Superconductivity and Magnetism in REFeAsO1-xFx (RE=Rare Earth Elements)

Fluoride-doped iron-based oxypnictides containing rare-earth gadolinium (GdFeAsO0.8F0.2) and co-doping with yttrium (Gd0.8Y0.2FeAsO0.8F0.2) have been prepared via conventional solid state reaction at ambient pressure. The non-yttrium substituted oxypnictide show superconducting transition as high as 43.9 K from temperature dependent resistance measurements with the Meissner effect observed at a lower temperature of 40.8 K from temperature dependent magnetization measurements. By replacing a small amount of gadolinium with yttrium Tc was observed to be lowered by 10 K which might be caused by a change in the electronic or magnetic structures since the crystal structure was not altered.Comment: 4 pages, 4 figures, Journal of Physics: Conference Series (Proceedings in the LT25 Low Temperature Physics Conference) Submitte

Trailing Edge Noise Reduction by Passive and Active Flow Controls

This paper presents the results on the use of porous metal foams (passive control) and dielectric barrier surface plasma actuations (active control) for the reduction of vortex shedding tonal noises from the nonflat plate type trailing edge serration in a NACA0012 airfoil previously discussed in Chong et al. (AIAA J. Vol. 51, 2013, pp. 2665-2677). The use of porous metal foams to fill the interstices between adjacent members of the sawtooth can almost completely suppress the vortex shedding tonal noise, whilst the serration effect on the broadband noise reduction is retained. This concept will promote the nonflat plate type serrated trailing edge to become a genuine alternative to the conventional flat plate type serrated trailing edge, which is known to have drawbacks in the structural stability, aerodynamic performances and implementation issues. For the plasma actuators, configuration which produces electric wind in a tangential direction is found to be not very effective in suppressing the vortices emanated from the serration blunt root. On the other hand, for the plasma configuration which produces electric wind in a vertical direction, good level of vortex shedding tonal noise reduction has been demonstrated. However, the self noise produced by the plasma actuators negates the noise benefits on the tonal noise reduction. This characteristic illustrates the need to further develop the plasma actuators in a two pronged approach. First is to increase the electric wind speed, thereby allowing the plasma actuators to be used in a higher free jet velocity which naturally produces a larger level of jet noise. Second, the self noise radiated by the plasma actuators should be reduced

Operational approach to the Uhlmann holonomy

We suggest a physical interpretation of the Uhlmann amplitude of a density operator. Given this interpretation we propose an operational approach to obtain the Uhlmann condition for parallelity. This allows us to realize parallel transport along a sequence of density operators by an iterative preparation procedure. At the final step the resulting Uhlmann holonomy can be determined via interferometric measurements.Comment: Added material, references, and journal reference

Steady-state Ab Initio Laser Theory: Generalizations and Analytic Results

We improve the steady-state ab initio laser theory (SALT) of Tureci et al. by expressing its fundamental self-consistent equation in a basis set of threshold constant flux states that contains the exact threshold lasing mode. For cavities with non-uniform index and/or non-uniform gain, the new basis set allows the steady-state lasing properties to be computed with much greater efficiency. This formulation of the SALT can be solved in the single-pole approximation, which gives the intensities and thresholds, including the effects of nonlinear hole-burning interactions to all orders, with negligible computational effort. The approximation yields a number of analytic predictions, including a "gain-clamping" transition at which strong modal interactions suppress all higher modes. We show that the single-pole approximation agrees well with exact SALT calculations, particularly for high-Q cavities. Within this range of validity, it provides an extraordinarily efficient technique for modeling realistic and complex lasers.Comment: 17 pages, 11 figure

Imaging Orbital-selective Quasiparticles in the Hund's Metal State of FeSe

Strong electronic correlations, emerging from the parent Mott insulator phase, are key to copper-based high temperature superconductivity (HTS). By contrast, the parent phase of iron-based HTS is never a correlated insulator. But this distinction may be deceptive because Fe has five active d-orbitals while Cu has only one. In theory, such orbital multiplicity can generate a Hund's Metal state, in which alignment of the Fe spins suppresses inter-orbital fluctuations producing orbitally selective strong correlations. The spectral weights $Z_m$ of quasiparticles associated with different Fe orbitals m should then be radically different. Here we use quasiparticle scattering interference resolved by orbital content to explore these predictions in FeSe. Signatures of strong, orbitally selective differences of quasiparticle $Z_m$ appear on all detectable bands over a wide energy range. Further, the quasiparticle interference amplitudes reveal that $Z_{xy}<Z_{xz}<<Z_{yz}$, consistent with earlier orbital-selective Cooper pairing studies. Thus, orbital-selective strong correlations dominate the parent state of iron-based HTS in FeSe.Comment: for movie M1, see http://www.physik.uni-leipzig.de/~kreisel/osqp/M1.mp4, for movie M2, see http://www.physik.uni-leipzig.de/~kreisel/osqp/M2.mp4, for movie M3, see http://www.physik.uni-leipzig.de/~kreisel/osqp/M3.mp4, for movie M4, see http://www.physik.uni-leipzig.de/~kreisel/osqp/M4.mp4, for movie M5, see http://www.physik.uni-leipzig.de/~kreisel/osqp/M5.mp

Supersymmetric QCD corrections to single top quark production at hadron colliders

We present the calculations of the supersymmetric QCD corrections to the total cross sections for single top production at the Fermilab Tevatron and the CERN Large Hadron Collider in the minimal supersymmetric standard model. Our results show that for the s-channel and t-channel, the supersymmetric QCD corrections are at most about 1%, but for the associated production process, the supersymmetric QCD corrections increase the total cross sections significantly, which can reach about 6% for most values of the parameters, and the supersymmetric QCD corrections should be taken into consideration in the future high precision experimental analysis for top physics.Comment: 33 pages, 19 figures, version to appear in Phys.Rev.

