bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation into the morphology and mechanical properties of melt‐drawn filaments from uncompatibilized blends of polystyrene and high‐density polyethylene
Authors: Cherian Zeena , Lehman Richard , VanNess Kenneth
Published: November 2006

Uncompatibilized immiscible blends of polystyrene (PS) and high‐density polyethylene (HDPE) were melt‐processed in a single‐screw extruder fitted with a fine screen mesh and capillary die and were further drawn into filaments to produce near‐nanoscale immiscible domains. The resultant morphologies and mechanical properties were studied for these structures in which load transfer is achieved solely by mechanical linkages between blend domains. The morphology of the blends revealed co‐continuity approximately in the range of 45–47 volume percent PS. The development of a three‐dimensional co‐continuous network in 45 vol% PS, as revealed by morphology observations, was also related to a decrease in extruder output rate in this region, an indicator of the melt interaction of the two phases as co‐continuity is achieved. Image analysis revealed submicron fibrillar structures near the phase inversion composition where domain sizes ranged from 6–220 nm with an average domain size of 90 nm. Tensile modulus increased with increasing PS content (E = 2.7 GPa at 47% PS) over the entire blend range with values greater than the rule of mixtures up to 50% PS. Strain to failure did not seem to be influenced by co‐continuous morphologies and the fine dispersion of PS domains appears to constrain the fundamentally high strain of HDPE. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1616–1625, 2007
Modeling solubility of gases in semicrystalline polyethylene
Authors: Yao Wenjuan , Hu Xiaoping , Yang Yongrong
Published: November 2006

An absorption model of gases in semicrystalline polymer was built that was based on the activity coefficient theory in polymer solution and associated with crystallinity dependent on temperature. The solubility of ethylene, isopentane, and n‐hexane in three types of polyethylene (PE) were obtained by the use of a pressure‐decay method at temperatures of 333–363 K and pressures of up to 2 MPa, 80–300 KPa, and 19–100 KPa, respectively. Experimental data from three gases in each PE sample were used for the single‐parameter fitting, and fitting error was within about 12%. It was found that a single parameter was merely dependent on the properties of PE used. It was shown that, unlike with the Flory–Huggins model and the UNIFAC–M‐H method, correlation between the crystallinity of the semicrystalline polymer and temperature had to be taken into account in order for the solubility data of alkane, olefin, and aromatic hydrocarbons in polyethylene to fit well, especially in the temperature range near the melting point of the polymer. The four free‐energy contributions to the total gas activity were experimentally determined to be about 47%–60% combined, the free‐volume contribution about 12%–25%, and the elastic effect about 22%–35%, but the interactional contribution was zero. The contributions changed with the size of the gas molecules. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1737–1744, 2007
Mechanical properties of short‐isora‐fiber‐reinforced natural rubber composites: Effects of fiber length, orientation, and loading; alkali treatment; and bonding agent
Authors: Mathew Lovely , Joseph Rani
Published: November 2006

A series of short‐isora‐fiber‐reinforced natural rubber composites were prepared by the incorporation of fibers of different lengths (6, 10, and 14 mm) at 15 phr loading and at different concentrations (10, 20, 30, and 40 phr) with a 10 mm fiber length. Mixes were also prepared with 10 mm long fibers treated with a 5% NaOH solution. The vulcanization parameters, processability, and stress–strain properties of these composites were analyzed. Properties such as tensile strength, tear strength, and tensile modulus were found to be at maximum for composites containing longitudinally oriented fibers 10 mm in length. Mixes containing fiber loadings of 30 phr with bonding agent (resorcinol‐formaldehyde [RF] resin) showed mechanical properties superior to all other composites. Scanning electron microscopy (SEM) studies were carried out to investigate the fiber surface morphology, fiber pullout, and fiber–rubber interface. SEM studies showed that the bonding between the fiber and rubber was improved with treated fibers and with the use of bonding agent. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1640–1650, 2007
Study of an epoxy system cured with different diamines by differential scanning calorimetry
Authors: Ramírez C. , Rico M. , López J. , Montero B. , Montes R.
Published: November 2006

Kinetic and cured reaction experiments for five systems based on the epoxy resin diglycidyl ether of bisphenol A (DGEBA) cured with the diamines 1,3‐bisaminomethylcyclohexane, 4‐4′‐diaminediphenylmetane, 1,4‐phenylediamine, 4‐4′(1,3‐phenylenediisopropylidene) bisaniline, and 4‐4′metilenebis(2,6‐dietilaniline) were carried out by differential scanning calorimetry. Kinetic analysis was performed using dynamic experiments through the Kissinger and Flynn–Wall–Ozawa methods. The isothermal experimental data showed an autocatalytic behavior compared with the model proposed by Kamal. Activation energy and kinetic parameters were determined by fitting experimental data. This model provided a good description of the cure kinetics up to onset of vitrification. Diffusion control was incorporated to describe the postvitrification region. By combining the autocatalytic model and the diffusion factor, it was possible to predict the cure kinetics over the whole conversion range. The behavior of the cure kinetics of the DGEBA was similar with all the diamines used. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1759–1768, 2007
Novel method for preparation of polyurethane elastomers with improved thermal stability and electrical insulating properties
Authors: Yeganeh Hamid , Talemi Pejman Hojati , Jamshidi Sadegh
Published: November 2006

