bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure, phase transitions and dielectric properties of a new inclusion compound of bis-thiourea pyridinium nitrate salt
Authors: Maluszýnska Hanna , Czarnecki Piotr 
Published: February 2006

Abstract
A structure of a new inclusion compound of bis-thiourea pyridinium nitrate salt C5H6N+NO3
- 2[CH4N2S] was determined by single-crystal X-ray diffraction method at 293 K, 250 K and 150 K. In high temperature phase the compound crystallizes in orthorhombic system, the two low-temperature phases are monoclinic. The sequence of phases is: Pbnm → P21/c → P21. In the orthorhombic form (I) the a axis is doubled in respect to the monoclinic forms and pyridinium and nitrate ions are partially disordered. Both low-temperature monoclinic phases (II) and (III) are ordered but twinned by pseudo-merohedry. In all three phases the host lattice is built of ribbons of hydrogen-bonded thiourea molecules and nitrate anions forming channels in which the guests pyridinium cations are located. Each ribbon consists of two crystallographically independent thiourea molecules and nitrate ions. Four ribbons form a channel parallel to the c axis with approximately square cross-section. In the channel there is a stack of pyridinium cations, which planes form an inclination angle with the channel axis. The angle varies from about 90° in disordered phase I to 60° in well ordered phase (III).
The dielectric spectroscopy measurements were performed on the polycrystalline sample with HP-4291A impedance analyser in the frequency range 1 MHz–1 GHz. The dielectric measurements reveal that two phase transitions occur at T
1 = 287 K and at T
2 = 217 K. The phase transition at T
2 = 287 K is of the first order with the thermal hysteresis of 10 K at cooling and heating. The phase transition at 217 K is of the second order and the dielectric anomaly suggests the ferroelectric-paraelectric phase transition. The dielectric relaxation observed below T
2 are caused by the pyridinium cation reorientation. The dielectric relaxation time changes with the temperature according to Arrhenius low and the activation energy of the relaxation process is about 14 kJ/mol.
Self-association and stereochemistry study of (5R)-4-methyl-5-phenyl-1,3,4-oxadiazinan-2-one
Authors: Rodrigues Alessandro , Olivato Paulo R. , Zukerman-Schpector Julio , Rittner Roberto 
Published: February 2006

Abstract
C10H12N2O2, M
r = 191.21, P21, a = 5.5771(7), b = 27.841(3), c = 6.906(1) Å, β = 111.937(9)°, Z = 4, R
1 = 0.0462. The two independent molecules in the asymmetric unit are linked through two very strong quasi centro-symmetric hydrogen bonds. The oxadiazinone rings, of both molecules, show the pyramidal inversion at N-4 nitrogen, thus resulting in a C(R)N(S)—C(R)N(R) diastereomeric pair. The analysis of the IR N-H stretching band (in the solid and in carbon tetrachloride solution) and the 13C NMR experiment at low temperature are in agreement with the X-ray crystal structure.
Testing Causal Mechanisms of Nonsyndromic Craniosynostosis Using Path Analysis of Cranial Contents in Rabbits with Uncorrected Craniosynostosis
Authors: Fellows-Mayle Wendy , Hitchens T. Kevin , Simplaceanu Elena , Horner Joyce , Barbano Timothy , Losee Joseph E. , Losken H. Wolfgang , Siegel Michael I. , Mooney Mark P. 
Published: February 2006

Objective: Various causal mechanisms of familial nonsyndromic craniosynostosis have been presented. One hypothesis suggests that overproduction of bone at the suture is the primary origin of craniosynostosis, which affects brain and cranial growth secondarily through altered intracranial pressure (Primary Suture Fusion Model). Other hypotheses suggest that decreased cranial base growth or abnormal brain growth are the primary cause of craniosynostosis (Cranial Base, Brain Parenchyma Models, respectively). This study was designed to investigate which model best describes neurocranial changes associated with craniosynostosis in a rabbit model through multivariate path analysis. Design: Serial magnetic resonance imaging scans and intracranial pressure measurements were obtained at 10, 25, and 42 days of age from 18 rabbits: six controls, six with delayed-onset synostosis, and six with early-onset synostosis. Five variables were collected from each rabbit: calvarial thickness at the affected suture, cranial base length, brain volume, cerebrospinal fluid volume, and intracranial pressure. This data set was used to test causal pathway relationships generated by the proposed models. Goodness of fit was measured by experimental group for each model. Results: Primary Suture Fusion Model best explained the variables in both delayed-onset and early-onset synostotic rabbits (Goodness of fit = 93%, 97%, respectively). Cranial Base Model (Goodness of fit = 94%) best explained the data in control rabbits. Conclusion: Results suggest that the primary site of craniosynostosis in craniosynostotic rabbits is most likely the synostosed suture. Other cranial vault anomalies are most likely secondary compensatory changes. Results of the present study may provide insight regarding the causal pathway of craniosynostosis.
SEPN1: Associated with congenital fiber‐type disproportion and insulin resistance
Authors: Clarke Nigel F. , Kidson Warren , Quijano‐Roy Susana , Estournet Brigitte , Ferreiro Ana , Guicheney Pascale , Manson James I. , Kornberg Andrew J. , Shield Lloyd K. , North Kathryn N. 
Published: February 2006

