Potential Of System Research Articles

Homogeneous populations of Artemia nauplii and their potential use for in vitro testing in developmental toxicology.

Efforts have begun to establish test subjects other than the intact pregnant mammal to serve as models for rapid teratology screens. Artemia nauplii transcending instar I to later instars were examined to determine their potential for indicating chemicals as potential developmental hazards and thus prioritizing them for more extensive in vivo testing. Several criteria selected for assessing the system's potential for screening were the ability to: collect homogeneous populations of instar I nauplii; characterize intermediate development by technically simple measurements; and demonstrate development-related differentials in naupliar vulnerability. Homogeneous populations of nauplii were harvested from a flow-through hatching and cold storage system. Nauplii accumulated in the system are stored at 4 degrees C in a quiescent state with little physical (body length, body water volume) and biochemical (DNA and protein levels) change and thus are maintained at instar I. Intermediate development of nauplii transcending instar I to IV was characterized after the onset of 25 degrees C incubation by measuring changes in drinking activity, body length, body water volume, and DNA and protein levels. During the first day of incubation, development was greatest between 6 and 24 hours of incubation. Development-related differentials in naupliar vulnerability were shown by comparing median lethal concentrations (LC50) estimated for cadmium sulfate (CdSO4), mercuric chloride (HgCl2), and sodium azide (NaN3) at various times during incubation. With cadmium and mercury, LC50s decreased as nauplii aged and developed; whereas, with azide, LC50s did not vary. Developing nauplii were differentially vulnerable to cadmium and inorganic mercury. Artemia nauplii transcending instar I to IV appear useful for indicating chemicals that preferentially interact with developmental events.

Effect of Fluid-to-Structure Heat Transfer on the Structural Damage Potential to a Liquid-Metal Fast Breeder Reactor

Deterministic calculations simulating a hypothetical accident in a liquid-metal fast breeder reactor that leads to a hydrodynamic disassembly of the core have been carried out to estimate the system's damage potential due to the vapor-pressure-driven expansion of molten core material and its dependency on the heat transfer to the remaining structure. These calculations ignored the effect on the work potential of sodium left in the core during the disassembly. Results indicate that steel cladding in the upper axial blankets and fission gas plenum acts as a thermodynamic energy sink that could reduce the total thermodynamic work energy by between one and two orders of magnitude, provided little or no sodium is present in the core at the time of interaction. These results have been found to be insensitive to the rate of heat transferred from the molten fuel to the molten steel that comprises the molten core material.

Effects of Radial Appendage Flexibility on Shaft Whirl Stability

Introduction T move to lighter, more flexible gas turbine engine components has initiated several recent investigations into the effects of component flexibility on shaft whirl. Based on a study of a flexible shaft-disk model, Chivens and Nelson concluded that critical speeds are not affected significantly by disk flexibility. Some limitations concerning this conclusion have been discussed by Klompas. The object of this Note is to show that, provided that a sufficiently wide range of parameters is considered, the effects of an appendage's flexibility on critical speeds can become significant. Critical speed stability boundaries are shown to reduce to the expected limiting cases of a shaft containing rigid appendages as the appendage's stiffness increases, and to an elastic shaft with a concentrated mass at the point of appendage attachment when the appendage's stiffness decreases. Stability boundaries are obtained by a Liapunov analysis in which the system's dynamic potential serves as a Liapunov testing function.

Novel frequency-analysis system for a vibrotactile speech training aid for the deaf

The paper is about the design of a novel speech processor and its successful incorporation in a vibrotactile speech training aid for the deaf. The introduction makes clear the particular difficulties and needs of the deaf child who is learning to speak. The discussion shows that to help with the deaf child's difficulty with mimicry the technologist must enable the child to sense and compare patterns of articulator configurations. It is suggested that the vocal gestures will be monitored most easily if the speech processor operates in such a way as to ignore variations in speech intensity. An explanation is given of a novel amplitude insensitive filtering system which employs a bank of high-pass filters. A particular requirement of the system is for the measurement of the ratio of two voltages each of which can vary over a wide dynamic range; a circuit for this is presented. Although the discussion focuses on the application of the frequency-analysis system to speech processing the theoretical treatment facilitates the evaluation of the system's potential for processing other signals.

