bluuebunny/crossref_metadata_2025_split huggingface dataset:
A numerical study of a spectral problem in solid‐fluid type structures
Authors: Conca Carlos , Durán Mario 
Published: August 2005

AbstractThis article presents a numerical study of a spectral problem that models the vibrations of a solid–fluid structure. It is a quadratic eigenvalue problem involving incompressible Stokes equations. In its numerical approximation we use Lagrange finite elements. To approximate the velocity, degree 2 polynomials on triangles are used, and for the pressure, degree 1 polynomials. The numerical results obtained confirm the theory, as they show in particular that the known theoretical bound for the maximum number of nonreal eigenvalues admitted by such a system is optimal. The results also take account of the dependence of vibration frequencies with respect to determined physical parameters, which have a bearing on the model. © 1995 John Wiley & Sons, Inc.
High resolution upwind‐mixed finite element methods for advection‐diffusion equations with variable time‐stepping
Authors: Dawson Clint 
Published: August 2005

AbstractNumerical methods for advection‐diffusion equations are discussed based on approximating advection using a high‐resolution upwind finite difference method, and incorporating diffusion using a mixed finite element method. In this approach, advection is approximated explicitly and diffusion implicitly. We first describe the basic procedure where each advection time‐step is followed by a diffusion step. Because the explicit nature of the advective scheme requires a CFL time‐step constraint, the basic procedure may be expensive, especially if the CFL constraint is severe. Two alternative time‐stepping approaches are presented for improving computational efficiency while preserving accuracy. In the first approach, several advective time‐steps are computed before taking a diffusion step. In the second approach, the advective time‐steps are also allowed to vary spatially. Numerical results for these three procedures for a model problem arising in flow through porous media are given. © 1995 John Wiley & Sons, Inc.
Synthesis, characterization and water absorbency properties of poly(acrylic acid)/sodium humate superabsorbent composite
Authors: Li An , Zhang Junping , Wang Aiqin 
Published: August 2005

AbstractA novel poly(acrylic acid)/sodium humate superabsorbent composite was synthesized by aqueous solution polymerization of acrylic acid using N, N′‐methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator in the presence of sodium humate. The effects on water absorbency such as initial monomer concentration, degree of neutralization of acrylic acid, amount of crosslinker, initiator and sodium humate, etc. were investigated. The water absorbency of the superabsorbent composite synthesized under optimal synthesis conditions with a sodium humate content of 20% exhibited an absorption of 1268 g H2O/g sample and 93 g H2O/g sample in distilled water and in 0.9 wt% NaCl solution, respectively. Swelling rate and water retention tests were also carried out. The results show that sodium humate, as a kind of functional filler, can enhance comprehensive properties of superabsorbent composite and reduce the product cost significantly. Copyright © 2005 John Wiley & Sons, Ltd.
Expression and localization of Reg IV in human neoplastic and non‐neoplastic tissues: Reg IV expression is associated with intestinal and neuroendocrine differentiation in gastric adenocarcinoma
Authors: Oue Naohide , Mitani Yoshitsugu , Aung Phyu Phyu , Sakakura Chouhei , Takeshima Yukio , Kaneko Mayumi , Noguchi Tsuyoshi , Nakayama Hirofumi , Yasui Wataru 
Published: August 2005

AbstractRegenerating islet‐derived family, member 4 (Reg IV) is a candidate marker for cancer and inflammatory bowel disease. In the present study, immunohistochemical analysis of Reg IV was performed in various human neoplastic (n = 289) and non‐neoplastic tissues. In the stomach, foveolar epithelium was negative for Reg IV, whereas goblet cells of intestinal metaplasia and neuroendocrine cells at the base of intestinal metaplasia expressed Reg IV. Neuroendocrine cells of the small intestine and colon showed strong expression of Reg IV, whereas goblet cells of the small intestine and colon showed weak or no expression of Reg IV. Insulin‐producing beta cells of the endocrine pancreas were positive for Reg IV. Among 143 gastric adenocarcinomas, Reg IV expression was detected in 42 (29.4%) and was associated with both the intestinal mucin phenotype and neuroendocrine differentiation. No association was found between Reg IV expression and clinical characteristics such as tumour stage and patient prognosis. Of 36 colorectal adenocarcinomas, 13 (36.1%) were positive for Reg IV, which was associated with tumour stage (p = 0.0379, Fisher's exact test). Expression of Reg IV was detected in 14 (93.3%) of 15 colorectal carcinoid tumours. Reg IV expression was also detected in 5 (21.7%) of 23 ductal adenocarcinomas of the pancreas. In contrast, lung cancers (n = 30) and breast cancers (n = 30) did not express Reg IV. This is the first immunohistochemical analysis of the expression and distribution of Reg IV protein in human tumours. These data suggest that Reg IV is expressed by gastrointestinal and pancreatic tumours, including adenocarcinomas and carcinoid tumours, and that Reg IV is associated with intestinal and neuroendocrine differentiation of the stomach and gastric carcinoma. Copyright © 2005 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Second trimester ultrasound prenasal thickness combined with nasal bone length: a new method of Down syndrome screening
Authors: Maymon Ron , Levinsohn‐Tavor Orna , Cuckle Howard , Tovbin Yosef , Dreazen Eli , Wiener Yifat , Herman Arie 
Published: August 2005

