A model of an optical biosensor detecting environment

Heller et. Al. (Science 311, 508 (2006)) demonstrated the first DNA-CN optical sensor by wrapping a piece of double-stranded DNA around the surface of single-walled carbon nanotubes (CN). This new type of optical device can be placed inside living cells and detect trace amounts of harmful contaminants by means of near infrared light. Using a simple exciton theory in nanostructures and the phenomena of B-Z structural phase transition of DNA, we investigate the working principle of this new class of optical biosensor from DNA by using the nanostructure surface as a sensor to detect the property change of DNA as it responds to the presence of target ions. We also propose some new design models by replacing carbon nanotubes with graphene ribbon semiconductors.Comment: 4 pages, 4 figures, Accepte

Spin-chirality decoupling in the one-dimensional Heisenberg spin glass with long-range power-law interactions

We study the issue of the spin-chirality decoupling/coupling in the ordering of the Heisenberg spin glass by performing large-scale Monte Carlo simulations on a one-dimensional Heisenberg spin-glass model with a long-range power-law interaction up to large system sizes. We find that the spin-chirality decoupling occurs for an intermediate range of the power-law exponent. Implications to the corresponding $d$-dimensional short-range model is discussed.Comment: 5 pages, 4 figures, to appear in Physical Review Letter

Differences in delivery of prehospital ambulance care comparing non-white versus white patients with suspected cardiac chest pain: cross-sectional study

Introduction Quality implies equitable care irrespective of ethnicity. There have been few previous studies investigating quality of prehospital cardiac care by ethnicity. We aimed to investigate whether prehospital care for suspected cardiac pain varied by ethnicity. Methods We conducted a cross-sectional analysis of retrospective electronic clinical data for patients with chest pain over one year (August 2011 to July 2012) extracted from a single regional ambulance service. This included patient demographic data (ethnicity, age, sex, deprivation), clinical measurements (blood pressure, respiratory rate, pain assessment, temperature, blood glucose, oxygen saturation), drugs (aspirin, nitroglycerin, Entonox, morphine) and outcomes such as transportation to hospital or referral to primary care. We used multivariate regression to investigate differences in care by ethnicity comparing non-white with white patients. Results There were 7046 patients with suspected cardiac chest pain, with 4825 who had ethnicity recorded including 4661 (96.6%) white, 164 (3.4%) non-white (2221 patients had missing data for ethnicity). Non-white patients were similar in sex (p=0.63) and socioeconomic group (p=0.07) but significantly younger in age (p<0.001) than white patients. After correcting for age, sex, socioeconomic status and whether transported to hospital, non-white patients were similar to white patients in recording of blood pressure, pain score or electrocardiogram but significantly more likely to have temperature (77.4 vs.69.8%), blood glucose (78.7 vs. 69.4%), and oxygen saturation (85.4 vs. 80.7%) recorded. There were no differences in aspirin, nitroglycerin, Entonox or morphine treatment but non-white patients were less likely than white patients to be transported to hospital (93.3 vs. 94.4, p=0.02). Conclusion We found differences in prehospital ambulance care for non-white compared with white patients with cardiac pain that could be due to recording bias, varying clinical condition or provider management. Further analysis should involve larger and more complete datasets to explore ethnic differences in greater detail

Monte Carlo studies of the chiral and spin orderings of the three-dimensional Heisenberg spin glass

The nature of the ordering of the three-dimensional isotropic Heisenberg spin glass with nearest-neighbor random Gaussian coupling is studied by extensive Monte Carlo simulations. Several independent physical quantities are measured both for the spin and for the chirality, including the correlation-length ratio, the Binder ratio, the glass order parameter, the overlap distribution function and the non-self-averageness parameter. By controlling the effect of the correction-to-scaling, we have obtained a numerical evidence for the occurrence of successive chiral-glass and spin-glass transitions at nonzero temperatures, T_{CG} > T_{SG} > 0. Hence, the spin and the chirality are decoupled in the ordering of the model. The chiral-glass exponents are estimated to be \nu_{CG}=1.4+-0.2 and \eta_{CG}=0.6+-0.2, indicating that the chiral-glass transition lies in a universality class different from that of the Ising spin glass. The possibility that the spin and chiral sectors undergo a simultaneous Kosterlitz-Thouless-type transition is ruled out. The chiral-glass state turns out to be non-self-averaging, possibly accompanying a one-step-like peculiar replica-symmetry breaking. Implications to the chirality scenario of experimental spin-glass transitions are discussed.Comment: 20 pages, 24 figures. The Chi^2-analysis of the transition point has been added with new Fig.12. Some references also adde

Insider trading, gender diversity within the board room, CEO pay gap, and stock price crash risk

This paper investigates the impact of insider trading and managerial attributes on future stock price crashes. We conduct a series of regressions addressing the managerial attributes determinants of future stock price crashes including gender diversity, CEO age, and CEO power (measured by CEO pay disparity, CEO tenure and CEO duality). Our empirical results reveal a positive association between insider purchases and price crash risk. This implies that other than compensation and career concerns, insiders hoard bad news to fulfil their trading incentives. Our positive coefficients of insider sales also suggest that insider sellers can assess inside information promptly and anticipate shortly before the crashes. We further document that the presence of female directors on boards can mitigate stock price crash risk. However, firms with powerful or younger Chief Executive Officers are more likely to experience crashes. Overall, we highlight the importance of corporate managerial attributes in dealing with information asymmetry problems