232 research outputs found
Steady-state composition of a two-component gas bubble growing in a liquid solution: self-similar approach
The paper presents an analytical description of the growth of a two-component
bubble in a binary liquid-gas solution. We obtain asymptotic self-similar time
dependence of the bubble radius and analytical expressions for the non-steady
profiles of dissolved gases around the bubble. We show that the necessary
condition for the self-similar regime of bubble growth is the constant,
steady-state composition of the bubble. The equation for the steady-state
composition is obtained. We reveal the dependence of the steady-state
composition on the solubility laws of the bubble components. Besides, the
universal, independent from the solubility laws, expressions for the
steady-state composition are obtained for the case of strong supersaturations,
which are typical for the homogeneous nucleation of a bubble.Comment: 12 pages, 2 figure
Dynamics of gas bubble growth in a supersaturated solution with Sievert's solubility law
This paper presents a theoretical description of diffusion growth of a gas
bubble after its nucleation in supersaturated liquid solution. We study systems
where gas molecules completely dissociate in the solvent into two parts, thus
making Sievert's solubility law valid. We show that the difference between
Henry's and Sievert's laws for chemical equilibrium conditions causes the
difference in bubble growth dynamics. Assuming that diffusion flux is steady we
obtain a differential equation on bubble radius. Bubble dynamics equation is
solved analytically for the case of homogeneous nucleation of a bubble, which
takes place at a significant pressure drop. We also obtain conditions of
diffusion flux steadiness. The fulfillment of these conditions is studied for
the case of nucleation of water vapor bubbles in magmatic melts.Comment: 22 pages, 3 figure
On details of the thermodynamical derivation of the Ginsburg--Landau equations
We examine the procedure of thermodynamical derivation of the
Ginsburg--Landau equation for current, which is given unclear and contradictory
interpretations in existing textbooks. We clarify all steps of this procedure
and find as a consequence a limitation on the validity range of the
thermodynamic Ginsburg--Landau theory, which does not seem to be explicitely
stated up to now: we conclude that the thermodynamic theory is applicable only
to a superconducting specimen that is not a part of an external
current-carrying loop.Comment: 11 pages. Accepted for publication in 'Superconductor Science and
Technology
The Twin Deficit and the Macroeconomic variables in Kenya
The purpose of this paper is to test the twin deficit hypothesis and empirical relationship between current account balance and budget deficit while including other important macroeconomic variables such as growth, interest rates, money supply (M3) in Kenya from 1963-2012. The study was based on co integration analysis and error correction model (ECM). The results reveal a long-run association between the trade deficit and the fiscal deficit. The findings indicate that the Keynesian view fits well for Kenya since the causality runs from budget deficit to current account deficit. We detected unidirectional causation between the twin deficits, running from budget deficit to current account directly and indirectly through budget deficits which raise real interest rates, crowd out domestic investment, and cause the currency to appreciate in relation to the other currencies and further deteriorates the current account deficit
Design and performance testing of quantitative real time PCR assays for influenza A and B viral load measurement
Background: The antiviral effect of anti-influenza drugs such as zanamivir may be demonstrated in patients as an increased rate of decline in viral load over a time course of treatment as compared with placebo. Historically this was measured using plaque assays, or Culture Enhanced Enzyme Linked Immunosorbent Assay (CE-ELISA). Objectives: to develop and characterise real time quantitative PCR (qPCR) assays to measure influenza A and B viral load in clinical samples, that offer improvements over existing methods, in particular virus infectivity assays. Study design: The dynamic range and robustness were established for the real time qPCR assays along with stability of the assay components. Cross validation of the real time PCR assays with CE-ELISA was performed by parallel testing of both serial dilutions of three different subtypes of cultured virus and a panel of influenza positive throat swab specimens. Results: the assays were specific for influenza A and B and the dynamic ranges were at least seven logs. The assay variability was within acceptable limits but increased towards the lower limit of quantification, which was 3.33 log10 viral cDNA copies/ml of virus transport medium (ten viral RNA copies/PCR). The components of the assay were robust enough to withstand extended storage and several freeze–thawcycles. For the real time PCR assays the limit of quantification was equivalent to the virus infectivity cut off, which equates to a 93-fold increase in sensitivity. Conclusion: Well characterised real time PCR assays offer significant improvements over the existing methods for measuring the viral load of strains of influenza A and B in clinical specimens
Switchable collective pinning of flux quanta using magnetic vortex arrays
We constructed a superconducting/ferromagnetic hybrid system in which the
ordering of the pinning potential landscape for flux quanta can be manipulated.
