5,295 research outputs found
Bioprospecting endophytic bacteria for biological control of coffee leaf rust.
Supressão de doenças de plantas por microrganismos endofÃticos tem sido demonstrada em diversos patossistemas. Neste trabalho foram selecionados isolados de bactérias endofÃticas de folhas e ramos de cafeeiro com potencial para o controle biológico da ferrugem do cafeeiro, pois é conhecido que esses microrganismos podem possuir essa caracterÃstica. Bactérias endofÃticas isoladas previamente de folhas e ramos de Coffea arabica L e Coffea robusta L foram avaliadas quanto ao seu potencial de biocontrole da ferrugem do café causada pelo fungo Hemileia vastatrix Berk. & Br., raça 2. As bactérias foram testadas para a inibição da germinação de urediniosporos do fungo e em bioensaios para o controle do desenvolvimento da ferrugem alaranjada do cafeeiro em discos de folhas, folhas destacadas e mudas da cv. Mundo Novo. Os isolados de bactérias endofÃticas testados demonstraram eficácia na inibição da germinação de urediniosporos e/ou no desenvolvimento da ferrugem, com valores acima de 50%, embora os resultados obtidos nos testes de germinação de urediniosporos tenham sido inferiores ao tratamento com propiconazole (testemunha padrão). Nos testes em discos de folhas, folhas destacadas e em plantas de cafeeiro, os isolados endofÃticos TG4-Ia, TF2-IIc, TF9-Ia, TG11-IIa e TF7-IIa demonstraram melhor controle da ferrugem do cafeeiro. Os isolados endofÃticos TG4-Ia e TF9-Ia foram identificados como Bacillus lentimorbus Dutky e Bacillus cereus Frank. & Frank., respectivamente. De acordo com os resultados verifica-se que alguns isolados foram eficientes em controlar a ferrugem do cafeeiro, embora alguns tenham aumentado a severidade da doença. Apesar do número relativamente baixo de bactérias endofÃticas testadas, resultados promissores foram obtidos em relação ao controle biológico da ferrugem, sendo que esses poderão no futuro apresentar uma alternativa aos fungicidas
Atomic structure of dislocation kinks in silicon
We investigate the physics of the core reconstruction and associated
structural excitations (reconstruction defects and kinks) of dislocations in
silicon, using a linear-scaling density-matrix technique. The two predominant
dislocations (the 90-degree and 30-degree partials) are examined, focusing for
the 90-degree case on the single-period core reconstruction. In both cases, we
observe strongly reconstructed bonds at the dislocation cores, as suggested in
previous studies. As a consequence, relatively low formation energies and high
migration barriers are generally associated with reconstructed
(dangling-bond-free) kinks. Complexes formed of a kink plus a reconstruction
defect are found to be strongly bound in the 30-degree partial, while the
opposite is true in the case of 90-degree partial, where such complexes are
found to be only marginally stable at zero temperature with very low
dissociation barriers. For the 30-degree partial, our calculated formation
energies and migration barriers of kinks are seen to compare favorably with
experiment. Our results for the kink energies on the 90-degree partial are
consistent with a recently proposed alternative double-period structure for the
core of this dislocation.Comment: 12 pages, two-column style with 8 postscript figures embedded. Uses
REVTEX and epsf macros. Also available at
http://www.physics.rutgers.edu/~dhv/preprints/index.html#rn_di
Produção de plântulas in vitro a partir de diferentes explantes de sementes de camu-camu (Myrciaria dubia (H.B.K.) Mc vaugh).
Coulomb and nuclear breakup of B
The cross sections for the (B,Be-) breakup reaction on Ni
and Pb targets at the beam energies of 25.8 MeV and 415 MeV have been
calculated within a one-step prior-form distorted-wave Born approximation. The
relative contributions of Coulomb and nuclear breakup of dipole and quadrupole
multipolarities as well as their interference have been determined. The nuclear
breakup contributions are found to be substantial in the angular distributions
of the Be fragment for angles in the range of 30 - 80 at
25.8 MeV beam energy. The Coulomb-nuclear interference terms make the dipole
cross section larger than that of quadrupole even at this low beam energy.
