2,956 research outputs found
Final Calibration of the Berkeley Extreme and Far-Ultraviolet Spectrometer on the ORFEUS-SPAS I and II Missions
The Berkeley Extreme and Far-Ultraviolet Spectrometer (BEFS) flew as part of
the ORFEUS telescope on the ORFEUS-SPAS I and II space-shuttle missions in 1993
and 1996, respectively. The data obtained by this instrument have now entered
the public domain. To facilitate their use by the astronomical community, we
have re-extracted and re-calibrated both data sets, converted them into a
standard (FITS) format, and placed them in the Multimission Archive at Space
Telescope (MAST). Our final calibration yields improved wavelength scales and
effective-area curves for both data sets.Comment: To appear in the January 2002 issue of the PASP. 17 pages with 9
embedded postscript figures; uses emulateapj5.st
Crossover from 2D to 3D in a weakly interacting Fermi gas
We have studied the transition from two to three dimensions in a low
temperature weakly interacting Li Fermi gas. Below a critical atom number,
, only the lowest transverse vibrational state of a highly anisotropic
oblate trapping potential is occupied and the gas is two-dimensional. Above
the Fermi gas enters the quasi-2D regime where shell structure
associated with the filling of individual transverse oscillator states is
apparent. This dimensional crossover is demonstrated through measurements of
the cloud size and aspect ratio versus atom number.Comment: Replaced with published manuscrip
The relationship between the optical Halpha filaments and the X-ray emission in the core of the Perseus cluster
NGC 1275 in the centre of the Perseus cluster of galaxies, Abell 426, is
surrounded by a spectacular filamentary Halpha nebula. Deep Chandra X-ray
imaging has revealed that the brighter outer filaments are also detected in
soft X-rays. This can be due to conduction and mixing of the cold gas in the
filaments with the hot, dense intracluster medium. We show the correspondence
of the filaments in both wavebands and draw attention to the relationship of
two prominent curved NW filaments to an outer, buoyant radio bubble seen as a
hole in the X-ray image. There is a strong resemblance in the shape of the hole
and the disposition of the filaments to the behaviour of a large air bubble
rising in water. If this is a correct analogy, then the flow is laminar and the
intracluster gas around this radio source is not turbulent. We obtain a limit
on the viscosity of this gas.Comment: Accepted for publication in MNRA
Effectiveness of Digital Interventions for Reducing Behavioral Risks of Cardiovascular Disease in Nonclinical Adult Populations: Systematic Review of Reviews
Background: Digital health interventions are increasingly being used as a supplement or replacement for face-to-face services as a part of predictive prevention. They may be offered to those who are at high risk of cardiovascular disease and need to improve their diet, increase physical activity, stop smoking, or reduce alcohol consumption. Despite the popularity of these interventions, there is no overall summary and comparison of the effectiveness of different modes of delivery of a digital intervention to inform policy. Objective: This review aims to summarize the effectiveness of digital interventions in improving behavioral and health outcomes related to physical activity, smoking, alcohol consumption, or diet in nonclinical adult populations and to identify the effectiveness of different modes of delivery of digital interventions. Methods: We reviewed articles published in the English language between January 1, 2009, and February 25, 2019, that presented a systematic review with a narrative synthesis or meta-analysis of any study design examining digital intervention effectiveness; data related to adults (â„18 years) in high-income countries; and data on behavioral or health outcomes related to diet, physical activity, smoking, or alcohol, alone or in any combination. Any time frame or comparator was considered eligible. We searched MEDLINE, Embase, PsycINFO, Cochrane Reviews, and gray literature. The AMSTAR-2 tool was used to assess review confidence ratings. Results: We found 92 reviews from the academic literature (47 with meta-analyses) and 2 gray literature items (1 with a meta-analysis). Digital interventions were typically more effective than no intervention, but the effect sizes were small. Evidence on the effectiveness of digital interventions compared with face-to-face interventions was mixed. Most trials reported that intent-to-treat analysis and attrition rates were often high. Studies with long follow-up periods were scarce. However, we found that digital interventions may be effective for up to 6 months after the end