Preset Threshold Value Research Articles

Operant slowing of the extension phase of the reaching movement in rats

Motor learning was studied in rats (n=8) trained to slow down the forepaw extension while reaching into a narrow tube equipped with an axially moving piston. The photoelectrically monitored velocity of the movement between points P1, P2 and P3 (13.0, 15.1 and 17.3 mm from tube entrance) was evaluated with a laboratory computer which also plotted distributions of the corresponding time intervals and delivered food pellets whenever the time interval between P1 and P2 exceeded a preset threshold value (Group I). The additional condition of attaining P3 was required in Group II. Marked prolongation of the P1-P2 interval required about 20 sessions of 512 reaches in Group I and 27 to 30 sessions in Group II. The rats prolonged the P1-P2 interval in two ways: (a) By generating movements the amplitude of which oscillated around the P2 level and thus exposed the P2 sensor to the slow terminal part of the movement; (b) By true velocity decrease in the middle part (P1-P2) of the movements attaining the level P3. It is concluded that reaching is a highly stereotyped instrumental reaction, the pattern of which is not easily modified by operant conditioning. Substantial slowing (2 times) of the ballistic extension phase of long reaches probably reflects programmed coactivation of the antagonist.

Cycle detection: a technique for estimating the frequency and amplitude of episodic fluctuations in blood hormone and substrate concentrations.

Investigation of episodic endocrine secretion has been hampered by inadequate analytical techniques for describing patterns of blood concentrations over time. Although standard time series methods, such as autocorrelation and power spectral analysis, are available, their use is limited to special cases in which rhythms are regular. To facilitate the analysis of our own episodic LH data, we have developed a process for determining the frequency and amplitude of both regular and irregular endocrine rhythms (signals) in the presence of high levels of random measurement errors (noise). This process, called cycle detection, engages an iterative, computerized procedure which scans data identifying sequential increases and decreases greater than an initial, preset threshold value. One complete cycle is defined as two increases greater than threshold separated by a decrease which is also greater than threshold. For an initial first pass estimate of frequency and amplitude, the threshold is set at 2.7 times the noise standard deviation. On the next pass, the threshold is readjusted, based on an empirically derived formula, and the data are scanned again. This process is repeated until the threshold reaches a stable value. We have tested the reliability of the cycle detection process by simulating irregular rhythm fluctuations of different frequencies, corrupted by various levels of noise and evaluating the signal characteristics with cycle detection analysis. These tests indicate that cycle detection provides excellent estimates of cycle frequency and amplitude, even with signal to noise ratios as low as 1.5. The ability of this process to analyze cyclic signals of almost any shape, with either regular or irregular rhythms, should make it a valuable tool in the hands of endocrine researchers.

Increases in skin resistance of white rats following scopolamine injection

Thirty-six male albino rats were injected with either saline or 0.6 mg/kg scopolamine and placed on a metal grid. The grid was wired to a transistor-biased detector which determined, every second, whether the subject's resistance was above or below a preset threshold value. Over test sessions of five minutes, drug subject's resistances were above each of the three threshold values used (5, 10, 15 megohms) for significantly longer than those of control subjects. Scopolamine treated rats would therefore receive lower shock levels than control subjects in a shock experiment.

Feedback signal based upon force and time delay: modification of the Krusen Limb Load Monitor.

Recently a device has been developed to augment sensory feedback during weight-bearing activities.1 The Krusen Limb Load Monitor (Model 101)* consists of a force transducer housed within a footplate (foreground, Fig. 1) placed in the sole of a shoe. The footplate is connected to the limb-load monitor (LLM) by a coaxial cable. An audio tone can be emitted through an amplifier placed within the LLM when force upon the plate reaches a preset (threshold) value. Through training by shaping responses to attempts at symmetrical standing, some hemiplegic patients can correct their static limb loading patterns2 and possibly retain these corrected patterns once feedback has been withdrawn.3 The LLM can be used either as a force-feedback device for weight-shifting activities during stance or, by adding our time delay modification† (right, Fig. 1), for feedback to the existing force-sensing component.…

A closed-loop electro-magnetic flowmeter

In applications requiring long-term in situ measurements, or in the operation of remote sensors as in meteorology and oceanography, power-conserving circuits are especially advantageous. The closed-loop circuit described adjusts the coil power of an electromagnetic flowmeter when flow velocities exceed a preset threshold value. As a consequence, electrical power is saved.

A new instrument system to investigate sediment dynamics on continental shelves

A new instrumented tripod, the GEOPROBE system, has been constructed and used to collect time-series data on physical and geological parameters that are important in bottom sediment dynamics on continental shelves. Simultaneous in situ digital recording of pressure, temperature, light scattering, and light transmission, in combination with current velocity profiles measured with a near-bottom vertical array of electromagnetic current meters, is used to correlate bottom shear generated by a variety of oceanic processes (waves, tides, mean flow, etc.) with incipient movement and resuspension of bottom sediment. A bottom camera system that is activated when current speeds exceed preset threshold values provides a unique method to identify initial sediment motion and bed form development. Data from a twenty day deployment of the GEOPROBE system in Norton Sound, Alaska, during the period September 24 – October 14, 1976 show that threshold conditions for sediment movement are commonly exceeded, even in calm weather periods, due to the additive effects of tidal currents, mean circulation, and surface waves.

The Optimal Adaptive Sampled-Data Regulator

The optimal control problem for sampled-data processes in which sampling is not triggered by a timer, but occurs when one or more outputs attain preset threshold values is formulated as an adaptive optimal sampled-data regulator problem. Both open loop and closed loop solutions are determined and a comparison of a system’s performance with adaptive and with periodic sampling is presented.

Radium in Great Britain

For the original verification method of screen spatial location parameters of sky screen target is complex and low efficiency, the new verification device without disassembly the sky screen target is designed in this paper. The stroboscopic light sources including the LED, collimating lens, frosted glass and small aperture are designed, and the datum plane is precisely established. By setting the threshold method of oscilloscope, the translation stage moving distance relative to the datum plane are recorded, when the amplitude of the output signal of the sky screen target just reaches the preset threshold value. According to the formula, the screen spatial location parameters of sky screen target are achieved. Experimental results show that the calibration accuracy of screen surface space position parameters is better than ±1′, which is consistent with the theoretical error analysis. This verification device makes up for original verification deficiencies of disassembly sky screen target, saves test time, increases the verification efficiency of sky screen target, and has a broad range market demand.