5,599 research outputs found

    Retired galaxies: not to be forgotten in the quest of the star formation -- AGN connection

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    We propose a fresh look at the Main Galaxy Sample of the Sloan Digital Sky Survey by packing the galaxies in stellar mass and redshift bins. We show how important it is to consider the emission-line equivalent widths, in addition to the commonly used emission-line ratios, to properly identify retired galaxies (i.e. galaxies that have stopped forming stars and are ionized by their old stellar populations) and not mistake them for galaxies with low-level nuclear activity. We find that the proportion of star-forming galaxies decreases with decreasing redshift in each mass bin, while that of retired galaxies increases. Galaxies with M>1011.5MM_\star > 10^{11.5} M_\odot have formed all their stars at redshift larger than 0.4. The population of AGN hosts is never dominant for galaxy masses larger than 1010M10^{10} M_\odot. We warn about the effects of stacking galaxy spectra to discuss galaxy properties. We estimate the lifetimes of active galactic nuclei (AGN) relying entirely on demographic arguments --- i.e. without any assumption on the AGN radiative properties. We find upper-limit lifetimes of about 1--5 Gyr for detectable AGN in galaxies with masses between 101010^{10}--1012M10^{12} M_\odot. The lifetimes of the AGN-dominated phases are a few 10810^8 yr. Finally, we compare the star-formation histories of star-forming, AGN and retired galaxies as obtained by the spectral synthesis code STARLIGHT. Once the AGN is turned on it inhibits star formation for the next \sim 0.1 Gyr in galaxies with masses around 1010M10^{10} M_\odot, \sim 1 Gyr in galaxies with masses around 1011M10^{11} M_\odot.Comment: accepted for MNRAS figure resolution has been degraded with respect to what will be published in MNRA

    Multiplicação in vitro de abacaxi ornamental (Ananas comosus).

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    O abacaxi ornamental Ananas comosus é uma espécie vegetal pertencente à família Bromeliaceae, de grande interesse para paisagistas e floricultores, a utilização da cultura de tecidos proporciona a obtenção de milhares de mudas a partir de uma gema em um pequeno espaço e em um intervalo de tempo relativamente curto.Titulo: Multiplicação [i.e. e enraizamento] in vitro de abacaxi ornamental (Ananas comosus)

    Multiplicação in vitro de duas cultivares de bananeira.

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    A banana, Musa spp., é uma das frutas mais consumidas no mundo e na maioria dos países tropicais, a micropropagação de ápices caulinares constitui-se em importante ferramenta para obtenção de mudas de banana com alto padrão de qualidade, bem como para clonagem em massa de genótipos-elites. O objetivo deste trabalho foi avaliar a eficiência da multiplicação in vitro de duas cultivares de bananeira (Caipira e Pioneira) em cinco subcultivos, em meio MS (Murashige & Skoog, 1962), suplementado com 30 g L-1 de sacarose, 3 g L-1 de gelrite, 2 mg L-1 de BAP e pH 5,8 em sala de crescimento a 25ºC ± 2ºC, com iluminação artificial com intensidade luminosa de 2000 lux e fotoperíodo de 16 horas. As cultivares Caipira e Pioneira apresentam taxas de multiplicação absoluta e acumulada similares. Contudo, a cultivar Caipira, em média, mostra taxas de multiplicação absoluta mais uniforme ao longo dos subcultivos. Em média, a eficiência da multiplicação, especialmente da cultivar Caipira, é crescente até o subcultivo 4

    Use of strategies to improve retention in primary care randomised trials: a qualitative study with in-depth interviews

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    Objective To explore the strategies used to improve retention in primary care randomised trials.<p></p> Design Qualitative in-depth interviews and thematic analysis.<p></p> Participants 29 UK primary care chief and principal investigators, trial managers and research nurses.<p></p> Methods In-depth face-to-face interviews.<p></p> Results Primary care researchers use incentive and communication strategies to improve retention in trials, but were unsure of their effect. Small monetary incentives were used to increase response to postal questionnaires. Non-monetary incentives were used although there was scepticism about the impact of these on retention. Nurses routinely used telephone communication to encourage participants to return for trial follow-up. Trial managers used first class post, shorter questionnaires and improved questionnaire designs with the aim of improving questionnaire response. Interviewees thought an open trial design could lead to biased results and were negative about using behavioural strategies to improve retention. There was consensus among the interviewees that effective communication and rapport with participants, participant altruism, respect for participant's time, flexibility of trial personnel and appointment schedules and trial information improve retention. Interviewees noted particular challenges with retention in mental health trials and those involving teenagers.<p></p> Conclusions The findings of this qualitative study have allowed us to reflect on research practice around retention and highlight a gap between such practice and current evidence. Interviewees describe acting from experience without evidence from the literature, which supports the use of small monetary incentives to improve the questionnaire response. No such evidence exists for non-monetary incentives or first class post, use of which may need reconsideration. An exploration of barriers and facilitators to retention in other research contexts may be justified.<p></p&gt

