Shape-Resonant Superconductivity in Nanofilms: from Weak to Strong Coupling

Ultrathin superconductors of different materials are becoming a powerful platform to find mechanisms for enhancement of superconductivity, exploiting shape resonances in different superconducting properties. Here, we evaluate the superconducting gap and its spatial profile, the multiple gap components, and the chemical potential, of generic superconducting nanofilms, considering the pairing attraction and its energy scale as tunable parameters, from weak to strong coupling, at fixed electron density. Superconducting properties are evaluated at mean field level as a function of the thickness of the nanofilm, in order to characterize the shape resonances in the superconducting gap. We find that the most pronounced shape resonances are generated for weakly coupled superconductors, while approaching the strong coupling regime the shape resonances are rounded by a mixing of the subbands due to the large energy gaps extending over large energy scales. Finally, we find that the spatial profile, transverse to the nanofilm, of the superconducting gap acquires a flat behavior in the shape resonance region, indicating that a robust and uniform multigap superconducting state can arise at resonance.     

Influence of dietary vitamin C and selenium,alone and in combination,on the composition and oxidative stability of meat of broilers

Information on the combined effect of dietary vitamin C and Se on the composition and oxidative stability of meat of broilers is not available in the literature. In the present experiment, male broiler chickens were fed a maize–wheat–soya diet supplemented with vitamin C at 280 and 560 mg/kg of diet, and Se (sodium selenite or selenised yeast; Se) at 0.3 mg/kg for 5 weeks. After slaughter, samples of thigh meat were analysed. The supplementation of diets with vitamin C or Se increased the protein concentration of the meat at the expense of fat. Vitamin C supplementation increased the vitamin C content of the meat in a dose-dependent manner and decreased the vitamin A concentration in the meat of broilers fed diets with sodium selenite or without a Se supplement. In the meat of the broilers that were fed these diets, the vitamin C decreased the lipid oxidation in meat that was stored for 5 days. No sparing effect of vitamin C was apparent on the amount of vitamin E in the meat. Selenised yeast was more effective in the enrichment of meat with Se than was selenite. Both Se sources increased the activity of glutathione peroxidase and the oxidative stability of the meat.     

Influence of Disorder on Superconducting Correlations in Nanoparticles

We investigate how the interplay of quantum confinement and level broadening caused by disorder affects superconducting correlations in ultra-small metallic grains. We use the electron-phonon interaction-induced electron mass renormalization and the reduced static-path approximation of the BCS formalism to calculate the critical temperature as a function of the grain size. We show how the strong electron-impurity scattering additionally smears the peak structure in the electronic density of states of a metallic grain and imposes additional limits on the critical temperature under strong quantum confinement.     

Sulfobutylation of Beta-Cyclodextrin Enhances the Complex Formation with Mitragynine: An NMR and Chiroptical Study

Mitragynine (MTR), the main indole alkaloid of the well-known plant kratom (Mitragyna speciosa), is one of the most studied natural products nowadays, due to its remarkable biological effects. It is a partial agonist on the opioid receptors, and as such relieves pain without the well-known side-effects of the opioids applied in the clinical practice. MTR and its derivatives therefore became novel candidates for drug development. The poor aqueous solubility and low bioavailability of drugs are often improved by cyclodextrins (CyDs) as excipients through host-guest type complex formation. Among the wide variety of CyDs, sulfobutylether-beta-cyclodextrin (SBEβCyD) is frequently used and official in the European and U.S. Pharmacopoeia. Herein, the host-guest complexation of MTR with βCyD and SBEβCyD was studied using chiroptical and NMR spectroscopy. It was found by NMR measurements that MTR forms a rather weak (logβ₁₁ = 0.8) 1:1 host-guest complex with βCyD, while the co-existence of the 2MTR∙SBEβCyD and MTR∙SBEβCyD species was deducted from ¹H NMR titrations in the millimolar MTR concentration range. Sulfobutylation of βCyD significantly enhanced the affinity towards MTR. The structure of the formed inclusion complex was extensively studied by circular dichroism spectroscopy and 2D ROESY NMR. The insertion of the indole moiety was confirmed by both techniques.     

Crystallography and Morphology of Niobium Carbide in As-Cast HP-Niobium Reformer Tubes

The microstructures of two as-cast heats of niobium-modified HP stainless steels were characterized. Particular attention was paid to the interdendritic niobium-rich carbides formed during solidification of these alloys. At low magnifications, these precipitates are grouped in colonies of similar lamellae. Higher magnifications revealed that the lamellae actually obtain two distinct morphologies. The type I morphology exhibits broad planar interfaces with a smooth platelike shape. Type II lamellae have undulating interfaces and an overall reticulated shape. To provide further insight into the origin of these two different morphologies, the microstructure and crystallography of each have been studied in detail using high resolution scanning electron microscopy, transmission electron microscopy, various electron diffraction methods (electron backscatter diffraction (EBSD), selected area diffraction (SAD), and convergent beam electron diffraction (CBED)), and energy dispersive X-ray spectroscopy.     

