bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Elevated Temperature Annealing on the Structure and Hardness of Copper/niobium Nanolayered Films
Authors: Misra A. , Hoagland R.G.
Published: August 2005

We investigated the effects of elevated temperature vacuum annealing on the morphological stability and hardness of self-supported, textured, polycrystalline Cu–Nb nanolayered films with individual layer thickness varying from 15 to 75 nm. Films with layer thickness greater than approximately 35 nm are found to resist layer pinch-off and spheroidization even after long annealing times at 700 °C, while films with layer thickness ∼15 nm exhibit layer pinch-off and evolve into an equiaxed grain microstructure. Nanoindentation measurements indicate almost no change in hardness after annealing for films that retain the layered morphology, in spite of the increase of in-plane grain dimensions. Significant decreases in hardness are noted for films that develop a coarsened equiaxed grain microstructure after annealing. The mechanism that leads to the development of a thermally stable nanolayered structure is analyzed. Also, the relative effects of in-plane grain size and layer thickness on the multilayer hardness are discussed.
Neutron Rietveld Analysis for Optimized CaMgSi2O6:Eu2+ and its Luminescent Properties
Authors: Im Won Bin , Kim Yong-Il , Kang Jong Hyuk , Jeon Duk Young , Jung Ha Kyun , Jung Kyeong Youl
Published: August 2005

We optimized synthesis conditions of blue-emitting CaMgSi2O6:Eu2+ (CMS:Eu2+) with conventional solid-state reaction and successfully determined structure parameters by Rietveld refinement method with neutron powder diffraction data. The final weighted R-factor Rwp was 6.42% and the goodness-of-fit indicator S (= Rwp/Re) was 1.34. The refined lattice parameters of CMS:Eu2+ were a = 9.7472(3) Å, b = 8.9394(2) Å, and c = 5.2484(1) Å. The β angle was 105.87(1)°. The concentration quenching process was observed, and the critical quenching concentration of Eu2+ in CMS:Eu2+ was about 0.01 mol and critical transfer distance was calculated as 12 Å. With the help of the Rietveld refinement and Dexter theory, the critical transfer distance was also calculated as 27 Å. In addition, the dominant multipolar interaction of CMS:Eu2+ was investigated from the relationship between the emission intensity per activator concentration and activator concentration. The dipole–dipole interaction was a dominant energy transfer mechanism of electric multipolar character of CMS:Eu2+.
Effects of Sub-ångstrom (pico-scale) Structure of Surfaces on Adhesion, Friction, and Bulk Mechanical Properties
Authors: Israelachvili Jacob , Maeda Nobuo , Rosenberg Kenneth J. , Akbulut Mustafa
Published: August 2005

We review experimental results—over the past 10–15 years and more recent theoretical modeling and computer simulations—on the effects of surface subnanoscale texture on adhesion and friction and the implications for certain mechanical properties of materials such as Mode I and Mode II failure. Examples and comparisons include surfaces that are adhesive or nonadhesive, rough or smooth, hard or soft (e.g., viscoelastic polymers), dry (unlubricated) or lubricated. One important conclusion is that the ultrafine picoscale details of a surface lattice or its roughness (“texture”) can be the most important factor in determining its friction and Mode II fracture, whereas such effects are less important for determining adhesion forces and Mode I fracture processes. Such studies are also clarifying the molecular and atomic basis of many well-established adhesion and tribological laws and empirical observations and are revealing new fundamental insights and relationships between nanoscale (molecular) and macroscale processes.
Spherical Indentation Creep Following Ramp Loading
Authors: Oyen Michelle L.
Published: August 2005

Elastic-viscoelastic correspondence, utilizing Boltzmann integral operators, was used to generate displacement–time solutions for spherical indentation testing of viscoelastic materials. Solutions were found for creep following loading at a constant loading rate and compared with step-loading solutions. Experimental creep tests were performed with different loading rate–peak load level combinations on glassy and rubbery polymeric materials. The experimental data were fit to the spherical indentation ramp–creep solutions to obtain values of shear modulus and time-constants; good agreement was found between the experimental results and known modulus values. A multiple ramp-and-hold protocol was examined for the measurement of creep responses at several loads (and depths) within the same test. Emphasis is given to the use of multiple experiments (or multiple levels within a single experiment) to test a priori assumptions made in the correspondence solutions regarding linear viscoelastic material behavior and the creep function.
Amorphization of Cristobalite at High Temperature in Vacuum
Authors: Xu Chang-Ming , Wang S.W. , Huang X.X. , Guo J.K.
Published: August 2005

Amorphous transition behavior of silica polymorphs under high pressure has been extensively studied by using diamond-anvil cells or shock wave technologies at ambient temperature. Here, we report the amorphization of crystalline silica fiber in cristobalite polymorph in the temperature range of 1050–1350 °C without pressure applied in vacuum. X-ray diffraction, infrared spectra, and Raman spectra illustrated the transition. Raman spectra revealed that no significant changes had happened to the SiO4unit during the transition. It is suggested that the driven-off of interstitial oxygen attributed to the transition and the reaction between the diffusing hydrogen and interstitial oxygen promoted the process.
Ferromagnetic Cobalt Nanodots, Nanorices, Nanowires and Nanoflowers by Polyol Process
Authors: Cha Seung I. , Mo Chan B. , Kim Kyung T. , Hong Soon H.
Published: August 2005

