A spectral scheme for Kohn-Sham density functional theory of clusters

Starting from the observation that one of the most successful methods for solving the Kohn-Sham equations for periodic systems -- the plane-wave method -- is a spectral method based on eigenfunction expansion, we formulate a spectral method designed towards solving the Kohn-Sham equations for clusters. This allows for efficient calculation of the electronic structure of clusters (and molecules) with high accuracy and systematic convergence properties without the need for any artificial periodicity. The basis functions in this method form a complete orthonormal set and are expressible in terms of spherical harmonics and spherical Bessel functions. Computation of the occupied eigenstates of the discretized Kohn-Sham Hamiltonian is carried out using a combination of preconditioned block eigensolvers and Chebyshev polynomial filter accelerated subspace iterations. Several algorithmic and computational aspects of the method, including computation of the electrostatics terms and parallelization are discussed. We have implemented these methods and algorithms into an efficient and reliable package called ClusterES (Cluster Electronic Structure). A variety of benchmark calculations employing local and non-local pseudopotentials are carried out using our package and the results are compared to the literature. Convergence properties of the basis set are discussed through numerical examples. Computations involving large systems that contain thousands of electrons are demonstrated to highlight the efficacy of our methodology. The use of our method to study clusters with arbitrary point group symmetries is briefly discussed.Comment: Manuscript submitted (with revisions) to Journal of Computational Physic

Impacts of the criminalization on the everyday lives of people living in with HIV in Canada

As part of a study on the social consequences of the criminal justice system on people living with HIV or AIDS (PHAs) in Canada, this article focuses on how heightened public identification of HIV with criminal matters is having wide ranging effects on perceived personal security and in particular on negotiating potential romantic and sexual interactions. As articulated by the Supreme Court of Canada, the courts have been enforcing a requirement that HIV-positive people disclose their sero-status to prospective partners, relying on the notion that “through deterrence it [the Criminal Code] will protect and serve to encourage honesty, frankness and safer sexual practices.” Nevertheless an accumulating set of evidence in the social and health sciences is pointing toward the difficulties of carrying out this directive in everyday life and toward the ways in which the application of law creates counter-productive or unanticipated consequences that can run contrary to the ostensible objective of discouraging behaviour likely to transmit HIV

Effects of the criminalization of HIV transmission in Cuerrier on men reporting unprotected sex with men

This paper reports on the perceptions and practices of men who have frequent unprotected sex with men in a socio-legal environment defined by the 1998 decision of the Supreme Court of Canada in R. v. Cuerrier. HIV-positive people are increasingly finding themselves in court since Cuerrier and many are trying to take account of legal reasoning in their own conduct. The judicial construction of behaviour likely to transmit HIV relies on a set of presumptions concerning individual responsibility, rational and contractual interaction, and consenting adults that raise a series of ambiguities and uncertainties among HIV-positive people attempting to implement them in everyday life. While some express support for the reasoning in Cuerrier, others struggle with practical dilemmas in sexual interaction, and a minority strand of ethical reasoning advances a “buyer beware” principle. This latter view occurs in a social environment where HIV-positive people experience strong disincentives to disclose in the face of potential rejection or discrimination once their sero-status is known. Examination of the social consequences of Cuerrier raises questions about the viability of relying on the enforcement of disclosure, through threat of criminal prosecution, as an effective method of HIV prevention, especially when most practical, day-to-day HIV prevention occurs when safer sex is practised consistently regardless of disclosure

Indoor visible light communication localization system utilizing received signal strength indication technique and trilateration method

Visible light communication (VLC) based on light-emitting diodes (LEDs) technology not only provides higher data rate for indoor wireless communications and offering room illumination but also has the potential for indoor localization. VLC-based indoor positioning using the received optical power levels from emitting LEDs is investigated. We consider both scenarios of line-of-sight (LOS) and LOS with non-LOS (LOSNLOS) positioning. The performance of the proposed system is evaluated under both noisy and noiseless channel as is the impact of different location codes on positioning error. The analytical model of the system with noise and the corresponding numerical evaluation for a range of signal-to-noise ratio (SNR) are presented. The results show that an accuracy of 12 dB

HIVpositive people\u27s perspectives on Canadian criminal law and non-disclosure

The largest survey to date of people living with HIV regarding attitudes toward criminalization of HIV non-disclosure, this study investigates: sources of legal information available to HIV-positive people; perceptions of how criminal prosecutions and media coverage affect understanding of rights and responsibilities of self and others; and where HIV-positive people themselves stand on the role the criminal justice system should play. While mainstream media constructions of criminal iconography do affect PHA views, those who have higher levels of formal education, are active in the dating scene, and have been living longer with HIV hold less punitive views than those who do not. While the overall pattern of agreement on where to draw the line in criminal prosecution holds regardless of demographic characteristics, there is some statistically significant variation in degree of punitiveness according to sexual orientation and gender as well