A novel method was developed for the preparation of polyurethane with enhanced thermal stability and electrical insulation properties via the reaction of epoxy‐terminated polyurethane prepolymer (EPU) and poly(amic acid) (PAA). EPUs were synthesized from the reaction of glycidol with NCO‐terminated polyurethane prepolymers, which were prepared from the reaction of polycaprolactone‐based polyol (CAPA) of different molecular weights and some commercially available diisocyanates including hexamethylene diisocyante, toluene diisocyanate, and 4,4′‐methylene bis(phenyl isocyanate). PAA was prepared from the reaction of equimolar amounts of pyromellitic dianhydride and oxydianiline. The effects of PAA content, the nature of diisocyanate, and the molecular weight of CAPA on the mechanical, thermal, thermomechanical, and electrical properties of the final networks were investigated. The crosslink density of the samples was determined according to an equilibrium swelling method using the Flory–Rehner equation and was correlated to the structure of the final polymers. Gel content and activation energy of network formation in the absence and the presence of a tertiary amine catalyst were also studied. The results showed considerable improvement in the thermal, electrical, and mechanical properties compared to those of other common polyurethanes. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1776–1785, 2007
Supercritical gas–polymer interactions with applications in the petroleum industry. Determination of thermophysical properties
Authors: Boyer Séverine A. E. , Klopffer Marie‐Hélène , Martin Joseph , Grolier Jean‐Pierre E.
Published: November 2006

The knowledge of chemical equilibria in {gas–polymer} systems plays an essential role as regards the safety of transport of petroleum products in polymer‐made pipes. Thermophysical properties of thermoplastic semicrystalline polymers are key data for the development of several engineering applications. These applications require the investigation of the behavior of a polymer, in the solid state i.e., between glass‐transition temperature Tg and melting‐transition temperature Tm, submitted to the triple thermal, barometric, and chemical constraint. The chemical stress results from supercritical fluid sorption. The relatively high temperature and pressure, industrial operating conditions, require for laboratory investigations the use of sophisticated experimental instrumentation in which such extreme conditions can be reproduced. In this context, coupling gas solubility and swelling techniques (VW‐PVT) on the one hand, calorimetry and PVT techniques (PCSC) on the other hand, over extended temperature and pressure ranges, provide a wide spectrum of thermophysical and thermomechanical properties like solubility and isobaric thermal expansion, in absence or in presence of solubilized gases. Selected examples taken in the petroleum industry, dealing with different polymers [medium density polyethylene, poly(vinylidene fluoride)] in presence of gases (carbon dioxide CO2, nitrogen N2), serve to illustrate the importance of gas solubility (VW‐PVT) (Boyer and Grolier, Polymer 2005, 46, 3737) data and of heats of interaction (PCSC) measurements (Randzio et al., Fr. Pat. 9109227, Pol. Pat. 295285; Randzio, Chem Soc Rev 1996, 25, 383; Boyer et al., J Polym Sci Part B: Polym Phys 2006, 44, 185) in the broad field of applied polymer thermodynamics. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1706–1722, 2007
Polyetherols obtained from 6‐aminouracil and oxiranes
Authors: Chmiel‐Szukiewicz Elżbieta
Published: November 2006

Reactions of 6‐aminouracil with an excess of oxiranes (ethylene oxide and propylene oxide) in dimethylsulfoxide in the presence of triethylamine as a catalyst leads to polyetherols with a 1,3‐pyrimidine ring. The products are analyzed using IR and 1H‐NMR spectroscopies. The physical properties and thermal stability of the prepared polyetherols are investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1466–1472, 2007
Urea–formaldehyde‐resin gel time as affected by the pH value, solid content, and catalyst
Authors: Xing Cheng , Zhang S. Y. , Deng James , Wang Siqun
Published: November 2006

An experiment was conducted to investigate the effects of the resin solid content, catalyst content, and pH value obtained by the addition of two kinds of catalysts on the gel time of a urea–formaldehyde (UF) resin. Upon the addition of ammonium chloride, the pH value of the resin mixture decreased to 7 but not significantly further because of the limited free formaldehyde in the system. The pH values of the critical points, at which the resin‐curing rate dramatically increased and the gel time was reduced, were above 7 for both catalysts. To achieve the same gel time, the required pH value of the UF resin adjusted with ammonium chloride was higher than that of the resin modified by hydrochloric acid. This indicated that the main effects of ammonium chloride on the UF‐resin cure included both the release of hydrochloric acid and the catalysis of the reactants in the UF‐resin system. The gel time of the UF resin obviously decreased with increasing catalyst and resin solid contents and with decreasing pH. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1566–1569, 2007
In situ preparation and properties of high‐solid‐content and low‐viscosity poly(methyl methacrylate/n‐butyl acrylate/acrylic acid)/poly(styrene/acrylic acid) composite latexes
Authors: Ai Zhao‐Quan , Zhou Qi‐Long , Xie Chang‐Sheng , Zhang Hong‐Tao
Published: November 2006

With monodispersed poly(methyl methacrylate/n‐butyl acrylate/acrylic acid) [P(MMA/BA/AA)] seeded latex with a particle size of 485 nm and a solid content of 50 wt % as a medium, a series of stable P(MMA/BA/AA)/poly(styrene/acrylic acid) composite latexes with a high solid content (70 wt %) and low viscosities (500–1000 mPa · s when the shear rate was 21 s−1) was prepared in situ via simple two‐step semicontinuous monomer adding technology. The coagulum ratio of polymerization was about 0.05 wt %. The particle size distribution of such latexes was bimodal, in which the large particle was about 589 nm and the small one was about 80 nm. The latexes combined good mechanical properties with good film‐forming properties. Differential scanning calorimetry showed that the corresponding latex film had a two‐phase structure. The morphology of the latex film was characterized with atomic force microscopy and scanning electron microscopy. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1815–1825, 2007
Impact of H+ ion beam irradiation on Matrimid®. II. Evolution in gas transport properties
Authors: Hu Ling , Xu Xinglong , Coleman Maria R.
Published: November 2006

