418 research outputs found
Weinhold'length in an isochoric thermodynamic system at constant heat capacity
The purpose of this paper is to study thermodynamic length of an isochoric
two dimensional thermodynamic system with constant heat capacity. We find that
length is related to the heat flow into the substance. We give examples of
Ideal gas and Van der Waals gas
Evolving attackers against wireless sensor networks using genetic programming
Recent hardware developments have made it possible for the Internet of Things (IoT) to be built. A wide variety of industry sectors, including manufacturing, utilities, agriculture, transportation, and healthcare are actively seeking to incorporate IoT technologies in their operations. The increased connectivity and data sharing that give IoT systems their advantages also increase their vulnerability to attack. In this study, the authors explore the automated generation of attacks using genetic programming (GP), so that defences can be tested objectively in advance of deployment. In the authors' system, the GP-generated attackers targeted publish-subscribe communications within a wireless sensor networks that was protected by an artificial immune intrusion detection system (IDS) taken from the literature. The GP attackers successfully suppressed more legitimate messages than the hand-coded attack used originally to test the IDS, whilst reducing the likelihood of detection. Based on the results, it was possible to reconfigure the IDS to improve its performance. Whilst the experiments were focussed on establishing a proof-of-principle rather than a turnkey solution, they indicate that GP-generated attackers have the potential to improve the protection of systems with large attack surfaces, in a way that is complementary to traditional testing and certification
A meta-analysis of how parasites affect host consumption rates
Parasites are known to mediate trophic interactions and can, for example, modify how consumers acquire resources. These modifications of host feeding behaviour can be imposed through three interconnected mechanisms affecting: 1) host food acquisition, 2) host food digestion or 3) host energy budgets. As a result, infected hosts may consume more, less or the same amount of food compared to their uninfected conspecifics. It is commonly assumed that infected hosts have lower consumption rates than uninfected hosts, but a comprehensive quantitative synthesis investigating the effects of parasites on host consumption rate has been lacking thus far. To fill this knowledge gap, we systematically searched for experimental studies that evaluated changes in consumption rate of infected vs uninfected hosts. In total, we extracted 158 effect sizes from 68 studies. We then performed meta-analyses of mean differences in host consumption rates and their variation. The analyses were carried out for all taxonomic groups as well as separately for vertebrate and invertebrate hosts. The main-effects meta-analyses confirmed a generally negative effect of parasites on host consumption rates; infected hosts consumed on average 25% less food than their uninfected conspecifics. In addition, there was a significant increase in the variability in host consumption rate, on average by 25%, indicating that parasites can have variable effects on the foraging behaviour of their hosts. The meta-regression models revealed that several moderator variables related to host and parasite characteristics influence host consumption rate. Experimental infection had a stronger influence on variance effects than natural infection. Parasitic infections reduced consumption rate of vertebrate hosts by 28% and thus more strongly than those of invertebrates, which were reduced by 22%. We conclude with recommendations to facilitate future ecological research syntheses on host-parasite interactions and beyond
The Entropy of Lagrange-Finsler Spaces and Ricci Flows
We formulate a statistical analogy of regular Lagrange mechanics and Finsler
geometry derived from Grisha Perelman's functionals generalized for
nonholonomic Ricci flows. There are elaborated explicit constructions when
nonholonomically constrained flows of Riemann metrics result in Finsler like
configurations, and inversely, and geometric mechanics is modelled on Riemann
spaces with preferred nonholonomic frame structure.Comment: latex2e, 20 pages, v3, the variant accepted to Rep. Math. Phy
Apparent interspecific transmission of Aphanomyces astaci from invasive signal to virile crayfish in a sympatric wild population
The crayfish plague pathogen (Aphanomyces astaci) causes mass mortalities of European crayfish when transmitted from its original North American crayfish hosts. Little is known, however, about interspecific transmission of the pathogen between different American crayfish species, although evidence from trade of ornamental crayfish suggests this may happen in captivity. We screened signal and virile crayfish for A. astaci at allopatric and sympatric sites in a UK river. Whilst the pathogen was detected in signal crayfish from both sites, infected virile crayfish were only found in sympatry. Genotyping of A. astaci from virile crayfish suggested the presence of a strain related to one infecting British signal crayfish. We conclude that virile crayfish likely contracted A. astaci interspecifically from infected signal crayfish. Interspecific transmission of A. astaci strains differing in virulence between American carrier species may influence the spread of this pathogen in open waters with potential exacerbated effects on native European crayfish
Geometrothermodynamics of black holes
The thermodynamics of black holes is reformulated within the context of the
recently developed formalism of geometrothermodynamics. This reformulation is
shown to be invariant with respect to Legendre transformations, and to allow
several equivalent representations. Legendre invariance allows us to explain a
series of contradictory results known in the literature from the use of
Weinhold's and Ruppeiner's thermodynamic metrics for black holes. For the
Reissner-Nordstr\"om black hole the geometry of the space of equilibrium states
is curved, showing a non trivial thermodynamic interaction, and the curvature
contains information about critical points and phase transitions. On the
contrary, for the Kerr black hole the geometry is flat and does not explain its
phase transition structure.Comment: Revised version, to be published in Gen.Rel.Grav.(Mashhoon's
Festschrift
New type of phase transition in Reissner Nordstr\"om - AdS black hole and its thermodynamic geometry
The phase transition of a RN-AdS black hole is studied in details using
Ehrenfest's equations. There is no discontinuity in entropy which signals a
lack of any first order phase transition. We then show that although
Ehrenfest's first equation is satisfied, the second is not, so that a true
second order phase transition is also ruled out. However this deviation from
the second Ehrenfest's equation, for a certain range of the black hole charge,
indicates the existence of a new glassy type transition. We finally study the
thermodynamic behaviour using state space geometry and find that the scalar
curvature diverges exactly at those points where the heat capacity diverges.Comment: Major revisions in Sec. 3. New results and interpretations. 2 new
references. To appear in Phys. Lett.
A Commentary on Ruppeiner Metrics for Black Holes
There has been some recent controversy regarding the Ruppeiner metrics that
are induced by Reissner-Nordstrom (and Reissner-Nordstrom-like) black holes.
Most infamously, why does this family of metrics turn out to be flat, how is
this outcome to be physically understood, and can/should the formalism be
suitably modified to induce curvature? In the current paper, we provide a novel
interpretation of this debate. For the sake of maximal analytic clarity and
tractability, some supporting calculations are carried out for the relatively
simple model of a rotating BTZ black hole.Comment: 15 pages; v2, typos corrected and a few references adde
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