Spectral and picosecond temporal properties of flared guide Y‐coupled phase‐locked laser arrays

Spatio‐spectral and spatio‐temporal properties of flared waveguide ‘‘Y’’‐coupled laser arrays are investigated in both cw and pulsed operation. In each case, regular sustained self‐pulsations are exhibited. Destabilization of phase locking, caused by amplitude phase coupling, is thought to be the origin of the pulsations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70525/2/APPLAB-53-24-2380-1.pd

Soil biocrusts affect metabolic response to hydration on dunes in west Queensland, Australia

Soil biocrusts, formed from communities of microbes and their extracellular products are a common feature of dryland soil surfaces. Biocrust organisms are only intermittently metabolically active, but due to their ubiquity they make a significant contribution to the carbon cycle. Quantification of the controls and insights into the interlinked process of photosynthesis and respiration are essential to enhancing our understanding of the carbon cycle in the world’s drylands. Yet, there have been relatively few field studies investigating controls on both biocrust photosynthesis and respiration. We undertook field-based experiments at two dune sites during the dry season in Diamantina National Park in Queensland, Australia to determine how biocrust hydration and illumination affect soil CO2 flux and photosynthesis. Static chambers and an infra-red gas analyser were used to quantify soil CO2 flux, and a fluorometer and a CFImager were used to determine a range of photosynthetic parameters in the field and laboratory respectively. When dry, biocrust photosynthetic activity was not detected and soil CO2 flux was very low irrespective of biocrust cover. Hydration led to a large and immediate increase in CO2 flux, which was more pronounced in the presence of biocrusts and on the dune with thinner biocrusts. Hydration also initiated the onset of photosynthesis in some biocrusts, which was greatest under low light conditions and sustained with further hydration. There were only infrequent periods of net CO2 uptake to the soil, occurring when CO2 uptake due to photosynthetic activity was less than background soil CO2 flux. Chlorophyll fluorescence imaging indicated biocrust spatial heterogeneity was evident at the cm scale where microtopography creates a myriad of environments for different crust organisms. Our findings demonstrate that biocrusts are highly spatially heterogenetic at both landscape and small scale, which suggests the maintenance of biocrust spatial diversity is likely to be key to imparting resilience to changing climate and disturbance. As well as reaffirming the importance of biocrusts for the carbon cycle in dryland dune soils the study demonstrates that biocrust respiration and photosynthesis respond differently to hydration and shading. This adds an unpredictability to the distribution of soil carbon stocks and the gaseous exchanges of CO2 between the surface and atmosphere. Future changes to precipitation and increased temperatures are likely to reduce soil moisture across much of the Australian interior and consequently biocrusts may experience a decline in biomass, structure, and function which could have significant repercussions beyond carbon stocks.Natural Environment Research Counci

Weak evidence of bright light effects on human LH and FSH

<p>Abstract</p> <p>Background</p> <p>Most mammals are seasonal breeders whose gonads grow to anticipate reproduction in the spring and summer. As day length increases, secretion increases for two gonadotropins, luteinizing hormone (LH) and follicle stimulating hormone (FSH). This response is largely controlled by light. Light effects on gonadotropins are mediated through effects on the suprachiasmatic nucleus and responses of the circadian system. There is some evidence that seasonal breeding in humans is regulated by similar mechanisms, and that light stimulates LH secretion, but primate responses seem complex.</p> <p>Methods</p> <p>To gain further information on effects of bright light on LH and FSH secretion in humans, we analyzed urine samples collected in three experiments conducted for other goals. First, volunteers ages 18-30 years and 60-75 commenced an ultra-short 90-min sleep-wake cycle, during which they were exposed to 3000 lux light for 3 hours at balanced times of day, repeated for 3 days. Urine samples were assayed to explore any LH phase response curve. Second, depressed participants 60-79 years of age were treated with bright light or dim placebo light for 28 days, with measurements of urinary LH and FSH before and after treatment. Third, women of ages 20-45 years with premenstrual dysphoric disorder (PMDD) were treated to one 3-hour exposure of morning light, measuring LH and FSH in urine before and after the treatments.</p> <p>Results</p> <p>Two of the three studies showed significant increases in LH after light treatment, and FSH also tended to increase, but there were no significant contrasts with parallel placebo treatments and no significant time-of-day treatment effects.</p> <p>Conclusions</p> <p>These results gave some support for the hypothesis that bright light may augment LH secretion. Longer-duration studies may be needed to clarify the effects of light on human LH and FSH.</p