AbstractObjectiveTo evaluate ultrasound prenasal thickness (PT) as a way of enhancing the Down syndrome (DS) screening performance of second‐trimester nasal bone (NB) length measurement.MethodsTwenty‐one DS and 500 normal fetuses were scanned at 14–27 weeks' gestation. The affected karyotype was known to the person performing the scan. Both PT and NB were measured in a mid‐sagittal position and results were expressed in multiples of the normal gestation‐specific median (MoM). Gaussian modelling was used to predict the performance of routine screening.ResultsAmong DS fetuses, the PT median was 1.35 MoM, a highly statistically significant increase compared with the unaffected pregnancies (p < 0.0001, Wilcoxon Rank Sum Test, two‐tailed). The NB median was 0.87 MoM (p < 0.0005) and the ratio PT/NB median was 1.51 MoM (p < 0.0001). In the normal fetuses, the two markers were positively correlated (0.25, p < 0.0001), whereas in the DS fetuses there was a non‐significant negative correlation (−0.24, p = 0.33). For a 5% false‐positive rate, the model predicted detection rate was 70% for PT and NB compared with 43% for NB alone.ConclusionIn the second trimester, PT is increased on average in DS fetuses. Combining PT and NB measurement could yield a higher screening detection rate than NB alone. Confirmation of our findings in a series of women scanned before the karyotype was known is needed before the method can be clinically implemented. Copyright © 2005 John Wiley & Sons, Ltd.
Trisomy 2 due to a 3:1 segregation in an abortion studied by QF‐PCR and CGH
Authors: Lorda‐Sánchez Isabel , Diego‐Alvarez Dan , Ayuso Carmen , de Alba Marta Rodríguez , Trujillo Maria Jose , Ramos Carmen 
Published: August 2005

AbstractBalanced reciprocal translocation is one of the known causes of recurrent spontaneous abortions. Cytogenetic studies of unbalanced miscarriages are difficult due to the growth failure of early loss and usually macerated abortions. We present a molecular study of an abortion in which the father carries a balanced reciprocal translocation t(2;17)(q32.1;q24.3) using QF‐PCR and CGH techniques. DNA analysis showed the presence of a trisomy 2 due to a 3:1 interchange segregation. Recombinant events could also be investigated by comparing DNA samples from the family. We propose QF‐PCR in addition to CGH as an efficient diagnostic method to improve our knowledge of unbalanced offspring in balanced translocation carriers. Copyright © 2005 John Wiley & Sons, Ltd.
Prenatal diagnosis of del(9)(p24): a sex reverse case
Authors: Privitera Orsola , Vessecchia Graziella , Bernasconi Barbara , Bettio Daniela , Stioui Sabine , Giordano Giovanna 
Published: August 2005

AbstractBackgroundWe report on a fetus with sex reversal and del(9)(p24) consequent to a malsegregation of a maternal balanced complex translocation involving chromosomes 7, 9 and 11.MethodsFluorescence in situ hybridization (FISH) was performed in order to verify the presence of the SRY gene and the absence of DMRT1 and DMRT2 genes located in 9p24.3 region and frequently associated with sex reversal.Results and ConclusionsThe prenatal karyotype revealed an unbalanced male fetus. The postmortem examination showed a malformed fetus with female external genitalia. Lack of DMRT1‐2 genes established by FISH. Copyright © 2005 John Wiley & Sons, Ltd.
Pyroelectric and dielectric properties of side‐chain liquid crystal polymers
Authors: Mehl Georg H. , Nordmann Ina , Lacey David , Goodby John W. , Hogg J. H. Christopher , Das‐Gupta Dilip K. 
Published: August 2005

