Velocity fluctuations of population fronts propagating into metastable states

The position of propagating population fronts fluctuates because of the discreteness of the individuals and stochastic character of processes of birth, death and migration. Here we consider a Markov model of a population front propagating into a metastable state, and focus on the weak noise limit. For typical, small fluctuations the front motion is diffusive, and we calculate the front diffusion coefficient. We also determine the probability distribution of rare, large fluctuations of the front position and, for a given average front velocity, find the most likely population density profile of the front. Implications of the theory for population extinction risk are briefly considered.Comment: 8 pages, 3 figure

Bose-Einstein condensation in an optical lattice: A perturbation approach

We derive closed analytical expressions for the order parameter $\Phi (x)$ and for the chemical potential $\mu$ of a Bose-Einstein Condensate loaded into a harmonically confined, one dimensional optical lattice, for sufficiently weak, repulsive or attractive interaction, and not too strong laser intensities. Our results are compared with exact numerical calculations in order to map out the range of validity of the perturbative analytical approach. We identify parameter values where the optical lattice compensates the interaction-induced nonlinearity, such that the condensate ground state coincides with a simple, single particle harmonic oscillator wave function

The null energy condition and instability

We extend previous work showing that violation of the null energy condition implies instability in a broad class of models, including gauge theories with scalar and fermionic matter as well as any perfect fluid. Simple examples are given to illustrate these results. The role of causality in our results is discussed. Finally, we extend the fluid results to more general systems in thermal equilibrium. When applied to the dark energy, our results imply that w is unlikely to be less than -1.Comment: 11 pages, 5 figures, Revte

Between-strain differences in hypothermic response in mice after intranasal administration of PtO nanoparticles

Air pollution by particulate matter (PM) has been associated with cardiopulmonary morbidity and mortality in many recent epidemiological studies. It has been shown that transition metal compounds, well- known toxic components of PM, are able to induce hypothermia following whole-body inhalation exposure. Low temperature appears to protect tissue against toxic effects of PM metal compounds in vivo and in vitro. To study the role of soluble and insoluble irritants in the induction of the hypothermic response, we analyz­ed the decrease in mouse body temperature (Δtbody) after intranasal administration of PtO nanoparticles or a K2[PtCl 4] solution. Between-strain differences in Δtbody after intranasal administration of the irritants were evaluated using 6 inbred (BALB/cJ, C57BL/6J, AKR/OlaHsd, DBA/2JRccHsd, C3H/HeNHsd, and SJL/J) and 2 outbred mouse strains (SCID and CD1). BALB/cJ and SCID mice showed the most pronounced effect of intranasal admini­stration of the xenobiotic on tbody. Thus, tbody was signi­ficantly lower after nasal administration the PtO nano­particles than after administration of the K2[PtCl 4] solution. To study the mechanism of this decrease, we compar­ed the respective values for Δtbody following intra­nasal, intravenous and peroral administration of PtO nanoparticles in Balb/c mice. Neither intravenous nor peroral administration had any effect on mouse body temperature. This fact together with data on the dynamics of the decrease in mouse body temperature following intranasal administration of PtO nanoparticles (max Δtbody ~ 80–100 min) allowed us to assume that this process is under nervous regulation. The correlation found between our data and some well-known phenotypic characteristics (phenome.jax.org) of the mouse strains used confirms this hypothesis

Using a multi-lens framework for landscape decisions

1. Landscape decisions are multi-faceted. Framing landscape decision-making as a governance process that requires a collective approach can encourage key stakeholders to come together to co-inform a discussion about their priorities and what constitutes good governance, leading to more holistic landscape decisions. 2. In this paper, we recognise that a suite of complementary and multi-dimensional approaches are in practice used to inform and evaluate land use decisions. We have called these approaches ‘lenses’ because they each provide a different perspective on the same problem. The four lenses are: i) Power and Market Gain, ii) Ecosystem Services, iii), Place-based Identity and iv) Ecocentric. Each brings a different set of evidence and viewpoints (narrative, qualitative and experiential, as well as quantitative metrics such as monetary) to the decision-making process and can potentially reveal problems and solutions that others do not. 3. Considering all lenses together allows dialogue to take place which can reveal the true complexities of landscape decision-making and can facilitate more effective and more holistic decisions. Employing the lenses requires governance structures that give equal weight to all lenses, enable dialogue and coexistence between top down and bottom-up approaches, and permit adaptation to local and granular place-specifics rather than developing “one-size-fits-all” solutions. 4. We propose that formalising the process of balancing all the lenses requires public participation, and that a lens approach should be used to support landscape decisions alongside a checklist that facilitates transparency in the conversation, showing how all evidence has been considered and critically assessed

Normal families of functions and groups of pseudoconformal diffeomorphisms of quaternion and octonion variables

This paper is devoted to the specific class of pseudoconformal mappings of quaternion and octonion variables. Normal families of functions are defined and investigated. Four criteria of a family being normal are proven. Then groups of pseudoconformal diffeomorphisms of quaternion and octonion manifolds are investigated. It is proven, that they are finite dimensional Lie groups for compact manifolds. Their examples are given. Many charactersitic features are found in comparison with commutative geometry over $\bf R$ or $\bf C$.Comment: 55 pages, 53 reference

A link between phenotypic robustness and life expectancy in Drosophila melanogaster

Long-lived systems are expected to be stable, i. e. resistant to either external influences, or internal failures. Robustness of biological systems can be defined as a reciprocal value to their phenotypic plasticity expressed through a coefficient of variation (C.V.) for positively distributed phenotypic traits. Considering lifespan as phenotype, which integrates all functions of an organism, we showed that its phenotypic robustness correlates positively with life expectancy. We assessed lifespan parameters for a selection of inbred Drosophila melanogaster strains from Drosophila Genetic Reference Panel (DGRP) reared at 29 ºС. The robustness of lifespan phenotype (C.V.–1) correlated positively with estimated life expectancy for these strains. The same relation also holds for the lifespan of all DGRP strains reared at 25 ºС. Also, in agreement with previous observations, upon temperature change (decrease or increase) the survival curves scaled in time (stretched or shrunk respectively). In other words, the average lifespan decreased for flies reared at elevated temperature, but so did the standard deviation, and thus the coefficients of variation remained in the same range. From this we conclude that coefficients of variation correlate with life expectancies and account for the robustness of lifespan phenotype irrespective of accelerated aging caused by temperature

Constructing a Stochastic Model of Bumblebee Flights from Experimental Data

PMCID: PMC3592844This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited