排序方式: 共有39条查询结果,搜索用时 15 毫秒
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Kasyutich V.L. Bale C.S.E. Canosa-Mas C.E. Pfrang C. Vaughan S. Wayne R.P. 《Applied physics. B, Lasers and optics》2003,76(6):691-697
We present an application of cavity-enhanced absorption spectroscopy with an off-axis alignment of the cavity formed by two
spherical mirrors and with time integration of the cavity-output intensity for detection of nitrogen dioxide (NO2) and iodine monoxide (IO) radicals using a violet laser diode at λ=404.278 nm. A noise-equivalent (1σ≡ root-mean-square variation
of the signal) fractional absorption for one optical pass of 4.5×10-8 was demonstrated with a mirror reflectivity of ∼0.99925, a cavity length of 0.22 m and a lock-in-amplifier time constant
of 3 s. Noise-equivalent detection sensitivities towards nitrogen dioxide of 1.8×1010 molecule cm-3 and towards the IO radical of 3.3×109 molecule cm-3 were achieved in flow tubes with an inner diameter of 4 cm for a lock-in-amplifier time constant of 3 s. Alkyl peroxy radicals
were detected using chemical titration with excess nitric oxide (RO2+NO→RO+NO2). Measurement of oxygen-atom concentrations was accomplished by determining the depletion of NO2 in the reaction NO2+O→NO+O2. Noise-equivalent concentrations of alkyl peroxy radicals and oxygen atoms were 3×1010 molecule cm-3 in the discharge-flow-tube experiments.
Received: 4 February 2003 / Revised version: 10 March 2003 / Published online: 12 May 2003
RID="*"
ID="*"Corresponding author. Fax: +44-1865/275-410, E-mail: vlk@physchem.ox.ac.uk 相似文献
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Greg BG Moorhead Laura Trinkle-Mulcahy Mhairi Nimick Veerle De Wever David G Campbell Robert Gourlay Yun Wah Lam Angus I Lamond 《BMC biochemistry》2008,9(1):28
Background
Protein phosphatase one (PP1) is a ubiquitously expressed, highly conserved protein phosphatase that dephosphorylates target protein serine and threonine residues. PP1 is localized to its site of action by interacting with targeting or regulatory proteins, a majority of which contains a primary docking site referred to as the RVXF/W motif. 相似文献5.
A new method was developed using AFM images of a fiber surface to regenerate the surface roughness in 3D geometry, such as the cylindrical shape of a “model” fiber. The Langevin equation was used to derive the fluctuations of a carbon fiber surface image. The equation contains two quantities, D(1) (h) and D(2) (h) which in physics represent drift and diffusion coefficients. Knowing this coefficient and adding a proper noise function, a similar surface of larger dimension with the same statistical properties of the initial data was created. The generated surface was mapped into cylindrical coordinates, then a mesh generated. The resulting reconstructed surface, input over the geometry of a cylindrical shape, can be implemented for finite element analysis of a single fiber surrounded by matrix and generalized to a many fiber model. 相似文献
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Characteristic parameters of drift vortices coupled to Alfvén waves in an inhomogeneous space plasma
We present detailed measurements of ion scale vortices of drift type coupled to Alfvén waves in an inhomogeneous and collisionless space magnetoplasma. The two free parameters of a dipolar vortex, intensity and spatial radius, are measured. The vortices are driven by a strong density gradient on a boundary layer with scale size of the same order as the vortex diameter. Observations of vortices off the gradient show that symmetry-breaking conditions in a real inhomogeneous plasma can lead not only to cross-field but also to cross-boundary anomalous transport of particles and energy. 相似文献
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The problems of conventional methods for determining sulphur content at elevated temperatures are discussed and a thermogravimetric technique for a direct continuous analysis is described. The technique is illustrated by employing the Cu-S system at 1200 and with a discussion of the necessary correction factors for buoyancy and volatilization being included.
One of the authors, C. W. B., is grateful to the Noranda Research Centre for a graduate fellowship. We are also grateful to the Canadian National Research Council for financial assistance. 相似文献
Zusammenfassung Es werden die Probleme der üblichen Methoden der Schwefelbestimmung bei hohen Temperaturen erörtert und eine thermogravimetrische Methode zur direkten kontinuierlichen Analyse vorgeschlagen. Das Verfahren wird an dem Beispiel des Systems Cu-S bei 1200 gezeigt mit Hinweis auf die infolge Auftrieb und Verflüchtigung nötige Korrektur.
Résumé On discute les problèmes posés par les méthodes conventionnelles pour doser le soufre aux températures élevées et l'on décrit une méthode thermogravimétrique pour l'analyse directe en continu. La technique est illustrée sur l'exemple du système Cu-S à 1200; on discute les facteurs correctifs que l'on doit appliquer pour tenir compte de la poussée et de la volatilisation.
. Cu-S 1200 .
One of the authors, C. W. B., is grateful to the Noranda Research Centre for a graduate fellowship. We are also grateful to the Canadian National Research Council for financial assistance. 相似文献
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alpha-Keto alkynes react with CO and H(2) in the presence of catalytic quantities of the zwitterionic rhodium complex (eta(6)-C(6)H(5)BPh(3))(-)Rh(+)(1,5-COD) and triphenyl phosphite affording either the 2-, 2(3H)-, or 2(5H)-furanones in 61-93% yields. The cyclohydrocarbonylation is readily accomplished using substrates containing alkyl, aryl, vinyl, and alkoxy groups at the acetylenic terminal, as well as a variety of primary, secondary, and tertiary alkyl, aryl, and heteroaryl groups connected to the ketone functionality. Structural and electronic properties present in the starting materials mediate the chemo- and regioselectivity of the reaction. 相似文献
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Matthew Blacklock Hrishikesh Bale Matthew Begley Brian Cox 《Journal of the mechanics and physics of solids》2012,60(3):451-470
A Monte Carlo algorithm is defined for generating replicas of textile composite specimens that possess the same statistical characteristics as specimens imaged using high resolution computed tomography. The textile reinforcement is represented by one-dimensional tow loci in three-dimensional space, which are easily incorporated into the Binary Model of textile composites. A tow locus is expressed as the sum of non-stochastic, periodic variations in the coordinates of the tow centroid and stochastic, non-periodic deviations. The non-stochastic variations have period commensurate with the dimensions of the unit cell of the textile, while the stochastic deviations, which describe geometrical defects, exhibit correlation lengths that may be incommensurate with the unit cell. The model is calibrated with data deduced in prior work from computed tomography images. The calibration obviates the need for assuming any ideal shape functions for the tow loci, which can take very general form. The approach is therefore valid for a wide range of textile architectures. Once calibrated, a Markov Chain algorithm can generate numerous stochastic replicas of a textile architecture very rapidly. These virtual specimens can be much larger than the real specimens from which the data were originally gathered, a necessary feature when real specimen size is limited by the nature of high resolution computed tomography. The virtual specimen generator is illustrated using data for an angle interlock weave. 相似文献