250 research outputs found
Noncommutativity from the string perspective: modification of gravity at a mm without mm sized extra dimensions
We explore how the IR pathologies of noncommutative field theory are resolved
when the theory is realized as open strings in background B-fields:
essentially, since the IR singularities are induced by UV/IR mixing, string
theory brings them under control in much the same way as it does the UV
singularities. We show that at intermediate scales (where the Seiberg-Witten
limit is a good approximation) the theory reproduces the noncommutative field
theory with all the (un)usual features such as UV/IR mixing, but that outside
this regime, in the deep infra-red, the theory flows continuously to the
commutative theory and normal Wilsonian behaviour is restored. The resulting
low energy physics resembles normal commutative physics, but with additional
suppressed Lorentz violating operators. We also show that the phenomenon of
UV/IR mixing occurs for the graviton as well, with the result that, in
configurations where Planck's constant receives a significant one-loop
correction (for example brane-induced gravity), the distance scale below which
gravity becomes non-Newtonian can be much greater than any compact dimensions.Comment: 30 pages. Slight revision: clarified some points and added a
referenc
Rotating strings and D2-branes in type IIA reduction of M-theory on G2 manifold and their semiclassical limits
We consider rotating strings and D2-branes on type IIA background, which
arises as dimensional reduction of M-theory on manifold of G2 holonomy, dual to
N=1 gauge theory in four dimensions. We obtain exact solutions and explicit
expressions for the conserved charges. By taking the semiclassical limit, we
show that the rotating strings can reproduce only one type of semiclassical
behavior, exhibited by rotating M2-branes on G2 manifolds. Our further
investigation leads to the conclusion that the rotating D2-branes reproduce two
types of the semiclassical energy-charge relations known for membranes in
eleven dimensions.Comment: LaTeX, 29 pages, no figures; V2:comments added; V3:no changes, to
appear in JHE
Infant feeding practices in a multi-ethnic Asian cohort: the GUSTO study
The optimal introduction of complementary foods provides infants with nutritionally balanced diets and establishes healthy eating habits. The documentation of infant feeding practices in multi-ethnic Asian populations is limited. In a Singapore cohort study (GUSTO), 842 mother-infant dyads were interviewed regarding their feeding practices when the infants were aged 9 and 12 months. In the first year, 20.5% of infants were given dietary supplements, while 5.7% took probiotics and 15.7% homeopathic preparations. At age 9 months, 45.8% of infants had seasonings added to their foods, increasing to 56.3% at 12 months. At age 12 months, 32.7% of infants were given blended food, although 92.3% had begun some form of self-feeding. Additionally, 87.4% of infants were fed milk via a bottle, while a third of them had food items added into their bottles. At both time points, more than a third of infants were provided sweetened drinks via the bottle. Infants of Indian ethnicity were more likely to be given dietary supplements, have oil and seasonings added to their foods and consumed sweetened drinks from the bottle (p < 0.001). These findings provide a better understanding of variations in infant feeding practices, so that healthcare professionals can offer more targeted and culturally-appropriate advice
Semiclassical Strings, Dipole Deformations of N=1 SYM and Decoupling of KK Modes
In this paper we investigate the recently found -deformed
Maldacena-Nunez background by studying the behavior of different semiclassical
string configurations. This background is conjectured to be dual to dipole
deformations of SYM. We compare our results to those in the pure
Maldacena-Nunez background and show that the energies of our string
configurations are higher than in the undeformed background. Thinking in the
lines of (hep-th/0505100) we argue that this is an evidence for better
decoupling of the Kaluza-Klein modes from the pure SYM theory excitations.
Moreover we are able to find a limit of the background in which the string
energy is independent of , these strings are interpreted as
corresponding to pure gauge theory effects.Comment: 31 pages, references added, new solutions in Section 7 presented, an
appendix added, to appear in JHE
The holographic superconductors in higher-dimensional AdS soliton
We explore the behaviors of the holographic superconductors at zero
temperature for a charged scalar field coupled to a Maxwell field in
higher-dimensional AdS soliton spacetime via analytical way. In the probe
limit, we obtain the critical chemical potentials increase linearly as a total
dimension grows up. We find that the critical exponent for condensation
operator is obtained as 1/2 independently of , and the charge density is
linearly related to the chemical potential near the critical point.
