6,252 research outputs found

    Recent Advances in Chromospheric and Coronal Polarization Diagnostics

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    I review some recent advances in methods to diagnose polarized radiation with which we may hope to explore the magnetism of the solar chromosphere and corona. These methods are based on the remarkable signatures that the radiatively induced quantum coherences produce in the emergent spectral line polarization and on the joint action of the Hanle and Zeeman effects. Some applications to spicules, prominences, active region filaments, emerging flux regions and the quiet chromosphere are discussed.Comment: Review paper to appear in "Magnetic Coupling between the Interior and the Atmosphere of the Sun", eds. S. S. Hasan and R. J. Rutten, Astrophysics and Space Science Proceedings, Springer-Verlag, 200

    Metallochaperones Are Needed for Mycobacterium tuberculosis and Escherichia coli Nicotinamidase-Pyrazinamidase Activity.

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    Mycobacterium tuberculosis nicotinamidase-pyrazinamidase (PZAse) is a metalloenzyme that catalyzes conversion of nicotinamide-pyrazinamide to nicotinic acid-pyrazinoic acid. This study investigated whether a metallochaperone is required for optimal PZAse activity. M. tuberculosis and Escherichia coli PZAses (PZAse-MT and PZAse-EC, respectively) were inactivated by metal depletion (giving PZAse-MT-Apo and PZAse-EC-Apo). Reactivation with the E. coli metallochaperone ZnuA or Rv2059 (the M. tuberculosis analog) was measured. This was repeated following proteolytic and thermal treatment of ZnuA and Rv2059. The CDC1551 M. tuberculosis reference strain had the Rv2059 coding gene knocked out, and PZA susceptibility and the pyrazinoic acid (POA) efflux rate were measured. ZnuA (200 ΌM) achieved 65% PZAse-EC-Apo reactivation. Rv2059 (1 ΌM) and ZnuA (1 ΌM) achieved 69% and 34.3% PZAse-MT-Apo reactivation, respectively. Proteolytic treatment of ZnuA and Rv2059 and application of three (but not one) thermal shocks to ZnuA significantly reduced the capacity to reactivate PZAse-MT-Apo. An M. tuberculosis Rv2059 knockout strain was Wayne positive and susceptible to PZA and did not have a significantly different POA efflux rate than the reference strain, although a trend toward a lower efflux rate was observed after knockout. The metallochaperone Rv2059 restored the activity of metal-depleted PZAse in vitro Although Rv2059 is important in vitro, it seems to have a smaller effect on PZA susceptibility in vivo. It may be important to mechanisms of action and resistance to pyrazinamide in M. tuberculosis Further studies are needed for confirmation.IMPORTANCE Tuberculosis is an infectious disease caused by the bacterium Mycobacterium tuberculosis and remains one of the major causes of disease and death worldwide. Pyrazinamide is a key drug used in the treatment of tuberculosis, yet its mechanism of action is not fully understood, and testing strains of M. tuberculosis for pyrazinamide resistance is not easy with the tools that are presently available. The significance of the present research is that a metallochaperone-like protein may be crucial to pyrazinamide's mechanisms of action and of resistance. This may support the development of improved tools to detect pyrazinamide resistance, which would have significant implications for the clinical management of patients with tuberculosis: drug regimens that are appropriately tailored to the resistance profile of a patient's individual strain lead to better clinical outcomes, reduced onward transmission of infection, and reduction of the development of resistant strains that are more challenging and expensive to treat

    Caracterização, classificação, potencialidades e restriçÔes agrícolas de solos em Chapadinha-MA.

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    O assentamento Malhada do Meio, localizado em Chapadinha-MA, possui uma ĂĄrea de 630,86 ha, a vegetação Ă© de Floresta Estacional Decidual Submontana e Savana EstĂ©pica. O relevo Ă© ondulado e plano, com altitude mĂ©dia de 67 m. A geologia Ă© formada por arenitos finos argilosos da Formação Itapecuru e DepĂłsitos Aluvionares e Coluvionares. Objetivou-se neste trabalho caracterizar, classificar e avaliar as potencialidades e as restriçÔes agrĂ­colas dos solos do assentamento de reforma agrĂĄria Malhada do Meio, localizado no municĂ­pio de Chapadinha-MA. Foram abertos quatro perfis em pontos distintos da paisagem. Amostras foram coletadas para a realização das anĂĄlises de caracterização quĂ­micas e granulomĂ©trica. Os solos estudados foram classificados no Sistema Brasileiro de Classificação de Solos como Plintossolo PĂ©trico ConcrecionĂĄrio ĂȘndico latossĂłlico, Plintossolo ArgilĂșvico DistrĂłfico abrĂșptico gleissĂłlico, Neossolo FlĂșvico e Gleissolo HĂĄplico Tb DistrĂłfico cambissĂłlico. As limitaçÔes agrĂ­colas entre os solos estudados (baixa fertilidade, drenagem deficiente, impedimentos Ă  mecanização e ao desenvolvimento das raĂ­zes) podem restringir a produtividade das culturas agrĂ­colas

    Effects of pesticides used in soybean crops to the egg parasitoid Trichogramma pretiosum.