A conundrum in molecular toxicology: molecular and biological changes during neoplastic transformation of human cells

The process of multistage carcinogenesis lends itself to the concept that the effects of carcinogens are mediated through dose-related, multi-hit, linear changes. Multiple in vitro model systems have been developed that are designed to examine the cellular changes associated with the progression of cells through the different stages in the process; however, these systems may have inherent limitations due to the cell lines used for these studies, the manner of assessing the effects of the carcinogens, and the subsequent growth and differentiation of the exposed cells. Each of these variables results in increasing levels of uncertainty relative to the correlation of the events with the actual process of human tumor development. Therefore, the prediction of the ultimate effect of any carcinogen is difficult. Moreover, relationships between individual biological endpoints resulting from carcinogen treatment appear at best to be approximations. The presence of an activated carcinogen inside the cell can give rise to multiple outcomes, only some of which may be critical events. For example, site-specific modification of the 12th and 13th codons of H-ras is different than that in the adjacent 14th and 15th codons. It is interesting to speculate what effect these differences might have on a biological outcome, e.g., transformation to anchorage-independent growth. The use of different model systems to examine the effects of activated carcinogens also creates additional problems. Comparisons of in vitro transformed cells with similar cells isolated from human tumors indicate that the culture environment appears to influence the expression of a particular phenotype, in that human tumor cells in culture express many of the same parameters as those found in cells transformed with carcinogens in vitro. If the process of transformation is linear, then less aggressive phenotypes should progress to a more aggressive transformed stage. However, in carcinogen-transformed human cells, the populations exhibit phenotypic diversity in that many of the transformed cells differentiate and fail to continue to divide in culture. Historically, we have assumed only a limited role for epigenetic modulation of molecular changes that occur during progression; however, our data suggest quite strongly that nonmalignant tumor populations can be converted to a more malignant phenotype without additional mutations taking place and, conversely, malignant populations can be downregulated to a nontumorigenic phenotype. Tumor cell plasticity is not only a fundamental characteristic of diverse types of human tumors, but also appears as an integral characteristic of carcinogen-transformed cells in vitro.     

Number and position of visual stimuli as determinants of reaction time in schizophrenia.

Notes that RT in normal Ss has been shown to be linearly related to stimulus complexity, defined as the log of the number of equally probable stimuli to which a response may be made. Data from an earlier study of 40 short- and long-term paranoid and nonparanoid male schizophrenics and 10 male hospital employees were reanalyzed and compared with P. Venable's (see record 1959-10789-001) study of schizophrenic deficit. Although experimental procedures were dissimilar, both studies found that increased complexity did not result in schizophrenics having steeper regression slopes than normal Ss. Consideration of the position of the critical stimulus, however, clearly indicated that long-term, nonparanoid schizophrenics narrow attention to central cues when confronted by an increase in complexity. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Computation of steady and time-dependent temperature distribution for building elements: A general three-dimensional solution

A computational method of temperature distribution calculation for building elements in two- and three-dimensional time-dependent heat flow problems is developed with a general approximate solution using, as a numerical approach, the finite difference method. An analytical evaluation method of the accuracy of calculations is developed. The method described was compared with experimental values and good correspondence was obtained. The time-dependent study which is presented includes thermal resistance and inertia (heat capacity) of the components' materials and different geometric compositions.     

Symbolic target detection in SAR imagery via rotationally invariant-weighted feature extraction

This article introduces the application of a physics-based symbolic image partitioning method to detect targets in synthetic aperture radar (SAR) imagery. ‘Targets’ in this case refer to vehicular objects which produce a distinct radar return pattern, and have spatial characteristics that are known a priori. The proposed Rotationally Invariant Symbolic Histogram (RISH) detection method co-analyses both target and speckle statistics, and significantly reduces computational requirements by partitioning the data into a discrete number of state representations. RISH requires only one pass for robust detection, unlike other SAR detection methods which rely on difference metrics calculated using multiple passes. To improve performance in high-resolution data, RISH uses a weighted feature extraction algorithm to avoid the common requirement of processing each pixel of the image equally. The weighted structure extracts geometrically undefined and rotationally invariant target features. This article details the analysis of 24 experimentally obtained very high-frequency (VHF)-band SAR magnitude images using this novel approach to SAR target detection. In localizing small (~8.4 m²) foliage-concealed targets, without the aid of pre-processing, this method results in high performance characteristics (90% true positive) with a low Type-II error rate of 6.4 false alarms per 1 × 10⁶ m². With the addition of change detection, RISH lowers the error rate by 85%.