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31.
Ison JR Castro J Allen P Virag TM Walton JP 《The Journal of the Acoustical Society of America》2002,112(2):740-747
The effect on gap detectability of varying noise fall time (FT) and rise time (RT) of the gap boundary ramps was examined in mice using reflex modification audiometry, measuring inhibition of acoustic startle reflexes by variously shaped gaps just preceding reflex expression. In experiment 1 (n = 12) inhibition increased up to near-asymptotic values with longer FT (0, 1, 2, 3, 5, or 10 ms) and QT (quiet time, 0 to 13 ms), with a 2:1 trade-off between FT and QT. In experiment 2 (n = 24) inhibition increased for any RT above 0 ms (2, 3, 5, or 7 ms) if QT= 1 ms, but diminished with increased RT when QT = 3 or 8 ms. Enhanced detectability for subthreshold gaps by longer ramps results from their extending the apparent gap duration. The negative effect of increased RT for threshold gaps suggests the importance for gap detection of the stronger neural responses to sharp edges at the end of the gap shown previously in the mouse inferior colliculus. These effects are specific to gaps: inhibition for fixed (70-dB SPL) or varied level pulses (30 to 60 dB) was unaffected by varying the ramped edges (experiments 3 and 4, n = 9). 相似文献
32.
Walton B Najmudin Z Wei MS Marle C Kingham RJ Krushelnick K Dangor AE Clarke RJ Poulter MJ Hernandez-Gomez C Hawkes S Neely D Collier JL Danson CN Fritzler S Malka V 《Optics letters》2002,27(24):2203-2205
A short-pulse laser beat wave scheme for advanced particle accelerator applications is examined. A short, intense (3-ps, >10(18)-W cm(-2)) two-frequency laser pulse is produced by use of a modified chirped-pulse amplification scheme and is shown to produce relativistic plasma waves during interactions with low-density plasmas. The generation of plasma waves was observed by measurement of forward Raman scattering. Resonance was found to occur at an electron density many times that expected, owing to ponderomotive displacement of plasma within the focal region. 相似文献
33.
Braun T Foxon SP Perutz RN Walton PH 《Angewandte Chemie (International ed. in English)》1999,38(22):3326-3329
Rapid and regioselective activation of the C-F bond of 2,4,6-trifluoropyrimidine occurs on reaction with [Ni(cod)(2)] (cod=1,5-cyclooctadiene) in the presence of PEt(3) to give 1, which can be converted into complex 2, containing a further N(3)-metalated pyrimidin-4-one unit. The novel pyrimidin-4-one 3 is released on protonation of 2. 相似文献
34.
David A. Kort Wengan Wu Phillip E. Fanwick Richard A. Walton 《Transition Metal Chemistry》1995,20(6):625-629
35.
The diamagnetic Roussin esters Fe2(SR)2(NO)4 readily underwent exchange with thiols R′SH to yield Fe2(SR′)2(NO)4: the exchange was faster in polar, coordinating solvents where paramagnetic, mononuclear complexes of types [Fe(NO)2(solvent)2]+ and Fe(NO) 2(SR)(solvent) were formed. With the corresponding thiolate anions RS-, the esters Fe2(SR)2(NO)4 formed the mononuclear complexes [Fe(SR)2(NO)2]-, which were fully characterised by EPR spectroscopy for R = H, Me, Et, i-Pr, t-Bu and PhCH2: assignments of hyperfine couplings were confirmed by use of 15N. With Fe2(SR)2(NO)4 and a different set of thiolate anion, R′S -, in excess, thiol exchange occurred to give [Fe(SR′)2(NO)2]-. A mechanism for formation of Fe2(SR′)2(NO)4 from Fe2(SR)2(NO)4 has been proposed. The paramagnetic mononuclear complexes [Fe(SR)2(NO)2] were also readily formed from the diamagnetic clusters [Fe4S3(NO)7]- and Fe4S4(NO)4, together with [Fe(SR)3(NO)]-, and additionally from [Fe(CO)3NO]-. [Fe(SMe)2(NO)2]-. was found to be a precursor of isolable Fe2(SMe)2(NO)4, and [Fe(SH)2 (NO)2]- to be the common precursor of both Roussin′s red anion [Fe2S2(NO)4]- and Roussin's black anion [Fe4S3 (NO)7]- interconvertible by appropriate adjustment of pH. The nitrosyl groups in these complexes were freely labile, and mononitrosyliron and dinitrosyliron fragments were readily interconvertible: FE(NO) fragments were favoured by the dimethyldithiocarbamate ligand (Me2NCS 2) and Fe(NO)2 fragments by thiolate ligands, RS-, regardless of the origin of the Fe(NO)x(x = 1,2) fragment: both mono- and dinitrosyliron complexes persisted with [(i-PrO)2S2]- as ligand. Isotopic labelling showed the occurrence of rapid exchange of nitrogen between nitrosyl ligands and added nitrite in Fe(NO)(S2CNMe2)2 and [Fe(SR)2(NO)2]- 相似文献
36.
