Characterization of Physical Properties of Flour and Starch Obtained from Gamma‐Irradiated White Rice

Physical and structural characteristics of rice flour and starch obtained from gamma‐irradiated white rice were determined. Pasting viscosities of the rice flour and starch, analyzed by using a Rapid Visco Analyser, decreased continuously with the increase in irradiation dosage. Differential scanning calorimetry showed that gelatinization onset, peak and conclusion temperatures of rice flour and starch changed slightly but the enthalpy change decreased significantly with increase of irradiation dosage. All irradiated starch displayed an A‐type X‐ray diffraction pattern like the native starch. Gel permeation chromatography showed that the blue value ratio of the first peak (amylopectin) to the second one (amylose) decreased with the increase of the irradiation dosage. The weight‐average molecular weight (M_w) and gyration radius (R_z) of amylopectin analyzed by using HPSEC‐MALLS‐RI (high‐performance size‐exclusion chromatography equipped with multiangle laser‐light scattering and refractive index detector) decreased gradually from 1.48×10⁹ (M_w) and 384.1 nm (R_z) of native rice starch to 2.36×10⁸ (M_w) and 236.8 nm of 9 kGy‐irradiated starch. The branch chain‐length distribution of amylopectins determined by HPAEC‐ENZ‐PAD (high‐performance anion‐exchange chromatography with amyloglucosidase post‐column on‐line reactor and pulsed amperometric detector) showed that gamma irradiation had no significant effect on the amylopectin branch chains with 13≤DP≤24 and 37≤DP, but produced more branch chains with 6≤DP≤12 when the irradiation dosage was less than 9 kGy. It might be deduced that gamma irradiation caused the breakage of the amylopectin chains at the amorphous regions, but had little effects on the crystalline regions of starch granules, especially at low dosage irradiation.     

Survival of Listeria monocytogenes and Escherichia coli O157:H7 during sauerkraut fermentation

Sauerkraut was produced from shredded cabbage, as is typical in the United States, and from whole head cabbages, which is a traditional process in parts of Eastern Europe. The sauerkraut was inoculated with five strain mixtures of Escherichia coli O157:H7 and Listeria monocytogenes, and the populations of these bacteria, as well as lactic acid bacteria, pH, and titratable acidity, were monitored over the course of fermentation. Fermentation variables were temperature (18 and 22 degrees C) and salt concentration (1.8, 2.25, and 3%). For most of the analyses, the type of cabbage processing was a significant factor, although within cabbage type, neither salt nor fermentation temperature had significant effects. The final pH of the whole-head sauerkraut was lower than the shredded sauerkraut, but the titratable acidity was significantly higher in the shredded sauerkraut. E. coli O157:H7 and L. monocytogenes persisted in the brines for most of the fermentation, although at the end of the fermentations (15 days for shredded, 28 days for whole head), neither pathogen had detectable populations. E. coli populations decreased more rapidly in the shredded sauerkraut even though the pH was higher because of the higher total acidity in the shredded sauerkraut. Acid-tolerant strains of E. coli and L. monocytogenes were isolated from both shredded and whole-head sauerkraut at different salt concentrations and temperatures after 15 days of fermentation and could be detected at 35 days in the wholehead sauerkraut.     

Effects of an encounter group experience on self-perception and interpersonal relations.

Conducted a controlled laboratory investigation of an encounter group experience involving 24 Ss. All Ss 1st participated in a group discussion and rated each other and self on liking, trust, openness, and relaxation. A week later, 1/2 of the Ss participated in a 2-day group encounter and, subsequently, all Ss met again in discussion and were rerated on the same values by each other, self, and independent Os. Results show the encounter Ss improved in self concept, intragroup cohesiveness and liking, and ability to relate to others. No such changes were found for the controls. Negatively, however, the Os did not find any difference between experimental Ss and controls. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Estimation of diffusion coefficient of chromium in colloidal silica using digital photography

In order to study the effectiveness of using colloidal silica, NYACOL DP5110, to stabilize chromium-contaminated soil, the diffusion of chromium in colloidal silica gel was estimated from laboratory experiments. To measure diffusion coefficients of chromium in the colloidal silica gel, a new measurement method based on digital photography was introduced. A series of experiments were designed and conducted to validate this new method and to estimate the diffusion coefficients of chromium in the colloidal silica gel. Accuracy of the proposed method was evaluated by several differentways. It was found that the apparent diffusion coefficient of chromium in colloidal silica gel ranged from 1.76 to 8.48 x 10(-10) m2/s depending mainly on the concentration of silica in the gel with chromium concentration less than 10(-2) M. Higher silica concentrations yielded lower diffusion coefficients due to the obstruction to the free movement of chromium. The adsorption isotherm of chromate to colloidal silica gel was found to be linear at pH 7; the partition coefficient was calculated to be 0.549 L/g. Mass balance calculations were performed to evaluate the accuracy of the proposed method and found that the measuring error was less than 6.5%. Based on the test data, the estimation of diffusion coefficients for chromium in colloidal silica gel using digital photography seems to be accurate and precise. This method is suitable for analyzing colored chemicals inside clear/white gels. From the results, it can be concluded that the gel behaves as a porous material with silica network forming continuous solid phase and its pore space saturated with water. The chromium ions diffuse in porous silica gel on a tortuous path. Therefore, the bulk diffusion dominates. Thus, the silica can be represented as a fix and impenetrable immersion in the solution. The presence of these motionless silica chains leads to an increase in the mean path of the diffusing molecules between two points in the system. On the basis of the test results, it can also be concluded that colloidal silica, NYACOL DP5110, for in-situ treatment of chromium-contaminated soils seems to be ineffective. Further research of more realistic simulation of diffusion and refined gel formulation with the capacity to convert the chromium to an immobile form is recommended.     

Iron Particles Coated with Alumina: Synthesis by a Mechanofusion Process and Study of the High-Temperature Oxidation Resistance

The mechanofusion process, a dry particle coating route, has been successfully applied to coat iron particles with alumina. The high-temperature oxidation resistance of Fe and coated Fe particles has been comparatively investigated in air in the temperature range 350°–900°C. The activation energy calculations demonstrate that, in the temperature range 350°–420°C, the oxidation mechanisms are the same for both particles. Scanning electron microscopy and energy-dispersive spectroscopy analyses show that oxidation products are mainly formed at the iron/alumina interface at low temperatures or at the alumina/gas interface at high temperatures. It is shown that, depending on the temperature range, two different oxidation mechanisms are predominant.     

Energy Transfer and Population Inversion in Heavy Metal Oxide Glasses Doped with Tm3+ and Tb3+

Emission properties and energy transfer of PbO–Bi₂O₃–Ga₂O₃–GeO₂ glasses codoped with Tm³⁺ and Tb³⁺ ions were investigated. The 1.48-μm emission due to the Tm³⁺:³H₄→³F₄ transition can be used to amplify the S-band (1460–1530-nm) signal light. With Tb³⁺ addition, the lifetime and emission intensity of the Tm³⁺:³F₄ level decreased sharply via the Tm³⁺:³F₄→Tb³⁺:⁷F_0,1,2 energy transfer. Population densities of the ³F₄ and ³H₄ levels in Tm³⁺ calculated from rate equations clearly verified that population inversion in Tm³⁺ ions became possible with as little as 0.1 mol% of Tb³⁺ addition.