Topological Phase Transitions and Holonomies in the Dimer Model

We demonstrate that the classical dimer model defined on a toroidal hexagonal lattice acquires holonomy phases in the thermodynamic limit. When all activities are equal the lattice sizes must be considered mod 6 in which case the finite size corrections to the bulk partition function correspond to a massless Dirac Fermion in the presence of a flat connection with nontrivial holonomy. For general bond activities we find that the phase transition in this model is a topological one, where the torus degenerates and its modular parameter becomes real at the critical temperature. We argue that these features are generic to bipartite dimer models and we present a more general lattice whose continuum partition function is that of a massive Dirac Fermion.Comment: 7 pages, 4 figures. Minor corrections with additional figure

Measuring the Size, Scope & Scale of the Social Enterprise Sector in Manitoba

This project surveyed social enterprises in Manitoba during the spring and summer of 2011 to develop clear indicators of their size, market activities, and socio‐economic contributions. In this study, a social enterprise is defined as a business venture, owned or operated by a nonprofit organization that sells goods or provides services in the market to create a blended return on investment; financial, social, environmental, and cultural. Using this definition, researchers identified 266 operating social enterprises in Manitoba. Of the 266 social enterprises that received the survey, 118 responded. Indicators of socio‐economic contribution included sales and revenue, expenditures, employment, volunteer engagement, and clients served and trained. Respondents were asked to report results of the 2010 financial year. The following report is a summary of the survey findings. Prior to revealing the survey findings, this paper provides a brief history of the innovative approaches to community economic development that have been used in Manitoba. The province’s roots in community‐based economic models laid the foundation for Manitoba’s current social enterprises, which are found to be a diverse sector, composed of businesses meeting a range of poverty reduction, social, cultural or environmental goals. The survey results suggest that in 2010, the 118 responding social enterprises generated at least $55.4 million in cumulative revenue, including at least$41.5 million generated through sales. Responding social enterprises paid at least $25.3 million in salaries and wages to 3,752 people, of whom 3,450 were employed as part of the mission of the organization. We estimate that Manitoba social enterprises paid, on average, just over$20,000 in wages and salary per full‐time equivalent employee. Additionally, social enterprises trained 6,890 individuals, generated 5,870 volunteer opportunities, and provided services to an average of 4,200 people. This paper builds a strong case for stakeholders, community, funder, and government, to collaboratively value these distinct contributions and to support hospitable environments for social enterprises.BC‐Alberta Social Economy Research Alliance (BALTA), Canadian Community Economic Development Network (CCEDNet), Manitoba Social Enterprise Working Group, Assiniboine Credit Union, United Way of Winnipeg, Social Sciences and Humanities Research Council of Canada, Mount Royal Universit

Stochastic formulation of the renormalization group: supersymmetric structure and topology of the space of couplings

The exact or Wilson renormalization group equations can be formulated as a functional Fokker-Planck equation in the infinite-dimensional configuration space of a field theory, suggesting a stochastic process in the space of couplings. Indeed, the ordinary renormalization group differential equations can be supplemented with noise, making them into stochastic Langevin equations. Furthermore, if the renormalization group is a gradient flow, the space of couplings can be endowed with a supersymmetric structure a la Parisi-Sourlas. The formulation of the renormalization group as supersymmetric quantum mechanics is useful for analysing the topology of the space of couplings by means of Morse theory. We present simple examples with one or two couplings.Comment: 13 pages, based on contribution to "Progress in Supersymmetric Quantum Mechanics" (Valladolid U.), accepted in Journal of Physics

Low-level mixing height detection in coastal locations with a scanning Doppler lidar

Mixing layer height (MLH) is one of the key parameters in describing lower tropospheric dynamics and capturing its diurnal variability is crucial, especially for interpreting surface observations. In this paper we introduce a method for identifying MLH below the minimum range of a scanning Doppler lidar when operated at vertical. The method we propose is based on velocity variance in low-elevation-angle conical scanning and is applied to measurements in two very different coastal environments: Limassol, Cyprus, during summer and Loviisa, Finland, during winter. At both locations, the new method agrees well with MLH derived from turbulent kinetic energy dissipation rate profiles obtained from vertically pointing measurements. The low-level scanning routine frequently indicated non-zero MLH less than 100 m above the surface. Such low MLHs were more common in wintertime Loviisa on the Baltic Sea coast than during summertime in Mediterranean Limassol

