bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hetero‐π‐systems from 2 + 2 cycloreversion, part 2.1Ab initio thermochemical study of heterocyclobutanes 2 + 2 cycloreversion to form heteroethenes H2C=X (X=NH, O, SiH2, PH, S)
Authors: Gusel'nikov Leonid E. , Avakyan Vitaly G. , Guselnikov Stephan L. 
Published: November 2007

AbstractAb initio and DFT thermochemical study of diradical mechanism of 2 + 2 cycloreversion of parent heterocyclobutanes and 1,3‐diheterocyclobutanes, cyclo‐(CH2CH2CH2X), and cyclo‐(CH2XCH2X), where X = NH, O, SiH2, PH, S, was undertaken by calculating closed‐shell singlet molecules at three levels of theory: MP4/6‐311G(d)//MP2/6‐31G(d)+ZPE, MP4/6‐311G(d,p)//MP2/6‐31G (d,p)+ZPE, and B3LYP/6‐311+G(d,p)+ZPE. The enthalpies of 2 + 2 cycloreversion decrease on going from group 14 to group 16 elements, being substantially higher for the second row elements. Normally endothermic 2 + 2 cycloreversion is predicted to be exothermic for 1,3‐diazetidine and 1,3‐dioxtane. Strain energies of the four‐membered rings were calculated via the appropriate homodesmic reactions. The enthalpies of ring opening via the every possible one‐bond homolysis that results in the formation of the corresponding 1,4‐diradical were found by subtracting the strain energies from the central bond dissociation energies of the heterobutanes CH3CH2—CH2XH, CH3CH2—XCH3, and HXCH2—XCH3. The latter energies were determined via the enthalpies of the appropriate dehydrocondensation reactions, using C—H and X—H bond energies in CH3XH calculated at G2 level of theory. Except 1,3‐disiletane, in which ring‐opening enthalpy attains 69.7 kcal/mol, the enthalpies of the most economical ring openings do not exceed 60.7 kcal/mol. The 1,4‐diradical decomposition enthalpies found as differences between 2 + 2 cycloreversion and ring‐opening enthalpies were negative, the least exothermicity was calculated for ⋅ CH2SiH2CH2CH2. The only exception was 1,3‐disiletane, which being diradical, CH2SiH2CH2SiH2, decomposed endothermically. Since decomposition of the diradical containing two silicon atoms required extra energy, raising the enthalpy of the overall reaction to 78.9 kcal/mol, 1,3‐disiletane was predicted to be highly resisting to 2 + 2 cycloreversion. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:704–720, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20377
DFt study of the regioselectivity of addition of sulfenylchloride to ethenes
Authors: Vektariene Ausra , Vektaris Gytis , Rankin David W. H. 
Published: November 2007

AbstractThe electrophilic addition reactions of methylsulfenyl chloride to the double bonds of functionalized ethenes have been studied theoretically. Density functional theory (DFT) calculations have been applied for starting species and ethene‐based sulfonium intermediates bearing substitutes at α‐carbon atom to study geometrical parameters and electronic states of plausible intermediate forms. The quantum chemical optimizations of intermediates indicate that the episulfonium ion is the most likely methyl‐ or carboxyl‐substituted ethane‐based intermediate. However, with phenyl substituents the intermediate is more like a carbonium than an episulfonium ion. The role of sulfur appears to be that of directing the stereochemistry of the addition reaction of chloride, forming the trans product upon nucleophilic attack on the C—C bond of the episulfonium ion. The regioselectivity features of the opening of the episulfonium ion by the chloride anion depend on the LUMO and LUMO+1 of the episulfonium ion and the approaching HOMO of chlorine. The results of the theoretical investigations are in agreement with experiment. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:695–703, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20378
An efficient and green preparation of 9‐arylacridine‐1,8‐dione derivatives
Authors: Fan Xuesen , Li Yanzhen , Zhang Xinying , Qu Guirong , Wang Jianji 
Published: November 2007

