bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal expansion of polymers submitted to supercritical CO2 as a function of pressure
Authors: Boyer Séverine A. E. , Randzio Stanislaw L. , Grolier Jean‐Pierre E. 
Published: November 2005

AbstractInteractions of polymers with compressed supercritical CO2 has been studied by using pressure‐controlled scanning calorimetry (PCSC). Global cubic thermal expansion coefficients (αpol‐g‐int) for medium density polyethylene (MDPE) and poly(vinylidene fluoride) (PVDF) saturated with supercritical CO2 have been determined at 352.4 K over the pressure range from 0.1 MPa to 100 MPa. In both cases, the isotherms of global αpol‐g‐int exhibit minima near 20 MPa. At pressures below the minimum, αpol‐g‐int for the PVDF–CO2 system are higher than for the MDPE–CO2 system, while at pressures above the minimum the opposite was observed. This proves that incorporation of CO2 in PVDF is stronger than in MDPE. The appearance of the minimum is attributed to the action of compressed CO2 molecules, which at higher pressures are forced to enter deep inside the interstitial or other voids in the polymer and cause their mechanical distension, which must be associated with an endothermic effect. The measurements have been performed on polymers used for fabrication of pipelines. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44:185–194, 2006
Structure and properties of some novel fluoroelastomer/clay nanocomposites with special reference to their interaction
Authors: Maiti Madhuchhanda , Bhowmick Anil K. 
Published: November 2005

AbstractIn the present work, rubber/clay nanocomposites were prepared by a solution mixing process using fluoroelastomers and different nanoclays (namely, Cloisite NA+, Cloisite 10A, Cloisite 20A, and Cloisite 30B). Fluoroelastomers having different microstructure and viscosity (Viton B‐50, Viton B‐600, Viton A‐200, and VTR‐8550) were used. Characterization of the nanocomposites was done by using X‐ray diffraction and atomic force microscopy. The mechanical and dynamic mechanical properties were studied. The surface energy of the clays and the elastomer was also measured. Even with the addition of only 4 phr of clay in Viton B‐50, tensile strength and modulus improved by 30–96% and 80–134%, respectively, depending on the nature of the nanoclays. Exfoliation was observed with both the unmodified and the modified clays at low loading in all the fluoroelastomers. Best properties were observed with the unmodified clay. All the grades of fluororubber followed the same trend. The increment (19%) in storage modulus was also higher in the case of the unmodified clay filled Viton B‐50 system. The results were explained with the help of thermodynamics, surface energies, and swelling studies. The difference in surface energy, Δγ, between the rubber and the unmodified clay was lower. The work of adhesion (67.63 mJ/m2) between Viton B‐50 and Cloisite NA+ was also higher than that (51.42 mJ/m2) between Viton B‐50 and Cloisite 20A. Negative ΔHS value for the unmodified clay‐filled system thermodynamically favored the formation of the nanocomposite as compared to the modified clay filled samples where ΔHS is positive or zero. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 162‐176, 2006
Maximum tensile properties of oriented polyethylene, achieved by uniaxial drawing of solution‐grown crystal mats: Effects of molecular weight and molecular weight distribution
Authors: Sawai Daisuke , Nagai Kazuhiko , Kubota Minato , Ohama Toshio , Kanamoto Tetsuo 
Published: November 2005

AbstractThe effects of molecular weight (MW) and MW distribution on the maximum tensile properties of polyethylene (PE), achieved by the uniaxial drawing of solution‐grown crystal (SGC) mats, were studied. The linear‐PE samples used had wide ranges of weight‐average (Mw = 1.5–65 × 105) and number‐average MWs (Mn = 2.0–100 × 104), and MW distribution (Mw/Mn = 2.3–14). The SGC mats of these samples were drawn by a two‐stage draw technique, which consists of a first‐stage solid‐state coextrusion followed by a second‐stage tensile drawing, under controlled conditions. The optimum temperature for the second‐stage draw and the resulting maximum‐achieved total draw ratio (DRt) increased with the MW. For a given PE, both the tensile modulus and strength increased steadily with the DRt and reached constant values that are characteristic for the sample MW. The tensile modulus at a given DRt was not significantly affected by the MW in the lower DRt range (DRt < 50). However, both the maximum achieved tensile modulus (80–225 GPa) and strength (1.0–5.6 GPa), as well as those at higher DRts > 50, were significantly higher for a higher MW. Although the maximum modulus reached 225 ± 5 for Mn ≥ 4 × 105, the maximum strength continued to increase with Mn even for Mn > 4 × 105, showing that strength is more strongly dependent on the Mn, even at higher Mn. Furthermore, it was found that each of the maximum tensile modulus and strength achieved could be expressed by a unique function of the Mn, independently of the wide variations of the sample MW and MW distribution. These results provide an experimental evidence that the Mn has a crucial effect on the tensile properties of extremely drawn and chain‐extended PE fibers, because the structural continuity along the fiber axis increases with the chain length, and hence with the Mn. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 153–161, 2006
Role of phosphorylated Thr160 for the activation of the CDK2/Cyclin A complex
Authors: De Vivo Marco , Cavalli Andrea , Bottegoni Giovanni , Carloni Paolo , Recanatini Maurizio 
Published: November 2005