Ion beam irradiation is an easily controlled method to modify the chemical structure and microstructure of polymers including the fractional free volume, free volume distribution and chain mobility, thus altering the gas transport properties of the irradiated polymers. The previous paper focused on the impact of H+ ion beam irradiation on chemical structural evolution of the polyimide Matrimid®. This paper focuses on the impact of H+ ion beam irradiation on microstructure and gas permeation properties of Matrimid®. Irradiation at low ion fluence resulted in slight decreases in permeabilities for five gases (i.e., He, CO2, O2, N2, and CH4) with increases in permselectivities for some gas pairs (e.g., He/CH4 and He/N2). In contrast, irradiation at relatively high ion fluences resulted in simultaneous increases in permeabilities and permselectivities for most gas pairs (e.g., He/CH4, He/N2, O2/N2, and CO2/CH4). While Matrimid® has bulk gas permeation properties that are below the range of commercially interesting polymers, samples irradiated at high ion fluences exhibited significant improvement in gas separation performances. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1670–1680, 2007
Reciprocal influence of succinimide and oligodiene‐ and oligoolefin‐based sulfur‐containing alkylphenols
Authors: Biglova R. Z. , Galimzyanova A. U. , Talipov R. F. , Gerchikov A. Ya. , Khairullina V. R. , Zaikov G. E.
Published: November 2006

Reciprocal influence of antioxidizing and detergent‐dispersive components of batch additives have been studied. Oligomers of piperylene and isobutylene functionalized by element sulfur and phenols in combination with succinimide have been chosen as the object of research. Constants of inhibition rates have been determined for oligomer antioxidizing agents. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1842–1846, 2007
pH‐response superabsorbant hydrogel synthesized by ultraviolet photopolymerization
Authors: Ruan Weiqing , Lian Yanqing , Zhen Tao , Huang Luning , Qiao Jinliang
Published: November 2006

A new synthesis method of pH‐response superabsorbent hydrogels (SHG) was achieved by direct ultraviolet (UV) photopolymerization, and in particular, the synthesis of SHGs of acrylic acid (AA), sodium acrylate (AANa), and methacrylcholine chloride (MACC) tricomponent copolymer by UV photopolymerization were investigated. The pH value responsive behavior of SHG with different monomer ratios of MACC and AA was researched, and SHG showed large swelling properties at pH value approximately 7. Influences of monomer ratio (mol) of AANa to AA, photoinitiators, crosslinking agents, and exposure time of UV light on the water absorbent properties were studied. The results showed that the water absorbent capacity of SHG based on photoinitiators: Esacure KTO46 or Irgacure 651 can reach comparatively high, N,N′‐Methylene bisacrylamide and diethylene glycol diacrylate (DEGDA) were high efficient crosslinking agents for its crosslinking the molecular chains through attending the copolymerization with monomers. When the exposure time was 10 min, the distilled water absorbency of SHG was 1503 mL/g under the condition: content of MACC, 14.3 wt %; monomer ratio (mol) of AANa to AA: 5.67; content of DEGDA and Irgacure 651, 0.0025 and 0.25 wt %. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1847–1852, 2007
Stable P‐Heterocyclic Carbenes: Scope and Limitations
Authors: Masuda Jason D. , Martin David , Lyon‐Saunier Celine , Baceiredo Antoine , Gornitzka Heinz , Donnadieu Bruno , Bertrand Guy
Published: November 2006

The conjugate acids (PHCH+s) of P‐heterocyclic carbenes (PHCs) are prepared by formal [3+2] cycloaddition of a 1,3‐diphosphaallyl or 1,3‐phosphinophosphenium cation with various nitriles. The effect of the phosphorus substituent on the fate of the cyclization and on that of the counteranion and base in the subsequent deprotonation reaction are reported. Two PHCs that are indefinitely stable in the solid state are described. In solution, one of them, made from acetonitrile, undergoes a facile [3+2] cycloreversion, whereas the other, based on dimethyl cyanamide, is stable, presumably owing to its zwitterionic structure, which involves a tricoordinate pentavalent phosphorus atom. The reactivity of PHCs is strongly driven by the high electrophilicity of the phosphorus centers, as demonstrated by their reactivity with water and benzaldehyde. Although both PHCs reported in this paper are direct analogues of the least‐basic NHCs, their basicity is comparable to those of the more strongly basic NHCs (as determined by comparison of the carbonyl stretching frequencies of their corresponding cis‐[RhCl‐(CO)2(L)] complexes).
Dehalogenation of 1,3‐Diiodotricyclo[3.3.0.03,7]octane: Generation of 1,3‐Dehydrotricyclo[3.3.0.03,7]octane, a 2,5‐Methano‐Bridged [2.2.1]Propellane
Authors: Ayats Carles , Camps Pelayo , Fernández José A. , Vázquez Santiago
Published: November 2006

Compounds isolated from the reaction of (±)‐1,3‐diiodotricyclo[3.3.0.03,7]octane with molten sodium or tBuLi suggest the intermediate formation of (±)‐1,3‐dehydrotricyclo[3.3.0.03,7]octane. Worthy of note is the formation of stereoisomeric bi(5‐methylenebicyclo[2.2.1]hept‐2‐ylidene) derivatives, probably by coupling of two units of (±)‐1,3‐dehydrotricyclo[3.3.0.03,7]octane of the same or different absolute configuration followed by fragmentation, processes that have been studied by theoretical calculations.
Michael Additions of Methylene Active Compounds to Chalcone in Ionic Liquids without any Catalyst: The Peculiar Properties of Ionic Liquids
Authors: Mečiarová Mária , Toma Štefan
Published: November 2006

