4,682 research outputs found
Bayesian salamanders: analysing the demography of an underground population of the European plethodontid <i>Speleomantes strinatii</i> with state-space modelling
<b>Background</b>: It has been suggested that Plethodontid salamanders are excellent candidates for indicating ecosystem health. However, detailed, long-term data sets of their populations are rare, limiting our understanding of the demographic processes underlying their population fluctuations. Here we present a demographic analysis based on a 1996 - 2008 data set on an underground population of Speleomantes strinatii (Aellen) in NW Italy. We utilised a Bayesian state-space approach allowing us to parameterise a stage-structured Lefkovitch model. We used all the available population data from annual temporary removal experiments to provide us with the baseline data on the numbers of juveniles, subadults and adult males and females present at any given time.
<b>Results</b>: Sampling the posterior chains of the converged state-space model gives us the likelihood distributions of the state-specific demographic rates and the associated uncertainty of these estimates. Analysing the resulting parameterised Lefkovitch matrices shows that the population growth is very close to 1, and that at population equilibrium we expect half of the individuals present to be adults of reproductive age which is what we also observe in the data. Elasticity analysis shows that adult survival is the key determinant for population growth.
<b>Conclusion</b>: This analysis demonstrates how an understanding of population demography can be gained from structured population data even in a case where following marked individuals over their whole lifespan is not practical
The deformed M2-brane
The superembedding formalism is used to study correction terms to the
dynamics of the M2 brane in a flat background. This is done by deforming the
standard embedding constraint. It is shown rigorously that the first such
correction occurs at dimension four. Cohomological techniques are used to
determine this correction explicitly. The action is derived to quadratic order
in fermions, and the modified \k-symmetry transformations are given.Comment: 38 pages, 3 figure
Ownership Change, Productivity, and Human Capital: New Evidence from Matched Employer-Employee Data in Swedish Manufacturing
Empirical studies of the impact of changes in ownership of manufacturing plants on productivity (e.g., Lichtenberg and Siegel (1987, 1990a, 1990b), McGuckin and Nguyen (1995, 2001), and Maksimovic and Phillips (2001)) have provided limited evidence on how such transactions affect investment in human capital and have been based strictly on U.S. and U.K. data. We attempt to fill these gaps, based on an analysis of matched employer-employee data from over 19,000 Swedish manufacturing plants for the years 1985-1998. The sample covers virtually the entire population of manufacturing plants with 20 or more employees and a probability-based sample of smaller plants. We assess whether there are differential effects on productivity and human capital for different types of ownership changes, such as partial and full acquisitions and divestitures, and related and unrelated acquisitions. Our results suggest that ownership change results in an increase in relative productivity. We also find that plants involved in these transactions experience increases in average employee age, experience, and the percentage of employees with a college education. Ownership change also leads to an increase in wages and a reduction in the percentage of female workers. All of these patterns emerge most strongly for full acquisitions and divestitures and unrelated acquisitions.
Study of thermal insulation for airborne liquid hydrogen fuel tanks
A concept for a fail-safe thermal protection system was developed. From screening tests, approximately 30 foams, adhesives, and reinforcing fibers using 0.3-meter square liquid nitrogen cold plate, CPR 452 and Stafoam AA1602, both reinforced with 10 percent by weight of 1/16 inch milled OCF Style 701 Fiberglas, were selected for further tests. Cyclic tests with these materials in 2-inch thicknesses bonded on a 0.6-meter square cold plate with Crest 7410 adhesive systems, were successful. Zero permeability gas barriers were identified and found to be compatible with the insulating concept
Geochemistry of HASP, VLT, and other glasses from double drive tube 79001/2
The Apollo 17 double drive tube 79001/2 (station 9, Van Serg Crater) is distinctive because of its extreme maturity, abundance, and variety of glass clasts. It contains mare glasses of both high Ti and very low Ti (VLT) compositions, and highland glasses of all compositions common in lunar regolith samples: highland basalt (feldspathic; Al2O3 greater than 23 wt percent), KREEP (Al2O3 less than 23 wt percent, K2O greater than 0.25 wt percent), and low-K Fra Mauro (LKFM; Al2O3 less than 23 wt percent, K2O less than 0.25 wt percent). It also contains rare specimens of high-alumina, silica-poor (HASP), and ultra Mg glasses. HASP glasses contain insufficient SiO2 to permit the calculation of a standard norm, and are thought to be the product of volatilization during impact melting. They have been studied by electron microprobe major-element analysis techniques but have not previously been analyzed for trace elements. The samples analyzed for this study were polished grain mounts of the 90-160 micron fraction of four sieved samples from the 79001/2 core (depth range 2.3-11.5 cm). A total of 80 glasses were analyzed by SEM/EDS and electron microprobe, and a subset of 33 of the glasses, representing a wide range of compositional types, was chosen for high-sensitivity INAA. A microdrilling device removed disks (mostly 50-100 micron diameter, weighing approx. 0.1-0.5 micro-g) for INAA. Preliminary data reported here are based only on short counts done within two weeks of irradiation
Magnetic field tuning of coplanar waveguide resonators
We describe measurements on microwave coplanar resonators designed for
quantum bit experiments. Resonators have been patterned onto sapphire and
silicon substrates, and quality factors in excess of a million have been
observed. The resonant frequency shows a high sensitivity to magnetic field
applied perpendicular to the plane of the film, with a quadratic dependence for
the fundamental, second and third harmonics. Frequency shift of hundreds of
linewidths can be obtained.Comment: Accepted for publication in AP
On the properties of superconducting planar resonators at mK temperatures
Planar superconducting resonators are now being increasingly used at mK
temperatures in a number of novel applications. They are also interesting
devices in their own right since they allow us to probe the properties of both
the superconductor and its environment. We have experimentally investigated
three types of niobium resonators - including a lumped element design -
fabricated on sapphire and SiO_2/Si substrates. They all exhibit a non-trivial
temperature dependence of their centre frequency and quality factor. Our
results shed new light on the interaction between the electromagnetic waves in
the resonator and two-level fluctuators in the substrate.Comment: V2 includes some minor corrections/changes. Submitted to PR
Vertical Motion in the SYNOP Central Array
As part of the SYNOP (Synoptic Ocean Prediction experiment) field program, twelve tall moorings measured the Gulf Stream\u27s temperature and velocity fields with current meters (CM) at nominal depths of 400 m, 700 m, 1000 m, and 3500 m for two years, from May 1988 through August 1990. Simultaneously, 24 inverted echo sounders (IES) monitored the thermocline topography. A third observational component of the experiment was the release of isopycnal RAFOS floats; 70 such floats traversed the area monitored by the CM and the IES. This report documents the methods used to compute vertical motion for each data source, and the differences and similarities between the three methods. Typical velocities during `strong\u27 events, as observed by or inferred from all three instruments, was 1-2 mm s-1 in regions near the center of the Gulf Stream. The comparison of RAFOS vertical motions and vertical motions diagnosed from CM data showed excellent agreement; furthermore, CM vertical motions and IES vertical motions are statistically coherent for periods longer than 12 days. We conclude that we may map mesoscale fields of w(x, y, t); the fields mapped are consistent with quasi-geostrophic dynamics
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