antonio , Palacios‐Alquisira Joaquín , Barceló‐Santana Federico , Castaño‐Meneses Victor
Published: March 2011

The chemical structure and the molecular parameters of four dental acrylic polymer materials (samples P‐1 to P‐4) and two polyacrylic acids of different molecular weight (relative molecular mass) used as model compounds (samples Paa‐1 and Paa‐2) were studied and correlated with polymer structure and molecular weight. All polymer samples show low molecular weights, MW, and broad poly‐dispersity as obtained by GPC. Samples P‐3 and P‐4 show the lower MW and bi‐modal distribution, one peak corresponding to the polymer and the other to a low molecular weight compound at a lower concentration. The other polymer samples show unimodal distribution. Initially, all samples were soluble in water and dioxane above 99.8%. However, after lyophilization at −50 °C they showed different degrees of solubility because of partial gelation. The FTIR and, 1H and 13C‐NMR spectra of Paa‐1, Paa‐2 in D2O show the pattern characteristic of poly(acrylic acid). The polymers of P‐1 and P‐2 are mainly poly(acrylic acid). The P‐3 spectra show the peak pattern for an (acrylic acid/methyl acrylate) copolymer of about 2:1 composition as calculated from the NMR spectra. The P‐4 is an oligomer derived from 2‐hydroxyethyl methacrylate. Solid 13C‐NMR spectra confirm the above structures and evidence anhydride formation after lyophilization. The MW and the linear expansion coefficient, α, were derived from intrinsic viscosity in theta and perturbed conditions. From this, the steric hindrance parameter, A, the molecular stiffness, σ, and the second virial coefficient, A2, were calculated using different thermodynamic models. The Flory‐Fox‐Shafgagen and the Stockmayer‐Fixman models fit better the experimental data and can be used to describe the molecular parameters of the acrylic polymers. Light scattering was used to compare results.
Miscibility behaviour of blends of a thermoplastic polyester polyurethane with vinyl polymers
Authors: Danait Achala , Deshpande Dinkar D.
Published: March 2011

A method based on the intrinsic viscosities of transfer has been used to predict miscibility of polymer blends. This method has been applied to study the change in the phase behaviour of a microphase separated polyester polyurethane (PSPU) on blending with polyvinyl chloride (PVC), polyvinyl acetate (PVAc) and a vinyl chloride‐vinyl acetate copolymer (VCVAc). The PVC/PSPU blends are found to exhibit complete miscibility over the entire composition range. PVAc/PSPU blends show immiscibility while VCVAc/PSPU blends show partial miscibility. Thermal analysis and scanning electron microscopic studies of the blend films have confirmed the results evaluated on the basis of the viscosity method.
Treatment of Ewing sarcoma family of tumors with a modified P6 protocol in children and adolescents
Authors: Mora Jaume , de Torres Carmen , Parareda Andreu , Torner Ferran , Galván Patricia , Rodríguez Eva , Cardesa Teresa , Salvador Héctor , Suñol Mariona , Huguet Ramon , Cruz Ofelia
Published: March 2011

Background

Reported overall survival (OS) rates of patients with localized Ewing sarcoma family of tumors (ESFT) are >80% when treated with the MSKCC P6 protocol. However, it has been associated with a 5.8% incidence of secondary leukemias. A modified P6 (mP6) protocol with reduced exposure to chemotherapy is presented.

Procedure

Thirty‐one newly diagnosed ESFT patients were enrolled onto this phase II, single‐arm, non‐randomized protocol. Courses 1, 2 and 4 consisted of cyclophosphamide 4.2 g/m2, doxorubicin 75 mg/m2, and vincristine 2 mg/m2 (CDV). Cycles 3 and 5 consisted of ifosfamide 9 g/m2 and etoposide 500 mg/m2 (IE). Course 5 ifosfamide was 14 g/m2 if necrosis was <90%.