Michael additions of malonodinitrile as well as several other reagents to chalcone have been found to proceed well in pure ionic liquids, without the addition of any catalyst. The catalytic effect of the residual acidity caused by hydrolysis of ionic liquids anions was excluded because HCl in dichloromethane did not catalyse the Michael addition of malonodinitrile. Piperidine was tested as the catalyst and was found to be a much better catalyst in ionic liquids than in dichloromethane. Therefore, the following question arose: what is the effect of ionic liquids on the dissociation constants of CH acids?
Experimental and DFT Study of the Tautomeric Behavior of Cobalt‐Containing Secondary Phosphine Oxides
Authors: Wei Chu‐Hung , Wu Cheng‐En , Huang Yi‐Luen , Kultyshev Roman G. , Hong Fung‐E.
Published: November 2006

New cobalt‐containing secondary phosphine oxides [(μ‐PPh2CH2PPh2)Co2(CO)4{μ,η‐PhCCP(O)(H)(R)}] (8 a: R=tBu; 8 b: R=Ph) were prepared by reaction of secondary phosphine oxides PhCCP‐ (O)(H)(R) (6 a: R=tBu; 6 b: R=Ph) with dppm‐bridged dicobalt complex [(μ‐PPh2CH2PPh2)Co2(CO)6] (2). The molecular structures of 8 a and 8 b were determined by single‐crystal X‐ray diffraction. Although palladium‐catalyzed Heck reactions employing 8 b as ligand gave satisfying results, 8 a performed poorly in the same reaction. Judging from these results, a tautomeric equilibrium between 8 b and its isomeric form [(μ‐PPh2CH2PPh2)Co2(CO)4{μ,η‐PhCCP(OH)(Ph)}] 8 b′ indeed takes place, but it is unlikely between 8 a and [(μ‐PPh2CH2PPh2)Co2(CO)4{μ,η‐PhCCP(OH)(tBu)}] (8 a′). The DFT studies demonstrated that reasonable activation energies for the tautomeric conversions can be achieved only via a bimolecular pathway. Since a tBu group is much larger than a Ph group, the conversion is presumably only feasible in the case of 8 b⇌8 b′, but not in the case of 8 a⇌8 a′. Another cobalt‐containing phosphine, namely, [(μ‐PPh2CH2PPh2)Co2(CO)4{μ,η‐PhCCP(NEt2)(tBu)}] (7 a), and its oxidation product [(μ‐PPh2CH2PPh2)Co2(CO)4{μ,η‐PhCCP(O)(NEt2)(tBu)}] 7 a′ were prepared from the reaction of PhCCP(NEt2)(tBu) (5 a) with 2. The molecular structures of 7 a and 7 a′ were determined by single‐crystal X‐ray diffraction. The phosphorus atom is surrounded by substituents in a tetrahedral environment. A PN single bond (1.676(3) Å) is observed in the molecular structure of 7 a. Heck reactions employing 7 a/Pd(OAc)2 as catalyst system exhibited efficiency comparable to that of 8 a/Pd(OAc)2.
Total Syntheses of the Actin‐Binding Macrolides Latrunculin A, B, C, M, S and 16‐epi‐Latrunculin B
Authors: Fürstner Alois , De Souza Dominic , Turet Laurent , Fenster Michaël D. B. , Parra‐Rapado Liliana , Wirtz Conny , Mynott Richard , Lehmann Christian W.
Published: November 2006

The latrunculins are highly selective actin‐binding marine natural products and as such play an important role as probe molecules for chemical biology. A short, concise and largely catalysis‐based approach to this family of bioactive macrolides is presented. Specifically, the macrocyclic skeletons of the targets were forged by ring‐closing alkyne metathesis (RCAM) or enyne–yne metathesis of suitable diyne or enyne–yne precursors, respectively. This transformation was best achieved with the aid of [(tBu)(Me2C6H3)N]3Mo (37) as precatalyst activated in situ with CH2Cl2, as previously described. This catalyst system is strictly chemoselective for the triple bond and does not affect the olefinic sites of the substrates. Moreover, the molybdenum‐based catalyst turned out to be broader in scope than the Schrock alkylidyne complex [(tBuO)3WCCMe3] (38), which afforded cycloalkyne 35 in good yield but failed in closely related cases. The required metathesis precursors were assembled in a highly convergent fashion from three building blocks derived from acetoacetate, cysteine, and (+)‐citronellene. The key fragment coupling can either be performed via a titanium aldol reaction or, preferentially, by a sequence involving a Horner–Wadsworth–Emmons olefination followed by a protonation/cyclization/diastereoselective hydration cascade. Iron‐catalyzed CC‐bond formations were used to prepare the basic building blocks in an efficient manner. This synthesis blueprint gave access to latrunculin B (2), its naturally occurring 16‐epimer 3, as well as the even more potent actin binder latrunculin A (1) in excellent overall yields. Because of the sensitivity of the 1,3‐diene motif of the latter, however, the judicious choice of protecting groups and the proper phasing of their cleavage was decisive for the success of the total synthesis. Since latrunculin A and B had previously been converted into latrunculin S, C and M, respectively, formal total syntheses of these congeners have also been achieved. Finally, a previously unknown acid‐catalyzed degradation pathway of these bioactive natural products is described. The cysteine‐derived ketone 18, the tetrahydropyranyl segment 31 serving as the common synthesis platform for the preparation of all naturally occurring latrunculins, as well as the somewhat strained cycloalkyne 35 formed by the RCAM reaction en route to 2 were characterized by X‐ray crystallography.
Stereochemical identification of (R)‐ and (S)‐ibuprofen using residual dipolar couplings, NMR, and modeling
Authors: Marathias Vasilios M. , Tawa Gregory J. , Goljer Igor , Bach Alvin C.
Published: November 2006

