930 research outputs found
Perceptions and behaviors related to hand hygiene for the prevention of H1N1 influenza transmission among Korean university students during the peak pandemic period
<p>Abstract</p> <p>Background</p> <p>This study was performed to better assess the perceptions, motivating factors, and behaviors associated with the use of hand washing to prevent H1N1 influenza transmission during the peak pandemic period in Korea.</p> <p>Methods</p> <p>A cross-sectional survey questionnaire was completed by 942 students at a university campus in Suwon, Korea, between December 1 and 8, 2009. The survey included questions regarding individual perceptions, motivating factors, and behaviors associated with hand washing for the prevention of H1N1 influenza transmission.</p> <p>Results</p> <p>Compared to one year prior, 30.3% of participants reported increasing their hand washing frequency. Female students were more likely to practice more frequent hand washing. Women also perceived the effectiveness of hand washing to be lower, and illness severity and personal susceptibility to H1N1 infection to be higher. Study participants who were female (OR: 1.79-3.90) who perceived of hand washing to be effective (OR: 1.34-12.15) and illness severity to be greater (OR: 1.00-3.12) washed their hands more frequently.</p> <p>Conclusions</p> <p>Korean students increased their frequency of hand hygiene practices during the pandemic, with significant gender differences existing in the attitudes and behaviors related to the use of hand hygiene as a means of disease prevention. Here, the factors that affected hand washing behavior were similar to those identified at the beginning of the H1N1 or SARS pandemics, suggesting that public education campaigns regarding hand hygiene are effective in altering individual hand hygiene habits during the peak periods of influenza transmission.</p
Fermions and Type IIB Supergravity On Squashed Sasaki-Einstein Manifolds
We discuss the dimensional reduction of fermionic modes in a recently found
class of consistent truncations of type IIB supergravity compactified on
squashed five-dimensional Sasaki-Einstein manifolds. We derive the lower
dimensional equations of motion and effective action, and comment on the
supersymmetry of the resulting theory, which is consistent with N=4 gauged
supergravity in , coupled to two vector multiplets. We compute fermion
masses by linearizing around two vacua of the theory: one that breaks
N=4 down to N=2 spontaneously, and a second one which preserves no
supersymmetries. The truncations under consideration are noteworthy in that
they retain massive modes which are charged under a U(1) subgroup of the
-symmetry, a feature that makes them interesting for applications to
condensed matter phenomena via gauge/gravity duality. In this light, as an
application of our general results we exhibit the coupling of the fermions to
the type IIB holographic superconductor, and find a consistent further
truncation of the fermion sector that retains a single spin-1/2 mode.Comment: 43 pages, 2 figures, PDFLaTeX; v2: added references, typos corrected,
minor change
Hydrodynamics from charged black branes
We extend the recent work on fluid-gravity correspondence to charged
black-branes by determining the metric duals to arbitrary charged fluid
configuration up to second order in the boundary derivative expansion. We also
derive the energy-momentum tensor and the charge current for these
configurations up to second order in the boundary derivative expansion. We find
a new term in the charge current when there is a bulk Chern-Simons interaction
thus resolving an earlier discrepancy between thermodynamics of charged
rotating black holes and boundary hydrodynamics. We have also confirmed that
all our expressions are covariant under boundary Weyl-transformations as
expected.Comment: 0+ 31 Pages; v2: 0+33 pages, typos corrected and new sections (in
appendix) added; v3:published versio
Constructing Lifshitz solutions from AdS
Under general assumptions, we show that a gravitational theory in d+1
dimensions admitting an AdS solution can be reduced to a d-dimensional theory
containing a Lifshitz solution with dynamical exponent z=2. Working in a d=4,
N=2 supergravity setup, we prove that if the AdS background is N=2
supersymmetric, then the Lifshitz geometry preserves 1/4 of the supercharges,
and we construct the corresponding Killing spinors. We illustrate these results
in examples from supersymmetric consistent truncations of type IIB
supergravity, enhancing the class of known 4-dimensional Lifshitz solutions of
string theory. As a byproduct, we find a new AdS4 x S1 x T(1,1) solution of
type IIB.Comment: 29 pages, no figures; v2 minor corrections, a reference adde
Lifshitz black holes in string theory
We provide the first black hole solutions with Lifshitz asymptotics found in
string theory. These are expected to be dual to models enjoying anisotropic
scale invariance with dynamical exponent z=2 at finite temperature. We employ a
consistent truncation of type IIB supergravity to four dimensions with an
arbitrary 5-dimensional Einstein manifold times a circle as internal geometry.
