22 research outputs found

    ENCAPSULATION EFFICIENCY AND THERMAL STABILITY OF ORANGE ESSENTIAL OIL MICROENCAPSULATED BY SPRAY DRYING AND BY COACERVATION

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    Orange essential oil was microencapsulated by spray drying using maltodextrin and modified starch as carrier agents, and also by coacervation using sodium alginate. The influence of different microencapsulation methods and carriers on the microscopic and thermal characteristics of the product and on the encapsulation efficiency of the microparticles was investigated. According to a technique based on headspace extraction coupled to gas chromatography, the encapsulation efficiencies were above 99 % for both methods, and the oil was composed mainly of D-limonene (95.7 %) and mircene (1.66 %). Coacervation and spray drying produced microparticles of 908.63 μm and 1.02 μm, respectively, which increased the thermal stability of the oil. Nonetheless, the coacervated microparticles showed higher thermal stability and boiling point than the spray-dried ones

    Soil bulk density and biomass partitioning of Brachiaria decumbens in a silvopastoral system Densidade do solo e partição de biomassa de Brachiaria decumbens em um sistema silvopastoril

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    Shade in silvopastoral systems improves the thermal comfort of animals, but it may also affect the pasture productivity and can contribute to soil compaction in the shaded areas due to the increase in the number of animals looking for comfort. The effect of grazing at various distances from tree rows (under the tree canopy, at 6 and at 12 m away from the trees) on the soil bulk density and on the aerial and root biomass of Brachiaria decumbens was evaluated in both the dry and the rainy seasons. The study was carried out on an Orthic Ferralsol in a randomized block design with two replications. Tree rows were composed of Eucalyptus grandis and Acacia mangium species, and the paddocks were submitted to a rotational stocking management, using Holstein (Bos taurus) × Zebu (Bos indicus) heifers. The shade intensity in the pasture decreased with an increasing distance from the tree row. Soil bulk density did not vary with the distance from the tree row, but varied seasonally, being greater in the rainy season (1.47 g cm-3) than in the dry season (1.28 g cm-3). Green forage and root mass, expressed as dry matter, were lower under the tree canopy and were greater in the rainy season. There were decreases of 22.3 and 41.4% in the aerial and root biomasses, respectively, in the tree rows. The greatest shoot/root ratio for B. decumbens under moderate and intensive shading indicates a modification in the forage biomass allocation pattern that favours the aerial development in detriment of the root system.<br>O sombreamento em sistemas silvipastoris concorre para o conforto térmico dos animais; no entanto pode afetar a produção do pasto e contribuir para a compactação do solo, pelo aumento da concentração de animais nas áreas sombreadas. Avaliou-se o efeito da distância do renque de árvores (sob a copa das árvores, 6 e 12 m de distancia das árvores) na densidade do solo e na biomassa aérea e de raízes de Brachiaria decumbens, nas épocas seca e chuvosa. O estudo foi conduzido num Latossolo Vermelho-Amarelo no delineamento em blocos casualizados, com duas repetições. A faixa de árvores foi composta pelas espécies Eucalyptus grandis e Acacia mangium, e os piquetes foram manejados com novilhas Holandês (Bos taurus) × Zebu (Bos indicus) , sob lotação rotativa. A intensidade de sombreamento foi decrescente com o distanciamento do renque de árvores. A densidade do solo não variou com a distância do renque de árvores, mas sim com a época do ano, tendo sido maior na época chuvosa (1,47 g dm-3) do que na seca (1,28 g dm-3). As massas secas de forragem verde e de raízes foram menores sob a copa das árvores e maiores na época chuvosa do que na seca. Na faixa arborizada houve reduções de 22,3 e 41,4% na biomassa aérea e de raízes, respectivamente. A maior relação parte aérea/raiz da B. decumbens à sombra expressa uma modificação no padrão de alocação de biomassa na forrageira, que prioriza a formação da parte aérea, em detrimento do sistema radicular

    1100 days in the life of the supernova 2018ibb The best pair-instability supernova candidate, to date

