Oxidation-reduction behaviour of La-doped SrTiO3

Thermogravimetric measurements as a function of oxygen activity were performed in the temperature range of 1200 to 1400° C on a series of lanthanum SrTiO₃ compounds. A model which assumes the absorption of excess oxygen in the structure which compensates the donors by formation of cationic defects is postulated. Comparison of this model with the experimental results show reasonable agreement.On leave from the Faculty of Engineering, Cairo University, Egypt.     

Two operations for "ratios" and "differences" of distances on the mental map.

Ss judged "ratios of distances" between pairs of U.S. cities. Results fit the theory that Ss used two comparison processes as instructed. A ratio scale of distances between cities was constructed from the 2 rank orders. From this scale, an interval scale of the city locations on an east-west continuum was derived. This scale agrees with the subtractive model fit to "ratios" and "differences" of easterliness and westerliness, and it also agrees with multidimensional scaling of judged distances between cities. These findings are consistent with the theory that Ss use subtraction when instructed to judge either "ratios" or "differences," but that they can use both ratio and difference operations when the stimuli (in this case, distances) constitute a ratio scale on the subjective continuum. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A mRNA signal for the type III secretion of Yop proteins by Yersinia enterocolitica

Pathogenic Yersinia species have a specialized secretion system (type III) to target cytotoxic Yop proteins during infection. The signals of YopE and YopN sufficient for the secretion of translational reporter fusions were mapped to the first 15 codons. No common amino acid or peptide sequence could be identified among the secretion signals. Systematic mutagenesis of the secretion signal yielded mutants defective in Yop translation; however, no point mutants could be identified that specifically abolished secretion. Frameshift mutations that completely altered the peptide sequences of these signals also failed to prevent secretion. Thus, the signal that leads to the type III secretion of Yop proteins appears to be encoded in their messenger RNA rather than the peptide sequence.     

Periductal mastitis and duct ectasia: different conditions with different aetiologies

A prospective study of 14,225 patients has been undertaken to determine the inter-relationship between periductal mastitis and duct ectasia and to establish whether there is an association between smoking and either of these two conditions. Periductal mastitis affected women at a younger age than did duct ectasia. Of 139 patients with the clinical syndrome of periductal mastitis, 97 (70 per cent) had a past history of previous periductal mastitis, compared with only one (1 per cent) of 186 patients with the clinical syndrome of duct ectasia (P < 0.0001). There was a significant excess of smokers in patients with clinically (124 (89 per cent) of 139) and pathologically (71 (91 per cent) of 78) diagnosed periductal mastitis compared with age-matched controls (both P < 0.001), but there was no such excess in those with clinically (52 (28 per cent) of 186) or pathologically (15 (23 per cent) of 64) diagnosed duct ectasia. These data suggest that periductal mastitis and duct ectasia are separate conditions which affect different age groups, have different aetiologies, and should now be considered as separate entities.     

Dynamic simulation of three-dimensional rigid body systems using Vector-Network techniques

This paper describes a new approach to the problem of motion prediction. An extension of the “Vector-Network” method to rigid body systems in 3-D is introduced. This procedure, with its computational implementation, is shown to eliminate the work of analytically modelling a dynamic system in order to generate its time response. The entire procedure (Vector-Network) is a basic application of concepts of graph theory in which laws of vector dynamics are combined. The principle of orthogonality is reviewed and a specific application to the generation of equations of motion is presented. Moreover, various new terminal equations are shown to be necessary in the derivation of this algorithm. It is observed that this procedure is very attractive and may prove to be helpful due to its simplicity and basic application of Newton's law.     

Total dose and transient radiation effects on GaAs MMICs

To elucidate the effects of radiation on GaAs monolithic microwave integrated circuits (MMICs), radiation-induced changes in DC parameters of test FETs and in the measured microwave performance of MMICs were compared. Changes in material parameters determined from the DC results were used to model the observed microwave performance degradation. In addition, the effect of accumulated radiation damage in MMICs was studied in terms of the amplifier response to transient radiation pulses. The effect of 1-MeV electron irradiation on microwave response and transient radiation pulse response was measured in 0.5- to 12.5-GHz distributed amplifiers (ion-implanted) and in 28-GHz power amplifiers (with epitaxially grown active layers)