Process reconstruction from incomplete and/or inconsistent data

We analyze how an action of a qubit channel (map) can be estimated from the measured data that are incomplete or even inconsistent. That is, we consider situations when measurement statistics is insufficient to determine consistent probability distributions. As a consequence either the estimation (reconstruction) of the channel completely fails or it results in an unphysical channel (i.e., the corresponding map is not completely positive). We present a regularization procedure that allows us to derive physically reasonable estimates (approximations) of quantum channels. We illustrate our procedure on specific examples and we show that the procedure can be also used for a derivation of optimal approximations of operations that are forbidden by the laws of quantum mechanics (e.g., the universal NOT gate).Comment: 9pages, 5 figure

Linear force and moment equations for an annular smooth shaft seal perturbed both angularly and laterally

Coefficients are derived for equations expressing the lateral force and pitching moments associated with both planar translation and angular perturbations from a nominally centered rotating shaft with respect to a stationary seal. The coefficients for the lowest order and first derivative terms emerge as being significant and are of approximately the same order of magnitude as the fundamental coefficients derived by means of Black's equations. Second derivative, shear perturbation, and entrance coefficient variation effects are adjudged to be small

Achievable efficiencies for probabilistically cloning the states

We present an example of quantum computational tasks whose performance is enhanced if we distribute quantum information using quantum cloning. Furthermore we give achievable efficiencies for probabilistic cloning the quantum states used in implemented tasks for which cloning provides some enhancement in performance.Comment: 9 pages, 8 figure

Management of erectile dysfunction post-radical prostatectomy

© 2015 Saleh et al.Radical prostatectomy is a commonly performed procedure for the treatment of localized prostate cancer. One of the long-term complications is erectile dysfunction. There is little consensus on the optimal management; however, it is agreed that treatment must be prompt to prevent fibrosis and increase oxygenation of penile tissue. It is vital that patient expectations are discussed, a realistic time frame of treatment provided, and treatment started as close to the prostatectomy as possible. Current treatment regimens rely on phosphodiesterase 5 inhibitors as a first-line therapy, with vacuum erection devices and intraurethral suppositories of alprostadil as possible treatment combination options. With nonresponders to these therapies, intracavernosal injections are resorted to. As a final measure, patients undergo the highly invasive penile prosthesis implantation. There is no uniform, objective treatment program for erectile dysfunction post-radical prostatectomy. Management plans are based on poorly conducted and often underpowered studies in combination with physician and patient preferences. They involve the aforementioned drugs and treatment methods in different sequences and doses. Prospective treatments include dietary supplements and gene therapy, which have shown promise with there proposed mechanisms of improving erectile function but are yet to be applied successfully in human patients

Atomic level micromagnetic model of recording media switching at elevated temperatures

An atomic level micromagnetic model of granular recording media is developed and applied to examine external field-induced grain switching at elevated temperatures which captures non-uniform reversal modes. The results are compared with traditional methods which employ the Landau-Lifshitz-Gilbert equations based on uniformly magnetized grains with assigned intrinsic temperature profiles for $M(T)$ and $K(T)$. Using nominal parameters corresponding to high-anisotropy FePt-type media envisioned for Energy Assisted Magnetic Recording, our results demonstrate that atomic-level reversal slightly reduces the field required to switch grains at elevated temperatures, but results in larger fluctuations, when compared to a uniformly magnetized grain model.Comment: 4 pages, 5 figure

Micromagnetic simulations of sweep-rate dependent coercivity in perpendicular recording media

The results of micromagnetic simulations are presented which examine the impact of thermal fluctuations on sweep rate dependent coercivities of both single-layer and exchange-coupled-composite (ECC) perpendicular magnetic recording media. M-H loops are calculated at four temperatures and sweep rates spanning five decades with fields applied normal to the plane and at 45 degrees. The impact of interactions between grains is evaluated. The results indicate a significantly weaker sweep-rate dependence for ECC media suggesting more robustness to long-term thermal effects. Fitting the modeled results to Sharrock-like scaling proposed by Feng and Visscher [J. Appl. Phys. 95, 7043 (2004)] is successful only in the case of single-layer media with the field normal to the plane.Comment: 7 pages, 14 figure

About the screening of the charge of a proton migrating in a metal

The amount of screening of a proton in a metal, migrating under the influence of an applied electric field, is calculated using different theoretical formulations. First the lowest order screening expression derived by Sham (1975) is evaluated. In addition 'exact' expressions are evaluated which were derived according to different approaches. For a proton in a metal modeled as a jellium the screening appears to be 15 +/- 10 %, which is neither negligible not reconcilable with the controversial full-screening point of view of Bosvieux and Friedel (1962). In reconsidering the theory of electromigration, a new simplified linear-response expression for the driving force is shown to lead to essentially the same result as found by Sorbello (1985), who has used a rather complicated technique. The expressions allow for a reduction such that only the scattering phase shifts of the migrating impurity are required. Finally it is shown that the starting formula for the driving force of Bosvieux and Friedel leads exactly to the zero-temperature limit of well-established linear response descriptions, by which the sting of the controversy has been removed.Comment: 14 pages, 5 figure

Periodic homogenization of a pseudo-parabolic equation via a spatial-temporal decomposition

Pseudo-parabolic equations have been used to model unsaturated fluid flow in porous media. In this paper it is shown how a pseudo-parabolic equation can be upscaled when using a spatio-temporal decomposition employed in the Peszyn'ska-Showalter-Yi paper [8]. The spatial-temporal decomposition transforms the pseudo-parabolic equation into a system containing an elliptic partial differential equation and a temporal ordinary differential equation. To strengthen our argument, the pseudo-parabolic equation has been given advection/convection/drift terms. The upscaling is done with the technique of periodic homogenization via two-scale convergence. The well-posedness of the extended pseudo-parabolic equation is shown as well. Moreover, we argue that under certain conditions, a non-local-in-time term arises from the elimination of an unknown.Comment: 6 pages, 0 figure