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11.
Pendlebury SR Barroso M Cowan AJ Sivula K Tang J Grätzel M Klug D Durrant JR 《Chemical communications (Cambridge, England)》2011,47(2):716-718
Transient absorption spectroscopy on the μs-s time scale is used to monitor the yield and decay dynamics of photogenerated holes in nanocrystalline hematite photoanodes. In the absence of a positive applied bias, these holes are observed to undergo rapid electron-hole recombination. The application of a positive bias results in the generation of long-lived (3 ± 1 s lifetime) photoholes. 相似文献
12.
G.L. Greene N.F. Ramsey W. Mampe J.M. Pendlebury K. Smith W.D. Dress P.D. Miller Paul Perrin 《Physics letters. [Part B]》1977,71(2):297-300
The magnetic moment of the neutron has been measured with a factor of one hundred improvement in accuracy. In terms of the Bohr magneton and proton magnetic moment, respectively, the result is μn/μB= ?1.041 875 79 (26) × 10?3, μn/μp = ?0.684 979 45 (17). 相似文献
13.
怀孕期头发中一些元素含量的变化趋势 总被引:5,自引:1,他引:4
用同步辐射激发X射线荧光分析,对11个产妇怀孕期间头发内一些元素含量的变化趋势进行了测量,在各自对比的基础上,得到了一些结果。 相似文献
14.
Baker CA Doyle DD Geltenbort P Green K van der Grinten MG Harris PG Iaydjiev P Ivanov SN May DJ Pendlebury JM Richardson JD Shiers D Smith KF 《Physical review letters》2006,97(13):131801
An experimental search for an electric dipole moment (EDM) of the neutron has been carried out at the Institut Laue-Langevin, Grenoble. Spurious signals from magnetic-field fluctuations were reduced to insignificance by the use of a cohabiting atomic-mercury magnetometer. Systematic uncertainties, including geometric-phase-induced false EDMs, have been carefully studied. The results may be interpreted as an upper limit on the neutron EDM of |d(n)|< 2.9 x 10(-26)e cm (90% C.L.). 相似文献
15.
Cowan AJ Barnett CJ Pendlebury SR Barroso M Sivula K Grätzel M Durrant JR Klug DR 《Journal of the American Chemical Society》2011,133(26):10134-10140
Competition between charge recombination and the forward reactions required for water splitting limits the efficiency of metal-oxide photocatalysts. A key requirement for the photochemical oxidation of water on both nanostructured α-Fe(2)O(3) and TiO(2) is the generation of photoholes with lifetimes on the order of milliseconds to seconds. Here we use transient absorption spectroscopy to directly probe the long-lived holes on both nc-TiO(2) and α-Fe(2)O(3) in complete PEC cells, and we investigate the factors controlling this slow hole decay, which can be described as the rate-limiting step in water oxidation. In both cases this rate-limiting step is tentatively assigned to the hole transfer from the metal oxide to a surface-bound water species. We demonstrate that one reason for the slow hole transfer on α-Fe(2)O(3) is the presence of a significant thermal barrier, the magnitude of which is found to be independent of the applied bias at the potentials examined. This is in contrast to nanocrystalline nc-TiO(2), where no distinct thermal barrier to hole transfer is observed. 相似文献
16.
L. Vincent S. N. Connolly F. Dolan P. H. Willcocks S. A. A. Jayaweera R. Pendlebury 《Journal of Thermal Analysis and Calorimetry》2006,86(1):147-154
The essential work of fracture
(EWF) method has been used to study the relationship between molecular structure
and thin film fracture toughness for three ductile polyesters at ambient temperature.
The fracture toughness of PPT is of particular interest. Successful fracture
characterisation of thin film polyesters has been achieved by the EWF method
using double edge notched tension (DENT) specimens. The specific essential
work of fracture, w
e,
for polyethylene terephthalate (PET), polypropylene terephthalate (PPT) and
polybutylene terephthalate (PBT) films is found to be 35.54±2.56, 41.03±3.23
and 31.34±8.60 kJ m–2, respectively.
