An Integrated Approach to High Integrity Software Verification

Using automated reasoning techniques, we tackle the niche activity of proving that a program is free from run-time exceptions. Such a property is particularly valuable in high integrity software, for example, safety- or security-critical applications. The context for our work is the SPARK Approach for the development of high integrity software. The SPARK Approach provides a significant degree of automation in proving exception freedom. Where this automation fails, however, the programmer is burdened with the task of interactively constructing a proof and possibly also having to supply auxiliary program annotations. We minimize this burden by increasing the automation, through an integration of proof planning and a program analysis oracle. We advocate a ‘cooperative’ integration, where proof-failure analysis directly constrains the search for auxiliary program annotations. The approach has been successfully tested on industrial data.     

Some Thermal Properties of a Copper–Tin Alloy

The thermal properties (heat capacity, thermal diffusivity, and electrical resistivity) of a Cu + 10 wt% Sn alloy in both solid and liquid phases have been reported. Using these values it was confirmed that the Lorenz relation is suitable for obtaining thermal conductivity from electrical resistivity in the liquid phase of this alloy. Also, the temperature differential (d/dT) obtained from such an approach was in excellent agreement with the thermal conductivity values calculated from thermal diffusivity.     

Shielded gradients. And the general solution to the near field problem of electromagnet design

The development of actively shielded gradients introduced the concept of surface distributed conductors for the production of electromagnetic fields. This represented the most significant step in electromagnetic coil design since the discovery of the electromagnetic field equations a century earlier. Further, the associated recognition of the Biot-Savart equation as the convolution of the current distribution function with the inverse square spatial dispersion, permits a solution of the general near field problem with implications for other scientific fields that have yet to be explored.     

Monaural and binaural story recall by schizophrenic subjects.

P. Green and other investigators have reported that schizophrenic Ss have poorer recall of stories presented to both ears than to the single best ear (binaural deficit) and poorer recall of stories presented to the left ear than to the right ear (monaural asymmetry) than do normal control Ss. These studies are plagued by potential methodological problems, including differences in overall accuracy, which artifactually affect the difference scores, and scoring methods that are vulnerable to systematic bias. In this study, scores of schizophrenic, bipolar, and normal control Ss on the Auditory Comprehension Test were compared. Scoring bias was avoided by the use of blind scoring and a revised scoring manual, and artifactual effects of accuracy were considered in interpreting the results. Contrary to previous findings, the groups did not differ on either monaural asymmetry or binaural deficit. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Long-term potentiation in vivo in layers II/III of rat barrel cortex

Long-term potentiation was studied in vivo in the rat barrel cortex. It was found that LTP lasting several hours could be induced in layer II/III by tetanic stimuli applied in layer IV. The probability of inducing LTP at a given site was high (86%) provided that the electrodes were not displaced too far horizontally. LTP was not observed if the stimulating electrode was located on the far side of the neighbouring barrel-column from the recording electrode. The strongest LTP was induced by stimulating layer IV septal locations or the edge of the barrel and recording in the near half of the neighbouring barrel. However, examples were found of LTP from layer IV to II/III within the same barrel, within the same septum and from barrel to adjacent septum. The probability of inducing LTP on a particular occasion was greatly increased by iontophoresis of bicuculline at the recording site during the tetanus (from 20 to 55% judged by a change in peak amplitude). The average increase in the peak amplitude was 29 +/- 3.2% for protocol 1 (urethane anesthesia, monopolar stimulation) and 23 +/- 7% for protocol 2 (barbiturate anesthesia, bipolar stimulation). The probability of inducing LTP was greater if the first tetanus was accompanied by BMI application (67%) than for any subsequent attempts (39%). These results suggest it should be possible to study the effect of LTP on sensory processing in defined positions within the barrel field.     

