45,104 research outputs found
Signal-Locality in Hidden-Variables Theories
We prove that all deterministic hidden-variables theories, that reproduce
quantum theory for a 'quantum equilibrium' distribution of hidden variables,
predict the existence of instantaneous signals at the statistical level for
hypothetical 'nonequilibrium ensembles'. This signal-locality theorem
generalises yet another property of the pilot-wave theory of de Broglie and
Bohm. The theorem supports the hypothesis that in the remote past the universe
relaxed to a state of statistical equilibrium (at the hidden-variable level) in
which nonlocality happens to be masked by quantum noise.Comment: 9 pages, latex, no figures. Revised, shortene
Issues and challenges of using web blogs as a medium for research communication.
The advent of web-based technology has initially allowed millions of users to get hold of immense information and to communicate worldwide. In the field of education, for example, web-based technology has brought about significant influence in terms of teaching and learning approaches (Supyan, 2003; Supyan & Roziana, 2001; Zuwati, 2006). In fact, web-based technology is also now popular as a medium for data collection among researchers (C. Cooper, Cooper, Del Junco, Shipp, Whitworth, & Cooper, 2006; White, Carey, & Dailey, 2000). The purpose of this paper is to report on both issues that need addressing, and challenges in using web blogs as a medium for communicating with respondents for research purposes. The issues and challenges discussed in the paper were based on the researchers' own experience in conducting data collection using a qualitative approach through web blog discussions. With the socio-cultural approach in view, some recommendations are also included as guidelines for those planning to use such web-based technology as a medium of data collection in research
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Business Grid Services
Grid services have come to represent the synthesis of web services and grid computing paradigms. Web services provide the means to modularize software, enabling loosely coupled and novel synthesis. Grid computing removes the binding between functional software components and specific hosting hardware, enabling software to be deployed dynamically over a network (e.g. intra-, extra- or inter-net). Applying the constructs of grid computing to the service orientation of enterprise software will allow business service networks to utilize more specialized services. An upper service ontology that enables business grid services to be described and then related to the grid hosting platform is presented. Explicit knowledge is required for enterprise software, hosting servers and the domain that can then be utilized by both SLA and reservation systems. The ontology presented is derived from and validated using a collection of web services taken from leading investment banks
The stellar populations of spiral galaxies
We have used a large sample of low-inclination spiral galaxies with
radially-resolved optical and near-infrared photometry to investigate trends in
star formation history with radius as a function of galaxy structural
parameters. A maximum likelihood method was used to match all the available
photometry of our sample to the colours predicted by stellar population
synthesis models. The use of simplistic star formation histories, uncertainties
in the stellar population models and regarding the importance of dust all
compromise the absolute ages and metallicities derived in this work, however
our conclusions are robust in a relative sense. We find that most spiral
galaxies have stellar population gradients, in the sense that their inner
regions are older and more metal rich than their outer regions. Our main
conclusion is that the surface density of a galaxy drives its star formation
history, perhaps through a local density dependence in the star formation law.
The mass of a galaxy is a less important parameter; the age of a galaxy is
relatively unaffected by its mass, however the metallicity of galaxies depends
on both surface density and mass. This suggests that galaxy mass-dependent
feedback is an important process in the chemical evolution of galaxies. In
addition, there is significant cosmic scatter suggesting that mass and density
may not be the only parameters affecting the star formation history of a
galaxy.Comment: 25 pages; 17 figures; re-submitted to MNRAS after replying to
referee's repor
Internal structures of electrons and photons: the concept of extended particles revisited
The theoretical foundations of quantum mechanics and de Broglie--Bohm
mechanics are analyzed and it is shown that both theories employ a formal
approach to microphysics. By using a realistic approach it can be established
that the internal structures of extended particles comply with a wave-equation.
Including external potentials yields the Schrodinger equation, which, in this
context, is arbitrary due to internal energy components. The statistical
interpretation of wave functions in quantum theory as well as Heisenberg's
uncertainty relations are shown to be an expression of this, fundamental,
arbitrariness. Electrons and photons can be described by an identical
formalism, providing formulations equivalent to the Maxwell equations.
Electrostatic interactions justify the initial assumption of electron-wave
stability: the stability of electron waves can be referred to vanishing
intrinsic fields of interaction. The theory finally points out some fundamental
difficulties for a fully covariant formulation of quantum electrodynamics,
which seem to be related to the existing infinity problems in this field.Comment: 14 pages (RevTeX one column) and 1 figure (eps). For a full list of
available papers see http://info.tuwien.ac.at/cms/wh
Statistical Mechanics of the Self-Gravitating Gas: I. Thermodynamic Limit and Phase Diagram
We provide a complete picture to the selfgravitating non-relativistic gas at
thermal equilibrium using Monte Carlo simulations, analytic mean field methods
(MF) and low density expansions. The system is shown to possess an infinite
volume limit in the grand canonical (GCE), canonical (CE) and microcanonical
(MCE) ensembles when(N, V) --> infinity, keeping N/ V^{1/3} fixed. We compute
the equation of state (we do not assume it as is customary), as well as the
energy, free energy, entropy, chemical potential, specific heats, compressibi-
lities and speed of sound;we analyze their properties, signs and singularities.
