Itinerant-electron Ferromagnetism in W(Nb)O3-d

The crystal structure and the magnetic properties of the W1-xNbxO3-d, (x<0.03) system have been investigated. In contrast to the orthorhombic diamagnetic WO3, the material with x=0.01 is paramagnetic down to 5 K. Introducing of 2.5 at. % of Nb into WO3 leads to a tetragonal structure and to a weak itinerant ferromagnetic ordering below TC= 225 K. The saturation magnetic moment at 5 K is 1.07*10-3 mB, whereas the paramagnetic effective moment is 0.06 mB per mole. This high ratio indicates itinerant ferromagnetism in W0.975Nb0.025O3-d.Comment: accepted to Physica

Specific heat studies of pure Nb3Sn single crystals at low temperature

Specific heat measurements performed on high purity vapor-grown Nb$_3$Sn crystals show clear features related to both the martensitic and superconducting transitions. Our measurements indicate that the martensitic anomaly does not display hysteresis, meaning that the martensitic transition could be a weak first or a second order thermodynamic transition. Careful measurements of the two transition temperatures display an inverse correlation between both temperatures. At low temperature specific heat measurements show the existence of a single superconducting energy gap feature.Comment: Accepted in Journal of Physics: Condensed Matte

Arithmetic properties of blocks of consecutive integers

This paper provides a survey of results on the greatest prime factor, the number of distinct prime factors, the greatest squarefree factor and the greatest m-th powerfree part of a block of consecutive integers, both without any assumption and under assumption of the abc-conjecture. Finally we prove that the explicit abc-conjecture implies the Erd\H{o}s-Woods conjecture for each k>2.Comment: A slightly corrected and extended version of a paper which will appear in January 2017 in the book From Arithmetic to Zeta-functions published by Springe

Stripes, Non-Fermi-Liquid Behavior, and High-Tc Superconductivity

The electronic structure of the high-Tc cuprates is studied in terms of "large-U" and "small-U" orbitals. A striped structure and three types of quasiparticles are obtained, polaron-like "stripons" carrying charge, "svivons" carrying spin, and "quasielectrons" carrying both. The anomalous properties are explained, and specifically the behavior of the resistivity, Hall constant, and thermoelectric power. High-temperature superconductivity results from transitions between pair states of quasielectrons and stripons.Comment: 4 page

Xenosurveillance reflects traditional sampling techniques for the identification of human pathogens: A comparative study in West Africa

BACKGROUND: Novel surveillance strategies are needed to detect the rapid and continuous emergence of infectious disease agents. Ideally, new sampling strategies should be simple to implement, technologically uncomplicated, and applicable to areas where emergence events are known to occur. To this end, xenosurveillance is a technique that makes use of blood collected by hematophagous arthropods to monitor and identify vertebrate pathogens. Mosquitoes are largely ubiquitous animals that often exist in sizable populations. As well, many domestic or peridomestic species of mosquitoes will preferentially take blood-meals from humans, making them a unique and largely untapped reservoir to collect human blood. METHODOLOGY/PRINCIPAL FINDINGS: We sought to take advantage of this phenomenon by systematically collecting blood-fed mosquitoes during a field trail in Northern Liberia to determine whether pathogen sequences from blood engorged mosquitoes accurately mirror those obtained directly from humans. Specifically, blood was collected from humans via finger-stick and by aspirating bloodfed mosquitoes from the inside of houses. Shotgun metagenomic sequencing of RNA and DNA derived from these specimens was performed to detect pathogen sequences. Samples obtained from xenosurveillance and from finger-stick blood collection produced a similar number and quality of reads aligning to two human viruses, GB virus C and hepatitis B virus. CONCLUSIONS/SIGNIFICANCE: This study represents the first systematic comparison between xenosurveillance and more traditional sampling methodologies, while also demonstrating the viability of xenosurveillance as a tool to sample human blood for circulating pathogens

