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91.
In the electronic version of the original article, the issue number shown in the header of the article opening page was wrong. It should be Issue 5 as in Acta Mechanica Sinica (2012) 28(5): 1374-1381. 相似文献
92.
M. Chiesa M. C. Paganini E. Giamello D. M. Murphy 《Research on Chemical Intermediates》2002,28(2-3):205-214
The present contribution aims to show that detailed information on structure and location of surface defective sites (surface vacancies, low co-ordination sites) can be obtained by combining data on the chemical reactivity of polycrystalline surfaces and EPR data. The use of nitrous oxide for bleaching trapped electron centres at the surface of MgO produces a remarkable variety of O- species, which differ in their values of the energy splitting (δE) term between the pz and the other two p orbitals of the radical ion. This indicates the existence of a corresponding variety of surface traps having different structural features. 相似文献
93.
A repetitive potential cycling procedure was used to produce a specific multilayer hydrous oxide film on copper in base at
60 °C. Such a deposit undergoes reduction in a quasi-reversible manner at ca. −0.1 V (RHE), i.e. at a potential that is unrelated
to Pourbaix data for copper but, as demonstrated previously, is of major significance with regard to the electrocatalytic
behaviour of this electrode system. In accordance with the incipient hydrous oxide/adatom mediator model of electrocatalysis,
an active surface state of the metal (Cu*) is assumed to be involved both in electrocatalysis and as a primary product in
the hydrous oxide reduction reaction. While the latter process occurs very rapidly at −0.1 V, it is not usually reversible
as it is accompanied by subsequent rapid loss of the active state of the metal. The same general approach was used previously
to explain the hydrous oxide and electrocatalytic behaviour of a range of noble metals.
Received: 28 August 1999 / Accepted: 11 November 1999 相似文献
94.
Karen A. Murphy Jessica M. Eisenhauer Daniel A. Savin 《Journal of Polymer Science.Polymer Physics》2008,46(3):244-252
A series of amphiphilic block copolymers composed of poly(ethylene oxide) and poly(lactide) were synthesized and their solution properties studied using static and dynamic light scattering. These materials self‐assemble in aqueous media with the hydrodynamic radius increasing with increasing hydrophobic fraction in the copolymer. To ascertain the potential for use of these materials as degradable coatings in delivery applications, block copolymers of varying compositions were adsorbed onto a series of colloidal polystyrene particles with varying radii, and the thickness of the adsorbed layer was determined from changes in the hydrodynamic size. The adlayer thicknesses ranged from 3 to 14 nm with varying block copolymer compositions, and colloid radii. The trends fit well with theoretical models for adlayer thickness, with the exception of the smallest colloids. In these systems, we propose that the colloids may become encapsulated into the block copolymer assembly. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 244–252, 2008 相似文献
95.
Yao S Hinds MG Murphy JM Norton RS 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2011,211(2):243-247
Conformational or chemical exchange can cause significant sensitivity loss in NMR spectroscopy through resonance broadening for nuclear spins involved in these processes. While this effect may sometimes be alleviated by manipulating experimental conditions such as temperature, pH, and buffers, conditions optimal for all resonances are not always achievable. As a consequence, any means of recovering or minimizing this exchange-induced sensitivity loss is potentially of significant value in regaining information otherwise lost. We report the experimental observation of significant sensitivity gain for nuclear spins undergoing chemical exchange with solvent (water) at exchange rates ca 1-10 s(-1) in (1)H-(15)N correlation spectra of proteins acquired with band-selective pulses (the SOFAST-HMQC sequence). 相似文献
96.
Murphy K Harris AD Diukova A Evans CJ Lythgoe DJ Zelaya F Wise RG 《Magnetic resonance imaging》2011,29(10):1382-1389
Pulsed arterial spin labeling (PASL) is an increasingly common technique for noninvasively measuring cerebral blood flow (CBF) and has previously been shown to have good repeatability. It is likely to find a place in clinical trials and in particular the investigation of pharmaceutical agents active in the central nervous system. We aimed to estimate the sample sizes necessary to detect regional changes in CBF in common types of clinical trial design including (a) between groups, (b) a two-period crossover and (3) within-session single dosing. Whole brain CBF data were acquired at 3 T in two independent groups of healthy volunteers at rest; one of the groups underwent a repeat scan. Using these data, we were able to estimate between-groups, between-session and within-session variability along with regional mean estimates of CBF. We assessed the number of PASL tag-control image pairs that was needed to provide stable regional estimates of CBF and variability of regional CBF across groups. Forty tag-control image pairs, which take approximately 3 min to acquire using a single inversion label delay time, were adequate for providing stable CBF estimates at the group level. Power calculations based on the variance estimates of regional CBF measurements suggest that comparatively small cohorts are adequate. For example, detecting a 15% change in CBF, depending on the region of interest, requires from 7-15 subjects per group in a crossover design, 6-10 subjects in a within-session design and 20-41 subjects in a between-groups design. Such sample sizes make feasible the use of such CBF measurements in clinical trials of drugs. 相似文献
97.
98.
99.
P J Murphy 《The Journal of the Acoustical Society of America》1999,105(5):2866-2881
The measurement of the harmonics-to-noise ratio (HNR) in speech signals gives an indication of the aperiodicity of the speech waveform. This may be due to the presence of jitter, shimmer, additive noise, waveshape change, or some unknown combination of these factors. In order to estimate the HNR as a measure of the additive noise component only, the contaminating effects of the other contributory components must first be removed. A pitch synchronous harmonic analysis is proposed to overcome this problem. The procedure takes advantage of the time scale compression-frequency expansion property of the Fourier series in order to eliminate jitter and shimmer. Successive spectra are added by harmonic number as opposed to frequency location, and perturbation is removed due to the fact that the relative heights of the harmonic components remain the same for scaled signals. The technique is examined on synthetically generated voice signals. A discussion of the results is given in terms of human voice signals, characterization of jitter, vocal tract filtering effects, perturbation mechanisms, nonlinear dynamics, and the possibility of developing the method for use with inverse filtering strategies. 相似文献
100.
S M Waybright C P Singleton K Wachter C J Murphy U H Bunz 《Journal of the American Chemical Society》2001,123(9):1828-1833
A nano-architectural system that has high variability while maintaining component specificity is described. Tetraphenylcyclobutadiene(cyclopentadienyl)cobalt complexes and phenyleneethynylene trimers were synthesized and subsequently modified with oligonucleotides utilizing standard phosphoramidite chemistry. The resulting oligonucleotide modified organics (OMOs) were characterized by UV-vis spectroscopy, fluorescence spectroscopy, and phosphate analysis. Hybridization of these OMOs resulted in a series of self-assembled oligomeric hybrids of varying length and topology. These hybrids were characterized by melting temperature, polyacrylamide gel electrophoresis, and fluorescence spectroscopy. This model system demonstrates the power of DNA to self-assemble modules of interest-independent of the module itself. 相似文献