Properties of optically selected BL Lac candidates from the SDSS

\textbf{Context.} Deep optical surveys open the avenue for find large numbers of BL Lac objects that are hard to identify because they lack the unique properties classifying them as such. While radio or X-ray surveys typically reveal dozens of sources, recent compilations based on optical criteria alone have increased the number of BL Lac candidates considerably. However, these compilations are subject to biases and may contain a substantial number of contaminating sources. \textbf{Aims.} In this paper we extend our analysis of 182 optically selected BL Lac object candidates from the SDSS with respect to an earlier study. The main goal is to determine the number of bona fide BL Lac objects in this sample. \textbf{Methods.} We examine their variability characteristics, determine their broad-band radio-UV SEDs, and search for the presence of a host galaxy. In addition we present new optical spectra for 27 targets with improved S/N with respect to the SDSS spectra. \textbf{Results.} At least 59% of our targets have shown variability between SDSS DR2 and our observations by more than 0.1-0.27 mag de- pending on the telescope used. A host galaxy was detected in 36% of our targets. The host galaxy type and luminosities are consistent with earlier studies of BL Lac host galaxies. Simple fits to broad-band SEDS for 104 targets of our sample derived synchrotron peak frequencies between $13.5 \leq \mathrm{log}_{10}(\nu_{\mathrm{peak}}) \leq 16$ with a peak at $\mathrm{log}_{10} \sim 14.5$. Our new optical spectra do not reveal any new redshift for any of our objects. Thus the sample contains a large number of bona fide BL Lac objects and seems to contain a substantial fraction of intermediate-frequency peaked BL Lacs.Comment: Accepted for publication in A\&

Comparison of feeding diets diluted with sorghum-sudangrass silage or low-quality grass on nutrient intake and digestibility and growth performance of Holstein dairy heifers

This study was carried out to evaluate the nutrient intakes and growth of dairy heifers offered an alfalfa silage– corn silage diet (CON; 14.3% crude protein, 61.1% total digestible nutrients, 47.9% neutral detergent fiber) compared with diets containing 1 of 2 types of sorghumsudangrass (SS) silages: conventional or photoperiod sensitive. The objective of the study was to determine the potential to use SS to control dry matter (DM) and nutrient intakes and weight gain. Both diets were similar in nutrient composition, with approximately 13% crude protein, 60 to 61% total digestible nutrients, and 55% neutral detergent fiber. Seventy-two Holstein heifers (16–18 mo at study initiation) were blocked by initial body weight (light = 422 ± 12.8 kg; medium = 455 ± 14.8 kg; heavy = 489 ± 16.7 kg) with 3 pens assigned to each weight block (8 heifers/pen; 24 heifers/block). The 3 diets were randomly allocated to the pens within each block and offered for 12 wk. Heifers offered the CON diet had greater DM, protein, and energy intakes compared with those offered the SS silage-based diets due to the greater neutral detergent fiber concentration of the SS diets. With lower DM and nutrient intakes, average daily gain was in the recommended range (0.8– 1 kg/d for Holstein heifers) for heifers offered the SS silage-based diets (mean of 0.92 kg/d for both SS diets vs. 1.11 kg/d for CON). Sorting behaviors for heifers offered both SS diets were more aggressive against long, medium, and short particles compared with those of heifers offered the CON diet; however, heifers sorted large particles from photoperiod-sensitive silage more aggressively than those from conventional silage. Based on this study, SS silage-based diets can control the DM and energy intakes for heifers and maintain optimum growth rates, with harvesting at a shorter chop length likely helping to alleviate sorting issues

The origin of HIMU in the SW Pacific : evidence from intraplate volcanism in southern New Zealand and subantarctic islands

Author Posting. © The Author, 2006. This is the author's version of the work. It is posted here by permission of Oxford University Press for personal use, not for redistribution. The definitive version was published in Journal of Petrology 27 (2006): 1673-1704, doi:10.1093/petrology/egl024.This paper presents field, geochemical and isotopic (Sr, Nd, Pb) results on basalts from the Antipodes, Campbell and Chatham Islands, New Zealand. New 40Ar/39Ar age determinations along with previous K-Ar dates reveal three major episodes of volcanic activity on Chatham Island (85-82, 41-35, ~5 Ma). Chatham and Antipodes samples comprise basanite, alkali and transitional basalts that have HIMU-like isotopic (206Pb/204Pb >20.3-20.8, 87Sr/86Sr 0.5128) and trace element affinities (Ce/Pb 28-36, Nb/U 34-66, Ba/Nb 4-7). The geochemistry of transitional to Q-normative samples from Campbell Island is explained by interaction with continental crust. The volcanism is part of a long-lived (~100 Myr), low-volume, diffuse alkaline magmatic province that includes deposits on the North and South Islands as well as portions of West Antarctica and SE Australia. All of the continental areas were juxtaposed on the eastern margin of Gondwanaland at >83 Ma. A ubiquitous feature of mafic alkaline rocks from this region is their depletion in K and Pb relative to other highly incompatible elements when normalized to primitive mantle values. The inversion of trace element data indicates enriched mantle sources that contain variable proportions of hydrous minerals. We propose that the mantle sources represent continental lithosphere that host amphibole/phlogopite-rich veins formed by plume and/or subduction related metasomatism between 500 and 100 Ma. The strong HIMU signature (206Pb/204Pb >20.5) is considered to be an in-grown feature generated by partial-dehydration and loss of hydrophile elements (Pb, Rb, K) relative to more magmaphile elements (Th, U, Sr) during short-term storage at the base of the lithosphere.This study was supported by National Science Foundation Grants OPP-9419686 and OPP-0003702 awarded to KSP

