579 research outputs found
Hawking Radiation as Quantum Tunneling in Rindler Coordinate
We substantiate the Hawking radiation as quantum tunneling of fields or
particles crossing the horizon by using the Rindler coordinate. The thermal
spectrum detected by an accelerated particle is interpreted as quantum
tunneling in the Rindler spacetime. Representing the spacetime near the horizon
locally as a Rindler spacetime, we find the emission rate by tunneling, which
is expressed as a contour integral and gives the correct Boltzmann factor. We
apply the method to non-extremal black holes such as a Schwarzschild black
hole, a non-extremal Reissner-Nordstr\"{o}m black hole, a charged Kerr black
hole, de Sitter space, and a Schwarzschild-anti de Sitter black hole.Comment: LaTex 19 pages, no figure; references added and replaced by the
version accepted in JHE
D-branes in T-fold conformal field theory
We investigate boundary dynamics of orbifold conformal field theory involving
T-duality twists. Such models typically appear in contexts of non-geometric
string compactifications that are called monodrofolds or T-folds in recent
literature. We use the framework of boundary conformal field theory to analyse
the models from a microscopic world-sheet perspective. In these backgrounds
there are two kinds of D-branes that are analogous to bulk and fractional
branes in standard orbifold models. The bulk D-branes in T-folds allow
intuitive geometrical interpretations and are consistent with the classical
analysis based on the doubled torus formalism. The fractional branes, on the
other hand, are `non-geometric' at any point in the moduli space and their
geometric counterparts seem to be missing in the doubled torus analysis. We
compute cylinder amplitudes between the bulk and fractional branes, and find
that the lightest modes of the open string spectra show intriguing non-linear
dependence on the moduli (location of the brane or value of the Wilson line),
suggesting that the physics of T-folds, when D-branes are involved, could
deviate from geometric backgrounds even at low energies. We also extend our
analysis to the models with SU(2) WZW fibre at arbitrary levels.Comment: 38 pages, no figure, ams packages. Essentially the published versio
Impact of Zinc Deficiency on Vibrio Cholerae Enterotoxin-stimulated Water and Electrolyte Transport in Animal Model
The effect of zinc deficiency on the function of the intestine to
absorb water and electrolytes was studied in animal models, stimulated
by Vibrio cholerae enterotoxin. Sprague-Dawley rats, used in the
study, were divided into four groups: Zinc-deficient, ad libitum
zinc-fed control, zinc weight-matched control, and zinc-deficient
acutely-repleted. 14C-labelled polyethylene glycol solution was used
for measuring the absorption capacity of the small intestine.
Significantly lower absorption of water and sodium per cm of the
intestine was observed in the zinc-deficient animals compared to the ad
libitum zinc-fed control animals (p<0.01). An improved absorption
capacity was equally observed in the zinc-deficient acutely-repleted
animals and ad libitum zinc-fed control group. The zinc-deficient
animals showed four times greater cholera toxin-induced net secretions
of water and sodium compared to the ad libitum zinc-fed group
(p<0.01), while a 40% reduction was observed in the zinc-deficient
acutely-repleted group. The results suggest that zinc deficiency is
associated with reduced absorption of water and electrolytes and
increased secretion of the same stimulated by cholera toxin
Correction: Alhamami et al. First emergence of resistance to macrolides and tetracycline identified in Mannheimia haemolytica and Pasteurella multocida isolates from beef feedlots in Australia. Microorganisms 2021, 9, 1322
The authors wish to make the following corrections to this paper..
Photo-Voltaic (PV) Monitoring System, Performance Analysis and Power Prediction Models in Doha, Qatar
This study aims developing customized novel data acquisition for photovoltaic systems under extreme climates by utilizing off-the-shelf components and enhanced with data analytics for performance evaluation and prediction. Microcontrollers and sensors are used to measure meteorological and electrical parameters. Customized signal conditioning, which can withstand high-temperature along with microcontrollers’ development boards enhanced with appropriate interfacing shields and wireless data transmission to iCloud IoT platforms, is developed. In addition, an automatically controllable in-house electronic load of the PV system was developed to measure the maximum power possible from the system. LabVIEW™ program was used to allow ubiquitous access and processing of the recorded data over the used IoT. Furthermore, machine learning algorithms are utilized to predict the PV output power by utilizing data collected over a two-year span. The result of this study is the commissioning of original hardware for PV study under extreme climates. This study also shows how the use of specific ML algorithms such as Artificial Neural Network (ANN) can successfully provide accurate predictions with low root-mean-squared error (RMSE) between the predicted and actual power. The results support reliable integration of PV systems into smart-grids for efficient energy planning and management, especially for arid and semi-arid regions
Hawking Radiation and Tunneling Mechanism for a New Class of Black Holes in Einstein-Gauss-Bonnet Gravity
We study the Hawking radiation in a new class of black hole solutions in the
Einstein-Gauss-Bonnet theory. The black hole has been argued to have vanishing
mass and entropy, but finite Hawking temperature. To check if it really emits
radiation, we analyse the Hawking radiation using the original method of
quantization of scalar field in the black hole background and the quantum
tunneling method, and confirm that it emits radiation at the Hawking
temperature. A general formula is derived for the Hawking temperature and
backreaction in the tunneling approach. Physical implications of these results
are discussed.Comment: 12 pages, v2: Title slightly changed. Motivation and discussions are