Furthermore, we consider a slightly generalized setup the
Einstein-Power-Maxwell field theory, and find that the critical exponent for
condensation operator is given as in terms of a power parameter
of the Power-Maxwell field, and the charge density is proportional to the
chemical potential to the power of .Comment: LaTeX, 16 pages, 5 figures, typos corrected, one reference added,
version to appear in European Physical Journal
UV-divergences of Wilson Loops for Gauge/Gravity Duality
We analyze the structure of the UV divergences of the Wilson loop for a
general gauge/gravity duality. We find that, due to the presence of a
nontrivial NSNS B-field and metric, new divergences that cannot be subtracted
out by the conventional Legendre transform may arise. We also derive conditions
on the B-field and the metric, which when satisfied, the leading UV divergence
will become linear, and can be cancelled out by choosing the boundary condition
of the string appropriately. Our results, together with the recent result of
arXiv:0807.5127, where the effect of a nontrivial dilaton on the structure of
UV divergences in Wilson loop is analysed, allow us to conclude that Legendre
transform is at best capable of cancelling the linear UV divergences arising
from the area of the worldsheet, but is incapable to handle the divergences
associated with the dilaton or the B-field in general. We also solve the
conditions for the cancellation of the leading linear divergences generally and
find that many well-known supergravity backgrounds are of these kinds,
including examples such as the Sakai-Sugimoto QCD model or N=1 duality with
Sasaki-Einstein spaces. We also point out that Wilson loop in the
Klebanov-Strassler background have a divergence associated with the B-field
which cannot be cancelled away with the Legendre transform. Finally we end with
some comments on the form of the Wilson loop operator in the ABJM
superconformal Chern-Simons theory.Comment: 26 pages. LaTeX. v2: reference added. version to appear in JHE
Charmless hadronic decays and new physics effects in the general two-Higgs doublet models
Based on the low-energy effective Hamiltonian with the generalized
factorization, we calculate the new physics contributions to the branching
ratios of the two-body charmless hadronic decays of and mesons
induced by the new gluonic and electroweak charged-Higgs penguin diagrams in
the general two-Higgs doublet models (models I, II and III). Within the
considered parameter space, we find that: (a) the new physics effects from new
gluonic penguin diagrams strongly dominate over those from the new -
and - penguin diagrams; (b) in models I and II, new physics contributions
to most studied B meson decay channels are rather small in size: from -15% to
20%; (c) in model III, however, the new physics enhancements to the
penguin-dominated decay modes can be significant, , and
therefore are measurable in forthcoming high precision B experiments; (d) the
new physics enhancements to ratios {\cal B}(B \to K \etap) are significant in
model III, , and hence provide a simple and plausible new
physics interpretation for the observed unexpectedly large B \to K \etap
decay rates; (e) the theoretical predictions for and
in model III are still consistent with the data
within errors; (f) the significant new physics enhancements to the
branching ratios of and decays are helpful to improve the
agreement between the data and the theoretical predictions; (g) the theoretical
predictions of in the 2HDM's are generally
consistent with experimental measurements and upper limits ()Comment: 55 pages, Latex file, 17 PS and EPS figures. With minor corrections,
final version to be published in Phys.Rev. D. Repot-no: PKU-TH-2000-4
Statins for extension of disability-free survival and primary prevention of cardiovascular events among older people: protocol for a randomised controlled trial in primary care (STAREE trial)
Introduction: The world is undergoing a demographic transition to an older population. Preventive healthcare has reduced the burden of chronic illness at younger ages but there is limited evidence that these advances can improve health at older ages. Statins are one class of drug with the potential to prevent or delay the onset of several causes of incapacity in older age, particularly major cardiovascular disease (CVD). This paper presents the protocol for the STAtins in Reducing Events in the Elderly (STAREE) trial, a randomised double-blind placebo-controlled trial examining the effects of statins in community dwelling older people without CVD, diabetes or dementia. Methods and analysis: We will conduct a double-blind, randomised placebo-controlled trial among people aged 70 years