43 research outputs found

    Spectacular nucleosynthesis from early massive stars

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    Stars formed with initial mass over 50 Msun are very rare today, but they are thought to be more common in the early universe. The fates of those early, metal-poor, massive stars are highly uncertain. Most are expected to directly collapse to black holes, while some may explode as a result of rotationally powered engines or the pair-creation instability. We present the chemical abundances of J0931+0038, a nearby low-mass star identified in early followup of SDSS-V Milky Way Mapper, which preserves the signature of unusual nucleosynthesis from a massive star in the early universe. J0931+0038 has relatively high metallicity ([Fe/H] = -1.76 +/- 0.13) but an extreme odd-even abundance pattern, with some of the lowest known abundance ratios of [N/Fe], [Na/Fe], [K/Fe], [Sc/Fe], and [Ba/Fe]. The implication is that a majority of its metals originated in a single extremely metal-poor nucleosynthetic source. An extensive search through nucleosynthesis predictions finds a clear preference for progenitors with initial mass > 50 Msun, making J0931+0038 one of the first observational constraints on nucleosynthesis in this mass range. However the full abundance pattern is not matched by any models in the literature. J0931+0038 thus presents a challenge for the next generation of nucleosynthesis models and motivates study of high-mass progenitor stars impacted by convection, rotation, jets, and/or binary companions. Though rare, more examples of unusual early nucleosynthesis in metal-poor stars should be found in upcoming large spectroscopic surveys.Comment: 11 pages + 22 page appendix, accepted to ApJ

    Measurement of the underlying event activity in pp collisions at √s = 0.9 and 7 TeV with the novel jet-area/median approach

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    Open Access: This article is distributed under the terms of the Creative Commons Attribution License.-- Chatrchyan, S. et al.The first measurement of the charged component of the underlying event using the novel >jet-area/median> approach is presented for proton-proton collisions at centre-of-mass energies of 0.9 and 7 TeV. The data were recorded in 2010 with the CMS experiment at the LHC. A new observable, sensitive to soft particle production, is introduced and investigated inclusively and as a function of the event scale defined by the transverse momentum of the leading jet. Various phenomenological models are compared to data, with and without corrections for detector effects. None of the examined models describe the data satisfactorily. © 2012 SISSA.Acknowledge support from BMWF and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); MoER, SF0690030s09 and ERDF (Estonia); Academy of Finland, MEC, and HIP (Finland); CEA and CNRS/IN2P3 (France);BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF and WCU (Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); MSI (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine, Uzbekistan); MON, RosAtom, RAS and RFBR (Russia); MSTD (Serbia); SEIDI and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); ThEP, IPST and NECTEC (Thailand); TUBITAK and TAEK (Turkey); NASU (Ukraine); STFC (United Kingdom); DOE and NSF (USA). Individuals have received support from the Marie-Curie program and the European Research Council (European Union); the Leventis Foundation; the A. P. Sloan Foundation; the Alexander von Humboldt Foundation; the Austrian Science Fund (FWF); the Belgian Federal Science Policy Office; the Fonds pour la Formation à la Recherche dans l’Industrie et dans l’Agriculture (FRIA-Belgium); the Agentschap voor Innovatie door Wetenschap en Technologie (IWTBelgium); the Ministry of Education, Youth and Sports (MEYS) of Czech Republic; the Council of Science and Industrial Research, India; the Compagnia di San Paolo (Torino); and the HOMING PLUS program of Foundation for Polish Science, cofinanced from European Union, Regional Development Fund.Peer Reviewe

    Search for physics beyond the standard model in events with a Z boson, jets, and missing transverse energy in pp collisions at √s̅ = 7 TeV

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    Spectacular Nucleosynthesis from Early Massive Stars

