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1.
Spatial structures break their symmetry under the influence of shear stress arising from fluid flow. Here, we present surface instabilities appearing on chitosan tubes when an acidic solution of chitosan with various molecular weight is injected into a pool of sodium hydroxide solution. At slow flow rates wrinkle-to-fold transition takes place along the direction of the flow yielding a banded structure. For greater injection rates we observe coexisting modes of wrinkles and folds which are stabilized to periodic wrinkles when the alkaline concentration is increased. The instabilities are characterized by the scaling laws of the pattern wavelength and amplitude with the tube characteristics. Our experimental adaptation of mechanical instabilities provides a new in situ method to create soft biomaterials with the desired surface morphology without the use of any prefabricated templates. 相似文献
2.
Applying Kubo's formulae and damping theoretical arguments the electric, thermoelectric and thermal transport coefficients for a system of free and independent electrons and fixed scatterers in the presence of an external magnetic field are calculated. Assumingδ-type scatterers it is shown that in the quantum regionkT?ω?ζ the Wiedemann-Franz law holds for the oscillating symmetric conductivities, whereas in the case of the antisymmetric ones quantum mechanical deviations from this law occur. For strong magnetic fields and arbitrary scattering potential the symmetric transversal transport coefficients can be expressed by Titeica type formulae. 相似文献
3.
Damping theoretical calculation of the transverse magnetoresistance in the quantum limit yields an approximate power law ρ ∝ Bα with α = 3 for short range and α = 1 for long range impurities — in agreement with experimental results. 相似文献
4.
An expression for the heat conductivity
xx
is derived in the effective medium approximation. Mott type formulas are obtained for
xx
and the Peltier coefficient
xx
. Using percolation theory in a three-dimensional system the Wiedemann-Franz ratio was found to depend on the temperature like
. The Mott type formulas were evaluated in a similar way for a two-dimensional system in the quantum Hall regime within the high-field percolation model. In contrast to previous calculations of the high field hopping conductivity
xx
, the results are fully consistent with the experimental data on
xx
and the density of states at the Fermi level. Finally,
xx
is estimated which together with
xx
and
xy
=ie
2/h(i=0,1,2,...), determines both thermopower coefficients
xx
and
xy
.Dedicated to Professor W. Brenig on the occasion of his 60th birthday 相似文献
5.
K. Gruiz M. Moln��r E. Fenyvesi Cs. Hajdu ��. Atk��ri K. Bark��cs 《Journal of inclusion phenomena and macrocyclic chemistry》2011,70(3-4):299-306
Experimental results, which may serve as basis for innovative applications of cyclodextrins (CDs) in environmental technologies, are presented here. Some newly developed CD-aided tools are used in sampling, measuring the concentration or testing the effect of contaminants in water and soil. The innovative methods such as the bacterial bioassays with CD-increased sensitivity or the CD-filled absorptive samplers for air and water sampling are utilised in environmental exposure, hazard and risk assessment. Technological developments aim the reduction of the risk of chemical substances in waters and soils. CD-aided environmental remediation is introduced through examples for the elimination of organic contaminants from water by CD-filters, and for the enhancement of the mobility and availability of soil contaminants in this way increasing the efficiency of soil remediation by water extraction, chemical oxidation, biodegradation, etc. 相似文献
6.
We give a complete characterization of so-called powerful arithmetic progressions, i.e. of progressions whose kth term is a kth power for all k. We also prove that the length of any primitive arithmetic progression of powers can be bounded both by any term of the progression different from 0 and ±1, and by its common difference. In particular, such a progression can have only finite length. 相似文献
7.
László B. Kiss János Kertész János Hajdu 《Zeitschrift für Physik B Condensed Matter》1990,81(2):299-303
We investigate the shape as well as the size- and temperature-dependence of the conductance noise spectrum of a small system containing electrons and both fixed and mobile scatterers. If the number of mobile scatterers within a phase-coherent region is sufficiently large, the temporal variation of the conductance can be viewed as a random walk process limited by the universal conductance fluctuations, resulting in a practically Lorentzian power spectrum. We discuss the conditions under which the noise spectrum of a system consisting of many phase-coherent regions is either Lorentzian or 1/f-like. The temperature-dependence of the power spectrum is determined by the hopping mechanism and the variation of the phase breaking length. As a function of temperature the spectrum satisfies power law scaling relations with exponents depending on the dimension and the temperature range; the spectral intensity can both increase and decrease with decreasing temperature. 相似文献
8.
In this paper we consider representations of algebraic integers of a number field as linear combinations of units with coefficients coming from a fixed small set, and as sums of elements having small norms in absolute value. These theorems can be viewed as results concerning a generalization of the so-called unit sum number problem, as well. Beside these, extending previous related results we give an upper bound for the length of arithmetic progressions of \(t\) -term sums of algebraic integers having small norms in absolute value. 相似文献
9.
A system of independent electrons interacting with an arbitrary number of fixed point scatterers on the surface of an infinitely long cylinder is considered. It is shown that (at zero temperature) the equilibrium Byers-Yang Hall current takes the same value as for free electrons if the Fermi energy lies in an energy gap. 相似文献
10.
Synthesis of a new series of phospholipid analogues to serve as activity-based probes of secretory phospholipase A2 enzymes is reported. The synthesis is based upon (1) preparation of long-chain esters and amides of glyceric acid, followed by (2) regioselective derivatization of the diol function of the molecule to achieve phosphorylation at the primary hydroxyl group, and to introduce the incipient sn-2-ester group of the target compounds. The sequence has been shown to allow incorporation of fluorescent, paramagnetic, and redox-active reporter groups, leading to phospholipid analogues applicable to detect and measure enzyme activity, to develop highly specific, real-time spectroscopic assay of phospholipase A2 enzymes, as well as to track the metabolic fate of the hydrolysis products. The synthetic method has a great deal of flexibility to open the way to the design and synthesis of activity-probes for other phospholipid metabolizing enzymes as well. 相似文献