Conservation Laws in Cellular Automata

If X is a discrete abelian group and B a finite set, then a cellular automaton (CA) is a continuous map F:B^X-->B^X that commutes with all X-shifts. If g is a real-valued function on B, then, for any b in B^X, we define G(b) to be the sum over all x in X of g(b_x) (if finite). We say g is `conserved' by F if G is constant under the action of F. We characterize such `conservation laws' in several ways, deriving both theoretical consequences and practical tests, and provide a method for constructing all one-dimensional CA exhibiting a given conservation law.Comment: 19 pages, LaTeX 2E with one (1) Encapsulated PostScript figure. To appear in Nonlinearity. (v2) minor changes/corrections; new references added to bibliograph

Conductivity in quasi two-dimensional systems

The conductivity in quasi two-dimensional systems is calculated using the quantum kinetic equation. Linearizing the Lenard-Balescu collision integral with the extension to include external field dependences allows one to calculate the conductivity with diagrams beyond the GW approximation including maximally crossed lines. Consequently the weak localization correction as an interference effect appears here from the field dependence of the collision integral (the latter dependence sometimes called intra-collisional field effect). It is shown that this weak localization correction has the same origin as the Debye-Onsager relaxation effect in plasma physics. The approximation is applied to a system of quasi two-dimensional electrons in hetero-junctions which interact with charged and neutral impurities and the low temperature correction to the conductivity is calculated analytically. It turns out that the dynamical screening due to charged impurities leads to a linear temperature dependence, while the scattering from neutral impurities leads to the usual Fermi-liquid behavior. By considering an appropriate mass action law to determine the ratio of charged to neutral impurities we can describe the experimental metal-insulator transition at low temperatures as a Mott-Hubbard transition.Comment: 7 pages 7 pages appendix 11 figure

Pericardial effusion of HIV-infected patients - results of a prospective multicenter cohort study in the era of antiretroviral therapy

<p>Abstract</p> <p>Background</p> <p>Patients with human immunodeficiency virus (HIV) infection have an increased risk of cardiovascular diseases. Previous publications described pericardial effusion as one of the most common HlV-associated cardiac affiliations. The aim of the current study was to investigate if pericardial effusion still has a relevant meaning of HIV-infected patients in the era of antiretroviral therapy.</p> <p>Methods</p> <p>The HIV-HEART (HIV-infection and HEART disease) study is a cardiology driven, prospective and multicenter cohort study. Outpatients with a known HIV-infection were recruited during a 20 month period in a consecutive manner from September 2004 to May 2006. The study comprehends classic parameters of HIV-infection, comprising CD4-cell count (cluster of differentiation) and virus load, as well as non-invasive tests of cardiac diseases, including a thorough transthoracic echocardiography.</p> <p>Results</p> <p>802 HIV-infected patients (female: 16.6%) with a mean age of 44.2 ± 10.3 years, were included. Duration of HIV-infection since initial diagnosis was 7.6 ± 5.8 years. Of all participants, 85.2% received antiretroviral therapy. Virus load was detectable in 34.4% and CD4 - cell count was in 12.4% less than 200 cells/μL. Pericardial effusions were present in only two patients of the analysed population. None of the participants had signs of a relevant cardiovascular impairment by pericardial effusion.</p> <p>Conclusions</p> <p>Our results demonstrate that the era of antiretroviral therapy goes along with low rates of pericardial effusions in HIV-infected outpatients. Our findings are in contrast to the results of publications, performed before the common use of antiretroviral therapy.</p

Spin-Boson Hamiltonian and Optical Absorption of Molecular Dimers

An analysis of the eigenstates of a symmetry-broken spin-boson Hamiltonian is performed by computing Bloch and Husimi projections. The eigenstate analysis is combined with the calculation of absorption bands of asymmetric dimer configurations constituted by monomers with nonidentical excitation energies and optical transition matrix elements. Absorption bands with regular and irregular fine structures are obtained and related to the transition from the coexistence to a mixing of adiabatic branches in the spectrum. It is shown that correlations between spin states allow for an interpolation between absorption bands for different optical asymmetries.Comment: 15 pages, revTeX, 8 figures, accepted for publication in Phys. Rev.