Electrical analogue for a partial differential equation

The electrical analogue provides a useful approach to the solution of Partial Differential Equations. A general purpose analogue for PDEs would be a useful peripheral for a small digital computer, enabling it to handle quickly, cheaply and with reasonable accuracy problems which otherwise require substantial computational time on large machines.In this paper the author discusses the design of an analogue for ?²U + U_x = 0, suitable for further extension as a computer controlled general analogue. It is shown that AC networks, using capacitors as passive elements, offer substantial advantages over other analogues. The use of buffer amplifiers at each node greatly simplifies the unilateral impedance problem, but introduces unidirectional error components. These errors are analysed, and specifications for suitable amplifiers are obtainedExperimental results on small (20 node, 90 node) models confirm the satisfactory performance of the analogue, and the author predicts that large scale (> 900 nodes) models will yield results accurate to better than 99.9%, with less than 100 ms settling times     

Physiologic effects of a self-contained self-rescuer

Recently promulgated federal regulations mandate the provision of an emergency, self-contained, oxygen-supplying breathing device (self-contained self-rescuer, SCSR) to all underground coalminers. In order to assist in defining the potential limitations of this new device, we measured the responses of ten healthy coal mine inspectors to submaximal steady-state treadmill exercise with and without the SCSR. During the last minute of exercise, blood oxygen saturation averaged 98.3% and mouth pressure swing 15.6 cm H2O with the device, compared to 94.8% and 10.4 cm H2O without it. Mean respiratory rates were decreased to 25/min with the SCSR from 28/min without it. Blood pressure, core temperature and heart rate were unaffected. We conclude that in healthy individuals on submaximal exercise there is little evidence of a significant adverse effect of the new device.     

`Early-intercept voltage?: a parameter of voltage-driven b.j.t.s

Experimental measurements support a theoretical argument suggesting that if the collector current of a b.j.t. is plotted against collector-base voltage, for set values of base-emitter drive voltage, then the tangents to the characteristics at a given collector-base voltage, in the forward-active region, have a common intersection point on the collector-base voltage axis. The usefulness of this parameter, designated the early-intercept voltage, in the analysis of some linear i.e. schemes is mentioned.     

Reversal of pretreatment hypotension and control of hemorrhage in trauma patients by a simple device

The injection of a suspension of Walker 256 carcinoma cells into the carotid artery of rats produced a model of hematogenously spread cerebral metastases. Most animals died from massive extracerebral tumors of the head and jaw; brain tumors were present in only one-quarter. External carotid artery ligation prior to tumor inoculation did not increase the incidence of fatal brain tumor. When cyclophosphamide, 15 mg/kg, was injected as a single dose on the fourteenth day after tumor inoculation, most of the extracerebral tumor disappeared. Fifty percent of the animals so treated were cured of tumor, but 90% of the remainder died of large intracerebral tumors. Severe cytopathic changes resulting from cyclophosphamide were present in extracerebral or choroid plexus tumors but were mild or nonexistent in intracerebral tumors. These selective effects of cyclophosphamide suggest that water-soluble agents are less effective against tumor in the brain than against extracerebral tumors despite the fact that metastatic tumor breaks down the blood-brain barrier.     

Hematuria and sickle cell disorders

To examine the relationship between gross hematuria and sickle cell disorders, all patients admitted to Grady Memorial Hospital with the diagnosis of a sickle cell disorder during a 14-month period were reviewed. Of 115 such patients, 65% had sickle cell disease and 35% had sickle cell trait. None of the former but seven of the latter group had gross hematuria. Mean age of the seven was 30 years. Comprehensive examinations and laboratory studies showed that all were free of concomitant disease. Physical findings, diagnostic modalities, and treatment were reviewed. Findings suggest that conservative therapy (bed rest, hydration, and diuresis) is usually effective.     

Anomalous double blood supply to the lung

We report an unusual case in which an apparently normal upper lobe of the right lung was supplied by major systemic arterial and pulmonary arterial vessels. The anomalous artery arose from the descending aorta. Following interruption of this vessel, the machinery-like murmur previously present disappeared.