AbstractThe enzymatic activity of the CDK2/Cyclin A complex increases upon the specific phosphorylation of Thr160@CDK2. In the present study, we have performed a comparative molecular dynamics (MD) study of models of the complex CDK2/Cyclin A/Substrate, which differ for the presence or absence of the phosphate group bound to Thr160. The models are based on two X‐ray structures available for CDK2/CyclinA and pCDK2/CyclinA/Substrate complexes. In this way, we analyze the influence of the phosphorylated Thr160 (pThr160) on both the flexibility of CDK2 activation loop (AL) and substrate binding in CDK2. Our calculations point to a decreased flexibility of the AL in the phosphorylated model, in fairly good agreement with experimental data, and to a key role of pThr160 for substrate recognition and stability. Multiple alignments of the CDKs sequences point to the very high conservation of the AL sequence among the CDKs, thus extending our results to all CDKs. Proteins 2006. © 2005 Wiley‐Liss, Inc.
Structure, conformational stability, and enzymatic properties of acylphosphatase from the hyperthermophile Sulfolobus solfataricus
Authors: Corazza Alessandra , Rosano Camillo , Pagano Katiuscia , Alverdi Vera , Esposito Gennaro , Capanni Cristina , Bemporad Francesco , Plakoutsi Georgia , Stefani Massimo , Chiti Fabrizio , Zuccotti Simone , Bolognesi Martino , Viglino Paolo 
Published: November 2005

AbstractThe structure of AcP from the hyperthermophilic archaeon Sulfolobus solfataricus has been determined by 1H‐NMR spectroscopy and X‐ray crystallography. Solution and crystal structures (1.27 Å resolution, R‐factor 13.7%) were obtained on the full‐length protein and on an N‐truncated form lacking the first 12 residues, respectively. The overall Sso AcP fold, starting at residue 13, displays the same βαββαβ topology previously described for other members of the AcP family from mesophilic sources. The unstructured N‐terminal tail may be crucial for the unusual aggregation mechanism of Sso AcP previously reported. Sso AcP catalytic activity is reduced at room temperature but rises at its working temperature to values comparable to those displayed by its mesophilic counterparts at 25–37°C. Such a reduced activity can result from protein rigidity and from the active site stiffening due the presence of a salt bridge between the C‐terminal carboxylate and the active site arginine. Sso AcP is characterized by a melting temperature, Tm, of 100.8°C and an unfolding free energy, ΔG, at 28°C and 81°C of 48.7 and 20.6 kJ mol−1, respectively. The kinetic and structural data indicate that mesophilic and hyperthermophilic AcP's display similar enzymatic activities and conformational stabilities at their working conditions. Structural analysis of the factor responsible for Sso AcP thermostability with respect to mesophilic AcP's revealed the importance of a ion pair network stabilizing particularly the β‐sheet and the loop connecting the fourth and fifth strands, together with increased density packing, loop shortening and a higher α‐helical propensity. Proteins 2006. © 2005 Wiley‐Liss, Inc.
Are structural biases at protein termini a signature of vectorial folding?
Authors: Laio Alessandro , Micheletti Cristian 
Published: November 2005

