Biomedical subjects

C Tomlin

Publications and source records attributed to C Tomlin.

4 recordsLinked to original sources

PubMed2004

Symbolic reachable set computation of piecewise affine hybrid automata and its application to biological modelling: Delta-Notch protein signalling.

Hybrid automata are an eminently suitable modelling framework for biological protein regulatory networks, as the protein concentration dynamics inside each biological cell are modelled using linear differential equations; inputs activate or deactivate these continuous dynamics through discrete switches, which themselves are controlled by protein concentrations reaching given thresholds. This paper proposes an iterative refinement algorithm for computing discrete abstractions of a class of hybrid automata with piecewise affine continuous dynamics and forced discrete transitions, defined completely in terms of symbolic variables and parameters. Furthermore, these discrete abstractions are utilised to compute symbolic parametric backward reachable sets from the equilibria of the hybrid automata, that are guaranteed to be exact or conservative under-approximations. The algorithm is then implemented using MATLAB and QEPCAD, to compute reachable sets for the biologically observed equilibria of the multiple cell Delta-Notch protein signalling automaton with symbolic parameters. The results are analysed to show that novel, non-intuitive, and biologically interesting properties can be deduced from the reachability computation, thus demonstrating the utility of the algorithm.

Algorithms↗

PubMed2000

Variation of method for measurement of brachial artery pressure significantly affects ankle-brachial pressure index values.

BACKGROUND: Mmeasurement of ankle brachial pressure indices (ABPI) is important in the assessment of patients with peripheral vascular disease. METHODS: Thirty-one hospitals with a vascular surgeon were selected at random. A telephone questionnaire was completed to assess the method used for the measurement of ABPI. Following the survey, 14 patients with peripheral vascular disease had their ABPI measurement done by two observers, a pre-registration house officer and a clinical nurse practitioner. Observers were blinded to their own and each other's results. Brachial systolic pressures were obtained using a DINAMAP(TM)(Critikon, Tampa, U.S.A.) automated blood pressure monitor, the Korotkoff method (12 cm cuff, parallel wrap) and an 8 MHz Doppler probe (Huntleigh) and sphygmomanometer. Ankle systolic pressures were obtained using the Doppler probe. The results were analysed using the Wilcoxon signed rank test. RESULTS: The survey demonstrated that at the majority of centres with vascular laboratories the brachial artery systolic pressures were measured using a Doppler probe. In contrast, at centres where the house officers performed the routine measurements, over 60% used the Korotkoff method to obtain this reading. One in four nurse practitioners used the Korotkoff method. When the ABPI values were calculated, the DINAMAP produced significantly higher median values than the Korotkoff (0.79 vs 0.72, p=0.003) and Doppler methods (0.79 vs 0.70, p<0.0001). The nurse had a higher median ABPI value of 0.76 compared with the doctor (0.71, p=0.01). CONCLUSION: This study shows that measurement of ABPI varies in different vascular units. The technique for ABPI measurement should be standardised.

Aged↗

PubMed1988

A further examination of heavy metal inhibition of gas production by thermophilic anaerobic sludges.

Mesophilic anaerobic digestion is a well established method for stabilising municipal sewage sludges. However, digestion in the thermophilic range is very restricted. The main reason for this has been the imbalance between the energy produced in the form of biogas and the energy required to maintain the temperature of a thermophilic system. It has been shown recently that an energy-positive process can be achieved using thickened sludges as the feedstock and, therefore, thermophilic digestion must be considered as a potentially attractive process for sludge stabilisation. However, before it can properly be offered as an alternative technology, the effect of toxic materials must be known. Currently, there is little information about the effect that known toxic agents can have on the microbial flora of a thermophilic sludge. This paper examines the toxicity (measured in terms of gas inhibition) of heavy metals, both individually and in combinations, on the sludge produced by a laboratory-scale digester (10 litres) operating at 55 degrees C with a solids retention time of 20 days. The metals used were zinc, lead, nickel, copper and cadmium and the gas inhibition studies were done in small (500 ml) flasks so that the gas production could be monitored precisely. Statistical analysis of the results showed that a model, developed previously to describe the toxicity of a range of compounds to mesophilic systems, was applicable to heavy metals and thermophilic sludges.

Anaerobiosis↗

PubMed1981

Self-recognition in retarded children.

This study was designed to investigate the relationship between cognitive and affective development. Young preverbal retarded children watched TV images of themselves with faces marked or unmarked and of a peer whose face was marked. We used the objective technique of increased mark-directed responses as evidence of self-recognition and rated the children's reactions as they watched these images. The emergence of self-recognition was closely tied to the maturity of the children's general responsiveness to their reflections. The Down's syndrome children made a broad range of responses, including the curiosity and self-conscious behaviors characteristic of normal children during the second year of life, and all except one of these children showed evidence that they recognized their images. In contrast, the range of behaviors displayed by multihandicapped children was greatly restricted and similar to children in the first year of life. Less than half of these children showed an emergence of self-recognition.

Body Image↗