Various shapes and sizes of colloidal Co nanoparticles were fabricated by the polyol process using Co(acac)3, 1,2-hexadecanediol, oleylamine, and oleic acid within octylether. The rice-shaped Co nanoparticles with size of 30 nm and aspect ratio of 1.8 can be fabricated into a self-assembled form without assistance of surfactants. The addition of oleylamine as surfactant decreased the particle size and aspect ratio, and the addition of oleic acid made the surface of particle faceted without decreasing particle size from that of rice shape. The mixture of oleylamine and oleic acid produce differently shaped Co nanoparticles, including nanoprism, nanowire, and nanoflower according to the ratio of components, total amount of surfactant mixture, and reaction time. The fabricated nanoparticles showed ferromagnetic properties. These results showed that the various size and shape of metallic nanoparticles can be fabricated by the polyol process into controlled forms.
Investigation on Carbonizing Behaviors of Nanometer-sized Cr2O3 Particles Dispersed on Alumina Particles by Metalorganic Chemical Vapor Deposition in Fluidized Bed
Authors: Lin Hao-Tung , Huang Jow-Lay , Lo Wen-Tse , Wei Wen-Cheng J.
Published: August 2005

Nanoscaled Cr2O3 powder with an average particle size of 20–40 nm, coated on alumina particles, has been produced by means of chemical vapor deposition (CVD) in a fluidized chamber, using the pyrolysis of Cr(CO)6 precursor. Amorphous and crystalline Cr2O3 particles were obtained when the temperatures of the pyrolysis were 300 and 400 °C, respectively. To prepare nanoscaled Cr3C2 powder from the nanometer-sized Cr2O3, carbonizing behavior of the Cr2O3 particles was investigated. It was found that, when amorphous Cr2O3 powders were carbonized in graphite furnace at 1150 °C for 2 h in vacuum (10−3 Torr), the powder was transformed into Cr3C2, while the crystalline Cr2O3 was transformed into a mixture of Cr7C3 and Cr3C2. The examinations by x-ray diffraction, transmission electron microscopy, and energy dispersive spectroscopy confirmed the transformation of the nano-sized Cr3C2 powders. The results of thermogravimetry and differential thermal analysis indicated that the transformation temperature was ∼1089 °C for amorphous Cr2O3 and ∼1128 °C for crystalline Cr2O3.
Elastic Deformation of Coating/substrate Composites in Axisymmetric Indentation
Authors: Sakai M. , Zhang J. , Matsuda A.
Published: August 2005

Elastic deformation of coating/substrate composites was examined for axisymmetric indentations with three different geometries of flat-ended cylinder, sphere, and cone. Intensive theoretical considerations were made for the Boussinesq problems not only in its Fredholm integral equation of the second kind, but also in its Green function using the principle of superposition for the approximated contact stress distribution. The agreement and the disagreement between these two different numerical/analytical assessments for elastic surface deformations are discussed. Along with these theoretical considerations, experimental scrutiny was conducted for the theoretical predictions for spherical indentation by the use of a sol-gel-derived MeSiO3/2 film coated on a soda-lime glass plate. A novel technique is also proposed for estimating in a simultaneous manner the elastic moduli of both the coating film and of the substrate or the elastic modulus of the film and its thickness in spherical indentation tests.
Damages and Microstructural Variation of High-lead and Eutectic SnPb Composite Flip Chip Solder Bumps Induced by Electromigration
Authors: Liu Yeh-Hsiu , Lin Kwang-Lung
Published: August 2005

The electromigration behavior of the high-lead and eutectic SnPb composite solder bumps was investigated at 150 °C with 5 × 103 A/cm2 current stressing for up to 1711 h. The diameter of the bumps was about 125 μm. The underbump metallization (UBM) on the chip side was sputtered Al/Ni(V)/Cu thin films, and the Cu pad on the board side was plated with electroless Ni/Au. It was observed that damages occurred in the joints in a downward electron flow (from chip side to the substrate side), while those joints having the opposite current polarity showed only minor changes. In the case of downward electron flow, electromigration damages were observed in the UBM and solder bumps. The vanadium in Ni(V) layer was broken under current stressing of 1711 h while it was still intact after current stressing of 1000 h. The electron probe microanalyzer (EPMA) elemental mapping clearly shows that the Al atoms in the trace migrated through the UBM into the solder bump during current stressing. Voids were found in the solder bump near the UBM/solder interface. The Sn-rich phases of the solder bumps showed gradual streaking and reorientation upon current stressing. This resulted in the formation of uniaxial Sn-rich phases in the middle of the solder bump, while the columnar and fibrous Sn-rich phases were formed in the surrounding regions. The formation mechanism of electromigration-induced damage to the UBM structure and solder bump were discussed.
Sodium Ion Conduction in Plastic Phases: Dynamic Coupling of Cations and Anions in the Picosecond Range
Authors: Wilmer D. , Feldmann H. , Lechner R.E. , Combet J.
Published: August 2005

