Transconductance and mobility of Si:B delta MOSFETs

Delta-doped MOSFETs have been fabricated in MBE-grown silicon using for the first time boron as the dopant within the delta layer. Current-voltage characteristics have been measured, and secondary ion mass spectrometry (SIMS) is used to confirm the location of the delta layer and the extent of layer broadening by diffusion during processing. Precise threshold voltages of the devices are difficult to determine since the devices (which all operate in depletion mode) take several volts to switch off. Transconductances of the devices have been measured, and it is shown how analysis of these results can yield estimates of the carrier mobility for transport along the delta layers despite the uncertainty in the threshold voltage. A clear transition is observed in the results which is attributed to the formation of a parasitic surface-channel field-effect transistor, providing conclusive evidence that the devices are conducting along a delta channel for part of the measured range of applied gate biases     

DASD trends: cost, performance, and form factor

By examining trends in disk technology, performance, reliability, and price and comparing those trends to those of competing technologies, the authors conclude that magnetic disks will be useful for the foreseeable future. Key to the survival of magnetic disks is the use of low-cost logic and memory to enhance the performance and function of the disk subsystem, and rapid adaptation of disk technology to the changing requirements for storage     

Optical quality GaInAs grown by molecular beam epitaxy

Ga₄₇In₅₃As films have been grown by molecular beam epitaxy (MBE) on InP substrates. The unintentionally doped material has a free electron concentration of 8 × 10¹⁵cm^-3 and exhibits sharp (~5 meV linewidth) exciton recombination in the 4K photoluminescence. The films were grown on (100) InP surfaces which were thermally cleaned in the arsenic beam. The effects of the substrate temperature during growth, the Ga to In flux ratio and the group V to group III flux ratio on the 4K photoluminescence are reported.     

~1.40 eV emission band in GaAs

Photoluminescence techniques have been used to detect and characterise the ~ 1.40 eV emission band in an Mn-doped GaAs MBE epilayer and heated semi-insulating Cr-doped GaAs. An activation energy ~ 110 ± 5 meV is obtained from the temperature quenching of the emission intensity, and evidence indicated that physical movement of the Mn atom is responsible for type conversion.     

The roles of nitrogen,phosphorus and Potassium in the production of sugarcane in South Africa

The amounts of N and K fertilizers used in the South African sugar industry have increased dramatically in the past four decades, due partly to an increase in the area under sugarcane but also to large increases in the amounts of N and K fertilizers applied per hectare. There has also been an increase in the amount of P fertilizer used but this has been more gradual. The main fertilizer carriers for cane and their relative efficiency are discussed. During this period there has been considerable research into the nutrient requirements of sugarcane. Correlations established between soil and leaf analysis and crop responses to N, P and K fertilizers, and their effects on cane quality, are reviewed. While fertilizer recommendations based on soil and leaf analysis have provided a useful guide for determining the nutrient requirements of cane, they are continually being modified in the light of current research.     

Factoring Algorithms for Computing K-Terminal Network Reliability

Let GK denote a graph G whose edges can fail and with a set K ? V specified. Edge failures are independent and have known probabilities. The K-terminal reliability of GK, R(GK), is the probability that all vertices in K are connected by working edges. A factoring algorithm for computing network reliability recursively applies the formula R(GK) = piR(GK * ei) + qiR(GK - ei) where GK * ei is GK, with edge ei contracted, GK - ei is GK with ei deleted and pi ? 1 - qi is the reliability of edge ei. Various reliability-preserving reductions can be performed after each factoring operation in order to reduce computation. A unified framework is provided for complexity analysis and for determining optimal factoring strategies. Recent results are reviewed and extended within this framework.     

Metatarsus varus corrected by open wedge osteotomy of the first cuneiform bone

The persistence of metatarsus adductus varus has been a problem in management. We have treated a series of selected patients with this problem and believe that our results have been better than with the procedure we have used in the past. Fowler has described a procedure which seems ideal for the patients in our series. Through personal communication the procedure and its application were discussed and the series was started eight years ago. Our series is small because our patients are responding to other forms of treatment at an earlier age. The few that do not respond are now considered for the operation described. The procedure is relatively simple to perform. Full correction should be obtained at the time of surgery. Casting is utilized to hold the correction and immobilize the extremity for healing. Our unsatisfactory results occurred because of errors in technique or poor selection of patients. We believe that this procedure should be considered in the older patient with metatarsus varus.     

Antipyrine: radioimmunoassay in plasma and saliva following administration of a high dose and a low dose

The body's equilibrium is possible thanks to the integration of skeletal structure, vertebrae, ligaments and muscles to form one functional unity. The forces which determine posture are composed of two complementary systems, the ligamentary and the muscular systems, which together determine a dynamic act of balance. The ligaments operate mainly against the visco-hydraulic pressure of the nucleus pulposus and bind the vertebral bodies together, whereas the muscles exhibit an antigravity function and support spinal stability. A mathematical model based on a mixed theory of directed and oriented curves is proposed. Through this model it is possible to develop an exact theory governing the deformation of the ligamentous spine. This theory should be universal in the sense that it can be used to supply the spine in any of its environments.     

Comparative study of two systems for detecting becteraemia and septicaemia

Two blood culturing systems were compared in parallel-a semi-automated radiometric method, BACTEC1, and the conventional method used in our laboratory. BACTEC contains radioactive 14C labelled substrates and monitors the level of 14CO2 evolved by actively metabolizing bacteria. BACTEC was as efficient as the conventional method in detecting positive cultures and indicated that it was superior in detecting positive cultures earlier than the conventional system.