Results

Twenty‐four patients had loco‐regional disease and seven had metastases. The 4‐year event‐free survival (EFS) rate for patients with localized tumors is 83% and overall survival (OS) is 92%. The 3‐year EFS rate for patients with distant metastases is 28% and OS rate is 42%. EWS‐FLI1 fusion genes were detected in 17 cases (74%) and EWS‐ERG in six cases (26%). Type 1 EWS‐FLI1 variant was present in 6/7 metastatic patients and 3/16 loco‐regional cases (P = 0.001). None of the patients experienced tumor progression before remission. All relapses occurred within 2 years from the end of treatment and local relapses (n = 3) happened in patients who did not receive radiation therapy. No secondary malignancies have been observed, median follow‐up of 4.3 years for surviving patients.

Conclusions

In this pilot study, the mP6 protocol produced a complete remission rate of 83% at 4 years in non‐metastatic ESFT reducing the risk of secondary malignancies. Pediatr Blood Cancer 2011;57:69–75. © 2011 Wiley‐Liss, Inc.
A study on fusion and rheological behaviors of PVC/SiO2 microcomposites and nanocomposites: The effects of SiO2 particle size
Authors: Ari Gulsen Albayrak , Aydin Ismail
Published: March 2011

In this study, poly(vinyl chloride) (PVC) and silica (SiO2) microcomposites and nanocomposites were prepared by melt mixing in a Haake torque rheometer. The fusion and rheological behaviors of PVC/SiO2 composites were evaluated by means of torque data recorded during processing to investigate the influence of the SiO2 particle size on these behaviors. It was found that the fusion time and the fusion temperature decreased with the decreasing of SiO2 particle size, whereas the fusion torque increased with the decreasing of particle size. The PVC/Si‐25‐nm nanocomposite (PVC including the 25 nm of SiO2) showed the highest apparent viscosity among the PVC/SiO2 microcomposites and nanocomposites prepared in this study. Scanning electron microscopy results demonstrated that some aggregates, whose sizes about 60–90 nm, were formed when the 25 nm of SiO2 was used as filler. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
On superembedding approach and its possible application in search for SO(32) heterotic five‐brane equations
Authors: Bandos I.A.
Published: March 2011

We elaborate the superembedding description of simple D = 10, N = 1 five‐brane and discuss the possible application of the superembedding approach in search for the equations of motion of the mysterious SO(32) heterotic five brane on this basis.
Stringy instantons and dualities
Authors: Frau M.
Published: March 2011

We discuss non‐perturbative corrections to the gauge kinetic functions in a four‐dimensional 𝒩 = 2 gauge theory realized with a system of D7/D3‐branes in a compactification of type I′ theory on 𝒯4ℤ2 × ℤ2. The non‐perturbative contributions arise when D(–1) branes, corresponding to stringy instantons, are added to the system; such contributions can be explicitly evaluated using localization techniques and precisely match the results predicted by the heterotic/type I′ duality. This agreement represents a very non‐trivial test of the stringy multi‐instanton calculus.
Strange metallic behaviour and the thermodynamics of charged dilatonic black holes
Authors: Meyer R. , Goutéraux B. , Kim B.S.
Published: March 2011

We review a recent holographic analysis [1] of charged black holes with scalar hair in view of their applications to the cuprate high temperature superconductors. We show in particular that these black holes show an interesting phase structure including critical behaviour at zero temperature or charge, describe both conductors and insulators (including holographic Mott‐like insulators), generically have no residual entropy and exhibit experimentally observed scaling relations between electronic entropy, specific heat and (linear) DC resistivity. Transport properties are discussed in the companion contribution [2] in these proceedings.
Modifications of laser field assisted intersubband transitions in the coupled quantum wells due to static electric field
Authors: Prasad Vinod , Dahiya Brijender
Published: March 2011

