The effect of some processing conditions on the characteristics of biodegradable microspheres obtained by an emulsion solvent evaporation process

Unloaded microspheres were prepared from polyhydroxybutyrate (PHB) and polyhydroxybutyrate-co-valerate (PHB-HV) polymers using an oil-in-water emulsion solvent evaporation method. The study was conducted to evaluate how the polymer and some process parameters affect properties of the final microspheres such as particle size, superficial area, zeta potential, surface morphology and microsphere degradation. The variables included surfactant concentration in the emulsion water phase and solvent composition. From the results, it was found that the parameters affecting microsphere size the most were surfactant concentration in the emulsion water phase and solvent composition. Properties such as zeta potential, surface area and surface morphology remained pratically unchanged over the range of the processing conditions studied here.011

Superdiffusion in Decoupled Continuous Time Random Walks

Continuous time random walk models with decoupled waiting time density are studied. When the spatial one jump probability density belongs to the Levy distribution type and the total time transition is exponential a generalized superdiffusive regime is established. This is verified by showing that the square width of the probability distribution (appropriately defined)grows as $t^{2/\gamma}$ with $0<\gamma\leq2$ when $t\to \infty$. An important connection of our results and those of Tsallis' nonextensive statistics is shown. The normalized q-expectation value of $x^2$ calculated with the corresponding probability distribution behaves exactly as $t^{2/\gamma}$ in the asymptotic limit.Comment: 9 pages (.tex file), 1 Postscript figures, uses revtex.st

Impact of a winter upwelling event on the distribution and transport of sardine (Sardina pilchardus) eggs and larvae off western Iberia: a retention mechanism.

A hydrographic and ichthyoplanktonic survey was conducted on the western Iberia Peninsula shelf-slope, with the objective of assessing the influence of wind-driven flow on the transport and survival of sardine early life history stages. Measurements were taken during a 2-week period of an 'upwelling-favourable' wind event. An offshore displacement of the surface low salinity Western Iberia Buoyant Plume (WIBP) was observed well off the shelf break. Below the plume, the current was southward over the mid- and inner-shelf. Offshore, the flow was poleward in the northern part of the survey area and equatorward in the south. A convergence zone was detected along the outer shelf and upper slope where the buoyant plume was apparently trapped and deepened. In general, eggs and larvae were distributed according to the spreading of the low salinity surface waters, and also within the convergent band. Older larvae were retained within the latter feature. The role of wind forcing on the plume and its interaction with the slope flow were analysed. A mechanism of larvae retention was formulated based on simplified models of the observed shelf-slope circulation

Contenido de fosfátidos en el aceite de soja en función del contenido de humedad en la cosecha y el tiempo de almacenamiento del poroto

The influence of soybean moisture content-at-harvest and storage time upon total and non-hydratable phosphatides content in oil and bean phospholipase D activity was evaluated. Tests were performed upon soybeans harvested with moisture contents between 14.4 and 33.3% weight wet basis (wb). They were air dried at 25ºC until achieving safe storage moisture contents between 12.8 and 13.5 % wb and were stored at the same temperature for 245 days. Periodically they were analyzed for total and non-hydratable phosphatides content and phospholipase D activity. Total phosphatides initial content was high in soybeans with higher initial moisture levels and decreased slightly with time. Total phosphatides content remained constant at their initial levels in soybeans with lower initial moisture content. Non-hydratable phosphatides content was related to the phospholipase D activity, which decreased 30–35 days after harvest, and then stabilized, with values between 3.0 x 10-4 and 3.8 x 10-4 choline mmol/(min • soybean g).Se evaluó la influencia del contenido de humedad en la cosecha y el tiempo de almacenamiento del poroto de soja sobre el contenido de los fosfátidos totales y no hidratables en el aceite y la actividad de la fosfolipasa D en el poroto. Los porotos fueron cosechados con humedades entre el 14.4 y 33.3 %, secados con aire a 25 ºC hasta 12.8 - 13.5 % y almacenados durante 245 días. Periódicamente se determinó el contenido de fosfátidos y la actividad de la fosfolipasa D. Para los valores más altos de humedad, el contenido inicial de fosfátidos totales fue alto, disminuyendo con el tiempo. En los porotos con humedades más bajas el contenido de fosfátidos totales se mantuvo en sus valores iniciales. El contenido de fosfátidos no hidratables está relacionado con la actividad de la fosfolipasa D, la cual disminuye hasta 30-35 días después de la cosecha y luego se estabiliza en valores entre 3.0 x 10-4 y 3.8 x 10-4 mmol de colina/(min • g de soja)