Comparative effects of castration and dehorning in series or concurrent castration and dehorning procedures on stress responses and production in Holstein calves

The study objective was to compare serum cortisol as an acute stress measure, chute exit velocity as a behavioral measure, and ADG as an indicator of performance and well-being after castration, dehorning, or concurrent castration/dehorning of calves when performed in parallel and in series. Intact male Holstein calves, 3 to 4 mo, underwent sham handling before 2 procedures performed in series separated by 2 to 3 wk. In Period 1, calves were either dehorned by amputation, surgically castrated, concurrently castrated/dehorned, or served as nonsurgical controls (n = 10/treatment). In Period 2, calves that had been dehorned, castrated, or castrated/dehorned were then castrated, dehorned, or served as nonsurgical controls, respectively. Indicators of distress were measured after all procedures; ADG was assessed for 7 d after each procedure and over the 2 to 3 wk interim. Period 1 cortisol concentrations in dehorned calves were less than in castrated and castrated/dehorned calves at 120 min and from 50 to 240 min, respectively (P \u3c 0.02). There was marginal evidence that cortisol concentrations were greater in castrated/dehorned than castrated calves at 60 min (P = 0.06). Period 2 cortisol concentrations were less in dehorned than castrated calves at 120 min (P = 0.005) but were greater from 360 to 480 min (P \u3c 0.002). The Period 2 cortisol profile of control calves did not differ from the baseline obtained during sham handling, despite the intervening castration/dehorning in Period 1, suggesting that memory did not affect cortisol. The cortisol profile of castrated calves did not differ between periods except at 720 min, when Period 1 concentrations were greater than Period 2 (P = 0.02). Cortisol concentrations of calves dehorned in Period 2 were greater than those dehorned in Period 1 at 20 and 240 to 480 min (P \u3c 0.05). In both periods, castrated calves exited the chute slower than dehorned calves (P \u3c 0.05). The ADG did not differ between surgically treated calves in Period 1; in the interim, the ADG of castrated calves was greater than that of castrated/dehorned calves (difference ± SED, 1.4 ± 0.6 kg/d; P = 0.03), and in Period 2, the ADG of dehorned calves was less than castrated calves (1.8 ± 0.6 kg/d; P = 0.005). Our study supports both the common practice of concurrent castration/dehorning and the sequence of dehorning and castration. Delayed dehorning (vs. delayed castration) appeared to be more acutely stressful and more detrimental to ADG

How do junior medical officers use online information resources? A survey

Background: Online information resources function dually as important learning tools and sources of the latest evidence-based recommendations for junior medical officers (JMOs). However, little is currently known about how JMOs utilise this information when providing care for their patients. This study aimed to examine the usage and experience of online information resources amongst JMOs in South Australia to ascertain (i) the type of resources accessed, (ii) the frequency, (iii) the intended purpose, and (iv) the perceived reliability. Methods: A survey instrument using multiple choices, five-point Likert scales and free-text comments was developed and distributed through SurveyMonkey to South Australian JMOs between 1 May 2014 and 30 June 2014. Results: Of the 142 surveyed, 100 JMOs (70.4 %) used online information resources as their first approach over all other resources available. JMOs overwhelmingly (94.4 %, n = 134) used online information resources at least once per day, with the most frequent purpose for use being information regarding prescription medication (82.4 %, n = 117, reported ‘very frequent’ use). JMOs stated online resources were necessary to perform their work and, of the different types of information accessed, they rated peer-reviewed resources as the most reliable. Conclusions: JMOs strongly rely upon online clinical information in their everyday practice. Importantly, provision of these resources assists JMOs in their education and clinical performance.Heng Teck Chong, Michael James Weightman, Peranada Sirichai and Alison Jone

A 16 x 16 CMOS amperometric microelectrode array for simultaneous electrochemical measurements

There is a requirement for an electrochemical sensor technology capable of making multivariate measurements in environmental, healthcare, and manufacturing applications. Here, we present a new device that is highly parallelized with an excellent bandwidth. For the first time, electrochemical cross-talk for a chip-based sensor is defined and characterized. The new CMOS electrochemical sensor chip is capable of simultaneously taking multiple, independent electroanalytical measurements. The chip is structured as an electrochemical cell microarray, comprised of a microelectrode array connected to embedded self-contained potentiostats. Speed and sensitivity are essential in dynamic variable electrochemical systems. Owing to the parallel function of the system, rapid data collection is possible while maintaining an appropriately low-scan rate. By performing multiple, simultaneous cyclic voltammetry scans in each of the electrochemical cells on the chip surface, we are able to show (with a cell-to-cell pitch of 456 μm) that the signal cross-talk is only 12% between nearest neighbors in a ferrocene rich solution. The system opens up the possibility to use multiple independently controlled electrochemical sensors on a single chip for applications in DNA sensing, medical diagnostics, environmental sensing, the food industry, neuronal sensing, and drug discovery