Abstract9‐Arylacridine‐1,8‐dione derivatives were prepared in an ionic liquid medium in the presence of CeCl3 ċ 7H2O through an one‐pot procedure. The method presented here has the advantages of environmental benignancy, good‐to‐excellent yields, and simple operational procedure. Moreover, the solvent and catalyst can be easily recovered and reused for several runs without obvious loss of activity. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:786–790, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20410
Numerical simulation of separated flow transition and heat transfer around a two‐dimensional rib
Authors: Yanaoka Hideki , Inamura Takao , Kobayashi Reiri 
Published: November 2007

AbstractNumerical simulations of separated flow transition and heat transfer around a two‐dimensional rib mounted in a laminar boundary layer were performed. The separated shear layer becomes unstable due to the Kelvin–Helmholtz instability and generates a two‐dimensional vortex. This vortex becomes three‐dimensional and collapses in the downstream part of the separation bubble. As a result, transition from laminar to turbulent flow occurs in the separated shear layer. Streamwise vortices exist downstream of the reattachment flow region. The low‐frequency flapping motion and transition of the separated shear layer are influenced by three‐dimensional dynamics upstream of the separation bubble. Large‐scale vortices around the reattachment flow region have substantial effects on heat transfer. Downstream of the reattachment point, the surface friction coefficient and Nusselt number are different from their profiles in the laminar boundary layer and approach the distributions seen in the turbulent boundary layer. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(8): 513–528, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20177
Diagnostic technique for degradation of engineering materials by measurement of thermophysical properties
Authors: Kato Kazunori , Takahashi Ichiro 
Published: November 2007

AbstractThe thermal conductivity of the surface layer of engineering materials changes in the early stages of material degradation due to the appearance of micro‐cracks. A new method for evaluating and assessing the degree of degradation of a material using this change is proposed herein. The influence of the micro‐cracked layer on the temperature response as measured by a thermophysical handy tester was theoretically examined. By defining a thermal degradation parameter, the amount of degradation of various materials was evaluated. In order to verify this theory, fatigue tests using metallic materials were conducted. Comparisons before and after the fatigue tests were then made to establish the correlation between the density of micro‐cracks and the decrease in thermal conductivity. As a result, it was ascertained that a thermal degradation parameter can easily be estimated from a temperature response curve obtained using the tester. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(8): 501–512, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20178
An effect of scraper shapes on detachment of solid adhered to cooling surface for formation of clathrate hydrate slurry
Authors: Daitoku Tadafumi , Utaka Yoshio 
Published: November 2007

AbstractIn air‐conditioning systems, it is desirable that the liquid– solid phase change temperature of a cool energy storage material is approximately 10°C from the perspective of improving the coefficient of performance (COP). Moreover, a thermal storage material that forms slurry can realize large heat capacity of working fluids. Since the solid that adheres to the heat transfer surface forms a thermal resistance layer and remarkably reduces the rate of cold storage, it is important to avoid the adhesion of a thick solid layer on the surface so as to realize efficient energy storage. Considering a harvest type cooling unit, the force required for removing the solid phase from the heat transfer surface was studied. Tetra‐n‐butylammonium bromide (TBAB) clathrate hydrate was used as a cold storage material. The effect of the scraper shapes on the scraping force for detachment of the adhered solid of TBAB hydrate to the heat transfer surface was examined experimentally. The TBAB hydrate solids were categorized broadly into two kinds of solids. The scraping force of the TBAB hydrate solid on the heat transfer surface was different for the two kinds of the TBAB hydrate solids. And the scraping force of the TBAB hydrate solid formed after scraping was improved by the modifying the scraper shape. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(8): 489– 500, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20179
Heat transfer of combined forced and natural convection from horizontal cylinder to air
Authors: Kitamura Kenzo , Mototani Kazuhiro , Kimura Fumiyoshi 
Published: November 2007