    Torsion Phenomenology at the LHC

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    We explore the potential of the CERN Large Hadron Collider (LHC) to test the dynamical torsion parameters. The form of the torsion action can be established from the requirements of consistency of effective quantum field theory. The most phenomenologically relevant part of the torsion tensor is dual to a massive axial vector field. This axial vector has geometric nature, that means it does not belong to any representation of the gauge group of the SM extension or GUT theory. At the same time, torsion should interact with all fermions, that opens the way for the phenomenological applications. We demonstrate that LHC collider can establish unique constraints on the interactions between fermions and torsion field considerably exceeding present experimental lower bounds on the torsion couplings and its mass. It is also shown how possible non-universal nature of torsion couplings due to the renormalization group running between the Planck and TeV energy scales can be tested via the combined analysis of Drell-Yan and ttˉt\bar{t} production processes

    Inhibition of the formation in vitro of putatively carcinogenic metabolites derived from S. Haematobium and O. Viverrini by Combination of Drugs with Antioxidants

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    Infections caused by Schistosoma haematobium and Opisthorchis viverrini are classified as carcinogenic. Although carcinogenesis might be a multifactorial process, it has been postulated that these helminth produce/excrete oxysterols and estrogen-like metabolites that might act as initiators of their infection-associated carcinogenesis. Current treatment and control of these infections rely on a single drug, praziquantel, that mainly targets the parasites and not the pathologies related to the infection including cancer. Thus, there is a need to search for novel therapeutic alternatives that might include combinations of drugs and drug repurposing. Based on these concepts, we propose a novel therapeutic strategy that combines drugs with molecule antioxidants. We evaluate the efficacy of a novel therapeutic strategy to prevent the formation of putative carcinogenic metabolites precursors and DNA adducts. Firstly, we used a methodology previously established to synthesize metabolites precursors and DNA adducts in the presence of CYP450. Then, we evaluated the inhibition of their formation induced by drugs and antioxidants alone or in combination. Drugs and resveratrol alone did not show a significant inhibitory effect while N-acetylcysteine inhibited the formation of most metabolite precursors and DNA adducts. Moreover, the combinations of classical drugs with antioxidants were more effective rather than compounds alone. This strategy might be a valuable tool to prevent the initiation of helminth infection-associated carcinogenesis.This work was financed by FEDER-Fundo Europeu de Desenvolvimento Regional funds through the COMPETE 2020-Operational Programme for Competitiveness and Internationalisation (POCI), Portugal 2020, and by Portuguese funds through FCT-Fundação para a Ciência e a Tecnologia, in the framework of the projects "Institute for Research and Innovation in Health Sciences" (POCI-01-0145-FEDER-007274). N.V. also acknowledges support from FCT and FEDER (European Union), award number IF/00092/2014/CP1255/CT0004. FUNDING TEXT 2: Funding: This work was financed by FEDER-Fundo Europeu de Desenvolvimento Regional funds through the COMPETE 2020-Operational Programme for Competitiveness and Internationalisation (POCI), Portugal 2020, and by Portuguese funds through FCT-Fundação para a Ciência e a Tecnologia, in the framework of the projects “Institute for Research and Innovation in Health Sciences” (POCI-01-0145-FEDER-007274). N.V. also acknowledges support from FCT and FEDER (European Union), award number IF/00092/2014/CP1255/CT0004

    Crossover from 2D to 3D in a weakly interacting Fermi gas

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    We have studied the transition from two to three dimensions in a low temperature weakly interacting 6^6Li Fermi gas. Below a critical atom number, N2DN_{2D}, only the lowest transverse vibrational state of a highly anisotropic oblate trapping potential is occupied and the gas is two-dimensional. Above N2DN_{2D} the Fermi gas enters the quasi-2D regime where shell structure associated with the filling of individual transverse oscillator states is apparent. This dimensional crossover is demonstrated through measurements of the cloud size and aspect ratio versus atom number.Comment: Replaced with published manuscrip
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