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881.
This paper presents an analysis of the compound effect of finite temperature differences and fluid friction on the existence
of an optimum laminar flow regime in singly connected micro channels with complex free flow area cross sections. A widespread
conviction has been established that the two competing irreversibility sources in a channel flow with heat transfer lead to
the existence of an optimum flow regime. The results presented in this paper clearly shows the opposite. When an objective
function is represented by the entropy generation rate per unit heat capacity rate of the fluid stream, the thermodynamic
optimum flow regime represents a rather rare occurrence in the laminar region of irregularly shaped ducts. The presence of
an extremum is more probable for very small diameters, the ones of an order of magnitude of O(≤10−3 m). The analysis is performed for selected ranges of relevant geometric, flow, and thermal parameters of a set of straight
micro channels with irregular free flow area cross-sections. The following geometries of the free flow area cross section
were investigated: (i) sine duct, (ii) circular duct, (iii) elliptical duct, (iv) moon-shaped ducts, and (v) four-cuspped
duct. The range of Reynolds numbers has been established between O(102) and O(104). The existence of the objective function minimum is confirmed for ducts with an irregular cross section only for very small
hydraulic diameters. These minima are relatively weak, and as a general rule, the sets of optimum parameters are close to
the onset of turbulence or possibly even in the transitional or turbulent regions.
Received on 10 November 1998 相似文献
882.
E. Seligmann Eichholz R. H. Williams H. C. Sherman F. W. Richardson und E. W. T. Jones 《Fresenius' Journal of Analytical Chemistry》1909,48(7-8):502-504
Ohne Zusammenfassung 相似文献
883.
C. Maurel M. Bellec B. Bousquet J.J. Videau M. Richardson 《Journal of luminescence》2009,129(12):1514-1891
We report on exposing a photosensitive zinc phosphate glass containing silver to different radiation (electron, gamma, optical). Laser irradiations using nanosecond ultraviolet (UV) and femtosecond infrared (IR) laser are compared with gamma and electron exposure. All irradiated glasses exhibit absorption maxima around 320 nm and 380 nm and emission in the visible spectral range. Following exposure, silver clusters are formed. The optical response of such species is investigated using absorption and fluorescence spectroscopic techniques. The mechanism of formation of these clusters is discussed. 相似文献
884.
885.
Brian R. Linton Michael H. Reutershan Elizabeth A. Richardson Charles W. Ashley Scott J. Miller 《Tetrahedron letters》2007,48(11):1993-1997
Peptide-based catalysts have been developed that promote the asymmetric Michael addition of nitroalkanes. The most effective peptides contain a β-turn structural element as well as a basic histidine and an arylsulfonamide-protected arginine. Excellent yields with enantioselectivities of up to 74% ee have been observed. 相似文献
886.
Let M be a compact Riemannian manifold endowed with an isometric action of a compact, connected Lie group. The method of the Witten
deformation is used to compute the virtual representation-valued equivariant index of a transversally elliptic, first order
differential operator on M. The multiplicities of irreducible representations in the index are expressed in terms of local quantities associated to
the isolated singular points of an equivariant bundle map that is locally Clifford multiplication by a Killing vector field
near these points.
相似文献
887.
