Nernst effect as a probe of superconducting fluctuations in disordered thin films

In amorphous superconducting thin films of $Nb_{0.15}Si_{0.85}$ and $InO_x$, a finite Nernst coefficient can be detected in a wide range of temperature and magnetic field. Due to the negligible contribution of normal quasi-particles, superconducting fluctuations easily dominate the Nernst response in the entire range of study. In the vicinity of the critical temperature and in the zero-field limit, the magnitude of the signal is in quantitative agreement with what is theoretically expected for the Gaussian fluctuations of the superconducting order parameter. Even at higher temperatures and finite magnetic field, the Nernst coefficient is set by the size of superconducting fluctuations. The Nernst coefficient emerges as a direct probe of the ghost critical field, the normal-state mirror of the upper critical field. Moreover, upon leaving the normal state with fluctuating Cooper pairs, we show that the temperature evolution of the Nernst coefficient is different whether the system enters a vortex solid, a vortex liquid or a phase-fluctuating superconducting regime.Comment: Submitted to New. J. Phys. for a focus issue on "Superconductors with Exotic Symmetries

Influence of Environmental Conditions and Application of Cleaning Methods Against Biodeterioration of Marble Monuments

The aim of this paper is the study of the effect of environmental factors on the deterioration of marble monuments and the selection of a suitable and effective cleaning method. One of the main deterioration problems of the monuments is biodeterioration. It was obvious the presence of thick layers of biological patina, covering all almost surfaces of these. The growth of microorganisms, bacteria and plants is enhanced from the particular environmental conditions, that combine increased moisture, insolation and temperature, an area full of plants and trees and can cause extensive chemical and mechanical decay of the monuments. The growth of microorganisms, bacteria, plants and lichens was observed and determined. The influence of specific weathering agents and factors to the behavior of the materials was examined. The chemical composition of bulk precipitation and also the physicochemical characteristics of the surface and underground water were investigated. The environmental conditions and the growth of physical microorgamisms on the surface of the materials led to loss of the structural cohesion and the surface instability of the building materials. A series of various mechanical and chemical cleaning methods were tested in the laboratory containing the use of distilled water, microsandblast, organic solvents, absorbing clays, NH4HCO3 solution, biocides (desogen, hydrogen peroxide). In situ tests were carried out with satisfactory results in the monuments when a method of combination of hydrogen peroxide solutions, EDTA, NH4HCO3 solution and organic solvent was applied in various steps on the monument surface.Dept. of Chemistry, Aristotle University of Thessaloniki, Thessaloniki 54006 Greece, Dept. of Biology, University of Athens, Athens, Greece

Nernst effect in the phase-fluctuating superconductor InOx_x

We present a study of the Nernst effect in amorphous 2D superconductor InO$_x$, whose low carrier density implies low phase rigidity and strong superconducting phase fluctuations. Instead of presenting the abrupt jump expected at a BCS transition, the Nernst signal evolves continuously through the superconducting transition as previously observed in underdoped cuprates. This contrasts with the case of Nb$_{0.15}$Si$_{0.85}$, where the Nernst signal due to vortices below T$_{c}$ and by Gaussian fluctuations above are clearly distinct. The behavior of the ghost critical field in InO$_x$ points to a correlation length which does not diverge at $T_c$, a temperature below which the amplitude fluctuations freeze, but phase fluctuations survive.Comment: 4 pages, 4 figure

Use of Salivary Diurnal Cortisol as an Outcome Measure in Randomised Controlled Trials: a Systematic Review.

BACKGROUND: Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis is associated with diverse adverse health outcomes, making it an important therapeutic target. Measurement of the diurnal rhythm of cortisol secretion provides a window into this system. At present, no guidelines exist for the optimal use of this biomarker within randomised controlled trials (RCTs). PURPOSE: The aim of this study is to describe the ways in which salivary diurnal cortisol has been measured within RCTs of health or behavioural interventions in adults. METHODS: Six electronic databases (up to May 21, 2015) were systematically searched for RCTs which used salivary diurnal cortisol as an outcome measure to evaluate health or behavioural interventions in adults. A narrative synthesis was undertaken of the findings in relation to salivary cortisol methodology and outcomes. RESULTS: From 78 studies that fulfilled the inclusion criteria, 30 included healthy participants (38.5 %), 27 included patients with physical disease (34.6 %) and 21 included patients with psychiatric disease (26.9 %). Psychological therapies were most commonly evaluated (n = 33, 42.3 %). There was substantial heterogeneity across studies in relation to saliva collection protocols and reported cortisol parameters. Only 39 studies (50 %) calculated a rhythm parameter such as the diurnal slope or the cortisol awakening response (CAR). Patterns of change in cortisol parameters were inconsistent both within and across studies and there was low agreement with clinical findings. CONCLUSIONS: Salivary diurnal cortisol is measured inconsistently across RCTs, which is limiting the interpretation of findings within and across studies. This indicates a need for more validation work, along with consensus guidelines.Dr. Ryan is funded by a National Institute for Health Research (NIHR) Doctoral Research Fellowship Programme Award in the UK. The views expressed are those of the authors and not necessarily those of the National Health Service (NHS), the NIHR or the Department of Health.This is the final version of the article. It first appeared from Springer via https://doi.org/10.1007/s12160-015-9753-