The integration of the corneal and limbal fibrils in the human eye

The precise orientation of the collagen fibrils in human cornea and sclera and the method by which these two areas fuse together at the limbus have never been determined, despite the importance of this information. From a consideration of the mechanics of the system, fibril orientation in the tissue has the potential to affect the curvature of the cornea so, by inference, refractive problems such as astigmatism involving an incorrect curvature of the cornea may be related to fibril orientation. The high intensity and small beam size of a synchrotron x-ray source has enabled us to study fibril orientation in post-mortem human cornea and sclera. Previously we have revealed two preferred directions of orientation in the cornea (Meek, K. M., T. Blamires, G. F. Elliot, T. Y. Gyi, and C. J. Nave. 1987. Curr. Eye Res. 6:841-846) and a circumcorneal annulus in the limbus (Newton, R. H., and K. M. Meek. 1998. Invest. Ophthalmol. & Visual Sci. 39: 1125-1134). Here we present the results of our investigation into the relationship between these two features. Our measurements indicate that the corneal fibrils oriented in the two preferred directions bend at the limbus to run circumferentially. On the basis of these results we propose a model as to how the human cornea and sclera fuse together.     

Characterisation of erythrocyte shapes and sizes by NMR diffusion-diffraction of water: correlations with electron micrographs

Irradiation of the mammalian foetus produces a broad spectrum of congenital abnormalities, growth retardations, developmental delays, and functional deficits, depending upon the dose and the specific gestational phase of irradiation. The developing brain is particularly susceptible to production of deleterious effects, with decreased brain size, behavioural alterations, and mental retardation having been documented. Supplementing the limited human data, rodent models have been extensively used to investigate the specific processes by which relatively low doses, with correspondingly minor cellular damage to the developing neocortex, can produce dramatic postnatal consequences in brain structure and function. The effects of a variety of physical (dose, linear energy transfer, dose rate, fractionation) and biological (species, strain, gestational age, time course post-irradiation) parameters have been examined in an attempt to provide much needed information on such critical aspects as dose response, threshold doses for effect, and extrapolation to human risk estimates. Various acute cellular responses (e.g. appearance of pyknotic cells and macrophages) observed in the developing neocortex 0-24 h after in utero irradiation can be associated with postnatal effects. Moreover, it is possible to correlate thinning of specific layers of the cerebral cortex with specific behavioural aberrations, allowing prediction of brain structural changes from functional alterations, and vice versa. Thus, it is possible to speculate as to the mechanisms and targets for extremely sensitive, radiation-induced cellular damage in the developing foetal brain, that will interfere with the orderly and precisely programmed development of the mammalian brain, leading finally to postnatal expression as delays in growth and development, perturbations in behaviour, and alterations in brain structure.     

Motor function of the proximal stomach and visceral perception in gastro-oesophageal reflux disease

Oxytocin (OT) is present in the mammalian testis and has been shown to play a role in the modulation of seminiferous tubule contractility and steroidogenesis. However, stage-specific effects of the peptide have not been previously investigated. In this study, computer-assisted analysis and time-lapse videomicrography were used to investigate basal contractility and the response to OT of seminiferous tubules at specific stages of the spermatogenic cycle. Adult rat testes were placed in fresh oxygenated DMEM F12 medium, decapsulated, and the tubules gently teased apart. Stages were identified by transillumination and a 10 mm section of tubule at each of stages IV-V, VII-VIII and XIII-I was placed in a microslide chamber and perifused with medium. After a control period of 3 h, OT (2 nM) was given for 1 h, followed by another control period of 1 h. The experiment was repeated using tubules from different rats and data were analysed to give arbitrary units of tubule contractility. Contractility was observed in all the tubules studied and the contractile activity was shown to vary depending on the stage of the spermatogenic cycle. Mean basal contractility at stages VII-VIII, the time when sperm are shed from the epithelium, was significantly lower than that at stages IV-V and XIII-I. The response of the tubules to OT was also stage-dependent, with the peptide producing the largest increases in contractile activity at stages VII-VIII and having no effect at stages IV-V. We postulate that these stage-specific differences in basal and OT-stimulated contractility may be important in co-ordinating the movement of developing germ cells towards the lumen of the seminiferous epithelium and in the process of spermiation.