All physical quantities turn out to depend on a single variable eta = G m^2 N/
[V^{1/3} T] that is kept fixed in the N--> infinity and V --> infinity limit.
The system is in a gaseous phase for eta < eta_T and collapses into a dense
objet for eta > \eta_T in the CE with the pressure becoming large and negative.
At eta simeq eta_T the isothermal compressibility diverges. Our Monte Carlo
simulations yield eta_T simeq 1.515. PV/[NT] = f(eta) and all physical magni-
tudes exhibit a square root branch point at eta = eta_C > eta_T. The MF for
spherical symmetry yields eta_C = 1.561764.. while Monte Carlo on a cube yields
eta_C simeq 1.540.The function f(eta) has a second Riemann sheet which is only
physically realized in the MCE.In the MCE, the collapse phase transition takes
place in this second sheet near eta_MC = 1.26 and the pressure and temperature
are larger in the collapsed phase than in the gas phase.Both collapse phase
transitions (CE and MCE) are of zeroth order since the Gibbs free energy jumps
at the transitions. f(eta), obeys in MF a first order non-linear differential
equation of first kind Abel's type.The MF gives an extremely accurate picture
in agreement with Monte Carlo both in the CE and MCE.Comment: Latex, 51 pages, 15 .ps figures, to appear in Nucl. Phys.
The bimodal spiral galaxy surface brightness distribution
We have assessed the significance of Tully and Verheijen's (1997) bimodal
Ursa Major Cluster spiral galaxy near-infrared surface brightness distribution,
focussing on whether this bimodality is simply an artifact of small number
statistics. A Kolmogorov-Smirnov style of significance test shows that the
total distribution is fairly represented by a single-peaked distribution, but
that their isolated galaxy subsample (with no significant neighbours within a
projected distance of around 80 kpc) is bimodal at the 96 per cent level. We
have also investigated the assumptions underlying the isolated galaxy surface
brightness distribution, finding that the (often large) inclination corrections
used in the construction of this distribution reduce the significance of the
bimodality. We conclude that the Ursa Major Cluster dataset is insufficient to
establish the presence of a bimodal near-infrared surface brightness
distribution: an independent sample of around 100 isolated, low inclination
galaxies is required to establish bimodality at the 99 per cent level.Comment: 5 pages LaTeX; 2 embedded figures; re-submitted to MNRAS after
replying to referee's comment
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Effects of industrial heat treatments on the kinetics of inactivation of antimicrobial bovine milk xanthine oxidase.
Milk is a source of antimicrobial systems such as xanthine oxidoreductase, which has been proposed to modulate the oral and gut microbiota of infants. Heat treatments are applied to milk to ensure its microbial safety, however, the effects of heat on this antimicrobial enzyme are not known. The effects of batch pasteurization (BP), high-temperature short time (HTST), and ultra high temperature (UHT) on kinetics of inactivation of xanthine oxidase and its antimicrobial properties were determined. Xanthine oxidase activity was preserved by HTST (100%). Partial (8%) and nearly complete (95%) enzyme inactivation were observed for BP and UHT milks, respectively. K m values of 100âÎŒM and V max values of 6.85, 5.12, 6.31, and 0.40âÎŒmol/min/mg were determined for xanthine oxidase in raw, BP, HTST, and UHT milks, respectively. These results demonstrate that xanthine oxidase maintains apparent affinity and activity for its substrate when milk is treated by BP and HTST and yet the enzyme is inactivated with UHT. To investigate heat treatment-induced alterations in the biological activity of xanthine oxidase, heat treated milks were compared to raw milk for their ability to inhibit the growth of S. aureus. Raw, BP, and HTST milk xanthine oxidase efficiently inhibited S. aureus growth. However, these antibacterial properties were lost when milk was subjected to UHT. These results demonstrate that HTST and BP preserves bovine milk xanthine oxidase activity compared with UHT and that, the judicious selection of thermal treatments could be exploited to preserve the antimicrobial properties of bovine milk
Contextualist viewpoint to Greenberger-Horne-Zeilinger paradox
We present probabilistic analysis of the Greenberger-Horne-Zeilinger (GHZ)
scheme in the contextualist framework, namely under the assumption that
distributions of hidden variables depend on settings of measurement devices. On
one hand, we found classes of probability distributions of hidden variables for
that the GHZ scheme does not imply a contradiction between the local realism
and quantum formalism. On the other hand, we found classes of probability
distributions of hidden variables for that the GHZ scheme still induce such a
contradiction (despite variations of distributions). It is also demonstrated
that (well known in probability theory) singularity/absolute continuity
dichotomy for probability distributions is closely related to the GHZ paradox.
Our conjecture is that this GHZ-coupling between singularity/absolute
continuity dichotomy and incompatible/compatible measurements might be a
general feature of quantum theory.Comment: By taking into account contextualism of probabilities, i.e.,
dependence on complexes of experimental physical conditions, we resolve
GHZ-parado
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