2,313 research outputs found

    Density-dependent effects on the weight of female Ascaris lumbricoides infections of humans and its impact on patterns of egg production

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    <p>Abstract</p> <p>Background</p> <p><it>Ascaris lumbricoides </it>exhibits density-dependent egg production, a process which has a marked impact on both the transmission dynamics and the stability of the parasite population. Evidence suggests that the egg production of female <it>Ascaris </it>is also associated with the size of the worm. If worm size is mediated by density-dependent processes then the size of female worms may have a causal impact upon patterns of <it>Ascaris </it>egg production.</p> <p>Results</p> <p>We analyse data collected from a cohort of human hosts, and demonstrate that the per host mean weight (a proxy for size) of female <it>Ascaris </it>is dependent on the number of infecting females (worm burden) following a pattern of initial facilitation followed by limitation. Applying a negative binomial (NB) generalized linear model (GLM) and a zero-inflated negative binomial (ZINB) model we confirm that the per host female mean weight is significantly associated with per host egg production. Despite these associations, the mean weight of female <it>Ascaris </it>has little causal impact on patterns of density-dependent egg output. The ZINB model is able to account for the disproportionately large number of zero egg counts within the data and is shown to be a consistently better fit than the NB model. The probability of observing a zero egg count is demonstrated as being negatively associated with both female worm burden and female mean weight.</p> <p>Conclusion</p> <p>The mean weight of female <it>Ascaris </it>is statistically significantly associated with egg output, and follows a consistent pattern of facilitation preceding limitation with increasing female worm burden. Despite these relationships, incorporation of female <it>Ascaris </it>mean weight into models of egg output has little effect on patterns of density dependence. The ZINB model is a superior fit to the data than the NB model and provides additional information regarding the mechanisms that result in a zero egg count. The ZINB model is shown to be a useful tool for the analysis of individual-based egg output data.</p

    Ionic Liquids Containing Sulfonium Cations as Electrolytes for Electrochemical Double Layer Capacitors

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    In this work, we report on the behavior of ionic liquids (ILs) containing sulfonium cations as electrolytes for electrochemical double layer capacitors (EDLCs). Physical properties such as viscosity and ionic conductivity are reported over a range of temperatures for ILs containing the diethylmethyl sulfonium [S221], triethyl sulfonium [S222], and diethylpropyl sulfonium [S223] cations paired with the bis(trifluoromethanesulfonyl) imide [Tf2N] anion. The size and structure of the cations are shown to influence the physical and electrochemical properties of the ILs, with a significant degree of ionic coordination being evident in [S223][Tf2N]. The electrochemical behavior of these ILs in EDLCs was compared with that of a fairly established IL electrolyte, N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide ([Pyr14][Tf2N]), and it is shown that [S221][Tf2N] can perform better in terms of energy and power at room temperature, despite operating at a much reduced potential

    Reply to "Comment on 'Intrinsic decoherence in quantum mechanics'"

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    Finkelstein’s criticism [Phys. Rev. A (to be published)] of my paper [Phys. Rev. A 44, 5401 (1991)] presupposes time measurements of an accuracy explicitly ruled out in the paper

    Curvature Diffusions in General Relativity

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    We define and study on Lorentz manifolds a family of covariant diffusions in which the quadratic variation is locally determined by the curvature. This allows the interpretation of the diffusion effect on a particle by its interaction with the ambient space-time. We will focus on the case of warped products, especially Robertson-Walker manifolds, and analyse their asymptotic behaviour in the case of Einstein-de Sitter-like manifolds.Comment: 34 page

    Approximate Deadline-Scheduling with Precedence Constraints

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    We consider the classic problem of scheduling a set of n jobs non-preemptively on a single machine. Each job j has non-negative processing time, weight, and deadline, and a feasible schedule needs to be consistent with chain-like precedence constraints. The goal is to compute a feasible schedule that minimizes the sum of penalties of late jobs. Lenstra and Rinnoy Kan [Annals of Disc. Math., 1977] in their seminal work introduced this problem and showed that it is strongly NP-hard, even when all processing times and weights are 1. We study the approximability of the problem and our main result is an O(log k)-approximation algorithm for instances with k distinct job deadlines

    Equivalence of the (generalised) Hadamard and microlocal spectrum condition for (generalised) free fields in curved spacetime

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    We prove that the singularity structure of all n-point distributions of a state of a generalised real free scalar field in curved spacetime can be estimated if the two-point distribution is of Hadamard form. In particular this applies to the real free scalar field and the result has applications in perturbative quantum field theory, showing that the class of all Hadamard states is the state space of interest. In our proof we assume that the field is a generalised free field, i.e. that it satisies scalar (c-number) commutation relations, but it need not satisfy an equation of motion. The same argument also works for anti-commutation relations and it can be generalised to vector-valued fields. To indicate the strengths and limitations of our assumption we also prove the analogues of a theorem by Borchers and Zimmermann on the self-adjointness of field operators and of a very weak form of the Jost-Schroer theorem. The original proofs of these results in the Wightman framework make use of analytic continuation arguments. In our case no analyticity is assumed, but to some extent the scalar commutation relations can take its place.Comment: 18 page

    Samarbeidsavtaler mellom kommuner og helseforetak – etterleves de?: En undersþkelse av erfaringene i et utvalg kommuner og helseforetak

