Opiate Drug Seeking and Addiction: The Influence of Sucrose Consumption on the Acquisition and Expression of Morphine-induced Conditioned Place Preferences (CPP)

Sucrose intake may lead to changes in brain and behavior similar to the effects of abused drugs. For example, sucrose may agonize endogenous opiate systems and modulate opiate-seeking behavior. Previous research reported equivocal outcomes where sucrose may either enhance (i.e., cross-sensitization) or attenuate (i.e., cross-tolerance) drug seeking as measured by morphine-induced CPP. The present experiment extends from past work and evaluated the impact of sucrose administered prior to place conditioning. Additionally, unique groups received sucrose prior to tests for CPP to measure sucrose influences on CPP expression. Sprague-Dawley rats (n=24) were assigned to sucrose (15% w/v) or water pre-exposure conditions. Subsequently, subjects received morphine place conditioning where morphine (10mg/kg) was administered on the initially non-preferred side of the apparatus. Three post-tests were conducted and, prior to each test, animals within each pre-exposure group (sucrose or water) received either sucrose or water. Factorial ANOVA was used to analyze data. Results showed robust morphine-induced CPP. Although animals in the sucrose pre-exposure condition displayed enhanced CPP, the outcomes were not statistically significant. The present findings support the value of CPP techniques to measure opiate drug-seeking behavior. Future work may discover the sufficient conditions for detecting sucrose cross-sensitization of morphine CPP

On the Hopf Conjecture with Symmetry

The Hopf conjecture states that an even-dimensional, positively curved Riemannian manifold has positive Euler characteristic. We prove this conjecture under the additional assumption that a torus acts by isometries and has dimension bounded from below by a logarithmic function of the manifold dimension. The main new tool is the action of the Steenrod algebra on cohomology

A preliminary estimate of the age of the Gladysvale australopithecine site

Excavations conducted at the Gladysvale site in the Transvaal, South Africa during 1991 -1992 have revealed an abundant Plio-Pleistocene fossil fauna from the limeworks breccia dumps and in situ decalcified deposits. To date, over 600 specifically identifiable macro-mammalian specimens have been recovered including the remains of Australopithecus. These identifications have revealed that the Gladysvale site has an extremely diverse macro-mammalian faunal assemblage equal to many other South African Plio-Pleistocene fossil sites. Comparison of the Gladysvale macromammalian fauna with those of the other early hominid-associated sites in South Africa indicates an age for the deposit(s) at Gladysvale between 1.7- 2.5 m.a.. ln addition, the Kromdraai A macromammalian assemblage is considered to be closer in age to the Gladysvale assemblage than any other South African faunal assemblage.John Vorster, Norman Segal, David Pfeiffe

Intracluster Short Gamma-Ray Bursts by Compact Binary Mergers

One of the possible origins of short gamma-ray bursts (SGRBs) is merging of compact binaries, and the effect of large kick velocity is a signature that can be used as an observational test for this hypothesis. Intracluster SGRBs that escaped from a host galaxy in a galaxy cluster are interesting in this context, since they would escape more easily by cluster tidal force, and would have brighter afterglow luminosity by dense intracluster gas, than those in general field galaxies. Here we calculate the escape fraction of compact binaries from their host galaxies in a galaxy cluster, and discuss some observational implications. We found that the escape fraction strongly depends on the nature of dark matter subhalos associated with member galaxies. If the amount of dark matter around member galaxies is not large and the gravitational potential for an escaping binary is determined mostly by stellar mass, most of SGRBs should escape and be observed as hostless, which is a much higher fraction than those in the field. Hence, statistics of intracluster SGRBs could give important information about the dark matter distribution in galaxy clusters, as well as hints for the origin of SGRBs.Comment: 6 pages, 1 figure, accepted to ApJ Letters; added discussion about evolution of galaxies and cluster

Halo Retention and Evolution of Coalescing Compact Binaries in Cosmological Simulations of Structure Formation: Implications for Short Gamma-Ray Bursts

Merging compact binaries are the one source of gravitational radiation so far identified. Because short-period systems which will merge in less than a Hubble time have already been observed as binary pulsars, they are important both as gravitational wave sources for observatories such as LIGO but also as progenitors for short gamma-ray bursts (SGRBs). The fact that these systems must have large systemic velocities implies that by the time they merge, they will be far from their formation site. The locations of merging sites depend sensitively on the gravitational potential of the galaxy host, which until now has been assumed to be static. Here we refine such calculations to incorporate the temporal evolution of the host's gravitational potential as well as that of its nearby neighbors using cosmological simulations of structure formation. This results in merger site distributions that are more diffusively distributed with respect to their putative hosts, with locations extending out to distances of a few Mpc for lighter halos. The degree of mixing between neighboring compact binary populations computed in this way is severely enhanced in environments with a high number density of galaxies. We find that SGRB redshift estimates based solely on the nearest galaxy in projection can be very inaccurate, if progenitor systems inhere large systematic kicks at birth.Comment: 7 pages, 3 figures, accepted for publication in ApJ