Differential scanning calorimetry (DSC) has been employed to investigate the
crystallinity of the polymers concerned and the effect of this on their EWF
values. 相似文献
17.
We discuss the interaction of Ultra-Cold and Cold Neutrons with superfluid 4He and show that this interaction has all the characteristics which are necessary for the achievement of extremely high densities of UCN. 相似文献
18.
Barroso M Cowan AJ Pendlebury SR Grätzel M Klug DR Durrant JR 《Journal of the American Chemical Society》2011,133(38):14868-14871
Transient absorption spectroscopy was used to probe the dynamics of photogenerated charge carriers in α-Fe(2)O(3)/CoO(x) nanocomposite photoelectrodes for water splitting. The addition of cobalt-based electrocatalysts was observed to increase the lifetime of photogenerated holes in the photoelectrode by more than 3 orders of magnitude without the application of electrical bias. We therefore propose that the enhanced photoelectrochemical activity of the composite electrode for water photooxidation results, at least in part, from reduced recombination losses because of the formation of a Schottky-type heterojunction. 相似文献
19.
Correlating magnetic resonance imaging markers of axonal injury and demyelination in motor impairment secondary to stroke and multiple sclerosis 总被引:2,自引:0,他引:2
The primary pathological mechanisms in stroke and multiple sclerosis (MS) are very different but in both diseases, impairment may arise from a final common pathway of axonal damage. We aimed to examine the relationship between motor impairment, magnetisation transfer ratio (MTR) (an index of demyelination), and N-acetyl aspartate (NAA) loss (an index of axonal injury) localised to the descending motor pathways in stroke and MS. Twelve patients between 1 and 10 months after first ischaemic stroke causing a motor deficit and 12 patients with stable MS with asymmetric motor deficit were examined. T(2)-weighted imaging of the brain together with MTR and proton (voxel 1.5x2x2 cm(3)) MRS localised to the posterior limb of the internal capsule were performed and correlated to a composite motor deficit score. MTR and NAA in the internal capsule were reduced in both stroke and MS patients compared to controls. NAA loss correlated with motor deficit score in both stroke and MS (p<0.001 and p = 0.04, respectively). Correlations were seen between MTR and motor deficit (p<0.001) MTR and NAA loss (p <0.001) in stroke patients but not in MS patients. Axonal injury in the descending motor tracts would appear to be an important determinant of motor impairment in both stroke and MS. In stroke, MTR measures of demyelination are closely related to axonal damage and thus also correlate with motor deficit. However in MS, MTR measures of demyelination do not correlate with NAA loss or motor deficit suggesting that demyelination and gliosis may occur independently of axonal damage and are less closely linked with functional impairment. 相似文献
20.
The kinetics of the reversible reaction have been studied spectrophotometrically in acid solution under conditions in which both the forward and reverse reactions go to virtual completionand in which the reaction comes to a practical equlibrium. The rates of theforward (Rf) and reverse (Rr) reactions are given by where f, g, h, u, and v have the values (4 ± 1) × 10?5 mole/1.·s, (4.2 ± 0.2) × 10?5 mole2/1.2·s, (5.0 · 0.3) × 10?7 mole3/1.3·s, (1.1 ± 0.1) × 10?3 1.2/mole2·s, and (3.7 ± 0.2) × 10?3 1.3/mole3·s at 298.2°K and at an ionic strength of 2.00M maintained by adding sodium chloride. The stoichiometric equilibrium constant under similar conditions is 0.022 ± 0.003. Differentvalues of these parameters were obtained when sodium perchlorate and sodiumnitrate were used to control ionic strength. The results are compared with those from previous reports and a mechanism is proposed based upon an initial rapid equilibrium followed by a rate-determining attack of water upon H3AsO3I+, H2AsO3I, and HAsO3I?. 相似文献