8,082 research outputs found

    Effective Lagrangian for a Technicolor Model without Exact Custodial Symmetry

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    Effective Lagrangian including technimesons is constructed for a realistic one-family Technicolor model without exact custodial symmetry. Tree level contribution to oblique correction parameters SS and UU due to spin 1 technimesons are computed with the effective Lagrangian. An isospin breaking term which is associated with technilepton vector mesons gives a negative contribution to the electroweak radiative correction parameter SS due to mixing between I=0I=0 and I=1I=1 vector mesons. UU receives non-zero contribution due to exotic left-handed charged vector mesons and its sign can be both negative and positive.Comment: 30 pages plus 1 table and 4 figures (7 postscript files append.), Latex, (HUPD-9406

    Confirming the Detection of an Intergalactic X-ray Absorber Toward PKS 2155-304

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    We present new observations on PKS 2155-304 with the Chandra Low Energy Transmission Grating Spectrometer (LETG), using the Advanced CCD Imaging Spectrometer (ACIS). We confirm the detection of an absorption line plausibly identified as OVIII Ly-alpha from the warm-hot intergalactic medium associated with a small group of galaxies along the line of sight, as originally reported by Fang et al. 2002 (here after FANG02). Combining the previous observations in FANG02 and five new, long observations on the same target, we increase the total exposure time by a factor of three, and the total counts per resolution element by a factor of five. The measured line equivalent width is smaller than that observed in FANG02, but still consistent at 90% confidence. We also analyze the XMM-Newton observations on the same target, as well as observations using the Chandra LETG and the High Resolution Camera (HRC) combination. These observations have been used to challenge our reported detection. While no line is seen in either the XMM-Newton and the Chandra LETG+HRC data, we find that our result is consistent with the upper limits from both data sets. We attribute the non-detection to (1) higher quality of the Chandra LETG+ACIS spectrum, and (2) the rather extended wings of the line spread functions of both the XMM RGS and the Chandra LETG+HRC. We discuss the implication of our observation on the temperature and density of the absorber. We also confirm the detection of z ~ 0 OVII absorption and, comparing with previous Chandra analysis, we obtain much tighter constraints on the line properties.Comment: 10 pages, 8 figures, accepted for publication in Ap

    Proto-clusters in the Lambda CDM Universe

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    We compare the highly clustered populations of very high redshift galaxies with proto-clusters identified numerically in a standard Λ\LambdaCDM universe (Ω0=0.3,λ0=0.7\Omega_0=0.3, \lambda_0=0.7) simulation. We evolve 256^3 dark matter particles in a comoving box of side 150h^{-1}Mpc. By the present day there are 63 cluster sized objects of mass in excess of 10^{14}h^{-1}Mo in this box. We trace these clusters back to higher redshift finding that their progenitors at z=4--5 are extended regions of typically 20--40 Mpc (comoving) in size, with dark halos of mass in excess of 10^{12}h^{-1}Mo and are overdense by typically 1.3--13 times the cosmological mean density. Comparison with the observation of Lyman alpha emitting (LAEs) galaxies at z=4.86 and at z=4.1 indicates that the observed excess clustering is consistent with that expected for a proto-cluster region if LAEs typically correspond to massive dark halos of more than 10^{12}h^{-1}Mo. We give a brief discussion on the relation between high redshift concentration of massive dark halos and present day rich clusters of galaxies.Comment: 4 pages, 5 figures, Accepted for publication in ApJ Letter

    Gay-Straight Alliances as Settings to Discuss Health Topics: Individual and Group Factors Associated with Substance Use, Mental Health, and Sexual Health Discussions

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    Sexual minority (e.g. lesbian, gay, bisexual, questioning; LGBQ) and gender minority (e.g. transgender) youth experience myriad health risks. Gay-Straight Alliances (GSAs) are school-based settings where they may have opportunities to discuss substance use, mental health, and sexual health issues in ways that are safe and tailored to their experiences. Attention to these topics in GSAs could aid in developing programming for these settings. Among 295 youth from 33 Massachusetts high-school GSAs (69% LGBQ, 68% cisgender female, 68% White, Mage = 16.06), we examined how often youth discussed these topics within their GSA and identified factors associated with having more of these discussions. Youth and GSAs as a whole varied in their frequency of discussing these topics. Youth who accessed more information/resources in the GSA and did more advocacy more frequently engaged in discussions around substance use, mental health and sexual health. Youth who reported greater victimization more often discussed substance use and mental health, but not sexual health. Finally, GSAs whose members collectively reported greater victimization more frequently discussed these topics. These findings can assist the development of health programming to be delivered within GSAs

    Cultures and institutions: dispositional and contextual explanations for country-of-origin effects in MNC 'ethnocentric' staffing practices

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    Although the country-of-origin effect on staffing practices of multinational corporations (MNCs) is well-known, its underlying mechanisms are under-theorized. Drawing on the cross-cultural management and comparative institutionalism literatures, we propose an overarching, theory-based framework with two mechanisms, dispositional and contextual, that might explain country-of-origin effects in MNCs’ use of parent-country nationals (PCNs) in their foreign subsidiaries’ top management teams. The tendency of MNCs from some home countries to staff these positions with PCNs is typically labeled as “ethnocentric”, a word imbued with negative intentions referring mainly to the dispositional rationale behind this staffing choice. However, fuzzy-set qualitative comparative analysis (fsQCA) of staffing practices of MNCs from ten home countries shows that both mechanisms – dispositional and contextual – have considerable explanatory power. Our methodological approach enables us to analyze conceptually distinct, yet empirically intertwined, societal-level explanations as a pattern, and thus offers a viable solution to integrate different perspectives in international and comparative research

    Extended general design theory

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    Transient expression of the coat protein of Apple chlorotic leaf spot virus inhibits the viral RNA accumulation in Nicotiana occidentalis

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    The coat protein of Apple chlorotic leaf spot virus (ACLSV-CP) plays a crucial role in infectivity and efficient viral RNA accumulation in host cells (J. Gen. Virol, 88, 2007). In this study, the effect of ACLSV-CP on viral RNA accumulation in Nicotiana occidentalis was investigated. The CP, CPm40 (an amino acid (aa) substitution of Ala to Ser at aa position 40), CPm75 (a substitution of Phe to Tyr at aa position 75), and CPm40m75 (two aa substitutions at positions 40 and 75) of ACLSV (P205) were transiently expressed in N. occidentalis leaves by agroinfiltration. Immunoblot analysis showed that CP and CPm40m75 accumulated in infiltrated tissues, in contrast to CPm40 and CPm75 which were not detected, suggesting that the stable accumulation of CP is important for effective viral RNA accumulation. However, co-agroinfiltration of an infectious ACLSV cDNA clone (pBICLSF) or pBICLSF-based CP mutants (pBICLCPm40, pBICLCPm75, and pBICLCPm40m75) with a vector expressing CP (pBE2113-CP) showed no viral genomic RNA accumulations were found in any leaves infiltrated with these constructs. The inhibition of ACLSV-RNA accumulation was found only in leaves co-expressed with CP protein, but not with a frame-shift mutant of CP, a movement protein (P50), and a frame-shift mutant of P50. Keywords: Apple chlorotic leaf spot virus, coat protein, protein stability, coat protein mediated resistance (CP-MR), agroinfiltratio
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