AbstractLiquid crystal side‐chain polymers (LCP), where the polymer architecture consists of a polymer backbone, flexible spacers, and mesogenic groups, are of considerable interest as they promise desirable electro‐active properties, including pyroelectricity and electro‐optic display phenomena. Induced polarization in the LCP system remains stable at ordinary temperatures, and therefore these systems are suitable for sensor materials for pyroelectric applications where switching times are less important. The dielectric applications of the polarized LCP system are also of importance if they are to be used as thin film electro‐active devices. This paper reports the results of the dielectric and pyroelectric characterizations of six different polymers over a wide range of frequencies and temperatures. To elucidate the effect of a variation of chemical structure on the macroscopic properties, the structure of the mesogenic moiety was kept constant, and the length of the spacer and the size of the polymer backbone were varied.
Thermodynamic characterization of interpenetrating polymer networks
Authors: Privalko Valery P. , Azarenkov Vassily P. , Baibak Alexander V. , Korskanov Valery V. , Titov Georgy V. , Frisch Harry L. , Zhou Peiguang 
Published: August 2005

AbstractCrosslinked poly(methyl methacrylate) (PMMA‐c), poly(carbonate‐urethane) (PCU‐c), poly(vinyl pyridine) (PVP‐c), and full, simultaneous interpenetrating polymer networks (IPNs) based on the above polymers were characterized by precise heat capacity (Cp) measurements in the temperature interval 4.2–450 K. The raw values of Cp scaled with temperature (T) as Cp ∼ Td with d = 2 and 5/3, as expected for a fracton‐like vibration regime, in the temperature intervals 8–10 and 10–30 K, respectively. A single glass transition temperature (Tg) and two Tg's were observed for apparently homogeneous and microphase‐separated IPNs, respectively. Judged by the positive sign of the excess Gibbs free energy, the apparently single‐phase state of homogeneous IPNs is thermodynamically unstable; however, its kinetic stability is ensured by permanent topological constraints (network junctions) prohibiting the incipient phase separation.
Complex dielectric permittivity of an ion‐containing polymer in the microwave region
Authors: Dabek Roman 
Published: August 2005

AbstractA method for determination of the complex dielectric permittivity of polar, non‐polar and ion‐containing polymers at microwave frequencies is presented. Disk‐shaped samples are employed in a radial‐line configuration at the end of a coaxial‐line structure. An equivalent circuit, established by admittance measurements, is used to relate the capacitance at the sample face to the impedance measured on the slotted line preceding the coaxial sample holder. The method has been applied first to determine the frequency spectrum of polyethylene (PE) and poly(tetrafluoroethylene) (PTFE) between 80 MHz and 4 GHz at 293 K. The results agree with those reported in the literature, demonstrating the reliability of the method as well as usability of PE and PTFE as standards at high frequencies. Subsequently, the AMF C‐311 cation exchange membrane (polyfluorocarbon backbone chains with grafted polystyrene side chains containing sulfonate groups) was studied in the same frequency range. Values of dielectric permittivity and dielectric losses for AMF C‐311 samples in the dry and swollen hydrated states are reported and compared.
Dielectric spectroscopy of polyethylene in the frequency range of 10−5 Hz to 106 Hz
Authors: Scarpa P. C. N. , Svatík A. , Das‐Gupta D. K. 
Published: August 2005

AbstractPolyethylene, one of the most widely used electrical insulating materials, is known, despite its excellent physical properties, to exhibit structural degradation when submitted to a continued electrical (AC) stress in a humid environment. Although much work has been done to correlate the inception and growth of water trees with the breakdown in polyethylene, little attention appears to have been given to identify, through an appropriate model, the deterioration of the electrical and dielectrical parameters with the progressive aging of the insulator. This paper reports the results of a comprehensive study of electrical aging of both low‐density polyethylene (LDPE) and chemically crosslinked polyethylene (XLPE) aged in humid environment at an AC stress of 6 kV/mm for an extended time. For this study, dielectric spectroscopy in the frequency range of 10−5 Hz to 106 Hz has been employed to provide appropriate electrical analog models of the aging. An agreement, at least qualitative, is found with the dielectric and the thermally stimulated discharge current (TSDC) behavior.
Synthesis and characterization of new poly(butadiene‐co‐acrylic acid(g) acrylic acid) and poly(butadiene(g) acrylic acid)
Authors: Bertorello Héctor , Argüello Ricardo 
Published: August 2005

