121 research outputs found
A first-principles comparison of the electronic properties of MgC_{y}Ni_{3} and ZnC_{y}Ni_{3} alloys
First-principles, density-functional-based electronic structure calculations
are employed to study the changes in the electronic properties of ZnC_{y}Ni_{3}
and MgC_{y}Ni_{3} using the Korringa-Kohn-Rostoker coherent-potential
approximation method in the atomic sphere approximation (KKR-ASA CPA). As a
function of decreasing C at%, we find a steady decrease in the lattice constant
and bulk modulus in either alloys. However, the pressure derivative of the bulk
modulus displays an opposite trend. Following the Debye model, which relates
the pressure derivative of the bulk modulus with the average phonon frequency
of the crystal, it can thus be argued that ZnCNi_{3} and its disordered alloys
posses a different phonon spectra in comparison to its MgCNi_{3} counterparts.
This is further justified by the marked similarity we find in the electronic
structure properties such as the variation in the density of states and the
Hopfield parameters calculated for these alloys. The effects on the equation of
state parameters and the density of states at the Fermi energy, for partial
replacement of Mg by Zn are also discussed.Comment: 19 pages, 15 figure
Prevalence and determinants of substance use among indigenous tribes in South India: Findings from a tribal household survey
Background: Indigenous populations have higher substance use than non-indigenous populations. Current evidence on indigenous substance use is largely derived from national household surveys, while there are no specifically designed, culturally specific methodological studies available to determine the prevalence of substance abuse among the indigenous tribes. The present study examined the prevalence and predictors of alcohol use, smoking, and betel quid chewing among indigenous tribes in South India. Method: We conducted a cross-sectional population-based random survey of 2186 tribal households in the Wayanad District, Kerala. A self-prepared, pilot-tested structured interview schedule was used to collect information on sociodemographic variables and substance use. Multivariate logistic regression models were used to examine the sociodemographic predictors of substance use. Results: The overall prevalence of current alcohol use, current smoking and daily betel quid use was 17.2%, 18.8% and 47.6% respectively. Consistently, male gender (alcohol use OR = 13.55; smoking OR = 3.42; betel quid use OR = 1.65), increasing age (OR = 1.32; OR = 1.01; OR = 1.03), Paniya tribe status (OR = 2.24; OR = 1.39; OR = 5.38) and employment status being working (OR = 2.07; OR = 1.77; OR = 1.26) increased the risk of alcohol use, smoking and betel quid chewing. Furthermore, having ‘no formal education’ was associated with smoking (OR = 1.35), and betel quid chewing (OR = 3.27). Conclusion: Substance use was high among the indigenous tribes. The male gender, increasing age, Paniya tribe and working status significantly influenced alcohol use, smoking and betel quid chewing. The results underscore the need for indigenous specific de-addiction policies and programmes, alongside a consideration of the critical sociodemographic predictors
Effective AdS/renormalized CFT
For an effective AdS theory, we present a simple prescription to compute the
renormalization of its dual boundary field theory. In particular, we define
anomalous dimension holographically as the dependence of the wave-function
renormalization factor on the radial cutoff in the Poincare patch of AdS. With
this definition, the anomalous dimensions of both single- and double- trace
operators are calculated. Three different dualities are considered with the
field theory being CFT, CFT with a double-trace deformation and spontaneously
broken CFT. For the second dual pair, we compute scaling corrections at the UV
and IR fixed points of the RG flow triggered by the double-trace deformation.
For the last case, we discuss whether our prescription is sensitive to the AdS
interior or equivalently, the IR physics of the dual field theory.Comment: 20 pages, 3 figure
Fluorescence characterization of clinically-important bacteria
Healthcare-associated infections (HCAI/HAI) represent a substantial threat to patient health during hospitalization and incur billions of dollars additional cost for subsequent treatment. One promising method for the detection of bacterial contamination in a clinical setting before an HAI outbreak occurs is to exploit native fluorescence of cellular molecules for a hand-held, rapid-sweep surveillance instrument. Previous studies have shown fluorescence-based detection to be sensitive and effective for food-borne and environmental microorganisms, and even to be able to distinguish between cell types, but this powerful technique has not yet been deployed on the macroscale for the primary surveillance of contamination in healthcare facilities to prevent HAI. Here we report experimental data for the specification and design of such a fluorescence-based detection instrument. We have characterized the complete fluorescence response of eleven clinically-relevant bacteria by generating excitation-emission matrices (EEMs) over broad wavelength ranges. Furthermore, a number of surfaces and items of equipment commonly present on a ward, and potentially responsible for pathogen transfer, have been analyzed for potential issues of background fluorescence masking the signal from contaminant bacteria. These include bedside handrails, nurse call button, blood pressure cuff and ward computer keyboard, as well as disinfectant cleaning products and microfiber cloth. All examined bacterial strains exhibited a distinctive double-peak fluorescence feature associated with tryptophan with no other cellular fluorophore detected. Thus, this fluorescence survey found that an emission peak of 340nm, from an excitation source at 280nm, was the cellular fluorescence signal to target for detection of bacterial contamination. The majority of materials analysed offer a spectral window through which bacterial contamination could indeed be detected. A few instances were found of potential problems of background fluorescence masking that of bacteria, but in the case of the microfiber cleaning cloth, imaging techniques could morphologically distinguish between stray strands and bacterial contamination
A Stealth Supersymmetry Sampler
The LHC has strongly constrained models of supersymmetry with traditional
missing energy signatures. We present a variety of models that realize the
concept of Stealth Supersymmetry, i.e. models with R-parity in which one or
more nearly-supersymmetric particles (a "stealth sector") lead to collider
signatures with only a small amount of missing energy. The simplest realization
involves low-scale supersymmetry breaking, with an R-odd particle decaying to
its superpartner and a soft gravitino. We clarify the stealth mechanism and its
differences from compressed supersymmetry and explain the requirements for
stealth models with high-scale supersymmetry breaking, in which the soft
invisible particle is not a gravitino. We also discuss new and distinctive
classes of stealth models that couple through a baryon portal or Z' gauge
interactions. Finally, we present updated limits on stealth supersymmetry in
light of current LHC searches.Comment: 45 pages, 16 figure
2:1 for Naturalness at the LHC?