Field Theory Entropy, the HH-theorem and the Renormalization Group

We consider entropy and relative entropy in Field theory and establish relevant monotonicity properties with respect to the couplings. The relative entropy in a field theory with a hierarchy of renormalization group fixed points ranks the fixed points, the lowest relative entropy being assigned to the highest multicritical point. We argue that as a consequence of a generalized $H$ theorem Wilsonian RG flows induce an increase in entropy and propose the relative entropy as the natural quantity which increases from one fixed point to another in more than two dimensions.Comment: 25 pages, plain TeX (macros included), 6 ps figures. Addition in title. Entropy of cutoff Gaussian model modified in section 4 to avoid a divergence. Therefore, last figure modified. Other minor changes to improve readability. Version to appear in Phys. Rev.

Calculation of energy levels and transition amplitudes for barium and radium

The radium atom is a promising system for studying parity and time invariance violating weak interactions. However, available experimental spectroscopic data for radium is insufficient for designing an optimal experimental setup. We calculate the energy levels and transition amplitudes for radium states of significant interest. Forty states corresponding to all possible configurations consisting of the $7s$, $7p$ and $6d$ single-electron states as well as the states of the $7s8s$, $7s8p$ and $7s7d$ configurations have been calculated. The energies of ten of these states corresponding to the $6d^2$, $7s8s$, $7p^2$, and $6d7p$ configurations are not known from experiment. Calculations for barium are used to control the accuracy.Comment: 12 pages, 4 table

Against the Odds: Psychomotor Development of Children Under 2 years in a Sudanese Orphanage.

Providing abandoned children the necessary medical and psychological care as possible after their institutionalization may minimize developmental delays. We describe psychomotor development in infants admitted to an orphanage in Khartoum, Sudan, assessed at admission and over an 18-month follow-up. Psychological state and psychomotor quotients were determined using a simplified Neonatal Behavior Assessment Scale (NBAS), the Brunet-Lezine and Alarm distress baby (ADBB) scale. From May-September 2005, 151 children were evaluated 2, 4, 9, 12 and 18 months after inclusion. At admission, ∼15% of children ≤1 month had a regulation impairment according to the NBAS, and 33.8% presented a distress state (ADBB score >5). More than 85% (129/151) recovered normal psychomotor development. The results of the program reinforce the importance of early detection of psychological disorders followed by rapid implementation of psychological case management to improve the development of young children in similar institutions and circumstances