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    Denne undersÞkelsen har hatt som formÄl Ä kartlegge hvordan samarbeidsavtaler mellom kommuner og helseforetak, et av virkemidlene i Samhandlingsreformen, fungerer i et utvalg kommuner og helseforetak. Gjennom en kvalitativ tilnÊrming er det undersÞkt hvorvidt intensjonene og forpliktelsene i de inngÄtte samarbeidsavtalene etterleves, i tillegg er viktige suksesskriterier for at avtalene skal virke etter intensjonen identifisert og konkretisert. LovpÄlagte samarbeidsavtaler mellom kommuner og helseforetak er et av virkemidlene som skal bidra til Ä realisere mÄlsetningene ved Samhandlingsreformen. Samarbeidsavtalene skal fremme samhandlingen mellom kommuner og helseforetak ved Ä konkretisere oppgave- og ansvarsfordelingen, samt etablere gode samarbeidsrutiner pÄ sentrale samhandlingsomrÄder. UndersÞkelsen viser at samarbeidsavtalene oppleves som et egnet og nÞdvendig verktÞy for samhandling, har bidratt til en tydeliggjÞring av ansvar- og oppgavefordeling samt medfÞrt et bedre samarbeid mellom partene. Hovedutfordringen knyttet til avtalene er omfanget, bÄde antallet avtaler og detaljeringsgrad. At avtaleverket oppleves som omfattende, utfordrer hÄndteringen av avtalene (implementering og etterlevelse) og medfÞrer hÞy ressursbruk hos kommuner og helseforetak. Det synes Ä vÊre store variasjoner nÄr det gjelder hvorvidt avtalenes innhold er kjent, bÄde i kommunen og i helseforetaket. Generelt er det mest kjennskap til avtalene pÄ hÞyere nivÄ, men det er kun et fÄtall i hver organisasjon som kjenner helheten i avtaleverket. Samtidig er det delte meninger om hvorvidt det er behov for kjennskap til avtalene pÄ lavere nivÄ. Det er generelt mest kjennskap til avtalene som direkte berÞrer Þkonomi og pasientflyt. Avtaler som omhandler omrÄder hvor ansvars- og oppgavefordelingen er uklar er utfordrende Ä formulere og preges av vage og runde formuleringer. SÊrlig gjelder dette innenfor rehabilitering, psykisk helse og rus. Suksesskriterier knyttet direkte til avtalene er konkrete, tydelige og presise formuleringer. PÄ omrÄder med liten usikkerhet rundt ansvars- og oppgavefordelingen er det Þnskelig med tydelig ordbruk i avtalene hvor det fremgÄr klart hva oppgaven bestÄr av og hvem som har ansvaret, slik at det ikke er rom for tolkning. Et annet suksesskriterium er at avtalene ikke bÞr vÊre for omfattende og detaljerte. Suksesskriterier knyttet til strukturelle og prosessuelle forhold rundt avtalene er; fellesavtaler mellom kommuner i samme opptaksomrÄde, enighet mellom kommuner med fellesavtaler, personer med ulik fagbakgrunn samt beslutningsmakt og forhandlingskompetanse i avtale-/samarbeidsutvalg, jevnlige fysiske mÞter mellom partene, ledelsesforankring, bevissthet rundt likeverd og tilrettelegging for dette, en egen stilling/rolle med ansvar for samarbeidsavtalene for begge parter, tilstedevÊrelse fra kommunal side pÄ sykehuset i forbindelse med utskriving, gjensidig kompetanseutveksling og involvering av fastleger. Selv om avtaler oppleves som et nÞdvendig verktÞy, er de ikke tilstrekkelige for at intensjonene og forpliktelsene etterleves. Strukturelle og prosessuelle forhold er av stor betydning, bÄde for avtalenes utforming og etterlevelse. Det er variasjoner mellom kommuner og avtaleparter nÄr det gjelder organisering av samarbeidet og helsetjenestene, dette pÄvirker avtalenes innhold, utforming og bruk, samt samarbeidsrelasjonen mellom partene. Hovedvekten av tilbakemeldingene knyttet til erfaringer med avtalene er positive. Funnene i undersÞkelsen tyder pÄ at omrÄder som er konkretisert og tydeliggjort i avtalene, i hovedsak etterleves. Derimot er det tegn som tyder pÄ at omrÄder med uklare eller utilstrekkelige beskrivelser av oppgave- og ansvarsfordeling i avtalene, kan vÊre til hinder for etterlevelse

    Glaciotectonic disintegration of roches moutonnées during glacial ripping in east Sweden

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    Roches moutonnĂ©es are typical landforms of glacial erosion developed in hard rocks, with an asymmetric profile caused by abrasion and lee-side plucking. In eastern Sweden, some roches moutonnĂ©es show extensive damage, including open fractures, disintegration into blocks, fracture caves and short boulder trains. Disintegration increases along ice-flow directions during deglaciation of the last Weichselian Fennoscandian Ice Sheet, indicating a subglacial origin: limited edge rounding can be explained by a combination of hard rock, slow abrasion rates and disintegration just prior to deglaciation. The roches moutonnĂ©es initially developed in kernels of gneissic rocks with a wide fracture spacing (large block size) and interlocking fracture pattern, and hence high overall rock mass strength. Dilated fractures and ‘fracture caves’ occur up to 15 m below the ice-bed interface. It is proposed that hydraulic jacking by overpressured water opened up the rock mass along pre-existing fractures. Jacking reduced rock mass strength, allowing glaciotectonic deformation of the roches moutonnĂ©es. Uneven hydraulic jacking led to uplift of individual fracture-bound blocks above the pre-existing smooth, abraded surface of the roches moutonnĂ©es, creating blunt, step-like edges. These edges allowed high ice pushing forces to act on large blocks: where blocks extend into the deeper rock mass, they further aided the disintegration of the rock mass. The disintegrated roches moutonnĂ©es can be regarded as transient features between intact bedrock and complete disintegration into boulders. The jacking-disintegration-transport sequence is characteristic of glacial ripping and very different from classic lee-side plucking
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