Results of simple computer simulations and model calculations for ion conducting rotor phases are compared to quasi-elastic neutron scattering data from solid solutions of sodium orthophosphate and sodium sulphate, xNa2SO4⋅(1 − x)Na3PO4. These materials are not only sodium fast-ion conductors in their high-temperature cubic phases but also show considerable dynamic reorientation disorder of their tetrahedral anions. At an elastic energy resolution of about 100 μeV, neutron spectrometry monitored oxygen scattering due to anion reorientation which occurs on the picosecond time scale. This thermally activated process exhibits activation energies between 0.184 eV (x = 0.0) and 0.052 eV (x = 0.5). Analysis of the quasielastic intensities as a function of scattering vector Q gives clear evidence of the involvement of cations in the anion reorientation. Increasing the elastic resolution to about 1 μeV full width at half-measure (FWHM) (thereby shifting the dynamic window to the nanosecond scale) allowed examination of sodium diffusion in xNa2SO4⋅(1 − x)Na3PO4. This process consists predominantly of thermally activated jumps between tetrahedrally coordinated sites, the activation energies ranging from 0.64 eV for x = 0.0 to 0.30 eV for x = 0.5.
Representative Strain of Indentation Analysis
Authors: Ogasawara Nagahisa , Chiba Norimasa , Chen Xi
Published: August 2005

Indentation analysis based on the concept of representative strain offers an effective way of obtaining mechanical properties, especially work-hardening behavior of metals, from reverse analysis of indentation load–displacement data, and does not require measuring of the projected contact area. The definition of representative strain adopted in previous studies [e.g., Dao et al., Acta Mater.49, 3899 (2001)] has a weak physical basis, and it works only for a limited range in some sense of engineering materials. A new indentation stress-state based formulation of representation is proposed in this study, which is defined as the plastic strain during equi-biaxial loading. Extensive numerical analysis based on the finite element method has shown that with the new formulation of representative strain and representative stress, the critical normalized relationship between load and material parameters is essentially independent of the work-hardening exponent for all engineering materials, and the results also hold for three distinct indenter angles. The new technique is used for four materials with mechanical properties outside the applicable regime of previous studies, and the reverse analysis has validated the present analysis. The new formulation based on indentation stress-state based definition of representative strain has the potential to quickly and effectively measure the mechanical properties of essentially all engineering materials as long as their constitutive behavior can be approximated into a power-law form.
Partial Dehydration of the Retinal Binding Pocket and Proof for Photochemical Deprotonation of the Retinal Schiff Base in Bicelle Bacteriorhodopsin Crystals
Authors: Sanii Laurie S. , El‐Sayed Mostafa A.
Published: August 2005

In bicelle bacteriorhodopsin (bcbR) crystals, the protein has a different structure from both native bacteriorhodopsin (bR) and in‐cubo bR (cbR) crystals. Recently, we studied the ability of bcbR crystals to undergo the photocycle upon laser excitation, characterized by the appearance of the M intermediate by single crystal resonance Raman spectroscopy. Calculation of the M lifetime by flash photolysis experiments demonstrated that in our bcbR crystals, the M rise time is much faster than in the native or cbR crystals, with a decay time that is much slower than these other two forms. Although it is now known that the bcbR crystals are capable of photochemical deprotonation, it is not known whether photochemical deprotonation is the only way to create the deprotonated Schiff base in the bcbR crystals. We measured both the visible and Raman spectra of crystals dried under ambient lighting and dried in the dark in order to determine whether the retinal Schiff base is able to thermally deprotonate in the dark. In addition, changes in the visible spectrum of single bcbR crystals under varying degrees of hydration and light exposure were examined to better understand the retinal binding environment.
Long-Term Proliferation of Human Embryonic Stem Cell–Derived Neuroepithelial Cells Using Defined Adherent Culture Conditions
Authors: Shin Soojung , Mitalipova Maisam , Noggle Scott , Tibbitts Deanne , Venable Alison , Rao Raj , Stice Steven L.
Published: August 2005

Research on the cell fate determination of embryonic stem cells is of enormous interest given the therapeutic potential in regenerative cell therapy. Human embryonic stem cells (hESCs) have the ability to renew themselves and differentiate into all three germ layers. The main focus of this study was to examine factors affecting derivation and further proliferation of multipotent neuroepithelial (NEP) cells from hESCs. hESCs cultured in serum-deprived defined medium developed distinct tube structures and could be isolated either by dissociation or adherently. Dissociated cells survived to form colonies of cells characterized as NEP when conditioned medium from human hepatocellular carcinoma HepG2 cell line (MEDII) was added. However, cells isolated adherently developed an enriched population of NEP cells independent of MEDII medium. Further characterization suggested that they were NEP cells because they had a similar phenotype profile to in vivo NEP cells and expression SOX1, SOX2, and SOX3 genes. They were positive for Nestin, a neural intermediate filament protein, and Musashi-1, a neural RNA-binding protein, but few cells expressed further differentiation markers, such as PSNCAM, A2B5, MAPII, GFAP, or O4, or other lineage markers, such as muscle actin, α fetoprotein, or the pluripotent marker Oct4. Further differentiation of these putative NEP cells gave rise to a mixed population of progenitors that included A2B5-positive and PSNCAM-positive cells and postmitotic neurons and astrocytes. To proliferate and culture these derived NEP cells, ideal conditions were obtained using neurobasal medium supplemented with B27 and basic fibroblast growth factor in 5% oxygen. NEP cells were continuously propagated for longer than 6 months without losing their multipotent cell characteristics and maintained a stable chromosome number.
Interactions Between Human Mesenchymal Stem Cells and Natural Killer Cells
Authors: Sotiropoulou Panagiota A. , Perez Sonia A. , Gritzapis Angelos D. , Baxevanis Constantin N. , Papamichail Michael
Published: August 2005

