Biomedical subjects

S Alani

Publications and source records attributed to S Alani.

4 recordsLinked to original sources

PubMed1995

Topographic mapping of cortical potentials evoked by distension of the human proximal and distal oesophagus.

We describe cortical potentials evoked by balloon distension of the proximal and distal oesophagus in 8 healthy right handed volunteers. Oesophageal stimulation was performed using a pump which rapidly inflated a 2 cm silicone balloon positioned either 3 cm distal to the upper oesophageal sphincter or 5 cm proximal to the lower oesophageal sphincter, at a frequency of 0.2 Hz, using inflation volumes which produced a definite but not painful sensation. Oesophageal evoked cortical potentials were recorded in all subjects with an initial negative and positive component (N1 and P1), followed by a second negative and positive component (N2 and P2) in 6 subjects. The morphology and the scalp topography of the N1 component elicited by proximal and distal oesophageal stimulation suggests activation of the primary somatosensory cortex and/or the insular. There was also evidence for hemispheric dominance for the N1 potential which was independent of handedness. The frontal emphasis of the proximal oesophageal N1 component, in contrast to the central emphasis of the distal oesophageal N1 component, suggests that different neuronal populations were activated by stimulation of the two sites. The frontal emphasis of the ensuing P1 component from both oesophageal sites suggests that it originates in a separate precentral source. The topography of the N2 components obtained by stimulation of either oesophageal site was similar to that of the N1 component, suggesting that they originate in similar areas of the cortex. The P2 component evoked by stimulation of both oesophageal sites was localised at the vertex. The inter- and intra-subject variation in the morphology of the N2 and P2 components suggests that secondary cortical processes related to cognition may be involved in their generation.

Adult↗

PubMed1994

Esophageal myoelectric responses to magnetic stimulation of the human cortex and the extracranial vagus nerve.

We describe the use of magnetic stimulation of the human motor cortex and the extracranial vagus nerve in the neck to study human esophageal electromyographic (EMG) responses. Diffuse cortical stimulation produced both an early and a late EMG response in the proximal esophagus with latencies of 10.9 +/- 0.5 and 43.4 +/- 4.3 ms, respectively. Increasing the stimulation intensity increased the amplitude and duration, but reduced the latency, of the early response (P < 0.01), whereas the late response remained unchanged. The early response, but not the late response, was facilitated when cortical stimulation was performed during valsalva maneuver. Maximal early response amplitudes were obtained by focal stimulation of either hemisphere 4-8 cm lateral to the vertex. Stimulation of the neck over the extracranial vagus nerve at the angle of the jaw also produced an early and a late EMG response in the proximal esophagus with latencies of 4.3 +/- 0.4 and 56.8 +/- 14.5 ms, respectively. Early responses were also recorded in the midesophagus and distal esophagus from either cortical or vagal stimulation, but amplitudes were smaller and rise times were longer, suggesting passive "volume conduction" from the proximal esophagus. Comparison of laryngeal, pharyngeal, and esophageal early EMG responses showed similar amplitudes and rise times, suggesting that the action potentials were generated locally at each site and that true esophageal responses were being detected.

Adult↗

PubMed1994

Enhanced filtration using flat membranes and standing vortex waves.

The performance of membrane filters is limited by concentration polarisation and membrane fouling. High shear rates reduce these effects but can damage delicate cells and proteins in biological fluids. Secondary flows to promote fluid mixing, and hence enhance filtration, can be highly effective, but usually carry the penalty of complexity. Oscillatory flow over furrowed or dimpled membrane surfaces (vortex mixing) has been shown to be very efficient in the microfiltration and oxygenation of blood, but carries the added complexity of oscillatory flow and the need to thermoform the membranes. To allow the use of asymmetric or rigid membranes, a new form of vortex mixing has been studied, in which the membranes are flat and form parallel channels. Feed flow is oscillatory and passes back-and-forth across ladder-like flow deflectors to generate standing vortex waves. Flow visualisation studies and numerical calculations of standing vortex waves (SVW) were undertaken to help optimise flow parameters and flow deflector geometry. Flat plate membrane ultrafilters were built and evaluated for different geometries of flow deflector, using solutions of bovine serum albumin (BSA) as the test fluid. Very high filtration rates were measured with BSA concentrations ranging from 1 to 24%. A SVW ultrafilter was compared with a Millipore Pellicon ultrafilter using BSA as the test fluid. Filtration flux was similar at low concentrations of BSA, but was greater by a factor of 4.5 in the SVW device at high concentrations of BSA.

Chemical Engineering↗

PubMed1982

Neurosyphilis in the Leicester area.

Twenty patients with neurosyphilis are reviewed. They were gathered over a 15-year period during which the overall incidence was 0.18 per 100,000, though fewer cases appeared in the latter half of the study. The commonest presentation was with mental symptoms and classical forms of neurosyphilis were rarely seen. No patient presented with epilepsy. There is a case for the more selective use of serological testing.

England↗