The Hobby-Eberly Telescope Chemical Abundances Of Stars In The Halo (CASH) Project. I. The Lithium-, s-, And r-Enhanced Metal-Poor Giant HKII 17435-00532

We present the first detailed abundance analysis of the metal-poor giant HKII 17435-00532. This star was observed as part of the University of Texas long-term project Chemical Abundances of Stars in the Halo ( CASH). A spectrum was obtained with the High Resolution Spectrograph (HRS) on the Hobby-Eberly Telescope with a resolving power of R similar to 15,000. Our analysis reveals that this star may be located on the red giant branch, red horizontal branch, or early asymptotic giant branch. We find that this metal-poor (Fe/H = -2.2) star has an unusually high lithium abundance [log epsilon(Li) +2.1], mild carbon (C/Fe = +0.7) and sodium (]Na/Fe] = +0.6) enhancement, as well as enhancement of both s-process ([Ba/Fe] = +0.8) and r-process ([Eu/Fe] = +0.5) material. The high Li abundance can be explained by self-enrichment through extra mixing that connects the convective envelope with the outer regions of the H-burning shell. If so, HKII 17435-00532 is the most metal-poor star in which this short-lived phase of Li enrichment has been observed. The Na and n-capture enrichment can be explained by mass transfer from a companion that passed through the thermally pulsing AGB phase of evolution with only a small initial enrichment of r-process material present in the birth cloud. Despite the current nondetection of radial velocity variations (over similar to 180 days), it is possible that HKII 17435 - 00532 is in a long-period or highly inclined binary system, similar to other stars with similar n-capture enrichment patterns.NASA AAS Small Research Grant ProgramGALEX GI 05-GALEX05-27Italian MIUR-PRIN06 ProjectNSF AST 06-07708, AST04-06784, AST 07-0776, PHY 02-15783JINA AST 07-07447Astronom

Finite-Size Scaling in Two-Dimensional Superfluids

Using the $x-y$ model and a non-local updating scheme called cluster Monte Carlo, we calculate the superfluid density of a two dimensional superfluid on large-size square lattices $L \times L$ up to $400\times 400$. This technique allows us to approach temperatures close to the critical point, and by studying a wide range of $L$ values and applying finite-size scaling theory we are able to extract the critical properties of the system. We calculate the superfluid density and from that we extract the renormalization group beta function. We derive finite-size scaling expressions using the Kosterlitz-Thouless-Nelson Renormalization Group equations and show that they are in very good agreement with our numerical results. This allows us to extrapolate our results to the infinite-size limit. We also find that the universal discontinuity of the superfluid density at the critical temperature is in very good agreement with the Kosterlitz-Thouless-Nelson calculation and experiments.Comment: 13 pages, postscript fil

The SPEAR Instrument and On-Orbit Performance

The SPEAR (or 'FIMS') instrumentation has been used to conduct the first large-scale spectral mapping of diffuse cosmic far ultraviolet (FUV, 900-1750 AA) emission, including important diagnostics of interstellar hot (10^4 K - 10^6 K) and photoionized plasmas, H_2, and dust scattered starlight. The instrumentation's performance has allowed for the unprecedented detection of astrophysical diffuse far UV emission lines. A spectral resolution of 550 and an imaging resolution of 5' is achieved on-orbit in the Short (900 - 1175 AA) and Long (1335 - 1750 AA) bandpass channels within their respective 7.4 deg x 4.3' and 4.0 deg x 4.6' fields of view. We describe the SPEAR imaging spectrographs, their performance, and the nature and handling of their data

Scaling of the specific heat in superfluid films

We study the specific heat of the $x-y$ model on lattices $L \times L \times H$ with $L \gg H$ (i.e. on lattices representing a film geometry) using the Cluster Monte--Carlo method. In the $H$--direction we apply Dirichlet boundary conditions so that the order parameter in the top and bottom layers is zero. We find that our results for the specific heat of various thickness size $H$ collapse on the same universal scaling function. The extracted scaling function of the specific heat is in good agreement with the experimentally determined universal scaling function using no free parameters.Comment: 4 pages, uuencoded compressed PostScrip

Ozone production and trace gas correlations during the June 2000 MINATROC intensive measurement campaign at Mt. Cimone

An intensive measurement campaign was performed in June 2000 at the Mt. Cimone station (44°11' N-10°42' E, 2165 m asl, the highest mountain in the northern Italian Apennines) to study photochemical ozone production in the lower free troposphere. In general, average mixing ratios of important trace gases were not very high (121 ± 20 ppbv CO, 0.284 ± 0.220 ppbv NOx, 1.15 ± 0.8 ppbv NOy, 58 ± 9 ppbv O₃), which indicates a small contribution by local pollution. Those trace gas levels are representative of continental background air, which is further supported by the analysis of VOCs (e.g.: C₂H₆ = (905 ± 200) pptv, C₃H₈ = (268 ±110) pptv, C₂H₂ = (201 ± 102) pptv, C₅H₈ = (111 ± 124) pptv, benzene = (65 ± 33) pptv). Furthermore, significant diurnal variations for a number of trace gases (O₃, CO, NOx, NOy, HCHO) indicate the presence of free tropospheric airmasses at nighttime as a consequence of local catabatic winds. Average mid-day peroxy radical concentrations at Mt. Cimone are of the order of 30 pptv. At mean NO concentrations of the order of 40 pptv this gives rise to significant in situ net O₃ production of 0.1-0.3 ppbv/hr. The importance of O₃production is supported by correlations between O₃, CO, NOz, and HCHO, and between HCHO, CO and NOy