AbstractExperimental investigations of the biosynthesis of a number of proteins have pointed out that part of the native structure may be acquired already during translation. We carried out a comprehensive statistical analysis of some average structural properties of proteins that have been put forward as possible signatures of this progressive buildup process. Contrary to a widespread belief, we found that there is no major propensity of the amino acids to form contacts with residues that are closer to the N‐terminus. Moreover, we found that the C‐terminus is significantly more compact and locally organized than the N‐terminus. This bias, though, is unlikely to be related to vectorial effects, since it correlates with subtle differences in the primary sequence. These findings indicate that even if proteins acquire their structure vectorially, no signature of this seems to be detectable in their average structural properties. Proteins 2006. © 2005 Wiley‐Liss, Inc.
Preparation of amino‐acid‐type selective isotope labeling of protein expressed in Pichia pastoris
Authors: Chen Chiu‐Yueh , Cheng Chun‐Ho , Chen Yi‐Chun , Lee Jenq‐Chang , Chou Shan‐Ho , Huang Wenya , Chuang Woei‐Jer 
Published: November 2005

AbstractWe report the culture conditions for successful amino‐acid‐type selective (AATS) isotope labeling of protein expressed in Pichia pastoris (P. pastoris). Rhodostomin (Rho), a six disulfide‐bonded protein expressed in P. pastoris with the correct fold, was used to optimize the culture conditions. The concentrations of [α‐15N] selective amino acid, nonlabeled amino acids, and ammonium chloride, as well as induction time, were optimized to avoid scrambling and to increase the incorporation rate and protein yield. The optimized protocol was successfully applied to produce AATS isotope‐labeled Rho. The labeling of [α‐15N]Cys has a 50% incorporation rate, and all 12 cysteine resonances were observed in HSQC spectrum. The labeling of [α‐15N]Leu, ‐Lys, and ‐Met amino acids has an incorporation rate greater than 65%, and the expected number of resonances in the HSQC spectra were observed. In contrast, the labeling of [α‐15N]Asp and ‐Gly amino acids has a low incorporation rate and the scrambling problem. In addition, the culture condition was successfully applied to label dendroaspin (Den), a four disulfide‐bonded protein expressed in P. pastoris. Therefore, the described condition should be generally applicable to other proteins produced in the P. pastoris expression system. This is the first report to present a protocol for AATS isotope labeling of protein expressed in P. pastoris for NMR study. Proteins 2006. © 2005 Wiley‐Liss, Inc.
Thermal denaturation of a recombinant mouse amelogenin: Circular dichroism and differential scanning calorimetric studies
Authors: Oobatake Motohisa , Yamasaki Tomoko , Simmer James P. , Renugopalakrishnan V. 
Published: November 2005

AbstractConformational analyses of a recombinant mouse tooth enamel amelogenin (rM179) were performed using circular dichroism (CD), fluorescence, differential scanning calorimetry, and sedimentation equilibrium studies. The results show that the far‐UV CD spectra of rM179 at acidic pH and 10°C are different from the spectra of random coil in 6 M GdnHCl. A near‐UV CD spectrum of rM179 at 10°C is similar to that of rM179 in 6 M GdnHCl, which indicates that aromatic residues of native structure are exposed to solvent and rotate freely. Far‐UV CD values of rM179 at 80°C are different from that of random‐coil structure in 6 M GdnHCl, which suggests that rM179 at 80°C has specific secondary structures. A gradual thermal transition was observed by far‐UV CD, which is interpreted as a weak cooperative transition from specific secondary structures to other specific secondary structures. The fluorescence emission maximum for the spectrum due to Trp residues in rM179 at 10°C shows the same fluorescence emission maximum as rM179 in 6 M GdnHCl and amino acid Trp, which indicates that the three Trp in rM179 are exposed to solvent. Deconvolution of differential scanning calorimetry curve gives the population of three states (A, I, and C states). These results indicate that three states (A, I, and C) have specific secondary structures, in which hydrophobic and Trp residues are exposed to the solvent. The thermodynamic characteristics of rM179 are unique and different from a typical globular protein, proline‐rich peptides, and a molten globule state. Proteins 2006. © 2005 Wiley‐Liss, Inc.
Functional role of a protein foldon—An Ω‐loop foldon controls the alkaline transition in ferricytochrome c
Authors: Maity Haripada , Rumbley Jon N. , Englander S. Walter 
Published: November 2005