AbstractObjective Our first objective was to determine whether SEPN1 gene mutations are a cause of congenital fiber‐type disproportion (CFTD), a rare form of congenital myopathy in which relative hypotrophy of type 1 (slow twitch) muscle fibers is the principal abnormality on histology. Second, we investigated an association between SEPN1‐related myopathy and insulin resistance.MethodsWe sequenced SEPN1 in five unrelated CFTD patients with scoliosis and respiratory muscle weakness and screened an additional 22 CFTD patients for abnormalities in SEPN1 by Western blotting and restriction digest for the 943G→A mutation. We performed oral glucose tolerance tests (OGTTs) in eight SEPN1‐related myopathy patients. ResultsTwo sisters with CFTD were homozygous for the 943G→A SEPN1 mutation and had clinical features typical of previously reported patients with SEPN1‐related myopathy. Five of eight SEPN1‐related myopathy patients had abnormalities on OGTT suggestive of insulin resistance.InterpretationSEPN1 is the second genetic cause of CFTD and the first cause of autosomal recessive CFTD to be identified to our knowledge. CFTD is the fourth clinicopathological presentation that can be associated with mutations in SEPN1. Insulin resistance may be a specific, previously unrecognized aspect of SEPN1‐related myopathy. Ann Neurol 2006
High temperature polymerization of propylene catalyzed by MgCl2‐supported Ziegler–Natta catalyst with various cocatalysts
Authors: Wang Qi , Lin Yuanzhi , Zhang Zhenhua , Liu Boping , Terano Minoru 
Published: February 2006

AbstractFour cocatalysts, referred to as ethylaluminoxanes, were synthesized by the reaction between triethylaluminium (AIEt3) and water under various molar ratios of H2O/Al at −78°C. Aluminoxanes were used as cocatalysts for a MgCl2‐supported Ziegler–Natta catalyst for propylene polymerization at temperatures ranging from 70 to 100°C. When the polymerization was activated by AlEt3, the activity as well as the molecular weight and isotacticity of the resulting polymer gradually dropped as the temperature varied from 70 to 100°C. When ethylaluminoxane was employed as the cocatalyst, good activity and high molecular weight and isotacticity were obtained at 100°C. Furthermore, when the cocatalyst varied from AlEt3 to ethylaluminoxane, the atactic fraction and polymer fraction with moderate isotacticity decreased and the high isotactic fraction slightly increased, which indicated that the variation of the cocatalyst significantly affects the isospecificity of active sites. It was suggested that the reactivity of the Al‐Et group and the size of the cocatalyst were correlated to the performance of the Ziegler–Natta catalyst at different temperatures. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1978–1982, 2006
Prediction of properties of rubber by using artificial neural networks
Authors: Vijayabaskar V. , Gupta Rakesh , Chakrabarti P. P. , Bhowmick Anil K. 
Published: February 2006

AbstractDifferent rubber formulations were designed using nitrile rubber and a mixed crosslinking system consisting of sulfur/accelerator and electron beam radiation. Based on the experimental results, an artificial neural network (ANN) was constructed to simulate the mechanical properties and volume fraction of rubber. The ANN could predict accurately the above properties for a series of nitrile rubber compounds. However, the number of training data played a key role in the ANN predictive quality. In addition, the more complex the nonlinear relation between input and output was, the larger was the number of training dataset required. The predicted results were further validated using another mathematical model. The constructed ANN was verified with a completely different styrene butadiene rubber system. The prediction was found to be extremely good. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2227–2237, 2006
Effect of reaction parameters on the particle sizes of crosslinked spherical phenolic beads by suspension polymerization of phenol and formaldehyde
Authors: Singh Arjun , Lal Darshan 
Published: February 2006

