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81.
We investigate the stationary nonequilibrium (heat transporting) states of the Lorentz gas. This is a gas of classical point particles moving in a region gL containing also fixed (hard sphere) scatterers of radiusR. The stationary state considered is obtained by imposing stochastic boundary conditions at the top and bottom of , i.e., a particle hitting one of these walls comes off with a velocity distribution corresponding to temperaturesT
1 andT
2 respectively,T
1 <T
2. Letting be the average density of the randomly distributed scatterers we show that in the Boltzmann-Grad limit,,R 0 with the mean free path fixed, the stationary distribution of the Lorentz gas converges in theL
1-norm to the stationary distribution of the corresponding linear Boltzmann equation with the same boundary conditions. In particular, the steady state heat flow in the Lorentz gas converges to that of the linear Boltzmann equation, which is known to behave as (T
2-T
1)/L for largeL, whereL is the distance from the bottom to the top wall: i.e., Fourier's law of heat conduction is valid in the limit. The heat flow converges even in probability. Generalizations of our result for scatterers with a smooth potential as well as the related diffusion problem are discussed.Research supported in part by NSF Grant no. Phy 77-22302.On leave of absence from the Fachbereich Physik der Universität, München. Work supported by a DFG fellowship. 相似文献
82.
The redox coupleb-nor-biladiene-ac (2)/b-nor-bilatriene-abc (3) exhibits an oxidative half wave potential of 800 mV in acetonitrile solution. It is demonstrated that it can be used as an extremely efficient electron carrier through bulk membranes. Whereas2 is not suitable as a ligand in carrier mediated cation transport,3 is a medium suited carrier for Cu(II) or Zn(II) ions, however, it is the most efficient one found so far for transport of Hg(II) ions. A 1:1 zinc chelate of3 is isolated and characterized. it is deduced to represent a polymer consisting of about 73 monomer units. 相似文献
83.
Facilitated transport process has attracted much attention because high selectivity and high permeability may be achieved. However, most research on facilitated transport process is concerned only with uniform membranes. In this paper, a model predicting the gas separation performance of a hollow-fiber module with facilitated transport membrane is developed. The influence of feed rate, operation pressure, and permeant-feed flow pattern on the module performance are analyzed and the effect of the nonuniform distribution of reaction equilibrium constant is examined. The calculated results show that the nonuniform active distribution may cause an improved module performance. Because of the passive transport characteristics of the facilitated transport process, the mass transfer driving force across the membrane has a great influence on the improvement of the module performance through a facilitated transport effect. 相似文献
84.
Jorge Macanás 《Analytica chimica acta》2005,534(1):101-108
Activated composite membranes (ACMs) containing di-(2-ethylhexyl) dithiophosphoric acid (D2EHDTPA) as a carrier have been found to facilitate the transport and separation of several cations. This paper describes an approach to the chemical characterisation of the transport phenomena of Zn2+, Cd2+, Cu2+, Ni2+, Sn2+ and In3+ by an ACM. The selectivity of D2EHDTPA based ACM towards different metal ions is presented and discussed focusing in Zn2+ and Cd2+ transport and recovery. Selectivity demonstrates that zinc ions are removable from mixtures due to the different extraction strength of D2EHDTPA. Such selectivity is based on the differences of the dynamic behaviour of the metal ions transport. In addition, a correlation of the chemical behaviour of those ACM systems with the corresponding solvent extraction systems has been found. 相似文献
85.
A.?Ya.?NeimanEmail author N.?N.?Pestereva A.?R.?Sharafutdinov Yu.?P.?Kostikov 《Russian Journal of Electrochemistry》2005,41(6):598-611
The conduction and transport numbers of charge carriers for composites in the systems MeWO4-WO3 (Me = Ca, Sr, Ba) are studied as a function of the temperature and the activity of oxygen in a gas phase. The transport numbers are determined by an emf method and are estimated from dependences of conductance on the activity of oxygen in a gas phase. The deficiencies of the given procedure as applied to investigation of properties of composite phases are analyzed. The materials under study are classified with a class of metacomposites. The concentration intervals of the ionic, mixed, and electronic conductions are determined. The conduction of composites of compositions (100 − x)MeWO4 ⋅ xWO3 is predominantly ionic at x ≤ 10 (Me = Ca), x ≤ 60 (Me = Sr), and x ≤ 45 (Me = Ba). The obtained data are explained in the framework of a model that represents a composite as a distributed matrix system where a film of surface phase MeW-s with a high mobility of oxygen ions plays the role of a connected matrix. It is presumed that the surface phase MeW-s possesses double-sided surface activity (α MeW-s ≤
) and a higher mobility with respect to MeWO4 and WO3. The discovered anomalies of dependences
(T) and partial dependences
, σel(T) are explained by a change in the stoichiometry, morphology, and the degree of connectedness of surface phase MeW-s caused by with a change in the temperature and composition of composites.__________Translated from Elektrokhimiya, Vol. 41, No. 6, 2005, pp. 680–693.Original Russian Text Copyright © 2005 by Neiman, Pestereva, Sharafutdinov, Kostikov.Published on the basis of a report delivered at the VII Meeting on Fundamental Problems in Solid-State Ionics (Chernogolovka-2004). 相似文献
86.