elaborated, v3: typos corrected to match the published versio
Mirrorfolds with K3 Fibrations
We study a class of non-geometric string vacua realized as completely soluble
superconformal field theory (SCFT). These models are defined as `interpolating
orbifolds' of by the mirror transformation acting on the
fiber combined with the half-shift on the -base. They are variants of the
T-folds, the interpolating orbifolds by T-duality transformations, and thus may
be called `mirrorfolds'. Starting with arbitrary (compact or non-compact)
Gepner models for the fiber, we construct modular invariant partition
functions of general mirrorfold models. In the case of compact fiber the
mirrorfolds only yield non-supersymmetric string vacua. They exhibit IR
instability due to winding tachyon condensation which is similar to the
Scherk-Schwarz type circle compactification. When the fiber SCFT is non-compact
(say, the ALE space in the simplest case), on the other hand, both
supersymmetric and non-supersymmetric vacua can be constructed. The non-compact
non-supersymmetric mirrorfolds can get stabilised at the level of string
perturbation theory. We also find that in the non-compact supersymmeric
mirrorfolds D-branes are {\em always} non-BPS. These D-branes can get
stabilized against both open- and closed-string marginal deformations.Comment: Eqns (2.61) and (3.17) correcte
Global, regional, and national comparative risk assessment of 79 behavioural, environmental and occupational, and metabolic risks or clusters of risks, 1990-2015: A systematic analysis for the Global Burden of Disease Study 2015
Background: The Global Burden of Diseases, Injuries, and Risk Factors Study 2015 provides an up-to-date synthesis of the evidence for risk factor exposure and the attributable burden of disease. By providing national and subnational assessments spanning the past 25 years, this study can inform debates on the importance of addressing risks in context.
Methods: We used the comparative risk assessment framework developed for previous iterations of the Global Burden of Disease Study to estimate attributable deaths, disability-adjusted life-years (DALYs), and trends in exposure by age group, sex, year, and geography for 79 behavioural, environmental and occupational, and metabolic risks or clusters of risks from 1990 to 2015. This study included 388 risk-outcome pairs that met World Cancer Research Fund-defined criteria for convincing or probable evidence. We extracted relative risk and exposure estimates from randomised controlled trials, cohorts, pooled cohorts, household surveys, census data, satellite data, and other sources. We used statistical models to pool data, adjust for bias, and incorporate covariates. We developed a metric that allows comparisons of exposure across risk factors—the summary exposure value. Using the counterfactual scenario of theoretical minimum risk level, we estimated the portion of deaths and DALYs that could be attributed to a given risk. We decomposed trends in attributable burden into contributions from population growth, population age structure, risk exposure, and risk-deleted cause-specific DALY rates. We characterised risk exposure in relation to a Socio-demographic Index (SDI).
Findings: Between 1990 and 2015, global exposure to unsafe sanitation, household air pollution, childhood underweight, childhood stunting, and smoking each decreased by more than 25%. Global exposure for several occupational risks, high body-mass index (BMI), and drug use increased by more than 25% over the same period. All risks jointly evaluated in 2015 accounted for 57·8% (95% CI 56·6–58·8) of global deaths and 41·2% (39·8–42·8) of DALYs. In 2015, the ten largest contributors to global DALYs among Level 3 risks were high systolic blood pressure (211·8 million [192·7 million to 231·1 million] global DALYs), smoking (148·6 million [134·2 million to 163·1 million]), high fasting plasma glucose (143·1 million [125·1 million to 163·5 million]), high BMI (120·1 million [83·8 million to 158·4 million]), childhood undernutrition (113·3 million [103·9 million to 123·4 million]), ambient particulate matter (103·1 million [90·8 million to 115·1 million]), high total cholesterol (88·7 million [74·6 million to 105·7 million]), household air pollution (85·6 million [66·7 million to 106·1 million]), alcohol use (85·0 million [77·2 million to 93·0 million]), and diets high in sodium (83·0 million [49·3 million to 127·5 million]). From 1990 to 2015, attributable DALYs declined for micronutrient deficiencies, childhood undernutrition, unsafe sanitation and water, and household air pollution; reductions in risk-deleted DALY rates rather than reductions in exposure drove these declines. Rising exposure contributed to notable increases in attributable DALYs from high BMI, high fasting plasma glucose, occupational carcinogens, and drug use. Environmental risks and childhood undernutrition declined steadily with SDI; low physical activity, high BMI, and high fasting plasma glucose increased with SDI. In 119 countries, metabolic risks, such as high BMI and fasting plasma glucose, contributed the most attributable DALYs in 2015. Regionally, smoking still ranked among the leading five risk factors for attributable DALYs in 109 countries; childhood underweight and unsafe sex remained primary drivers of early death and disability in much of sub-Saharan Africa.
Interpretation: Declines in some key environmental risks have contributed to declines in critical infectious diseases. Some risks appear to be invariant to SDI. Increasing risks, including high BMI, high fasting plasma glucose, drug use, and some occupational exposures, contribute to rising burden from some conditions, but also provide opportunities for intervention. Some highly preventable risks, such as smoking, remain major causes of attributable DALYs, even as exposure is declining. Public policy makers need to pay attention to the risks that are increasingly major contributors to global burden.
Funding: Bill & Melinda Gates Foundation
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