Influence of dissipation on the prefactor in the expression of the decay rate of a metastable state

The influence of dissipation on the prefactor in the expression of the decay probability of a metastable state via macroscopic quantum tunneling is discussed. It is shown that under experimental conditions, because of the small number of levels in the well, such a correction is of paramount importance. Moreover, the full coincidence is shown between the expression of the decay probability derived from usual quantum mechanics and that obtained by the functional integral method in the limit of zero viscosity. The whole discussion, though of wide generality, is referred to a Josephson junction as a physical model, for which some conclusions of experimental interest are drawn.     

The relationship between the stressed state of metastable steels and phase transformations

An experimental investigation was carried out to establish the basic laws necessary to formulate a mathematical theory of the elastic-plastic deformation of alloys undergoing structural transformation under load.Translated from Fiziko-Khimischeskaya Mekhanika Materialov, Vol. 5, No. 5, pp. 542–547, September–October, 1969.     

Resonance reduction of the lifetime of the metastable state of tunnel junctions

The lifetime of a metastable current state of a tunnel junction is reduced under the action of a weak microwave perturbation. The dependence of the lifetime on pumping frequency is found and describes the experimental data. At a very highQ-factor, frequent sharp dips appear in the dependence of the lifetime on pumping frequency. These dips are connected with the quantum properties of the phase of the order parameter.     

Diffusion mechanism in the quantum decay of metastable3He-4He mixtures at low temperatures

We study the quantum phase-separation kinetics of a supersaturated liquid mixture at temperatures down to absolute zero. The energy dissipation effect of diffusion is incorporated into the calculation of the nucleation rate in normal and superfluid liquid mixtures. Unlike single-component systems, diffusion is the principal process which governs both the quantum nucleation rate and supercritical droplet growth rate in mixtures near the demixing curve. The low temperature phase-separation experiments in supersaturated liquid³He-⁴He mixtures of³He-dilute phase are analyzed and discussed. The critical degree of metastability and at the same time the critical droplet radius are shown to be temperature-independent below about 80 mK, suggesting the temperature of the thermal-to-quantum crossover to be of the same order of magnitude. The critical radius of a demixed droplet is estimated as about 20 Å, being within reasonable values.     

The theory of the growth of vapor bubbles in a metastable liquid

The growth of a single bubble and a system of vapor bubbles in the initial state in thermal and mechanical equilibrium with a liquid has been considered. Linear and nonlinear solutions have been derived, and the effects of the radial inertia, viscosity of the liquid, interphase heat and mass exchange, and the conditions of the tightness of bubbles on the development of the process have been studied on their basis.     

The theory of non-steady state fracture propagation rate

The classical concepts of the Tobolsky-Eyring theory of thermally activated bond breaking and mending mechanism were extended to describe fracture propagation at the molecular level. The analysis shows that the physical process which controls the propagation rate of cracks is described by a differential equation identical to the mathematical representation of the counterpart problems in heat transfer and diffusion.     

The ukrainian state standard for the liquid flow rate unit

Design and metrological characteristics are given for the Ukrainian state primary standard for the units of volume and mass liquid flow. __________ Translated from Izmeritel’naya Tekhnika, No. 6, pp. 39–45, June, 2007.     

Criterion for a balanced state of the heart rate regulating mechanism

Synthesized series of heart rate variability parameters are generated from digitized data for a series of R–R interval sequences on 433 electrocardiogram recordings for healthy young people. The results of preliminary analysis of the variability parameters using one of the recording series are generalized and applied to these synthesized series. Criteria are proposed for a balanced state of the heart rate regulating mechanism. Classification of the functional states on a four-point scale is confirmed and refined.     

The decay rate of critical fluctuations in3He-4He mixtures near the gas-liquid critical point

We have measured the critical light scattering intensity and the Rayleigh line shape for³He and for³He-⁴He mixtures with compositionX(³He)=0.95, 0.79, and 0.63 along their respective critical isochores near the plait point. The experimental linewidth of³He is compared with the calculated one from heat conductivity and equation of state measurements, and satisfactory agreement is obtained. For mixtures, gravity effects in our cell of finite height prevent us from reaching the critical point along a path at strictly constant composition and density. HenceT _c cannot be determined directly. Using the prediction that the scattered light intensity in the mixtures has the same diverging behavior as for the pure fluid, we determine the reduced temperaturet[T – T _c(X)]/T _c from the intensity. The measured Rayleigh line shape can be expressed by a single decay rate as a function oft for a given scattering angle of the light beam. Our experiments show that in the mixtures is only weakly dependent on composition. Our analysis leads to the determination of the mass diffusion coefficientD, which is found to be nearly independent of composition and nearly equal to the thermal diffusivityD _T measured for³He. The results are discussed in the light of the predictions from mode coupling theory.     