AbstractThe crosslinked spherical phenolic beads (PB) were prepared with phenol and formaldehyde in alkaline medium by suspension polymerization technique. Poly(vinyl alcohol) (PVA) hexamethylenetetramine (HMTA), and triethylamine (TEA) were used as stabilizer, crosslinking agent, and basic catalyst respectively. The resulting PB with higher yield (82.5%) and relatively uniform particle size range (0.2–1.8 mm) were formed at 95–97°C, 550 rpm for 4 h, by using varied amounts of PVA as a stabilizer. The particle size and its distribution could be adjusted by selecting a suitable polymerization medium, consisting of monomer added to water, and by varying their relative amounts, mechanical agitation and stabilizer concentration. The yield % of PB was also varied with the concentration of stabilizer, agitation rate, and monomer‐to‐water ratio. The effects of concentration of the stabilizer, agitation rates, and monomer‐to‐water ratio on PB formation and morphology are described. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2323–2330, 2006
Two‐dimensional simulation of hollow fiber membrane fabricated by phase inversion method
Authors: Yang Xiao‐Tian , Xu Zhen‐Liang , Wei Yong‐Ming 
Published: February 2006

AbstractIn the steady fabricating process, two‐dimensional hollow fiber membrane near the spinneret was numerically simulated using the finite element method (FEM). The unknown positions of free surface and moving interface were calculated simultaneously by the velocity and pressure fields. The effects of seven relevant parameters, i.e., inertia term, gravity term, dope flow rate, bore flow rate, dope viscosity, tensile force, end velocity and non‐Newtonian on the velocity and diameter profile were studied. On the basis of the simulated results, the inertia term in hollow fiber‐spinning process was safely neglected in low speed, while the effect of gravity was not be neglected. Besides, the outer diameter of the fibers increased with an increase of dope flow rate and bore flow rate; Large tensile force or large end velocity could cause large deformation in the air gap; larger viscous dope solution tended to make less deformation in the air gap. It was found that an increase of the dope flow rate at small dope flow rate resulted in an increase of the inner diameter, while at large dope flow rate, it decreased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2067–2074, 2006
Viscoelastic behavior of thermosetting epoxy mixtures modified with syndiotactic polystyrene during network formation
Authors: Tercjak A. , Serrano E. , Remiro P. M. , Mondragon I. 
Published: February 2006

AbstractThe rheological behavior of thermosetting epoxy mixtures modified with thermoplastic syndiotactic polystyrene (sPS) was monitored during the curing of the epoxy resin. The selected thermosetting system was diglycidyl ether of bisphenol A cured with 4,4′‐methylene bis(3‐chloro‐2,6‐diethylaniline) in the presence of various compositions of sPS (from 2.5 to 12.5 wt %). The storage and loss shear moduli of the systems were monitored during network formation. The validity of the Winter–Chambon criterion for the accurate determination at the gelation point from rheological data was demonstrated. The influence of the sPS concentration on the dynamic rheological properties of the samples was investigated. The experimental data showed that at sPS concentrations lower than 7.5 wt %, phase separation induced a quick increase in the viscosity, which was related to a crystallization‐induced phase separation of sPS. For sPS concentrations higher than 7.5 wt %, near the phase‐inversion composition, the rheological behavior of the mixtures was characteristic of a cocontinuous structure. After the viscosity jumped at the onset of phase separation, a decrease in the viscosity was found, and later on, the viscosity increased again because of gelation. Additionally, the influence of the cure temperature on the rheological properties was studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2348–2355, 2006
Poly (N‐methylaniline)/multi‐walled carbon nanotube composites—Synthesis, characterization, and electrical properties
Authors: Lu Xiaofeng , Zheng Jiani , Chao Danming , Chen Jingyu , Zhang Wanjin , Wei Yen 
Published: February 2006

