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101.
In various formulations of plasticity, there is evident a structure embracing several features, including inviscidity, a yield condition, and a constitutive inequality. By means of these features the constitutive equations of plasticity are derived. In the present paper we introduce a viscoplastic counterpart of the constitutive inequality of plasticity, and we consider its physical significance. We also present a theory of viscoplasticity having a structure similar to that of plasticity and its relation with the Hohenemser-Prager prototype of viscoplastic constitutive relations is considered. 相似文献
102.
103.
UPLC/MS(E); a new approach for generating molecular fragment information for biomarker structure elucidation 总被引:1,自引:0,他引:1
Plumb RS Johnson KA Rainville P Smith BW Wilson ID Castro-Perez JM Nicholson JK 《Rapid communications in mass spectrometry : RCM》2006,20(13):1989-1994
A new approach to obtain fragmentation information in liquid chromatography/mass spectrometry (LC/MS) studies of small molecules in complex mixtures is presented using simultaneous acquisition of exact mass at high and low collision energy, MS(E). LC/MS-TOF and LC/MS/MS-TOF are powerful tools for the analysis of complex mixtures, especially those for biological fluids allowing the elucidation of elemental composition and fragmentation information. In this example the composition of rat urine was studied using this new approach, allowing the structures of several endogenous components to be confirmed in one analytical run by the simultaneous acquisition of exact mass precursor and fragment ion data. The spectral data obtained using this new approach are comparable to those obtained by conventional LC/MS/MS as exemplified by the identification of endogenous metabolites present in rat urine. 相似文献
104.
Alla B. Antonova Michael I. Bruce Paul A. Humphrey Brian K. Nicholson Brian W. Skelton Natasha N. Zaitseva 《Journal of organometallic chemistry》2006,691(22):4694-4707
A series of alkynyl-tricobalt carbonyl clusters, Co3(μ3-CnR)(μ-dppm)(CO)7 [R = But, Ph, C6H4I, C6H4CCPh, SiMe3, Fc, Au(PPh3)] containing three, five or seven carbons in the chain, have been prepared by elimination of phosphine-gold(I) halides in reactions between Co3(μ3-CBr)(μ-dppm)(CO)7 and Au(CCR)(PPh3) or between Co3{μ3-CCCAu(PR3)} (μ-dppm)(CO)7 (R = Ph, tol) and ICCR′ (R′ = SiMe3, Fc). The use of poly-substituted arenes or ferrocenes has enabled preparation of the complexes 1,4-{(OC)7(μ-dppm)Co3 (μ3-CCC)}2C6H3X-5 (X = H, Br), 1,3,5-{(OC)7(μ-dppm)Co3(μ3-CCC)}3C6H3 and 1,1′-{(OC)7(μ-dppm)Co3 (μ3-CCC)}2Fc′ [Fc′ = Fe(η-C5H4-)2]. The X-ray determined molecular structures of 12 of the complexes are reported. 相似文献
105.
The concept of self-entanglement is introduced to describe a mixed state or ensemble density as a pure state in an augmented Hilbert space formed by the products of the individual states forming a mixed state (or ensemble). We use this representation of mixed states to show that upon dissociation a neutral homonuclear diatomic molecule will separate into two neutral atoms. 相似文献
106.
We have developed and tested in terms of atomic calculations an exact, analytic and computationally simple procedure for determining the functional derivative of the exchange energy with respect to the density in the implementation of the Kohn–Sham formulation of density functional theory (KS-DFT), providing an analytic, closed-form solution of the self-interaction problem in KS-DFT. We demonstrate the efficacy of our method through ground-state calculations of the exchange potential and energy for atomic He and Be atoms, and comparisons with experiment and the results obtained within the optimized effective potential (OEP) method. 相似文献
107.
Zolot AM Giorgetta FR Baumann E Nicholson JW Swann WC Coddington I Newbury NR 《Optics letters》2012,37(4):638-640
We demonstrate a dual-comb spectrometer using stabilized frequency combs spanning 177 to 220 THz (1360 to 1690 nm) in the near infrared. Comb-tooth-resolved measurements of amplitude and phase generate over 4×10(5) individually resolved spectral elements at 100 MHz point spacing and kilohertz-level resolution and accuracy. The signal-to-noise ratio is 100 to 3000 per comb tooth. Doppler-broadened phase and amplitude spectra of CO(2), CH(4), C(2)H(2), and H(2)O in a 30 m multipass cell agree with established spectral parameters, achieving high-resolution measurements with optical bandwidth generally associated with blackbody sources. 相似文献
108.
Hodgkinson JT Galloway WR Wright M Mati IK Nicholson RL Welch M Spring DR 《Organic & biomolecular chemistry》2012,10(30):6032-6044
Many species of bacteria employ a mechanism of intercellular communication known as quorum sensing which is mediated by small diffusible signalling molecules termed autoinducers. The most common class of autoinducer used by Gram-negative bacteria are N-acylated-L-homoserine lactones (AHLs). Pseudomonas aeruginosa is a clinically important bacterium which is known to use AHL-mediated quorum sensing systems to regulate a variety of processes associated with virulence. Thus the selective disruption of AHL-based quorum sensing represents a strategy to attenuate the pathogenicity of this bacterium. Herein we describe the design, synthesis and biological evaluation of a collection of structurally novel AHL mimics. A number of new compounds capable of modulating the LasR-dependent quorum sensing system of P. aeruginosa were identified, which could have value as molecular tools to study and manipulate this signalling pathway. Worthy of particular note, this research has delivered novel potent quorum sensing antagonists, which strongly inhibit the production of virulence factors in a wild type strain of this pathogenic bacterium. 相似文献
109.
The attenuation of wave modes of ultrasound propagating in a number of different diameter stainless steel wires (in the range 0.25-1.21 mm) has been found experimentally. Most modes display an attenuation minimum at certain frequencies. The varying behaviour of mode attenuation with frequency, which is called selective attenuation, is due, in part, to changing proportions of the different types of wave motion that constitute a mode. Selective attenuation is discussed in the light of two theoretical models. One model, which considers the waveguide medium as being viscoelastic in nature, is shown qualitatively to be in reasonable agreement with experimental results but nevertheless leaves a number of questions unanswered. 相似文献
110.
Experimental results of ultrasound of varying frequency (0.8-5.0 MHz) propagating in cold drawn wires of stainless steel and aluminium ranging in diameter from 0.25 to 1.21 mm are in close agreement with theoretical predictions. This agreement is maintained when the coupling medium between the wire and the ultrasound source is a short distance of water. Similar measurements for brass and copper wires are in less close agreement with theory due, probably, to the effect of greater anisotropy. 相似文献