In this work, we describe an NMR‐based method that utilizes an orientation media composed of the chiral polypeptide liquid crystal poly‐γ‐benzyl‐L‐glutamate (PBLG) dissolved in CDCl3, to measure the 1H‐1H, 1H‐13C and 13C‐13C residual dipolar couplings (RDCs) of (R) and (S)‐ibuprofen. Calculated RDCs, obtained from the lowest energy conformers, are then compared with the experimentally measured RDCs to predict the stereochemistry of each enantiomer. Excellent agreement between calculated and experimental RDCs was found when the lowest energy structure of each enantiomer, obtained in a simulated PBLG/CDCl3 environment, was used to back‐calculate the RDCs. This method is generally useful for small molecular weight molecules that possess either one or two chiral centers, are soluble in low viscosity organic solvents, and will not crystallize (Clegg, Crystal Structure Analysis. Principles and Practice. New York: Oxford University Press; 2002) or cannot be derivatized with a Mosher's reagent (Dale and Mosher, J Am Chem Soc 1973;95:512–519). Chirality, 2006. © 2006 Wiley‐Liss, Inc.
Growth and properties of an organometallic nonlinear optical crystal: bis(isothiocyanato)‐bis(4‐methylpyridine)zinc(II) (Zn(SCN)2(C6H7N)2)
Authors: Zhu L. Y. , Xu D. , Wang X. Q. , Liu X. J. , Zhang G. H. , Sun J.
Published: November 2006

Bis(isothiocyanato)‐bis(4‐methylpyridine)zinc(II)(Zn(SCN)2(C6H7N)2), (abbreviated as ZBNC) single crystals of optical quality have been grown from acetone solution by the slow temperature‐lowering method. Its solubilities at different temperatures in acetone were measured. The X‐ray powder diffraction (XRPD) spectroscopy of ZBNC crystal was performed at room temperature. The second harmonic generation (SHG) efficiency was determined by powder technique of Kurtz and Perry using Nd:YAG laser, which is equivalent to KDP crystal. The thermal decomposition process was characterized by thermal gravity and differential thermal analysis (TG\DTA). The specific heat of the crystal is 1440.67 J/mol·K at 325 K. The IR spectrum was recorded in the 500∼3500 cm–1 region, using KBr pellets on a Nicolet 170sx FT‐IR spectrometer. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimal allocation of distributed generation and reactive sources considering tap positions of voltage regulators as control variables
Authors: Golshan Mohamad Esmail Hamedani , Ali Arefifar Seyed
Published: November 2006

In this paper, by defining and solving an optimization problem, amount of distributed generators (DGs) and reactive power sources (RSs) in selected buses of a distribution system are computed to make up a given total of distributed generation for minimizing losses, line loadings, and total required reactive power capacity. The formulated problem is a combinatorial problem, therefore Tabu search algorithm is applied for solving the optimization problem. Results of solving the optimization problem for a radial 33‐bus distribution system and a meshed 6‐bus system are presented. When using less amount of reactive capacity, regarding tap positions of voltage regulators as control variables has considerable role in loss reduction and improvement of voltage profile. In the case of meshed systems, including line loadings in the cost function can significantly change results of solving the optimization problem such as amount of the required reactive capacity and how to assign DGs and RSs to the selected buses. Copyright © 2006 John Wiley & Sons, Ltd.
Monte Carlo simulation techniques for optimisation of phase shifter settings
Authors: Verboomen J. , Van Hertem D. , Schavemaker P. H. , Spaan F. J. C. M. , Delince J‐M. , Belmans R. , Kling W. L.
Published: November 2006

The Netherlands has installed two phase shifting transformers (PSTs) in order to more evenly distribute the load on the interconnectors with Germany. Belgium is planning to install four devices to tackle the problem of transit flows between France and Germany and to control the flow on the parallel paths between Belgium and France. One phase shifter on the border of the Netherlands and Germany was already installed for a long time. The coordination of all the phase shifters is very important in order to take full advantage of these devices, but also to guarantee a safe situation and not to mutually counteract control actions. In this paper, a new Monte Carlo based approach is proposed to find the optimal settings of different phase shifters. The goal is to maximise the import capacity for both the Netherlands and Belgium. Copyright © 2006 John Wiley & Sons, Ltd.
A new reduction method for reliability assessment of bulk electric power systems
Authors: Gharaghozloo H. , Haghifam M.‐R. , Haubrich H.‐J. , Firozabad M. Fotuhi
Published: November 2006

Data requirements and large computation times are still major difficulties in bulk electric systems (BES). When small area of BES is noticed as area of interest (AI) in reliability studies, the other parts of the network can be considered as interconnected area (IA). A reduction method based on generations and loads importance of IA is presented in this paper to equivalent the IA. Generation Reliability Importance Factor (GRIF) of generation units and Load Reliability Importance Factor (LRIF) of loads with respect to power system reliability are defined for the generation and load points associated with the IA. Application of graph theory concept is used for obtaining the equivalent network. With some rules based on graph networks, an equivalent network will be obtained for this network and some nodes are remained in final network such as main nodes based on GRIF and LRIF indices. The applicability of the proposed approach is examined using the 3‐area IEEE‐RTS network and the results are presented and compared for various case studies. Copyright © 2006 John Wiley & Sons, Ltd.
Cortical brain responses during passive nonpainful median nerve stimulation at low frequencies (0.5–4 Hz): An fMRI study
Authors: Ferretti Antonio , Babiloni Claudio , Arienzo Donatello , Del Gratta Cosimo , Rossini Paolo Maria , Tartaro Armando , Romani Gian Luca
Published: November 2006

