Anisotrophy control of Ni-Fe films through sequenced-field deposition

Anisotropy of nickel-iron films of 82, 74, and 66 per cent nickel compositions was controlled by time-sequenced application of orthogonal fields during deposition. Resulting anisotropy values are in agreement with simpleM-induced anisotropy principles. Coercive forces show small but definite decrease with anisotropy constant. Dispersion angle is proportional to the reciprocal of the anisotropy constant. The technique is suitable for production of low-Hkfilms. It permits nonanomalous inverted films to be produced and allows the study of other anisotropy sources.     

A method for measurement of "Creep" in thin magnetic films

The "creep" phenomenon in thin magnetic films is measured using a field consisting of a static field parallel to the film's easy axis, and a high-frequency sinusoidal field along the transverse axis. A special field-gradient coil is used to establish a two-domain magnetization configuration in the film plane, and the Kerr magneto-optic effect is employed to measure the position of the disturbed domain wall. Measurements on Ni-Fe-Co and NiFe alloy films show the typically sharp threshold field below which there is no wall creep; nonuniform creep gives evidence for wall "pinning" phenomena. With the method described for field calibration and the simple form of fields employed, this procedure should be valuable in establishing comparative creep sensitivity data for films formed from different alloys or by different technologies.     

Genetic control of social organization in an ant

A central issue in evolutionary biology is the extent to which complex social organization is under genetic control. We have found that a single genomic element marked by the protein-encoding gene Gp-9 is responsible for the existence of two distinct forms of social organization in the fire ant Solenopsis invicta. This genetic factor influences the reproductive phenotypes and behavioral strategies of queens and determines whether workers tolerate a single fertile queen or multiple queens per colony. Furthermore, this factor affects worker tolerance of queens with alternate genotypes, thus explaining the dramatic differences in Gp-9 allele frequencies observed between the two social forms in the wild. These findings reveal how a single genetic factor can have major effects on complex social behavior and influence the nature of social organization.     

Toxic effect of systemic administration of low doses of the plasticizer di-(2-ethyl hexyl) phthalate [DEHP] in rats

A spreadsheet model of a circle breathing system and a 70-kg anaesthetised 'standard man' has been used to simulate the first 20 min of low-flow anaesthesia with halothane, enflurane, isoflurane, sevoflurane and desflurane in oxygen. It is shown that, with the fresh-gas flow set initially equal to the total ventilation and the fresh-gas partial pressure to 3 MAC, the end-expired partial pressure can be raised to 1 MAC in 1 min with desflurane and sevoflurane, 1.5 min with isoflurane, 2.5 min with enflurane and 4 min with halothane. Sequences of lower fresh-gas flow and partial pressure settings are given for then maintaining 1 MAC end-expired partial pressure, with a minimum usage of anaesthetic, e.g. 13 ml of liquid desflurane in 20 min (of which only 33% is taken up by the patient) if the minimum acceptable flow is 11.min-1, or 8 ml (with 57% in the patient) if the minimum is 250 ml.min-1.     

TEM Observation of Crack- and Pit-Shaped Defects in Electrically Degraded GaN HEMTs

AlGaN/GaN high-electron mobility transistors stressed under dc bias at various channel temperatures were studied using transmission electron microscopy for evidence of physical damage. Stressed devices consistently developed crack- and pit-shaped defects in the AlGaN/GaN crystal material under the drain-side edge of the gate, whereas side-by-side as-processed unstressed devices did not show these features. Furthermore, the amount of physical damage was found to correlate to the amount of electrical degradation as measured by the change in IDmax from before and after stress. The formation of these defects is consistent with the theory of damage from the inverse piezoelectric effect.