Response times to stimuli of increasing complexity as a function of ageing

Twelve elderly and 12 young subjects were tested on a series of experiments with increasing complexity of perceptual-response mapping. As task complexity increased the differential slowing in performance between young and old increased and an ageXtask complexity interaction was observed. However, with practice this phenomenon disappeared leaving an apparent age lag constant. This slowing was due to increased central processing time rather than peripheral factors. No major differences in strategies were observed between the groups, though the old subjects tended to be less able to extract critical (useful) features from the display. Stimulus repetitions of a new kind were found where all characteristics of the stimulus (relevant and irrelevant) were important. Repetitions of coding rules rather than of particular signals or responses also facilitated RT. It was also found that later in practice old subjects were making fewer errors than the young, reversing earlier observations.     

A post mortem study of equine digital flexor tendons

The results of a survey are presented in which 589 limbs from 206 horses were dissected. In174 of the limbs lesions were found in either the superficial (131) or deep (43) digital flexor tendons. Changes occurring with age were also recorded. The sites of the abnormalities and their macroscopical appearance are described and the value of the results is considered in relation to the diagnosis and the treatment of clinical lesions.     

Acute cholecystitis in choledocholithiasis and stricture of the ampulla of Vater

The central haemodynamics and regional lung function were measured in the sitting position before and after infusion of prostaglandin F2alpha (PGF2alpha) in seven healthy women in the first trimester of pregnancy. The dosage level of PGF2alpha was: 100mug/min for 10 minutes followed by 300mug/min for 5 minutes. The pulmonary arterial pressure, wedge pressure, and cardiac output were measured by means of a flow direct Swan-Ganz catheter introduced through an antecubital vein. The regional perfusion of the lungs was determined, in the sitting position, by external counting over the chest following intravenous injection of Xe133. The thoracic impedance was measured with the Minnesota Impedance Cardiograph Model 304A and the impedance was considered as an expression of the thoracic fluid volume. A significant redistribution of the pulmonary blood flow after PGF2alpha administration was found, ie an increase in the apical blood flow and a reduction in the basal blood flow. Further, the point of maximal blood flow moved in direction of the apex. A significant increase in both arterial [1.92-2.76 kPa (14.4-20.7 mmHg)] and wedge pressures [0.56-0.83 kPa (4.2-6.2 mmHg)] was found at the highest dosage level, whereas no changes were seen in the cardiac output and thoracic impedance. The findings indicate vasoconstriction of the arterial and possibly on the venous side of the pulmonary vascular bed during PGF2alpha infusion.     

Command neurons in the unconditioned reflex arc of the grape snail

Independent intracellular activation of any one of the five identified neurones elicits a behavioral act of pneumostome closing. Similar closing is evoked by adequate stimulation of different modalities. Comparison of unconditioned reflex properties and characteristics of responses of the studied cells leads to the conclusion that neurones under discussion are command elements for the unconditioned reflex. Command neurones respond to all sensory stimuli which can evoke reflex closing. There is a lot of synchronous EPSPs in their spontaneous activity, but no action potentials. A spike discharge of command neurones evoked by an adequate stimulus always precedes the effector movements but there is no action potentials during the pneumostome closing. Conclusion is made that the functional role of command neurones in the unconditioned reflex arc consists in evaluating the sensory input and in triggering motor programmes.     

Semeiology of bronchogenic carcinoma. Limitations of explorative thoracotomy

Modern methods of semeiological detection of bronchiogenic cancer are discussed in the light of experience gained in a hospital chest surgery centre. Emphasis is laid on the advantages offered by new advances in nuclear diagnosis and bronchial endoscopy. The limitations of exploratory thoractomy are explained. Attention is drawn to the by no means inconsiderable number of cases in which early knowledge of the nature of the process could not be obtained. A series of illustrative cases are presented.     

High-Temperature Fracture Mechanism of Low-Ca-Doped Silicon Nitride

High-purity Si₃N₄ (with 2.5 wt% glassy SiO₂) doped with 0 to 450 at.ppm of Ca was prepared as a model system to investigate the effects of grain-boundary segregants on fracture phenomenology at 1400°C. Subcritical crack-growth (SCG) resistance as well as creep resistance was degraded significantly by the presence of a small amount of Ca. The internal friction of the doped materials exhibited the superposition of a grain-boundary relaxation peak and a high-temperature background, and the apparent viscosity of the grain-boundary film was determined from the peak. Based on these experimental data, the fracture mechanism at 1400°C was divided into three regions: "brittle," SCG, and creep failure as a function of both external strain rate and Ca concentration, C _Ca. From the investigation of the C _Ca dependence of the critical strain rate for the transition from "brittle" to SCG fractures, the SCG phenomenon is suggested to be triggered by small-scale, grain-boundary sliding. The C _Ca dependence of "steady-state" creep rate was far from the theoretical dependence of diffusional creep via a solution-precipitation mechanism. The discrepancy was interpreted to be due to the presence of an impurity-insensitive creep component. This component may correspond to the lowest limit of the tensile creep rate in Si₃N₄ polycrystalline materials containing intergranular glassy-SiO₂ film.     

Synthesis of High Coercivity Core–Shell Nanorods Based on Nickel and Cobalt and Their Magnetic Properties

Hybrid magnetic nanostructures with high coercivity have immense application potential in various fields. Nickel (Ni) electrodeposited inside Cobalt (Co) nanotubes (a new system named Ni @ Co nanorods) were fabricated using a two-step potentiostatic electrodeposition method. Ni @ Co nanorods were crystalline, and they have an average diameter of 150 nm and length of ~15 μm. The X-ray diffraction studies revealed the existence of two separate phases corresponding to Ni and Co. Ni @ Co nanorods exhibited a very high longitudinal coercivity. The general mobility-assisted growth mechanism proposed for the growth of one-dimensional nanostructures inside nano porous alumina during potentiostatic electrodeposition is found to be valid in this case too.     

Mapping sky and surface luminance distribution using a flux mapper

A prototype, all-sky flux mapper has been developed at the Solar Energy Research Institute (SERI). The flux mapper is a video system which provides a rapid, real time processing of daylightning luminance data. The system uses an orthographic-projection fish-eye lens to project the entire image of a 180° field onto a vidicon target. The signal is then digitized and may be plotted as equal brightness comtours or recorded on tape for later analysis. The system has great potential for use in delineating illuminance distribution of the sky and of interior spaces.