Heat-flow near a North Atlantic fracture zone

Fifteen new heat-flow measurements are reported, fourteen of which are located in or near a fracture zone near 43°N on the mid-Atlantic Ridge. These data, combined with earlier nearby measurements, show the fracture zone to have an observable, positive effect on the regional heat-flow field. A good correlation is observed between large near-bottom water potential temperature gradients and the occurrence of significant variations with depth in the measured rate of heat-flow. One measurement was taken in the Horseshoe abyssal plain west of Gibraltar and gave a value of 1.38 μcal/cm²s.     

Zinc therapy in acrodermatitis enteropathica

Albino Holtzman, albino Wistar and hooded HS rats were injected fortnightly for 14 weeks with human glomerular basement membrane (GBM) emulsified in Freund's complete adjuvant. Half of the rats were pretreated with Freund's complete adjuvant and some were unilaterally nephrectomized. Anti-GBM antibody glomerulonephritis, characterized by proteinuria (greater than 100 mg/16 h) and a diffuse linear deposition of host immunoglobulin along the glomerular basement membrane, was first detected in Holtzman rats 4 weeks after treatment with GBM had begun, and had developed in 69% of these rats by 15 weeks. In contrast, none of the similarly treated Wistar or HS rats became proteinuric at any time, although a few showed weak glomerular fluorescence at the end of the experiment. Thus Holtzman rats are susceptible, and HS and Wistar rats are resistant to experimental anti-GBM antibody glomerulonephritis. Pretreatment with Freund's complete adjuvant apparently shortened the induction period of the experimental disease in the Holtzman rats whereas unilateral nephrectomy appeared to decrease their susceptibility to it.     

Interpretation of non-equilibrium measurements on MOS devices using the linear voltage ramp technique

An analytical and experimental study is presented of MOS devices subjected to a linear voltage ramp such that the rate of change of voltage is sufficiently high to take the device into the non-equilibrium mode of operation. Various areas of the resulting current-voltage plots are identified with physical quantities such as gate charge and surface potential, a knowledge of which is very useful in studying non-equilibrium mechanisms. To circumvent the difficulty of tedious graphical integration involved in the process of extracting these quantities from the experimental current-voltage plots, an experimental technique is presented which facilitates the direct measurement of these quantities. The resulting plots of displacement current, surface potential and gate charge vs gate voltage are related to each other in a manner which gives interesting insight into the mechanisms occurring within the device, and agreement with the existing theories is found to be extremely good.     

Determination of bulk trap parameters using thermal dielectric relaxation techniques

A new non-steady-state technique for determining the energy levels of traps through which electron-hole pairs are generated in the depletion-layer of the silicon of metal-oxide-silicon (MOS) capacitor structures has been applied to metal-nitride-oxide-silicon (MNOS) structures. The technique consists of cooling the device to low temperatures and biasing it into the deep-depletion mode. The temperature of the device is then raised at a constant rate and the resulting I_g-T characteristic exhibits a pronounced wide peak. The energy level of the traps involved in the generation process was obtained from the slope of the log_eI_g - 1/T plot of the leading edge of the I_g-T characteristic curve, and is found to be 0·55 eV.A cross-check on the trap levels involved in the generation process was made by performing the experiment at two heating rates, β₁ and β₂. From a knowledge of the corresponding temperatures at which the maxima of the two peaks in the I_g-T characteristics occur, the energy level of the traps was found to be 0·54 eV. Furthermore, having obtained the trap level, the so-called carrier lifetime, τ, was found to be approximately 4μ sec.Experiments are described which provide convincing evidence that the generation of electron-hole pairs occurs in the depletion-layer of the silicon rather than at the silicon-silicon interface.     

Amphotericin B-induced changes in K+ content, viability, and ultrastructure of yeast-phase Histoplasma capsulatum

Yeast-phase cells of Histoplasma capsulatum were challenged with amphotericin B, and membrane perturbation was monitored by K+ efflux. Suspensions of washed cells readily absorbed about 1.12 microgram of amphotericin B per mg (dry weight) and further nonspecific sites were also apparent. The dose-response curve for initial rate of K+ efflux was sigmoidal within the range 0.1 to 1.0 microgram of amphotericin B per ml. A fungistatic concentration of amphotericin B (0.3 microgram/ml) evoked an efflux of 85 to 90% K+ from the cells within 15 min, but cell viability decreased only 13% (yeast phase) or 33% (transformed to mycelial units). Ultrastructural changes in treated cells were detected within 5 min, and the hallmark was expansion of vacuoles during the 1-h monitoring period. In contradistinction to a previous report, the appearance of the protoplasmic membrane was not altered by fungistatic concentration. When treated cells were returned to a fresh growth medium, there was a pronounced lag (20 h). During this apparent recovery phase, the large vacuoles fragmented and returned to normal size. It is proposed that vacuoles of H. capsulatum act as a spatial buffer of considerable survival value to stressed cells.     

Experimental studies of switching in metal semi-insulating n-p silicon devices

The switching properties of silicon structures comprising a p⁺-n junction and a metal electrode separated from the n-section of the p⁺-n junction by a semi-insulating (leaky) layer are presented. Two basic types of structure were studied: devices with relatively light doped n-sections, and those with relatively heavily doped sections.

The switching voltage of the first group was found to be proportional to the product of the doping density, N_d and the square of the width of the n-section, and to be only very weakly temperature-dependent. The capacitance-voltage relationship of the device in the high-impedance mode was found to be of the form C⁻¹ ∞ V^1/2, and these measurements established that switching occurred just as the depletion region of the n-section under the gate electrode reached through to the p⁺-n junction. It was thus established that these devices were operating in the punch-through mode.

In the second group of devices, the doping density of the n-section was increased by diffusing an n-well into the section. The switching properties were found to be quite different from the punch-through devices. The switching voltage was found to be independent of the width of the n-section and proportional to N_d^−3/4. Capacitance measurements also showed that the depletion region in the n-section under the oxide at switching, varied with the doping concentration, and was substantially less than the width of the n-layer. It was thus concluded that switching in these devices was of the avalanche-mode type.     

The value of a certified quality management system: the perception of internal developers

There is growing interest among internal information technology (IT) departments in implementing a certified quality management system (QMS). This paper examines the forces that have influenced organizations that supply development services to adopt QMS models and explores the relevance of these forces to internal IT developers. The perceptions of internal developers regarding the value of QMS in addressing these forces were studied using a multiple case study involving four organizations. The results suggest that while the reasons given by external developers concern mainly the marketing advantages of adopting a QMS, internal developers envisage the major advantage to be an improvement in the development process.