Grand potential in thermodynamics of solid bodies and surfaces

Using the chemical potential of a solid in a dissolved state or the corresponding component of the chemical potential tensor at equilibrium with the solution, a new concept of grand thermodynamic potential for solids has been suggested. This allows generalizing the definition of Gibbs' quantity $\sigma$ (surface work often called the solid-fluid interfacial free energy) at a planar surface as an excess grand thermodynamic potential per unit surface area that (1) does not depend on the dividing surface location and (2) is common for fluids and solids.Comment: 6 page

Contact angles on a soft solid: from Young's law to Neumann's law

The contact angle that a liquid drop makes on a soft substrate does not obey the classical Young's relation, since the solid is deformed elastically by the action of the capillary forces. The finite elasticity of the solid also renders the contact angles different from that predicted by Neumann's law, which applies when the drop is floating on another liquid. Here we derive an elasto-capillary model for contact angles on a soft solid, by coupling a mean-field model for the molecular interactions to elasticity. We demonstrate that the limit of vanishing elastic modulus yields Neumann's law or a slight variation thereof, depending on the force transmission in the solid surface layer. The change in contact angle from the rigid limit (Young) to the soft limit (Neumann) appears when the length scale defined by the ratio of surface tension to elastic modulus $\gamma/E$ reaches a few molecular sizes

Depairing currents in superconducting films of Nb and amorphous MoGe

We report on measuring the depairing current J_{dp} in thin superconducting films as a function of temperature. The main difficulties in such measurements are that heating has to be avoided, either due to contacts, or to vortex flow. The latter is almost unavoidable since the sample cross-section is usually larger than the superconducting coherence length \xi_s and the magnetic field penetration depth \lambda_s. On the other hand, vortex flow is helpful since it homogenizes the distribution of the current across the sample. We used a pulsed current method, which allows to overcome the difficulties caused by dissipation and measured the depairing current in films of thin polycrystalline Nb (low \lambda_s, low specific resistance \rho) and amorphous Mo_{0.7}Ge_{0.3} (high \lambda_s, high \rho), structured in the shape of bridges of various width. The experimental values of J_{dp} for different bridge dimensions are compared with theoretical predictions by Kupriyanov and Lukichev for dirty limit superconductors. For the smallest samples we find a very good agreement with theory, over essentially the whole temperature interval below the superconducting critical temperature.Comment: 5 pages, 6 figure

Capillary pressure of van der Waals liquid nanodrops

The dependence of the surface tension on a nanodrop radius is important for the new-phase formation process. It is demonstrated that the famous Tolman formula is not unique and the size-dependence of the surface tension can distinct for different systems. The analysis is based on a relationship between the surface tension and disjoining pressure in nanodrops. It is shown that the van der Waals interactions do not affect the new-phase formation thermodynamics since the effect of the disjoining pressure and size-dependent component of the surface tension cancel each other.Comment: The paper is dedicated to the 80th anniversary of A.I. Rusano

Genotyping of Bulgarian Vitis vinifera L. cultivars by microsatellite analysis

A characterization of the Bulgarian grapevine genepool (Vitis vinifera L. cultivars) was initiated through microsatellite analysis. Seventy four wine and table grapevine varieties from the National List of Cultivars, were analyzed at 9 microsatellite loci: VVS2, ssrVvUCH11, ssrVvUCH 29, ssrVrZAG21, ssrVrZAG47, ssrVrZAG62, ssrVrZAG64, ssrVrZAG79 and ssrVrZAG83. The high genetic diversity (78 %) allowed accurate identification and discrimination of the cultivars. The low PI value (1.201 x 10-8) reflects the high discriminative power of the chosen set of markers for the investigated population. Based on the microsatellite allele data, two pairs of old native varieties, Misket Cherven and Misket Vrachanski; Tamyanka and Tamyanka tvarda, were considered distinct cultivars. The synonymy ofTamyanka, Italian Moscato Bianco and Greek Moschato Kerkyras andPamid and Greek Pamidi was verified, while the putative synonymy of Mavrud and Greek Mavroudi Arachovis was rejected.Further utilization of microsatellite profiling in the management of the Bulgarian grapevine genepool is discussed.

Unified description of fission in fusion and spallation reactions

We present a statistical-model description of fission, in the framework of compound-nucleus decay, which is found to simultaneously reproduce data from both heavy-ion-induced fusion reactions and proton-induced spallation reactions at around 1 GeV. For the spallation reactions, the initial compound-nucleus population is predicted by the Li\`{e}ge Intranuclear Cascade Model. We are able to reproduce experimental fission probabilities and fission-fragment mass distributions in both reactions types with the same parameter sets. However, no unique parameter set was obtained for the fission probability. The introduction of fission transients can be offset by an increase of the ratio of level-density parameters for the saddle-point and ground-state configurations. Changes to the finite-range fission barriers could be offset by a scaling of the Bohr-Wheeler decay width as predicted by Kramers. The parameter sets presented allow accurate prediction of fission probabilities for excitation energies up to 300 MeV and spins up to 60 \hbar.Comment: 16 pages, 20 figures. Submitted to Phys. Rev.

Sharp change over from compound nuclear fission to shape dependent quasi fission

Fission fragment mass distribution has been measured from the decay of $^{246}$Bk nucleus populating via two entrance channels with slight difference in mass asymmetries but belonging on either side of the Businaro Gallone mass asymmetry parameter. Both the target nuclei were deformed. Near the Coulomb barrier, at similar excitation energies the width of the fission fragment mass distribution was found to be drastically different for the $^{14}$N + $^{232}$Th reaction compared to the $^{11}$B + $^{235}$U reaction. The entrance channel mass asymmetry was found to affect the fusion process sharply.Comment: 4 pages,6 figure

Genetic diversity in native Bulgarian grapevine germplasm (Vitis vinifera L.) based on nuclear and chloroplast microsatellite polymorphisms

Fifty one wild specimens collected in different areas in Bulgaria and nineteen native Bulgarian grapevine cultivars were genotyped with 7 nuclear and 5 chloroplast SSR markers. Based on the microsatellite allelic profile six wild samples, collected from the Danube Riverbank, were considered non vinifera genotypes. The genetic diversity for nuclear loci observed in the cultivated grapevines was comparable to that found in other cultivated collections. However, lower genetic diversity was observed in the set of wild samples. The dendrogram based on nuclear SSRs separated most of the cultivated grapevines from the wild samples. Four chlorotypes corresponding to previously determined chlorotypes A, B, C and D, were identified in the analyzed samples that occurred with different frequencies in groups of wild and cultivated plants. The most frequent chlorotype among wild samples was A, while it was C in the cultivated samples. The differentiation of Bulgarian grape chlorotypes in the context of differentiation of chlorotypes in Eurasian grape flora is discussed.

First experiment on fission transients in highly fissile spherical nuclei produced by fragmentation of radioactive beams

We report on a novel experimental approach for studying the dissipative spreading of collective motion in a meta-stable nuclear system, using, for the first time, highly fissile nuclei with spherical shape. This was achieved by fragmentation of 45 radioactive heavy-ion beams at GSI, Darmstadt. The use of inverse kinematics and a dedicated experimental set-up allowed for the identification in atomic number of both fission fragments. From the width of their charge distributions, a transient time of (3.3 +/- 0.7) 10-21 s is deduced for initially spherical nuclei.Comment: 7 pages, 4 figures, background information at http://www-win.gsi.de/charms