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排序方式: 共有236条查询结果,搜索用时 15 毫秒
91.
Calvert CR Belshaw L Duffy MJ Kelly O King RB Smyth AG Kelly TJ Costello JT Timson DJ Bryan WA Kierspel T Rice P Turcu IC Cacho CM Springate E Williams ID Greenwood JB 《Physical chemistry chemical physics : PCCP》2012,14(18):6289-6297
Laser induced acoustic desorption (LIAD) has been used for the first time to study the parent ion production and fragmentation mechanisms of a biological molecule in an intense femtosecond (fs) laser field. The photoacoustic shock wave generated in the analyte substrate (thin Ta foil) has been simulated using the hydrodynamic HYADES code, and the full LIAD process has been experimentally characterised as a function of the desorption UV-laser pulse parameters. Observed neutral plumes of densities >10(9) cm(-3) which are free from solvent or matrix contamination demonstrate the suitability and potential of the source for studying ultrafast dynamics in the gas phase using fs laser pulses. Results obtained with phenylalanine show that through manipulation of fundamental femtosecond laser parameters (such as pulse length, intensity and wavelength), energy deposition within the molecule can be controlled to allow enhancement of parent ion production or generation of characteristic fragmentation patterns. In particular by reducing the pulse length to a timescale equivalent to the fastest vibrational periods in the molecule, we demonstrate how fragmentation of the molecule can be minimised whilst maintaining a high ionisation efficiency. 相似文献
92.
Osten KM Yu I Duffy IR Lagaditis PO Yu JC Wallis CJ Mehrkhodavandi P 《Dalton transactions (Cambridge, England : 2003)》2012,41(26):8123-8134
Functionalized diaminophenols, H(N(R1R2)N(R3)O), were investigated as ligands for indium catalysts in the ring-opening polymerization of racemic lactide. Precursor complexes (N(Me2)N(Me)O)InCl(2) (1), (N(Pr2)NO)InCl(2) (2), and (N(Mes)NO)InCl(2) (3) were synthesized and fully characterized by (1)H and (13)C NMR spectroscopy, elemental analysis, and single-crystal X-ray crystallography. Complexes 1 and 2 were used to synthesize alkoxy-bridged complexes [(N(Me2)N(Me)O)InCl](2)(μ-Cl)(μ-OEt) (4) and [(N(Pr2)NO)InCl](2)(μ-Cl)(μ-OEt) (5). These complexes catalysed the polymerization of racemic lactide at different rates, with complex 5 being substantially more active than complex 4. The dissociation behaviour of these catalysts in the presence of lactide was also studied and used to make comparisons with previously reported catalyst systems. 相似文献
93.
The approach to the critical solution in leading order coating and rimming flow of a thin fluid film on a uniformly rotating horizontal cylinder is investigated. In particular, it is shown that the weight of the leading order “full film” solution approaches its critical maximum value with logarithmically infinite slope as the volume flux approaches its critical value. 相似文献
94.
L. Benevides A. Romanyukha F. Hull M. Duffy S. Voss M. Moscovitch 《Radiation measurements》2010,45(3-6):523-526
We are reporting the results of an investigation designed to determine the magnitude of the light induced fading associated with the OSL response of Al2O3:C. Unlike previous studies where bare, radiation sensitive OSL elements were exposed directly to light, most of the experiments described here were conducted using sealed commercially available OSL dosimeters. During light exposure the OSL sensitive elements were kept inside a standard commercially available plastic badge. A commercial OSL system was used for these experiments in an attempt to simulate typical field use conditions. Both light induced signal and light induced fading were considered, however no measurable light induced signal could be identified. Light induced fading effects, however, were significant, up to 55% loss of OSL signal following daylight exposure of 45 days. The possibility that dose information may be easily erased, intentionally or accidentally, could impose significant restrictions on the ability of the US Navy to defend, if needed, the reported personnel dose levels. 相似文献
95.