A large enhancement of a factor of 1.5 - 2 in Higgs production and decay in
the diphoton channel, with little deviation in the ZZ channel, can only
plausibly arise from a loop of new charged particles with large couplings to
the Higgs. We show that, allowing only new fermions with marginal interactions
at the weak scale, the required Yukawa couplings for a factor of 2 enhancement
are so large that the Higgs quartic coupling is pushed to large negative values
in the UV, triggering an unacceptable vacuum instability far beneath the 10 TeV
scale. An enhancement by a factor of 1.5 can be accommodated if the charged
fermions are lighter than 150 GeV, within reach of discovery in almost all
cases in the 8 TeV run at the LHC, and in even the most difficult cases at 14
TeV. Thus if the diphoton enhancement survives further scrutiny, and no charged
fermions beneath 150 GeV are found, there must be new bosons far beneath the 10
TeV scale. This would unambiguously rule out a large class of fine-tuned
theories for physics beyond the Standard Model, including split SUSY and many
of its variants, and provide strong circumstantial evidence for a natural
theory of electroweak symmetry breaking at the TeV scale. Alternately, theories
with only a single fine-tuned Higgs and new fermions at the weak scale, with no
additional scalars or gauge bosons up to a cutoff much larger than the 10 TeV
scale, unambiguously predict that the hints for a large diphoton enhancement in
the current data will disappear.Comment: 18 pages, 6 figures; typos corrected and references adde
Single Molecule In Vivo Analysis of Toll-Like Receptor 9 and CpG DNA Interaction
Toll-like receptor 9 (TLR9) activates the innate immune system in response to oligonucleotides rich in CpG whereas DNA lacking CpG could inhibit its activation. However, the mechanism of how TLR9 interacts with nucleic acid and becomes activated in live cells is not well understood. Here, we report on the successful implementation of single molecule tools, constituting fluorescence correlation/cross-correlation spectroscopy (FCS and FCCS) and photon count histogram (PCH) with fluorescence lifetime imaging (FLIM) to study the interaction of TLR9-GFP with Cy5 labeled oligonucleotide containing CpG or lacking CpG in live HEK 293 cells. Our findings show that i) TLR9 predominantly forms homodimers (80%) before binding to a ligand and further addition of CpG or non CpG DNA does not necessarily increase the proportion of TLR9 dimers, ii) CpG DNA has a lower dissociation constant (62 nM±9 nM) compared to non CpG DNA (153 nM±26 nM) upon binding to TLR9, suggesting that a motif specific binding affinity of TLR9 could be an important factor in instituting a conformational change-dependant activation, and iii) both CpG and non CpG DNA binds to TLR9 with a 1∶2 stoichiometry in vivo. Collectively, through our findings we establish an in vivo model of TLR9 binding and activation by CpG DNA using single molecule fluorescence techniques for single cell studies
Price shocks in regional markets: Japan's great Kantō Earthquake of 1923
Japan’s Great Kantō Earthquake of September 1st 1923 devastated the area around Tokyo and the country’s main port of Yokohama. This paper uses the earthquake as a case study to inform our understanding of the economics of disasters and the history of market integration. It seeks to test two main assumptions: firstly, that shifting demand and supply curves consequent on a disaster will have some impact on prices; and secondly, that any local changes in the disaster region are likely to be diffused across a wider geographical area. We make use of a unique monthly wholesale price dataset for a number of cities across Japan, and our analysis suggests three main findings: that price changes in the affected areas immediately following the disaster were in most cases reflected in price changes in Japan’s provincial cities; that cities further away from the devastation witnessed smaller price changes than those nearer to the affected area; and that the observed pattern of price changes reflects the regional heterogeneity identified by scholars who have worked on market integration in Japan
Natural SUSY Predicts: Higgs Couplings
We study Higgs production and decays in the context of natural SUSY, allowing
for an extended Higgs sector to account for a 125 GeV lightest Higgs boson.
Under broad assumptions, Higgs observables at the LHC depend on at most four
free parameters with restricted numerical ranges. Two parameters suffice to
describe MSSM particle loops. The MSSM loop contribution to the diphoton rate
is constrained from above by direct stop and chargino searches and by
electroweak precision tests. Naturalness, in particular in demanding that rare
B decays remain consistent with experiment without fine-tuned cancellations,
provides a lower (upper) bound to the stop contribution to the Higgs-gluon
coupling (Higgs mass). Two parameters suffice to describe Higgs mixing, even in
the presence of loop induced non-holomorphic Yukawa couplings. Generic classes
of MSSM extensions, that address the fine-tuning problem, predict sizable
modifications to the effective bottom Yukawa, yb. Non-decoupling gauge
extensions enhance yb, while a heavy SM singlet reduces yb. A factor of 4-6
enhancement in the diphoton rate at the LHC, compared to the SM prediction, can
be accommodated. The ratio of the enhancements in the diphoton vs. the WW and
ZZ channels cannot exceed 1.4. The h to bbbar rate in associated production
cannot exceed the SM rate by more than 50%.Comment: 31 pages, 11 figure
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