Mesenchymal stem cells (MSCs) are multipotent progenitor cells representing an attractive therapeutic tool for regenerative medicine. They possess unique immunomodulatory properties, being capable of suppressing T-cell responses and modifying dendritic cell differentiation, maturation, and function, whereas they are not inherently immunogenic, failing to induce alloreactivity to T cells and freshly isolated natural killer (NK) cells. To clarify the generation of host immune responses to implanted MSCs in tissue engineering and their potential use as immunosuppressive elements, the effect of MSCs on NK cells was investigated. We demonstrate that at low NK-to-MSC ratios, MSCs alter the phenotype of NK cells and suppress proliferation, cytokine secretion, and cyto-toxicity against HLA-class I– expressing targets. Some of these effects require cell-to-cell contact, whereas others are mediated by soluble factors, including transforming growth factor–β1 and prostaglandin E2, suggesting the existence of diverse mechanisms for MSC-mediated NK-cell suppression. On the other hand, MSCs are susceptible to lysis by activated NK cells. Overall, these data improve our knowledge of interactions between MSCs and NK cells and consequently of their effect on innate immune responses and their contribution to the regulation of adaptive immunity, graft rejection, and cancer immunotherapy.
Isolation and Angiogenesis by Endothelial Progenitors in the Fetal Liver
Authors: Cherqui Stephanie , Kurian Sunil M. , Schussler Olivier , Hewel Johannes A. , Yates John R. , Salomon Daniel R.
Published: August 2005

Endothelial progenitor cells (EPCs) have significant therapeutic potential. However, the low quantity of such cells available from bone marrow and their limited capacity to proliferate in culture make their use difficult. Here, we present the first definitive demonstration of the presence of true EPCs in murine fetal liver capable of forming blood vessels in vivo connected to the host's vasculature after transplantation. This population is particularly interesting because it can be obtained at high yield and has a high angiogenic capacity as compared with bone marrow–derived EPCs. The EPC capacity is contained within the CD31+Sca1+ cell subset. We demonstrate that these cells are dependent for survival and proliferation on a feeder cell monolayer derived from the fetal liver. In addition, we describe a novel and easy method for the isolation and ex vivo proliferation of these EPCs. Finally, we used gene expression profiling and tandem mass spectrometry proteomics to examine the fetal liver endothelial progenitors and the feeder cells to identify possible proangiogenic growth factor and endothelial differentiation-associated genes.
Visualizations of Boger fluid flows in a 4:1 square–square contraction
Authors: Alves M. A. , Pinho F. T. , Oliveira P. J.
Published: August 2005

Visualizations of the 3‐D flow in a 4:1 square–square sudden contraction for two viscoelastic Boger fluids and two Newtonian fluids were carried out at low Reynolds numbers. In these creeping flow conditions, the vortex length remained unchanged for Newtonian fluids, whereas a nonmonotonic variation with flow rate was observed for the Boger fluids. Initially, the corner vortex slightly increased with flow rate to a local peak at a Deborah number of De2 ≈ 6, before decreasing significantly to a minimum at De2 ≈ 15 (De2 is based on downstream characteristics). Finally, for Deborah numbers > 20 there was intense vortex enhancement until a periodic flow was established at higher flow rates (De2 ≈ 45–52). The strong elastic vortex enhancement was preceded by the appearance of diverging streamlines on the approach flow and, for the Boger fluid with higher polymer concentration, vortex enhancement took place through a lip vortex mechanism. AIChE J, 2005
Properties of polyacrylamide‐based hydrogels prepared by electron beam irradiation for possible use as bioactive controlled delivery matrices
Authors: Abd El‐Rehim H. A. , Hegazy El‐Sayed A. , Abd El‐Mohdy H. L.
Published: August 2005

Polyacrylamide/poly(ethylene oxide) (PAAm/PEO) crosslinked hydrogels were designed for controlled delivery of an herbicide, Atrazine, which is used in the agricultural field. Atrazine was incorporated into a PAAm/PEO matrix during an electron beam irradiation process. The Atrazine release rate from matrices prepared under different conditions was studied to determine which factors have the most affect and control over the PAAm/PEO matrix release property. The copolymer blend composition, copolymer gel content, and irradiation dose greatly affected the Atrazine release rate. In addition, its release rate was influenced by the pH and temperature of the matrix‐surrounding medium. The Atrazine release rate decreased as the pH increased, but it increased as the temperature increased. The properties of the prepared crosslinked hydrogels may make them acceptable for practical use as bioactive controlled release matrices. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1262–1270, 2005
Micro‐void toughening of thermosets and its mechanism
Authors: Kim Nam Ho , Kim Ho Sung
Published: August 2005

Void toughening is studied using epoxy resin. Voids were produced mechanically without any chemical agents so that it was possible to isolate the role of micro‐voids from other factors. Toughness of the epoxy resin owing to voids was improved over that of the control by an order of magnitude. The toughening mechanism was found to be strongly related to intervoid distance and, hence, to void‐to‐crack distance. Large deformation bands between the crack and voids were deduced to be the source of toughening. The intervoid distance was directly measured on scanning electron microscope photos. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1290–1295, 2005
Preparation of porous spherical MgCl2/SiO2 complex support as precursor for catalytic propylene polymerization
Authors: Jiang Tao , Chen Wei , Zhao Feng , Liu Yuexiang , Wang Ruen , Du Hongbin , Zhang Tianyi
Published: August 2005