We consider the electron bound in the conduction band of a coupled asymmetric double quantum well (ADQW) interacting with static as well as strong monochromatic field in terahertz (THz) region. We use non‐perturbative Floquet theory to study the static field and quantum well (QW) system in the presence of strong laser fields. We show that the intersubband dynamics gets modified due to the static field. The sensitivity to the ratio of strengths of static and laser field (Es/E0) of the state populations can be used in various optoelectronic device applications.
High‐field domains from dc to 60 GHz
Authors: Böer Karl W.
Published: March 2011

The history of the high‐field domains is given with the description of the experimental and theoretical results of the team of the author in the first decade after their discovery in 1958. This work is done at CdS single crystal platelets that are used as a model substance. The major findings of modern high‐field domain research that followed their original research are then reviewed. It is emphasized that all high‐field domains are created for reasons of the minimum entropy production principle when the conductivity decreases more than linear within a semiconductor. The application of these high‐field domains in important semiconductor devices are reviewed that have now reached a multibillion dollar market.
Amorphous piezoresistive and piezoelectric sensors for robotics applications
Authors: Somolinos Jose Andrés , Morales Rafael , García Alfonso , Morón Carlos
Published: March 2011

Ultrasonic transducers have often been used in the development of sensory systems for robotics applications. In most cases, these sensory systems are based on the determination of times of flight for signals from every transducer. In this work we have used piezoresistive and piezoelectric materials to measure the instant and position collision in metallic structures by using the difference of the times of propagation of an acoustic wave when it is produced over a ferromagnetic (iron, steel or another material) based structure. An immediate application of the proposed method is the detection and location of impacts over the metallic links of an industrial robot or the collision position in a metallic structure for an automated inspection. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Metal‐Ion‐Induced Formation and Stabilization of Protein Cages Based on the Cowpea Chlorotic Mottle Virus
Authors: Minten Inge J. , Wilke Koos D. M. , Hendriks Linda J. A. , van Hest Jan C. M. , Nolte Roeland J. M. , Cornelissen Jeroen J. L. M.
Published: March 2011

The cowpea chlorotic mottle virus (CCMV) is a versatile building block for the construction of nanoreactors and functional materials. Upon RNA removal, the capsid can be reversibly assembled and disassembed by adjusting the pH. At pH 5.0 the capsid is in the native assembled conformation, while at pH 7.5 it disassembles into 90 capsid protein dimers. This special property enables the encapsulation of various molecules, such as protein and enzymes, but only at low pH. It is possible to stabilize the capsid at pH 7.5 by addition of negatively charged polyelectrolytes or negatively charged particles, but these methods all fill the interior of the capsid, leaving little or no space for other cargo molecules. This pH restriction therefore severely limits the range of enzymes that can be encapsulated, and hampers the investigation of the CCMV capsid as a nanoreactor for the study of enzymes in confined spaces. Herein, the interaction of N‐terminal histidine‐tag‐modified capsid proteins with several metal ions is reported. Depending on the conditions used, nanometer‐sized protein particles or capsidlike architectures are formed that are stable at pH 7.5. This metal‐mediated stabilization methodology is employed to form stable capsids containing multiple proteins at pH 7.5, thereby greatly expanding the scope of the CCMV capsid as a nanoreactor.
A phenomenological model of finite strain viscoplasticity with distortional hardening
Authors: Shutov A.V. , Panhans S. , Kreißig R.
Published: March 2011

