The absence of a solid layer of helium on alkaline earth fluoride substrates

Journal of Low Temperature Physics -     

A computer technique for the estimation of the absolute three-dimensional array of basal dendritic fields using data from projected histological sections

The standard projection methods of dendritic field analysis have revealed that dendritic density decays exponentially with increasing distance from the centre of the perikaryon and present ideas about dendritic connectivity are largely based on this theory. However, inherent in the projection method are a series of errors which have not hitherto been defined and which indicate that much of the data obtained by the projection technique may be an artefact of the method itself. However, it is possible, given the projection data from a sample of neurons, to extrapolate the three-dimensional array of dendritic fields by employing a computer technique. In this technique the perikaryon is enclosed in concentric spheres set 20 mμ apart and dendritic endings (E) and branching nodes (B) are positioned within the volume of the total sphere according to known distributions. The number of dendritic intersections (I) at the surface of the nth concentric sphere can be calculated given the number of primary dendrites from the relationship; I_{(n ? 1)} + B_n — E_n. These numbers may then be corrected for the distortion due to projection and sectioning. Comparison of these corrected data with those obtained from conventional histological methods suggests that the distribution of dendritic parameters may be quite different from the conventionally held view and that the decay of dendritic density is not exponential.     

Optimal Heterophily and Communication Effectiveness: Some Empirical Findings

A fundamental principle of human communication is that source-receiver similarity promotes communication effectiveness. But do perceived source-receiver dissimilarities have instrumental value in enhancing the effectiveness of communication? This study demonstrates the application of a method for gauging the relationship between heterophily or source-receiver dissimilarity and communication effectiveness and for identifying relevant dimensions of homophily/heterophily in achieving effective communication. One hundred ninety-two Ss viewed three slides of widely-differing college males, to whom three pre-scaled neutral statements were randomly attributed. Measures were obtained of Ss ratings of themselves and these “sources” along twenty-one personal attributes, as well as their agreement (or disagreement) with the attributed statements. Perceived source-receiver distances varied across the three sources, as did the agreement measure of communication effectiveness. The moderately-distant source achieved the highest agreement, lending support to Everett M. Rogers'notion that optimal heterophily produces communication effectiveness. The pattern and directions of the perceived dimensions of interpersonal differences gave further understanding of the relative communication effectiveness of communication sources.     

Toward a real-time model-based training system

This article describes the development of a real-time model-based training system that provides adaptive “over-the-shoulder” (OTS) instructions to trainees as they learn to perform an Anti-Air Warfare Coordinator (AAWC) task. The long-term goal is to develop a system that will provide real-time instructional materials based on learners’ actions, so that eventually the initial set of instructions on a task can be strengthened, complemented, or overridden at different stages of training. The training system is based on the ACT-R architecture, which serves as the theoretical background for the cognitive model that monitors the learning process of the trainee. An experiment was designed to study the impact of OTS instructions on learning. Results showed that while OTS instructions facilitated short-term learning, (a) they took time away from the processing of current information, (b) their effects tended to decay rapidly in initial stages of training, and (c) their effects on training diminished when the OTS instructions were proceduralized in later stages of training. A cognitive model that learned from both the upfront and OTS instructions was created and provided good fits to the learning and performance data collected from human participants. Our results suggest that to fully capture the symbiotic performance between humans and intelligent training systems, it is important to closely monitor the learning process of the trainee so that instructional interventions can be delivered effectively at different stages of training. We proposed that such a flexible system can be developed based on an adaptive cognitive model that provides real-time predictions on learning and performance.     

Does a failed quit attempt reduce cigarette consumption following resumption of smoking? The effects of time and quit attempts on the longitudinal analysis of self-reported cigarette smoking intensity.