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    Stars that formed with an initial mass of over 50 M ⊙ are very rare today, but they are thought to be more common in the early Universe. The fates of those early, metal-poor, massive stars are highly uncertain. Most are expected to directly collapse to black holes, while some may explode as a result of rotationally powered engines or the pair-creation instability. We present the chemical abundances of J0931+0038, a nearby low-mass star identified in early follow-up of the SDSS-V Milky Way Mapper, which preserves the signature of unusual nucleosynthesis from a massive star in the early Universe. J0931+0038 has a relatively high metallicity ([Fe/H] = −1.76 ± 0.13) but an extreme odd–even abundance pattern, with some of the lowest known abundance ratios of [N/Fe], [Na/Fe], [K/Fe], [Sc/Fe], and [Ba/Fe]. The implication is that a majority of its metals originated in a single extremely metal-poor nucleosynthetic source. An extensive search through nucleosynthesis predictions finds a clear preference for progenitors with initial mass >50 M ⊙, making J0931+0038 one of the first observational constraints on nucleosynthesis in this mass range. However, the full abundance pattern is not matched by any models in the literature. J0931+0038 thus presents a challenge for the next generation of nucleosynthesis models and motivates the study of high-mass progenitor stars impacted by convection, rotation, jets, and/or binary companions. Though rare, more examples of unusual early nucleosynthesis in metal-poor stars should be found in upcoming large spectroscopic surveys

    Measurement of the charge asymmetry in top-quark pair production in the lepton-plus-jets final state in pp collision data at s=8TeV\sqrt{s}=8\,\mathrm TeV{} with the ATLAS detector

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    ATLAS Run 1 searches for direct pair production of third-generation squarks at the Large Hadron Collider

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    Reconstructing contemporary democracy

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    Democratic practice varies historically, and transformations of the societal context require accompanying reconstructions of democracy if “rule by the people” is to remain meaningful. Contemporary society is witnessing particularly profound changes in underlying structures of space, governance, and identity. Fundamental reconsideration of democracy is therefore also needed. This article first develops a generic understanding of democracy; next elaborates on currently unfolding transformations of geography, regime, and community; and then develops a five-faceted reconstruction of democracy to meet these changed circumstances. This prescription entails: (1) reconceptualizing democracy, shifting away from obsolete assumptions of territorialist space, statist regulation, and nationalist identity; (2) refashioning civic education to empower all citizens to act in this new situation; (3) building effective institutional mechanisms of public accountability in respect of an emergent polycentric mode of governance; (4) effecting progressive structural redistributions of resources and power in order that all stakeholders in contemporary public policy issues have more equal opportunities of political participation; and (5) nurturing positive practices of intercultural recognition, communication, and negotiation

    Changes in End-of-Life Practices in European Intensive Care Units From 1999 to 2016.

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    Importance End-of-life decisions occur daily in intensive care units (ICUs) around the world, and these practices could change over time. Objective To determine the changes in end-of-life practices in European ICUs after 16 years. Design, Setting, and Participants Ethicus-2 was a prospective observational study of 22 European ICUs previously included in the Ethicus-1 study (1999-2000). During a self-selected continuous 6-month period at each ICU, consecutive patients who died or had any limitation of life-sustaining therapy from September 2015 until October 2016 were included. Patients were followed up until death or until 2 months after the first treatment limitation decision. Exposures Comparison between the 1999-2000 cohort vs 2015-2016 cohort. Main Outcomes and Measures End-of-life outcomes were classified into 5 mutually exclusive categories (withholding of life-prolonging therapy, withdrawing of life-prolonging therapy, active shortening of the dying process, failed cardiopulmonary resuscitation [CPR], brain death). The primary outcome was whether patients received any treatment limitations (withholding or withdrawing of life-prolonging therapy or shortening of the dying process). Outcomes were determined by senior intensivists. Results Of 13 625 patients admitted to participating ICUs during the 2015-2016 study period, 1785 (13.1%) died or had limitations of life-prolonging therapies and were included in the study. Compared with the patients included in the 1999-2000 cohort (n = 2807), the patients in 2015-2016 cohort were significantly older (median age, 70 years [interquartile range {IQR}, 59-79] vs 67 years [IQR, 54-75]; P < .001) and the proportion of female patients was similar (39.6% vs 38.7%; P = .58). Significantly more treatment limitations occurred in the 2015-2016 cohort compared with the 1999-2000 cohort (1601 [89.7%] vs 1918 [68.3%]; difference, 21.4% [95% CI, 19.2% to 23.6%]; P < .001), with more withholding of life-prolonging therapy (892 [50.0%] vs 1143 [40.7%]; difference, 9.3% [95% CI, 6.4% to 12.3%]; P < .001), more withdrawing of life-prolonging therapy (692 [38.8%] vs 695 [24.8%]; difference, 14.0% [95% CI, 11.2% to 16.8%]; P < .001), less failed CPR (110 [6.2%] vs 628 [22.4%]; difference, -16.2% [95% CI, -18.1% to -14.3%]; P < .001), less brain death (74 [4.1%] vs 261 [9.3%]; difference, -5.2% [95% CI, -6.6% to -3.8%]; P < .001) and less active shortening of the dying process (17 [1.0%] vs 80 [2.9%]; difference, -1.9% [95% CI, -2.7% to -1.1%]; P < .001). Conclusions and Relevance Among patients who had treatment limitations or died in 22 European ICUs in 2015-2016, compared with data reported from the same ICUs in 1999-2000, limitations in life-prolonging therapies occurred significantly more frequently and death without limitations in life-prolonging therapies occurred significantly less frequently. These findings suggest a shift in end-of-life practices in European ICUs, but the study is limited in that it excluded patients who survived ICU hospitalization without treatment limitations