New interesting features are found that significantly differ from previous
results in phenomenological models. In particular, small black holes are shown
to be thermodynamically unstable, analogously to the usual AdS-Schwarzschild
black holes, and extremality is never reached. This signals a possible
Hawking-Page like phase transition at low temperatures.Comment: 19 pages, 7 figures. v2 references adde
Holographic Lovelock Gravities and Black Holes
We study holographic implications of Lovelock gravities in AdS spacetimes.
For a generic Lovelock gravity in arbitrary spacetime dimensions we formulate
the existence condition for asymptotically AdS black holes. We consider small
fluctuations around these black holes and determine the constraint on Lovelock
parameters by demanding causality of the boundary theory. For the case of cubic
Lovelock gravity in seven spacetime dimensions we compute the holographic Weyl
anomaly and determine the three point functions of the stress energy tensor in
the boundary CFT. Remarkably, these correlators happen to satisfy the same
relation as the one imposed by supersymmetry. We then compute the energy flux;
requiring it to be positive is shown to be completely equivalent to requiring
causality of the finite temperature CFT dual to the black hole. These
constraints are not stringent enough to place any positive lower bound on the
value of viscosity. Finally, we conjecture an expression for the energy flux
valid for any Lovelock theory in arbitrary dimensions.Comment: 31 pages, 1 figure, harvmac, references added, calculation of
viscosity/entropy ratio include
Moduli and electromagnetic black brane holography
We investigate the thermodynamic and hydrodynamic properties of 4-dimensional
gauge theories with finite electric charge density in the presence of a
constant magnetic field. Their gravity duals are planar magnetically and
electrically charged AdS black holes in theories that contain a gauge
Chern-Simons term. We present a careful analysis of the near horizon geometry
of these black branes at finite and zero temperature for the case of a scalar
field non-minimally coupled to the electromagnetic field. With the knowledge of
the near horizon data, we obtain analytic expressions for the shear viscosity
coefficient and entropy density, and also study the effect of a generic set of
four derivative interactions on their ratio. We also comment on the attractor
flows of the extremal solutions.Comment: 39 pages, no figures; v2: minor changes, refs. added; v3: typo fixed;
v4: a proof for decoupling of the viscosity mode added in appendix, matches
the published versio
Universality and exactness of Schrodinger geometries in string and M-theory
We propose an organizing principle for classifying and constructing
Schrodinger-invariant solutions within string theory and M-theory, based on the
idea that such solutions represent nonlinear completions of linearized vector
and graviton Kaluza-Klein excitations of AdS compactifications. A crucial
simplification, derived from the symmetry of AdS, is that the nonlinearities
appear only quadratically. Accordingly, every AdS vacuum admits infinite
families of Schrodinger deformations parameterized by the dynamical exponent z.
We exhibit the ease of finding these solutions by presenting three new
constructions: two from M5 branes, both wrapped and extended, and one from the
D1-D5 (and S-dual F1-NS5) system. From the boundary perspective, perturbing a
CFT by a null vector operator can lead to nonzero beta-functions for spin-2
operators; however, symmetry restricts them to be at most quadratic in
couplings. This point of view also allows us to easily prove nonrenormalization
theorems: for any Sch(z) solution of two-derivative supergravity constructed in
the above manner, z is uncorrected to all orders in higher derivative
corrections if the deforming KK mode lies in a short multiplet of an AdS
supergroup. Furthermore, we find infinite classes of 1/4 BPS solutions with
4-,5- and 7-dimensional Schrodinger symmetry that are exact.Comment: 31 pages, plus appendices; v2, minor corrections, added refs, slight
change in interpretation in section 2.3, new Schrodinger and Lifshitz
solutions included; v3, clarifications in sections 2 and 3 regarding
existence of solutions and multi-trace operator
Excess Higgs Production in Neutralino Decays
The ATLAS and CMS experiments have recently claimed discovery of a Higgs
boson-like particle at ~5 sigma confidence and are beginning to test the
Standard Model predictions for its production and decay. In a variety of
supersymmetric models, a neutralino NLSP can decay dominantly to the Higgs and
the LSP. In natural SUSY models, a light third generation squark decaying
through this chain can lead to large excess Higgs production while evading
existing BSM searches. Such models can be observed at the 8 TeV LHC in channels
exploiting the rare diphoton decays of the Higgs produced in the cascade decay.
Identifying a diphoton resonance in association with missing energy, a lepton,
or b-tagged jets is a promising search strategy for discovery of these models,
and would immediately signal new physics involving production of a Higgs boson.
We also discuss the possibility that excess Higgs production in these SUSY
decays can be responsible for enhancements of up to 50% over the SM prediction
for the observed rate in the existing inclusive diphoton searches, a scenario
which would likely by the end of the 8 TeV run be accompanied by excesses in
the diphoton + lepton/MET and SUSY multi-lepton/b searches and a potential
discovery in a diphoton + 2b search.Comment: 42 pages, 19 figure
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