916 research outputs found

    The interactions between the sterically demanding trimesitylphosphine oxide and trimesityphosphine with scandium and selected lanthanide ions

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    The reactions between lanthanide nitrates, Ln(NO3)3 and scandium and lanthanide trifluoromethane sulfonates, Ln(Tf)3 with trimesitylphosphine oxide, Mes3PO show that coordination to the metal ions does not lead to crystalline complexes. Investigation of the reactions by 31-P NMR spectroscopy shows that weak complexes are formed in solution. The crystal structures of Mes3PO·0.5CH3CN (1) and [Mes3PO]3H3O·2CH3CN·Tf (2), formed in the reaction between ScTf3 and Mes3PO, are reported. Trimesitylphosphine, Mes3P, is protonated by scandium and lanthanide trifluoromethane sulfonates and lanthanide nitrates in CD3CN and the structure of [Mes3PH]Cl·HCl·2H2O (3) is reported

    Total syntheses of conformationally-locked difluorinated pentopyranose analogues and a pentopyranosyl phosphate mimetic

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    Trifluoroethanol has been elaborated, via a telescoped sequence involving a metalated difluoroenol, a difluoroallylic alcohol, [2,3]-Wittig rearrangement, and ultimately an RCM reaction and requiring minimal intermediate purification, to a number of cyclooctenone intermediates. Epoxidation of these intermediates followed by transannular ring opening or dihydroxylation, then transannular hemiacetalization delivers novel bicyclic analogues of pentopyranoses, which were elaborated (in one case) to an analogue of a glycosyl phosphate

    The Constraints and Spectra of a Deformed Quantum Mechanics

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    We examine a deformed quantum mechanics in which the commutator between coordinates and momenta is a function of momenta. The Jacobi identity constraint on a two-parameter class of such modified commutation relations (MCR's) shows that they encode an intrinsic maximum momentum; a sub-class of which also imply a minimum position uncertainty. Maximum momentum causes the bound state spectrum of the one-dimensional harmonic oscillator to terminate at finite energy, whereby classical characteristics are observed for the studied cases. We then use a semi-classical analysis to discuss general concave potentials in one dimension and isotropic power-law potentials in higher dimensions. Among other conclusions, we find that in a subset of the studied MCR's, the leading order energy shifts of bound states are of opposite sign compared to those obtained using string-theory motivated MCR's, and thus these two cases are more easily distinguishable in potential experiments.Comment: 30 pages inclusive of 7 figure

    Combined experimental and computational investigations of rhodium-catalysed C-H functionalisation of pyrazoles with alkenes

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    Detailed experimental and computational studies have been carried out on the oxidative coupling of the alkenes C(2)H(3)Y (Y=CO(2)Me (a), Ph (b), C(O)Me (c)) with 3-aryl-5-R-pyrazoles (R=Me (1 a), Ph (1 b), CF(3) (1 c)) using a [Rh(MeCN)(3)Cp*][PF(6)](2)/Cu(OAc)(2)⋅H(2)O catalyst system. In the reaction of methyl acrylate with 1 a, up to five products (2 aa–6 aa) were formed, including the trans monovinyl product, either complexed within a novel Cu(I) dimer (2 aa) or as the free species (3 aa), and a divinyl species (6 aa); both 3 aa and 6 aa underwent cyclisation by an aza-Michael reaction to give fused heterocycles 4 aa and 5 aa, respectively. With styrene, only trans mono- and divinylation products were observed, whereas with methyl vinyl ketone, a stronger Michael acceptor, only cyclised oxidative coupling products were formed. Density functional theory calculations were performed to characterise the different migratory insertion and β-H transfer steps implicated in the reactions of 1 a with methyl acrylate and styrene. The calculations showed a clear kinetic preference for 2,1-insertion and the formation of trans vinyl products, consistent with the experimental results

    Non-adiabatic holonomic quantum computation

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    We develop a non-adiabatic generalization of holonomic quantum computation in which high-speed universal quantum gates can be realized by using non-Abelian geometric phases. We show how a set of non-adiabatic holonomic one- and two-qubit gates can be implemented by utilizing optical transitions in a generic three-level Λ\Lambda configuration. Our scheme opens up for universal holonomic quantum computation on qubits characterized by short coherence times.Comment: Some changes, journal reference adde

    Management of Germplasm Collections in Chickpea

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    Chickpea (Cicer arietinum L.) is an important pulse crop and ranks second in area and third in production among the pulses in the world.About 150 accessions were desi types and remaining 10 kabuli types. Similarly, kabuli germplasm maintained at International Centre for Agricultural Research in the Dry Areas (ICARDA) was screened for 29 traits including reaction to major biotic and abiotic stresses and promising donor sources have been identified. Collaborative efforts among different research institutes through national network should be made to evaluate chickpea germplasm systematically at several locations. To narrow down the gap between germplasm available and the germplasm utilized in the breeding programmes, it is imperative to document the germplasm providing a complete spectrum of genetic variability in the collection. Efforts should also be made towards germplasm enhancement through incorporation of genes from secondary and tertiary gene pools into a suitable genetic background. A good number of accessions conserved in various genebanks may be duplicates and efforts are required to identify and eliminate them using molecular markers.Over 13,500 accessions were evaluated for resistance to race 1 of Fusarium oxysporum f. sp. ciceri at ICRISAT resulting into identification of 160 accessions with stable resistance (Haware et al., 1992)

    Correlation induced non-Abelian quantum holonomies

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    In the context of two-particle interferometry, we construct a parallel transport condition that is based on the maximization of coincidence intensity with respect to local unitary operations on one of the subsystems. The dependence on correlation is investigated and it is found that the holonomy group is generally non-Abelian, but Abelian for uncorrelated systems. It is found that our framework contains the L\'{e}vay geometric phase [2004 {\it J. Phys. A: Math. Gen.} {\bf 37} 1821] in the case of two-qubit systems undergoing local SU(2) evolutions.Comment: Minor corrections; journal reference adde

    Impact of organizational trust on job performance : a study of land and survey department / Kuldip Singh

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    This study examines the influence of organizational trust on job performance by analyzing perceptions of 100 public employees in the Land and Survey Department. The instrument used to measure organizational trust was adopted from Institute for Public Relations (2003). Job performance was measured using an instrument developed by Borman and Motowidlo (1997). Results of the instrument’s Cronbach Alpha measurement show that the score of reliability is above .90 which indicates an acceptable level. The results indicate that organizational trust is positively correlated with job performance. These results imply that job performance may be dependent on organizational trust in the public sector. This study provides insights on the relationship between organizational trust and job performance in the public sector. The findings of this study may help public sector to enhance its organizational trust and its effect on job performance. Limitations and recommendations are also discussed
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