The shape evolution of cometary nuclei via anisotropic mass loss

Context. Breathtaking imagery recorded during the European Space Agency's Rosetta mission confirmed the bilobate nature of comet 67P/Churyumov-Gerasimenko's nucleus. Its peculiar appearance is not unique among comets. The majority of cometary cores imaged at high resolution exhibit a similar build. Various theories have been brought forward as to how cometary nuclei attain such peculiar shapes. Aims. We illustrate that anisotropic mass loss and local collapse of subsurface structures caused by non-uniform exposure of the nucleus to solar irradiation can transform initially spherical comet cores into bilobed ones. Methods. A mathematical framework to describe the changes in morphology resulting from non-uniform insolation during a nucleus' spin-orbit evolution is derived. The resulting partial differential equations that govern the change in the shape of a nucleus subject to mass loss and consequent collapse of depleted subsurface structures are solved analytically for simple insolation configurations and numerically for more realistic scenarios. Results. The here proposed mechanism is capable of explaining why a large fraction of periodic comets appear to have peanut-shaped cores and why light-curve amplitudes of comet nuclei are on average larger than those of typical main belt asteroids of the same size.Comment: 4 pages of the main text, 2 pages of appendix, 4 figure

Pulsed thermal NDT in tables, figures and formulas

Several reviews and summary papers describing the history and the current status of pulsed thermal nondestructiv

Vacuum Cherenkov radiation

Within the classical Maxwell-Chern-Simons limit of the Standard-Model Extension (SME), the emission of light by uniformly moving charges is studied confirming the possibility of a Cherenkov-type effect. In this context, the exact radiation rate for charged magnetic point dipoles is determined and found in agreement with a phase-space estimate under certain assumptions.Comment: 4 pages, REVTeX

A novel data processing algorithm in thermal property measurement and defect detection by using one-sided active infrared thermography

The proposed algorithm is based on the analysis of an artificial front-surface pixel-based function which include

Interplay of paramagnetic, orbital and impurity effects on the phase transition of a normal metal to superconducting state

We derive the generalized Ginzburg-Landau free energy functional for conventional and unconventional singlet superconductors in the presence of paramagnetic, orbital and impurity effects. Within the mean field theory, we determine the criterion for appearence of the non uniform (Fulde-Ferrell-Larkin-Ovchinnikov) superconducting state, with vortex lattice structure and additional modulation along the magnetic field. We also discuss the possible change of the order of transition from normal to superconducting state. We find that the superconducting phase diagram is very sensitive to geometrical effects such as the nature of the order parameter and the shape of the Fermi surface. In particular, we obtain the qualitative phase diagrams for three-dimensional isotropic s-wave superconductors and in quasi two-dimensional d-wave superconductors under magnetic field perpendicular to the conducting layers. In addition, we determine the criterion for instability toward non uniform superconducting state in s-wave superconductors in the dirty limit.Comment: 15 pages, 4 figure

Spectroscopic analysis of finite size effects around a Kondo quantum dot

We consider a simple setup in which a small quantum dot is strongly connected to a finite size box. This box can be either a metallic box or a finite size quantum wire.The formation of the Kondo screening cloud in the box strongly depends on the ratio between the Kondo temperature and the box level spacing. By weakly connecting two metallic reservoirs to the quantum dot, a detailed spectroscopic analysis can be performed. Since the transport channels and the screening channels are almost decoupled, such a setup allows an easier access to the measure of finite-size effects associated with the finite extension of the Kondo cloud.Comment: contribution to Les Houches proceeding, ``Quantum magnetism'' 200

Stochastic dynamics of magnetization in a ferromagnetic nanoparticle out of equilibrium

We consider a small metallic particle (quantum dot) where ferromagnetism arises as a consequence of Stoner instability. When the particle is connected to electrodes, exchange of electrons between the particle and the electrodes leads to a temperature- and bias-driven Brownian motion of the direction of the particle magnetization. Under certain conditions this Brownian motion is described by the stochastic Landau-Lifshitz-Gilbert equation. As an example of its application, we calculate the frequency-dependent magnetic susceptibility of the particle in a constant external magnetic field, which is relevant for ferromagnetic resonance measurements.Comment: 15 pages, 6 figure

Study of the immunoglobulin and oxidized protein content of semen under infertility

Among the causes of male infertility, enough attention is paid to oxidative stress, which in turn is a pathogenetic link in the inflammatory process. However, there is practically no information on the content of oxidized modified proteins in the semen, which makes it difficult to study the pathogenesis of diseases of the male reproductive system. In part, protein oxidation may be due to the production of reactive oxygen species by microorganisms, both directly and indirectly through the activation of immune system cells. The aim of the research was to study the level of oxidized modified proteins and changes in immunoglobulin concentrations in the semen under bacteriospermia. A study was made of the ejaculate of 48 men who applied to the clinic for infertility in marriage. The comparison group consisted of 32 practically healthy men who had no growth of microorganisms in the ejaculate samples. When conducting bacteriological analysis, the studied samples were diluted 10 times and used the generally accepted method. The concentration of albumin, immunoglobulins A, M, G, E was determined in the spermatic fluid. The oxidative modification of proteins was evaluated in the reaction with 2,4-dinitrophenylhydrazine. The concentration of oxidized proteins was expressed in nmol/mg of the total protein of the studied biological fluid. The biuret method was used to determine the protein concentration. Statistical analysis of the results was performed using descriptive statistics and Student's t-test for paired data. The concentration of protein in the seminal fluid did not differ significantly among the studied groups. The albumin concentration (16.96±1.28 mg/mL) was statistically significantly lower in the absence of microorganism growth than in bacteriospermia. With bacteriospermia, a decrease in the concentration of IgM and IgA and an increase in the level of IgG were noted. The degree of protein oxidation is maximum when enterobacteria are isolated from seminal fluid. Thus, during the studies it was found that, despite the absence of a clinic, with asymptomatic bacteriospermia, the secretion of immunoglobulins G into the semen is observed. The accumulation of oxidized proteins in the seminal fluid in bacteriospermia has been shown