Previous findings have shown that the human somatosensory cortical systems that are activated by passive nonpainful electrical stimulation include the contralateral primary somatosensory area (SI), bilateral secondary somatosensory area (SII), and bilateral insula. The present study tested the hypothesis that these areas have different sensitivities to stimulation frequency in the condition of passive stimulation. Functional MRI (fMRI) was recorded in 24 normal volunteers during nonpainful electrical median nerve stimulations at 0.5, 1, 2, and 4 Hz repetition rates in separate recording blocks in pseudorandom order. Results of the blood oxygen level‐dependent (BOLD) effect showed that the contralateral SI, the bilateral SII, and the bilateral insula were active during these stimulations. As a major finding, only the contralateral SI increased its activation with the increase of the stimulus frequency at the mentioned range. The fact that nonpainful median‐nerve electrical stimuli at 4 Hz induces a larger BOLD response is of interest both for basic research and clinical applications in subjects unable to perform cognitive tasks in the fMRI scanner. Hum Brain Mapp 2006. © 2006 Wiley‐Liss, Inc.
Caffeine attenuates practice effects in word stem completion as measured by fMRI BOLD signal
Authors: Bendlin Barbara B. , Trouard Theodore P. , Ryan Lee
Published: November 2006

Caffeine ingestion results in increased brain cell metabolism (Nehlig et al. [1992] Brain Res Brain Res Rev 17:139–170) and decreased cerebral blood flow (Field et al. [2003] Radiology 227:129–135; Mulderink et al. [2002] Neuroimage 15:37–44). The current study investigated the effect of caffeine in a word stem completion task using only novel word stems (no repeated stimuli). Resting perfusion was measured with arterial spin labeled perfusion MRI, along with blood oxygenation level‐dependent (BOLD) signal before and after ingestion of regular coffee, decaffeinated coffee, and water. Based on previous research (Laurienti et al. [2002] Neuroimage 17:751–757; Mulderink et al. [2002] Neuroimage 15:37–44), we hypothesized that caffeine would result in increased BOLD signal intensity and extent of BOLD activation. As expected, caffeine resulted in a significant decrease in cerebral perfusion. However, both the control and caffeine groups showed an increase in BOLD signal amplitude across two sets of novel word stems. Additionally, the control group showed a 50% reduction in the extent of BOLD activation, while the caffeine group showed no change in activation extent. Neither group showed changes in BOLD baseline signal over time, which had been suggested to mediate caffeine‐related BOLD signal changes. The results suggest that caffeine may attenuate general task practice effects that have been described in recent functional MRI studies of word stem completion (Buckner et al. [2000] Brain 123:620–640). Hum Brain Mapp 2006. © 2006 Wiley‐Liss, Inc.
Polyribosomes are increased in spines of CA1 dendrites 2 h after the induction of LTP in mature rat hippocampal slices
Authors: Bourne Jennifer N. , Sorra Karin E. , Hurlburt Jamie , Harris Kristen M.
Published: November 2006

Enduring long‐term potentiation (LTP) requires immediate protein synthesis, hence we assessed whether more polyribosomes are present in dendritic spines of mature hippocampal dendrites after the induction of LTP. Reconstructions from serial section transmission electron microscopy (sSTEM) revealed more dendritic polyribosomes 2 h posttetanus, relative to low‐frequency stimulation (LFS). Polyribosomes were present in spines of all shapes with larger postsynaptic densities after 2 h, suggesting a coordinated local protein synthesis among many synapses to replenish proteins utilized during an earlier phase of LTP. © 2006 Wiley‐Liss, Inc.
Intranuclear paracrystals observed in striated muscle specific LIM protein‐deficient mouse cardiomyocytes
Authors: Muto M. , Sargeant A. , Tangkawattana P. , Takeyasu K. , Nishijima Y. , Bonagura J. , Hoshijima M. , Nakade T. , Hosaka Y. , Faulkner G. , Tomono K. , Yamaguchi M.
Published: November 2006

A paracrystalline structure was observed within left ventricular cardiomyocyte nuclei of MLP−/− mice. The paracrystal possessed cross lines, ∼8.0 μm long and 0.3 μm wide, with a slender spindle shape and a periodicity of 13 nm. Paracrystals were best observed along the longitudinal orientation of myofibrils and were detected in less than 10% of the nuclei observed. One dimension of the protein unit forming the paracrystal was 8.5 nm long. The electron density of the paracrystal appeared to be slightly higher than that of heterochromatin, suggesting that RNA‐associated proteins are constituents of the paracrystal. This is the first report of intranuclear paracrystals in cardiomyocytes, which appear to be unique to MLP−/− mice. Microsc. Res. Tech. 2007. © 2006 Wiley‐Liss, Inc.
Mechanisms controlling venom expulsion in the western diamondback rattlesnake, Crotalus atrox
Authors: Young Bruce A. , Kardong Kenneth V.
Published: November 2006