AbstractSynthetic crosslinked polymers from oligomers of butadiene‐co‐acrylic acid (Mw 5000) or oligomers of butadiene (Mw 6000) and acrylic acids were obtained after grafting reactions using varying reactant ratios. Characterization of the new crosslinked polymers were carried out by use of FTIR, H‐NMR, and 13C‐NMR in the solid state and also with the swollen products in D2O, DMF D7, or DMSO D6. Determinations of swelling in distilled water for the different synthesized hydrogels showed increase in the V/Vo ratios as the concentrations of anions (carboxylate) became higher. These values were sensitive to different pH values and changes in the concentrations of electrolytes. Different behavior was observed for the polymers obtained from mass and from synthesis in benzene. SEM analysis of the surfaces of the polymers obtained in mass showed a fibrous structure (with lower contents of carboxylic groups, and more swellable and with greater capacity to retain albumin). A porous surface was observed for products obtained in benzene (with higher content of carboxyl groups and capacity to retain cations such as copper and malachite green).
Nonisothermal thermophysical evaluation of a polypropylene + ethylene propylene diene (EPDM) blend
Authors: Brostow Witold , D'Souza Nandika Anne , Galina Henryk , Ramamurthy A. C. 
Published: August 2005

AbstractRecent theoretical evidence indicates that the rate effects of quenching seen in the isothermal crystallization kinetics can be eliminated through use of a nonisothermal method based on constant rate heating and cooling through inclusion of an activation energy. To investigate the potential of this method for polymers, we apply it to semicrystalline polymers: polypropylene (PP), a binary blend PP + ethylene propylene diene rubber (EPDM) and a ternary system PP + EPDM + high‐density polyethylene (PE). As opposed to traditional rubber‐modified systems such as high‐impact polystyrene (HIPS) wherein an amorphous component is blended with a rubbery one, the PP + EPDM system has a semicrystalline component. From the perspective of crystal lamellae growth or stress induced slip, the thermophysical properties are also a concern. Therefore, we use differential scanning calorimetry (DSC) and thermomechanical analysis (TMA). The results indicate that differences between isothermal and nonisothermal conditions must be taken into account since the latter conditions prevail in extrusion, injection molding, and in hot coating‐slow cooling processes. Our nonisothermal analysis of crystallization should assist in the optimization of cooling of semicrystalline polymers.
Rheology and morphology of poly(vinyl acetate) + calcite films
Authors: Kovacevic Vera , Lucic Sanja , Hace Drago , Glasnovic Antun 
Published: August 2005

AbstractWe have studied mechanical and rheological behavior of poly(vinyl acetate) (PVAC) composites filled with calcite as a function of filler particle geometry, particle size distribution, and active surface area. Detailed morphological characteristic were investigated. Tensile properties of PVAC composites were evaluated in the composition range 5–20 wt% calcite. The elongation at break decreases as consequence of matrix mobility restriction by filer particles. By contrast, the strength at break increases as a result of fewer stress concentration points produced by small calcite particles. Large calcite particles decrease the strength of the PVAC composite because of lack of structural continuity. Failure is then dominated by the dewetting. Understanding the deformation as it relates to structure, mechanism of failure, and strength of interactions makes development of improved PVAC composites for adhesives possible.
Conformational analysis and DFT calculations of 8α‐hydroxy‐germacradiene‐6,12‐olide derivatives
Authors: Maggio Antonella M. , Barone Giampaolo , Bruno Maurizio , Duca Dario , Rosselli Sergio 
Published: August 2005

AbstractThe Systematic Conformational Search Analysis (SCSA) code was employed to study the conformational properties of the 8α‐hydroxy‐germacradiene‐6,12‐olide isomers. This procedure was extended to the trans,cis‐ and trans,trans‐1(10),4‐isomers of 8α,15‐dihydroxy‐germacradiene‐6,12‐olides and 8α‐hydroxy‐15‐oxo‐germacradiene‐6,12‐olides, to investigate structural and energetic analogies between these and the 8α‐hydroxy‐germacradiene‐6,12‐olide species. The calculated 13C NMR spectra, at the hybrid DFT mPW1PW91 level, showed a sound correlation with the corresponding experimental spectra, providing a valid support to the reliability of the calculated structures and to the consistence of our conformational analysis. The results presented here allowed us to support our previous mechanistic interpretation on the oxidation of 8α,15‐dihydroxy‐trans,trans‐1(10),4‐germacradiene‐6,12‐olides to 8α‐hydroxy‐15‐oxo‐trans,cis‐1(10),4‐germacradiene‐6,12‐olides. Copyright © 2005 John Wiley & Sons, Ltd.
Chemical bonding in zwitterionic diamino‐meta‐quinonoids and their isomers
Authors: Höltzl Tibor , Veszprémi Tamás , Nguyen Minh Tho 
Published: August 2005

