The Moduli Space and Phase Structure of Heterotic Strings in Two Dimensions

We explore the moduli space of heterotic strings in two dimensions. In doing so, we introduce new lines of compactified theories with Spin(24) gauge symmetry and discuss compactifications with Wilson lines. The phase structure of d=2 heterotic string theory is examined by classifying the hypersurfaces in moduli space which support massless quanta or discrete states. Finally, we compute the torus amplitude over much of the moduli space.Comment: 23 pages, 1 figure, harvmac.tex; v2: minor changes to introduction, version to be published in Phys. Rev.

Talking about Bordering

In the summer of 2019 as the UK was in the midst of heated Brexit debates and Theresa May’s minority government clung on to power, Professor Louise Ryan interviewed Professor Nira Yuval-Davis about her recent book Bordering (Yuval-Davis, Wemyss and Cassidy 2019). Although things have changed in some significant ways since that interview, for example Boris Johnson has now replaced Theresa May as Prime Minister, and won a landslide election victory in December, 2019, and the controversial Brexit Bill was passed by the British Parliament, many of the issues about borders and bordering remain extremely relevant today. The current pandemic has not only revealed Britain’s dependence on migrant workers, especially in health and social care, but also exposed health inequalities among migrants and ethnic minorities. As the post-Brexit immigration landscape begins to emerge, the analysis of Nira Yuval Davis remains as pertinent as ever

ALESEP: A computer program for the analysis of airfoil leading edge separation bubbles

The ALESEP program for the analysis of the inviscid/viscous interaction which occurs due to the presence of a closed laminar transitional separation bubble on an airflow is presented. The ALESEP code provides a iterative solution of the boundary layer equations expressed in an inverse formulation coupled to a Cauchy integral representation of the inviscid flow. This interaction analysis is treated as a local perturbation to a known solution obtained from a global airfoil analysis. Part of the required input to the ALESEP code are the reference displacement thickness and tangential velocity distributions. Special windward differencing may be used in the reversed flow regions of the separation bubble to accurately account for the flow direction in the discretization of the streamwise convection of momentum. The ALESEP code contains a forced transition model based on a streamwise intermittency function and a natural transition model based on a solution of the integral form of the turbulent kinetic energy equation. Instructions for the input/output, and program usage are presented

The effect of consumption volume on profile and liking of oral nutritional supplements of varied sweetness: sequential profiling and boredom tests

Oral nutrition supplements (ONS) are routinely prescribed to those with, or at risk of, malnutrition. Previous research identified poor compliance due to taste and sweetness. This paper investigates taste and hedonic liking of ONS, of varying sweetness and metallic levels, over consumption volume; an important consideration as patients are prescribed large volumes of ONS daily. A sequential descriptive profile was developed to determine the perception of sensory attributes over repeat consumption of ONS. Changes in liking of ONS following repeat consumption were characterised by a boredom test. Certain flavour (metallic taste, soya milk flavour) and mouthfeel (mouthdrying, mouthcoating) attributes built up over increased consumption volume (p 0.002). Hedonic liking data from two cohorts, healthy older volunteers (n = 32, median age 73) and patients (n = 28, median age 85), suggested such build-up was disliked. Efforts made to improve the palatability of ONS must take account of the build up of taste and mouthfeel characteristics over increased consumption volume

FearNot! An Anti-Bullying Intervention: Evaluation of an Interactive Virtual Learning Environment

Original paper can be found at: http://www.aisb.org.uk/publications/proceedings.shtm

Accounting for the Decline in AFDC Caseloads: Welfare Reform or Economic Growth?

Nationwide, AFDC caseloads have decreased by about 18 percent since March 1994, while some states, such as Wisconsin, Indiana, and Oregon, have seen declines of 40 percent or more. Two factors are frequently suggested as possible causes: state-level experiments with welfare reform and strong economic growth. In this paper, we use state-level monthly panel data from 1987 to 1996 to assess the importance of each of these factors by estimating a model of AFDC caseloads as a dynamic function of time-dependent state welfare reform variables (welfare waivers) and economic variables such as per capita employment. Our results from the dynamic model suggest that the decline in per capita AFDC caseloads is attributable largely to the economic growth of states and not to waivers from federal welfare policies. In the 26 states experiencing at least a 20 percent decline in per capita AFDC caseloads between 1993 and 1996, we attribute 78 percent of the decline to business-cycle factors and 6 percent to welfare waivers.