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    ABSTRACT: This research aimed to study the effects of different insecticides, herbicides and fungicides on eggs, larvae and pupae of Trichogramma pretiosum. The results showed that studied pesticides had different impact on T. pretiosum. Esfenvalerate 7.5 and spinosad 24.0 grams ha-1 were classified as harmfull (class 4) while clorfluazuron 10.0, methoxyfenozide 19.2, lactofen 165.0, fomesafen 250.0, fluazifop 125.0, glyphosate 960.0 (GlizÂź and Roundup TransorbÂź), azoxistrobin + ciproconazol 60.0 + 24.0, azoxistrobin 50.0 and myclobutanil 125.0 grams ha-1 were chemicals classified as harmless to all imature T. pretiosum stages. All the other chemicals evaluated had different impact on T. pretiosum being classified from harmless (class 1) to harmful (class 4) varying the impact accordingly to the different parasitoid stage. Then, less noxious products should be chosen whenever possible to be used in a soybean IPM program. RESUMO: Este trabalho teve como objetivo estudar os efeitos de diferentes inseticidas, herbicidas e fungicidas em ovos, larvas e pupas de Trichogramma pretiosum. Os resultados mostraram que os pesticidas estudados tiveram efeitos diferentes sobre T. pretiosum. Esfenvalerato 7,5 e espinosade 24,0 gramas ha-1 foram classificados como nocivos (classe 4), enquanto que clorfluazurom 10,0, metoxifenozida 19,2, lactofem 165,0, fomesafem 250,0, fluazifope 125,0, glifosato 960,0 (GlizÂź e Roundup TransorbÂź), azoxistrobina + ciproconazole 60,0 + 24,0, azoxistrobina 50,0 e miclobutanil 125,0 gramas ha-1 foram classificados como seletivos (classe 1) para todas as fases imaturas de T. pretiosum. Todos os demais agroquĂ­micos avaliados tiveram diferentes efeitos em T. pretiosum, sendo classificados de seletivo (classe 1) a nocivo (classe 4), variando o impacto de acordo com as diferentes fases do parasitĂłide. Portanto, produtos menos nocivos aos inimigos naturais devem ser escolhidos, sempre que possĂ­vel, para serem usados em um programa de MIP-soja

    Interação de locais e capacidades combinatórias de linhagens de milho em cruzamento dialélicos.

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    Neste trabalho foram utilizados 45 hibridos simples provenientes de cruzamentos dialelicos entre 10 linhagens de milho considerados de elite pelo Centro Nacional de Pesquisa de Milho e Sorgo. Esses hibridos foram estudados em ensaios em blocos casualizados, com quatro repeticoes, e instalados em dois municipios (locais) do estado de Minas Gerais (Sete Lagoas e Capinopolis), no ano agricola de 1976/77. Foi analisado apenas a producao de graos por parcela. Esses ensaios foram analisados individualmente e de forma conjunta. Com a finalidade de verificar a influencia dos locais sobre os parametros geneticos, testou-se a interacao das capacidades combinatorias com locais. Esse estudo indicou maior inconsistencia da capacidade geral de combinacao em ambientes diferentes, quando comparados com a capacidade especifica de combinacao

    Biological characteristics and parasitism capacity of Trichogramma pretiosum Riley (Hymenoptera, Trichogrammatidae) on eggs of Spodoptera frugiperda (J. E. Smith) (Lepidoptera, Noctuidae).