AbstractQuantum chemical calculations using molecular orbital (HF) and density functional (B3LYP) methods, in conjunction with the 6‐311 + + G(d,p) basis set, have been applied to investigate the electronic structure of a series of diamino‐meta‐quinonoid molecules, each containing a six‐membered ring coupled with two exocyclic CO bonds situated in ametaposition, along with two amino substituents (NH2and NHR). The chemical bonding phenomena in these zwitterions and isomers where one or two hydrogens are transferred from N to O are analyzed with the aid of the atoms‐in‐molecules (AIM) approach. The relative energies between zwitterionic and quinonoid isomers in both neutral and ionized states also have been evaluated. Substituents exert a strong effect that in many cases changes the energy ordering. Copyright © 2005 John Wiley & Sons, Ltd.
Nonlinear elasticity of rodlike macromolecules in condensed state
Authors: Doi Masao , Kuzuu Nobu Y. 
Published: August 2005

AbstractThe finite deformation elasticity of gels of stiff rodlike polymer chains is discussed theoretically. Unlike a rubber composed of flexible polymer chains, the elasticity of this system is energetic, and arises from the elastic deformation of the stiff chains which are forced to bend under macroscopic strain. The stress‐strain curve of this system is shown to be nonlinear even if the bending of the rods is small, and has a characteristic S‐shaped form which is unlike that of a rubber. The effect of orientational order is also discussed.
Interpretation of longitudinal‐acoustical‐mode spectra of polymers
Authors: Snyder Robert G. , Scherer James R. 
Published: August 2005

AbstractThe influence of temperature, frequency, and straight‐chain‐length distribution on the low‐frequency Raman‐active longitudinal‐acoustical‐mode (LAM) bands of polymers is discussed. Specifically, the effect of these factors on the intensity of LAM‐1, on the ratio of intensities of LAM‐1 to LAM‐k, and on peak position is computed or estimated. Band halfwidth and chain‐length‐distribution halfwidth are found not to be simply related. It is shown that the integrated intensity of LAM‐1 is very nearly proportional to the total length of straight chains.
Tensile properties and partial alignment of polyacetylene, (CH)x, films
Authors: Druy M. A. , Tsang C.‐H. , Brown N. , Heeger A. J. , Macdiarmid A. G. 
Published: August 2005

AbstractThe tensile properties of both cis‐ and trans‐polyacetylene, (CH)x, were investigated in order to determine the variables that influence that ultimate extension ratio (l/l0) of polyacetylene films. It was found that when cis‐films of polyacetylene were extended in an inert (argon) atmosphere, ultimate extension ratios as high as 3.3 were obtained and with subsequent isomerization at 160–200°C under stress, a final l/l0, of about 4 was obtained. The extension ratio is extremely sensitive to exposure to oxygen and decreases markedly after periods as short as 1 min. It appears as though crosslinking may occur in the polymer when it is exposed to air and this produces brittleness in the specimen. When (CH)x was isomerized from cis to trans, it became brittle, even in the absence of air.
Plastic deformation of polypropylene: Effect of molecular weight on drawing behavior and structural characteristics of ultra‐high‐modulus products
Authors: Wills A. J. , Capaccio G. , Ward I. M. 
Published: August 2005

AbstractThe influence of molecular weight and temperature on the tensile drawing behavior of polypropylene has been studied, with particular reference to the production of ultra‐high‐modulus oriented materials. It has been shown that the optimum draw temperature is molecular weight independent to a good approximation, and that high‐modulus products can be obtained for M̄w in the range 180,000–400,000, the highest modulus being achieved for polymer with M̄w = 181,000. As in the case of linear polyethylene, under optimum drawing conditions the Young's modulus relates only to the draw ratio. Low‐temperature moduli as high as 25–27 GPa were recorded, which compare favorably with a previously reported value of 42 GPa for the crystal‐lattice modulus. Although the drawing behaviour of the samples studied appeared comparatively insensitive to molecular weight, some of the properties of the draw materials, notably melting point and shrinkage at high temperature, showed a wide range of behavior.