The ternary rare-earth nickel arsenides R3Ni7As5 (R=La, Ce, Pr, Nd, Sm) were prepared by arc melting the elemental components and subsequent annealing at T=1070 K. The crystal structure of Ce3Ni7As5 was determined from single-crystal X-ray data: space group Pmmn, Z=2; a=1.24210(6), b=0.40797(2), c=0.96436(5) nm, RF=0.037 (Rw=0.044); 596 independent reflections; 53 variable parameters. It is a new structure type, which belongs to the family of BaAl4-related structures. The magnetic properties are as follows: La3Ni7As5 is a Pauli-type paramagnet above 4.2 K, Pr3Ni7As5 remains paramagnetic in the temperature range investigated and Nd3Ni7As5 undergoes a ferromagnetic ordering at TC=24 K. Sm3Ni7As5 orders antiferromagnetically at a Néel temperature of TN=18 K followed by a spin flip towards parallel spin-alignment below TC=6 K. Ce3Ni7As5 reveals a strong deflection of the linear temperature dependence of the inverse susceptibility due to an intermediate valence behavior. The temperature dependence of the electrical resistivities for the La, Pr, Nd, Sm containing samples corroborates with the metallic state of the non-magnetic (La) and the magnetically ordered compounds, whereas in case of Ce3Ni7As5 the resistivity seems to be determined by an interplay of Kondo scattering and crystalline field effects. LIII X-ray absorption spectra confirm the demagnetization effects owing from valence fluctuations, the actual valence thereby changes from ν=3.10-3.14 at room temperature and 10 K, respectively. 相似文献
87.
The ternary phases existing on the quasi binary section CoSi/FeSi and CoSi2/β‐FeSi2 have been investigated by solid state reactions and chemical transport. The solid solution serie CoxFe1‐xSi can be described as a regular solution. The transport behaviour calculated is in good agreement with the experiments. The phases have been characterized by X‐ray powder diffraction, EDX and ICP‐OES. The temperature dependence of the resistivity has been measured from 20 K up to room temperature on single crystals. 相似文献
88.
89.
A new DNA assay has been designed, prepared and applied for the chemical investigation of reductive electron transfer through the DNA. It consists of 5-(10-methyl-phenothiazin-3-yl)-2'-deoxyuridine (Ptz-dU, 1) as the photoexcitable electron injector and 5-bromo-2'-deoxyuridine (Br-dU) as the electron trap. The Ptz-dU-modified oligonucleotides were synthesised by means of a Suzuki-Miyaura cross-coupling protocol and subsequent automated phosphoramidite chemistry. Br-dU represents a kinetic electron trap, since it undergoes a chemical modification after its one-electron reduction that can be analysed by piperidine-induced strand cleavage. The quantification of the strand cleavage yields from irradiation experiments reveals important information about the electron-transfer efficiency. The performed DNA studies focused on the base sequence dependence of the electron-transfer efficiency with respect to the proposal that C*- and T*- act as intermediate electron carriers during electron hopping. From our observations it became evident that excess-electron transfer is highly sequence dependent and occurs more efficiently over T-A base pairs than over C-G base pairs. 相似文献
90.
靛红掺杂聚吡咯膜修饰电极的电荷传输 总被引:5,自引:1,他引:5
利用交流阻抗法研究了靛红掺杂聚吡咯膜内的电荷传输,通过非线性最小二乘法拟合,得出了体系的等效电路,并计算出其电荷扩散系数和异相电子传递反应速率常数。实验结果表明,随着膜厚的增加,活性点增多,异相电子传递反应速率常数增大,同时表观扩散系数也增大。 相似文献