AbstractThis study described the synthesis of hydrochloric acid (HCl)‐doped poly (N‐methylaniline) (PNMA) with carboxylic groups containing multi‐walled carbon nanotubes (c‐MWNTs) via in situ polymerization. Based on the π–π electron interaction between c‐MWNTs and the N‐methylaniline monomer and the hydrogen bond interaction between the carboxyl groups of c‐MWNTs and imine groups of N‐methylaniline monomers, N‐methylaniline molecules were adsorbed on the surface of c‐MWNTs and polymerized to form PNMA/c‐MWNT composites. Scanning electron microscopy images showed that both the thinner fibrous phase and the larger block phase could be observed. The individual fibrous phases had diameters from several tens to hundreds of nanometers, depending on the PNMA content. Transmission electron microscopy proved that PNMA/c‐MWNTs composite fibrous phases were core (c‐MWNT)‐shell (PNMA) tubular structures. The structure of PNMA/c‐MWNT composites was characterized by FTIR, UV–vis spectra, and X‐ray diffraction patterns. The electrical conductivities of PNMA/c‐MWNT composites were much higher than that of PNMA without c‐MWNTs. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2356–2361, 2006
Preparation of polystyrene/poly(vinyl acetate) nanocomposites with a core–shell structure via emulsifier‐free emulsion polymerization
Authors: Soltan‐Dehghan Morteza , Sharifi‐Sanjani Naser , Naderi Nader 
Published: February 2006

AbstractPolystyrene/poly(vinyl acetate) latex nanoparticles with a core–shell morphology in an emulsifier‐free emulsion polymerization system were prepared with purified styrene and vinyl acetate (VAc) as monomers and 2,2′‐azo bis(2‐amino propane) dihydrochloride (ABA,2HCl) as the initiator and emulsifier. The optimized conditions of polymerization of VAc, on top of the already‐formed polystyrene as a core polymer, with a core–shell morphology were obtained using various parameters such as volume ratio of the first and second stages, type of process, and reaction time. The morphologic structure of the nanoparticles was studied by scanning electron microscopy and transmission electron microscopy. The latex nanoparticles and polymers were characterized by differential scanning calorimetry. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2409–2414, 2006
Gas permeation resistance of a perfluoroalkoxy‐tetrafluoroethylene copolymer
Authors: Extrand C. W. , Monson L. 
Published: February 2006

AbstractThe permeation resistance of perfluoroalkoxy (PFA), a polytetrafluoroethylene (PTFE) copolymer, to various gases was explored. The diffusion and permeability coefficients for hydrogen, oxygen, nitrogen, and air were measured with extruded films using standard manometric techniques. For thicker films, transport properties were independent of film thickness. For the thinnest films, the diffusivity and permeability coefficients were slightly higher because of reduced crystallinity. The solubility of these apolar permeants in PFA was quite low and behaved ideally. Therefore, the permeation characteristics of air could be calculated from those of nitrogen and oxygen. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2122–2125, 2006
Study of sulfonic acid esters from 1→4‐, 1→3‐, and 1→6‐linked polysaccharides
Authors: Koschella Andreas , Leermann Timo , Brackhagen Meinolf , Heinze Thomas 
Published: February 2006

AbstractSulfonic acid esters of differently linked polysaccharides including cellulose, dextran, lichenan, and pullulan were synthesized homogeneously applying N,N‐dimethylacetamide/LiCl as the solvent. The dependence of the degree of substitution (DS) on the molar ratio of repeating unit to sulfonic acid chloride and on the structure of the reagent (benzene‐, p‐toluene‐, 4‐chlorobenzene‐, 2,4‐dinitrobenzene‐, 2,4,6‐trimethylbenzene‐, and 2,4,6‐triisopropylbenzene sulfonic acid chloride), as well as on the polysaccharide, was studied. DS values in the range of 0.2–2.3 were obtained. Bulky and electron withdrawing substituents on the aromatic ring inhibited ester formation. None of the sulfonic acid chlorides applied showed distinct regioselectivity. The polysaccharide sulfonic acid esters were soluble in organic solvents depending on the type of substituent and the degree of substitution. The molecular structure of the new polymers was confirmed by elemental analysis, FTIR, and 13C‐NMR spectroscopy. Subsequently, nucleophilic displacement reactions were carried out, which showed that the reactivity of the primary sulfonic acid ester group was higher than that of the secondary ones. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2142–2150, 2006
A water‐soluble acrylate/sulfonate copolymer. I. Its synthesis and dispersing ability on cement
Authors: Ye Yi‐Shian , Huang Hung‐Lung , Hsu Kung‐Chung 
Published: February 2006

