2,793 research outputs found
The African hind's (Cephalopholis taeniops, serranidae) use of artificial reefs off Sal Island (Cape Verde): a preliminary study based on acoustic telemetry
The African hind Cephalopholis taeniops (Valenciennes, 1828) is one of the most important commercial demersal species caught in the Cape Verde archipelago. The species is closely associated with hard substrate and is one of the main attractions for SCUBA divers. In January 2006 a former Soviet fishing vessel - the Kwarcit - was sunk off Santa Maria Bay (Sal Island). Young C. taeniops are commonly observed in this artificial reef (AR). In order to investigate the species' use of the AR, 4 specimens were captured and surgically implanted underwater with Vemco brand acoustic transmitters. The fish were monitored daily with an active telemetry receiver for one week after release. Simultaneously, an array of 3 passive VR2 / VR2W receivers was set for 63 days, registering data that allowed an analysis of spatial, daily and short term temporal activity patterns. The results showed site fidelity to the AR, with no migrations to the nearby natural reef. The method used allowed to register a consistent higher activity during daytime and a preference for the area opposite the dominant current
Modified Gravity on the Brane and Dark Energy
We analyze the dynamics of an AdS5 braneworld with matter fields when gravity
is allowed to deviate from the Einstein form on the brane. We consider exact
5-dimensional warped solutions which are associated with conformal bulk fields
of weight -4 and describe on the brane the following three dynamics: those of
inhomogeneous dust, of generalized dark radiation, and of homogeneous
polytropic dark energy. We show that, with modified gravity on the brane, the
existence of such dynamical geometries requires the presence of non-conformal
matter fields confined to the brane.Comment: Revised version published in Gen. Rel. Grav. Typos corrected, updated
reference and some remarks added for clarity. 11 pages, latex, no figure
Atividade inseticida de estirpes de Bacillus thuringiensis em pragas da soja e do girassol.
O controle biolĂłgico como tĂĄtica de manejo integrado de pragas Ă© promissor devido a sua seletividade e sustentabilidade, pois Ă© realizado por diferentes organismos como os insetos parasitĂłides, predadores e patĂłgenos, destacando-se as bactĂ©rias. O presente estudo teve como objetivo avaliar cepas de Bacillus thuringiensis com mortalidade para Spodoptera frugiperda Spodoptera eridania, Spodoptera cosmioides, Chlosyne lacinia saundersii Anticarsia gemmatalis e Pseudoplusia includens. Utilizou-se lagartas de 2° instar e como padrĂŁo de comparação a estirpe HD-1 de B. thuringiensis subsp. Kurstaki. Cubos de dieta e pedaços de folhas de girassol e milho foram mergulhados na suspensĂŁo das culturas liofilizadas com a concentração desejada para a porcentagem de mortalidade e determinação da CL50. Constatou-se 80% de mortalidade em uma Ășnica espĂ©cie ou para mais de uma espĂ©cie em 21 estirpes. Destacaram-se a Br37, S1450 e HD-1, que causaram mortalidade acima de 80% para todas as espĂ©cies testadas. Br78 e S1265, provocaram mortalidade, acima de 82%, nas espĂ©cies de S. frugiperda S. eridania, A. gemmatalis e P. includens. O padrĂŁo HD-1 apresentou-se virulento para todas as espĂ©cies testadas. A CL50 de BR37, BR58 e BR94, variou entre 46,66 ?g de liofilizado/ml e 63,33 ?g/ml para S. eridania, entre 40,00 ?g/ml e 116,66 ?g/ml para S. frugiperda. Das 6 cepas de B. thuringiensis testadas para A.gemmatalis a CL50 variou entre 15,03 ?g/ml a 118,93 ?g/ml. Em C. l. saundersii a variação da CL50 ficou entre 6,54 ?g/ml e 57,77 ?g/ml. Em comparação com o padrĂŁo HD-1 a estirpe BR58 para S. eridania manteve a toxicidade, e para S. frugiperda e A. gemmatalis foi de uma vez maior do que em relação ao padrĂŁo. Para BR87, S1302, S1269 testadas em C.l. saundersii a toxicidade foi 3,0 vezes maior quando comparada ao padrĂŁo HD-1. Os resultados foram satisfatĂłrios observando o potencial de 4 cepas para o controle das espĂ©cies acima citadas.SICONBIOL 2011
Critical droplets in Metastable States of Probabilistic Cellular Automata
We consider the problem of metastability in a probabilistic cellular
automaton (PCA) with a parallel updating rule which is reversible with respect
to a Gibbs measure. The dynamical rules contain two parameters and
which resemble, but are not identical to, the inverse temperature and external
magnetic field in a ferromagnetic Ising model; in particular, the phase diagram
of the system has two stable phases when is large enough and is
zero, and a unique phase when is nonzero. When the system evolves, at small
positive values of , from an initial state with all spins down, the PCA
dynamics give rise to a transition from a metastable to a stable phase when a
droplet of the favored phase inside the metastable phase reaches a
critical size. We give heuristic arguments to estimate the critical size in the
limit of zero ``temperature'' (), as well as estimates of the
time required for the formation of such a droplet in a finite system. Monte
Carlo simulations give results in good agreement with the theoretical
predictions.Comment: 5 LaTeX picture
Chemoselective Installation of Amine Bonds on Proteins through Aza-Michael Ligation.