Short-Term H-alpha Variability in M Dwarfs

We spectroscopically study the variability of H-alpha emission in mid- to late-M dwarfs on timescales of ~0.1-1 hr as a proxy for magnetic variability. About 80% of our sample exhibits statistically significant variability on the full range of timescales probed by the observations, and with amplitude ratios in the range of ~1.2-4. No events with an order of magnitude increase in H-alpha luminosity were detected, indicating that their rate is < 0.05 /hr (95% confidence level). We find a clear increase in variability with later spectral type, despite an overall decrease in H-alpha "activity" (i.e., L_{H-alpha}/L_{bol}). For the ensemble of H-alpha variability events, we find a nearly order of magnitude increase in the number of events from timescales of about 10 to 30 min, followed by a roughly uniform distribution at longer durations. The event amplitudes follow an exponential distribution with a characteristic scale of Max(EW)/Min(EW)}-1 ~ 0.7. This distribution predicts a low rate of ~ 10^{-6} /hr for events with (Max(EW)/Min(EW) > 10, but serendipitous detections of such events in the past suggests that they represent a different distribution. Finally, we find a possible decline in the amplitude of events with durations of > 0.5 hr, which may point to a typical energy release in H-alpha events for each spectral type (E_{H-alpha} ~ L_{H-alpha} x t ~ const). Longer observations of individual active objects are required to further investigate this possibility. Similarly, a larger sample may shed light on whether H-alpha variability correlates with properties such as age or rotation velocity.Comment: Accepted for publication in Ap

Incorporation of Nitrogen into Organics Produced by Fischer-Tropsch Type Chemistry

Laboratory simulations have demonstrated that hydrothermal systems have the potential to produce a range of organic compounds through Fischer-Tropsch type (FTT) chemistry. The distribution of products depends on several factors, including the abundance and composition of feed-stock molecules, reaction temperature, and the physical and chemical characteristics of catalytic materials included in the reactions. The majority of studies per-formed to date have focused solely on inclusion of CO2 or CO and H2 as the carbon, oxygen and hydrogen sources, which limits the possible products to hydro-carbons, alcohols and carboxylic acids. A few studies have included nitrogen in the form of ammonia, which led to the production of amino acids and nitrogenous bases; and a separate suite of studies included sulfur as sulfide minerals or H2S, which yielded products such as thiols and amino acids. Although these demonstrations provide compelling evidence that FTT reactions can produce compounds of interest for the origins of life, such reactions have been conducted under a very limited range of conditions and the synthetic reaction mechanisms have generally not been well-characterized. As a consequence, it is difficult to extrapolate these results to geologic systems or to evaluate how variations in reactant compositions would affect the distribution of products over time. We have begun a series of laboratory experiments that will incorporate a range of precursor molecules in varying compositions to determine how these variables affect the relative amounts and speciation of life-essential elements in organic molecules produced under FTT conditions. In the present work, we focus on systems containing C, H, O and N

How do large banking organizations manage their capital ratio?

Large banking organizations in the U.S. hold significantly more equity capital than the minimum required by bank regulators. This capital cushion has built up during a period of unusual profitability for the banking system, leading some observers to argue that the capital merely reflects recent profits. Others contend that the banks deliberately choose target capital levels based on their risk exposures and their counterparties’ sensitivities to default risk. In either case, the existence of “excess” capital makes it difficult to observe how banks manage their capital levels, particularly in response to regulatory changes (such as Basel II). We propose several hypotheses to explain this “excess” capital, and test these hypotheses using annual panel data for large, publicly traded U.S. bank holding companies (BHCs) from 1992 through 2006, and an innovative partial adjustment approach that allows both the target capital ratios and the speed of adjustment toward those targets to vary with firm-specific characteristics. We find evidence to suggest that large BHCs actively managed their capital ratios during our sample period. Our tests suggest that large BHCs choose target capital levels substantially above well-capitalized regulatory minima; that these targets increase with BHC risk but decrease with BHC size; that BHCs adjust toward these targets relatively quickly; and that adjustment speeds are faster for poorly capitalized BHCs, but slower (ceteris paribus) for BHCs under severe regulatory pressure.Banks and banking ; Capital