Constraint violation stabilization using gradient feedback in constrained dynamics simulation

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76126/1/AIAA-11410-903.pd

Local free-fall temperature of a RN-AdS black hole

We use the global embedding Minkowski space (GEMS) geometries of a (3+1)-dimensional curved Reissner-Nordstr\"om(RN)-AdS black hole spacetime into a (5+2)-dimensional flat spacetime to define a proper local temperature, which remains finite at the event horizon, for freely falling observers outside a static black hole. Our extended results include the known limiting cases of the RN, Schwarzschild--AdS, and Schwarzschild black holes.Comment: 18 pages, 11 figures, version to appear in Int. J. Mod. Phys.

Seasonal abundance of small cladocerans in Lake Mangakaware, Waikato, New Zealand

The seasonal changes in the dynamics and life histories of the Cladocera in Lake Mangakaware, North Island, New Zealand, were studied over 19 months by sampling at weekly or 2-weekly intervals. Lake Mangakaware is a 13.3 ha polymictic lake with high nutrient status, low Secchi disc transparencies, and an unstable thermal regime. The four planktonic cladoceran species (Bosmina longirostris, B. meridionalis, Ceriodaphnia pulchella, and C. dubia) exhibited disjunct population maxima. Only B. longirostris was perennially present. All species exhibited low fecundities and low lipid content, indicating that food resources were limited and that competitive interactions and resistance to starvation were probably important in determining species success. Increases in body size in cooler seasons were unrelated to clutch size, giving further support for the view that available food was limited. These results are consistent with previous experimental findings that subtle differences in life history can determine seasonal success and the outcome of competition between similar species

Boosting the petrochronology arsenal: REE partitioning between garnet and monazite in Bhutanese pelitic metasediments

Metamorphic studies are increasingly striving to integrate timing information with petrographic analysis and thermobarometry – the developing field of petrochronology. Recent advances in analytical techniques, in particular a variety of in situ methods that can potentially extract the information preserved in disequilibrium features, have reinvigorated metamorphic studies. The strength of petrochronology lies in linking the isotopic age directly to the metamorphic stage, in contrast to earlier studies where accessory phase ages existed in isolation from the thermobaromatric data with which they were tentatively linked. Garnet has proved itself an invaluable tool in metamorphic studies, yielding microstructural, thermobarometric, geochemical and even geochronological information. Although common in amphibolite-facies pelitic metasediments, garnet does not easily yield its chronological data, so the common accessory phase monazite has been used more routinely. Typically, monazite isotopic ages cannot be linked to the development of different metamorphic assemblages because their textural relationships, especially with fabric-forming phases, are commonly obscure. However, their distribution as matrix grains versus inclusions in porphyroblast minerals such as garnet, or in retrograde textures, can yield useful information. In situ investigations of chemical zoning in both monazite and garnet offer the potential to link crystallisation of the two minerals more closely. Since both monazite and garnet incorporate rare earth elements (REE), their equilibrium partitioning behaviour provides not only a useful test of equilibration, but also a way of linking time to temperature. Previously reported garnetmonazite partitioning data record the behaviour expected under granulite-facies (>750°C) conditions. We document REE concentration data from sub-solidus amphibolite-facies (~650-700°C) rocks from the eastern Himalaya (Bhutan), where age and inclusion relationships suggest that garnet and monazite grew simultaneously. The garnet/monazite ratios show steeper heavy REE patterns than those reported from the higher-temperature experimental data. These data suggest either that the partitioning relationships vary with temperature, or that different relationships hold in sub-solidus vs. supra-solidus rocks. Bhutan is an excellent location to test these relationships; abundant pelitic metasediments within a single tectonic unit span metamorphic grades ranging from sub-solidus to supra-solidus. Moreover, these metamorphic rocks (and their counterparts along the strike of the orogen) have been extensively studied in recent years both in terms of their metamorphism and their monazite geochronology, providing an ideal framework for petrochronological research with applications to all major orogens