AbstractExperimental investigations have been carried out for combined convective flows of air induced around uniformly heated, horizontal cylinders. Three cases of aiding, opposing, and cross flows were examined. The experiments covered the ranges of the Reynolds and modified Rayleigh numbers of Red=50 to 900 and Rad*=5×104 to 3×106. The flow fields around the cylinders were visualized with smoke. The results showed that separation points gradually shift from those of the forced convection to the top edge of the cylinder with increasing wall heat fluxes. The local heat transfer coefficients of the cylinders were also measured. Although the local coefficients show complex variations with the forced flow velocities and the wall heat fluxes, the overall coefficients become higher than those estimated from pure forced and natural convections throughout the cases of aiding, opposing, and cross flows. Moreover, it was confirmed that the overall Nusselt numbers as well as the separation points can be predicted with the non‐dimensional parameter (Grd*/NudRed2). © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(8): 474–488, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20180
El Niño—Southern Oscillation influences on soybean yields in eastern Paraguay
Authors: Fraisse Clyde W. , Cabrera Victor E. , Breuer Norman E. , Baez Julian , Quispe Jaime , Matos Edwards 
Published: November 2007

AbstractSoybean (Glycine max. L. Merrill) production in Paraguay has increased dramatically during the last decade and the country is now the fourth largest soybean exporter in the world, producing about 3% of the world's soybean production. This paper explored associations between soybean yield in eastern Paraguay and the El Niño Southern Oscillation (ENSO) phases. Historical soybean yield data from official government sources were detrended to remove the effects of technological advances, and yield residuals were computed. In addition, differences in mean precipitation among ENSO phases were investigated under the context of crop development phases. The CSM‐CROPGRO soybean model was used to simulate soybean development for two locations representing the most important soybean producing areas in Paraguay. Influences of ENSO phases on mean precipitation during planting and blooming, blooming and seed podding, and from young pods to physiological maturity were explored through tests of differences in the central tendency. Relative yield residuals during El Niño years were positive six out of seven events and varied from − 9.4 to + 24.2% for the 1991/1992 and 2002/2003 cropping seasons, respectively. During La Niña years, calculated residuals were negative for three out of four events and varied from − 37.9 to + 1.5% for the 2005/2006 and 1988/1989 cropping seasons, respectively. Analysis of precipitation records showed significantly lower precipitation levels between planting and blooming during La Niña years than during El Niño years. Differences in mean precipitation during blooming and beginning of seed formation were found to be not significant. Mean precipitation between seed podding and crop maturity was found to be significantly lower during La Niña years than during El Niño years in one of the locations studied. Copyright © 2007 Royal Meteorological Society
Sustainability of the landscape of a UNESCO World Heritage site in the Lake Geneva region (Switzerland) in a greenhouse climate
Authors: Beniston Martin 
Published: November 2007

AbstractThis paper poses the question as to whether the vineyards of the Lavaux region in the eastern part of Lake Geneva, Switzerland, will be able to maintain in a future greenhouse climate the same ‘cultural landscape’ as presently. It is indeed this landscape which has recently been placed on the list of UNESCO World Heritage sites, but whether it will remain as it has since the 13th century is an open question. The projected shifts in temperature and moisture patterns from current to future climate suggest that the grape varieties cultivated in the Lavaux region are likely to be subject to increasing heat and drought stress. As a result, the grape varieties that are currently cultivated in the region may no longer be sustainable; however, the visual aspect of the vineyards could be maintained if other grape varieties were to be planted, for example those that are endemic to warmer and drier Mediterranean‐type climates. The scenery of the region would thus remain close to what it is today, even though the wine produced from other types of grape would certainly be different from those for which the Lavaux has become famous over the centuries. Copyright © 2007 Royal Meteorological Society
Effect of cell density on the rate of glycosaminoglycan accumulation by disc and cartilage cells in vitro
Authors: Kobayashi Shigeru , Meir Adam , Urban Jill 
Published: November 2007

