1,165 research outputs found
Broadband, unpolarized repumping and clearout light sources for Sr single-ion clocks
Future transportable optical clocks require compact and reliable light
sources. Here, broadband, unpolarized repumper and state clearout sources for
Sr+ single-ion optical clocks are reported. These turn-key devices require no
frequency stabilization nor external modulators. They are fiber based,
inexpensive, and compact. Key characteristics for clock operation are
presented, including optical spectra, induced light shifts and required
extinction ratios. Tests with an operating single-ion standard show a clearout
efficiency of 100%. Compared to a laser-based repumper, the achievable
fluorescence rates for ion detection are a few tens of per cent lower. The
resulting ion kinetic temperature is 1--1.5 mK, near the Doppler limit of the
ion system. Similar repumper light sources could be made for Ca+ (866 nm) and
Ba+ (650 nm) using semiconductor gain media.Comment: 4 pages, 6 figure
Experiments of Interfacial Roughening in Hele-Shaw Flows with Weak Quenched Disorder
We have studied the kinetic roughening of an oil--air interface in a forced
imbibition experiment in a horizontal Hele--Shaw cell with quenched disorder.
Different disorder configurations, characterized by their persistence length in
the direction of growth, have been explored by varying the average interface
velocity v and the gap spacing b. Through the analysis of the rms width as a
function of time, we have measured a growth exponent beta ~= 0.5 that is almost
independent of the experimental parameters. The analysis of the roughness
exponent alpha through the power spectrum have shown different behaviors at
short (alpha_1) and long (alpha_2) length scales, separated by a crossover
wavenumber q_c. The values of the measured roughness exponents depend on
experimental parameters, but at large velocities we obtain alpha_1 ~= 1.3
independently of the disorder configuration. The dependence of the crossover
wavenumber with the experimental parameters has also been investigated,
measuring q_c ~ v^{0.47} for the shortest persistence length, in agreement with
theoretical predictions.Comment: 20 pages, 22 figure
Propagation dynamics on networks featuring complex topologies
Analytical description of propagation phenomena on random networks has
flourished in recent years, yet more complex systems have mainly been studied
through numerical means. In this paper, a mean-field description is used to
coherently couple the dynamics of the network elements (nodes, vertices,
individuals...) on the one hand and their recurrent topological patterns
(subgraphs, groups...) on the other hand. In a SIS model of epidemic spread on
social networks with community structure, this approach yields a set of ODEs
for the time evolution of the system, as well as analytical solutions for the
epidemic threshold and equilibria. The results obtained are in good agreement
with numerical simulations and reproduce random networks behavior in the
appropriate limits which highlights the influence of topology on the processes.
Finally, it is demonstrated that our model predicts higher epidemic thresholds
for clustered structures than for equivalent random topologies in the case of
networks with zero degree correlation.Comment: 10 pages, 5 figures, 1 Appendix. Published in Phys. Rev. E (mistakes
in the PRE version are corrected here
Best Practices in the U.S. Lodging Industry: Overview, Methods, and Champions
When a lodging operation is doing an innovative and excellent job in a particular area, the industry benefits from spreading the word about the practice. But first one has to discover those best practices
Managing for Excellence: Conclusions and Challenges from a Study of Best Practices in the U.S Lodging Industry
Perhaps the real challenge of innovation is to continue innovating
Recommended from our members
Erratum: Interleukin-1β contributes to the generation of experimental febrile seizures (Annals of Neurology (January 2005) 57 (152-155))
Interface Equations for Capillary Rise in Random Environment
We consider the influence of quenched noise upon interface dynamics in 2D and
3D capillary rise with rough walls by using phase-field approach, where the
local conservation of mass in the bulk is explicitly included. In the 2D case
the disorder is assumed to be in the effective mobility coefficient, while in
the 3D case we explicitly consider the influence of locally fluctuating
geometry along a solid wall using a generalized curvilinear coordinate
transformation. To obtain the equations of motion for meniscus and contact
lines, we develop a systematic projection formalism which allows inclusion of
disorder. Using this formalism, we derive linearized equations of motion for
the meniscus and contact line variables, which become local in the Fourier
space representation. These dispersion relations contain effective noise that
is linearly proportional to the velocity. The deterministic parts of our
dispersion relations agree with results obtained from other similar studies in
the proper limits. However, the forms of the noise terms derived here are
quantitatively different from the other studies
Ethical considerations for HIV remission clinical research involving participants diagnosed during acute HIV infection
HIV remission clinical researchers are increasingly seeking study participants who are diagnosed and treated during acute HIV infection—the brief period between infection and the point when the body creates detectable HIV antibodies. This earliest stage of infection is often marked by flu-like illness and may be an especially tumultuous period of confusion, guilt, anger, and uncertainty. Such experiences may present added ethical challenges for HIV research recruitment, participation, and retention. The purpose of this paper is to identify potential ethical challenges associated with involving acutely diagnosed people living with HIV in remission research and considerations for how to mitigate them. We identify three domains of potential ethical concern for clinicians, researchers, and ethics committee members to consider: 1) Recruitment and informed consent; (2) Transmission risks and partner protection; and (3) Ancillary and continuing care. We discuss each of these domains with the aim of inspiring further work to advance the ethical conduct of HIV remission research. For example, experiences of confusion and uncertainty regarding illness and diagnosis during acute HIV infection may complicate informed consent procedures in studies that seek to recruit directly after diagnosis. To address this, it may be appropriate to use staged re-consent procedures or comprehension assessment. Responsible conduct of research requires a broad understanding of acute HIV infection that encompasses its biomedical, psychological, social, and behavioral dimensions. We argue that the lived experience of acute HIV infection may introduce ethical concerns that researchers and reviewers should address during study design and ethical approval
Evaluation of the impact of screening and signalling carriers of methicillin-resistant Staphylococcus aureus (MRSA) on hand hygiene compliance and MRSA crosstransmission
- …