305 research outputs found
Avaliação de características fenotípicas para a determinação do rendimento foliar em espinheira-santa (Maytenus ilicifolia Martius).
A espinheira-santa (Maytenus ilieifolia) é uma espécie medicinal arbórea, nativa das formações de Floresta Ombrófila Mista do sul do Brasil, a qual vem sofrendo grande pressão de exploração nos seus ambientes naturais. Este trabalho teve como objetivo caracterizar o rendimento de indivíduos de diferentes populações naturais de espinheira-santa, por meio de características fenotípicas não destrutivas, a fim de contribuir para o processo de manejo sustentável. Para fins de determinação do rendimento, foram avaliados o número de ramos primários com e sem folhas, a altura, o diâmetro a altura do colo (DAC) e a altura da primeira ramificação, em 60 indivíduos de espinheira-santa de duas populações naturais, com características distintas. Estimou-se coeficientes de corre/ação entre estes parâmetros, bem como equações de regressão entre e o número de ramos primários com folhas (X) e o rendimento (R). As equações R = 0,75205 • X, para populações que ocorrem a pleno sol, e R = 1,53459 • X, para populações que ocorrem no sub-bosque de formações secundárias, são de uso prático e capazes de representar com elevada precisão o rendimento em populações com essas características ambientais
Jet-Induced Nucleosynthesis in Misaligned Microquasars
The jet axes and the orbital planes of microquasar systems are usually
assumed to be approximately perpendicular, eventhough this is not currently an
observational requirement. On the contrary, in one of the few systems where the
relative orientations are well-constrained, V4641Sgr, the jet axis is known to
lie not more than ~36 degrees from the binary plane. Such a jet, lying close to
the binary plane, and traveling at a significant fraction of the speed of light
may periodically impact the secondary star initiating nuclear reactions on its
surface. The integrated yield of such nuclear reactions over the age of the
binary system (less the radiative mass loss) will detectably alter the
elemental abundances of the companion star. This scenario may explain the
anomalously high Li enhancements (roughly ~20-200 times the sun's photospheric
value; or, equivalently, 0.1-1 times the average solar system value) seen in
the companions of some black-hole X-ray binary systems. (Such enhancements are
puzzling since Li nuclei are exceedingly fragile - being easily destroyed in
the interiors of stars - and Li would be expected to be depleted rather than
enhanced there.) Gamma-ray line signatures of the proposed process could
include the 2.22 MeV neutron capture line as well as the 0.478 MeV 7Li*
de-excitation line, both of which may be discernable with the INTEGRAL
satellite if produced in an optically thin region during a large outburst. For
very energetic jets, a relatively narrow neutral pion gamma-decay signature at
67.5 MeV could also be measurable with the GLAST satellite. We argue that about
10-20% of all microquasar systems ought to be sufficiently misaligned as to be
undergoing the proposed jet-secondary impacts.Comment: ApJ, accepted. Includes referee's suggestions and some minor
clarifications over previous versio
Roteiro metodológico para conservação e uso sustentável da biodiversidade.
bitstream/CNPF-2009-09/42354/1/doc144.pdf1 CD-ROM
Conservação ambiental forte alcançada através de sistemas agroflorestais multiestratificados: 2 - restauração de paisagens degradadas por meio de agroflorestas.
Foi avaliada a sustentabilidade ambiental em nível da paisagem de práticas de sistemas agroflorestais multiestratificados na região do Vale do Ribeira, SP e PR, na escala da unidade de produção agrícola familiar, baseando-se nos resultados de várias pesquisas publicadas e em mapas georrefenciados de uso e ocupação do solo atual e histórico. As práticas da agrofloresta, através da indução de sucessão agroflorestal e da sucessão florestal secundária natural, resultam em uma paisagem produtiva sob intenso processo de restauração. Assim considera-se o ?land sharing? baseado em agroflorestas agroecológicas como uma promissora estratégia de conservação ambiental.Edição do 1º Seminário de Agroecologia da América do Sul; 5º Seminário de Agroecologia de Mato Grosso do Sul; 4º Encontro de Produtores Agroecológicos de Mato Grosso do Sul; 1º Seminário de Sistemas Agroflorestais em Bases Agroecológicas de Mato Grosso do Sul, 2014, Dourados, MS - AGROECOL
Conservação ambiental forte alcançada através de sistemas agroflorestais multiestratificados: 1 - agroflorestas e a restauração ecológica de florestas.