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    ABSTRACT. Biological characteristics and parasitism capacity of Trichogramma pretiosum Riley (Hymenoptera, Trichogrammatidae) on eggs of Spodoptera frugiperda (J. E. Smith) (Lepidoptera, Noctuidae). This study aimed at evaluating the biological characteristics and the capacity of parasitism of a Trichogramma pretiosum Riley, 1869 (Hymenoptera, trichogrammatidae) strain (T. pretiosum RV) collected in Rio Verde County, State of GoiĂĄs, Brazil. The study was carried out on eggs of Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera, Noctuidae) and conducted under controlled environmental conditions at different constant temperatures. The biological parameters determined were: developmental time (egg-adult; days); emergence (%); sex ratio; number of progeny/egg; number of generation/year; thermal constant (K); temperature threshold (Tb); daily number of parasitized eggs; cumulative parasitism (%); total number of eggs parasitized by T. pretiosum; and female longevity. To study the T. pretiosum parasitism capacity, 20 S. frugiperda eggs (? 24 h old) were placed into 8.0 cm x 2.0 cm glass vials containing one female (? 24 h old) each. Trials were carried out in a completely randomized experimental design, with 20 replications at each temperature. The environmental chambers (BOD type) were set at 18ÂșC, 20o C, 22o C, 25o C, 28o C and 32o C ± 1o C, 70 ±10% relative humidity, and 14/10 h (L:D) photoperiod. The eggs of S. frugiperda were replaced daily until parasitoid death. Results have shown an inverse correlation between developmental time and temperature, with statistically significant differences among means, except at 25ÂșC and 28ÂșC (10 days). Parasitoid emergence (%) was also influenced by temperature. The lowest percent emergence was observed at 32ÂșC, and the highest ones at 18ÂșC and 20ÂșC temperatures. The temperature did not affect T. pretiosum sex ratio and number of parasitoids per egg, thus allowing changes in the temperature to control insect mass production in the laboratory to meet the needs for field releases. RESUMO: CaracterĂ­sticas biolĂłgicas e capacidade de parasitismo de Trichogramma pretiosum Riley (Hymenoptera, Trichogrammatidae) em ovos de Spodoptera frugiperda (J. E. Smith) (LepidĂłptera, Noctuidae). O objetivo deste estudo foi avaliar as caracterĂ­sticas biolĂłgicas e a capacidade de parasitismo de uma linhagem de Trichogramma pretiosum Riley, 1869 (Hymenoptera, Trichogrammatidae), coletada em Rio Verde, GoiĂĄs, Brasil (T. pretiosum RV). O estudo foi feito com ovos de Spodoptera frugiperda (J. E. Smith) (LepidĂłptera, Noctuidae) e conduzido sob condiçÔes ambientais controladas e em diferentes temperaturas constantes. Os parĂąmetros biolĂłgicos determinados foram: perĂ­odo de desenvolvimento (ovo-adulto; dias); emergĂȘncia (%); razĂŁo sexual; nĂșmero de progĂȘnie/ovo; nĂșmero de geraçÔes/ano; constante tĂ©rmica (K); temperatura base (Tb); nĂșmero de ovos parasitados diariamente; parasitismo acumulado (%); nĂșmero total de ovos parasitados por fĂȘmea de T. pretiosum; e longevidade das fĂȘmeas. Para estudar a capacidade de parasitismo de T. pretiosum, 20 ovos de S. frugiperda (? 24 h de idade) foram colocados em tubos de vidro (8,0 x 2,0 cm) contendo uma fĂȘmea (? 24 h de idade) cada. Os experimentos foram conduzidos em delineamento experimental inteiramente casualizado, com 20 repetiçÔes por temperatura. As BODs foram reguladas para temperaturas constantes de 18ÂșC, 20oC, 22oC, 25oC, 28oC e 32oC, umidade relativa de 70 ±10% e fotoperĂ­odo de 14/10 h (L:E). Os ovos de S. frugiperda foram substituĂ­dos diariamente atĂ© a morte do parasitĂłide. Os resultados mostraram uma relação inversa entre o tempo de desenvolvimento e a temperatura, com mĂ©dias apresentado diferenças estatisticamente significativas entre si, com exceção das temperaturas de 25ÂșC e 28oC (10 dias). A emergĂȘncia do parasitĂłide (%) tambĂ©m foi influenciada pela temperatura. A menor porcentagem de emergĂȘncia foi observada a 32oC e a maior nas temperaturas de 18ÂșC e 20oC. A temperatura nĂŁo alterou a razĂŁo sexual nem o nĂșmero de parasitĂłides por ovo, permitindo mudanças na temperatura para controlar a produção de insetos em laboratĂłrio, com o fim de atender Ă s necessidades das liberaçÔes no campo

    Lepidopteran larva consumption of soybean foliage: basis for developing multiple-species economic thresholds for pest management decisions.

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    BACKGROUND: Defoliation by Anticarsia gemmatalis (H š ubner), Pseudoplusia includens (Walker), Spodoptera eridania (Cramer), S. cosmioides (Walker) and S. frugiperda (JE Smith) (Lepidoptera: Noctuidae) was evaluated in four soybean genotypes. A multiple-species economic threshold (ET), based upon the species? feeding capacity, is proposed with the aim of improving growers? management decisions on when to initiate control measures for the species complex. RESULTS: Consumption by A. gemmatalis, S. cosmioides or S. eridania on different genotypes was similar. The highest consumption of P. includens was 92.7 cm2 on Codetec 219RR; that of S. frugiperda was 118 cm2 on Codetec 219RR and 115.1 cm2 on MSoy 8787RR. The insect injury equivalent for S. cosmoides, calculated on the basis of insect consumption, was double the standard consumption by A. gemmatalis, and statistically different from the other species tested, which were similar to each other. CONCLUSIONS: As S. cosmioides always defoliated nearly twice the leaf area of the other species, the injury equivalent would be 2 for this lepidopteran species and 1 for the other species. The recommended multiple-species ET to trigger the beginning of insect control would then be 20 insect equivalents per linear metre

    Bunge’s Mathematical Structuralism Is Not a Fiction

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    In this paper, I explore Bunge’s fictionism in philosophy of mathematics. After an overview of Bunge’s views, in particular his mathematical structuralism, I argue that the comparison between mathematical objects and fictions ultimately fails. I then sketch a different ontology for mathematics, based on Thomasson’s metaphysical work. I conclude that mathematics deserves its own ontology, and that, in the end, much work remains to be done to clarify the various forms of dependence that are involved in mathematical knowledge, in particular its dependence on mental/brain states and material objects
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