396 research outputs found
Modelling of Thermal Sterilization of high-moisture snack foods: feasibility analysis and optimization
High-moisture snacks, such as steamed buns and rice cakes, are traditional and popular in Asian countries. However, their shelf life is short, primarily due to microbial spoilage. Current manufacturing methods address this shortcoming through the use of chemical preservatives. To satisfy consumers’ demand for preservative-free food, thermal sterilization of a model high-moisture snack (steamed rice cakes) is investigated in this work. Bacillus cereus spores are heat-resistant pathogens typically found in rice products; hence, they constitute a suitable candidate to assess the effectiveness of thermal sterilization. A validated combination of predicted temperature profile of rice cakes based on thermal properties extracted experimentally with thermal inactivation kinetics of B. cereus spores allows us to assess the sensitivity of processing conditions to sterilization efficiency. Using both experimentation and modelling, it is shown that enhancement of heat transfer by improving convection from the heating medium (either water or steam) has a limited effect on inactivation due to the intrinsic kinetics of spore inactivation
N=4 Supergravity Lagrangian for Type IIB Orientifold on T^6/Z_2 in Presence of Fluxes and D3-Branes
We derive the Lagrangian and the transformation laws of N=4 gauged
supergravity coupled to matter multiplets whose sigma-model of the scalars is
SU(1,1)/U(1)x SO(6,6+n)/SO(6)xSO(6+n) and which corresponds to the effective
Lagrangian of the Type IIB string compactified on the T^6/Z_2 orientifold with
fluxes turned on and in presence of n D3-branes. The gauge group is T^12 x G
where G is the gauge group on the brane and T^12 is the gauge group on the bulk
corresponding to the gauged translations of the R-R scalars coming from the R-R
four--form. The N=4 bulk sector of this theory can be obtained as a truncation
of the Scherk-Schwarz spontaneously broken N=8 supergravity. Consequently the
full bulk spectrum satisfies quadratic and quartic mass sum rules, identical to
those encountered in Scherk-Schwarz reduction gauging a flat group. This theory
gives rise to a no scale supergravity extended with partial super-Higgs
mechanism.Comment: 49 pages, LaTex, 2 figures. Misprints corrected, more comments adde
Special Geometry of Euclidean Supersymmetry I: Vector Multiplets
We construct the general action for Abelian vector multiplets in rigid
4-dimensional Euclidean (instead of Minkowskian) N=2 supersymmetry, i.e., over
space-times with a positive definite instead of a Lorentzian metric. The target
manifolds for the scalar fields turn out to be para-complex manifolds endowed
with a particular kind of special geometry, which we call affine special
para-Kahler geometry. We give a precise definition and develop the mathematical
theory of such manifolds. The relation to the affine special Kahler manifolds
appearing in Minkowskian N=2 supersymmetry is discussed. Starting from the
general 5-dimensional vector multiplet action we consider dimensional reduction
over time and space in parallel, providing a dictionary between the resulting
Euclidean and Minkowskian theories. Then we reanalyze supersymmetry in four
dimensions and find that any (para-)holomorphic prepotential defines a
supersymmetric Lagrangian, provided that we add a specific four-fermion term,
which cannot be obtained by dimensional reduction. We show that the Euclidean
action and supersymmetry transformations, when written in terms of
para-holomorphic coordinates, take exactly the same form as their Minkowskian
counterparts. The appearance of a para-complex and complex structure in the
Euclidean and Minkowskian theory, respectively, is traced back to properties of
the underlying R-symmetry groups. Finally, we indicate how our work will be
extended to other types of multiplets and to supergravity in the future and
explain the relevance of this project for the study of instantons, solitons and
cosmological solutions in supergravity and M-theory.Comment: 74 page
Atmospheric aerosols at the Pierre Auger Observatory and environmental implications
The Pierre Auger Observatory detects the highest energy cosmic rays.