Although many studies have documented variation in the amount of venom expended during bites of venomous snakes, the mechanistic source of this variation remains uncertain. This study used experimental techniques to examine how two different features of the venom delivery system, the muscle surrounding the venom gland (the Compressor Glandulae in the rattlesnake) and the fang sheath, could influence venom flow in the western diamondback rattlesnake, Crotalus atrox. Differential contraction of the Compressor Glandulae explained only approximately 30% of the variation in venom flow. Lifting (compression) of the fang sheath as occurs during a normal strike produced marked increases in venom flow; these changes were closely correlated and exceed in magnitude by almost 10 × those recorded from the Compressor Glandulae alone. These results suggest that variation in these two aspects of the venom delivery system—both in terms of magnitude and temporal patterning—explain most of the observed variation in venom injection. The lack of functional or mechanical links between the Compressor Glandulae and the fang sheath, and the lack of skeletal or smooth muscle within the fang sheath, make it unlikely that variation in venom flow is under direct neural control. Instead, differential venom injection results from differences in the pressurization by the Compressor Glandulae, the gate keeping effects of the fang sheath and enclosed soft‐tissue chambers, and by differences in the pressure returned by peripheral resistance of the target tissue. J. Exp. Zool. 305A:18–27, 2007. © 2006 Wiley‐Liss, Inc.
Uteroglobin induces the development and cellular proliferation of the mouse early embryo
Authors: Riffo Marta , González Keybell Díaz , Nieto Antonio
Published: November 2006

Two‐cell mouse embryos cultured in vitro in the presence of either purified rabbit uteroglobin (UG) or recombinant human UG developed and proliferated faster than controls cultured in the absence of this protein. Both the percentage of embryos developing to the blastocyst stage and the number of cells per embryo were increased. Treatment with UG for 3 hr was enough to trigger this response. The effect of UG was blocked by genistein, an inhibitor of tyrosine protein kinases, suggesting the involvement of these kinases in the stimulation of the embryo by UG. To further support this suggestion, embryos were metabolically labeled in vitro with [32P] and the phosphorylated proteins were immunoprecipitated with anti‐phosphotyrosine. Analysis of the immunoprecipitates by SDS‐PAGE showed that UG induced the phosphorylation of several proteins of Mr between 200 and 37 kDa. This induction was observed after 1 hr of stimulation with UG and further increased after 3 hr of treatment. Since UG is synthesized and secreted in the uterus and the oviduct, these results suggest a physiological role of this protein in the correct development of the embryo in vivo. J. Exp. Zool. 305A:28–34, 2007. © 2006 Wiley‐Liss, Inc.
Cytological mechanisms of gynogenesis and sperm incorporation in unreduced diploid eggs of the clonal loach, Misgurnus anguillicaudatus (Teleostei: Cobitidae)
Authors: Itono Masaki , Okabayashi Naoki , Morishima Kagayaki , Fujimoto Takafumi , Yoshikawa Hiroyuki , Yamaha Etsuro , Arai Katsutoshi
Published: November 2006

The loach Misgurnus anguillicaudatus comprises diploid clonal, triploid and diploid–triploid mosaic individuals in a wild population on Hokkaido island, Japan. When diploid eggs of clonal loaches are fertilized by haploid sperm of normal bisexual loaches, both diploid clonal and non‐diploid aclonal individuals occur in the progeny. Flow cytometry and microsatellite analyses revealed that the occurrence of triploid, diploid–triploid and other progeny was essentially due to the genetic incorporation of sperm to diploid clonal genomes of unreduced eggs. In this study, we examined the influence of water temperature from fertilization to early embryogenesis on frequencies of diploid clonal and other progeny and observed that progeny of three out of four clonal females examined exhibited approximately constant rates of diploid clonal individuals (54.2–68.9%) at hatching stage. Thus, no drastic increase of non‐diploid progeny was detected. However, the 28°C group of the fourth clonal female gave significantly lower rate (28.1%) of diploid clonal progeny, suggesting that this temperature might be a critical or a borderline temperature inducing sperm incorporation. We also examined the cytological process by which diploid clonal and other aclonal progeny develop after fertilization. In some fertilized eggs, the sperm nucleus remained condensed throughout fertilization and early embryogenesis and never fused with the female pronucleus. This cytological observation concludes that clonal eggs develop by the mechanism of gynogenesis. However, some other eggs showed the cytological process of syngamy between the female pronucleus and an accidentally formed male nucleus, suggesting the formation of triploid progeny. The syngamy between an accidentally activated sperm nucleus with a male pronucleus‐like structure and nucleus of a blastomere of gynogenetically developing clonal diploid embryo might produce a diploid–triploid mosaic individual. J. Exp. Zool. 305A:35–50, 2007. © 2006 Wiley‐Liss, Inc.
Moving in social circles—social circle membership and performance implications
Authors: Verbeke Willem , Wuyts Stefan
Published: November 2006

We investigate social circles in intra‐firm settings. First, we argue that social circles are inhabited by individuals whose attitudes display fit with the objectives of the social circle rather than more self‐centered instrumentalism or calculation. For a test of this hypothesis, we distinguish between friendship circles and strategy‐influence circles. We find that friendship circle membership is positively associated with attitudes that display empathic concern but negatively with more instrumental attitudes, whereas strategy‐influence circle membership is positively associated with attitudes that display long‐term ambition but negatively with attitudes that display short‐term calculation. Second, we argue and find that membership of social circles affects individual performance (social circles foster the exchange of information, for which we find clear evidence), albeit not necessarily in a linear fashion. Our new insights into social circle membership and performance implications can guide individuals in seeking access to such social circles and can aid management in understanding and perhaps influencing intra‐firm knowledge flows. Copyright © 2006 John Wiley & Sons, Ltd.
On asymptotic properties of multidimensional α ‐stable densities
Authors: Zaigraev A.
Published: November 2006

A class of multidimensional α ‐stable distributions is considered. The Poisson spectral measure of each distribution is assumed to be absolutely continuous with respect to the surface Lebesgue measure. The author concentrates his attention on the asymptotic behavior of the α ‐stable densities s (x) as |x | →∞and |x | → 0. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The coexistence problem for Heun's differential equation
Authors: Volkmer Hans
Published: November 2006