In this paper we suggest a thermodynamically consistent approach to the simulation of a rate dependent material response at finite strains. The nonlinear mechanical phenomena which are covered by the proposed material model include distortional, kinematic, and isotropic hardening. Firstly, we present a new two‐dimensional rheological model of distortional hardening, which predicts the yield curve in the stress space to be a limaçon of Pascal. Such effects like the distortion of the yield surface in the stress space and its orientation depending on the loading path are captured by the rheological model in a vivid way. Next, the rheological model serves as a guideline for the construction of the constitutive equations. In particular, the kinematic assumptions, the ansatz for the free energy, and the form of the yield function are motivated by the rheological model. Further, two types of flow rules are considered in this study: a normality rule and a radial rule, both thermodynamically consistent. Moreover, we formulate explicitly the constraints on the material parameters, which guarantee the convexity of the yield surface. Furthermore, implicit time‐stepping methods are considered which exactly preserve the incompressibility of the inelastic flow. Finally, the basic features of the predicted material response are illustrated by a series of numerical simulations. In particular, the simulation results are compared to the real experimental data.
Severe burn injury induces a characteristic activation of extracellular signal‐regulated kinase 1/2 in spinal dorsal horn neurons
Authors: Whitel John P.M. , Kol Chin Wing , Fidalgol Antonio Rei , Cibellil Mario , Paulel Cleoper C. , Andersonl Peter J. , Cruzl Celia , Gombal Szabolcs , Mateszl Klara , Veressl Gabor , Avelinol Antonio , Nagyl Istvan
Published: March 2011

We have studied scalding‐type burn injury‐induced activation of extracellular signal‐regulated kinase 1/2 (ERK1/2) in the spinal dorsal horn, which is a recognised marker for spinal nociceptive processing. At 5 min after severe scalding injury to mouse hind‐paw, a substantial number of phosphorylated ERK1/2 (pERK1/2) immunopositive neurons were found in the ipsilateral dorsal horn. At 1 h post‐injury, the number of pERK1/2‐labelled neurons remained substantially the same. However, at 3 h post‐injury, a further increase in the number of labelled neurons was found on the ipsilateral side, while a remarkable increase in the number of labelled neurons on the contralateral side resulted in there being no significant difference between the extent of the labelling on both sides. By 6 h post‐injury, the number of labelled neurons was reduced on both sides without there being significant difference between the two sides. A similar pattern of severe scalding injury‐induced activation of ERK1/2 in spinal dorsal horn neurons over the same time‐course was found in mice which lacked the transient receptor potential type 1 receptor (TRPV1) except that the extent to which ERK1/2 was activated in the ipsilateral dorsal horn at 5 min post‐injury was significantly greater in wild‐type animals when compared to TRPV1 null animals. This difference in activation of ERK1/2 in spinal dorsal horn neurons was abolished within 1 h after injury, demonstrating that TRPV1 is not essential for the maintenance of ongoing spinal nociceptive processing in inflammatory pain conditions in mouse resulting from at least certain types of severe burn injury.
Kinases and phosphatases in the mammalian circadian clock
Authors: Reischl Silke , Kramer Achim
Published: March 2011

Posttranslational modifications of circadian oscillator components are crucial for the generation of circadian rhythms. Among those phosphorylation plays key roles ranging from regulating degradation, complex formation, subcellular localization and activity. Although most of the known clock proteins are phosphoproteins in vivo, a comprehensive view about the regulation of clock protein phosphorylation is still missing. Here, we review our current knowledge about the role of clock protein phosphorylation and its regulation by kinases and phosphatases in eukaryotes with a major focus on the mammalian circadian clock.
March of the chekists: Beria’s secret police patronage network and Soviet crypto-politics
Authors: Blauvelt Timothy K.
Published: March 2011

Lavrentii Beria built up one of the most powerful patronage networks in Soviet history. Its success represents a unique case in Soviet history in which a regionally based secret police patron-client network, comprised primarily of representatives of ethnic minorities, took control first of the civilian leadership of one of the major regions of the Union, and then of the most powerful institution in the USSR, the national secret police, and subsequently became one of the main competing factions in the “crypto-politics” of the late-Stalin era. The fact that the Beria network emerged from the secret police gave it certain advantages in the political struggles of the period, but it also held weaknesses that played a role in Beria’s final undoing. The evolution and political struggles of Beria’s network also shed light on the inner workings of the competition among informal networks that made up the crypto-politics of the period. Using recent memoirs, new archival sources and interviews, this article will examine how Beria developed, managed and advanced his informal network, giving particular attention to the specific and unique outcomes that resulted from the rooting of this network in the secret police, at five critical junctures in Beria’s career.
Factionalism Among Syrian Nationalists During the French Mandate
Authors: Khoury Philip S.
Published: March 2011