Ryan A. Hemming Megan Bell Liam J. Duffy Jonathan Bristow John D. Wallis Steven M. Allin Philip C. Bulman Page 《Tetrahedron》2019,75(1):121-127
A new, versatile and highly stereoselective approach for the synthesis of non-racemic 3-substituted isoindolin-1-ones is described from a readily available chiral template. The potential of this new protocol is demonstrated through the synthesis of an enantiomerically enriched 3-alkyl N-H isoindolin-1-one target with an e.e. of 98%. 相似文献
96.
The basicity of the oxidic groups AlO45?, SiO44?, PO43?, SO42?, ClO4?, can be regarded in terms of electron donor power and expressed numerically as the optical basicity, λ. The λ value depends upon the oxidation number of the central atom and its basicity moderating parameter, γ. The results of (modified) self-consistent field CNDO calculations, presented and discussed in this paper, indicate the simple relationship that the optical basicity value is directly proportional to the negative charge borne by the oxygen atoms of the oxyanion. It is apparent that the basicity moderating parameter is a measure of the ability of the central atom to withdraw charge from the oxygen atoms. The results also indicate that the electron density at the “surface” of the oxyanion originates not only from the oxygens but also from the central atom, this effect increasing with decreasing oxidation number of the central atom. 相似文献
97.
Single-crystal X-ray structures of four nickel dithiocarbamate complexes, the homoleptic mixed-organic bis-dithiocarbamates Ni[S2CN(isopropyl)(benzyl)]2, Ni[S2CN(ethyl)(n-butyl)]2, and Ni[S2CN(phenyl)(benzyl)]2, as well as the heteroleptic mixed-ligand complex NiCl[P(phenyl)3][(S2CN(phenyl)(benzyl)], were determined. A slightly distorted square-planar nickel coordination environment was observed for all four complexes. The organic residues adopt conformations to minimize steric interactions. Steric effects also may determine puckering, if any, about the nickel and nitrogen atoms, both of which are planar or nearly so. A trans-influence affects the Ni-S bond distances. Nitrogens interact with the CS2 carbons with a bond order near two; the other substituents on nitrogen display transoid conformations. There are no strong intermolecular interactions, consistent with prior observations of the volatility of nickel dithiocarbamate complexes. A preliminary thermolysis study of the homoleptic species results in production of 1?:?1 nickel sulfide phases, indicating the potential utility of these species as “single-source” precursors. 相似文献
98.
Michael I. Bruce Christopher Dean D.Neil Duffy Mark G. Humphrey George A. Koutsantonis 《Journal of organometallic chemistry》1985,295(3):c40-c44
Addition of arenediazonium or tropylium salts to Ru(C2Ph)(L)2(η-C5H5) (L2 = (PPh3)2 or DPPE) gives the corresponding cationic aryldiazovinylidene and cycloheptatrienylvinylidene complexes, respectively; the X-ray structures of the title complexes confirm the presence of the new ligands. The RuC and CC distances are 1.823(9) and 1.34(1) Å for the aryldiazo complex, and 1.848(9) and 1.32(1) Å for the cycloheptatrienyl derivative. 相似文献
99.
100.
A simple high-performance liquid chromatography assay using fluorescence detection for the major metabolite of the gastric prokinetic drug cisapride, norcisapride, is presented. Analysis is performed using an Alltech Platinum EPS C8 column with a mobile phase made up of methanol and 0.02M sodium dihygrogen phosphate (45:55, v/v) containing triethylamine (1 g/L). Complete resolution is achieved among norcisapride, the internal standard (metoclopramide), and endogenous urinary components. The assay is linear over the range 50-2000 ng/mL with a mean recovery of 71.2% across the analytical range following solvent extraction with toluene-isoamyl alcohol (95:5, v/v). Intraday coefficients of variation (precision) determined at 200 and 1000 ng/mL are 6.0 and 9.8%, respectively, and interday coefficients of variation are 8.8 and 6.6%, respectively. Intra- and interassay accuracy (as mean relative error) determined at the same concentrations is within 10% in all cases. An analysis of urine samples from a healthy volunteer following the administration of a single 10-mg oral dose of cisapride is shown. 相似文献