1,438 research outputs found
Mapa parcial de ligação gênica em Coffea arabica L.
Em uma população F2 de 215 indivíduos, originária do cruzamento entre cafeeiros "Híbrido de Timor" (H445-46) e "Catuaí" (2143-235) foram analisados 102 marcadores RAPD. Com estes, foi confeccionado um mapa parcial em que 89 marcadores se posicionaram em 14 grupos de ligação. Treze marcadores não se ligaram a nenhum grupo formado. Houve distorção de segregação para 54 marcas. O mapa cobriu parte do genoma, mas novas marcas devem ser encontradas para saturação dos intervalos e formação de novos grupos
Efeito de sistemas produtivos sobre a comunidade de insetos em eucalipto
A integração de espécies vegetais pode promover um aumento da biodiversidade de insetos herbívoros e favorecer a permanência de predadores nesse habitat devido à existência de alimento. Consequentemente, a ocorrência de outbreaks de populacões de fitófagos é reduzida. Diante disso, objetivou-se avaliar a flutuação populacional de insetos -praga pertencentes à Psylloidea e Thysanoptera, bem como adultos de Neuroptera como grupo de predadores, em eucalipto em sistemas integrados de produção (silvipastoril, silviagrícola e agrossilvipastoril) e em monocultivo. O ensaio está localizado em Sinop/MT (11 0 51? 38??S e 55 0 37? 01??O) em um delineamento experimental de blocos ao acaso com quatro repetições, sendo cada parcela constituída de 2 ha. Para amostragem dos insetos foram utilizadas 02 armadilhas adesivas amarelas (10 x 12 cm), instaladas equidistantes por parcela a 1,8 m do solo e elevadas conforme o crescimento da altura das copas. As coletas foram realizadas quinzenalmente, durante o período da seca (junho a setembro) e mensalmente durante o período chuvoso (outubro a dezembro) de 2013. No laboratório realizou-se a quantificação e identificação dos insetos utilizando um estéreo-microscópio e material bibliográfico. Utilizando a análise de agrupamento hierárquica em dendrograma, observ ou-se que os sistemas produtivos em que o eucalipto está integrado se agrupam e são diferentes do eucalipto em monocultivo. Apenas a população de Thysanoptera foi significativamente maior no eucalipto em monocultivo. Entretanto, em todos os tratamentos, a comunidade de herbívoros -praga não causaram danos no eucalipto. Desta forma, a presença de fitófagos em sistemas integrados pode contribuir para o Manejo Integrado de Pragas por atuar como fonte de alimentos para predadores como os crisopídeos que se manterão no agroecossistema durante a entressafra das culturas anuai
Public perception of folate‐biofortifed genetically modifed lettuce varieties in Brazil.
Lettuce is one of the most widely consumed vegetables in the world, commonly eaten fresh in salads, sandwiches, wraps, and as a garnish in various dishes. Consequently, it is a very promising vehicle to deliver vitamins, such as folate (vitamin B9), to a specifc population using biofortifed varieties generated by conventional or molecular breeding. A new genetically modifed lettuce was generated with increased folate content. However, some issues related to public perception regarding this technology should still be evaluated. The aim of this study was to analyze whether consumers are willing to accept a folate-biofortifed GM lettuce that could become available to the Brazilian market. A questionnaire involving several issues regarding lettuce consumption was answered by 2,391 people from almost all Brazilian states. When informed that the folic acid biofortifed lettuce is a transgenic plant, 46.1% of respondents stated that they would eat it and 30.5% stated that it would be a possibility. This study demonstrated that if there is any explanation regarding the advantage in relation to the use of biotechnology, like enrichment with folic acid, the number of people who accept it increases
Universality, frustration and conformal invariance in two-dimensional random Ising magnets
We consider long, finite-width strips of Ising spins with randomly
distributed couplings. Frustration is introduced by allowing both ferro- and
antiferromagnetic interactions. Free energy and spin-spin correlation functions
are calculated by transfer-matrix methods. Numerical derivatives and
finite-size scaling concepts allow estimates of the usual critical exponents
, and to be obtained, whenever a second-order
transition is present. Low-temperature ordering persists for suitably small
concentrations of frustrated bonds, with a transition governed by pure--Ising
exponents. Contrary to the unfrustrated case, subdominant terms do not fit a
simple, logarithmic-enhancement form. Our analysis also suggests a vertical
critical line at and below the Nishimori point. Approaching this point along
either the temperature axis or the Nishimori line, one finds non-diverging
specific heats. A percolation-like ratio is found upon analysis of
the uniform susceptibility at the Nishimori point. Our data are also consistent
with frustration inducing a breakdown of the relationship between
correlation-length amplitude and critical exponents, predicted by conformal
invariance for pure systems.Comment: RevTeX code for 10 pages, 9 eps figures, to appear in Physical Review
B (September 1999
Duality in finite-dimensional spin glasses
We present an analysis leading to a conjecture on the exact location of the
multicritical point in the phase diagram of spin glasses in finite dimensions.
The conjecture, in satisfactory agreement with a number of numerical results,
was previously derived using an ansatz emerging from duality and the replica
method. In the present paper we carefully examine the ansatz and reduce it to a
hypothesis on analyticity of a function appearing in the duality relation. Thus
the problem is now clearer than before from a mathematical point of view: The
ansatz, somewhat arbitrarily introduced previously, has now been shown to be
closely related to the analyticity of a well-defined function.Comment: 12 pages, 3 figures; A reference added; to appear in J. Stat. Phy
Correlation functions in the two-dimensional random-field Ising model
Transfer-matrix methods are used to study the probability distributions of
spin-spin correlation functions in the two-dimensional random-field Ising
model, on long strips of width sites, for binary field
distributions at generic distance , temperature and field intensity
. For moderately high , and of the order of magnitude used in
most experiments, the distributions are singly-peaked, though rather
asymmetric. For low temperatures the single-peaked shape deteriorates, crossing
over towards a double- ground-state structure. A connection is obtained
between the probability distribution for correlation functions and the
underlying distribution of accumulated field fluctuations. Analytical
expressions are in good agreement with numerical results for ,
low , not too small, and near G=1. From a finite-size {\it ansatz} at
, , averaged correlation functions are predicted to
scale with , . From numerical data we estimate y=0.875 \pm
0.025WR/L=1W \sim h_0^{\kappa} f(L h_0^u)\kappa \simeq 0.45u \simeq 0.8f(x)x \to \inftyW \sim
h_0^{\kappa}d=2$.Comment: RevTeX code for 8 pages, 7 eps figures, to appear in Physical Review
E (1999
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