A software architecture for workstations supporting multimediaconferencing in packet switching networks

The software architecture of a multimedia workstation connected to an experimental packet switching network which is capable of switching voice, data, and video simultaneously is described. The user of a multimedia workstation may engage in several multimedia calls, each using multiple information streams consisting of voice, data, and images. The network interface software in the workstation maintains the temporal relationship among a given call's information streams. For each call, the network interface provides a multiple information channel interface to upper layer software supporting the notion of a multimedia virtual circuit. A connector mechanism is provided to control the information exchange among the network interface, the various voice, data, and image peripherals, and the computer programs used in a multimedia application. These information sources and sinks share a common abstraction called active devices     

Historic and future health promotion contexts for nursing

Lumbar artery aneurysms are uncommon lesions that usually present as pseudoaneurysms secondary to vessel injury. Despite their small size and retroperitoneal location, these lesions are potentially lethal once they rupture. This report describes a ruptured lumbar artery aneurysm which was successfully treated in a minimally invasive fashion. The diagnosis was suggested by computed tomography scan and confirmed with angiography. Successful treatment consisted of placing intravascular metallic coils into the lumbar artery. The literature contains only seven previous reports of ruptured lumbar artery aneurysms and these were managed either operatively or via an endovascular approach. Based upon the outcome of all reported cases, we believe that coil embolization of lumbar artery aneurysms following diagnostic angiography is an appropriate and effective mean of treating these lesions.     

Cadmium intake and cadmium in the human kidney

The diet and cigarette smoking are the main sources of cadmium intake in people not occupationally exposed to cadmium. Using data gathered from the literature, it is shown that there is a statistically significant relationship between the average cadmium intake in various countries and the average kidney cadmium concentration in 40-60 year old people living in those countries. It is estimated that a regular dietary intake of cadmium of 175 micrograms/day would cause the concentration of cadmium in the renal cortex to reach the critical level in 50 years.     

Effects of local hyperthermia on the pharmacokinetics of misonidazole in the anaesthetized mouse

The effects of sodium pentobarbitone anaesthesia, the presence of a tumour, and local hyperthermia to a tumour-bearing leg, on the pharmacokinetics of MISO in the mouse are reported. Analysis of MISO and its metabolite Ro 05-9963 was by high-performance liquid chromatography. The plasma kinetics of MISO were largely unaffected by any of these treatments, but hyperthermia substantially reduced tumour concentrations of the drug. The effects of tumour site and size on unheated-tumour drug concentrations were also studied, and an increase in tumour size was shown to decrease tumour MISO levels, but to different degrees according to whether implanted in the leg or flank. Uniformity of MISO distribution throughout heated and unheated tumours was examined, and levels were found to be constant within tumours. The presence of a temperature detector in heated tumours did not affect their drug concentration.     

Study of the extrusion of a typical pitch mesophase and the nature of the cokes derived therefrom

It is shown that the mesomorphic state of a typical pitch (Ashland 240), immediately prior to coking, can be extruded to produce a specified coke morphology. The rheology of the extrudate, the degree of preferred orientation induced and the nature of the cokes derived therefrom vary enormously depending on the thermal history of the pyrolysate. The extrudates and derived cokes are characterized by dilatometry and X-ray diffraction.     

Some examples of generalized cassegrainian and gregorian antennas

Some theoretical generalizations are given of two-reflector, rotationally symmetric microwave antennas fed by a plane wave across the feed aperture. So far as geometrical optics apply, the proposed designs offer 1) no reflection of energy back into the feed and 2) arbitrary illumination over the antenna aperture. The general solution is exhibited in terms of quadratures, and the reflector shapes for some simple cases are worked out in detail and plotted. Two families of antennas are found which image the feed aperture onto the secondary reflector. These antennas might be expected to have low spillover losses due to diffraction, but none of them is of practical proportions. It is shown in general that such imaging is incompatible with efficient illumination of the secondary aperture.     

Reactivity ratios for the copolymerization systems styrenep-ethoxystyrene and methyl methacrylatep-ethoxystyrene

Reactivity ratios for the systems $\text{styrene}\text{p-}\text{ethoxystyrene}$ and methyl $\text{methacrylate}\text{p-}\text{ethoxystyrene}$ have been determined at 50°C. The values found by the computational method of Tidwell and Mortimer were 1.08 and 0.74 for the first system, and 0.37 and 0.24 for the second; the 90% joint confidence limit envelopes were also calculated.     

High-frequency time-ratio control with insulated and isolated inputs

Fast-responding amplifiers are needed in many industrial and defense systems. Systems using power amplifiers with one to 1000 watts of output dc power require high performance. The requirements often include high efficiency, light weight, compactness, high reliability, economy, and simplicity, along with fast response and insulated multiple inputs. These performances are required in applications such as controls for high-power inverters and converters, motors, generators, light, heat, dc-to-ac inverters, power supplies, servo systems, etc. This paper presents a transistor-magnetic power amplifier with multiple insulated and isolated inputs (Fig. 1) with characteristics in Fig. 2. The technique of time-ratio control [1] is used to provide light weight, compactness, high efficiency, and high reliability. High-speed power transistors (0.1 μs) combined with a tunnel diode circuit permit high chopping frequency (50 kc). The base current of the power transistor is switched in-less than 0.02 μs. Insulated and isolated inputs are provided by a small saturable transformer the size of a TO-5 transistor case. Transistor inputs are used on the saturable transformer. Germanium power transistors (such as 2N1907) are used to provide economy, but silicon transistors can be used for applications at high ambient temperature. The circuit of Fig. 1 is used to fire controlled rectifiers for inverters and converters. A pulse transformer in series with a resistor replaces the load of Fig. 1 when needed in firing circuits. A simple time-ratio control (TRC) circuit is presented that controls the output [Fig. 2(a)] by varying the chopping frequency from 50 kc to 5 kc. The multiple inputs are illustrated. A constant frequency (50 kc) TRC is presented that controls load voltage from zero to the supply voltage [Fig. 2(b)]. The output responds to the control signal in 40 μs. The tunnel diode switching circuit is also presented.