Short columns of a 4% crosslinked cation-exchange resin gave good chromatography of xanthines, including caffeine, theophylline and hypoxanthine, and related polar aromatic compounds. Elution volumes and sequences can be modified by changing pH, solvent composition and resin counter-ion. A macroporous cation-exchange resin showed exaggerated counter-ion effects. A method is described for determining caffeine and theophylline in blood serum, using the 4% crosslinked resin with aqueous sodium phosphate eluent of pH 7.5; the temperature was 65 degrees. Detection limits are 10 ng and less. 相似文献
37.
An accelerated, more stable generalization of Newton's method for finding matrix pth roots is developed in a form suitable for finding the positive definite pth root of a positive definite matrix. Numerical examples are given and compared with the corresponding Newton iterates. 相似文献
38.
Lev?B.?Levitin Tom?ToffoliEmail author Zac?Walton 《International Journal of Theoretical Physics》2005,44(2):219-228
We consider a fixed quantum measurement performed over n identical copies of quantum states. Using a rigorous notion of distinguishability based on Shannon’s 12th theorem, we show that in the case of a single qubit, the number of distinguishable states is
, where (α1,α2) is the angle interval from which the states are chosen. In the general case of an N-dimensional Hilbert space and an area Ω of the domain on the unit sphere from which the states are chosen, the number of distinguishable states is
. The optimal distribution is uniform over the domain in Cartesian coordinates. 相似文献
39.
Brown EJ Whitwood AC Walton PH Duhme-Klair AK 《Dalton transactions (Cambridge, England : 2003)》2004,(16):2458-2462
The butoxy- and methoxy-derivatives (HLc, and HLb, respectively) of 1-[(ethoxycarbonyl)methyl]-3-hydroxy-2-(1H)-pyridinone, HLa, were synthesized by transesterification and the mononuclear complexes [MoO2(L(a-c))2] were obtained by the reaction of the ligands with molybdenyl acetylacetonate. The three complexes were fully characterized by (1)H and (13)C NMR spectroscopy, mass spectrometry and elemental analyses. A variable temperature NMR study showed that the N-substituents do not have a significant influence on the racemisation process of the complexes. The comparison of the crystal structure of [MoO2(Lb)2] with [MoO2(La)2] confirmed that an additional methylene group does not affect the immediate coordination environment of the molybdenum centre. The methoxy-derivative HLb was also found to produce a dinuclear complex of composition [(MoO2(Lb)O)2], the structure of which was determined by X-ray diffraction. 相似文献
40.
We obtain an explicit generalization, within Fokker-Planck dynamics, of Einstein's relation between drag, diffusion, and the equilibrium distribution for a spatially homogeneous system, considering both the transverse and longitudinal diffusion for dimension n>1. We provide a complete characterization of the equilibrium distribution in terms of the drag and diffusion transport coefficients. We apply this analysis to charm quark dynamics in a thermal quark-gluon plasma for the case of collisional equilibration. 相似文献