O objetivo deste trabalho foi verificar se um sistema agroflorestal multiestratificado (agrofloresta) agroecológico pode ser considerado como tendo uma sustentabilidade ambiental forte, com base em uma análise dos serviços ecossistêmicos de restauração florestal. Para tanto, foi utilizado resultados de pesquisas que compararam agroflorestas e regenerações naturais. Os resultados sugerem que as agroflorestas apresentam uma sustentabilidade ambiental forte e potencial de promover a restauração florestal, no entanto, é um sistema produtivo e não uma metodologia de restauração. Este fato, ao mesmo tempo em que impõe desafios legais e conceituais, aponta para uma alternativa de restauração para as florestas brasileiras.Edição do 1º Seminário de Agroecologia da América do Sul; 5º Seminário de Agroecologia de Mato Grosso do Sul; 4º Encontro de Produtores Agroecológicos de Mato Grosso do Sul; 1º Seminário de Sistemas Agroflorestais em Bases Agroecológicas de Mato Grosso do Sul, 2014, Dourados, MS - AGROECOL
Atomic Diffusion and Mixing in Old Stars I. VLT/FLAMES-UVES Observations of Stars in NGC 6397
We present a homogeneous photometric and spectroscopic analysis of 18 stars
along the evolutionary sequence of the metal-poor globular cluster NGC 6397
([Fe/H] = -2), from the main-sequence turnoff point to red giants below the
bump. The spectroscopic stellar parameters, in particular stellar-parameter
differences between groups of stars, are in good agreement with broad-band and
Stroemgren photometry calibrated on the infrared-flux method. The spectroscopic
abundance analysis reveals, for the first time, systematic trends of iron
abundance with evolutionary stage. Iron is found to be 31% less abundant in the
turnoff-point stars than in the red giants. An abundance difference in lithium
is seen between the turnoff-point and warm subgiant stars. The impact of
potential systematic errors on these abundance trends (stellar parameters, the
hydrostatic and LTE approximations) is quantitatively evaluated and found not
to alter our conclusions significantly. Trends for various elements (Li, Mg,
Ca, Ti and Fe) are compared with stellar-structure models including the effects
of atomic diffusion and radiative acceleration. Such models are found to
describe the observed element-specific trends well, if extra (turbulent) mixing
just below the convection zone is introduced. It is concluded that atomic
diffusion and turbulent mixing are largely responsible for the sub-primordial
stellar lithium abundances of warm halo stars. Other consequences of atomic
diffusion in old metal-poor stars are also discussed.Comment: 20 pages (emulateapj), 11 figures, accepted for publication in Ap
Increased fibrosis in a mouse model of anti-laminin 332 mucous membrane pemphigoid remains unaltered by inhibition of aldehyde dehydrogenase
Mucous membrane pemphigoid (MMP) is an autoimmune blistering disease characterized by autoantibodies against the basal membrane zone of skin and surface-close epithelia and predominant mucosal lesions. The oral cavity and conjunctivae are most frequently affected, albeit clinical manifestations can also occur on the skin. MMP-associated lesions outside the oral cavity typically lead to scarring. Mechanisms underlying scarring are largely unknown in MMP and effective treatment options are limited. Herein, we assessed the collagen architecture in tissue samples of an antibody-transfer mouse model of anti-laminin-332 MMP. In MMP mice, increased collagen fibril density was observed in skin and conjunctival lesions compared to mice injected with normal rabbit IgG. The extracellular matrix of MMP skin samples also showed altered post-translational collagen cross-linking with increased levels of both lysine- and hydroxylysine-derived collagen crosslinks supporting the fibrotic phenotype in experimental MMP compared to control animals. In addition, we evaluated a potential anti-fibrotic therapy in experimental anti-laminin-332 MMP using disulfiram, an inhibitor of the aldehyde dehydrogenase (ALDH), which has been implicated in immune-mediated mucosal scarring. In addition, disulfiram also acts as a copper chelator that was shown to block lysyl oxidase activity, an enzyme involved in formation of collagen crosslinks. Topical use of disulfiram (300 μM in 2 [w/v] methocel) did not improve ocular lesions in experimental MMP over the 12-day treatment period in disulfiram-treated mice compared to vehicle-treated mice (n=8/group). Furthermore, C57BL6/J mice (n=8/group) were treated prophylactically with 200 mg/kg p.o. disulfiram or the solvent once daily over a period of 12 days. Systemic treatment did not show any reduction in the severity of oral and ocular lesions in MMP mice, albeit some improvement in skin lesions was observed in disulfiram- vs. vehicle-treated mice (p=0.052). No reduction in fibrosis was seen, as assessed by immunohistochemistry. Whilst blocking of ALDH failed to significantly ameliorate disease activity, our data provide new insight into fibrotic processes highlighting changes in the collagenous matrix and cross-linking patterns in IgG-mediated MMP
Center-to-Limb Variation of Solar Line Profiles as a Test of NLTE Line Formation Calculations
We present new observations of the center-to-limb variation of spectral lines
in the quiet Sun. Our long-slit spectra are corrected for scattered light,
which amounts to 4-8 % of the continuum intensity, by comparison with a Fourier
transform spectrum of the disk center. We examine the effect of inelastic
collisions with neutral hydrogen in NLTE line formation calculations of the
oxygen infrared triplet, and the Na I 6160.8 A line. Adopting a classical
one-dimensional theoretical model atmosphere, we find that the sodium
transition, formed in higher layers, is much more effectively thermalized by
hydrogen collisions than the high-excitation oxygen lines. This result appears
as a simple consequence of the decrease of the ratio NH/Ne with depth in the
solar photosphere. The center-to-limb variation of the selected lines is
studied both under LTE and NLTE conditions. In the NLTE analysis, inelastic
collisions with hydrogen atoms are considered with a simple approximation or
neglected, in an attempt to test the validity of such approximation. For the
sodium line studied, the best agreement between theory and observation happens
when NLTE is considered and inelastic collisions with hydrogen are neglected in
the rate equations. The analysis of the oxygen triplet benefits from a very
detailed calculation using an LTE three-dimensional model atmosphere and NLTE
line formation. The chi**2 statistics favors including hydrogen collisions with
the approximation adopted, but the oxygen abundance derived in that case is
significantly higher than the value derived from OH infrared transitions.Comment: 10 pages, 8 figures, to appear in A&
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