Roentgen video-absorptiometry

Discusses the feasibility of performing absorptiometric measurements using a televised image-intensified fluoroscopic system. The system consists of an X-ray generator, image intensifier, TV camera and A/D convertor under computer control for digitizing the video signals. Preliminary experiments have been performed to evaluate the system's potential for determining the mass of bone mineral in the axial skeleton in vivo. All absorptiometric measurements were made in 15-20 cm of water using small field sizes of about 5*7 cm to reduce scatter. Phantoms of bone equivalent material representing vertebral bodies with different amounts of cone mineral were measured. The correlation coefficient between the actual and the measured mass was 0.98 and the standard error was 5.5%. The effect of beam hardening is described.

The unit system: current staff attitudes and future directions.

The geographic unit system, with its concept of equal treatment for all mental patients, has been widely adopted by psychiatric hospitals. By bringing acute and chronic patients together and exposing the latter to a large number of high-quality staff members, it has contributed materially to the return of long-term patients to the community. However, the release-oriented benefits of the system may now be leveling off, and criticism of it is increasing, particularly from proponents of specialized treatment programs. The authors describe the development of a typical unit system, report findings of two surveys of current staff attitudes, and discuss the system's past contributions and potential.

An Approach to Architectural Education

There have been numerous approaches to the student teacher relationship, and I would like to add to this list one particularly suited to the teaching of architecture.1 In it, the student working on an architectural problem is viewed as a system which the teacher is using to investigate various possibilities in the problem solution. The implications of this attitude are numerous. For one thing, the success of the teacher can be judged by the results of work done by his student problem system. High quality results should be expected because students are obviously the most flexible problem solving systems in existence and problems are chosen freely. Modern teaching theory reveals many inherent responsibilities in this approach. One of these is the need for a fairly complete understanding of each student and his capabilities.2 As with a computer, one cannot expect useful results without knowing the capacity of the system or the language it uses to understand and work with given problems. In fact, it is imperative to put problem solving language into either system if one expects to obtain useful results. The teacher is also responsible for maintaining the versatility of the problem solving system or enhancing its versatility to make it more useful. There are numerous reasons for this aside from the most obvious humanitarian ones.3 The sheer cost of a student problem solving system demands its use to the fullest extent. One would not buy an expensive camera and intentionally scratch the lens or add a restrictive gadget that could not be removed. This would effectively ruin the resale value of the camera and would also severely limit one's use of it in the larger field of photography. This seems obvious, but when viewing educational systems we can see similar restrictions developing in students because we have not been able to design an education that is expanding and self-reinforcing. Instead, many educational systems limit students' functional capabilities to very specific problem types, thereby reducing the system's total potential. There are several things that must be kept in mind when a teacher of architecture goes about developing the capabilities of his student problem system. First of all, there should be an overall purpose for the system, as broadly defined as possible. I suggest the minimum definition encompass the following goals:

Pulsed Laser Imaging System for Direct Visualization of Ultrasonic Waveforms

A pulsed laser with an extremely short pulse duration (≈3 nsec) has been used in a schlieren system to resolve individual wavefronts within high-frequency pulse trains. Wavefronts have been resolved at frequencies of 1–20 MHz. The system and its components are briefly described; photographs of basic ultrasonic wave propagation effects such as refraction, diffraction, and distortion in liquids are shown. Several possible applications to acoustic problems such as lens design, transducer and transducer array evaluation, critical effects, and propagation in biological specimens are discussed. The system's potential as a very graphic teaching aid is presented.

Experiments on Magnetic Tape Readout with an Electron Beam

The electron beam, due to its freedom from inertia' can be made to keep its proper position to recorded information regardless of any deformation experienced by the recording medium in the interval between the recording and the reproduction. In the beam readout system described in this paper, the magnetic tape is bent over a cylinder and the electron beam is made to pass across the recorded track. The electrons close to the tape form a cycloid pattern. This pattern is deflected across the entrance slit of a Faraday collector, thereby producing an output signal corresponding to the recorded information. At present, some practical limitations prevent the full realization of the system's potential. The ultimate limitation is the shot noise of the electrons. Theoretical considerations indicate that a 3-Mc-wide video signal, for example, if suitably recorded, could be reproduced with a signal-to-shot-noise ratio of 30 db and with an area packing density of 0.85 cycle per square mil.