Physical Stability of Octenyl Succinate–Modified Polysaccharides and Whey Proteins for Potential Use as Bioactive Carriers in Food Systems

The high cost and potential toxicity of biodegradable polymers like poly(lactic‐co‐glycolic)acid (PLGA) has increased the interest in natural and modified biopolymers as bioactive carriers. This study characterized the physical stability (water sorption and state transition behavior) of selected starch and proteins: octenyl succinate–modified depolymerized waxy corn starch (DWxCn), waxy rice starch (DWxRc), phytoglycogen, whey protein concentrate (80%, WPC), whey protein isolate (WPI), and α‐lactalbumin (α‐L) to determine their potential as carriers of bioactive compounds under different environmental conditions. After enzyme modification and particle size characterization, glass transition temperature and moisture isotherms were used to characterize the systems. DWxCn and DWxRc had increased water sorption compared to native starch. The level of octenyl succinate anhydrate (OSA) modification (3% and 7%) did not reduce the water sorption of the DWxCn and phytoglycogen samples. The Guggenheim–Andersen–de Boer model indicated that native waxy corn had significantly (P < 0.05) higher water monolayer capacity followed by 3%‐OSA‐modified DWxCn, WPI, 3%‐OSA‐modified DWxRc, α‐L, and native phytoglycogen. WPC had significantly lower water monolayer capacity. All Tg values matched with the solid‐like appearance of the biopolymers. Native polysaccharides and whey proteins had higher glass transition temperature (Tg) values. On the other hand, depolymerized waxy starches at 7%‐OSA modification had a “melted” appearance when exposed to environments with high relative humidity (above 70%) after 10 days at 23 °C. The use of depolymerized and OSA‐modified polysaccharides blended with proteins created more stable blends of biopolymers. Hence, this biopolymer would be suitable for materials exposed to high humidity environments in food applications.     

Evidence of High Vertical Wave-Number Behavior in a Continuously Stratified Reservoir: Boadella, Spain

High vertical wave-number modes clearly dominate the internal wave field during the stratification period in Boadella reservoir in northeast Spain. In this period, the extraction of hypolimnetic water, due to summer irrigation, brought the surface level down by 6 m in one month and the epilimnetic water progressively occupied the whole water column. The temperature profile, with the exception of a few meters at the surface layer, presented an almost constant temperature gradient of about 0.7°C/m. The period of the main vertical mode is 24 h with an amplitude of around 1 m. Thermistor chain records and meteorological data allow us to deduce that this mode is, at least, a third vertical mode forced by the wind, which normally has a typical periodicity of 24 h. However, when the wind changes direction from south to north, the circulation cells developed due to this forced nonstationary oscillation are destroyed. When this occurs, the Bulk Richardson number is Rib ～ 1. Similar vertical structures as a response to wind forcing should be expected in similar systems, although this has not been reported in the literature.     

Nanocrystalline TiO2 photosensitized with natural polymers with enhanced efficiency from 400 to 600 nm

TiO₂ sensitization for solar applications requires not only efficient but also stable and inexpensive sensitizers. Different condensed tannins extracted from bark wastes of tropical wood trees were studied as possible sensitizers of TiO₂. These natural polymers adhere strongly to the TiO₂ even from aqueous solutions. Absorption spectra are presented for 1 mM aqueous sensitizing solutions prepared with lyophilized condensed tannins which absorb light in the visible range. Spectral photocurrent measurements and I–V characterization show that no bias is required for electron injection to the TiO₂ from all studied condensed tannins. Incident photon to current efficiency (IPCE) analysis indicates that surface complexation originates absorption bands with different electron injection efficiencies. These play a dominant role in determining IPCE spectral shape. We propose that surface modification by the sensitizer changes the surface trap density, thereby decreasing recombination losses.     

Fluctuation conductivity in Li-doped YBa2Cu3O7−x

The paraconductivity of Li-doped YBa₂Cu₃O_7?x was measured. We have found that the character of the fluctuation changes as lithium content increases: instead of a crossover from 2D to 3D behavior (D is the dimensionality), as we have observed for a low doping level, a double crossover to the 2D percolative and 3D percolative regimes becomes manifest by increasing the lithium content.     

Experimental Study of Alumina Particle Removal From a Plane surface

Micron and submicron alumina particles are often used for the mechanical polishing of the GaAs wafers processed in the microelectronic industry. A better understanding of the adhesion mechanisms is the key factor for the particle removal and for the optimisation of the industrial chemical cleaning. However, the nature and the strength of the complex interactions occurring between asymmetrical alumina particles and the surface remain unclear. Thus, an experimental study of the detachment of asymmetrical alumina particles in adhesive contact with a glass plate was done using a specially designed shear stress flow chamber. A series of experiments was performed to measure the shear stress necessary to remove individual alumina particles (of 3 and 0.3 µm nominal size) under various chemical solutions (diluted ammonia, surfactant and glycerol). Then the effects of the particle size, the resting time, the pH and the nature of the chemical solutions used for the removal of the alumina particles was characterised in terms of percentage of alumina particles detached. Results have shown that the longer the resting time, the more adherent the particles are. Moreover, it was found that the ammonia solution gives the best particle removal rate (80%) because of the strong repulsive electrostatic interactions between the alumina particles and the glass surface, both being charged negatively in a basic solution.     

Behavioral effects of centrally administered arginine vasopressin in the rat fetus.

Arginine–8 vasopressin (AVP) was administered to rat fetuses on Embryonic Day 20 via intracisternal (IC), intrahemispheric (IH), or intrathecal (IT) injection. The IC administration of AVP promoted a 4-fold increase in motor activity, including the uncommon patterns of mouthing, licking, and facial wiping. The IH injection of AVP had little effect on fetal behavior, but IT injection resulted in pronounced increases in fetal activity, including mouthing, licking, and wiping. The IT administration of a V? antagonist blocked AVP effects, whereas IH injection potentiated AVP-induced changes in fetal behavior. The IC blockade of V? receptors suppressed facial wiping to a chemosensory fluid (lemon) and reduced oral grasping of an artificial nipple, whereas IH injection of the V? antagonist promoted facial wiping responses and increased grasping of the nipple. These data suggest that AVP may play a role in the development of responsiveness to stimuli encountered in the context of suckling. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Experimental Investigation of the Recovery of Soaked Paper Using Evaporative Freeze Drying

The aim of this article is to develop an experiment and a procedure to investigate the restoration of water-damaged paper and archival materials using freeze drying in order to allow a reproducible test and comparison of the influence of different operating conditions on drying time and restored paper quality. Firstly, a reproducible method for the preparation of soaked samples simulating water-damaged paper has been developed. Then, the samples have been freeze-dried in a laboratory-scale apparatus that allowed monitoring the temperature as well as the weight of the samples. The technique of evaporative freezing, which reduces the drying time required, has been used in this case. An innovative procedure for the visualization of the progress of the drying process has been validated, thus allowing the validation of a simple phenomenological model of the time evolution of the ice core volume; in addition, data on the residual moisture of the dried paper sheets in different zones have been given. Finally, optimization of this particular drying process by using simple or more sophisticated approaches has been discussed.