However, at the incident energy of 415 MeV, these effects are almost negligible
in the angular distributions of the (Be-p) coincidence cross sections at
angles below 4.Comment: Revised version, accepted for publication in Phys. Rev.
Models of core reconstruction for the 90-degree partial dislocation in semiconductors
We compare the models that have been proposed in the literature for the
atomic structure of the 90-degree partial dislocation in the homopolar
semiconductors, silicon, diamond, and germanium. In particular, we examine the
traditional single-period and our recently proposed double-period core
structures. Ab-initio and tight-binding results on the core energies are
discussed, and the geometries are compared in light of the available
experimental information about dislocations in these systems. The double-period
geometry is found to be the ground-state structure in all three materials. We
address boundary-conditions issues that have been recently raised about these
results. The structures of point excitations (kinks, solitons, and kink-soliton
complexes) in the two geometries are also reviewed.Comment: 9 pages, with 3 postscript figures embedded. Uses REVTEX and epsf
macros. Also available at
http://www.physics.rutgers.edu/~dhv/preprints/rn_eds/index.htm
Diffusion-weighted imaging: determination of the best pair ofb-values to discriminate breast lesions
In breast diffusion-weighted imaging (DWI), the apparent diffusion coefficient (ADC) is used to discriminate between malignant and benign lesions. As ADC estimates can be affected by the weighting factors, our goal was to determine the optimal pair of b-values for discriminating breast lesions at 3.0 T.
METHODS:
152 females with 157 lesions (89 malignant and 68 benign) underwent breast MRI, including a DWI sequence sampling six b-values 50, 200, 400, 600, 800 and 1000 s mm−2. ADC values were computed from different pairs of b-values and compared with ADC obtained by fitting the six b-values using a mono-exponential diffusion model (ADCall). Cut-off ADC values were determined and diagnostic performance evaluated by receiver operating characteristic analysis using Youden statistics. Mean ADCs were determined for normal tissue and lesions. Differences were evaluated by lesion and histological types.
RESULTS:
Considering the cut-off values 1.46 and 1.49 × 103mm2 s−1, the pairs 50, 1000 and 200, 800 s mm−2 showed the highest accuracy, 77.5% and 75.4% with areas under the curve 84.4% and 84.2%, respectively. The best pair for ADC quantification was 50, 1000 s mm−2 with 38/49 true-negative and 69/89 true-positive cases respectively; mean ADCs were 1.86 ± 0.46, 1.77 ± 0.37 and 1.15 ± 0.46 × 10−3 mm2 s−1 for normal, benign and malignant lesions. There were no significant differences in these ADC values when compared with ADCall (ADC calculated from the full set of b - values) [difference = 0.0075 × 10−3 mm2 s−1; confidence interval 95%: (−0.0036; 0.0186); p = 0.18].
CONCLUSION:
The diagnostic performance in differentiating malignant and benign lesions was most accurate for the b-value pair 50, 1000 s mm−2.info:eu-repo/semantics/publishedVersio
Produção de lipase intracelular por Yarrowia lipolytica utilizando óleo de fritura residual como indutor.
Microarray in clinical practice – utility vs complexity. Mixed phenotype of duplication 15q11.2q13.1 and deletion 16p11.2
Introduction: There’s a consensus to perform chromosomal microarray
technique as first-tier clinical diagnostic test for individuals with developmental
disabilities. However, given the complexity of clinical presentations, often several
diagnostic methods are held before conducting microarray.
Method: We report the case of a 5 year-old boy referred to Medical Genetics due
to short stature, developmental disabilities and facial dysmorphic features.
