Appraisal of the inverted-mesa AT-cut quartz resonator for achieving low-inductance high-Q single-response crystal units

A novel design for v.h.f. AT-cut quartz-crystal units is described which enables optimum energy-trapping conditions to be achieved with less restriction in the choice of equivalent electrical parameters than is usual for conventional units. The good suppression of unwanted modes, low inductance values and potentially good frequency stability of this type of unit should lead to its application in both oscillators and filters.     

Analytic solution for the birefringence produced by thermal stress in polarization-maintaining optical fibers

Polarization-maintaining optical fibers are usually made by inducing a large anisotropic thermal stress in the core so that it appears highly birefringent. A simple analytic solution has been found for the birefringence in terms of the cross-sectional distribution of the high-expansion material used to create the thermal stress. The analysis is able to predict optimal structures which efficiently utilize the available stress and thus maximize the birefringence. It is shown that the optimum structure has a cross-sectional geometry resembling a bow-tie. Design rules are given whereby the dimensions may be chosen and these are verified in a simple experiment.     

Brain-computer interface design for asynchronous control applications: improvements to the LF-ASD asynchronous brain switch

The low-frequency asynchronous switch design (LF-ASD) was introduced as a direct brain-computer interface (BCI) technology for asynchronous control applications. The LF-ASD operates as an asynchronous brain switch (ABS) which is activated only when a user intends control and maintains an inactive state output when the user is not meaning to control the device (i.e., they may be idle, thinking about a problem, or performing some other action). Results from LF-ASD evaluations have shown promise, although the reported error rates are too high for most practical applications. This paper presents the evaluation of four new LF-ASD designs with data collected from individuals with high-level spinal cord injuries and able-bodied subjects. These new designs incorporated electroencephalographic energy normalization and feature space dimensionality reduction. The error characteristics of the new ABS designs were significantly better than the LF-ASD design with true positive rate increases of approximately 33% for false positive rates in the range of 1%-2%. The results demonstrate that the dimensionality of the LF-ASD feature space can be reduced without performance degradation. The results also confirm previous findings that spinal cord-injured subjects can operate ABS designs to the same ability as able-bodied subjects.     

The preservation of spent brewers' grains by the application of intermediate moisture food technology

Spent brewers' or distillers' grains are normally disposed of either in the wet form, in which they spoil rapidly, or after drying, which is costly. Alternatively, the storage life of wet grains may be extended by ensiling, which involves on-farm control and equipment. This investigation examines the preservation of spent grains by lowering the water activity of the material using molasses and further stabilising the mixture by incorporating an anti-mycotic agent. Investigations at both laboratory-scale and pilot-scale are reported culminating in the successful stabilisation of the wet grains by the incorporation of 30% of beet molasses and 0.3% of potassium sorbate into the grains after preliminary centrifugation. For effective preservation the stabilised grains should be consolidated in plastic bags followed by closing to leave the minimum possible headspace in the bags.     

Intrinsic significance of molecular aggregation in sucrose-surfactant separation by dialysis

Aqueous sucrose-surfactant mixtures were dialysed and the diffusates examined quantitatively for sucrose at intervals by spectrophotometric analysis. The effect of surfactants (lecithin and glycerol monostearate) on the dialysability of sucrose from these solutions was also investigated and the amount of sucrose dialysed was found to increase steadily only up to about 2h with lecithin slowing down the rate of sucrose dialysis much more than GMS. These variations in the dialysability of sucrose from the mixtures are explained in terms of molecular aggregation and these are confirmed by freezing point depression measurements. The results are discussed in terms of the significance of molecular aggregation on the gustatory qualities of sapid molecules.     

Significance of local extradural cooling on cervical spinal cord (experimental study)

The PQ-interval was measured while resting supine before exercise testing, in the erect position on the bicycle before starting exercise, and resting supine after exercise in 68 men 6--8 weeks after acute myocardial infarction. During a 6-year follow-up period the death was non-sudden (greater than 1 hour) in 25 of these patients. In this group the PQ-time was significantly shorter (p less than 0.001) during somatomotor activation on the bicycle before exercise than resting supine. The same directional change (p less than 0.01) was seen in the sudden death (less than 1 hour) group (N = 21), but not in the patients who survived. PQ-time at supine rest before exercise testing, however, was significantly shorter (p less than 0.02) in surviving patients than in the non-sudden death group. The possible mechanisms of these, and of previously reported changes in the R-wave amplitudes and QT-times, are discussed.     

Technical note: repeatability of measurement in determining stature in sitting and standing postures.

The aim of this study was to determine the effect of sitting and standing postures on the repeatability of a stadiometer designed to detect small variations in spinal length. Two groups of ten healthy subjects, with no previous or known history of back problems, participated in this study. One group was measured in the standing posture, while the other group was measured in a sitting posture. All subjects gave informed consent to participate in this study. Subjects had a set of landmarks defining the spinal contour marked on their backs and then stood in the stadiometer for three series of ten measurements to be performed. At the end of each measurement, the subjects were requested to move away from and then be repositioned in the stadiometer. Subjects improved the repeatability across the measurement series. At the end of the second measurement series, all subjects presented mean standard deviations of 0.43 +/- 0.08 mm (range 0.30-0.50 mm) in the standing posture. In the sitting posture, deviations of less than 0.05 mm were obtained only at the end of the third measurement series (0.48 +/- 0.08 mm; range 0.34-0.62 mm), suggesting that this posture required three measurement series before repeatable measurements could be assured rather than two in the standing posture.