The Active Traveling Wave in the Cochlea

A sound stimulus entering the inner ear excites a deformation of the basilar membrane which travels along the cochlea towards the apex. It is well established that this wave-like disturbance is amplified by an active system. Recently, it has been proposed that the active system consists of a set of self-tuned critical oscillators which automatically operate at an oscillatory instability. Here, we show how the concepts of a traveling wave and of self-tuned critical oscillators can be combined to describe the nonlinear wave in the cochlea.Comment: 5 pages, 2 figure

Colligative properties of solutions: I. Fixed concentrations

Using the formalism of rigorous statistical mechanics, we study the phenomena of phase separation and freezing-point depression upon freezing of solutions. Specifically, we devise an Ising-based model of a solvent-solute system and show that, in the ensemble with a fixed amount of solute, a macroscopic phase separation occurs in an interval of values of the chemical potential of the solvent. The boundaries of the phase separation domain in the phase diagram are characterized and shown to asymptotically agree with the formulas used in heuristic analyses of freezing point depression. The limit of infinitesimal concentrations is described in a subsequent paper.Comment: 28 pages, 1 fig; see also math-ph/0407035 (both to appear in JSP

Density expansion for transport coefficients: Long-wavelength versus Fermi surface nonanalyticities

The expansion of the conductivity in 2-d quantum Lorentz models in terms of the scatterer density n is considered. We show that nonanalyticities in the density expansion due to scattering processes with small and large momentum transfers, respectively, have different functional forms. Some of the latter are not logarithmic, but rather of power-law nature, in sharp contrast to the 3-d case. In a 2-d model with point-like scatterers we find that the leading nonanalytic correction to the Boltzmann conductivity, apart from the frequency dependent weak-localization term, is of order n^{3/2}.Comment: 4 pp., REVTeX, epsf, 3 eps figs, final version as publishe

Carotid atherosclerosis and a reduced likelihood for lowered cognitive Performance in a Canadian first nations population

Background: We investigated the associations among cardiovascular risk factors, carotid atherosclerosis and cognitive function in a Canadian First Nations population. Methods: Individuals aged ≥18 years, without stroke, nonpreg- nant and with First Nations status were assessed by the Trail Making Test Parts A and B. Results were combined into a Trail Making Test executive function score (TMT-exec). Doppler ultrasonography assessed carotid stenosis and plaque volume. Anthropometric, vascular and metabolic risk factors were assessed by interview, clinical examinations and blood tests. Results: For 190 individuals with TMT-exec scores, the median age of the population was 39 years. Compared to the reference group, individuals with elevated levels of left carotid stenosis (LCS) and total carotid stenosis (TCS) were less likely to demonstrate lowered cognitive performance [LCS, odds ratio (OR): 0.47, 95% confidence interval (CI): 0.24-0.96; TCS, OR: 0.40, 95% CI: 0.20-0.80]. No effect was shown for plaque volume. In structural equation modeling, we found that for every 1-unit change in the anthropometric factor in kg/m2, there was a 0.86-fold decrease in the percent of TCS (p \u3c 0.05). Conclusions: Individuals with elevated levels of LCS and TCS were less likely to demonstrate lowered performance. There was some suggestion that TCS mediates the effect of anthropometric risk factors on cognitive function. Copyright © 2009 S. Karger AG, Basel

M\"ossbauer Antineutrinos: Recoilless Resonant Emission and Absorption of Electron Antineutrinos

Basic questions concerning phononless resonant capture of monoenergetic electron antineutrinos (M\"ossbauer antineutrinos) emitted in bound-state beta-decay in the 3H - 3He system are discussed. It is shown that lattice expansion and contraction after the transformation of the nucleus will drastically reduce the probability of phononless transitions and that various solid-state effects will cause large line broadening. As a possible alternative, the rare-earth system 163Ho - 163Dy is favoured. M\"ossbauer-antineutrino experiments could be used to gain new and deep insights into several basic problems in neutrino physics