Theoretical model for intermeshing twin screw extruders: Axial velocity profile for shallow channels

Positive displacement intermeshing twin screw extruders have been analyzed by a simple model for flow in the channel formed by the screw root and screw flights. The model considers the down channel flow to be a combination of drage flow resulting from the relative motion of the barrel and screw and pressure flow resulting from the positive displacement action of the device. The pressure flow in this situation is distinguished from pressure flow in a single screw extruder in that the pressure forces induce flow toward the die for the twin screw model rather than away from the die as in a single screw extruder. Comparison of the down channel shear rate profile of apositive displacement twin screw extruder with that of a single screw extruder with no net flow reveals that they are identical but inverted with respect to channel depth. The model presented does not consider leakage between the twin screws or the rotational motion of the second screw.     

Overlooking the incongruent: Categorization biases in the identification of political statements.

To explore factors affecting memory for statements expounding political positions, 2 experiments examined source attribution for 1-sentence political statements embedded in either congruent or incongruent contexts. In Exp I, 28 female undergraduates who were active in a campus feminist group and 26 who were not read essays by 4 writers of differing overall viewpoints on feminism; in Exp II, 32 undergraduates who were active in the anti-nuclear-power movement and 32 who were not read similar essays about nuclear power. Analysis revealed a pronounced "congruency bias"—both superior recognition memory and more accurate attribution to source for statements embodying a position consistent with the global position of the source. Among incongruent statements, however, there was significantly better source memory for statements that represented extreme, rather than moderate, departures from the overall position of the writer, an effect attributable in part to the greater salience of extremely incongruent items. There was also significantly better source attribution for statements made by writers whose global positions were relatively congenial to Ss and for statements embodying either minority positions or extreme versions of majority views. These effects were not moderated by either intensity of Ss' attitudes or instructions that specifically requested Ss to remember incongruent items. An extension of these studies that adjusted for response bias by transforming the source attribution dependent variable is appended. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Electrical Response of the Human Eye to Sinusoidal Light Stimulation

In order to extract maximum information from electroretingraphic waveforms obtained under clinical conditions, it is necessary to have reliable quantitative methods to characterize both the amplitude and shape of these waveforms. When sinusoidally modulated light is used to stimulate the retina, the resulting ERG potentials are, in general, not sinusoidal due to the nonlinearities in the system. However, the responses are very reproducible and can easily be characterized by a few parameters based on a Fourier analysis. The more conventional flash ERG, although usually of higher amplitude, is much less reproducible in shape and needs many more parameters to characterize completely. Amplitude and phase characteristics can be understood on the basis of a simple model for the scotopic B-wave system and additive interaction by the photopic system. Changes in amplitude and phase characteristics with various experimental conditions could be predicted and were confirmed by subsequent experiments. The ultimate goal of this work is to improve the quantitative basis for clinical electroretinography and to provide the clinician with additional data which can be useful in the diagnosis of retinal diseases.     

Neural pulse frequency modulation of an exponentially correlated Gaussian process

When the input to a Neural Pulse Frequency Modulation (NPFM) system is a stationary random process the output takes the form of a train of impulses for which the occurrence times and the intensities are stationary processes of a discrete type. Particularly, the impulse occurrence times constitute a stationary point process where the average impulse frequency (average number of impulses per unit time) becomes a reciprocal of the mean impulse period. Due to the inherent nature of the modulation procedure the determination of the mean impulse period transforms to a problem of computing the mean first passage time of a random process which is not necessarily Markovian. In this paper numerical solutions of the average impulse frequency of a Neural Pulse Frequency Modulation System are obtained for the case of an exponentially correlated Gaussian input. Monte Carlo computer simulations substantiate the theoretically obtained results.     

Nitrogen-15 in apple nutrition investigations

Young apple trees growing in pots of soil were treated with N-15 labelled potassium nitrate or urea at different times of year. Over periods of several months whole trees were harvested and divided into their component tissues for total N and N-15 analyses; the latter were carried out using an emission spectrometer. Following treatments in mid-October 1972 and harvest in the following February, about 16% of N-15 from soil-applied nitrate and almost 47% of that from leafapplied urea was recovered in the trees. A later harvest in May 1973 showed that by then one-third to one-half of this fertiliser N had been translocated to the new leaves. Soil applications of nitrate were also made in March or August 1973 and the maximum recoveries of fertiliser N were about 40% and 60% respectively, much of which was in the leaves. In the fruit from the March-N trees, seeds and flesh were almost equally labelled but in that from the August-treated trees the seeds contained no excess N-15, although there was a considerable concentration in the flesh. Urea foliar sprays were also made in June or August 1973. The distributions of isotope were very similar following these treatments, in that the greater part remained in the leaves. The results are discussed in relation to previously published work on N in apple trees, with particular emphasis on the advantages in using N-15 to follow unambiguously the movement of N between the tissues of the tree.     

Resource recovery: Use of a group contingency to increase paper recycling in an elementary school.

Recycling has been suggested as a means for replenishing dwindling energy supplies, reducing solid waste accumulation, and conserving natural resource bases. In the present study, the rates of newspaper recycling in 10 classrooms totaling 271 1st–6th graders were measured for 9? wks when a verbal appeal was made to students and when prizes were awarded to participating members of 3 classes recycling the most paper. 792 lb (359 kg) of newspaper were collected when the verbal appeal was made, and 14,298 lb (6,486 kg) were collected when prizes were forthcoming. The impact that newspaper recycling has on energy consumption was estimated, and the advantage of using the school system as an "agent" for wide-scale recycling operations is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)