The MgCl2/SiO2 complex support was prepared by spray drying using alcoholic suspension, which contained MgCl2 and SiO2. The complex support reacted with TiCl4 and di‐n‐butyl phthalate, giving a catalyst for propylene polymerization. The catalyst was spherical and porous with high specific surface area. TEA was used as a cocatalyst, and four kinds of alkoxysilane were used as external donors. The bulk polymerization of propylene was studied with the catalyst system. The effect of the reaction conditions and external donor on the polymerization were investigated. The results showed that the catalyst had high activity, high stereospecificity, and sensitive hydrogen responsibility. Polypropylene has good grain morphology because of duplicating the morphology of the catalyst. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1296–1299, 2005
Thermal analysis of novel underfill materials with optimum processing characteristics
Authors: Liu Yang , Wang Yi‐Feng , Gerasimov Timofey G. , Heffner Kenneth H. , Harmon Julie P.
Published: August 2005

This work encompasses the development of low‐viscosity cyclic oligomer underfill formulations that cure without heat evolution. Boron nitride, silica‐coated aluminum nitride, and alumina ceramic powders were used as fillers in cyclic butylene terephthalate oligomer melts. The melts were heated with a suitable catalyst to induce polymerization. The effects of the filler type and composition on the thermal and mechanical properties of the poly(butylene terephthalate)/filler composites were examined with differential scanning calorimetry, temperature‐modulated differential scanning calorimetry, thermogravimetric analysis, thermomechanical analysis, and dynamic mechanical analysis. Scanning electron microscopy was employed to elucidate the morphology of these composites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1300–1307, 2005
Preparation of starch‐graft‐poly(acrylamide)/attapulgite superabsorbent composite
Authors: Li An , Liu Ruifeng , Wang Aiqin
Published: August 2005

A novel starch‐graft‐poly(acrylamide)/attapulgite superabsorbent composite was synthesized by graft copolymerization reaction of starch, acrylamide (AM), and attapulgite micropowder using N.N‐methylene‐bisacrylamide (MBA) as a crosslinker and ammonium persulphate (APS) as an initiator in aqueous solution, followed by hydrolysis with sodium hydroxide. The effects on water absorbency, such as amount of crosslinker, initiator, attapulgite, weight ratio of acrylamide to starch in the feed, gelatinization conditions of starch and molar ratio of NaOH to acrylamide, and so forth, were investigated. These superabsorbent composites were characterized by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The water absorbencies for these superabsorbent composites in water and saline solution were investigated, and water retention tests were carried out. Results obtained from this study showed that the water absorbency of superabsorbent composite synthesized under optimal synthesis conditions with an attapulgite content of 10% exhibit absorption of 1317 g H2O/g sample and 68 g H2O/g sample in distilled water and in 0.9 wt % NaCl solution, respectively. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1351–1357, 2005
Thermally induced coil‐to‐helix transition of sodium gellan gum with different molar masses in aqueous salt solutions
Authors: Ogawa Etsuyo , Takahashi Rheo , Yajima Hirofumi , Nishinari Katsuyoshi
Published: August 2005

Using 5 samples of well‐purified Na‐gellans (Na‐gellans G1–G5, weight‐average molar mass Mw = 120 × 103−32 × 103 at 40°C), the effects of molar mass on the coil‐to‐double‐helix transition in aqueous solutions with 25 mM NaCl were studied by light scattering and circular dichroism (CD) measurements, viscometry, and differential scanning calorimetry (DSC). From the temperature dependence of Mw, molar ellipticity at 201nm [θ]201, intrinsic viscosity [η], and DSC exothermic curves, it was found that the coil‐to‐double‐helix transitions for G1–G5 samples took place at almost the same temperature. The [η] and Mw obtained in the temperature range from 40 to 25°C can be explained by a simple coil/double‐helix equilibrium model using the double‐helix contents determined from CD data. The van't Hoff's transition enthalpy ΔHvH of Na‐gellans depended on Mw. It is concluded that the coil‐to‐double‐helix transitions of Na‐gellans are all‐or‐none type transitions, and are accelerated with increasing Mw. © 2005 Wiley Periodicals, Inc. Biopolymers 79: 207–217, 2005

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Prenatal depression, mode of delivery and perinatal dissociation as predictors of postpartum posttraumatic stress: an empirical study
Authors: van Son Maarten , Verkerk Gerda , van der Hart Onno , Komproe Ivan , Pop Victor
Published: August 2005

This longitudinal study evaluated the validity of earlier established predictors for postpartum posttraumatic stress (postpartum PTS) in a community sample of women (n = 248) in the Netherlands. Data was collected at 32 weeks gestation and at 3, 6 and 12 months postpartum by means of structured interviews. On the basis of the literature, an etiological model was defined with two pathways for the prediction of postpartum PTS. The model encompassed prepartum factors (e.g. depression in family, depression during life and depression during gestation), peripartum factors (e.g. type of delivery, experienced pain, social support by medical staff, supply of information and perinatal dissociation), and postpartum factors (e.g. postpartum depression). The model was evaluated by LISREL. Two pathways for postpartum PTS were confirmed: (1) delivery‐related stressors predict postpartum PTS and (2) previous depression predicts postpartum PTS. Implications for mental health care during and after delivery are discussed. Copyright © 2005 John Wiley & Sons, Ltd.
Can patients specify treatment parameters? a preliminary investigation
Authors: Carey Timothy A.
Published: August 2005

