Biomedical subjects

N D Harris

Publications and source records attributed to N D Harris.

40 records · Page 3Linked to original sources

PubMed1968

Effect of metallic cations on the viability of phenol-treated Escherchia coli.

Five metallic cations (Fe(3+), Cr(3+), Ca(2+), Mg(2+), Mn(2+); concentration range, 1.85 x 10(-4) to 37 x 10(-4)m) were incorporated individually as chlorides into nutrient broth and agar media used for the recovery of phenol-treated Escherichia coli. The effects observed varied with the concentration and the ionic species. In nutrient agar, Fe(3+) and Cr(3+) were generally beneficial but were toxic at 37 x 10(-4)m. Of the divalent ions tested, Ca(2+) and Mg(2+) usually gave higher counts in nutrient broth, except at a concentration of 9.25 x 10(-4)m, whereas the effect of Mn(2+) was rather variable. Two possible explanations are suggested to explain these effects. Toxic materials may be removed from the media by the precipitates formed on the addition of Fe(3+) or Cr(3+), or, in the case of the divalent ions, the integrity of the bacterial cell membranes may be maintained.

Calcium↗

PubMedDate not supplied

Current developments in oxygen concentrator technology.

Oxygen concentrators are electrically powered devices which are designed to provide oxygen for patients who require long-term domiciliary oxygen. The machines have been available for the last 10 to 15 years, but it is only recently that improvements in design have led to them being generally accepted as a reliable and economical means of supplying long-term oxygen therapy. There are two basic types of concentrator currently available: the molecular sieve (MS) concentrator, and the membrane oxygen enricher. In this article the characteristics and principles of operation of these machines are reviewed, together with the development and present state of MS concentrator technology. A summary of a comparative evaluation of seven MS concentrators is presented and the results discussed. Relevant safety standards and current trends in concentrator design are then reviewed.

Biomedical Engineering↗

PubMedDate not supplied

Clinical applications of electrical impedance tomography.

This article is a preliminary review of the possible clinical applications of electrical impedance tomography (EIT). The applications to, for example, the central nervous, respiratory, cardiovascular and digestive systems are covered. It is concluded that the area of greatest potential application of EIT is monitoring cardiopulmonary function, but that studies on much larger groups of patients than have been carried out hitherto are required to fully assess the potential of EIT as a clinical tool.

Body Composition↗

PubMedDate not supplied

A portable system for monitoring physiological responses to hypoglycaemia.

Hypoglycaemia is the most common complication affecting people with Type 1 insulin dependent diabetes mellitus. Its onset is characterized by symptoms which include sweating, tremor, palpitations, loss of concentration and tiredness. As part of a research project to investigate the mechanisms of hypoglycaemia we have developed an ambulatory system to monitor and record pulsatile changes in blood flow, pulse interval, body temperature and skin impedance. The system uses a pocket computer (Atari Portfolio) to collect and store the data on a memory card. The analogue system consists of two thermocouples, an infrared photoplethysmograph and skin impedance monitoring circuit. To conserve power the system is programmed to make measurements for 2 min every 10 min: using this regimen over 16 h of data can be stored. Data collected during a spontaneous overnight hypoglycaemic episode are presented and also a comparison between continuous and intermittent data collection during a period of induced hypoglycaemia. The system is being used to investigate the physiological responses to hypoglycaemia but could easily be adapted for monitoring other physiological signals.

Arrhythmias, Cardiac↗