An Ultrasonic Sensor for Process Modeling and Proces Control of Ceramic Superconductors
This research demonstrates the feasibility of utilizing nondestructive ultrasonic sensors to monitor the effects of oxygen content, processing time and temperature on the resultant mechanical, structural, and electrical properties of high temperature ceramic superconductors. Ultrasonic velocity changes, as a function of processing time and temperature, have clearly been shown to indicate the transformation between orthorhombic and tetragonal phases in Y-Ba-Cu-O.
On the Disorder of LiNbO3 Crystals
Results of investigations of the absorption, electrical conductivity, and photoconductivity of LiNbO3 are presented. They are explained by a model being similar to the anti-Frenkel disorder and by the formation of F2 centres during the reduction of the crystals. The model also illustrates the dependence of the Curie temperature on the Li:Nb ratio and optically induced refractive index inhomogeneities. 
 
 
 
Es werden Ergebnisse von Untersuchungen der Absorption, der elektrischen Leitfahigkeit und der Phtoleitfahigkeit von LiNbO3 vorgelegt. Sie werden mit einem der Anti-Frenkel-Fehlordnung ahnlichen Model und der Bildung von F2-Zentren bei der Reduktion der Kristalle erklart. Das Modell macht zugleich die Abhangigikeit der Curie-Temperatur vom Li:Nb-Verhaltnis und optisch induzierte Brechzahlinhomogenitaten verstandlich.
Reduced translocation of cadmium from roots is associated with increased production of phytochelatins and their precursors.
Cadmium (Cd) is a non-essential trace element and its environmental concentrations are approaching toxic levels, especially in some agricultural soils. Understanding how and where Cd is stored in plants is important for ensuring food safety. In this study, we examined two plant species that differ in the distribution of Cd among roots and leaves. Lettuce and barley were grown in nutrient solution under two conditions: chronic (4 weeks) exposure to a low, environmentally relevant concentration (1.0 μM) of Cd and acute (1 h) exposure to a high concentration (5.0 mM) of Cd. Seedlings grown in solution containing 1.0 μM CdCl₂ did not show symptoms of toxicity and, at this concentration, 77% of the total Cd was translocated to leaves of lettuce, whereas only 24% of the total Cd was translocated to barley leaves. We tested the hypothesis that differential accumulation of Cd in roots and leaves is related to differential concentrations of phytochelatins (PCs), and its precursor peptides. The amounts of PCs and their precursor peptides in the roots and shoots were measured using HPLC. Each of PC₂₋₄ was synthesized in the barley root upon chronic exposure to Cd and did not increase further upon acute exposure. In the case of lettuce, no PCs were detected in the root given either Cd treatment. The high amounts of PCs produced in barley root could have contributed to preferential retention of Cd in barley roots.