2,190 research outputs found

    Morphine Metabolism in Human Skin Microsomes

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    For patients with severe skin wounds, topically applied morphine is an option to induce efficient analgesia due to the presence of opioid receptors in the skin. However, for topical administration it is important to know whether the substance is biotransformed in the skin as this can eventually reduce the concentration of the active agent considerably. We use skin microsomes to elucidate the impact of skin metabolism on the activity of topically applied morphine. We are able to demonstrate that morphine is only glucuronidated in traces, indicating that the biotransformation in the skin can be neglected when morphine is applied topically. Hence, there is no need to take biotransformation into account when setting up the treatment regimen. Copyright (C) 2012 S. Karger AG, Base

    On Long-Range Order in Low-Dimensional Lattice-Gas Models of Nematic Liquid Crystals

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    The problem of the orientational ordering transition for lattice-gas models of liquid crystals is discussed in the low-dimensional case d=1,2d=1,2. For isotropic short-range interactions, orientational long-range order at finite temperature is excluded for any packing of molecules on the lattice ZdZ^d; on the other hand, for reflection-positive long-range isotropic interactions, we prove existence of an orientational ordering transition for high packing (μ>μ0\mu > \mu_0) and low temperatures (β>βc(μ)\beta > \beta_c(\mu)).Comment: 11 page

    NVU dynamics. I. Geodesic motion on the constant-potential-energy hypersurface

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    An algorithm is derived for computer simulation of geodesics on the constant potential-energy hypersurface of a system of N classical particles. First, a basic time-reversible geodesic algorithm is derived by discretizing the geodesic stationarity condition and implementing the constant potential energy constraint via standard Lagrangian multipliers. The basic NVU algorithm is tested by single-precision computer simulations of the Lennard-Jones liquid. Excellent numerical stability is obtained if the force cutoff is smoothed and the two initial configurations have identical potential energy within machine precision. Nevertheless, just as for NVE algorithms, stabilizers are needed for very long runs in order to compensate for the accumulation of numerical errors that eventually lead to "entropic drift" of the potential energy towards higher values. A modification of the basic NVU algorithm is introduced that ensures potential-energy and step-length conservation; center-of-mass drift is also eliminated. Analytical arguments confirmed by simulations demonstrate that the modified NVU algorithm is absolutely stable. Finally, simulations show that the NVU algorithm and the standard leap-frog NVE algorithm have identical radial distribution functions for the Lennard-Jones liquid

    How to be fairer

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    We confront the philosophical literature on fair division problems with axiomatic and game-theoretic work in economics. Firstly, we show that the proportionality method advocated in Curtis (in Analysis 74:417–57, 2014) is not implied by a general principle of fairness, and that the proportional rule cannot be explicated axiomatically from that very principle. Secondly, we suggest that Broome’s (in Proc Aristot Soc 91:87–101, 1990) notion of claims is too restrictive and that game-theoretic approaches can rectify this shortcoming. More generally, we argue that axiomatic and game-theoretic work in economics is an indispensable ingredient of any theorizing about fair division problems and allocative justice

    Theories of Fairness and Aggregation

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    We investigate the issue of aggregativity in fair division problems from the perspective of cooperative game theory and Broomean theories of fairness. Paseau and Saunders (Utilitas 27:460–469, 2015) proved that no non-trivial theory of fairness can be aggregative and conclude that theories of fairness are therefore problematic, or at least incomplete. We observe that there are theories of fairness, particularly those that are based on cooperative game theory, that do not face the problem of non-aggregativity. We use this observation to argue that the universal claim that no non-trivial theory of fairness can guarantee aggregativity is false. Paseau and Saunders’s mistaken assertion can be understood as arising from a neglect of the (cooperative) games approach to fair division. Our treatment has two further pay-offs: for one, we give an accessible introduction to the (cooperative) games approach to fair division, whose significance has hitherto not been appreciated by philosophers working on fairness. For another, our discussion explores the issue of aggregativity in fair division problems in a comprehensive fashion

    Dividing the indivisible: Apportionment and philosophical theories of fairness

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    Philosophical theories of fairness propose to divide a good that several individuals have a claim to in proportion to the strength of their respective claims. We suggest that currently, these theories face a dilemma when dealing with a good that is indivisible. On the one hand, theories of fairness that use weighted lotteries are either of limited applicability or fall prey to an objection by Brad Hooker. On the other hand, accounts that do without weighted lotteries fall prey to three fairness paradoxes. We demonstrate that division methods from apportionment theory, which has hitherto been ignored by philosophical theories of fairness, can be used to provide fair division for indivisible goods without weighted lotteries and without fairness paradoxes

    Entropy-driven phase transition in a polydisperse hard-rods lattice system

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    We study a system of rods on the 2d square lattice, with hard-core exclusion. Each rod has a length between 2 and N. We show that, when N is sufficiently large, and for suitable fugacity, there are several distinct Gibbs states, with orientational long-range order. This is in sharp contrast with the case N=2 (the monomer-dimer model), for which Heilmann and Lieb proved absence of phase transition at any fugacity. This is the first example of a pure hard-core system with phases displaying orientational order, but not translational order; this is a fundamental characteristic feature of liquid crystals

    Hybrid systems: a real-time interface to control engineering

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    This paper gives an introduction to a general hybrid systems model for definition of system requirements and a corresponding software architecture together with an example of their specialization for use in implementing a modeswitching controller for a hydraulic cylinder. 1. Introduction An important application area for real-time computing is embedded systems where the computing system provides intelligent control of a mechanical, chemical etc. plant or device. The software requirements for such applications depend heavily on the properties of the plant. These properties are usually investigated by control engineers that base their work on the theory of dynamic systems [3, 9]. The mathematical tool for this work is thus mathematical analysis, in particular the theory of differential equations. If the models are linear differential equations, there are standard techniques for implementing a corresponding discrete, sampled system in the form of a computer program, and the work for the s..

    Breastfeeding practices in the United Kingdom: Is the neighbourhood context important?

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    Breastfeeding is an important public health issue worldwide. Breastfeeding rates in the United Kingdom, particularly for exclusive breastfeeding, are low compared with other OECD countries, despite its wide-ranging health benefits for both mother and child. There is evidence that deprivation in the structural and social organisation of neighbourhoods is associated with adverse child outcomes. This study aimed to explore whether breastfeeding initiation, exclusive breastfeeding for at least 3 months, and any type of breastfeeding for at least 6 months were associated with neighbourhood context measured by neighbourhood deprivation and maternal neighbourhood perceptions in a nationally representative U.K. SAMPLE: A cross-sectional analysis was conducted using data from the Millennium Cohort Study. Logistic regression was carried out on a sample of 17,308 respondents, adjusting for individual- and familial-level socio-demographic characteristics. Neighbourhood deprivation was independently and inversely associated with breastfeeding initiation. Compared with the least deprived areas, the likelihood of initiating breastfeeding was 40% lower in the most deprived neighbourhoods (OR: 0.60, 95% CI [0.50, 0.72]). The relationship between both exclusive and any type of breastfeeding at 3 and 6 months respectively with neighbourhood deprivation after adjustment for potential confounders was not entirely linear. Breastfeeding initiation (OR: 0.78, 95% CI [0.71, 0.85]), exclusivity for 3 months (OR: 0.84, 95% CI [0.75, 0.95]), and any breastfeeding for 6 months (OR: 0.82, 95% CI [0.73, 0.93]) were each reduced by about 20% among mothers who perceived their neighbourhoods lacking safe play areas for children. Policies to improve breastfeeding rates should consider area-based approaches and the broader determinants of social inequalities
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