Confinement induced by fermion damping in three-dimensional QED

The three-dimensional non-compact QED is known to exhibit weak confinement when fermions acquire a finite mass via the mechanism of dynamical chiral symmetry breaking. In this paper, we study the effect of fermion damping caused by elastic scattering on the classical potential between fermions. By calculating the vacuum polarization function that incorporates the fermion damping effect, we show that fermion damping can induce a weak confinement even when the fermions are massless and the chiral symmetry is not broken.Comment: 4 pages, no figur

Field-effect mobility enhanced by tuning the Fermi level into the band gap of Bi2Se3

By eliminating normal fabrication processes, we preserve the bulk insulating state of calcium-doped Bi2Se3 single crystals in suspended nanodevices, as indicated by the activated temperature dependence of the resistivity at low temperatures. We perform low-energy electron beam irradiation (<16 keV) and electrostatic gating to control the carrier density and therefore the Fermi level position in the nanodevices. In slightly p-doped Bi2-xCaxSe3 devices, continuous tuning of the Fermi level from the bulk valence band to the band-gap reveals dramatic enhancement (> a factor of 10) in the field-effect mobility, which suggests suppressed backscattering expected for the Dirac fermion surface states in the gap of topological insulators

Metamagnetic Transition in Na0.85_{0.85}CoO2_2 Single Crystals

We report the magnetization, specific heat and transport measurements of high quality Na$_{0.85}$CoO$_2$ single crystals in applied magnetic fields up to 14T. In high temperatures, the system is in a paramagnetic phase. It undergoes a magnetic phase transition below about 20K. When the field is applied along the c-axis, the measurement data of magnetization, specific heat and magnetoresistance reveal a metamagnetic transition from an antiferromagnetic state to a quasi-ferromagnetic state at about 8T in low temperatures. However, no transition is observed in the magnetization measurements up to 14T when the field is applied perpendicular to the c-axis. The low temperature magnetic phase diagram of Na$_{0.85}$CoO$_2$ is determined.Comment: 4 pages, 5 figure

Optimal enterprise risk management and decision making with shared and dependent risks

Includes bibliographical references (pages 27-29).Published as: Journal of Risk and Insurance, vol. 84, no. 4, December 2017, pp. 1127–1169. https://doi.org/10.1111/jori.12140.Dynamic enterprise risk management (ERM) entails holistic decision-making for critical corporate functions such as capital budgeting and risk management. The interplay across business divisions, however, is complicated due to their natural interactions through the shared and dependent risk exposures within an intricate corporate structure. This paper develops an integrated optimization framework via a copula-based decision tree interface to facilitate ERM decision making to meet the specified enterprise goal in a multi-period setting. We illustrate our model and provide managerial insights with a case study for a financial services company engaged in both banking and insurance businesses

UNDERSTANDING THE COST ASSOCIATED WITH DATA SECURITY BREACHES

To estimate the cost of a data breach to the inflicted firm, this study examines the relationship between a breach incident and changes in the inflicted firm’s profitability, perceived risk, and the inflicted firms’ information environment transparency. Profitability is measured as reported earnings and analysts’ earnings forecasts. Perceived risk is measured as reported stock return volatility and dispersion among analysts’ forecasts. Although a number of studies have investigated the stock market reaction surrounding the disclosure of a breach incident to quantify the cost associated with breaches, we argue that there exists information uncertainty and deficiency in the disclosure of the breach incident and stock market reaction surrounding a security breach announcement date may not be the best measure for the cost of security breaches. And research using other complementary measures is warranted. Our preliminary finding suggests that data breaches negatively impact firm profitability, perceived risk and information transparency. Nevertheless, the damage of a breach most likely stems from direct costs such as compensation and litigation costs rather than indirect costs such as tarnished reputation and a decrease in market share and sales. More sophisticated analysts are also found to add value in estimating the real cost of a security breach

Graph based cross-shape recognition for palm diagnosis

Author name used in this publication: David ZhangBiometrics Research Centre, Department of ComputingVersion of RecordPublishe

Application of Orthogonal Design to Optimize Extraction of Polysaccharide from Cynomorium songaricum Rupr (Cynomoriaceae)

Purpose: To optimize the extraction technology of polysaccharides from Cynomorium songaricum Rupr by ultrasonic-assisted extraction (UAE).Methods: Four parameters including ultrasonic power, ratio of raw material to water, extraction temperature, and extraction time were optimized by orthogonal design. The effects of the factors on the yield of polysaccharides were also studied. The hydroxyl and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activities were determined in vitro by spectrophotometry.Results: The optimal conditions were as follows: 1:30 as ratio of raw material to water, extraction for 70 min at 80oC with ultrasonic power being 420 W. Under these conditions, the yield of polysaccharides was up to 4.51%, which was significantly higher than that obtained under the initial conditions (3.82 %). DPPH radical scavenging activity reached 64.82 % at 0.012 mg/mL, while hydroxyl radical scavenging activity was 18.36 % at 0.5 mg/mL.Conclusion: Ultrasonic-assisted extraction technology is a useful tool for the extraction of bioactive components from biological materials.Keywords: Cynomorium songaricum, Polysaccharide, Ultrasonic-assisted Extraction, Orthogonal Desig

Suspension and Measurement of Graphene and Bi2Se3 Atomic Membranes

Coupling high quality, suspended atomic membranes to specialized electrodes enables investigation of many novel phenomena, such as spin or Cooper pair transport in these two dimensional systems. However, many electrode materials are not stable in acids that are used to dissolve underlying substrates. Here we present a versatile and powerful multi-level lithographical technique to suspend atomic membranes, which can be applied to the vast majority of substrate, membrane and electrode materials. Using this technique, we fabricated suspended graphene devices with Al electrodes and mobility of 5500 cm^2/Vs. We also demonstrate, for the first time, fabrication and measurement of a free-standing thin Bi2Se3 membrane, which has low contact resistance to electrodes and a mobility of >~500 cm^2/Vs