He was born from eutocic delivery after an uneventful pregnancy. He had
psychomotor milestones delayed like sitting at 9 months and walking at 24
months, holding an immature broad-based gait. There was history of learning
difficulties from both parents, and the mother has also short stature.
On examination it was noted some facial dysmorphic features like high forehead,
conical canines and rarefaction of the distal portion of the eyebrows.
Due to the history of an episode of transient ataxia, and suspicion of an inherited
metabolic disorder, he had already performed various analytical and imaging
screenings, all normal.
Results: Chromosomal microarray analysis revealed two pathogenic Copy
Number Variants (CNV’s): 16p11.2 deletion and 15q11.2q13.1 duplication.
The 15q11q13 microduplication syndrome (OMIM # 608636) is a very rare clinical
entity with about 30 reported cases with maternal origin, and it is characterized by
neurobehavioral disorder, hypotonia, cognitive impairment, epilepsy and short
stature.
The 16p11.2 microdeletion syndrome (OMIM # 613444) is also a rare clinical
entity, with high penetrance, associated with obesity and developmental
disabilities.
Discussion: Despite the unquestionable utility of microarray, the correlation of
the CNV's with the phenotype is often difficult by the rarity of these new
microdeletion/duplication clinical entities. In this case the interpretation has
increased difficulty because of the simultaneous existence of two distinct clinical
entities. Segregation studies, which in the first step include parental analysis, are
essential for genetic counseling and determining the risk of recurrence but also
for a more accurate correlation genotype-phenotype
A class of Poisson-Nijenhuis structures on a tangent bundle
Equipping the tangent bundle TQ of a manifold with a symplectic form coming
from a regular Lagrangian L, we explore how to obtain a Poisson-Nijenhuis
structure from a given type (1,1) tensor field J on Q. It is argued that the
complete lift of J is not the natural candidate for a Nijenhuis tensor on TQ,
but plays a crucial role in the construction of a different tensor R, which
appears to be the pullback under the Legendre transform of the lift of J to
co-tangent manifold of Q. We show how this tangent bundle view brings new
insights and is capable also of producing all important results which are known
from previous studies on the cotangent bundle, in the case that Q is equipped
with a Riemannian metric. The present approach further paves the way for future
generalizations.Comment: 22 page
Microrganismos endofÃticos: potencial de uso como agentes de biocontrole da ferrugem do cafeeiro.
O reino vegetal é colonizado por uma diversidade de microrganismos endofÃticos, principalmente bactérias e fungos, os quais estabelecem relações não patogênicas com seus hospedeiros. Quando benéficas tais associações podem estimular o crescimento das plantas, aumentar a resistência a doenças e as condições adversas do ambiente, como estresse hÃdrico. Relatos dessas caracterÃsticas inerentes aos endófitas despertaram o interesse da comunidade cientÃfica, que passou a estudar meios de inserir isolados previamente selecionados no sistema de produção agrÃcola. Assim, nas últimas décadas intensificaram-se os trabalhos buscando microrganismos endofÃticos com capacidade de promover o crescimento de culturas agronômicas e de atuar como agentes de biocontrole de fitopatógenos, estudando os possÃveis mecanismos envolvidos nessas interações com as plantas, e formas de preservação e de aplicação dos isolados no campo. No presente trabalho 217 bactérias e 17 fungos endofÃticos de cafeeiro foram testados em discos de folhas e os de melhor desempenho, em mudas de cafeeiro "Mundo Novo", para o controle de Hemileia vastatrix. As bactérias endofÃticas 3F e 119G destacaram-se proporcionando redução da severidade da ferrugem em torno de 85%. Estudando os possÃveis mecanismos de controle envolvidos, encontrou-se aumento da atividade de peroxidase em mudas de cafeeiro tratadas com as endófitas em questão. As mesmas bactérias inibiram também a germinação de urediniosporos em testes in vitro. Alguns isolados, porém, aumentaram a suscetibilidade do hospedeiro ao ataque do patógeno.bitstream/CNPMA/7434/1/boletim_38.pd
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