Evaluating HIV treatment as prevention in the European context

Executive summary The goal of this project is to gather evidence regarding the population-level, and to some extent, individual-level effects of the use of antiretroviral treatment (ART) to prevent HIV infection, and to relate this to current HIV treatment guidelines. To inform the project, formal literature reviews were performed for the three main areas of interest: the effect of antiretroviral therapy in adults on preventing sexual transmission of HIV, prevention of mother-to-child transmission (pMTCT) and post exposure prophylaxis (PEP). The strongest evidence with regard to the effect of treatment of HIV positive individuals to prevent onwards sexual transmission comes from the recent randomised controlled trial (RCT), HPTN052. This study demonstrated that early versus delayed ART led to a 96% relative reduction in onwards linked transmission. Several observational studies of HIV sero-discordant heterosexual couples have also reported that transmission is rare in patients on ART, particularly in those with low HIV-RNA concentrations. However, the findings of HPTN052 and these observational studies are mainly applicable to vaginal heterosexual sex. No direct empirical evidence regarding the relationship between ART use and the risk of HIV transmission through anal intercourse is currently available. Whilst the major HIV treatment guidelines do not explicitly recommend prescribing antiretroviral treatment to prevent onwards transmission, they do not rule out individuals starting ART at a high CD4 count on a case-by-case basis. However, one must also consider the impact of earlier treatment on the HIV positive individual with regard to side effects, and development of drug resistance. Early studies showed that pMTCT regimens containing a single antiretroviral agent (short course zidovudine or single dose nevirapine) or two antiretroviral agents (zidovudine and lamivudine with or without single dose nevirapine) led to clinically important reductions in MTCT rates. However, the most substantial reductions in MTCT rates occurred when combination antiretroviral regimens (more than three antiretroviral drugs) were introduced. These regimens involve the receipt of ART before the third trimester of pregnancy, intrapartum treatment, maternal post-partum treatment and some form of neonatal treatment. There is some evidence from RCTs and extensive evidence from observational studies of the efficacy of these combination regimens, with very low rates of transmission of around 0% to 6%, in settings with no or very little breastfeeding, and 1%-9% when breastfeeding occurs. Furthermore, in settings where avoidance of breastfeeding is not possible, there are a number of studies demonstrating that receipt of maternal and/or neonatal ART during the six months after birth can reduce the risk of perinatal transmissions. All treatment guidelines recommend that HIV-positive pregnant women should receive ART to prevent MTCT, although the exact timing of when ART should begin is not always explicit. Furthermore, where mentioned, use of neonatal ART is also recommended, regardless of whether infants are breastfed. Much of the data supporting the use of PEP are based on animal models, which suggest that PEP is most efficacious if commenced as soon as possible after exposure. When considering occupational exposure to HIV, human studies are limited, as no RCTs exist for ethical reasons. Evidence for efficacy is based on one case control study which demonstrated an 81% reduction in transmission of HIV through the use of zidovudine. Other studies have demonstrated that PEP following occupational exposure is not always effective and there are cases of PEP failure. Similarly, there are also no RCTs assessing the efficacy of PEP for prevention of HIV transmission after sexual exposure, and limited evidence from observational data. Most treatment guidelines agree that PEP is not always effective and PEP policies need to emphasise the importance of risk prevention in the first place in all settings where there is a risk of HIV transmission. Side effects are not uncommon when using PEP, so it is important to consider carefully whether an individual should receive PEP and some studies have suggested that increase in availability of PEP may lead to an increase in risky sex behaviour. Antiretroviral treatment has well documented benefits in reducing transmission of HIV and, in particular, has had a major population level impact on HIV acquisition in children from HIV positive mothers. Further research is needed to help us understand how we can best use ART to prevent HIV infections through other transmission routes, and to develop evidence-based policy recommendations, particularly in the European context

Stress, burnout, depression and work-satisfaction amongst UK anaesthetic trainees; a quantitative analysis of the Satisfaction and Wellbeing in Anaesthetic Training study

There is growing evidence that anaesthetic trainees experience, and may be particularly susceptible to, high levels of work stress, burnout and depression. This is a concern for the safety and wellbeing of these doctors and the patients they treat. To date, there has been no in-depth evaluation of these issues amongst UK anaesthetic trainees examining which groups may be most affected and the professional and personal factors which are associated. We conducted an anonymous electronic survey to determine the prevalence of perceived stress, risk of burnout and depression, and work-satisfaction among anaesthetic trainees within South West England and Wales and explored in detail the influence of key demographic, lifestyle and anaesthetic training variables. We identified a denominator of 619 eligible participants and received 397 responses; a response rate of 64%. We observed a high prevalence of perceived stress (37% [95% CI 32 – 42]), burnout risk (25% [21-29]) and depression risk (18% [15-23]) and found that these issues frequently co-exist. Having no children, >3 days of sickness absence in the previous year, 7.5hrs/week of additional non-clinical work were independently predictive of negative psychological outcomes. Although female gender was associated with higher stress, burnout risk was more likely in male respondents. This information could help in the identification of at-risk groups, as well as informing ways to support these groups and influence resource and intervention design. Targeted interventions, such as modification of exercise behaviour and methods of reducing stressors relating to non-clinical workloads, warrant further research

Entanglement in spin-one Heisenberg chains

By using the concept of negativity, we study entanglement in spin-one Heisenberg chains. Both the bilinear chain and the bilinear-biquadratic chain are considered. Due to the SU(2) symmetry, the negativity can be determined by two correlators, which greatly facilitate the study of entanglement properties. Analytical results of negativity are obtained in the bilinear model up to four spins and the two-spin bilinear-biquadratic model, and numerical results of negativity are presented. We determine the threshold temperature before which the thermal state is doomed to be entangled.Comment: 7 pages and 4 figure