    Changes in End-of-Life Practices in European Intensive Care Units From 1999 to 2016

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    Importance: End-of-life decisions occur daily in intensive care units (ICUs) around the world, and these practices could change over time. Objective: To determine the changes in end-of-life practices in European ICUs after 16 years. Design, Setting, and Participants: Ethicus-2 was a prospective observational study of 22 European ICUs previously included in the Ethicus-1 study (1999-2000). During a self-selected continuous 6-month period at each ICU, consecutive patients who died or had any limitation of life-sustaining therapy from September 2015 until October 2016 were included. Patients were followed up until death or until 2 months after the first treatment limitation decision. Exposures: Comparison between the 1999-2000 cohort vs 2015-2016 cohort. Main Outcomes and Measures: End-of-life outcomes were classified into 5 mutually exclusive categories (withholding of life-prolonging therapy, withdrawing of life-prolonging therapy, active shortening of the dying process, failed cardiopulmonary resuscitation [CPR], brain death). The primary outcome was whether patients received any treatment limitations (withholding or withdrawing of life-prolonging therapy or shortening of the dying process). Outcomes were determined by senior intensivists. Results: Of 13 625 patients admitted to participating ICUs during the 2015-2016 study period, 1785 (13.1%) died or had limitations of life-prolonging therapies and were included in the study. Compared with the patients included in the 1999-2000 cohort (n = 2807), the patients in 2015-2016 cohort were significantly older (median age, 70 years [interquartile range {IQR}, 59-79] vs 67 years [IQR, 54-75]; P < .001) and the proportion of female patients was similar (39.6% vs 38.7%; P = .58). Significantly more treatment limitations occurred in the 2015-2016 cohort compared with the 1999-2000 cohort (1601 [89.7%] vs 1918 [68.3%]; difference, 21.4% [95% CI, 19.2% to 23.6%]; P < .001), with more withholding of life-prolonging therapy (892 [50.0%] vs 1143 [40.7%]; difference, 9.3% [95% CI, 6.4% to 12.3%]; P < .001), more withdrawing of life-prolonging therapy (692 [38.8%] vs 695 [24.8%]; difference, 14.0% [95% CI, 11.2% to 16.8%]; P < .001), less failed CPR (110 [6.2%] vs 628 [22.4%]; difference, -16.2% [95% CI, -18.1% to -14.3%]; P < .001), less brain death (74 [4.1%] vs 261 [9.3%]; difference, -5.2% [95% CI, -6.6% to -3.8%]; P < .001) and less active shortening of the dying process (17 [1.0%] vs 80 [2.9%]; difference, -1.9% [95% CI, -2.7% to -1.1%]; P < .001). Conclusions and Relevance: Among patients who had treatment limitations or died in 22 European ICUs in 2015-2016, compared with data reported from the same ICUs in 1999-2000, limitations in life-prolonging therapies occurred significantly more frequently and death without limitations in life-prolonging therapies occurred significantly less frequently. These findings suggest a shift in end-of-life practices in European ICUs, but the study is limited in that it excluded patients who survived ICU hospitalization without treatment limitations.status: publishe
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