Partial or total silylation of dextran with hexamethyldisilazane

The silylation reaction of dextran with 1,1,1,3,3,3-hexamethyldisilazane (HMDS) in DMSO was studied as the first step of the synthesis of new amphiphilic polyester-grafted dextrans. According to the experimental conditions, i.e. dextran molar weight, medium temperature and reaction time, HMDS/OH ratio, addition of a catalyst and co-solvent, partially or totally silylated dextrans were recovered. The highest silylation yields were obtained with the lowest molecular weight dextrans. The increase in temperature medium and/or reaction time, the presence of catalyst or co-solvent favored the protection yield. Whatever the dextran used, complete silylation of the polysaccharide chain could be achieved by adequate selection of the experimental conditions. The thermal properties of resulting silylated polysaccharides were investigated by temperature modulated DSC. It was observed that T_g values of partially silylated dextran were maintained between 120 and 140 °C, independently of the dextran molecular weight. Interestingly, DMSO proved to behave as an efficient plasticizer of (partially) silylated dextrans. The partially silylated dextrans were efficiently used as multifunctional macroinitiators for the controlled ring-opening polymerization (ROP) of lactone. The ROP was then promoted from the remaining hydroxyl groups in the presence of tin or aluminium activator. After polymerization and ultimate deprotection of the silylated dextran backbone, amphiphilic polyester-grafted dextrans were readily recovered.     

Watershed and River Systems Management Program: Overview of Capabilities

Beginning in January 1992, the Bureau of Reclamation (Reclamation) and the US Geological Survey (USGS) formulated plans for the Watershed and River Systems Management Program—a cooperative interagency effort to develop and implement flexible and robust river basin management tools for the benefit of managers and decision makers using a data centered approach. In addition to Reclamation and the USGS, a number of other agencies and universities have made substantial contributions to the success of the program. The result has been the need driven research and development of state-of-the-art technology which benefits water managers and technical specialists in many river basins.     

Preparation of spherical aggregates of taro starch granules

Taro starch spherical aggregates were prepared by including a spray drying step in a conventional pilot plant-scale starch isolation procedure. The aim of this study was to characterize these spherical aggregates. The procedure was repeated three times to verify the spherical aggregates formation, which was shown by scanning electron microscopy. Amylose was not be detected in the aggregates, and a protein content of 4.5 g/100 g was recorded. Aggregation of taro starch granules did not affect the X-ray diffraction pattern. The maximum peak viscosity of the aggregate preparation was obtained at a relatively high temperature (i.e. start of the temperature holding step). The phase transition of taro starch aggregates in excess water showed high temperatures, with low molecular reorganization during storage. During water retention capacity (WRC) and solubility tests, taro starch aggregates were stable until 70 °C. The spray drying conditions used produced spherical aggregates of taro starch that presented physicochemical and functional characteristics with potential for encapsulation of substances.     

Improvement of emulsifying properties of milk proteins with κ or λ carrageenan: effect of pH and ionic strength

The objective of this work was to determine the effect of λ‐carrageenan or κ‐carrageenan on the emulsion capacity, emulsion work and emulsion stability of milk proteins concentrate (MP) or sodium caseinate (SC) emulsions at different levels of pH and ionic strength. Incorporation of carrageenans to proteins emulsions resulted in an improvement of emulsifying properties at pH 6.0 and low ionic strength (0.2 m NaCl). Although emulsion capacity was high in MP than for SC, irrespectively of carrageenan employed, addition of λ‐carrageenan increased twofold emulsion work values (15 327 Ω s^?1 for MP and 11 455 Ω s^?1 for SC; around 6000 Ω s^?1 in the other treatments). Emulsion stability was high with λ‐carrageenan (9.8 s) than MP‐κ‐carrageenan or MP (7.45 and 7.40 s, respectively). Carrageenan improving of emulsion properties was because of the complex formation with MP, characteristic of this type of food system when pH was above of isoelectric point.     

Delineation of female performance on the Rey-Osterrieth Complex Figure.

103 female college students (aged 18–24 yrs) were administered the Rey-Osterrieth Complex Figure on Copy, Immediate Recall, and 20-min Delayed Recall. Ss were grouped based on handedness, familial handedness, and academic major (mathematics/science and nonmath/science). Based on the scoring system of D. Waber and J. Holmes (see PA, Vols 72:24305 and 74:9917) the mathematics/science anomalous dominance groups obtained higher mean scores than all other subgroups, and the non-math/science familial right-handers were the low performers. The high-performing groups may have an increased ability to coordinate the use of left- and right-hemisphere processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)