In this paper I provide data that were obtained when patients made decisions regarding the scheduling of treatment sessions. I outline relevant information from the literature and describe Perceptual Control Theory as the theoretical basis of this work. The implications and limitations of the data are discussed as well as suggestions for future research. The data are interpreted as preliminary evidence that patients can take responsibility for decisions made during psychological treatment programs. Copyright © 2005 John Wiley & Sons, Ltd.
Improving the Properties of Organic Dyes by Molecular Encapsulation
Authors: Arunkumar Easwaran , Forbes Christopher C. , Smith Bradley D.
Published: August 2005

There is a demand for new methods of protecting organic dyes from aggregation effects and photochemical degradation. The purpose of this microreview is to summarize the recent attempts to improve the properties of dyes by molecular encapsulation. Organic dyes have been encapsulated inside inorganic matrices such as molecular sieves, and molecular containers such as cyclodextrins, cucurbiturils, dendrimers, and self‐assembled gels. Another strategy is permanent protection of the dye as the thread component in a rotaxane. Molecular encapsulation is an attractive supramolecular strategy because it is inherently flexible and does not necessarily require time‐consuming synthetic processes. Indeed, molecular encapsulation is an effective way to recycle familiar dyes that are already well‐characterized. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Characterization of hydroxyaromatic compounds in vegetable oils by capillary electrophoresis with direct injection in an oil‐miscible KOH/propanol/methanol medium
Authors: Mendonça Carla R. B. , Bica Clara I. D. , Piatnicki Clarisse M. S. , Simó‐Alfonso Ernesto F. , Ramis‐Ramos Guillermo
Published: August 2005

The separation of hydroxyaromatic compounds in vegetable oils, including synthetic antioxidants (3‐tert‐butyl‐4‐hydroxyanisol and 2,6‐di‐tert‐butyl‐4‐hydroxytoluene), E‐vitamers and other natural oil components, by nonaqueous capillary electrophoresis in an oil‐miscible background electrolyte (BGE) was investigated. The BGE contained 40 mM KOH in a methanol/1‐propanol (PrOH) mixture (15:85 v/v). The oil samples were 1:1 diluted with PrOH and directly injected in the capillary. Under negative polarity (cathode at the injection end), the anionic solutes moved faster than the electroosmotic flow, being well‐resolved among them and from the triacylglycerols. Using virgin palm, extra virgin olive, wheat germ, virgin soybean and other oils, the capability of the procedure to quickly yield a characteristic profile of the biophenols present in the sample was demonstrated. The α‐, (β + γ)‐ (as unresolved pair) and δ‐tocopherols of a soybean oil sample were quantified.
Effect of polymer matrix and glycerol on rapid single‐strand conformation polymorphism analysis by capillary and microchip electrophoresis for detection of mutations in K‐ras gene
Authors: Endo Yuki , Zhang Lihua , Katashima Rumi , Itakura Mitsuo , Doherty Erin A. S. , Barron Annelise E. , Baba Yoshinobu
Published: August 2005

We present the rapid single‐strand conformation polymorphism (SSCP) analysis by capillary and microchip electrophoresis to detect the mutations in K‐ras gene. Parameters that might affect the analysis of mutation in K‐ras gene, such as the polymer and the additive in the sieving matrix, have been studied systematically. Under the optimal conditions, the analysis of seven mutants of K‐ras gene could be finished within 10 min by capillary electrophoresis (CE). Furthermore, with the wild‐type gene as the inner standard, the analysis accuracy of mutations could be improved. In addition, by studying the properties of polymer solutions, the matrix suitable for microchip electrophoresis was found, and the detection of mutations in K‐ras gene could be further shortened to 1 min.
Simultaneous separation of organomercury species by nonaqueous capillary electrophoresis using methanol containing acetic acid and imidazole
Authors: Peng Zhen‐Lei , Qu Feng , Song Guanquan , Lin Jin‐Ming
Published: August 2005

A simple and rapid nonaqueous capillary electrophoresis method for simultaneous separation of four kinds of mercury species, namely inorganic mercury, methylmercury, ethylmercury, and phenylmercury, is reported. The effective mobilities of organomercury in aqueous and nonaqueous electrolytes were compared. Imidazole was confirmed not only as a co–ion for the separation but also as an online complexing reagent for mercury species. The optimum conditions for separation were achieved by using methanol solvent containing 0.15 M acetic acid and 15 mM imidazole as electrolyte. The sensitive detection of mercury species was accomplished at 191 nm.
Investigation of the effect of ionic strength of Tris‐acetate background electrolyte on electrophoretic mobilities of mono‐, di‐, and trivalent organic anions by capillary electrophoresis
Authors: Koval Dušan , Kašička Václav , Zusková Iva
Published: August 2005

