Random Scattering Matrices and the Circuit Theory of Andreev Conductances

The conductance of a normal-metal mesoscopic system in proximity to superconducting electrode(s) is calculated. The normal-metal part may have a general geometry, and is described as a ``circuit'' with ``leads'' and ``junctions''. The junctions are each ascribed a scattering matrix which is averaged over the circular orthogonal ensemble, using recently-developed techniques. The results for the electrical conductance reproduce and extend Nazarov's circuit theory, thus bridging between the scattering and the bulk approaches. The method is also applied to the heat conductance.Comment: 12 pages, RevTeX, including 2 figures with eps

Superconducting Proximity Effect and Universal Conductance Fluctuations

We examine universal conductance fluctuations (UCFs) in mesoscopic normal-superconducting-normal (N-S-N) structures using a numerical solution of the Bogoliubov - de Gennes equation. We discuss two cases depending on the presence (``open'' structure) or absence (``closed'' structure) of quasiparticle transmission. In contrast to N-S structures, where the onset of superconductivity increases fluctuations, we find that UCFs are suppressed by superconductivity for N-S-N structures. We demonstrate that the fluctuations in ``open'' and ``closed'' structures exhibit distinct responses to an applied magnetic field and to an imposed phase variation of the superconducting order parameter.Comment: (4 pages, 5 figures). Corrected typos in equations, added references, changed Fig. 5 and its discussions. Phys. Rev. B, accepted for publicatio

Giant Backscattering Peak in Angle-Resolved Andreev Reflection

It is shown analytically and by numerical simulation that the angular distribution of Andreev reflection by a disordered normal-metal -- superconductor junction has a narrow peak at the angle of incidence. The peak is higher than the well-known coherent backscattering peak in the normal state, by a large factor G/G_0 (where G is the conductance of the junction and G_0=2e^2/h). The enhanced backscattering can be detected by means of ballistic point contacts.Comment: Instituut-Lorentz, Leiden, The Netherlands, 4 pages, REVTeX-3.0, 3 figure

Medical graduates’ early career choices of specialty and their eventual specialty destinations: UK prospective cohort studies

Objective To report on doctors’ early choices of specialty at selected intervals after qualification, and eventual career destinations

Overcoming decoherence in the collapse and revival of spin Schr\"odinger cats

In addition to being a very interesting quantum phenomenon, Schr\"odinger cat swapping has the potential for application in the preparation of quantum states that could be used in metrology and other quantum processing. We study in detail the effects of field decoherence on a cat-swapping system comprising a set of identical qubits, or spins, all coupled to a field mode. We demonstrate that increasing the number of spins actually mitigates the effects of field decoherence on the collapse and revival of a spin Schr\"odinger cat, which could be of significant utility in quantum metrology and other quantum processing.Comment: 4 pages, 2 figure

Rapid Estimation of Binding Constants for Cucurbit[8]uril Ternary Complexes Using Electrochemistry

upramolecular complexes are of fundamental interests in biomedicines and adaptive materials, and thus facile methods to determine their binding affinity show usefulness in the design of novel drugs and materials. Herein, we report a novel approach to estimate the binding constants K_{G2} of cucurbit[8]uril-methyl viologen-based ternary complexes (CB8-MV^{2+}-G2) using electrochemistry, achieving high precision (±0.03) and practical accuracy (±0.32) in logKG2 and short measurement time ( 0.8) between the reduction potential of CB8-MV^{2+}-G2 ternary complexes and their reported binding constants from isothermal titration calorimetry, which allow a calibration curve to be plotted based on 25 sample complexes. Mechanistic investigation using experimental and computational approaches reveals that this correlation stems from the dynamic host-guest exchange events occurring after the electron transfer step. Binding constants of unknown ternary complexes, where G2 = hydrocarbons, were estimated, illustrating potential applications for sparsely soluble second guests