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    Stars with zero-age main sequence masses between 140 and 260 M are thought to explode as pair-instability supernovae (PISNe). During their thermonuclear runaway, PISNe can produce up to several tens of solar masses of radioactive nickel, resulting in luminous transients similar to some superluminous supernovae (SLSNe). Yet, no unambiguous PISN has been discovered so far. SN 2018ibb is a hydrogen-poor SLSN at z = 0.166 that evolves extremely slowly compared to the hundreds of known SLSNe. Between mid 2018 and early 2022, we monitored its photometric and spectroscopic evolution from the UV to the near-infrared (NIR) with 2–10 m class telescopes. SN 2018ibb radiated &gt;3 × 1051 erg during its evolution, and its bolometric light curve reached &gt;2 × 1044 erg s−1 at its peak. The long-lasting rise of &gt;93 rest-frame days implies a long diffusion time, which requires a very high total ejected mass. The PISN mechanism naturally provides both the energy source (56Ni) and the long diffusion time. Theoretical models of PISNe make clear predictions as to their photometric and spectroscopic properties. SN 2018ibb complies with most tests on the light curves, nebular spectra and host galaxy, and potentially all tests with the interpretation we propose. Both the light curve and the spectra require 25–44 M of freshly nucleosynthesised 56Ni, pointing to the explosion of a metal-poor star with a helium core mass of 120–130 M at the time of death. This interpretation is also supported by the tentative detection of [Co ii] λ 1.025 µm, which has never been observed in any other PISN candidate or SLSN before. We observe a significant excess in the blue part of the optical spectrum during the nebular phase, which is in tension with predictions of existing PISN models. However, we have compelling observational evidence for an eruptive mass-loss episode of the progenitor of SN 2018ibb shortly before the explosion, and our dataset reveals that the interaction of the SN ejecta with this oxygen-rich circumstellar material contributed to the observed emission. That may explain this specific discrepancy with PISN models. Powering by a central engine, such as a magnetar or a black hole, can be excluded with high confidence. This makes SN 2018ibb by far the best candidate for being a PISN, to date.</p

    1100 days in the life of the supernova 2018ibb -- The best pair-instability supernova candidate, to date

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    International audienceAbridged - Stars with ZAMS masses between 140 and 260M⊙260 M_\odot are thought to explode as pair-instability supernovae (PISNe). During their thermonuclear runaway, PISNe can produce up to several tens of solar masses of radioactive nickel, resulting in luminous transients similar to some superluminous supernovae (SLSNe). Yet, no unambiguous PISN has been discovered so far. SN2018ibb is a H-poor SLSN at z=0.166z=0.166 that evolves extremely slowly compared to the hundreds of known SLSNe. Between mid 2018 and early 2022, we monitored its photometric and spectroscopic evolution from the UV to the NIR with 2-10m class telescopes. SN2018ibb radiated >3×1051erg>3\times10^{51} \rm erg during its evolution, and its bolometric light curve reached >2×1044erg s−1>2\times10^{44} \rm erg\,s^{-1} at peak. The long-lasting rise of >93>93 rest-frame days implies a long diffusion time, which requires a very high total ejected mass. The PISN mechanism naturally provides both the energy source (56^{56}Ni) and the long diffusion time. Theoretical models of PISNe make clear predictions for their photometric and spectroscopic properties. SN2018ibb complies with most tests on the light curves, nebular spectra and host galaxy, potentially all tests with the interpretation we propose. Both the light curve and the spectra require 25-44 M⊙M_\odot of freshly nucleosynthesised 56^{56}Ni, pointing to the explosion of a metal-poor star with a He-core mass of 120-130 M⊙M_\odot at the time of death. This interpretation is also supported by the tentative detection of [Co II]λ\lambda1.025μ\mum, which has never been observed in any other PISN candidate or SLSN before. Powering by a central engine, such as a magnetar or a black hole, can be excluded with high confidence. This makes SN2018ibb by far the best candidate for being a PISN, to date

    ATP-Diphosphohydrolases in Parasites: Localization, Functions and Recent Developments in Drug Discovery

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