For certain parameter sets all solutions of Heun's equation are analytic in ℰ \ [0, 1], where ℰ is a (small) neighborhood of [0, 1]. These parameters sets are investigated. The results generalize those on coexistence of periodic solutions of the Lamé and Ince equations due to Ince, Magnus and Winkler. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Moving triangles over a sphere
Authors: Alonso Javier , Martín Pedro
Published: November 2006

If three points on a circle are rotated around the circle in such a way that the lengths of two sides of the triangle they define do not change, then neither does the length of the third side. If instead of a circle we consider the unit sphere of a norm in a two‐dimensional normed space, then the above property characterizes the ellipses. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Independent validation of SCOPA–psychosocial and metric properties of the PDQ‐39 Brazilian version
Authors: Carod‐Artal Francisco Javier , Martinez‐Martin Pablo , Vargas Antonio Pedro
Published: November 2006

The objective of this study was to perform an independent validation of the Scales for Outcomes in Parkinson's Disease–Psychosocial questionnaire (SCOPA‐PS) and assessment of the Parkinson's Disease Questionnaire (PDQ‐39), Brazilian version. Patients were evaluated by means of the Unified Parkinson's Disease Rating Scale, Hoehn and Yahr staging (HY), Schwab and England scale, Mini‐Mental State Examination, and Hospital Anxiety and Depression Scale. Health‐related quality of life was evaluated using the MOS‐Short Form 36 (SF‐36), PDQ‐39, and SCOPA‐PS. One hundred forty‐four patients were included (mean age, 62 years; 53.5% males; mean duration of illness, 6.6 years; HY, 1–4). Mean SCOPA‐PS and PDQ‐39 Summary Index (SI) were 39.2 and 40.7, respectively. The internal consistency of SCOPA‐PS (Cronbach's alpha = 0.84; item–total correlation, 0.44–0.73) and PDQ‐39 dimensions (alpha = 0.61–0.85; item–total correlation, 0.46–0.82) were satisfactory. Concerning the stability of the questionnaires, intraclass correlation coefficient (ICC) values were 0.71 for the SCOPA‐PS and 0.86 for the PDQ‐39 SI. ICC for PDQ‐39 dimensions ranged from 0.52 (social support) to 0.80 (stigma). Standard error of measurement (SEM) values for each PDQ‐39 dimension ranged from 0.49 (emotional well‐being) to 17.52 (social support). SEM values for SCOPA‐PS and PDQ‐39 SI were 11.84 and 6.72, respectively. A significant correlation of SCOPA‐PS and PDQ‐39 SI with the SF‐36 physical (−0.42 and −0.52, respectively) and mental components (−0.41) was found. Correlation between SCOPA‐PS and PDQ‐39 SI was 0.73 (all coefficients,P< 0.0001). The SCOPA‐PS and PDQ‐39, Brazilian versions, have satisfactory metric attributes. © 2006 Movement Disorder Society
Structural determination of silymins A and B, new pentacyclic triterpenes from Silybum marianum, by 1D and 2D NMR spectroscopy
Authors: Ahmed Ejaz , Noor Atia tun , Malik Abdul , Ferheen Sadia , Afza Nighat
Published: November 2006

Silymins A (1) and B (2), the new pentacyclic triterpenes, have been isolated from ethyl acetate fraction of Silybum marianum and their structures assigned from 1H and 13C NMR spectra, DEPT and by 2D COSY, NOE and HMBC experiments. Copyright © 2007 John Wiley & Sons, Ltd.
Superabsorbent composite. X. Effects of saponification on properties of polyacrylamide/attapulgite
Authors: Zhang Junping , Li An , Wang Aiqin
Published: November 2006

A novel superabsorbent composite from acrylamide (AM) and attapulgite (APT), polyacrylamide/attapulgite (PAM/APT), was prepared by polymerizing AM with the existence of APT in aqueous solution, and then saponified with NaOH solution. Considering the impacts of hydrophilic groups (COONa, COOH, and CONH2) on properties of the PAM/APT composite, the effects of saponification mode, molar ratio of NaOH to AM and saponification time on water absorbency, hydrophilic group content, and surface morphology were investigated systematically. The results indicate that the two‐step adding NaOH mode is superior to that of the one‐step mode. Among the superabsorbent composite incorporated with 30 wt% APT, the composite saponified at 95°C for 2 h with the molar ratio of 0.6 for NaOH to AM acquired the highest water absorbencies of 1715g g−1 and 87.8g g−1 in distilled water and in 0.9 wt% NaCl solution, respectively. The molar ratio of various hydrophilic groups at this time was 10:3:11 for COONa, COOH, and CONH2 determined using linear potentiometric titration method. POLYM. ENG. SCI. 46:1762–1767, 2006. © 2006 Society of Plastics Engineers.
Comparison of elastic and tactile behavior of human skin and elastomeric materials through tribological tests
Authors: Elleuch Khaled , Elleuch Riadh , Zahouani Hassan
Published: November 2006

The current article describes static and frictional contact tests carried out with spherical indenter on both human skin surface and elastomeric materials. This tribological study is performed to analyze the elasticity and tactile properties of the human skin, and therefore to evaluate reliability of human skin behavior simulation through the considered elastomeric materials. Finite element analyses of indentation tests are proposed. Critical normal load was found when numerical and experimental results were confronted. Such critical force defines the limit of elastic model application. POLYM. ENG. SCI., 46:1715–1720, 2006. © 2006 Society of Plastics Engineers