Cosmological constant in SUGRA models with Planck scale SUSY breaking and degenerate vacua

The empirical mass of the Higgs boson suggests small to vanishing values of the quartic Higgs self-coupling and the corresponding beta function at the Planck scale, leading to degenerate vacua. This leads us to suggest that the measured value of the cosmological constant can originate from supergravity (SUGRA) models with degenerate vacua. This scenario is realised if there are at least three exactly degenerate vacua. In the first vacuum, associated with the physical one, local supersymmetry (SUSY) is broken near the Planck scale while the breakdown of the SU(2)W×U(1)Y symmetry takes place at the electroweak (EW) scale. In the second vacuum local SUSY breaking is induced by gaugino condensation at a scale which is just slightly lower than ΛQCD in the physical vacuum. Finally, in the third vacuum local SUSY and EW symmetry are broken near the Planck scale

Ecological and evolutionary processes at expanding range margins

Many animals are regarded as relatively sedentary and specialized in marginal parts of their geographical distributions. They are expected to be slow at colonizing new habitats. Despite this, the cool margins of many species' distributions have expanded rapidly in association with recent climate warming. We examined four insect species that have expanded their geographical ranges in Britain over the past 20 years. Here we report that two butterfly species have increased the variety of habitat types that they can colonize, and that two bush cricket species show increased fractions of longer-winged (dispersive) individuals in recently founded populations. Both ecological and evolutionary processes are probably responsible for these changes. Increased habitat breadth and dispersal tendencies have resulted in about 3- to 15-fold increases in expansion rates, allowing these insects to cross habitat disjunctions that would have represented major or complete barriers to dispersal before the expansions started. The emergence of dispersive phenotypes will increase the speed at which species invade new environments, and probably underlies the responses of many species to both past and future climate change

The effect of metapopulation processes on the spatial scale of adaptation across an environmental gradient

We show that the butterfly Aricia agestis (Lycaenidae) is adapted to its thermal environment in via integer changes in the numbers of generations per year (voltinism): it has two generations per year in warm habitats and one generation per year in cool habitats in north Wales (UK). Voltinism is an “adaptive peak” since individuals having an intermediate number of generations per year would fail to survive the winter, and indeed no populations showed both voltinism types in nature. In spite of this general pattern, 11% of populations apparently possess the “wrong” voltinism for their local environment, and population densities were lower in thermally intermediate habitat patches. Population dynamic data and patterns of genetic differentiation suggest that adaptation occurs at the metapopulation level, with local populations possessing the voltinism type appropriate for the commonest habitat type within each population network. When populations and groups of populations go extinct, they tend to be replaced by colonists from the commonest thermal environment nearby, even if this is the locally incorrect adaptation. Our results illustrate how stochastic population turnover can impose a limit on local adaptation over distances many times larger than predicted on the basis of normal dispersal movements

Computational studies on gas phase polyborate anions

The borate anions [B(OH)4]�, [B2O(OH)5]�, [B3O3(OH)4]�, [B3O3(OH)5]2�, [B3O3(OH)6]3�, [B4O5(OH)4]2�, [B5O6(OH)4]�, and [B7O9(OH)5]2� (2 isomers) and the neutral orthoboric and metaboric acids, B(OH)3 and B3O3(OH)3, have been structurally optimised in the gas phase at the B3LYP/6-311++G(d,p) level. Energetic data, combined with analogous data for �building blocks� H2O and [OH]�, has enabled their relative gas phase stabilities (all exothermic) to be determined using an isodesmic approach as: [B5O6(OH)4]� > [B3O3(OH)4]� > [B(OH)4]� > [B7O9(OH)5]2� > [B4O5(OH)4]2� > [B3O3(OH)5]2�. The two isomers of [B7O9(OH)5]2� have similar total energies although the �ribbon� isomer is calculated to be more stable by only 10.0 kJ mol�1. QTAIM analyses have been undertaken on all computed structures, and QTAIM charges for H, O and B atoms have been calculated. It is concluded that H-bond interactions dominate the solid-state energetics of non-metal cation polyborate salts

Bandit models and Blotto games

In this thesis we present a new take on two classic problems of game theory: the "multiarmed bandit" problem of dynamic learning, and the "Colonel Blotto" game, a multidi- mensional contest. In Chapters 2-4 we treat the questions of experimentation with congestion: how do players search and learn about options when they are competing for access with other players? We consider a bandit model in which two players choose between learning about the quality of a risky option (modelled as a Poisson process with unknown arrival rate), and competing for the use of a single shared safe option that can only be used by one agent at the time. We present the equilibria of the game when switching to the safe option is irrevocable, and when it is not. We show that the equilibrium is always inefficient: it involves too little experimentation when compared to the planner solution. The striking equilibrium dynamics of the game with revocable exit are driven by a strategic option-value arising purely from competition between the players. This constitutes a new result in the bandit literature. Finally we present extensions to the model. In particular we assume that players do not observe the result of their opponent's experimentation. In Chapter 5 we turn to the n-dimensional Blotto game and allow battlefi�elds to have di�fferent values. We describe a geometrical method for constructing equilibrium distribution in the Colonel Blotto game with asymmetric battlfi�eld values. It generalises the 3-dimensional construction method �first described by Gross and Wagner (1950). The proposed method does particularly well in instances of the Colonel Blotto game in which the battlefi�eld weights satisfy some clearly defi�ned regularity conditions. The chapter also explores the parallel between these conditions and the integer partitioning problem in combinatorial optimisation

Weed survey and management practices used in alfalfa (Medicago sativa) seed fields in 1997