Conductividad eléctrica en muestras delgadas de hielo

En el presente las propiedades físicas de la superficie del hielo no son completamente conocidas. En este trabajo se ha disertado una experiencia para estudiar su comportamiento eléctrico minimizando las contribuciones del volumen. A tal fin se usó un portamuestras de cuatro terminales que permite muestras de 20mm x 20mm de área útil y espesor variable. La electrónica asociada que se disertó permite medir directamente las componentes real e imaginaria de la corriente y deducir las respectivas componentes de la conductividad. Para el preparado de las muestras se crecen monocristales por el método de Jaccard y se cortan al tamaño y espesor deseado determinando el plano cristalina por medio de réplicas. A la muestra se le aplica un voltaje alterno y se mide la corriente que la atraviesa. A diferencia del comportamiento volumétrico no se observa una relajación según el modelo de Debye. La corriente es principalmente real y presenta un crecimiento monótono con la frecuencia existiendo un cambio en la pendiente a lkhz. La dependencia con la temperatura sigue una ley de Arrhenius con una energía de activación cercana a leV.Nowadays the physical properties of ice surface are not completely known. In the present work an exper i ence has been carrled out to study its electrical behaviour minimizing the bulk contribution. With that purpose a sample holder admitting samples with work area of 20mm x 20mm and variable thickness has been used. The necessary electronic equipment was developed in order to measure the real and imaginary contributions to the current and the respective components of conductivity separately. To prepare the samples, single-crystals of ice were gronwn following Jaccard's method and they were cut according to the size and thickness deslred. The crystal plañe was determinad by means of etch pits in Formvar replics. An altérnate voltage was applied to the sample and the current across it was measured. Uní i ke bulk behaviour a relaxation was not observed, as predicted by Debye's model. The current was mal ni y real and showed a monotonous growth with frequency. A change was observed in the rate of growth at lkhz too. The temperatura dependence fitted an Arrhenius law with an activation energy near leV.Asociación Argentina de Geofísicos y Geodesta

Physical–biological interactions in the life history of small pelagic fish in the Western Iberia Upwelling Ecosystem.

This paper reviews relevant investigations conducted in the Western Iberia Upwelling Ecosystem (WIUE) on the dynamics of small pelagic fish (SPF), its relationship to climate changes and processes related to the ‘ocean triad’ (enrichment, concentration, transport/retention). In the last decades, a decline in the productivity of several SPF species (e.g., sardine and horse mackerel) was observed in the WIUE, which is partially explained by environmental variability (e.g., changes in coastal upwelling). The main mechanism proposed to explain this decline is the increased frequency and intensity of upwelling events during the spawning season (winter) of these species, which is typically a period when convergence conditions prevail. Thus, this ‘anomalous’ situation promotes egg and larval dispersal away from the favourable coastal habitat (the shelf) and consequently has a negative impact on their survival and recruitment. However, the variability of local features like the Western Iberia Buoyant Plume (WIBP) and the Iberian Poleward Current (IPC) introduce important fluctuations in the transport patterns of the region, and could modulate the impact of these winter upwelling events in the survival of larvae. The retention on the shelf of larval sardine along convergence zones formed by the interaction of these two features plays an important role in their survival. Furthermore, the WIBP is a suitable environment for the growth of phytoplankton and for larval fish survival. From these findings it is clear that simplified Ekman transport models could not explain larval fish transport/retention patterns in this region and more realistic biophysical models should be used to simulate the local oceanographic conditions to understand larval dynamics and the success of recruitment of SPF in the Western Iberia