AbstractHydrogen exchange results for cytochrome c and several other proteins show that they are composed of a number of foldon units which continually unfold and refold and account for some functional properties. Previous work showed that one Ω‐loop foldon controls the rate of the structural switching and ligand exchange behavior of cytochrome c known as the alkaline transition. The present work tests the role of foldons in the alkaline transition equilibrium. We measured the effects of denaturant and 14 destabilizing mutations. The results show that the ligand exchange equilibrium is controlled by the stability of the same foldon unit implicated before. In addition, the results obtained confirm the ε‐amino group of Lys79 and Lys73 as the alkaline replacement ligands and bear on the search for a triggering group. Proteins 2005. © 2005 Wiley‐Liss, Inc.
Managing and mining protein crystallization data
Authors: Amin Abdullah A. , Faux Noel G. , Fenalti Gustavo , Williams Geoffrey , Bernadou Adam , Daglish Ben , Keefe Karen , Middleton Shayne , Rae Joseph , Tetis Kosmas , Law Ruby H.P. , Fulton Kate F. , Rossjohn Jamie , Whisstock James C. , Buckle Ashley M. 
Published: November 2005

AbstractThe crystallization of macromolecules remains a major bottleneck in structural biology. The routine screening of more than one thousand crystallization conditions and subsequent optimization by fine screening presents a challenge to conventional laboratory notebook keeping. In addition, the development of high‐throughput robotic crystallization and imaging systems presents a pressing need for low‐cost laboratory information management system (LIMS). Here we describe CLIMS2, a crystallization LIMS that features a simple, user‐friendly graphical interface, allowing the storage, management, retrieval and mining of crystallization data. The CLIMS2 executable and documentation is freely available at http://clims.med.monash.edu.au. Proteins 2006. © 2005 Wiley‐Liss, Inc.
Experimental determination and estimation of closed cup flash points of mixtures of flammable solvents
Authors: Catoire Laurent , Paulmier Stéphanie , Naudet Valérie 
Published: November 2005

AbstractFlash points, in air at atmospheric pressure, of some binary and ternary mixtures are experimentally determined in this study. All the components of these mixtures are flammable. These data are used to further validate a simple and accurate method proposed for the estimation of flash points for both pure compounds and multicomponent mixtures. This method does not depend on experimental flash point or flammability limit data and requires only the normal boiling point temperature, the heat of vaporization, and the number of carbon atoms for the pure components, as well as vapor–liquid equilibrium data on the mixture. This method can be used to predict hazards resulting from minimum flash point behavior and probably the effects of small concentrations of volatile flammable contaminants on the flash point value of a mixture. It may therefore help to develop products (lubricants, fuels, etc.) that meet safety standards. © 2005 American Institute of Chemical Engineers Process Saf Prog, 2006
A study of dislocation contribution from the temperature dependence of zero‐bias resistance‐area product of long‐wavelength n‐on‐p mercury cadmium telluride diodes
Authors: Gopal Vishnu , Gupta Sudha 
Published: November 2005

AbstractA study of the contribution of dislocations to the zero‐bias resistance–area product (R0A) of long‐wavelength infrared n‐on‐p mercury cadmium telluride (HgCdTe) diodes has been carried out from the modelling of the temperature dependence of R0A product of diodes fabricated in a material of known dislocation density. The capture probabilities of electrons and holes relevant to the modelling of the effect of dislocations in p‐type HgCdTe have been thus evaluated. The general applicability of these parameters has been further verified by using them to model the temperature variation of the R0A of the diodes reported by other groups. Results of the present study show that dislocations degrade the impedance of HgCdTe diodes at low temperatures on account of their shunt‐resistance behavior rather than the commonly accepted dislocation‐assisted tunnelling mechanism. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
From electronic grade to solar grade silicon: chances and challenges in photovoltaics
Authors: Pizzini S. , Acciarri M. , Binetti S. 
Published: November 2005

AbstractPhotovoltaics is a promising but challenging opportunity for the environmentally clean production of electric energy, as the cost of the produced energy is still too high to compete with conventional thermal and nuclear sources, in spite of the scientific and technological progress occurred in this field after the first oil crisis of 1973. Among the problems which should be solved to make photovoltaics fully competitive, a breakthrough concerning the cost reduction of the base material is compulsory. Aim of this paper is to discuss the scientific and technological problems encountered in the development of solar silicon for its use in high efficiency and low cost solar cells, and to give some firm experimental evidences about its potentialities. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Wet‐oxidation effect on p‐type transparent conducting CuAlO2 thin film
Authors: Kim Dae‐Sung , Choi Se‐Young 
Published: November 2005