It is ironic and perhaps telling that the one national independence movement largely ignored by historians of the Arab Middle East is the Syrian nationalist movement. The irony, of course, is that the birthplace of Arab nationalism was Syria; it was to Damascus that Arab nationalists in Palestine, Iraq and elsewhere looked for inspiration, guidance, and moral support in the interwar period; and out of the Syrian movement sprang the radical nationalism of the Ba'thists. Intellectual histories of the precursors, birth, and content of Arab nationalism abound, and, insofar as these histories deal with the birthplace of Arab nationalism, they must discuss Damascus and Syria just prior to and during World War I. But once the intellectual birth of Arab nationalism has been discussed, interest in the history of Syria wanes to be revived only after World War II, with the emergence of Ba'thism and the military in politics. What follows is by no means a comprehensive analysis of the nature and organization of the Syrian national independence movement; rather, it is a preliminary investigation of some salient characteristics of the politics of Syrian-Arab nationalism in the early years of the French Mandate.
A novel dynamic walker with heel, ankle, and toe rocker motions
Authors: Kumar R. Prasanth , Özer Abdullah , Kim Gabsoon , Yoon Jungwon
Published: March 2011

This paper proposes a novel dynamic walker capable of walking with heel, ankle, and toe rocker motions. The heel and toe rocker motions are obtained by using inelastic stoppers between leg and foot, which limit the range of rotation of the foot about the ankle joint. A generalized set of equations of motion and associated transition equations applicable for multiple foot segments is derived. Passive dynamic walking is studied with equal heel and toe strike angles for the case of symmetric foot walking. It is shown that by including the ankle joint, low-speed walking is made possible. The energy efficiency of the proposed walker is studied theoretically and through numerical simulations. Finally, three different underactuated modes of active walking that do not require toe and heel actuation are presented. In order to implement these modes of walking, the proposed walker can be constructed with little modification from an existing flat-foot walker that uses ankle rocker motion alone. Results show that substantial benefits can be obtained in efficiency and stability compared to point/flat-foot walker of the same leg length and mass distribution.
Molecular obesity, potency and other addictions in drug discovery
Authors: Hann Michael M.
Published: March 2011

Molecular Obesity is the tendency for lead optimisation to yield candidate molecules that are unfit for their continued survival towards becoming a drug. Reasons for this and other issues are discussed.
Equality, difference and the absent presence of 'race' in citizenship education in the UK
Authors: Garratt Dean
Published: March 2011

Francis of Education (print)/1474-8479 (online) 2011 This paper examines the political and historical antecedents of the absent presence of 'race' in successive policies for citizenship education in contemporary Britain. It questions the possibility of embracing an emerging cosmopolitanism
and politics of difference, within the limiting frame of the nation state and its overarching appeal towards common values and goals. In that schools are widely regarded as important repositories of social and moral values, the paper moves to consider how policy tensions can be productively
employed by teachers to produce a re-articulation of equality and difference in order to enhance education, citizenship and social justice.
The small RNA PhrS stimulates synthesis of the Pseudomonas aeruginosa quinolone signal
Authors: Sonnleitner Elisabeth , Gonzalez Nicolas , Sorger‐Domenigg Theresa , Heeb Stephan , Richter Andreas S. , Backofen Rolf , Williams Paul , Hüttenhofer Alexander , Haas Dieter , Bläsi Udo
Published: March 2011

