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425 records were found.

La actividad optativa pasantía y la resolución de problemas como estrategia en la enseñanza de la fisiología vegetal

Eje temático 1: Problemáticas y alternativas de mejora de la enseñanza d - La articulación entre enseñanza y práctica profesional

Ethylene production by the flag leaf and panicle and their effects on grain quality in rice (Oriza sativa)

Ethylene is a plant hormone that regulates several physiological processes, such as, senescence of leaves and ripeness of inflorescence in cereals. The aim of this work was to determine if ethylene is involved in rice grain ripeness and its culinary quality. AVG (aminoethoxyvinylglycine) and Ethephon (chloroethylphosphonic acid) were sprayed on different rice plots cv. Yeruá P.A. from anthesis to grain ripeness. Ethylene production was quantified in both, panicles and flag leaves. Chlorophyll content, as a senescence index, was measured on the latter. Grain culinary quality was evaluated by calculating the starch amilose percentage and by recording starch gelatinization temperature. Ethylene production increased during flag leaves senescence and panicle ripeness in all plots. The amilose percentage also increased significantly in grain...

Resistive transition in disordered superconductors with varying intergrain coupling

The effect of disorder is investigated in granular superconductive materials with strong and weak links. The transition is controlled by the interplay of the \emph{tunneling} $g$ and \emph{intragrain} $g_{intr}$ conductances, which depend on the strength of the intergrain coupling. For $g \ll g_{intr}$, the transition involves first the grain boundary, while for $g \sim g_{intr}$ the transition occurs into the whole grain. The different intergrain coupling is considered by modelling the superconducting material as a disordered network of Josephson junctions. Numerical simulations show that on increasing the disorder, the resistive transition occurs for lower temperatures and the curve broadens. These features are enhanced in disordered superconductors with strong links. The different behaviour is further checked by estimating the ave...

Space-Charge-Limited Current Fluctuations in Organic Semiconductors

Comment: corrected proofs

$f^{-\gamma}$ Current Fluctuations in Organic Semiconductors: Evidence for Percolation

Comment: 11 pages, 2 figures, to appear on European Physical Journal B

Power grids vulnerability: a complex network approach

Comment: 16 pages, 3 figures. Figure 2 and table II modified. Typos corrected. Version accepted for publication in Chaos

Array of Josephson junctions with a non-sinusoidal current-phase relation as a model of the resistive transition of unconventional superconductors

Comment: Added: comparison with experiments; references

Expression of the monomeric 67-kd laminin-binding protein in human lymphomas as defined by MLuC5 monoclonal antibody and paraffin section immunohistochemistry.

Interactions between cancer cells and laminin, a major component of basement membranes, are mediated through a large variety of cell surface proteins designated as laminin receptors. Among the above proteins, a 67-kd monomeric high affinity laminin receptor (67 LR) has long been suspected to be involved in tumor progression. In this study we wished to establish whether the 67 LR molecule is detectable on tumor cells of Hodgkin's disease (HD) and non-Hodgkin's lymphomas (NHLs), to define its pattern of expression, and to assess the potential utility of 67 LR in differentiating these pathological entities. Morphological and immunohistological studies were performed on 85 specimens of HD and a series of 334 NHL specimens, including anaplastic large cell (ALC) (CD30-positive) lymphomas (73 specimens). For immunohistochemical assessment of ...

Resistive transition in granular disordered high-T$_c$ superconductors: a numerical study

The resistive transition of granular high-T$_c$ superconductors, characterized by either weak (YBCO-like) or strong (MgB$_2$-like) links, occurs through a series of avalanche-type current density rearrangements. These rearrangements correspond to the creation of resistive layers, crossing the whole specimen approximately orthogonal to the current density direction, due to the simultaneous transition of a large number of weak-links or grains. The present work shows that exact solution of the Kirchhoff equations for strongly and weakly linked networks of nonlinear resistors, with Josephson junction characteristics, yield the subsequent formation of resistive layers within the superconductive matrix as temperature increases. Furthermore, the voltage noise observed at the transition is related to the resistive layer formation process. Th...

Phosphorylation of threonine in the proline-rich carboxy-terminal region of simian virus 40 large T antigen.

The position of phosphothreonine in the predicted primary structure of simian virus 40 large T antigen was determined by different methods. After digestion of large T antigen with trypsin and subsequent two-dimensional peptide mapping, a single peptide containing phosphothreonine could be separated from the bulk of phosphoserine-containing peptides. Its amino acid composition was determined by differential labeling with various amino acids in vivo. The high yield of proline (4.5 mol) within the phosphothreonine peptide indicated that it was derived from the carboxy terminus of large T antigen and had in its unphosphorylated form the sequence Lys-Pro-Pro-Thr-Pro-Pro-Pro-Glu-Pro-Glu-Thr-COOH. A phosphopeptide generated by chymotrypsin could be converted into the tryptic phosphothreonine peptide, indicating that the latter was part of the...