Calorimetric measurements of extensive air showers induced by cosmic rays are
performed with a fluorescence detector. Thus, one of the main challenges is the
atmospheric monitoring, especially for aerosols in suspension in the
atmosphere. Several methods are described which have been developed to measure
the aerosol optical depth profile and aerosol phase function, using lasers and
other light sources as recorded by the fluorescence detector. The origin of
atmospheric aerosols traveling through the Auger site is also presented,
highlighting the effect of surrounding areas to atmospheric properties. In the
aim to extend the Pierre Auger Observatory to an atmospheric research platform,
a discussion about a collaborative project is presented.Comment: Regular Article, 16 pages, 12 figure
Selective quantum evolution of a qubit state due to continuous measurement
We consider a two-level quantum system (qubit) which is continuously measured
by a detector. The information provided by the detector is taken into account
to describe the evolution during a particular realization of measurement
process. We discuss the Bayesian formalism for such ``selective'' evolution of
an individual qubit and apply it to several solid-state setups. In particular,
we show how to suppress the qubit decoherence using continuous measurement and
the feedback loop.Comment: 15 pages (including 9 figures
Non-compact Groups, Coherent States, Relativistic Wave Equations and the Harmonic Oscillator II: Physical and Geometrical Considerations
The physical meaning of the particularly simple non-degenerate supermetric,
introduced in the previous part by the authors, is elucidated and the possible
connection with processes of topological origin in high energy physics is
analyzed and discussed. New possible mechanism of the localization of the
fields in a particular sector of the supermanifold is proposed and the
similarity and differences with a 5-dimensional warped model are shown. The
relation with gauge theories of supergravity based in the group is
explicitly given and the possible original action is presented. We also show
that in this non-degenerate super-model the physic states, in contrast with the
basic states, are observables and can be interpreted as tomographic projections
or generalized representations of operators belonging to the metaplectic group
. The advantage of geometrical formulations based on non-degenerate
super-manifolds over degenerate ones is pointed out and the description and the
analysis of some interesting aspects of the simplest Riemannian superspaces are
presented from the point of view of the possible vacuum solutions.Comment: Stile of the text improved in Journa
The ANTARES Optical Beacon System
ANTARES is a neutrino telescope being deployed in the Mediterranean Sea. It
consists of a three dimensional array of photomultiplier tubes that can detect
the Cherenkov light induced by charged particles produced in the interactions
of neutrinos with the surrounding medium. High angular resolution can be
achieved, in particular when a muon is produced, provided that the Cherenkov
photons are detected with sufficient timing precision. Considerations of the
intrinsic time uncertainties stemming from the transit time spread in the
photomultiplier tubes and the mechanism of transmission of light in sea water
lead to the conclusion that a relative time accuracy of the order of 0.5 ns is
desirable. Accordingly, different time calibration systems have been developed
for the ANTARES telescope. In this article, a system based on Optical Beacons,
a set of external and well-controlled pulsed light sources located throughout
the detector, is described. This calibration system takes into account the
optical properties of sea water, which is used as the detection volume of the
ANTARES telescope. The design, tests, construction and first results of the two
types of beacons, LED and laser-based, are presented.Comment: 21 pages, 18 figures, submitted to Nucl. Instr. and Meth. Phys. Res.
Single Spin Asymmetry in Polarized Proton-Proton Elastic Scattering at GeV
We report a high precision measurement of the transverse single spin
asymmetry at the center of mass energy GeV in elastic
proton-proton scattering by the STAR experiment at RHIC. The was measured
in the four-momentum transfer squared range \GeVcSq, the region of a significant interference between the
electromagnetic and hadronic scattering amplitudes. The measured values of
and its -dependence are consistent with a vanishing hadronic spin-flip
amplitude, thus providing strong constraints on the ratio of the single
spin-flip to the non-flip amplitudes. Since the hadronic amplitude is dominated
by the Pomeron amplitude at this , we conclude that this measurement
addresses the question about the presence of a hadronic spin flip due to the
Pomeron exchange in polarized proton-proton elastic scattering.Comment: 12 pages, 6 figure
Longitudinal double-spin asymmetry and cross section for inclusive neutral pion production at midrapidity in polarized proton collisions at sqrt(s) = 200 GeV
We report a measurement of the longitudinal double-spin asymmetry A_LL and
the differential cross section for inclusive Pi0 production at midrapidity in
polarized proton collisions at sqrt(s) = 200 GeV. The cross section was
measured over a transverse momentum range of 1 < p_T < 17 GeV/c and found to be
in good agreement with a next-to-leading order perturbative QCD calculation.
The longitudinal double-spin asymmetry was measured in the range of 3.7 < p_T <
11 GeV/c and excludes a maximal positive gluon polarization in the proton. The
mean transverse momentum fraction of Pi0's in their parent jets was found to be
around 0.7 for electromagnetically triggered events.Comment: 6 pages, 3 figures, submitted to Phys. Rev. D (RC
High non-photonic electron production in + collisions at = 200 GeV
We present the measurement of non-photonic electron production at high
transverse momentum ( 2.5 GeV/) in + collisions at
= 200 GeV using data recorded during 2005 and 2008 by the STAR
experiment at the Relativistic Heavy Ion Collider (RHIC). The measured
cross-sections from the two runs are consistent with each other despite a large
difference in photonic background levels due to different detector
configurations. We compare the measured non-photonic electron cross-sections
with previously published RHIC data and pQCD calculations. Using the relative
contributions of B and D mesons to non-photonic electrons, we determine the
integrated cross sections of electrons () at 3 GeV/10 GeV/ from bottom and charm meson decays to be = 4.0({\rm
stat.})({\rm syst.}) nb and =
6.2({\rm stat.})({\rm syst.}) nb, respectively.Comment: 17 pages, 17 figure
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