Reducing Global Warming and Adapting to Climate Change: The Potential of Organic Agriculture

Climate change mitigation is urgent and adaptation to climate change is crucial, particularly in agriculture, where food security is at stake. Agriculture, currently responsible for 20-30% of global greenhouse gas emissions counting direct and indirect agricultural emissions), can however contribute to both climate change mitigation and adaptation. The main mitigation potential lies in the capacity of agricultural soils to sequester CO2 through building organic matter. This potential can be realized by employing sustainable agricultural practices, such as those commonly found within organic farming systems. Examples of these practices are the use of organic fertilizers and crop rotations including legumes leys and cover crops. Mitigation is also achieved in organic agriculture through the avoidance of open biomass burning and the avoidance of synthetic fertilizers and the related production emissions from fossil fuels. Common organic practices also contribute to adaptation. Building soil organic matter increases water retention capacity, and creates more stabile, fertile soils, thus reducing vulnerability to drought, extreme precipitation events, floods and water logging. Adaptation is further supported by increased agro-ecosystem diversity of organic farms, due to reduced nitrogen inputs and the absence of chemical pesticides. The high diversity together with the lower input costs of organic agriculture is key in reducing production risks associated with extreme weather events. All these advantageous practices are not exclusive to organic agriculture. However, they are core parts of the organic production system, in contrast to most non-organic agriculture, where they play a minor role only. Mitigation in agriculture cannot be restricted to the agricultural sector alone, though. Consumer behaviour strongly influences agricultural production systems, and thus their mitigation potential. Significant factors are meat consumption and food wastage. Any discussion on mitigation climate change in agriculture needs to address the entire food chain and needs to be linked to general sustainable development strategies. The main challenges to climate change mitigation and adaptation in organic agriculture and agriculture in general concern a)the understanding of some of the basic processes, such as the interaction of N2O emissions and soil carbon sequestration, contributions of roots to soil carbon sequestration and the life-cycle emissions of organic fertilizers such as compost; b) approaches for emissions accounting that adequately represent agricultural production systems with multiple and diverse outputs and that also encompass ecosystem services; c) the identification and implementation of most adequate policy frameworks for supporting mitigation and adaptation in agriculture, i.e: not putting systemic approaches at a disadvantage due to difficulties in the quantification of emissions, and in their allocation to single products; d) how to assure that the current focus on mitigation does not lead to neglect of the other sustainability aspects of agriculture, such as pesticide loads, eutrophication, acidification or soil erosion and e) the question how to address consumer behaviour and how to utilize the mitigation potential of changes in consumption patterns

Stability of Bose-Einstein condensates in a Kronig-Penney potential

We study the stability of Bose-Einstein condensates with superfluid currents in a one-dimensional periodic potential. By using the Kronig-Penney model, the condensate and Bogoliubov bands are analytically calculated and the stability of condensates in a periodic potential is discussed. The Landau and dynamical instabilities occur in a Kronig-Penney potential when the quasimomentum of the condensate exceeds certain critical values as in a sinusoidal potential. It is found that the onsets of the Landau and dynamical instabilities coincide with the point where the perfect transmission of low energy excitations through each potential barrier is forbidden. The Landau instability is caused by the excitations with small $q$ and the dynamical instability is caused by the excitations with $q=\pi/a$ at their onsets, where $q$ is the quasimomentum of excitation and $a$ is the lattice constant. A swallow-tail energy loop appears at the edge of the first condensate band when the mean-field energy is sufficiently larger than the strength of the periodic potential. We find that the upper portion of the swallow-tail is always dynamically unstable, but the second Bogoliubov band has a phonon spectrum reflecting the positive effective mass.Comment: 32 pages, 21 figure

Non-contracting groups generated by (3,2)-automata

© Journal Algebra and Discrete Mathematics. We add to the classification of groups generated by 3-state automata over a 2-letter alphabet given by Bondarenko et al., by showing that a number of the groups in the classification are non-contracting. We show that the criterion we use to prove a self-similar action is non-contracting also implies that the associated self-similarity graph introduced by Nekrashevych is non-hyperbolic

Review article: the human intestinal virome in health and disease

Background: The human virome consists of animal-cell viruses causing transient infections, bacteriophage (phage) predators of bacteria and archaea, endogenous retroviruses and viruses causing persistent and latent infections. High-throughput, inexpensive, sensitive sequencing methods and metagenomics now make it possible to study the contribution dsDNA, ssDNA and RNA virus-like particles make to the human virome, and in particular the intestinal virome. Aim: To review and evaluate the pioneering studies that have attempted to characterise the human virome and generated an increased interest in understanding how the intestinal virome might contribute to maintaining health, and the pathogenesis of chronic diseases. Methods: Relevant virome-related articles were selected for review following extensive language- and date-unrestricted, electronic searches of the literature. Results: The human intestinal virome is personalised and stable, and dominated by phages. It develops soon after birth in parallel with prokaryotic communities of the microbiota, becoming established during the first few years of life. By infecting specific populations of bacteria, phages can alter microbiota structure by killing host cells or altering their phenotype, enabling phages to contribute to maintaining intestinal homeostasis or microbial imbalance (dysbiosis), and the development of chronic infectious and autoimmune diseases including HIV infection and Crohn's disease, respectively. Conclusions: Our understanding of the intestinal virome is fragmented and requires standardised methods for virus isolation and sequencing to provide a more complete picture of the virome, which is key to explaining the basis of virome-disease associations, and how enteric viruses can contribute to disease aetiologies and be rationalised as targets for interventions