The effect of ionic strength of the background electrolyte (BGE) composed of tris(hydroxymethyl)aminomethane (Tris) and acetic acid on the electrophoretic mobility of mono‐, di‐ and trivalent anions of aliphatic and aromatic carboxylic and sulfonic acids was investigated by capillary zone electrophoresis (CZE). Actual ionic mobilities of the above anions were determined from their CZE separations in Tris‐acetate BGEs of pH 8.1 to 8.2 in the 3 to 100 mM ionic strength interval at constant temperature (25°C). It was found that the ionic strength dependence of experimentally determined actual ionic mobilities does not follow the course supposed by the classical Onsager theory. A steeper decrease of actual ionic mobilities with the increasing ionic strength of BGE and a higher estimated limiting mobility of the anions than that found in the literature could be attributed to the specific behavior of the Tris‐acetate BGEs. Presumably, not only a single type of interaction of anionic analytes with BGE constituents but rather the combination of effects, such as ion association or complexation equilibria, seems to be responsible for the observed deviation of the concentration dependence of the actual ionic mobilities from the Onsager theory. Additionally, several methods for the determination of limiting ionic mobilities from CZE measured actual ionic mobilities were evaluated. It turned out that the determined limiting ionic mobilities significantly depend on the calculation procedure used.
The influence of tungsten compounds on the synthesis and properties of polyaniline
Authors: Stejskal Jaroslav , Trchová Miroslava , Holler Petr , Sapurina Irina , Prokeš Jan
Published: August 2005

Aniline was oxidized in an acidic aqueous medium with ammonium peroxydisulfate in the presence of various concentrations of tungsten compounds. The oxidation has two phases: an induction period followed by the exothermic polymerization. The course of oxidation was monitored by recording the reaction temperature or pH. The introduction of 2 mol% sodium tungstate (relative to aniline) prolonged the induction period from 5 to 30 min. Such molar concentration of tungstosilicic acid delayed the onset of polymerization by 120 min. The effect of sodium molybdate was less pronounced; sodium chromate had no influence on the course of oxidation. The presence of tungsten compounds had not affected the conductivity and molecular weight of the produced polyaniline. FTIR spectra and density determinations have proved that tungstate and tungstosilicate counter‐ions have been incorporated into polyaniline when they were present in the reaction mixture. Copyright © 2005 Society of Chemical Industry
The Skyrme model with a U*(1) gauged Wess‐Zumino term in a noncommutative spacetime
Authors: Mieck B.
Published: August 2005

The Skyrme model is generalized for a noncommutative spacetime with the Weyl‐operators of SU(2) matrices and the corresponding star‐product. The unitary condition and the topological current can be extended to star‐exponential matrices. The Wess‐Zumino term which breaks unphysical symmetries of the Skyrme action is gauged with the U*(1) group to allow for electromagnetic processes in a noncommutative spacetime. Apart from corrections to the anomalous decay γ→π0π+π– in commuting spacetime, the additional anomalous process γ→π0π0π0 is found in the U*(1) gauged Wess‐Zumino action for a noncommutative spacetime.
Gravitational scattering of massless scalars in QFT and superstring theory
Authors: Pašukonis J.
Published: August 2005

In this paper we perform the calculation of the gravitational scattering amplitude for 4 massless scalars in quantum field theory and Type II superstring theory. We show that the results agree, providing an example of how gravity is incorporated in the superstring theory. During the calculation we quantize gravitational action to derive graviton propagator and interaction vertex with massless scalar. We also calculate general 3‐point and 4‐point scattering amplitudes in SST for open and closed massless strings in NS sector.
Joint density of states at extended defects in CVD diamond, observed via highly spatially resolved electron energy loss spectroscopy
Authors: Bangert U. , Harvey A. J. , Schreck M. , Hoermann F.
Published: August 2005

Results are presented of highly spatially resolved electron energy loss spectroscopy conducted on extended defects in CVD diamond. Analysis of the low energy loss regime shows that the joint density of states in the vicinity of dislocation nodes and secondary stacking faults, formed by incomplete dissociation of partial dislocations, can be different from that in perfect bulk material. Extra intensity in the joint density of states below the conduction band edge and in the lower conduction band was observed, with the most marked increase at around 6 eV. This is an indicator for sp2‐bond character. Spatially these states are too widely dispersed to be innate to the dislocation cores, and they are thought to arise from point defect segregation to extended defects. Kramers–Kronig and valence band plasmon analysis suggest an increase in the effective electron density and mass at the dislocation nodes. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth and characterization of near‐atomically flat, thick homoepitaxial CVD diamond films
Authors: Bogdan G. , Nesládek M. , D'Haen J. , Maes J. , Moshchalkov V. V. , Haenen K. , D'Olieslaeger M.
Published: August 2005

Diamond films were grown in an ASTeX MW PE CVD reactor. The effect of pre‐growth etching with a O2/H2 plasma and the influence of the methane concentration on growth on type Ib (100) HPHT synthetic diamonds were investigated. By controlling step flow growth we were able to prepare optical quality thick diamond films, free of hillocks and unepitaxial crystallites, with a relatively high growth rate of 4 to 5 µm/h using higher pressures and methane concentrations than standard growth conditions in combination with a modified substrate holder. All diamond films were characterized by optical microscopy, SEM, AFM and Raman spectroscopy. The mean roughness (Rms) of the films grown with a thickness of 120 µm was approximately 0.5 to 0.8 nm for scanning regions of 5 × 5 µm2. For the first time nearatomically flat films thicker than 200 µm could be prepared. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Introduction to symmetry methods in the solution of differential equations that occur in chemistry and chemical biology
Authors: Hydon Peter E.
Published: August 2005

