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Selected AbstractsTheoretical studies of mechanisms of cycloaddition reaction between difluoromethylene carbene and acetoneINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 2 2007Xiu Hui Lu Abstract Mechanisms of the cycloaddition reaction between singlet difluoromethylene carbene and acetone have been investigated with the second-order Møller,Plesset (MP2)/6-31G* method, including geometry optimization and vibrational analysis. Energies for the involved stationary points on the potential energy surface (PES) are corrected by zero-point energy (ZPE) and CCSD(T)/6-31G* single-point calculations. From the PES obtained with the CCSD(T)//MP2/6-31G* method for the cycloaddition reaction between singlet difluoromethylene carbene and acetone, it can be predicted that path B of reactions 2 and 3 should be two competitive leading channels of the cycloaddition reaction between difluoromethylene carbene and acetone. The former consists of two steps: (i) the two reactants first form a four-membered ring intermediate, INT2, which is a barrier-free exothermic reaction of 97.8 kJ/mol; (ii) the intermediate INT2 isomerizes to a four-membered product P2b via a transition state TS2b with an energy barrier of 24.9 kJ/mol, which results from the methyl group transfer. The latter proceeds in three steps: (i) the two reactants first form an intermediate, INT1c, through a barrier-free exothermic reaction of 199.4 kJ/mol; (ii) the intermediate INT1c further reacts with acetone to form a polycyclic intermediate, INT3, which is also a barrier-free exothermic reaction of 27.4 kJ/mol; and (iii) INT3 isomerizes to a polycyclic product P3 via a transition state TS3 with an energy barrier of 25.8 kJ/mol. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source] Mobile technology in the village: ICTs, culture, and social logistics in IndiaTHE JOURNAL OF THE ROYAL ANTHROPOLOGICAL INSTITUTE, Issue 3 2008Sirpa Tenhunen Mobile technology is currently emerging as the first extensive form of electronic communication system in many regions of Africa and Asia. This article analyses the appropriation of mobile phones in rural India by exploring what new social alternatives mobile phones enable and how these new social constellations relate to culture and cultural change. The ethnographic description relates phone usage to other communication patterns and ongoing processes of transformation. The article shows how the appropriation of phones draws from the local cultural and social context, but also that phones facilitate new patterns that show great similarity with social processes in other places where phones have been introduced as the first form of communication technology, such as the increased multiplicity of social contacts and the greater efficiency of market relationships. I argue that mobile technology amplifies ongoing processes of cultural change but does so selectively, so that it brings about the homogenization of ,social logistics'. Résumé Dans de nombreuses régions d'Asie et d'Afrique, la technologie mobile apparaît aujourd'hui comme la première forme étendue de communications électroniques. L'auteur analyse ici l'appropriation de la téléphonie mobile en Inde, en explorant les nouvelles alternatives sociales que le téléphone portable rend possibles et les liens entre ces nouvelles constellations sociales, d'une part, et d'autre part la culture et le changement culturel. La description ethnographique fait le lien entre l'utilisation du téléphone et les autres modes de communication et avec les processus actuels de transformation. L'article montre comment l'appropriation du téléphone s'inscrit dans le contexte culturel et social local, tout en mettant en lumière la similarité entre la façon dont le téléphone facilite de nouveaux schémas de communication et les processus sociaux qui se déploient dans d'autres lieux où la téléphonie a été introduite comme première forme de technologie de communication : multiplication des contacts sociaux, efficacité accrue des relations de marché. L'auteur affirme que la technologie mobile amplifie les processus actuels de changement culturel, mais quelle le fait de manière sélective, en induisant ainsi une homogénéisation de la « logistique sociale ». [source] Crystallization and preliminary X-ray diffraction studies of a fungal hydrolase from Ophiostoma novo-ulmiACTA CRYSTALLOGRAPHICA SECTION D, Issue 10 2004Michail N. Isupov Dutch elm disease fungus Ophiostoma novo-ulmi contains a hydrolase activity which catalyses the resolution of racemic ethyl naproxen to the corresponding acid. The recombinant enzyme has been crystallized by the vapour-diffusion method in two crystal forms. The crystals of the first form belong to space group P21212, with unit-cell parameters a = 115.9, b = 174.4, c = 62.1,Å. The enzyme also crystallizes in space group P21212, with unit-cell parameters a = 72.9, b = 212.7, c = 61.7,Å. Synchrotron data have been collected for both crystal forms to 2.6 and 2.3,Å, respectively. A molecular-replacement solution has been found using a remote starting model of a bacterial esterase (23% sequence identity) for both crystal forms. Multicrystal averaging has resulted in interpretable electron-density maps. [source] Crystallization and preliminary X-ray analysis of a thermoalkalophilic lipase from Bacillus stearothermophilus L1ACTA CRYSTALLOGRAPHICA SECTION D, Issue 9 2001Seong-Tae Jeong A thermoalkalophilic lipase from Bacillus stearothermophilus L1 (L1 lipase) was crystallized in two different crystal forms using a low concentration of the enzyme and a calcium-exchange process. The first, needle-like, crystal form, which diffracts to about 3.5,Å, belongs to the orthorhombic space group P212121, with unit-cell parameters a = 67.84, b = 72.96, c = 104.41,Å. The second, monoclinic, crystal form, which behaves better than the first form for crystallographic analyses, belongs to the monoclinic space group C2 and has unit-cell parameters a = 119.62, b = 85.05, c = 98.36,Å, , = 99.73°. From the monoclinic crystals, a native data set and a samarium-derivative data set were collected to 2.0 and 2.3,Å resolution, respectively. The difference Patterson map between the two data sets shows strong heavy-atom peaks, indicating that the crystals are suitable for a high-resolution structure determination. [source] Crystallization and preliminary crystallographic analysis of Thermus thermophilus leucyl-tRNA synthetase and its complexes with leucine and a non-hydrolysable leucyl-adenylate analogueACTA CRYSTALLOGRAPHICA SECTION D, Issue 5 2000Anna Yaremchuk Leucyl-tRNA synthetase from Thermus thermophilus (LeuRSTT) is the first LeuRS to be crystallized. Two crystal forms of the native enzyme have been obtained using the hanging-drop vapour-diffusion method with ammonium sulfate as a precipitant. Crystals of the first form belong to space group I422 and have unit-cell parameters a = b = 312.4, c = 100.4,Å. They diffract anisotropically to 3.5,Å resolution in the c -axis direction and to only 6,Å resolution in the perpendicular direction. Crystals of the second form, which can be obtained native or with leucine or a leucyl-adenylate analogue bound, belong to space group C2221 and have unit-cell parameters a = 102.4, b = 154.1, c = 174.3,Å. They diffract to 1.9,Å resolution and contain one monomer in the asymmetric unit. Selenomethionated LeuRSTT has been produced and crystals of the second form suitable for MAD analysis have been grown. [source] | ||||||||||