AbstractA new water‐soluble methacrylate/2‐acrylamido‐2‐methylpropane sulfonate copolymer (PMAMP) was synthesized and evaluated as a dispersion agent for cement particles. PMAMP was prepared from methacrylic acid and 2‐acrylamido‐2‐methylpropane sulfonic acid (AMP). The structure of the prepared polymer was verified by its NMR and IR spectra. The dispersing properties of PMAMP were evaluated by a minislump test on cement pastes. The test results indicated that this copolymer could disperse the cement particles and improve the minislump of cement pastes. Compared with a commercial superplasticizer (sulfonated naphthalene formaldehyde condensates), PMAMP performed better in enhancing the fluidity of the cement pastes. The polymer with about 40–50% AMP and a weight‐average molecular weight of about 5 × 104 was most effective in dispersing cement particles and promoting the fluidity of cement pastes. Nevertheless, PMAMP with a higher AMP content or a higher molecular weight appeared to cause less slump loss. This was related to the interaction of this admixture with the cement particles and its adsorption behavior onto the cement particles. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2490–2496, 2006
Synthesis and characterization of soluble hybrids of poly(vinyl pyrrolidone) or its copolymer
Authors: Huang K. S. , Lee E. C. , Chang Y. S. 
Published: February 2006

AbstractThe purpose of this study was to examine the properties and synthesis feasibility of water‐soluble hybrids of poly(vinyl pyrrolidone) (PVP) or a PVP copolymer. PVP was first mixed with different concentrations of tetraethoxysilane (TEOS) to produce PVP/SiO2 hybrids. Second, PVP/sodium polyacrylate (PAANa) copolymers were prepared and further developed into hybrids and then were analyzed and tested with methods such as Fourier transform infrared, NMR, X‐ray spectroscopy, and scanning electron microscopy. According to the results of the experiments, the PVP polymer or its copolymer generated hydrogen bonding with the OH group in SiO2 with both PVP/SiO2 and PVP–PAANa/SiO2 hybrids. With an adequate concentration of TEOS, the hybrids exhibited increased heat resistance. Moreover, the roughness and holes in the hybrids increased with increasing TEOS concentration. However, when the TEOS concentration exceeded 6%, the roughness began to drop. Finally, all the hybrids were water‐soluble but possessed inferior solubility when used with organic solvents. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2164–2170, 2006
Hydrosilylation reaction of methylhydridesiloxane to phenylacetylene
Authors: Mukbaniani O. , Tatrishvili T. , Titvinidze G. , Mukbaniani N. , Lezhava L. , Gogesashvili N. 
Published: February 2006

AbstractThe hydrosilylation reaction of α,ω‐bis(trimethylsiloxy)methylhydridesiloxane to phenylacetylene in the presence of catalyst—platinum hydrochloric acid (0.1M solution in tetrahydrofuran)—at 1 : 35 ratio of initial compounds, at various temperatures (40–60°C) was investigated and methylsiloxane oligomers with phenethenyl substituted groups in the side chain has been obtained. It was shown that complete hydrosilylation of all active (SiH groups do not take place. The hydrosilylation reaction order, activation energy, and rate constants were found. The synthesized oligomers were characterized by 1H and 13C NMR and IR spectral data. Gel‐permeation chromatographic, differential scanning calorimetric, thermogravimetric, and wide‐angle X‐ray investigations of synthesized oligomers were carried out. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2511–2515, 2006
The effect of the osmolyte trimethylamine N‐oxide on the stability of the prion protein at low pH
Authors: Granata Vincenzo , Palladino Pasquale , Tizzano Barbara , Negro Alessandro , Berisio Rita , Zagari Adriana 
Published: February 2006

AbstractA study of the effect of trimethylamine N‐oxide on the stability of two recombinant forms of the prion protein PrP, an ovine full‐length and a human truncated form, is here reported. Both thermal denaturation and denaturation at room temperature were analyzed at pH values above and below the pKa of trimethylamine N‐oxide, which is close to 4.7. Surprisingly, results showed that not only is trimethylamine N‐oxide able to decrease PrP thermal stability at low pH but it also acts as a strong denaturant at room temperature. Likely, this destabilization is due to the capability of the cationic form of trimethylamine N‐oxide to interact with the protein backbone as well as to weaken electrostatic interactions which are important for PrP fold. These results constitute the first experimental measurement of the effect of trimethylamine N‐oxide on PrP stability and provide an unambiguous proof of the destabilizing effect of this osmolyte on PrP at low pH. © 2006 Wiley Periodicals, Inc. Biopolymers 82: 234–240, 2006This 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