California Tobacco Survey respondents were asked the intensity of their cigarette smoking 1 year previously and at the time of the survey. Respondents reported a generally lower smoking intensity at survey time compared with 1 year previously. Multivariable statistical models on the change in smoking intensity in the past year were fitted to assess the effects of low-tar cigarette use, a quit attempt in the past year, smoking intensity 1 year previously, and demographic variables (age, education, income, and race). The most important predictor of change in intensity was the intensity 1 year previously. The next most important predictor was whether a quit attempt had been made in the previous year. The demographic variables also were found to have a significant effect, although their effects were of smaller magnitude. Low-tar cigarette use was not a significant predictor of change in intensity in multivariable analysis. The effect of a quit attempt on the reduction in intensity of smoking suggests that periods of cessation may reduce the intensity of smoking and the level of addiction for several months following relapse. Consequently, it may be important to control for cessation activity in studies comparing exposures from conventional tobacco products to exposures from new products that purport to offer lower harm.     

Electrochemical characterization and in vivo biocompatibility of a thick-film printed sensor for continuous in vivo monitoring

This paper assessed the material biocompatibility and investigated the temporal modulation in electrochemical performance of printed thick-film electrochemical sensing devices (ESDs) that can serve as the basis of various enzymatic sensor in detecting an electrochemically potent species. The sensors were placed in phosphate buffered saline (PBS), human serum, or implanted subcutaneously in rats, free or in stainless steel cages. The exudate collection allowed the evaluation of inflammatory cell populations, up to 21 days. The ferrous/ferric redox electrode reactions were used to assess the electrode elements performance for up to 49 days. Following testing, scanning electron microscopy (SEM) evaluated cell surface adhesion, while fibrous capsules were examined by histology. It was determined that the exudates leukocyte concentration due to the presence of sensors was comparable to the empty cage controls. For the length of the study, the sensors functionality appeared not to be influenced by the in vivo environment, when tested ex vivo, without the surrounding fibrous capsule. Surface imaging (SEM) indicated temporal focal dissolution of the Ag/AgCl electrodes with no apparent local toxicity. We concluded that the ESDs were biocompatible and their ex vivo functionality was not lost when maintained in vivo for up to 49 days.     

Nutrition services in Canadian neonatal follow-up programs.

The benefits of nutrition assessment and support of the high-risk infant are well established. The premature infant remains vulnerable for poor growth and developmental disabilities, thus requiring consistent monitoring, intervention, and follow-up care. The purpose of this study was to determine the registered dietitian's role in neonatal/perinatal follow-up programs. A survey was sent to the 26 follow-up programs in Canada. The questionnaire response rate was 81%. Registered dietitians were involved in 67% of these programs. Of these dietitians, 43% were assigned to neonatal/perinatal follow-up programs while 57% were involved only by consult. The average time that assigned registered dietitians devoted to programs was 0.35 full-time equivalents. Over 80% of the dietitians did ongoing development, evaluation, and modification of nutrition care plans; 71% screened new patients for nutritional risk, and 100% instructed patient families and developed teaching materials. The study findings will assist program planners who wish to establish a dietitian position in a neonatal/ perinatal follow-up program. For registered dietitians already working in such programs, the results may provide some guidance on role definition and expansion.     

Interference of hydrogen peroxide on the standard cod test

The standard method for measuring chemical oxygen demand (COD), which is widely used throughout environmental engineering is affected by a number of inorganic substances. These are outlined in Standard Methods (APHA, Standard Methods for the Examination of Water and Wastewater, 16th edition, Washington, D.C., 1985) and methods of overcoming the problems are given, however, no reference is made to hydrogen peroxide as an interfering substance. In a number of complex industrial wastewaters, H₂O₂ is present and is also used in its treatment which will thus interfere with the analysis. This interference has a positive error effected on COD. This work has been carried out in order to show how hydrogen peroxide interferes in COD analysis, and further shows how to allow for this interference in future COD analysis. A number of specific points have been raised. It has been shown that H₂O₂ forms a complex with potassium dichromate, the structure of which is given. In experiments which were made on a range of synthetic samples, it was noted that the samples containing H₂O₂ had different COD values for various concentrations although they contained no organic substances. Also, it was shown on industrial wastewater samples that H₂O₂ either increased the COD values of the wastewater samples or interfered with the procedure, by completely masking the titration end-point. Reference is made to those industries and processes which contribute to interference by H₂O₂. A method of calculating the effect of interference by H₂O₂ is recommended.