of the intervention but that the effects dissipated by 12 months. There were small positive effects of digital interventions on smoking cessation and alcohol reduction; possible effectiveness in combined diet and physical activity interventions; no effectiveness for interventions targeting physical activity alone, except for when interventions were delivered by mobile phone, which had medium-sized effects; and no effectiveness observed for interventions targeting diet alone. Mobile interventions were particularly effective. Internet-based interventions were generally effective. Conclusions: Digital interventions have small positive effects on smoking, alcohol consumption, and in interventions that target a combination of diet and physical activity. Small effects may have been due to the low efficacy of treatment or due to nonadherence. In addition, our ability to make inferences from the literature we reviewed was limited as those interventions were heterogeneous, many reviews had critically low AMSTAR-2 ratings, analysis was typically intent-to-treat, and follow-up times were relatively short
Identifying Motivational Factors Impacting Entrepreneurship: Evidence from an Emerging Economy
A new method for the solution of the Schrodinger equation
We present a new method for the solution of the Schrodinger equation
applicable to problems of non-perturbative nature. The method works by
identifying three different scales in the problem, which then are treated
independently: An asymptotic scale, which depends uniquely on the form of the
potential at large distances; an intermediate scale, still characterized by an
exponential decay of the wave function and, finally, a short distance scale, in
which the wave function is sizable. The key feature of our method is the
introduction of an arbitrary parameter in the last two scales, which is then
used to optimize a perturbative expansion in a suitable parameter. We apply the
method to the quantum anharmonic oscillator and find excellent results.Comment: 4 pages, 4 figures, RevTex
Generalized Master Equations for Non-Poisson Dynamics on Networks
The traditional way of studying temporal networks is to aggregate the
dynamics of the edges to create a static weighted network. This implicitly
assumes that the edges are governed by Poisson processes, which is not
typically the case in empirical temporal networks. Consequently, we examine the
effects of non-Poisson inter-event statistics on the dynamics of edges, and we
apply the concept of a generalized master equation to the study of
continuous-time random walks on networks. We show that the equation reduces to
the standard rate equations when the underlying process is Poisson and that the
stationary solution is determined by an effective transition matrix whose
leading eigenvector is easy to calculate. We discuss the implications of our
work for dynamical processes on temporal networks and for the construction of
network diagnostics that take into account their nontrivial stochastic nature
Field-effect transistors assembled from functionalized carbon nanotubes
We have fabricated field effect transistors from carbon nanotubes using a
novel selective placement scheme. We use carbon nanotubes that are covalently
bound to molecules containing hydroxamic acid functionality. The functionalized
nanotubes bind strongly to basic metal oxide surfaces, but not to silicon
dioxide. Upon annealing, the functionalization is removed, restoring the
electronic properties of the nanotubes. The devices we have fabricated show
excellent electrical characteristics.Comment: 5 pages, 6 figure
Equation level matching: An extension of the method of matched asymptotic expansion for problems of wave propagation
We introduce an alternative to the method of matched asymptotic expansions.
In the "traditional" implementation, approximate solutions, valid in different
(but overlapping) regions are matched by using "intermediate" variables. Here
we propose to match at the level of the equations involved, via a "uniform
expansion" whose equations enfold those of the approximations to be matched.
This has the advantage that one does not need to explicitly solve the
asymptotic equations to do the matching, which can be quite impossible for some
problems. In addition, it allows matching to proceed in certain wave situations
where the traditional approach fails because the time behaviors differ (e.g.,
one of the expansions does not include dissipation). On the other hand, this
approach does not provide the fairly explicit approximations resulting from
standard matching. In fact, this is not even its aim, which to produce the
"simplest" set of equations that capture the behavior
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