and over, recruited through Australian general practice and with no history of clinical CVD, diabetes or dementia. Participants will be randomly assigned to oral atorvastatin (40 mg daily) or matching placebo (1:1 ratio). The co-primary endpoints are disability-free survival defined as survival-free of dementia and persistent physical disability, and major cardiovascular events (cardiovascular death or non-fatal myocardial infarction or stroke). Secondary endpoints are all-cause death, dementia and other cognitive decline, persistent physical disability, fatal and non-fatal myocardial infarction, fatal and non-fatal stroke, heart failure, atrial fibrillation, fatal and non-fatal cancer, all-cause hospitalisation, need for permanent residential care and quality of life. Comparisons between assigned treatment arms will be on an intention-to-treat basis with each of the co-primary endpoints analysed separately in time-to-first-event analyses using Cox proportional hazards regression models. Ethics and dissemination: STAREE will address uncertainties about the preventive effects of statins on a range of clinical outcomes important to older people. Institutional ethics approval has been obtained. All research outputs will be disseminated to general practitioner co-investigators and participants, published in peer-reviewed journals and presented at national and international conferences. Trial registration number: NCT02099123.Sophia Zoungas, Andrea Curtis, Simone Spark, Rory Wolfe, John J McNeil, Lawrence Beilin, Trevor T-J Chong, Geoffrey Cloud, Ingrid Hopper, Alissia Kost, Mark Nelson, Stephen J Nicholls, Christopher M Reid, Joanne Ryan, Andrew Tonkin, Stephanie A Ward, Anthony Wierzbicki, On behalf of STAREE investigator grou
Characterization of anticoagulant heparinoids by immunoprofiling
Heparinoids are used in the clinic as anticoagulants. A specific pentasaccharide in heparinoids activates antithrombin III, resulting in inactivation of factor Xa and–when additional saccharides are present–inactivation of factor IIa. Structural and functional analysis of the heterogeneous heparinoids generally requires advanced equipment, is time consuming, and needs (extensive) sample preparation. In this study, a novel and fast method for the characterization of heparinoids is introduced based on reactivity with nine unique anti-heparin antibodies. Eight heparinoids were biochemically analyzed by electrophoresis and their reactivity with domain-specific anti-heparin antibodies was established by ELISA. Each heparinoid displayed a distinct immunoprofile matching its structural characteristics. The immunoprofile could also be linked to biological characteristics, such as the anti-Xa/anti-IIa ratio, which was reflected by reactivity of the heparinoids with antibodies HS4C3 (indicative for 3-O-sulfates) and HS4E4 (indicative for domains allowing anti-factor IIa activity). In addition, the immunoprofile could be indicative for heparinoid-induced side-effects, such as heparin-induced thrombocytopenia, as illustrated by reactivity with antibody NS4F5, which defines a very high sulfated domain. In conclusion, immunoprofiling provides a novel, fast, and simple methodology for the characterization of heparinoids, and allows high-throughput screening of (new) heparinoids for defined structural and biological characteristics
Novel Druggable Hot Spots in Avian Influenza Neuraminidase H5N1 Revealed by Computational Solvent Mapping of a Reduced and Representative Receptor Ensemble
The influenza virus subtype H5N1 has raised concerns of a possible human pandemic threat because of its high virulence and mutation rate. Although several approved anti-influenza drugs effectively target the neuraminidase, some strains have already acquired resistance to the currently available anti-influenza drugs. In this study, we present the synergistic application of extended explicit solvent molecular dynamics (MD) and computational solvent mapping (CS-Map) to identify putative ‘hot spots’ within flexible binding regions of N1 neuraminidase. Using representative conformations of the N1 binding region extracted from a clustering analysis of four concatenated 40-ns MD simulations, CS-Map was utilized to assess the ability of small, solvent-sized molecules to bind within close proximity to the sialic acid binding region. Mapping analyses of the dominant MD conformations reveal the presence of additional hot spot regions in the 150- and 430-loop regions. Our hot spot analysis provides further support for the feasibility of developing high-affinity inhibitors capable of binding these regions, which appear to be unique to the N1 strain
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