Management Accountant's Role and Functions in the Enterprise Resource Planning Environment - Author's Own Research into Enterprises in Poland

This article seeks to answer whether the implementation of an ERP system has an effect on the management accountant's tasks and functions, especially in the field of performance measurement and internal reporting. The ERP impacts on the controller's role in the organization will be evaluated using field studies on six enterprises owned by multinational corporations. The question that should be asked here is whether controller's functions and tasks will also be unaffected.Celem badania jest próba odpowiedzi na pytanie czy zastosowanie zintegrowanego systemu informatycznego w przedsiębiorstwie zmienia zadania i funkcje specjalisty do spraw rachunkowości zarządczej. Na podstawie studium przypadku sześciu przedsiębiorstw będących częścią koncernów międzynarodowych zostaje dokonana ocena wpływu zastosowania ERP na rolę kontrolera w organizacji. Autor odpowiada również na pytanie czy w funkcjach i zadaniach kontrolera nie zaobserwowane zostaną zmiany w związku z implementacją ERP

Dzyaloshinskii-Moriya interaction in transport through single molecule transistors

The Dzyaloshinskii-Moriya interaction is shown to result in a canting of spins in a single molecule transistor. We predict non-linear transport signatures of this effect induced by spin-orbit coupling for the generic case of a molecular dimer. The conductance is calculated using a master equation and is found to exhibit a non-trivial dependence on the magnitude and direction of an external magnetic field. We show how three-terminal transport measurements allow for a determination of the coupling-vector characterizing the Dzyaloshinskii-Moriya interaction. In particular, we show how its orientation, defining the intramolecular spin chirality, can be probed with ferromagnetic electrodes

The Nernst effect and the boundaries of the Fermi liquid picture

Following the observation of an anomalous Nernst signal in cuprates, the Nernst effect was explored in a variety of metals and superconductors during the past few years. This paper reviews the results obtained during this exploration, focusing on the Nernst response of normal quasi-particles as opposed to the one generated by superconducting vortices or by short-lived Cooper pairs. Contrary to what has been often assumed, the so-called Sondheimer cancelation does not imply a negligible Nernst response in a Fermi liquid. In fact, the amplitude of the Nernst response measured in various metals in the low-temperature limit is scattered over six orders of magnitude. According to the data, this amplitude is roughly set by the ratio of electron mobility to Fermi energy in agreement with the implications of the semi-classical transport theory.Comment: Final version, Topical review for JPC

Material-specific gap function in the high-temperature superconductors

We present theoretical arguments and experimental support for the idea that high-Tc superconductivity can occur with s-wave, d-wave, or mixed-wave pairing in the context of a magnetic mechanism. The size and shape of the gap is different for different materials. The theoretical arguments are based on the t-J model as derived from the Hubbard model so that it necessarily includes three-site terms. We argue that this should be the basic minimal model for high-Tc systems. We analyze this model starting with the dilute limit which can be solved exactly, passing then to the Cooper problem which is numerically tractable, then ending with a mean field approach. It is found that the relative stability of s-wave and d-wave depends on the size and the shape of the Fermi surface. We identify three striking trends. First, materials with large next-nearest-neighbor hopping (such as YBa(2)Cu(3)O(7-x)) are nearly pure d-wave, whereas nearest-neighbor materials (such as La(2-x)Sr(x)CuO(4)) tend to be more s-wave-like. Second, low hole doping materials tend to be pure d-wave, but high hole doping leads to s-wave. Finally, the optimum hole doping level increases as the next-nearest-neighbor hopping increases. We examine the experimental evidence and find support for this idea that gap function in the high-temperature superconductors is material-specific.Comment: 20 pages; requires revtex.sty v3.0, epsf.sty; includes 6 EPS figures; Postscript version also available at http://lifshitz.physics.wisc.edu/www/koltenbah/papers/gapfunc2.ps . This version contains an extensive amount of new work including theoretical background, an additional mean field treatment with new figures, and a more thorough experimental surve

Joule-assisted silicidation for short-channel silicon nanowire devices

We report on a technique enabling electrical control of the contact silicidation process in silicon nanowire devices. Undoped silicon nanowires were contacted by pairs of nickel electrodes and each contact was selectively silicided by means of the Joule effect. By a realtime monitoring of the nanowire electrical resistance during the contact silicidation process we were able to fabricate nickel-silicide/silicon/nickel- silicide devices with controlled silicon channel length down to 8 nm.Comment: 6 pages, 4 figure

Multifunctional Devices and Logic Gates With Undoped Silicon Nanowires

We report on the electronic transport properties of multiple-gate devices fabricated from undoped silicon nanowires. Understanding and control of the relevant transport mechanisms was achieved by means of local electrostatic gating and temperature dependent measurements. The roles of the source/drain contacts and of the silicon channel could be independently evaluated and tuned. Wrap gates surrounding the silicide-silicon contact interfaces were proved to be effective in inducing a full suppression of the contact Schottky barriers, thereby enabling carrier injection down to liquid-helium temperature. By independently tuning the effective Schottky barrier heights, a variety of reconfigurable device functionalities could be obtained. In particular, the same nanowire device could be configured to work as a Schottky barrier transistor, a Schottky diode or a p-n diode with tunable polarities. This versatility was eventually exploited to realize a NAND logic gate with gain well above one.Comment: 6 pages, 5 figure