Non-Peer ReviewedA weed survey in alfalfa seed fields, located primarily in northeast Saskatchewan, was conducted in 1997. Following the weed survey, a farm management questionnaire was used to determine the influence of farm management practices on the surveyed weed community. Results from the weed survey and farm management questionnaire were compared to a similar survey and questionnaire conducted in 1989-90. Wild oats and green foxtail were the most abundant annual grass weeds and their relative abundance did not change significantly. Narrow-leaved hawk’s beard generally decreased in relative abundance while perennial weed species usually increased. Herbicides were the most common weed management practice used in Saskatchewan alfalfa seed fields and their use increased compared to the previous questionnaire. Group 1 herbicide use exceeded the recommended frequency to delay the onset of resistance in wild oats and green foxtail in over half of the fields surveyed. The increase in herbicide use may account for the reduction in relative abundance of some annual broad-leaved weed species between 1989-90 and 1997. The decrease in annual weed competition may have allowed some perennial weeds, which are harder to control with herbicides, to increase in relative abundance

Lookup tables to compute high energy cosmic ray induced atmospheric ionization and changes in atmospheric chemistry

A variety of events such as gamma-ray bursts and supernovae may expose the Earth to an increased flux of high-energy cosmic rays, with potentially important effects on the biosphere. Existing atmospheric chemistry software does not have the capability of incorporating the effects of substantial cosmic ray flux above 10 GeV . An atmospheric code, the NASA-Goddard Space Flight Center two-dimensional (latitude, altitude) time-dependent atmospheric model (NGSFC), is used to study atmospheric chemistry changes. Using CORSIKA, we have created tables that can be used to compute high energy cosmic ray (10 GeV - 1 PeV) induced atmospheric ionization and also, with the use of the NGSFC code, can be used to simulate the resulting atmospheric chemistry changes. We discuss the tables, their uses, weaknesses, and strengths.Comment: In press: Journal of Cosmology and Astroparticle Physics. 6 figures, 3 tables, two associated data files. Major revisions, including results of a greatly expanded computation, clarification and updated references. In the future we will expand the table to at least EeV levels

Deconfinement at finite chemical potential

In a confining, renormalisable, Dyson-Schwinger equation model of two-flavour QCD we explore the chemical-potential dependence of the dressed-quark propagator, which provides a means of determining the behaviour of the chiral and deconfinement order parameters, and low-energy pion observables. We find coincident, first order deconfinement and chiral symmetry restoration transitions at \mu_c = 375 MeV. f_\pi is insensitive to \mu until \mu \approx \mu_0 = 0.7 mu_c when it begins to increase rapidly. m_\pi is weakly dependent on \mu, decreasing slowly with \mu and reaching a minimum 6% less than its \mu=0 value at \mu=\mu_0. In a two-flavour free-quark gas at \mu=\mu_c the baryon number density would be approximately 3 \rho_0, where \rho_0=0.16 fm^{-3}; while in such a gas at \mu_0 the density is \rho_0.Comment: 11 pages, 3 figures, epsfig.sty, elsart.st

High-resolution wetness index mapping: A useful tool for regional scale wetland management

Wetland ecosystems are key habitats for carbon sequestration, biodiversity and ecosystem services, yet in many they localities have been subject to modification or damage. In recent years, there has been increasing focus on effective management and, where possible, restoration of wetlands. Whilst this is highly laudable, practical implementation is limited by the high costs and unpredictable rates of success. Accordingly, there is a need for spatial information to guide restoration, ideally at the regional scale that land managers operate. In this study, we use high-resolution Light Detection and Ranging (LiDAR)-derived elevation, in conjunction with regional soil and land cover maps, to model the wetness potential of an area of conservation importance in north-west England. We use the Compound Topographic Index (CTI) as a measure for the site-specific wetness and potential to be receptive to wetland restoration. The resulting model is in agreement with the regional-scale distribution of wetlands and is clearly influenced by the topographic and soil parameters. An assessment of three representative case studies highlights the small scale features that determine the potential wetness of an area. For each site, the model results conform to the expected patterns of wetness, highlighting restoration and management activity. Furthermore, areas showing high potential wetness that may be suitable for wetland habitat creation, are highlighted. The increasing availability of LiDAR data at regional and national scales will allow studies of this nature to be undertaken at previously unobtainable resolutions. Simple models, such as implemented here, benefit from explainability and relatability and have clear potential for use by managers and conservation agencies involved in wetland restoration

RepD-mediated recruitment of PcrA helicase at the Staphylococcus aureus pC221 plasmid replication origin, oriD

Plasmid encoded replication initiation (Rep) proteins recruit host helicases to plasmid replication origins. Previously, we showed that RepD recruits directionally the PcrA helicase to the pC221 oriD, remains associated with it, and increases its processivity during plasmid unwinding. Here we show that RepD forms a complex extending upstream and downstream of the core oriD. Binding of RepD causes remodelling of a region upstream from the core oriD forming a 'landing pad' for the PcrA. PcrA is recruited by this extended RepD-DNA complex via an interaction with RepD at this upstream site. PcrA appears to have weak affinity for this region even in the absence of RepD. Upon binding of ADPNP (non-hydrolysable analogue of ATP), by PcrA, a conformational rearrangement of the RepD-PcrA-ATP initiation complex confines it strictly within the boundaries of the core oriD. We conclude that RepD-mediated recruitment of PcrA at oriD is a three step process. First, an extended RepD-oriD complex includes a region upstream from the core oriD; second, the PcrA is recruited to this upstream region and thirdly upon ATP-binding PcrA relocates within the core oriD