Quorum sensing, a cell‐to‐cell communication system based on small signal molecules, is employed by the human pathogen Pseudomonas aeruginosa to regulate virulence and biofilm development. Moreover, regulation by small trans‐encoded RNAs has become a focal issue in studies of virulence gene expression of bacterial pathogens. In this study, we have identified the small RNA PhrS as an activator of PqsR synthesis, one of the key quorum‐sensing regulators in P. aeruginosa. Genetic studies revealed a novel mode of regulation by a sRNA, whereby PhrS uses a base‐pairing mechanism to activate a short upstream open reading frame to which the pqsR gene is translationally coupled. Expression of phrS requires the oxygen‐responsive regulator ANR. Thus, PhrS is the first bacterial sRNA that provides a regulatory link between oxygen availability and quorum sensing, which may impact on oxygen‐limited growth in P. aeruginosa biofilms.
Is PUVA maintenance therapy necessary in patients with early‐stage mycosis fungoides? Evaluation of a treatment guideline over a 28‐month follow‐up
Authors: Sánchez María A. , González Tatiana , Gaitán Miguel F. , Zuluaga Ángela , Jiménez Sol B. , de Galvis Yolanda T.
Published: March 2011

Background  Cutaneous T‐cell lymphoma is a rare condition that represents 2% of all lymphomas and 75–80% of primary cutaneous lymphomas. The objective of the present study is to evaluate a clinical practice guideline.

Methods  This paper reports a prospective cohort study with a five‐year follow‐up. This is the second report to describe the analysis of data obtained during follow‐up of 28 months. To date, 40 patients diagnosed with early‐stage mycosis fungoides (stage IA, n = 20; stage IB, n = 20) have been enrolled. All patients have been treated with a minimum of 58 sessions of psoralen and long‐wave ultraviolet radiation, with complete clinical and histological clearance of lesions. Variables considered include disease duration, treatment time, treatment dose, and history of relapse. Complete physical examinations and diverse complementary examinations were performed. A tumor–node–metastasis–blood staging system was applied. The population was divided into two groups according to results consisting, respectively, of those who relapsed during follow‐up (n = 12) and those who did not (n = 28).

Results  History of relapse was the variable most strongly associated with future relapse (relative risk = 10.38, 95% confidence interval 2.64–40.72). No statistically significant difference between the groups according to receipt of maintenance therapy was found (P = 0.161).

Conclusions  Our results strongly suggest that maintenance therapy does not prevent future relapse. However, history of relapse is a strong predictor for future relapse.
Effectively widening the gene pool of oilseed rape (Brassica napus L.) by using Chinese B. rapa in a ‘virtual allopolyploid’ approach
Authors: Mei JiaQin , Fu Ying , Qian LunWen , Xu XinFu , Li JiaNa , Qian Wei
Published: March 2011

With 2 figures and 2 tables

Brassica rapa (AA), which has a high level of genetic diversity, has been used to widen the genetic base of oilseed rape (B. napus L., AACC). However, the differences in the degree to which the genetic base of oilseed rape can be widened using different forms of B. rapa have not been well characterized. We used a strategy of virtual allopolyploid to investigate the genetic differences between the A subgenome of natural oilseed rape and different ecotypes of B. rapa. In this strategy, the genetic characteristics of the virtual allopolyploid lines are deduced from the genotypes of the parental lines which are established using molecular markers, without the need for interspecific hybridization. Three genotypes of B. oleracea and 56 accessions of B. rapa which originated from Europe, China and India were genotyped using simple sequence repeat markers, together with nine oilseed rape lines representing spring, semi‐winter and winter types. The genotypes of 168 virtual allopolyploid lines were derived from those of the parental lines and compared with those of the natural oilseed rape lines. Our data revealed that the virtual allopolyploid lines that were derived from Chinese semi‐winter B. rapa showed substantial genetic variation from natural oilseed rape. This indicates that Chinese semi‐winter B. rapa can be used effectively to broaden the germplasm of oilseed rape.
Quantitative variation analysis of fetal DNA in maternal plasma samples collected before and after amniocentesis
Authors: Bussani Cecilia , Di Tommaso Mariarosaria , Cioni Riccardo , Pasquini Lucia , Quitadamo Laura , Scarselli Gianfranco
Published: March 2011

Aims:  The aim of this study was to evaluate possible procedure‐related variations in the levels of cell‐free fetal DNA (fDNA) in maternal plasma of women undergoing genetic amniocentesis.

