59,598 research outputs found
Murder by fake drugs - prioritising the measures available to tackle the problem [Electronic Letter]
Polyakov loop potential at finite density
The Polyakov loop potential serves to distinguish between the confined
hadronic and the deconfined quark-gluon plasma phases of QCD. For Nf=2+1 quark
flavors with physical masses we determine the Polyakov loop potential at finite
temperature and density and extract the location of the deconfinement
transition. We find a cross-over at small values of the chemical potential
running into a critical end-point at mu/T > 1.Comment: 5 pages, 9 figure
âBinge drinking? Itâs good, itâs harmless funâ:a discourse analysis of accounts of female undergraduate drinking in Scotland
Binge drinking in young people, particularly females and students, is a source of some concern to those engaged in health education. The concept is usually defined in terms of quantities of alcohol consumed within a relatively short space of time. Research suggests that reasons for drinking are varied, and are likely to be influenced by culture and context. This study aimed to explore issues important to female undergraduate students in Scotland. Semi-structured interviews were carried out with 19 participants who were asked to describe what they understand by the term âbinge drinkingâ, why they drink and what might trigger excessive consumption. Discourse analysis was used to explore the possible âfunctionsâ of what was said, as well as the content. Participants showed sensitivity to how others might interpret their responses. They described binge drinking in terms of its behavioural effects rather than quantities consumed. Crucially, they positioned themselves outside the categories of âseriousâ or âanti-socialâ drinkers. These findings have important implications for our understanding of factors influencing drinking behaviour in this group of people, which in turn impacts on the potential design of health-enhancing interventions. The study also demonstrates the usefulness of a discourse analytic approach to accounts of drinking behaviour
Improved Upper Bounds to the Causal Quadratic Rate-Distortion Function for Gaussian Stationary Sources
We improve the existing achievable rate regions for causal and for zero-delay
source coding of stationary Gaussian sources under an average mean squared
error (MSE) distortion measure. To begin with, we find a closed-form expression
for the information-theoretic causal rate-distortion function (RDF) under such
distortion measure, denoted by , for first-order Gauss-Markov
processes. Rc^{it}(D) is a lower bound to the optimal performance theoretically
attainable (OPTA) by any causal source code, namely Rc^{op}(D). We show that,
for Gaussian sources, the latter can also be upper bounded as Rc^{op}(D)\leq
Rc^{it}(D) + 0.5 log_{2}(2\pi e) bits/sample. In order to analyze
for arbitrary zero-mean Gaussian stationary sources, we
introduce \bar{Rc^{it}}(D), the information-theoretic causal RDF when the
reconstruction error is jointly stationary with the source. Based upon
\bar{Rc^{it}}(D), we derive three closed-form upper bounds to the additive rate
loss defined as \bar{Rc^{it}}(D) - R(D), where R(D) denotes Shannon's RDF. Two
of these bounds are strictly smaller than 0.5 bits/sample at all rates. These
bounds differ from one another in their tightness and ease of evaluation; the
tighter the bound, the more involved its evaluation. We then show that, for any
source spectral density and any positive distortion D\leq \sigma_{x}^{2},
\bar{Rc^{it}}(D) can be realized by an AWGN channel surrounded by a unique set
of causal pre-, post-, and feedback filters. We show that finding such filters
constitutes a convex optimization problem. In order to solve the latter, we
propose an iterative optimization procedure that yields the optimal filters and
is guaranteed to converge to \bar{Rc^{it}}(D). Finally, by establishing a
connection to feedback quantization we design a causal and a zero-delay coding
scheme which, for Gaussian sources, achieves...Comment: 47 pages, revised version submitted to IEEE Trans. Information Theor
Phenomenological Aspects of F-theory
Stabilizing a heterotic string vacuum with a large expectation value of the
dilaton and simultaneously breaking low-energy supersymmetry is a long-standing
problem of string phenomenology. We reconsider these issues in light of the
recent developments in F-theory.Comment: 11 pages, phyzzx macro
Local discontinuous Galerkin methods for fractional ordinary differential equations
This paper discusses the upwinded local discontinuous Galerkin methods for
the one-term/multi-term fractional ordinary differential equations (FODEs). The
natural upwind choice of the numerical fluxes for the initial value problem for
FODEs ensures stability of the methods. The solution can be computed element by
element with optimal order of convergence in the norm and
superconvergence of order at the downwind point of each
element. Here is the degree of the approximation polynomial used in an
element and () represents the order of the one-term
FODEs. A generalization of this includes problems with classic 'th-term
FODEs, yielding superconvergence order at downwind point as
. The underlying mechanism of the
superconvergence is discussed and the analysis confirmed through examples,
including a discussion of how to use the scheme as an efficient way to evaluate
the generalized Mittag-Leffler function and solutions to more generalized
FODE's.Comment: 17 pages, 7 figure
The Hamiltonian Formulation of Higher Order Dynamical Systems
Using Dirac's approach to constrained dynamics, the Hamiltonian formulation
of regular higher order Lagrangians is developed. The conventional description
of such systems due to Ostrogradsky is recovered. However, unlike the latter,
the present analysis yields in a transparent manner the local structure of the
associated phase space and its local sympletic geometry, and is of direct
application to {\em constrained\/} higher order Lagrangian systems which are
beyond the scope of Ostrogradsky's approach.Comment: 17 pages. Revised: references adde
Critical Point and Deconfinement from Dyson-Schwinger Equations
We employ the Dyson-Schwinger equations for quark and gluon propagators in
order to study QCD with 2+1 flavours at finite temperature and density. In a
suitable truncation for these equations, we determine the position of the
critical end-point as well as the deconfinement temperature at all chemical
potentials. For the latter, the Polyakov-loop potential is obtained from the
QCD propagators. This is possible for the first time at finite chemical
potential, with implications for effective models.Comment: Proceedings for the 8th International Workshop on Critical Point and
Onset of Deconfinement (CPOD 2013). 5 pages, 5 figure
Development of mercuric iodide uncooled x ray detectors and spectrometers
The results obtained in the development of miniature, lowpower, light weight mercuric iodide, HgI2, x ray spectrometers for future space missions are summarized. It was demonstrated that HgI2 detectors can be employed in a high resolution x ray spectrometer, operating in a scanning electron microscope. Also, the development of HgI2 x ray detectors to augment alpha backscattering spectrometers is discussed. These combination instruments allow for the identification of all chemical elements, with the possible exception of hydrogen, and their respective concentrations. Additionally, further investigations of questions regarding radiation damage effects in the HgI2 x ray detectors are reported
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