Dynamic elasticity by the theory of characteristics

Method of characteristics for analysis of elastic wave equations in Cartesian coordinate

Quantitative Analysis of Electrotonic Structure and Membrane Properties of NMDA-Activated Lamprey Spinal Neurons

Parameter optimization methods were used to quantitatively analyze frequency-domain-voltage-clamp data of NMDA-activated lamprey spinal neurons simultaneously over a wide range of membrane potentials. A neuronal cable model was used to explicitly take into account receptors located on the dendritic trees. The driving point membrane admittance was measured from the cell soma in response to a Fourier synthesized point voltage clamp stimulus. The data were fitted to an equivalent cable model consisting of a single lumped soma compartment coupled resistively to a series of equal dendritic compartments. The model contains voltage-dependent NMDA sensitive (INMDA), slow potassium (IK), and leakage (IL) currents. Both the passive cable properties and the voltage dependence of ion channel kinetics were estimated, including the electrotonic structure of the cell, the steady-state gating characteristics, and the time constants for particular voltage- and time-dependent ionic conductances. An alternate kinetic formulation was developed that consisted of steady-state values for the gating parameters and their time constants at half-activation values as well as slopes of these parameters at half-activation. This procedure allowed independent restrictions on the magnitude and slope of both the steady-state gating variable and its associated time constant. Quantitative estimates of the voltage-dependent membrane ion conductances and their kinetic parameters were used to solve the nonlinear equations describing dynamic responses. The model accurately predicts current clamp responses and is consistent with experimentally measured TTX-resistant NMDA-induced patterned activity. In summary, an analysis method is developed that provides a pragmatic approach to quantitatively describe a nonlinear neuronal system

Some clinical observations on trypanosomiasis rhodesiensis

1. The object of the paper is to record some clinical observations made during the study of 94 consecutive cases of Rhodesian Sleeping Sickness.2. The main factor in the epidemic spread was man-fly-man transmission. The occurrence of human cases with no history of contact and the high T.bracei infection rate among the local fauna are recorded, as the possibility of there being some reservoir cannot be excluded.3. The incubation period is probably between 1-3 weeks.4. The average duration of the illness is five months.5. There was an acute febrile onset in 24/£ of cases. Variations in the subsequent course are found and it is considered that these are due to the existence of strains of trypanosoines of different virulence.6. The central nervous system may be involved at a very early stage. This results in grave pathological changes, but the virulence of the infection is such that symptoms arising from its effect on the heart and other viscera predominate over those due to central nervous system involvement until the last few weeks of the illness. Cardiac symptoms are important and the essential lesion is a toxic myocarditis.7. The axillary group of glands are those most constantly enlarged.8. It is in cases which have relapsed after treatment that mental symptoms are most pronounced. In relapse a new strain of trynanosames has been created, of lowered virulence but resistant to the action of drugs.9. 'Bayer 205' has a strong and immediate effect oh infections of the peripheral blood but its action is not always permanent and it cannot penetrate into the deeper tissues. Tryparsamide is slower in action but it maintains a sterilization made by 'Bayer' and it can exert a beneficial action on the central nervous system.10. Treatment by * Bayer* should he followed immediately by Tryparasmide • A routine treatment by this method gives satisfactory results if treatment is started early in the course of the illness, hut even the most intensive and prolonged doses of the two drugs in combination cannot he relied upon to effect a cure if the disease is well established

Hypersonic test facility Patent

Hypersonic test facility for studying ablation in models under high pressure and high temperatur

Preparation of Isolated Blood Capillaries

Blood capillaries have been isolated from various tissue sources yielding suspensions of capillary segments. These have provided opportunities to study the cellular properties of capillary endothelium under conditions uncomplicated by the presence of stromal tissues and in which measured parameters can be attributed to endothelial cells. Fresh capillary isolates have been used directly as experimental systems but the yield of endothelium is quite low. Amplification of endothelial biomass has been accomplished by using freshly isolated capillaries as explants for primary tissue culture. It has not been previously possible, however, to obtain large amounts of capillary endothelium from a single preparation nor have different capillary types been isolated from the same tissue. The rete mirabile of the eel swim bladder is a copious source of capillaries of two types: thick-walled, continuous capillaries heavily invested with pericytes and thin-walled, fenestrated capillaries. These can be isolated in large numbers free of large blood vessels and contaminating stromal tissue. The two types of capillaries can be isolated from each other by perfusing magnetic beads into one type prior to isolation and separating them from the other type in a magnetic field. This provides a system in which the cellular properties of the two types of endothelium can be studied in vitro and, due to a common isolation procedure, direct comparisons can be made

Depression, School Performance, and the Veridicality of Perceived Grades and Causal Attributions

An external criterion was assessed to test whether depressives have distorted perceptions of covariation information and whether their attributions are consistent with this information. Students’ actual and self-perceived grades, depression status, and attributions for failures were assessed. Furthermore, partici pants estimated average grades. Generally, self-perceived own past grades were inflated. Depressed students and those with low grades distorted their own grades (but not the average grade) more to their favor than individuals low in depression and those with high grades. Depression went along with lower actual grades and with internal, stable, and global failure attributions. Mood differences in attributions were not due to differences in previous grades. Depressed individuals drew (unrealistically) more depressogenic causal inferences when they perceived average grades to be low than when average grades were perceived to be high. However, they (realistically) attributed failure more in a depressogenic fashion than did nondepressives when their own grade history was low

Kinetic pathways of multi-phase surfactant systems

The relaxation following a temperature quench of two-phase (lamellar and sponge phase) and three-phase (lamellar, sponge and micellar phase) samples, has been studied in an SDS/octanol/brine system. In the three-phase case we have observed samples that are initially mainly sponge phase with lamellar and micellar phase on the top and bottom respectively. Upon decreasing temperature most of the volume of the sponge phase is replaced by lamellar phase. During the equilibriation we have observed three regimes of behaviour within the sponge phase: (i) disruption in the sponge texture, then (ii) after the sponge phase homogenises there is a lamellar nucleation regime and finally (iii) a bizarre plume connects the lamellar phase with the micellar phase. The relaxation of the two-phase sample proceeds instead in two stages. First lamellar drops nucleate in the sponge phase forming a onion `gel' structure. Over time the lamellar structure compacts while equilibriating into a two phase lamellar/sponge phase sample. We offer possible explanatioins for some of these observations in the context of a general theory for phase kinetics in systems with one fast and one slow variable.Comment: 1 textfile, 20 figures (jpg), to appear in PR

Phonological working memory impacts on information searching: An investigation of dyslexia

A key aspect of searching is the ability of users to absorb information from documents read in order to resolve their ask. One group of users who have problems with reading are dyslexic users, who due to underlying cognitive impairments in phonological processing and working memory, tend to read more slowly and make reading errors. The purpose of this study is to examine the impact of the dyslexia cognitive profile on information searching. Searches were logged for 8 dyslexic and 8 non-dyslexic university students, in order to examine the differences in searching behavior between the two groups. A set of literacy and phonological working memory tasks were also completed, in order to investigate the relationship between these cognitive variables and searching behavior. Results show that there is a significant difference between the two groups on the number of documents being judged irrelevant, and that this cannot be explained by a topic effect. Instead, the number of documents judged irrelevant is significantly correlated with a measure of working memory. This key result provides the research community the first real insight into impact of impaired short term memory on information searching