38,534 research outputs found
Simulation-based Estimation of Mean and Standard Deviation for Meta-analysis via Approximate Bayesian Computation (ABC)
Background: When conducting a meta-analysis of a continuous outcome,
estimated means and standard deviations from the selected studies are required
in order to obtain an overall estimate of the mean effect and its confidence
interval. If these quantities are not directly reported in the publications,
they need to must be estimated from other reported summary statistics, such as
the median, the minimum, the maximum, and quartiles. Methods: We propose a
simulation-based estimation approach using the Approximate Bayesian Computation
(ABC) technique for estimating mean and standard deviation based on various
sets of summary statistics found in published studies. We conduct a simulation
study to compare the proposed ABC method with the existing methods of Hozo et
al. (2005), Bland (2015), and Wan et al. (2014). Results: In the estimation of
the standard deviation, our ABC method performs best in skewed or heavy-tailed
distributions. The average relative error (ARE) approaches zero as sample size
increases. In the normal distribution, our ABC performs well. However, the Wan
et al. method is best since it is based on the normal distribution assumption.
When the distribution is skewed or heavy-tailed, the ARE of Wan et al. moves
away from zero even as sample size increases. In the estimation of the mean,
our ABC method is best since the AREs converge to zero. Conclusion: ABC is a
flexible method for estimating the study-specific mean and standard deviation
for meta-analysis, especially with underlying skewed or heavy-tailed
distributions. The ABC method can be applied using other reported summary
statistics such as the posterior mean and 95% credible interval when Bayesian
analysis has been employed
Structure of the Chiral Scalar Superfield in Ten Dimensions
We describe the tensors and spinor-tensors included in the -expansion
of the ten-dimensional chiral scalar superfield. The product decompositions of
all the irreducible structures with and the tensor are
provided as a first step towards the obtention of a full tensor calculus for
the superfield.Comment: 50 pages, UCLA/94/TEP/
Microscopic two-fluid theory of rotational constants of the OCS-H complex in He droplets
We present a microscopic quantum analysis for rotational constants of the
OCS-H complex in helium droplets using the local two-fluid theory in
conjunction with path integral Monte Carlo simulations. Rotational constants
are derived from effective moments of inertia calculated assuming that motion
of the H molecule and the local non-superfluid helium density is rigidly
coupled to the molecular rotation of OCS and employing path integral methods to
sample the corresponding H and helium densities. The rigid coupling
assumption for H-OCS is calibrated by comparison with exact calculations of
the free OCS-H complex. The presence of the H molecule is found to
induce a small local non-superfluid helium density in the second solvation
shell which makes a non-negligible contribution to the moment of inertia of the
complex in helium. The resulting moments of inertia for the OCS-H complex
embedded in a cluster of 63 helium atoms are found to be in good agreement with
experimentally measured values in large helium droplets. Implications for
analysis of rotational constants of larger complexes of OCS with multiple H
molecules in helium are discussed.Comment: 11 pages, 5 figures, accepted for publication in J. Chem. Phy
Fractional ac Josephson effect in p- and d-wave superconductors
For certain orientations of Josephson junctions between two p_x-wave or two
d-wave superconductors, the subgap Andreev bound states produce a 4pi-periodic
relation between the Josephson current I and the phase difference phi: I
sin(phi/2). Consequently, the ac Josephson current has the fractional frequency
eV/h, where V is the dc voltage. In the tunneling limit, the Josephson current
is proportional to the first power (not square) of the electron tunneling
amplitude. Thus, the Josephson current between unconventional superconductors
is carried by single electrons, rather than by Cooper pairs. The fractional ac
Josephson effect can be observed experimentally by measuring frequency spectrum
of microwave radiation from the junction. We also study junctions between
singlet s-wave and triplet p_x-wave, as well as between chiral p_x + ip_y-wave
superconductors.Comment: v. 5: minor update of references in proofs; v.4: minor improvements;
v.3: major expansion to 13 pages, 6 figures; v.2: significantly expanded to 6
pages; v.1: 4 pages, 2 figures, RevTeX
Elimination of the light shift in rubidium gas cell frequency standards using pulsed optical pumping
Changes in the intensity of the light source in an optically pumped, rubidium, gas cell frequency standard can produce corresponding frequency shifts, with possible adverse effects on the long-term frequency stability. A pulsed optical pumping apparatus was constructed with the intent of investigating the frequency stability in the absence of light shifts. Contrary to original expectations, a small residual frequency shift due to changes in light intensity was experimentally observed. Evidence is given which indicates that this is not a true light-shift effect. Preliminary measurements of the frequency stability of this apparatus, with this small residual pseudo light shift present, are presented. It is shown that this pseudo light shift can be eliminated by using a more homogeneous C-field. This is consistent with the idea that the pseudo light shift is due to inhomogeneity in the physics package (position-shift effect)
Anthropologies of Unemployment: New Perspectives on Work and Its Absence
[Excerpt] Anthropologies of Unemployment offers accessible, theoretically innovative, and ethnographically rich examinations of unemployment in rural and urban regions across North and South America, Europe, Africa, and Asia. The diversity of case studies demonstrates that unemployment is a pressing global phenomenon that sheds light on the uneven consequences of free-market ideologies and policies. Economic, social, and cultural marginalization is common in the lives of the unemployed, but their experience and interpretation are shaped by local and national cultural particularities. In exploring those differences, the contributors to this volume employ recent theoretical innovations and engage with some of the more salient topics in contemporary anthropology, such as globalization, migration, youth cultures, bureaucracy, class, gender, and race.
Taken together, the chapters reveal that there is something new about unemployment today. It is not a temporary occurrence, but a chronic condition. In adjusting to persistent, longstanding unemployment, people and groups create new understandings of unemployment as well as of work and employment; they improvise new forms of sociality, morality, and personhood. Ethnographic studies such as those found in Anthropologies of Unemployment are crucial if we are to understand the broader forms, meanings, and significance of pervasive economic insecurity and discover the emergence of new social and cultural possibilities
Towards Distributed Convoy Pattern Mining
Mining movement data to reveal interesting behavioral patterns has gained
attention in recent years. One such pattern is the convoy pattern which
consists of at least m objects moving together for at least k consecutive time
instants where m and k are user-defined parameters. Existing algorithms for
detecting convoy patterns, however do not scale to real-life dataset sizes.
Therefore a distributed algorithm for convoy mining is inevitable. In this
paper, we discuss the problem of convoy mining and analyze different data
partitioning strategies to pave the way for a generic distributed convoy
pattern mining algorithm.Comment: SIGSPATIAL'15 November 03-06, 2015, Bellevue, WA, US
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