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Biomedical subjects

J Hodgkinson

Publications and source records attributed to J Hodgkinson.

10 recordsLinked to original sources
PubMed2005

Modelling and interpretation of gas detection using remote laser pointers.

We have developed a quantitative model of the performance of laser pointer style gas leak detectors, which are based on remote detection of backscattered radiation. The model incorporates instrumental noise limits, the reflectivity of the target background surface and a mathematical description of gas leak dispersion in constant wind speed and turbulence conditions. We have investigated optimum instrument performance and limits of detection in simulated leak detection situations. We predict that the optimum height for instruments is at eye level or above, giving an operating range of 10 m or more for most background surfaces, in wind speeds of up to 2.5 ms(-1). For ground based leak sources, we find laser pointer measurements are dominated by gas concentrations over a short distance close to the target surface, making their readings intuitive to end users in most cases. This finding is consistent with the results of field trials.

Data Interpretation, Statistical↗
PubMed1999

Continuous neonatal blood gas monitoring using a multiparameter intra-arterial sensor.

AIMS: To compare arterial blood gas (ABG) readings obtained with a multiparameter intra-arterial sensor with those from an ABG analyser. METHODS: An MPIAS with the ability to measure continuously pH, PaCO2, and PaO2 was introduced via an umbilical arterial catheter in 27 neonates requiring intensive care. They underwent 3260 hours of MPIAS monitoring, during which 753 ABG readings were performed. RESULTS: Overall bias (mean difference: MPIAS-ABG) and precision (standard deviation of differences) values were: -0.002 and 0.022, respectively, for pH; +0.26 and 0.52 for PaCO2 (kPa); and -0.19 and 0.99 for PaO2 (kPa). This gave 95% limits of agreement as: -0.047 to +0.042 for pH, -0.76 to +1.28 kPa for PaCO2, and -2.13 to +1.75 kDa for PaO2. For each variable, precision across readings from the same individual was better than overall precision for all data. No complications related to the use of the catheter were observed. CONCLUSIONS: Continuous MPIAS ABG monitoring is an exciting development, with the potential to reduce blood transfusions and improve ABG homeostasis.

Blood Gas Analysis↗
PubMed1998

Structural interactions between actin, tropomyosin, caldesmon and calcium binding protein and the regulation of smooth muscle thin filaments.

The basic structure and functional properties of smooth muscle thin filaments were established about 10 years ago. Since then we and others have been working on the details of how tropomyosin, caldesmon and the Ca(2+)-binding protein regulate actin interaction with myosin. Our work has tended to emphasize the similarities between caldesmon and troponin function whilst others have been more concerned with the differences. The need to resolve the resulting differences has stimulated us to find new and more direct ways of investigating the mechanism of thin filament regulation. In recent years an apparent divergence has opened up between functional measurements, which indicate an allosteric-cooperative regulatory mechanism in which caldesmon and Ca(2+)-binding protein control actin-tropomyosin state in the same way as troponin, and structural measurements which show thin filament structures unlike striated muscle thin filaments. The challenge is to interpret function in terms of structure. We have combined functional studies with expression and mutagenesis of caldesmon and with structural methods including X-ray crystalography of tropomyosin-caldesmon crystals, electron microscopy and helical reconstruction of actin-tropomyosin-caldesmon complexes and high resolution nuclear magnetic resonance spectroscopy of the C-terminus of caldesmon in interaction with actin and calmodulin. We have used this information to propose a structural mechanism for caldesmon regulation of the smooth muscle thin filament.

Actins↗
PubMed1992

How common are polycystic ovaries in normal women and what is their significance for the fertility of the population?

OBJECTIVE: We wished to determine the prevalence of polycystic ovaries (PCO) and relate morphological appearance to fertility. DESIGN: We sent postal invitations to a random sample of women born in the years 1952-1969 from a list of a single Group Practice to attend for reproductive history questionnaire, examination, ultrasound scan of the ovaries and hormone measurements within 5 days of the onset of menstruation. SUBJECTS: Of 1065 women potentially available for study, 571 (54%) replied of whom 353 (62%) agreed to participate. One hundred and ninety (18%) completed the study, 163 were deferred (57 because of current or very recent pregnancy, 106 because of inconvenience at time approached), and 18 additional women volunteered. MEASUREMENTS: Prevalence of polycystic ovaries, ovarian size and morphology, menstrual history, features of androgen excess, fertility status, serum hormone levels. RESULTS: The prevalence of PCO was 22% (41/190). PCO and non-PCO women were similar with respect to age, body mass index, oral contraceptive pill (OCP) usage, acne, and menstrual pattern but hirsutism (Ferriman and Gallwey score > 7) was significantly (P = 0.006) more frequent among PCO women. Proven prior fertility was the same in PCO (56%) and non-PCO (64%) women and an equal proportion in each group had not yet tested their fertility. Of those women with previously proven fertility, self-perceived difficulty in conception occurred in similar proportions of women with and without PCO. Unresolved primary or secondary infertility (2.5-4%) was similar in both groups. Ovarian volume (each ovary separately) was larger in women with PCO irrespective of current OCP usage. Serum levels of oestradiol and FSH were similar in PCO and non-PCO women, but LH was distributed around a higher median in PCO women. Median testosterone and androstenedione levels were the same in PCO and non-PCO women. CONCLUSIONS: The prevalence of polycystic ovarian morphology is high but, in this sample of women, was accompanied by minimal clinical manifestations and apparently no deleterious effects on earlier fertility. An isolated finding of polycystic ovaries may be a normal variation and should not necessarily imply altered fertility potential.

Adult↗
PubMed1988

A comprehensive indexed bibliography data base using a micro computer.

A comprehensive index has been developed for coding and cataloguing alcohol literature. A system has been implemented using a commercial data base management program and a micro computer for computerising the references. In addition to the index code and citation the user can also enter an abstract and a description of the article. References can be added to the computer, edited, searched for, displayed on screen, typed on paper, or sent to a text file using a selection of criteria entered by the user. When a search is performed the printout can include the abstract of each paper similar to that obtained from larger bibliographic services. Such a system is beneficial for personal study, for writing books, articles and theses and for use by departments and small libraries.

Abstracting and Indexing↗