Flux pinning is induced by an array of magnetic nanodots in the magnetic vortex
state, and controlled by the magnetic history. This allows switching on and off
the collective pinning of the flux-lattice. In addition, we observed
field-induced superconductivity that originates from the annihilation of flux
quanta induced by the stray fields from the magnetic vortices.Comment: PDF file 18 pages including 5 figures, accepted for publication in
Phys. Rev.
Metastable bound state of a pair of two-dimensional spatially separated electrons in anti-parallel magnetic fields
We propose a new mechanism for binding of two equally charged carriers in a
double-layer system subjected by a magnetic field of a special form. A field
configuration for which the magnetic fields in adjacent layers are equal in
magnitude and opposite in direction is considered. In such a field an
additional integral of motion - the momentum of the pair P arises. For the case
when in one layer the carrier is in the zero (n=0) Landau level while in the
other layer - in the first (n=1) Landau level the dependence of the energy of
the pair on its momentum E(P} is found. This dependence turns out to be
nonmonotonic one : a local maximum and a local minimum appears, indicating the
emergence of a metastable bound state of two carrier with the same sign of
electrical charge.Comment: 7 page
Some remarks on D-branes and defects in Liouville and Toda field theories
In this paper we analyze the Cardy-Lewellen equation in general diagonal
model. We show that in these models it takes simple form due to some general
properties of conformal field theories, like pentagon equations and OPE
associativity. This implies, that the Cardy-Lewellen equation has simple form
also in non-rational diagonal models. We specialize our finding to the
Liouville and Toda field theories. In particular we prove, that conjectured
recently defects in Toda field theory indeed satisfy the cluster equation. We
also derive the Cardy-Lewellen equation in all Toda field theories and
prove that the forms of boundary states found recently in Toda field
theory hold in all theories as well.Comment: 30 pages, some comments, explanations and references adde
Superconducting tunneling-junction detectors of X-ray radiation. Issues concerning the energy resolution
Abstract -The effect of the recombination-and edge-related losses of nonequilibrium quasiparticles on the energy resolution of superconducting tunneling detectors is studied. The dependence of the signal on the energy of X-ray photons is measured and the shape of instrument-related lines is studied for the Ti/Nb/Al/AlO x /Al/Nb/NbN detectors with the Ti/Nb passive electrode. Experimental data are analyzed using the diffusion-based model of tunneling detectors
The CD100 Receptor Interacts with Its Plexin B2 Ligand to Regulate Epidermal γδ T Cell Function
Summaryγδ T cells respond rapidly to keratinocyte damage, providing essential contributions to the skin wound healing process. The molecular interactions regulating their response are unknown. Here, we identify a role for interaction of plexin B2 with the CD100 receptor in epithelial repair. In vitro blocking of plexin B2 or CD100 inhibited γδ T cell activation. Furthermore, CD100 deficiency in vivo resulted in delayed repair of cutaneous wounds due to a disrupted γδ T cell response to keratinocyte damage. Ligation of CD100 in γδ T cells induced cellular rounding via signals through ERK kinase and cofilin. Defects in this rounding process were evident in the absence of CD100-mediated signals, thereby providing a mechanistic explanation for the defective wound healing in CD100-deficient animals. The discovery of immune functions for plexin B2 and CD100 provides insight into the complex cell-cell interactions between epithelial resident γδ T cells and the neighboring cells they support
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