123 research outputs found
Dry matter and area partitioning, radiation interception and radiation-use efficiency in open-field bell pepper
The objective of this study was to determine some key components of a model for bell pepper growth and
yield under non-limiting water and nutrient conditions using data from field trials conducted in
Southern Portugal. DM partitioning, at least before fruiting, and specific area indices for leaves, stems
and fruits were conservative in relation to normalized thermal time. The interception model had a good
performance. It was based on the exponential extinction of radiation on the area covered by the plants,
the ellipsoidal leaf-angle distributionmodel (X-parameter 2.48 and 2.89), and absorptivities of the leaves
for PAR and NIR, 0.8 and 0.2, respectively. Radiation-use efficiency (RUE) was determined and presented
in four different forms. RUE did not change substantially throughout the growing season. RUE of irrigated
pepper crops grown in our experiments was around 1.6 g MJ 1 of intercepted PAR. The models and
parameter values presented in this study may be useful to simulate the development and growth of fieldgrown
pepper cro
Emerging Enteropathogenic Escherichia coli Strains?
Escherichia coli strains of nonenteropathogenic serogroups carrying eae but lacking the enteropathogenic E. coli adherence factor plasmid and Shiga toxin DNA probe sequences were isolated from patients (children, adults, and AIDS patients) with and without diarrhea in Brazil. Although diverse in phenotype and genotype, some strains are potentially diarrheagenic
Variability in oxidative degradation of charcoal: influence of production variables and environmental exposure
<p>Charcoal is a key component of the Black Carbon (BC) continuum, where BC is characterized as a recalcitrant, fire-derived, polyaromatic material. Charcoal is an important source of palaeoenvironmental data, and of great interest as a potential carbon sink, due to its high apparent environmental stability. However, at least some forms of charcoal are clearly susceptible to environmental alteration and degradation over relatively short timescales. Although these processes have importance for the role of charcoal in global biogeochemistry, they remain poorly understood.</p>
<p>Here we present results of an investigation into the susceptibility of a range of charcoal samples to oxidative degradation in acidified potassium dichromate. The study examines both freshly-produced charcoal, and charcoal exposed to environmental conditions for up to 50,000 years. We compare the proportion of carbon present in different forms between the samples, specifically with respect to the relative chemical resistance of these forms. This was undertaken in order to improve understanding of the post-depositional diagenetic changes affecting charcoal within environmental deposits.</p>
<p>A wide range in chemical compositions are apparent both within and between the sample groups. In freshly-produced charcoal, material produced at 300 °C contains carbon with more labile forms than charcoal produced at ≥400 °C, signifying a key chemical change over the 300–400 °C temperature range. Charcoal exposed to environmental depositional conditions is frequently composed of a highly carboxylated aromatic structure and contains a range of carbon fractions of varying oxidative resistance. These findings suggest that a significant number of the environmental charcoals have undergone post-depositional diagenetic alteration. Further, the data highlight the potential for the use of controlled progressive oxidative degradation as a method to characterize chemical differences between individual charcoal samples.</p>
Alterations and spatial variability of soil fertility in successive years under no tillage system
Chemical composition of essential oil extracted from leaves of Campomanesia adamantium subjected to different hydrodistillation times
Avaliação nutricional do capim-elefante (Cameroon) em diferentes idades de rebrotação
NÃveis de proteÃna bruta em rações para suÃnos machos castrados em fase inicial de crescimento, mantidos em ambiente de baixa temperatura
Crescimento e acumulação de nitrogênio de plantas de feijoeiro originadas de sementes com alto teor de molibdênio
Divergência genética entre acessos de espinheira-santa (Maytenus ilicifolia Mart. ex Reissek e M. aquifolium Mart.) com base em caracteres morfológicos e fisiológicos
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