9,418 research outputs found
Anti-de Sitter boundary in Poincare coordinates
We study the space-time boundary of a Poincare patch of Anti-de Sitter (AdS)
space. We map the Poincare AdS boundary to the global coordinate chart and show
why this boundary is not equivalent to the global AdS boundary. The Poincare
AdS boundary is shown to contain points of the bulk of the entire AdS space.
The Euclidean AdS space is also discussed. In this case one can define a
semi-global chart that divides the AdS space in the same way as the
corresponding Euclidean Poincare chart.Comment: In this revised version we add a discussion of the physical
consequences of the choice of a coordinate system for AdS space. We changed
figure 1 and added more references. Version to be published in Gen. Relat.
Grav
Hierarchical model for the scale-dependent velocity of seismic waves
Elastic waves of short wavelength propagating through the upper layer of the
Earth appear to move faster at large separations of source and receiver than at
short separations. This scale dependent velocity is a manifestation of Fermat's
principle of least time in a medium with random velocity fluctuations. Existing
perturbation theories predict a linear increase of the velocity shift with
increasing separation, and cannot describe the saturation of the velocity shift
at large separations that is seen in computer simulations. Here we show that
this long-standing problem in seismology can be solved using a model developed
originally in the context of polymer physics. We find that the saturation
velocity scales with the four-third power of the root-mean-square amplitude of
the velocity fluctuations, in good agreement with the computer simulations.Comment: 7 pages including 3 figure
Technical guidelines on testing the migration of primary aromatic amines from polyamide kitchenware and of formaldehyde from melamine kitchenware
Incidence of community-acquired lower respiratory tract infections and pneumonia among older adults in the United Kingdom: a population-based study.
Community-acquired lower respiratory tract infections (LRTI) and pneumonia (CAP) are common causes of morbidity and mortality among those aged ≥65 years; a growing population in many countries. Detailed incidence estimates for these infections among older adults in the United Kingdom (UK) are lacking. We used electronic general practice records from the Clinical Practice Research Data link, linked to Hospital Episode Statistics inpatient data, to estimate incidence of community-acquired LRTI and CAP among UK older adults between April 1997-March 2011, by age, sex, region and deprivation quintile. Levels of antibiotic prescribing were also assessed. LRTI incidence increased with fluctuations over time, was higher in men than women aged ≥70 and increased with age from 92.21 episodes/1000 person-years (65-69 years) to 187.91/1000 (85-89 years). CAP incidence increased more markedly with age, from 2.81 to 21.81 episodes/1000 person-years respectively, and was higher among men. For both infection groups, increases over time were attenuated after age-standardisation, indicating that these rises were largely due to population aging. Rates among those in the most deprived quintile were around 70% higher than the least deprived and were generally higher in the North of England. GP antibiotic prescribing rates were high for LRTI but lower for CAP (mostly due to immediate hospitalisation). This is the first study to provide long-term detailed incidence estimates of community-acquired LRTI and CAP in UK older individuals, taking person-time at risk into account. The summary incidence commonly presented for the ≥65 age group considerably underestimates LRTI/CAP rates, particularly among older individuals within this group. Our methodology and findings are likely to be highly relevant to health planners and researchers in other countries with aging populations
The 3-string vertex and the AdS/CFT duality in the PP-wave limit
We pursue the study of string interactions in the PP-wave background and show
that the proposal of hep-th/0211188 can be extended to a full supersymmetric
vertex. Then we compute some string amplitudes in both the bosonic and
fermionic sector, finding agreement with the field theory results at leading
order in lambda'.Comment: Latex, 25 pages. Comments added and typos correcte
Understanding How Stress Responses and Stress-Related Behaviors Have Evolved in Zebrafish and Mammals
Stress response is essential for the organism to quickly restore physiological homeostasis disturbed by various environmental insults. In addition to well-established physiological cascades, stress also evokes various brain and behavioral responses. Aquatic animal models, including the zebrafish (Danio rerio), have been extensively used to probe pathobiological mechanisms of stress and stress-related brain disorders. Here, we critically discuss the use of zebrafish models for studying mechanisms of stress and modeling its disorders experimentally, with a particular cross-taxon focus on the potential evolution of stress responses from zebrafish to rodents and humans, as well as its translational implications. © 2021 The AuthorsAVK is supported by the Zebrafish Platform Construction Fund from the Southwest University (Chongqing, China). The collaboration was supported by the Russian Science Foundation (RSF) grant 19-15-00053. KAD is supported by the President of Russia Graduate Fellowship, and the Special Rector's Fellowship for SPSU students. ACVVG is supported by the FAPERGS research fellowship 19/2551-0001-669-7. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
Frequency Locking of an Optical Cavity using LQG Integral Control
This paper considers the application of integral Linear Quadratic Gaussian
(LQG) optimal control theory to a problem of cavity locking in quantum optics.
The cavity locking problem involves controlling the error between the laser
frequency and the resonant frequency of the cavity. A model for the cavity
system, which comprises a piezo-electric actuator and an optical cavity is
experimentally determined using a subspace identification method. An LQG
controller which includes integral action is synthesized to stabilize the
frequency of the cavity to the laser frequency and to reject low frequency
noise. The controller is successfully implemented in the laboratory using a
dSpace DSP board.Comment: 18 pages, 9 figure
Quantitative measurement of the vibrational amplitude and phase in photorefractive time-average interferometry: A comparison with electronic speckle pattern interferometry
Modeling Denitrification : Can We Report What We Don't Know?
Funding Information: This study is the products of a workshop funded by the Deutsche Forschungsgemeinschaft through the research unit DFG‐FOR 2337: Denitrification in Agricultural Soils: Integrated Control and Modelling at Various Scales (DASIM), and by the German Federal Ministry of Education and Research (BMBF) under the “Make our Planet Great Again—German Research Initiative”, Grant 306060, implemented by the German Academic Exchange Service (DAAD). This work was supported by the European Union's Horizon 2020 research and innovation programme project VERIFY (grant agreement no. 776810). We would like to thank the contribution of all workshop participants of the II. DASIM Modeler Workshop. Publisher Copyright: © 2023. The Authors.Peer reviewedPublisher PD
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