This article is a short overview of the main ways in which symmetries can be used to obtain exact information about differential equations. It is written for a general scientific audience; readers do not need any previous knowledge of symmetry methods. The information yielded by symmetry methods may include the general solution of a given differential equation, special “invariant solutions” (such as similarity solutions), and conservation laws. Several symmetry methods have been implemented as computer algebra packages, which can be used by nonspecialists. Toward the end of the study, there is a brief outline of some recent developments in symmetry methods that await translation into symbolic algebra. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Use of symbolic and numeric computation techniques in analysis of biochemical reaction networks
Authors: Yildirim Necmettin
Published: August 2005

Mathematical models of biochemical reaction networks involve nonlinear differential equations with a number of parameters whose values are generally not known a priori. Analysis of such networks includes both analytical and numerical work. The analytical part of such analysis often requires manipulation with massive algebraic expressions that may become challenging due to the inherent nonlinearities and unknown parameters in the model. Computer algebra systems (CASs), which are also capable of performing calculations with symbols and to generate ready‐to‐use computer codes for numerical computations, are excellent tools in such analysis. The present work gives a brief description of how we can benefit from computer algebra to overcome such difficulties and combine symbolic and numeric computation techniques in such analysis with several illustrative biochemical reaction networks. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
The usefulness of tests in anorectal disease
Authors: Parks T. George
Published: August 2005

Specialized tests of anorectal function are designed to complement but not to replace good clinical examination and sound professional judgement. The different methods of recording pressure changes have advantages and disadvantages. Poor correlation exists when data recorded using miniature balloons are compared with data from microtransducers. Prolonged ambulatory monitoring of anal sphincter and rectal pressure reveal that spontaneous transient episodes of sphincter relaxation are demonstrable in normal subjects. In the investigation of patients with possible traction injury to the pudendal nerve, electromyography and pudendal nerve terminal motor latency data are more precise than manometry data. Good correlation between noninvasive surface electromyography using an intraanal plug electrode and anal manometry can be attained. Mapping of sphincter defects using concentric needle technology is reasonably accurate but distinctly painful. Dynamic defecography readily demonstrates abnormalities of the rectal wall. The division between what is normal and what is clinically relevant is rather imprecise. Comparative studies of sonographic and electromyographic mapping of sphincter defects give good correlation. Recent application of fine hooked electrodes have demonstrated periodic episodes of smooth muscle and sphincter relaxation. The saline infusion test and balloon expulsion test help to accurately quantify the difficulty patients experience in retention or evacuation, respectively. Perineometry is a simple, rapid, noninvasive method of measuring the extent of perineal descent on straining. Although reproducible, it tends to underestimate the degree of descent when compared with the radiological method but it avoids the use of ionized radiation.
Pre‐operative and post‐operative radiotherapy and rectal cancer
Authors: Påhlman Lars , Glimelius Bengt
Published: August 2005

The appropriate role for additional radiotherapy in patients with resectable rectal cancer is not yet settled. Irradiation has been considered by surgeons and radiotherapists as superfluous since no effect on survival has been shown. However, numerous trials have demonstrated that perioperative radiotherapy decreases an often high local recurrence rate while others believe it has a definite place in routine management. Several surgeons have, on the contrary, claimed that a skilled surgeon compared to a less skilled surgeon, will get the same acceptably low local recurrence rates. Since we will probably never have a randomized trial comparing “good” and “bad” surgeons, this argument cannot be settled. A further obstacle arises in the difficulty of persuading surgeons to organize their routine work so that it is performed in an optimal way by those specializing in this field. The question also arises whether radiotherapy should be delivered pre‐operatively, postoperatively or as a “sandwich” technique, i.e., both pre‐operatively and postoperatively. According to radio‐biological considerations and results from reported trials, the best effect on local tumor control has been achieved using pre‐operative radiotherapy.
Results of the double stapling procedure in pelvic surgery
Authors: Dean Griffen F. , Knight Charles D. , Knight Charles D.
Published: August 2005

The double stapling technique for rectal reconstruction after resection involves closing the lower rectal segment with a linear stapler and performing the anastomosis using a circular stapler across the linear staple row. The purpose of this report is to review the results of double stapling, present our experience, and draw conclusions from the material available. We have utilized the double stapling technique in 80 patients for primary anastomoses and in 11 patients for secondary anastomoses following Hartmann procedures. Twenty‐one anastomoses were at or near the dentate line. Fifty‐six patients had rectal carcinoma, 29 patients had diverticulitis, 3 patients had carcinoma of the ovary, and 1 patient each had traumatic rectal perforation, volvulus, or rectal prolapse. Complications in the total 91 patients included 3 anastomotic leaks (3.3%), 1 postoperative hemoperitoneum (1.1%), and 3 strictures (3.3%). No anastomosis was protected by diverting colostomy. There were no operative deaths. Of 43 patients with cancer available for follow‐up, 4 patients have developed local recurrence. The technique has been modified for ileoanal anastomosis during abdominal restorative proctocolectomy for ulcerative colitis and familial polyposis and early results are favorable. The double stapling technique provides a safe method for rectal reconstruction at or near the dentate line and offers the following advantages over other stapler techniques: (1) It eliminates the frustrating distal pursestring; (2) The rectal segment is not opened, minimizing contamination; and (3) It avoids gathering the sometimes generous circumference of the rectum on a pursestring thus allowing a more precise distal donut.