AbstractAggrecan concentration falls markedly during cartilage and disc degeneration with unfortunate biomechanical and physiological consequences. There is thus now an increasing interest in developing biological methods for its replacement. One approach is to stimulate aggrecan and hence glycosaminoglycan (GAG) production by resident cells through growth factor or genetic engineering. Another approach is to implant autologous cells into the cartilage or disc to enhance GAG production. In both instances GAG accumulation depends both on the number of active cells in the cartilage or disc and the rate of aggrecan synthesis per cell. Here we examine how cell density influences the rate of glycosaminoglycan accumulation in a three‐dimensional cell culture system. In the results, at cell densities found in vivo (standard condition) in the articular cartilage and the disc nucleus viz. 4 million cells/ml and at 21% oxygen the concentration of GAG in the bead reached 520.9±62.4 μg/ml and 649.0±40.1 μg/ml, respectively, in 5 days. These concentrations could be increased to 2‐4‐fold by raising cell density to 25 million cells/ml. However, rates of GAG production per cell decreased by 50‐60%. These results showed that rate of accumulation of glycosaminoglycan in this culture system in vitro is slow and is limited both by the rate of production of GAG per cell and by the cell density which can be maintained in a viable state. Although GAG production can be increased somewhat by use of higher cell densities, the consequent fall in concentration of oxygen and other nutrients in the center of three‐dimensional constructs slows metabolism and leads to apoptosis and cell death, which again limits the rate that the cells can produce matrix. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:493–503, 2008
Atom‐Transfer Radical Copolymerization of Furfuryl Methacrylate (FMA) and Methyl Methacrylate (MMA): A Thermally‐Amendable Copolymer
Authors: Kavitha Amalin A. , Singha Nikhil K. 
Published: November 2007

AbstractPolymers of furfuryl methacrylate (FMA) are interesting materials because of the presence of the furfuryl group as the reactive diene functionality in the pendent group. Copolymers of FMA and MMA were prepared using atom‐transfer radical polymerization (ATRP) catalyzed by CuCl, in combination with HMTETA as a ligand at 90 °C. It was very difficult to prepare by conventional radical polymerization because of several side reactions involving the reactive diene group. The copolymer composition was calculated using 1H NMR studies. The reactivity ratios of FMA and MMA (r1 and r2) were determined using the Finemann‐Ross and Kelen‐Tudos linearization methods. The reactivity ratios obtained were r1 = 1.56 and r2 = 0.56. Diels‐Alder chemistry was carried out using the reactive diene of the copolymers and a maleimide as the dienophile. Interestingly, the resultant material was observed to be thermo‐reversible as evidenced by FT‐IR spectroscopy and DSC studies.magnified image
Incorporation of Multi‐Walled Carbon Nanotubes into Biodegradable Telechelic Prepolymers
Authors: Song Wenhui , Zheng Zhen , Lu Haoxiang , Wang Xinling 
Published: November 2007

AbstractBiodegradable lactic‐acid‐based telechelic prepolymers incorporating CNTs were prepared. The products were characterized by FTIR, TGA, DSC, POM, 1H and 13C NMR, TEM, and FESEM. The results indicated that hydroxy‐terminated telechelic prepolymers were obtained. According to the TGA curves, the initial thermal decomposition temperatures of the prepolymers incorporating carboxylic CNTs were higher than those of the pure prepolymers. Amorphous and crystalline prepolymers incorporating CNTs were obtained, while the spherocrystal morphologies were not changed by the addition of the CNTs. The carboxylic CNTs were coated with PLA polymers after polymerization and well dispersed in the prepolymer matrix.magnified image
A Process for Polymerizing Vinyl Phosphonic Acid with C6F13I Perfluoroalkyl Iodide Chain‐Transfer Agent
Authors: David Ghislain , Boyer Cyrille , Tayouo Russell , Seabrook Shane , Ameduri Bruno , Boutevin Bernard , Woodward Gary , Destarac Mathias 
Published: November 2007

AbstractThe synthesis of oligomeric VPA structures via the CTA perfluorohexyl iodide has been investigated. NMR and MALDI‐TOF MS analysis showed that the structures were produced exclusively by radical‐transfer reactions. The oligomers had a molecular weight above 2 000 g · mol−1 and exhibited intra‐ and intermolecular anhydrous bonding. The investigation showed that the reaction is not a living (controlled) system, but follows conventional radical telomerization. The value for the transfer constant for C6F13I to VPA was found to be 3.4 at 70 °C and 4.3 at 80 °C. This high value may be partially explained by a low k/kt ratio, which suggests a low kp. The oligomeric structures showed a relatively high resistance to thermal degradation.magnified image
Probing the Contraction and Association of Polystyrene Chains in Semidilute Solution by Non‐Radiative Energy Transfer
Authors: Tao Fangfang , Wang Xiaoliang , Che Bo , Zhou Dongshan , Chen Wei , Xue Gi , Zou Dawei , Tie Zuoxiu 
Published: November 2007