Chemical modification of proteins is essential for a variety of important diagnostic and therapeutic applications. Many strategies developed to date lack chemo- and regioselectivity as well as result in non-native linkages that may suffer from instability in vivo and adversely affect the protein's structure and function. We describe here the reaction of N-nucleophiles with the amino acid dehydroalanine (Dha) in a protein context. When Dha is chemically installed in proteins, the addition of a wide-range N-nucleophiles enables the rapid formation of amine linkages (secondary and tertiary) in a chemoselective manner under mild, biocompatible conditions. These new linkages are stable at a wide range of pH values (pH 2.8 to 12.8), under reducing conditions (biological thiols such as glutathione) and in human plasma. This method is demonstrated for three proteins and is shown to be fully compatible with disulfide bridges, as evidenced by the selective modification of recombinant albumin that displays 17 structurally relevant disulfides. The practicability and utility of our approach is further demonstrated by the construction of a chemically modified C2A domain of Synaptotagmin-I protein that retains its ability to preferentially bind to apoptotic cells at a level comparable to the native protein. Importantly, the method was useful for building a homogeneous antibody-drug conjugate with a precise drug-to-antibody ratio of 2. The kinase inhibitor crizotinib was directly conjugated to Dha through its piperidine motif, and its antibody-mediated intracellular delivery results in 10-fold improvement of its cancer cell-killing efficacy. The simplicity and exquisite site-selectivity of the aza-Michael ligation described herein allows the construction of stable secondary and tertiary amine-linked protein conjugates without affecting the structure and function of biologically relevant proteins
Cellular localization, accumulation and trafficking of double-walled carbon nanotubes in human prostate cancer cells
Carbon nanotubes (CNTs) are at present being considered as potential nanovectors with the ability to deliver therapeutic cargoes into living cells. Previous studies established the ability of CNTs to enter cells and their therapeutic utility, but an appreciation of global intracellular trafficking associated with their cellular distribution has yet to be described. Despite the many aspects of the uptake mechanism of CNTs being studied, only a few studies have investigated internalization and fate of CNTs inside cells in detail. In the present study, intracellular localization and trafficking of RNA-wrapped, oxidized double-walled CNTs (oxDWNTâRNA) is presented. Fixed cells, previously exposed to oxDWNTâRNA, were subjected to immunocytochemical analysis using antibodies specific to proteins implicated in endocytosis; moreover cell compartment markers and pharmacological inhibitory conditions were also employed in this study. Our results revealed that an endocytic pathway is involved in the internalization of oxDWNTâRNA. The nanotubes were found in clathrin-coated vesicles, after which they appear to be sorted in early endosomes, followed by vesicular maturation, become located in lysosomes. Furthermore, we observed co-localization of oxDWNTâRNA with the small GTP-binding protein (Rab 11), involved in their recycling back to the plasma membrane via endosomes from the trans-golgi network
Scalar kinks and fermion localisation in warped spacetimes
Scalar kinks propagating along the bulk in warped spacetimes provide a thick
brane realisation of the braneworld. We consider here, a class of such exact
solutions of the full Einstein-scalar system with a sine-Gordon potential and a
negative cosmological constant. In the background of the kink and the
corresponding warped geometry, we discuss the issue of localisation of spin
half fermions (with emphasis on massive ones) on the brane in the presence of
different types of kink-fermion Yukawa couplings. We analyse the possibility of
quasi-bound states for large values of the Yukawa coupling parameter
(with , the warp factor parameter kept fixed) using appropriate, recently
developed, approximation methods. In particular, the spectrum of the low--lying
states and their lifetimes are obtained, with the latter being exponentially
enhanced for large . Our results indicate quantitatively, within
this model, that it is possible to tune the nature of warping and the strength
and form of the Yukawa interaction to obtain trapped massive fermion states on
the brane, which, however, do have a finite (but very small) probability of
escaping into the bulk.Comment: 22 pages, 4 figures, RevTex
Atividade bacteriostĂĄtica dos extratos brutos de Penicillium amapaense e Penicillium labradorum.
Do ponto de vista clĂnico, compostos antimicrobianos que possuem atividade bacteriostĂĄtica sĂŁo interessantes devido ao seu amplo espectro, estas molĂ©culas inibem o crescimento bacteriano e permitem ao sistema imunolĂłgico combatĂȘ-los com maior eficĂĄcia. Neste contexto, este estudo teve como objetivo a avaliação da atividade antibacteriana dos extratos brutos dos fungos P. amapaense (INPA-AP25) e P. labradorum (INPA-AP10) isolados de sedimentos do rio Amazonas
Extratos brutos de Penicillium amapaense e Penicillium labradorum no controle de patĂłgenos agrĂcolas.
Existe uma constante demanda pela identificação de novas molĂ©culas menos tĂłxicas e amigĂĄveis ambientalmente a serem utilizadas na agricultura, em virtude da resistĂȘncia adquirida pelos patĂłgenos. Uma alternativa Ă© o uso de fungos filamentosos, pois possuem uma ampla diversidade de metabĂłlitos secundĂĄrios (MS), com distintas atividades biolĂłgicas. O objetivo deste estudo foi avaliar a atividade antifĂșngica dos extratos de P. amapaense (INPA-AP25) e P. labradorum (INPA-AP10) isolados do rio Amazonas, contra fitopatĂłgenos de interesse agrĂcola
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