AbstractThe wet‐oxidation effect on optical and electrical properties of CuAlO2 thin films was investigated with different water vapor pressures. Preferential (006) oriented films were ob‐tained after wet‐oxidation. The transmittance was 50–85% for the visible range and the optical band gap was estimated to be 3.96–4.20 eV. The p‐type nature of the films was confirmed by Hall effect measurements. The resistivity and transmittance were increased as water vapor pressure, and these phenomena were caused by the decrease of lower oxides with higher oxygen pressure. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
X‐ray synchrotron diffraction studies of III–V semiconductor compounds implanted with hydrogen
Authors: Wieteska K. , Wierzchowski W. , Graeff W. , Gawlik G. 
Published: November 2005

AbstractGaAs crystals and Al0.43Ga0.57As epitaxial layers of low dislocation density were implanted with 146 keV, 100 keV and 60 keV H+ ions and studied by recording of rocking curves, reciprocal space mapping and Bragg‐type section topography. The X‐ray investigation were performed also in the case of GaAs double implanted with 146 keV and 60 keV protons with doses of 6 × 1015 cm–2 and 4.2 × 1015 cm–2, with penetration ranges differing by a factor 2. The rocking curves and Bragg‐type section patterns for single implantation were readily explainable by approximating the strain profiles by the point‐defect distribution calculated with the TRIM95 program. In the case of double implantation with hydrogen ions the rocking curve contained much narrower interference maxima than the curves for single implantation. The experimental curve was well approximated by the theoretical one obtained by numerical integration of the Takagi–Taupin equations. The strain profile in this calculation was a sum of strain profiles of single implantations. The narrow interference maxima were most probably caused by beating of the radiation, reflected by two strain maxima located at different depths in the implanted crystal. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Direct evidence of self‐aligned Si nanocrystals formed by ion irradiation of Si/SiO2 interfaces
Authors: Röntzsch Lars , Heinig Karl‐Heinz , Schmidt Bernd , Mücklich Arndt , Möller Wolfhard , Thomas Jürgen , Gemming Thomas 
Published: November 2005

AbstractEnergy‐filtered transmission electron microscopy proves directly that ion irradiation and post‐irradiation annealing of a Si/SiO2 interface results in the formation of a narrow layer of monodisperse Si nanocrystals in the oxide at a tunnel distance from the interface. Position and size of the Si nanocrystals are in agreement with predictive atomistic computer simulations. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bogoliubov theory of Bose‐condensates of spinor exciton‐polaritons
Authors: Shelykh I. A. , Malpuech G. , Kavokin A. V. 
Published: November 2005

AbstractIn the present work, we present the formalism allowing to calculate the energy spectrum of polariton spinor Bose condensates. We investigate the dispersion of the elementary excitations of the weakly depleted polariton condensate within the framework of the Bogoliubov approach. We show that for linearly polarized condensates the anisotropy of the polariton‐polariton interactions leads to important differences in polariton dispersion in linear co‐ and cross‐linear polarizations. Surprisingly, we find that contrary to the standard Bogoliubov model (which does not take into account the spin of the condensate) the dispersion is not necessary linear at k = 0, but can be parabolic. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ultrafast nonlinear response of AlGaAs/InAlGaAs MQW photonic crystal waveguides
Authors: Murzyn P. , Garcia‐Déniz A. Z. , Fox A. M. , Wells J.‐P. R. , Whittaker D. M. , Skolnick M. S. , Krauss T. F. , Roberts J. S. 
Published: November 2005

AbstractWe report ultrafast optical tuning of the reflection properties of MQW AlGaAs/InAlGaAs 1D photonic crystal waveguides using a reflection geometry, pump‐probe technique. Very fast pump‐induced shifts of photonic resonances between 800–900 nm by up to 18 nm nanometers are demonstrated. This is followed by a fast decay which varies from 5 to 30 ps depending on the sample dimensions. Together with the maximum reflectivity change of ΔR /R > 30%, this demonstrates excellent potential for application of photonic crystals as ultrafast nonlinear switches with decay times depending on the structure period. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)