AbstractThe interchain contraction and association of polystyrene in semidilute solution near the Θ temperature are studies using NET. The results reveal that during a drop of temperature, polystyrene chains pass through different states: a smooth change of conformation at temperatures above the Θ temperature, an accelerated contraction and association, aggregation of polymer chains, and then further continuous contraction below the Θ temperature. A pronounced hysteresis is observed during repeated heating. A viscosity study of the same solution was compared with the NET results. It indicates that NET can effectively be used to study conformational changes like contraction and association of polymer chains in a semidilute solution.magnified image
Isolated facial myokymia as a presenting feature of pontine neurocysticercosis
Authors: Bhatia Rohit , Desai Soaham , Garg Ajay , Padma Madakasira V. , Prasad Kameshwar , Tripathi Manjari 
Published: November 2007

AbstractA 45‐year‐old healthy man presented with 2 weeks history of continuous rippling and quivering movements of his right side of face and neck suggestive of myokymia. MRI scan of the head revealed neurocysticercus in the pons. Treatment with steroids and carbamezapine produced a significant benefit. This is the first report of pontine neurocysticercosis presenting as an isolated facial myokymia. © 2007 Movement Disorder Society
Factors predicting response to dopaminergic treatment for resting tremor of Parkinson's disease
Authors: Sung Young H. , Chung Sun J. , Kim Sung R. , Lee Myoung C. 
Published: November 2007

AbstractWe aimed to evaluate the clinical factors predicting response to dopaminergic treatment for resting tremor in patients with Parkinson's disease (PD). Eighty‐five PD patients with prominent resting tremor, defined as tremors of score greater than 3 in at least one limb on the Unified Parkinson's Disease Rating Scale (UPDRS), were divided into those responsive or nonresponsive to dopaminergic treatment. Responsiveness was defined as a reduction of at least two points for more than 3 months in the UPDRS tremor score. Of the 85 patients, 36 (42.4%) were responsive and 49 (57.6%) were nonresponsive to dopaminergic treatment. Initial UPDRS III score (P = 0.015) and Hoehn and Yahr stage (P = 0.010) were each significantly higher in the RG than in the NRG. UPDRS subscores for rigidity (P = 0.012), bradykinesia (P = 0.021) and postural impairment (P = 0.018) also correlated with responsiveness to dopaminergic treatment. Resting tremor in PD patients was more responsive to dopaminergic treatment when accompanied by moderate degrees of bradykinesia and rigidity than in patients without other prominent parkinsonian features. © 2007 Movement Disorder Society
Transcranial sonography findings in welding‐related Parkinsonism in comparison to Parkinson's disease
Authors: Walter Uwe , Dressler Dirk , Lindemann Christian , Slachevsky Andrea , Miranda Marcelo 
Published: November 2007

AbstractThe pathogenetic relationship of welding‐related Parkinsonism (WP) and idiopathic Parkinson's disease (PD) is a matter of debate. In the present study, we compared transcranial sonography (TCS) findings in patients with WP and PD. Two male patients with WP, who had developed levodopa‐resistant akinetic‐rigid Parkinsonism without ongoing progression after having worked as welders for many years in Chilean mines in confined spaces without adequate ventilation, and three age‐matched male patients with clinically definite akinetic‐rigid PD were studied with TCS in a random order by two investigators blind to clinical diagnoses. In both WP patients, normal echogenicity of substantia nigra was found whereas all PD patients exhibited marked substantia nigra hyperechogenicity, previously reported as a characteristic TCS finding in idiopathic PD. In contrast, lenticular nucleus was hyperechogenic in both WP patients but only in one of the PD patients. TCS findings suggest a different pathophysiology of Parkinsonism in WP and PD patients. © 2007 Movement Disorder Society