The Origin of Extreme Horizontal Branch Stars

Strong mass loss on the red giant branch (RGB) can result in the formation of extreme horizontal branch (EHB) stars. The EHB stars spend most of their He core and shell burning phase at high temperatures and produce copious ultraviolet flux. They have very small hydrogen envelopes and occupy a small range in mass. We have computed evolutionary RGB models with mass loss for stars with a range of metallicities at initial masses < 1.1 Msun corresponding to populations ages between 12.5 and 14.5 Gyr. We used the Reimers formula to characterize mass loss, but investigated a larger range of the mass loss efficiency parameter, eta, than is common. To understand how the number of EHB stars varies with metallicity in a stellar population we considered how the zero-age horizontal branch (ZAHB) is populated. The range in eta producing EHB stars is comparable to that producing `mid-HB' stars. Somewhat surprisingly, neither the range nor magnitude of eta producing EHB stars varies much metallicity. In contrast, the range of eta producing mid-HB stars decreases with increasing metallicity. Hence the HB of populations with solar metallicity and higher, such as expected in elliptical galaxies and spiral bulges, will be bimodal if the distribution covers a sufficiently large range in eta.Comment: AASLaTeX v.4, 29pp., postscript available at http://shemesh.gsfc.nasa.gov/~dorman/Ben.htm

Meta-analysis to evaluate the impact of the reduction of dietary crude protein on the gut health of post-weaning pigs

Weaning transition is often associated with the occurrence of the post-weaning diarrhoea syndrome (PWDS). The reduction of dietary crude protein (CP) has been intensively used as a strategy for controlling PWDS. The aim of the present meta-analysis was to report the effect of the reduction of dietary CP on the intestinal parameters related to the gut health, growth and diarrhoea of post-weaning piglets. A literature review of the articles published from 2006 to 2019 produced 48 articles and, of these 26 were selected. Parameters (bacterial metabolites, pH, microbiota diversity, intestinal morphology, inflammation markers, growth, faecal score) were extracted, expressed as a percentage of the control diet and analysed using a general linear model which included the study, reduction in points of dietary CP, and the ratio of digestible Lysine and dietary CP (dLys/CP) as factors. The reduction of dietary CP decreased ammonia (p &lt;.0001), pH (p =.039), total short-chain fatty acids (SCFAs) (p =.027), biogenic amines including cadaverine (p =.034) and putrescine (p =.030) and the expression of TLR4 (p &lt;.0001) in the intestine and also reduced the faecal score (p =.002). The dLys/CP ratio increased the level of Lactobacilli and the expression of TLR4 (p &lt;.05), and tended to increase acetic acid (p &lt;.1). Crypt depth, villus height, microbiota diversity and growth remained unchanged. In conclusion, this study confirmed that a reduction of dietary CP could reduce bacterial protein fermentation and the production of potentially toxic metabolites. In turn, this could result in lower intestinal inflammation and a decreased risk of diarrhoea in weaning piglets.Highlights Reducing the dietary crude protein can decrease the fermentation of undigested dietary protein, especially in the large intestine. Lowering undigested dietary protein results in a reduction of the intestinal pH and potentially toxic metabolites, including ammonia and amines. Diets with lower crude protein reduce inflammation of the intestinal mucosa and the post-weaning diarrhoea of piglets without compromising performance

Elemental Abundances of Solar Sibling Candidates

Dynamical information along with survey data on metallicity and in some cases age have been used recently by some authors to search for candidates of stars that were born in the cluster where the Sun formed. We have acquired high resolution, high signal-to-noise ratio spectra for 30 of these objects to determine, using detailed elemental abundance analysis, if they could be true solar siblings. Only two of the candidates are found to have solar chemical composition. Updated modeling of the stars' past orbits in a realistic Galactic potential reveals that one of them, HD162826, satisfies both chemical and dynamical conditions for being a sibling of the Sun. Measurements of rare-element abundances for this star further confirm its solar composition, with the only possible exception of Sm. Analysis of long-term high-precision radial velocity data rules out the presence of hot Jupiters and confirms that this star is not in a binary system. We find that chemical tagging does not necessarily benefit from studying as many elements as possible, but instead from identifying and carefully measuring the abundances of those elements which show large star-to-star scatter at a given metallicity. Future searches employing data products from ongoing massive astrometric and spectroscopic surveys can be optimized by acknowledging this fact.Comment: ApJ, in press. Tables 2 and 4 are available in full in the "Other formats: source" downloa