B. Alver B. B. Back M. D. Baker M. Ballintijn D. S. Barton R. R. Betts A. A. Bickley R. Bindel W. Busza A. Carroll Z. Chai V. Chetluru M. P. Decowski E. García T. Gburek N. George K. Gulbrandsen C. Halliwell J. Hamblen I. Harnarine M. Hauer C. Henderson D. J. Hofman R. S. Hollis R. Holyński B. Holzman A. Iordanova E. Johnson J. L. Kane N. Khan P. Kulinich C. M. Kuo W. Li W. T. Lin C. Loizides S. Manly A. C. Mignerey R. Nouicer A. Olszewski R. Pak C. Reed E. Richardson C. Roland G. Roland J. Sagerer H. Seals I. Sedykh C. E. Smith M. A. Stankiewicz P. Steinberg G. S. F. Stephans A. Sukhanov A. Szostak M. B. Tonjes A. Trzupek C. Vale G. J. van Nieuwenhuizen S. S. Vaurynovich R. Verdier G. I. Veres P. Walters E. Wenger D. Willhelm F. L. H. Wolfs B. Wosiek K. Wo?niak S. Wyngaardt B. Wys?ouch 《The European Physical Journal C - Particles and Fields》2009,61(4):575-582
A selection of experimental results from the PHOBOS Collaboration relevant for probing high-energy nuclear collisions with
high transverse momentum particles is presented. The inclusive yields of charged particles and comparisons between nuclear
and elementary collisions already reveal a large amount of parton energy loss in the hot and dense medium created in heavy
ion collisions. Remarkable scaling and factorization features are observed, unifying the data taken at various collision energies,
centralities and nuclear sizes. To further analyze the nature of the energy loss, a measurement of pseudorapidity (Δη) and azimuthal angle (Δφ) correlations between high transverse momentum charged hadrons (p
T
>2.5 GeV/c) and all associated charged particles is presented at both short-range (small Δη) and long-range (large Δη) over a continuous detector acceptance covering −4<Δη<2. Various near- and away-side features of the correlation structure are discussed as a function of centrality in Au + Au
collisions at
GeV. The results provide new information about the longitudinal (Δη) extent of the near-side ‘ridge’ structure, first observed by the STAR Collaboration over a narrower η range. In central Au + Au collisions the ridge structure extends to at least Δη=4, and its strength completely diminishes as collisions become more peripheral.
Presenter of the paper on the 3rd International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions,
8–14 June 2008, Illa da Toxa (Galicia-Spain). 相似文献
888.
The concept of a convergence tower space, or equivalently, a convergence approach space is formulated here in the context of a Cauchy setting in order to include a completion theory. Subcategories of filter tower spaces are defined in terms of axioms involving a general t-norm, T, in order to include a broad range of spaces. A T-regular sequence for a filter tower space is defined and, moreover, it is shown that the category of T-regular objects is a bireflective subcategory of all filter tower spaces. A completion theory for subcategories of filter tower spaces is given. 相似文献
889.
In this Letter we report a density functional all-electron calculation of the structural and electronic properties of the polynitrogen high-energy molecule, azidopentazole (N8). We have also performed a vibrational analysis to determine the IR and Raman spectra. Our calculated geometrical properties and vibrational frequencies are in good agreement with previous ab initio and density functional calculations. The weaker IR modes show a different relative ordering than previously reported. We also report calculated Raman intensities for azidopentazole. 相似文献
890.
Sergey O. Bachurin Galina F. Makhaeva Elena F. Shevtsova Alexey Yu. Aksinenko Vladimir V. Grigoriev Pavel N. Shevtsov Tatiana V. Goreva Tatiana A. Epishina Nadezhda V. Kovaleva Elena A. Pushkareva Natalia P. Boltneva Sofya V. Lushchekina Alexey V. Gabrelyan Vladimir L. Zamoyski Lyudmila G. Dubova Elena V. Rudakova Vladimir P. Fisenko Elena V. Bovina Rudy J. Richardson 《Molecules (Basel, Switzerland)》2021,26(18)
A new series of conjugates of aminoadamantane and γ-carboline, which are basic scaffolds of the known neuroactive agents, memantine and dimebon (Latrepirdine) was synthesized and characterized. Conjugates act simultaneously on several biological structures and processes involved in the pathogenesis of Alzheimer’s disease and some other neurodegenerative disorders. In particular, these compounds inhibit enzymes of the cholinesterase family, exhibiting higher inhibitory activity against butyrylcholinesterase (BChE), but having almost no effect on the activity of carboxylesterase (anti-target). The compounds serve as NMDA-subtype glutamate receptor ligands, show mitoprotective properties by preventing opening of the mitochondrial permeability transition (MPT) pore, and act as microtubule stabilizers, stimulating the polymerization of tubulin and microtubule-associated proteins. Structure–activity relationships were studied, with particular attention to the effect of the spacer on biological activity. The synthesized conjugates showed new properties compared to their prototypes (memantine and dimebon), including the ability to bind to the ifenprodil-binding site of the NMDA receptor and to occupy the peripheral anionic site of acetylcholinesterase (AChE), which indicates that these compounds can act as blockers of AChE-induced β-amyloid aggregation. These new attributes of the conjugates represent improvements to the pharmacological profiles of the separate components by conferring the potential to act as neuroprotectants and cognition enhancers with a multifunctional mode of action. 相似文献