PlantGDB: a resource for comparative plant genomics

PlantGDB (http://www.plantgdb.org/) is a genomics database encompassing sequence data for green plants (Viridiplantae). PlantGDB provides annotated transcript assemblies for >100 plant species, with transcripts mapped to their cognate genomic context where available, integrated with a variety of sequence analysis tools and web services. For 14 plant species with emerging or complete genome sequence, PlantGDB's genome browsers (xGDB) serve as a graphical interface for viewing, evaluating and annotating transcript and protein alignments to chromosome or bacterial artificial chromosome (BAC)-based genome assemblies. Annotation is facilitated by the integrated yrGATE module for community curation of gene models. Novel web services at PlantGDB include Tracembler, an iterative alignment tool that generates contigs from GenBank trace file data and BioExtract Server, a web-based server for executing custom sequence analysis workflows. PlantGDB also hosts a plant genomics research outreach portal (PGROP) that facilitates access to a large number of resources for research and training

One-step isolation and biochemical characterization of a highlyactive plant PSII monomeric core

We describe a one-step detergent solubilization protocol for isolating a highly active form of Photosystem II (PSII) from Pisum sativum L. Detailed characterization of the preparation showed that the complex was a monomer having no light harvesting proteins attached. This core reaction centre complex had, however, a range of low molecular mass intrinsic proteins as well as the chlorophyll binding proteins CP43 and CP47 and the reaction centre proteins D1 and D2. Of particular note was the presence of a stoichiometric level of PsbW, a low molecular weight protein not present in PSII of cyanobacteria. Despite the high oxygen evolution rate, the core complex did not retain the PsbQ extrinsic protein although there was close to a full complement of PsbO and PsbR and partial level of PsbP. However, reconstitution of PsbP and PsbPQ was possible. The presence of PsbP in absence of LHCII and other chlorophyll a/b binding proteins confirms that LHCII proteins are not a strict requirement for the assembly of this extrinsic polypeptide to the PSII core in contrast with the conclusion of Caffarri et al. (2009)

Nitrate- and silicate-competition among antarctic phytoplankton

Natural phytoplankton from antarctic waters in the Drake Passage were used for competition experiments in semicontinuous cultures. The outcome of interspecific competition for silicate and nitrate was studied at a range of Si:N ratios (from 2.6:1 to 425:1) and at three different dilution rates. For five species Monod kinetics of silicate-and nitrate-limited growth has been established. Comparison between theoretical predictions derived from Monod kinetics and the outcome of competition experiments showed only minor deviations. Contrary to literature data, considerable depletion of nitrate was found in antarctic seawater. Both the concentrations of soluble silicate and of nitrate were too low to support maximum growth rates of some of the diatom species under investigation

NGC 2770 - a supernova Ib factory?

NGC 2770 has been the host of three supernovae of Type Ib during the last 10 years, SN 1999eh, SN 2007uy and SN 2008D. SN 2008D attracted special attention due to the serendipitous discovery of an associated X-ray transient. In this paper, we study the properties of NGC 2770 and specifically the three SN sites to investigate whether this galaxy is in any way peculiar to cause a high frequency of SNe Ib. We model the global SED of the galaxy from broadband data and derive a star-formation and SN rate comparable to the values of the Milky Way. We further study the galaxy using longslit spectroscopy covering the major axis and the three SN sites. From the spectroscopic study we find subsolar metallicities for the SN sites, a high extinction and a moderate star-formation rate. In a high resolution spectrum, we also detect diffuse interstellar bands in the line-of-sight towards SN 2008. A comparison of NGC 2770 to the global properties of a galaxy sample with high SN occurance (at least 3 SN in the last 100 years) suggests that NGC 2770 is not particularly destined to produce such an enhancement of observed SNe observed. Its properties are also very different from gamma-ray burst host galaxies. Statistical considerations on SN Ib detection rates give a probability of ~1.5% to find a galaxy with three Ib SNe detected in 10 years. The high number of rare Ib SNe in this galaxy is therefore likely to be a coincidence rather than special properties of the galaxy itself. NGC 2770 has a small irregular companion, NGC 2770B, which is highly starforming, has a very low mass and one of the lowest metallicities detected in the nearby universe as derived from longslit spectroscopy. In the most metal poor part, we even detect Wolf-Rayet features, against the current models of WR stars which require high metallicities.Comment: 15 pages, 10 figures, submitted to Ap

Photoswitchable diacylglycerols enable optical control of protein kinase C.

Increased levels of the second messenger lipid diacylglycerol (DAG) induce downstream signaling events including the translocation of C1-domain-containing proteins toward the plasma membrane. Here, we introduce three light-sensitive DAGs, termed PhoDAGs, which feature a photoswitchable acyl chain. The PhoDAGs are inactive in the dark and promote the translocation of proteins that feature C1 domains toward the plasma membrane upon a flash of UV-A light. This effect is quickly reversed after the termination of photostimulation or by irradiation with blue light, permitting the generation of oscillation patterns. Both protein kinase C and Munc13 can thus be put under optical control. PhoDAGs control vesicle release in excitable cells, such as mouse pancreatic islets and hippocampal neurons, and modulate synaptic transmission in Caenorhabditis elegans. As such, the PhoDAGs afford an unprecedented degree of spatiotemporal control and are broadly applicable tools to study DAG signaling