Nuclear spin lattice relaxation rate in the excitonic state

The nuclear spin lattice relaxation rate in the excitonic state is studied. Use is made of the two-band model, where the Fermi radii of the electron band and the hole band are assumed to be of the same size. It is important to distinguish two cases; the spin singlet case (i.e., the nonmagnetic excitonic state) and the spin triplet case (i.e., the antiferromagnetic state). In the case of the spin singlet excitonic state the nuclear spin lattice relaxation rate first increases in the excitonic state just below the transition temperature and then decreases rapidly as the temperature decreases. In the case of the spin triplet excitonic state the relaxation rate depends on whether the nuclear spin is polarized parallel or perpendicular to the spin-density wave describing the excitonic state. In the parallel case the relaxation rate decreases monotonically in the excitonic state as the temperature decreases, while in the transverse case it has a small peak just below the transition temperature.     

Dimple instability in a metastable superfluid film

It is shown that the surface dimple in a metastable rotating superfluid film becomes unstable as the surface spinodal of the thick film is approached. The dimple ceases to exist when its free energy E _d equals the excess free energy E _c of a critical hole in the film, which indicates the breakdown of the metastable film. The lifetime of the metastable film upon approach of the instability is calculated. Possibilities of enhancing the instability are briefly addressed.     

Spin exchange cross sections for collisions of metastable helium atoms with lithium atoms in the ground state

The spin exchange and chemi-ionization cross sections for the metastable helium atom-lithium atom in the ground state system have been calculated. Using data on the interaction potentials obtained in this study, the spin exchange cross sections are determined for the first time for the He(2³ S ₁)-Li(2² S _1/2) system in the interval of collision energies from 5 × 10^?3 to 16 eV.     

On the steady state of the replicating portfolio: accounting for a growth rate

For the risk management and transfer pricing of non-maturity liabilities, banks in Europe often use a so-called replicating portfolio technique. A commonly used implementation is replication of a fixed investment rule every time period. This paper deals with the development of the portfolio in the long run, when using this methodology. Applying this replicating portfolio technique yields, after a while, a steady state. Besides the straightforward result when volume is constant, we solve the steady states for the case where the funds (volume) grow with a fixed rate (e.g. due to credited interest or growth in GDP). We therefore define a system growth process, alternative to the Markov process (when volume is constant). From a transfer pricing and risk-management point of view, the resulting portfolio should satisfy certain requirements concerning return and flexibility. Once the steady state can be calculated for given growth rates, the investment policy can be specified. The importance of taking account of a growth rate is illustrated. Growth in volume implies that a different rule will converge to the desired steady state. This is illustrated analytically and with numerical examples. The purpose of the paper is not to find the ideal hedge strategy for non-maturity liabilities, but to improve the existing risk management without any implementation costs for the banks. Given the currently used methodology, accounting for a growth rate can significantly improve the risk management of non-maturity liabilities. RID="*" ID="*" I thank Anja De Waegenaere, Peter Kort and an anonymous referee for useful comments on an earlier draft.     

Strong enhancement of the radiative decay rate of emitters by single plasmonic nanoantennas

We demonstrate a strong, 5-fold enhancement of the radiative decay rate from highly efficient fluorescent dye molecules around resonant optical nanoantennas. The plasmonic modes of individual gold dimer antennas are tuned by the particle length and the antenna gap, providing control over both the spectral resonance position and the near-field mode profile of the nanoantenna. Resonant enhancement of the radiative and nonradiative decay rates of a fluorescent dye is observed, resulting in an increase of the internal quantum efficiency from 40% up to 53% for single antennas, and up to 59% for antenna clusters. This improvement of the already high quantum efficiency of the dye molecules is in agreement with electrodynamic model calculations that predict a maximum attainable efficiency around 80% due to nonradiative losses in the metal.     

The decay of suddenly blocked flow in a curved pipe

Pressure-driven viscous flow through a rigid curved pipe of uniform circular cross-section which is suddenly stopped, for example through the instantaneous closure of a valve, is considered here. The profile of the flow at early times after the stoppage is analysed asymptotically, by matching diffusive boundary layers to a core flow that is driven by an axial pressure gradient. This pressure gradient is unknown a priori and, furthermore, exhibits singular behaviour immediately after the stoppage. This analysis therefore provides the flow information at small but finite times that is required for numerical determination of the flow at later times. The limiting case of weak curvature is also considered, where linearization of the governing flow equations is possible. The results illustrate some novel features of the flow which result solely from the pipe’s curvature and the consequences for the flow’s rate of decay are discussed.     

Spin exchange rate constant for collisions of metastable helium atoms with rubidium atoms

The spin exchange rate constant C _se in the He(2³S₁)-Rb(5²S_1/2) system has been measured for the first time in experiments on the optical orientation of metastable helium atoms in the presence of rubidium atoms. In the temperature interval T = 293–348 K, this value is C _se = (1.8 ± 0.4) × 10^?9 cm³ s^?1. The chemiionization rate constant, which has been simultaneously measured in collisions of these particles, is C _ci = (3.1 ± 0.6) × 10^?9 cm³ s^?1.