Free Energies of Dilute Bose gases: upper bound

We derive a upper bound on the free energy of a Bose gas system at density $\rho$ and temperature $T$. In combination with the lower bound derived previously by Seiringer \cite{RS1}, our result proves that in the low density limit, i.e., when $a^3\rho\ll 1$, where $a$ denotes the scattering length of the pair-interaction potential, the leading term of $\Delta f$ the free energy difference per volume between interacting and ideal Bose gases is equal to 4\pi a (2\rho^2-[\rho-\rhoc]^2_+). Here, \rhoc(T) denotes the critical density for Bose-Einstein condensation (for the ideal gas), and $[\cdot ]_+$ $=$ $\max\{\cdot, 0\}$ denotes the positive part.Comment: 56 pages, no figure

Modelling the emergence of cities and urban patterning using coupled integro-differential equations

Human residential population distributions show patterns of higher density clustering around local services such as shops and places of employment, displaying characteristic length scales; Fourier transforms and spatial autocorrelation show the length scale between UK cities is around 45 km. We use integro-differential equations to model the spatio-temporal dynamics of population and service density under the assumption that they benefit from spatial proximity, captured via spatial weight kernels. The system tends towards a well-mixed homogeneous state or a spatial pattern. Linear stability analysis around the homogeneous steady state predicts a modelled length-scale consistent with that observed in the data. Moreover, we show that spatial instability occurs only for perturbations with a sufficiently long wavelength and only where there is a sufficiently strong dependence of service potential on population density. Within urban centres, competition for space may cause services and population to be out of phase with one another, occupying separate parcels of land. By introducing competition, along with a preference for population to be located near, but not too near, to high service density areas, secondary out-of-phase patterns occur within the model, at a higher density and with a shorter length scale than in phase patterning. Thus, we show that a small set of core behavioural ingredients can generate aggregations of populations and services, and pattern formation within cities, with length scales consistent with real-world data. The analysis and results are valid across a wide range of parameter values and functional forms in the model

Dietary trehalose enhances virulence of epidemic Clostridium difficile

Molecular basis of bacterial pathogenesis, virulence factors and antibiotic resistanc

Finite Temperature Properties of Quantum Antiferromagnets in a Uniform Magnetic Field in One and Two Dimensions

Consider a $d$-dimensional antiferromagnet with a quantum disordered ground state and a gap to bosonic excitations with non-zero spin. In a finite external magnetic field, this antiferromagnet will undergo a phase transition to a ground state with non-zero magnetization, describable as the condensation of a dilute gas of bosons. The finite temperature properties of the Bose gas in the vicinity of this transition are argued to obey a hypothesis of ZERO SCALE-FACTOR UNIVERSALITY for $d < 2$, with logarithmic violations in $d=2$. Scaling properties of various experimental observables are computed in an expansion in $\epsilon=2-d$, and exactly in $d=1$.Comment: 27 pages, REVTEX 3.0, 8 Postscript figures appended, YCTP-xyz

Atmospheric Heating and Wind Acceleration: Results for Cool Evolved Stars based on Proposed Processes

A chromosphere is a universal attribute of stars of spectral type later than ~F5. Evolved (K and M) giants and supergiants (including the zeta Aurigae binaries) show extended and highly turbulent chromospheres, which develop into slow massive winds. The associated continuous mass loss has a significant impact on stellar evolution, and thence on the chemical evolution of galaxies. Yet despite the fundamental importance of those winds in astrophysics, the question of their origin(s) remains unsolved. What sources heat a chromosphere? What is the role of the chromosphere in the formation of stellar winds? This chapter provides a review of the observational requirements and theoretical approaches for modeling chromospheric heating and the acceleration of winds in single cool, evolved stars and in eclipsing binary stars, including physical models that have recently been proposed. It describes the successes that have been achieved so far by invoking acoustic and MHD waves to provide a physical description of plasma heating and wind acceleration, and discusses the challenges that still remain.Comment: 46 pages, 9 figures, 1 table; modified and unedited manuscript; accepted version to appear in: Giants of Eclipse, eds. E. Griffin and T. Ake (Berlin: Springer

Carbohydrate metabolism genes and pathways in insects: insights from the honey bee genome

Carbohydrate-metabolizing enzymes may have particularly interesting roles in the honey bee, Apis mellifera, because this social insect has an extremely carbohydrate-rich diet, and nutrition plays important roles in caste determination and socially mediated behavioural plasticity. We annotated a total of 174 genes encoding carbohydrate-metabolizing enzymes and 28 genes encoding lipid-metabolizing enzymes, based on orthology to their counterparts in the fly, Drosophila melanogaster, and the mosquito, Anopheles gambiae. We found that the number of genes for carbohydrate metabolism appears to be more evolutionarily labile than for lipid metabolism. In particular, we identified striking changes in gene number or genomic organization for genes encoding glycolytic enzymes, cellulase, glucose oxidase and glucose dehydrogenases, glucose-methanol-choline (GMC) oxidoreductases, fucosyltransferases, and lysozymes

Hydration status affects thirst and salt preference but not energy intake or postprandial ghrelin in healthy adults : a randomised crossover trial

Background Few studies have investigated the effect of hydration status on appetite for food in healthy adults. Prior work suggests hydration status does not alter appetite or energy intake, with mixed findings regarding appetite hormone secretion. However, an extensive investigation into both the psychological and physiological appetitive responses to hydration status has never been conducted. Objective To investigate the effect of hydration status on multiple facets of appetite. Design After 3 days pre-trial standardization, a range of appetite tasks were conducted when hypohydrated (HYPO) and euhydrated (EUHY) in 16 healthy participants (8 men). Hydration status was manipulated via dehydration in a heat tent for 60 min and subsequent fluid restriction (HYPO) or replacement (EUHY). The next day, a food reward computer task was completed followed by an ad libitum pasta meal. Pre- and post-prandial visual analogue scales assessing hunger, fullness, and flavour desires (sweet, salty, savoury and fatty) were additionally completed. Blood samples were taken the previous day before the hydration interventions in a euhydrated state, and in the fasted and post-prandial state during HYPO and EUHY. Results HYPO induced -1.9 ± 1.2% body mass change, compared to -0.2 ± 0.6% , with accompanying changes in markers of hypohydration which were not seen during EUHY. A higher desire for foods was associated with a higher water content but the association was weaker in EUHY compared to HYPO, (β= -0.33 mm/g of food water content, p < 0.001) in the food reward task. Visual analogue scales showed similar hunger and fullness between interventions, but during HYPO there was consistently higher thirst (average range in difference 27–32 mm across all time points) and lower fasted desire for salt (−23, 95% CI −10, −35 mm). Ad libitum energy intake (HYPO 1953 ± 742 kJ, EUHY 2027 ± 926 kJ; p = 0.542) and post-prandial ghrelin concentrations (HYPO 180 ± 65 pg mL−1, EUHY 188 ± 71 pg mL−1; p = 0.736) were similar by hydration status. Conclusions An acute manipulation to hydration status altered desire for salt and foods of differing water contents, but did not influence energy intake at an ad libitum pasta meal. Further research should investigate whether these appetites would alter food choice