Materials and Methods:  Blood samples were collected at 16–18 weeks' gestation from 33 pregnant women attending the Fetal Medicine Unit for genetic amniocentesis. For each woman, two blood samples were obtained: the first immediately before amniocentesis and the second one 15 min after the procedure. A real‐time quantitative polymerase chain reaction assay, using primers for SRY and beta‐globin genes, was used to assess fDNA concentrations in maternal plasma. A Wilcoxon signed‐rank test was used for statistical analysis.

Results:  The karyotype on cultured amniocytes showed that 15 out of 33 women had a male fetus. Real‐time quantitative polymerase chain reaction results, on maternal plasma sample pairs from known male pregnancies, showed no significant variations of fDNA correlated to amniocentesis (P = 0.394).

Conclusions:  Our preliminary study suggests that amniocentesis, although invasive, could be associated with minimal, if any, disruption at the fetal–maternal interface, as revealed by the lack of substantial modifications of fDNA levels in maternal circulation.
Measurement of fasting ketonuria and capillary blood glucose after main meals in women with gestational diabetes mellitus: How well is the metabolic picture captured?
Authors: Montaner Paquita , Ripollés Joaquim , Pamies Carme , Corcoy Rosa
Published: March 2011

Aim:  Metabolic monitoring of women with gestational diabetes mellitus (GDM) usually consists of measuring fasting ketonuria and postprandial capillary blood glucose (CBG) after main meals. We aimed to evaluate how this monitoring system captures the metabolic picture as compared to a scheme with a greater number of time points.

Methods:  Thirty‐five women with GDM were recommended to follow a fractionated diet and trained in CBG and ketonuria monitoring. They were asked to monitor ketonuria before a main meal, and to monitor CBG at fasting and 1 h postprandial after any two of the six daily meals. Participants were requested to monitor different meals each day. The goal for 1 h postprandial CBG was <135 mg/dL (7.5 mmol/L). Ketonuria was defined as significant before a certain meal when ≥30% of measurements at that point were positive. Similarly, postprandial CBG was defined as abnormal after a meal when ≥30% measurements exceeded the goal.

Results:  Ketonuria was significant in 22.5% of the time points and 41.2% of women had significant ketonuria at one or more time points; 61% of the time points and 35.7% of the women with significant ketonuria would have been undetected with monitoring restricted to breakfast. Postprandial CBG was abnormal in 17.6% of meals and 57% of women had abnormal postprandial CBG at one or more meals; 37.8% of points and 15% of women with abnormal postprandial CBG would have been undetected with monitoring restricted to main meals.

Conclusion:  A substantial proportion of metabolic abnormalities in GDM women are not detected with a monitoring program that measures only fasting ketonuria and postprandial CBG after main meals.
A Critique of “In Search of Token Women in Academia”
Authors: Constantinople Anne
Published: March 2011

The research of Young, MacKenzie, & Sherif (1980), designed to test Laws' (1975) analysis of token women in academia, is criticized on several methodological and conceptual grounds. The appropriateness of the study as a test of Laws' theory is questioned since no evidence is offered for the validity of the independent variables as measures of tokenism. Alternative explanations for their data, centering primarily on generational differences in attitudes and values, are examined briefly.
“In Search of Token Women in Academia”: Some Definitions and Clarifications
Authors: Young Carlotta Joyner , MacKenzie Doris Layton , Sherif Carolyn Wood
Published: March 2011

This article makes an important distinction between two definitions of “token woman.” In the first definition, a token woman is one of few women in a predominantly male setting. The second meaning of “Token Woman” identifies that subset of such women who have made the distinctive psychological adaptation described by Laws (1975). The methodological decisions in Young, MacKenzie, and Sherif's (1980) research are justified as based on that definitional distinction. Constantinople's critique is shown to be appropriate as an alternative to Laws' theory, but not as a criticism of our research. Alternative generational explanations for previous findings about Token Women are not supported by existing data.