Quantum Mechanics of Multi-Prong Potentials

We describe the bound state and scattering properties of a quantum mechanical particle in a scalar $N$-prong potential. Such a study is of special interest since these situations are intermediate between one and two dimensions. The energy levels for the special case of $N$ identical prongs exhibit an alternating pattern of non-degeneracy and $(N-1)$ fold degeneracy. It is shown that the techniques of supersymmetric quantum mechanics can be used to generate new solutions. Solutions for prongs of arbitrary lengths are developed. Discussions of tunneling in $N$-well potentials and of scattering for piecewise constant potentials are given. Since our treatment is for general values of $N$, the results can be studied in the large $N$ limit. A somewhat surprising result is that a free particle incident on an $N$-prong vertex undergoes continuously increased backscattering as the number of prongs is increased.Comment: 17 pages. LATEX. On request, TOP_DRAW files or hard copies available for 7 figure

Transformation of in-plane ρ(T)\rho (T) in YBa2Cu3O7−δYBa_{2}Cu_{3}O_{7-\delta} at fixed oxygen content

This paper reveals the origin of variation in the magnitude and temperature dependence of the normal state resistivity frequently observed in different YBCO single crystal or thin film samples with the same $T_{c}$. We investigated temperature dependence of resistivity in $YBa_{2}Cu_{3}O_{7-\delta}$ thin films with 7- $\delta = 6.95$ and 6.90, which were subjected to annealing in argon at 400-420 K ($120-140^{o}C$). Before annealing these films exhibited a non-linear $\rho_{ab}(T)$, with a flattening below 230 K, similar to $\rho_{b}(T)$ and $\rho_{ab}(T)$ observed in untwinned and twinned YBCO crystals, respectively. For all films the annealing causes an increase of resistivity and a transformation of $\rho_{ab}(T)$ from a non-linear dependence towards a more linear one (less flattening). In films with 7- $\delta = 6.90$ the increase of resistivity is also associated with an increase in $T_{c}$. We proposed the model that provides an explanation of these phenomena in terms of thermally activated redistribution of residual O(5) oxygens in the chain-layer of YBCO. Good agreement between the experimental data for $\rho_{ab}(t,T)$, where t is the annealing time, and numerical calculations was obtained.Comment: 8 pages, 9 figures, submitted to PR

До мінералогії сезонних сульфатів мису Фіолент (Південно-Західний Крим)

Комплексом методів вивчено колекцію зразків вторинних мінералів одного з узбережних відслонень зони окиснення сульфідної мінералізації мису Фіолент (Південно-Західний Крим). Установлено, що всі досліджені зразки є полімінеральними утвореннями, в яких одночасно співіснують у різних пропорціях сульфати Mg, Al, Fe²⁺, Fe³⁺, Ca тощо: пікерингіт (найпоширеніший), пікерингіт залізистий, гексагідрит, старкіїт, епсоміт, алуноген, ботріоген, копіапіт, ярозит, гіпс та ін. Старкіїт і ботріоген у Криму виявлено вперше.The collection of secondary minerals from one of littoral occurrences of sulphide zone of oxidation of the Fiolent Cape (South-Western Crimea) is studied by different methods. It was established that all studied samples were polymineral formations which consisted of sulphates of Mg, Al, Fe²⁺, Fe³⁺, Ca, etc. in different proportions: pickeringite (the most wide-spread), ferropickeringite, hexahydrite, starkeyite, epsomite, alunogen, botryogen, copiapite, jarosite, gypsum etc. Starkeyite and botryogen are detected in the Crimea for the first time

Role of Interfaces in the Proximity Effect in Anisotropic Superconductors

We report measurements of the critical temperature of YBCO-Co doped YBCO Superconductor-Normal bilayer films. Depending on the morphology of the S-N interface, the coupling between S and N layers can be turned on to depress the critical temperature of S by tens of degrees, or turned down so the layers appear almost totally decoupled. This novel effect can be explained by the mechanism of quasiparticle transmission into an anisotropic superconductor.Comment: 13 pages, 3 figure