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Biomedical subjects

M A Barton

Publications and source records attributed to M A Barton.

At least 19 recordsLinked to original sources
PubMed2006

Compensation of strong thermal lensing in high-optical-power cavities.

In an experiment to simulate the conditions in high optical power advanced gravitational wave detectors, we show for the first time that the time evolution of strong thermal lenses follows the predicted infinite sum of exponentials (approximated by a double exponential), and that such lenses can be compensated using an intracavity compensation plate heated on its cylindrical surface. We show that high finesse approximately 1400 can be achieved in cavities with internal compensation plates, and that mode matching can be maintained. The experiment achieves a wave front distortion similar to that expected for the input test mass substrate in the Advanced Laser Interferometer Gravitational Wave Observatory, and shows that thermal compensation schemes are viable. It is also shown that the measurements allow a direct measurement of substrate optical absorption in the test mass and the compensation plate.

Journal Article↗
PubMed2005

Upper limits on a stochastic background of gravitational waves.

The Laser Interferometer Gravitational-Wave Observatory has performed a third science run with much improved sensitivities of all three interferometers. We present an analysis of approximately 200 hours of data acquired during this run, used to search for a stochastic background of gravitational radiation. We place upper bounds on the energy density stored as gravitational radiation for three different spectral power laws. For the flat spectrum, our limit of omega0 < 8.4 x 10(-4) in the 69-156 Hz band is approximately 10(5) times lower than the previous result in this frequency range.

Journal Article↗
PubMed2005

Limits on gravitational-wave emission from selected pulsars using LIGO data.

We place direct upper limits on the amplitude of gravitational waves from 28 isolated radio pulsars by a coherent multidetector analysis of the data collected during the second science run of the LIGO interferometric detectors. These are the first direct upper limits for 26 of the 28 pulsars. We use coordinated radio observations for the first time to build radio-guided phase templates for the expected gravitational-wave signals. The unprecedented sensitivity of the detectors allows us to set strain upper limits as low as a few times 10(-24). These strain limits translate into limits on the equatorial ellipticities of the pulsars, which are smaller than 10(-5) for the four closest pulsars.

Journal Article↗
PubMed2001

Stable operation of a 300-m laser interferometer with sufficient sensitivity to detect gravitational-wave events within our galaxy.

TAMA300, an interferometric gravitational-wave detector with 300-m baseline length, has been developed and operated with sufficient sensitivity to detect gravitational-wave events within our galaxy and sufficient stability for observations; the interferometer was operated for over 10 hours stably and continuously. With a strain-equivalent noise level of h approximately 5x10(-21)/sqrt[Hz], a signal-to-noise ratio of 30 is expected for gravitational waves generated by a coalescence of 1.4M-1.4M binary neutron stars at 10 kpc distance. We evaluated the stability of the detector sensitivity with a 2-week data-taking run, collecting 160 hours of data to be analyzed in the search for gravitational waves.

Astronomy↗
PubMed1992

Diagnosis and assessment of pectoralis major rupture by dynamometry.

Four patients with pectoralis major ruptures underwent clinical and dynamometric assessment and one patient underwent late surgical repair. The operation is described. Dynamometry proved a useful and objective method of estimating the loss of strength and indicating patients who might benefit from surgical repair.

Adult↗
PubMed1991

Intra-articular distension and steroids in the management of capsulitis of the shoulder.

OBJECTIVE: To determine whether there is any synergistic effect in the administration of intraarticular steroids with distension in the management of early capsulitis of the shoulder. DESIGN: Prospective randomised trial of three treatments--namely distension only, steroid only, and steroid with distension. SETTING: Academic department of orthopaedic and accident surgery at Queen's Medical Centre, Nottingham. SUBJECTS: 47 patients (30 women) with capsulitis affecting 50 shoulders. INTERVENTIONS: Three intra-articular injections into the shoulder given at six week intervals by the same technique. MAIN OUTCOME MEASURES: Passive range of abduction, forward flexion, and external rotation; results of shoulder dynamometry measuring work done and torque produced; pain levels at rest and with resisted movement. RESULTS: All patients reported improvement during the study. Analysis of the mean improvements in abduction and forward flexion showed these to be significantly greater in the steroid with distension and steroid only groups than in the distension only group (mean improvements in abduction (degrees/week (95% confidence interval)) 4.3 (3.4 to 5.2), 3.4 (2.4 to 4.5), and 1.0 (-0.8 to 2.8) in the three groups respectively; mean improvements in flexion (degrees/week (95% confidence interval)) 3.6 (3.2 to 4.0), 3.3 (2.3 to 4.3), and 1.5 (0.5 to 2.5) respectively). Shoulder dynamometry failed to show a significant difference among the treatment groups. No severe complications occurred as a result of the injections, but two patients reported facial flushing related to the use of steroids. CONCLUSION: Intra-articular steroid injections have a useful role in the outpatient management of early capsulitis.

Air↗
PubMed1979

A simple reliable system for studying antigen-specific murine T cell proliferation.

Antigen-specific T cell proliferation can be readily elicited from the popliteal lymph node cells of mice which have received immunizations of antigen in the hind footpads. The advantages of our system over other published methods are (i) simplicity in method and materials, (ii) much improved reproducibility, (iii) negligible concomitant B cell proliferation, (iv) large degrees of antigen specific proliferation with very low background, and (v) complete dependence of the response on accessory cells or macrophages. These results were brought about by proper immunization procedures for mice and judicious choice of culture conditions. Our data show that the system is very suitable for the study of macrophage-T cell interaction in the induction of T cell proliferation as well as the genetic basis of responsiveness or non-responsiveness to protein and polypeptide antigens.

Animals↗
PubMed1978

Characterization and genetic control of the immune response to synthetic polypeptide antigens of defined geometry.

Both humoral and cell-mediated immune responses to the synthetic helical hapten-carrier conjugate poly-Glu-Tyr-Lys(TNP)-(Glu-Tyr-Ala)5 were found to be linked to the major histocompatibility locus in mice and guinea pigs. The responder mouse strains (H-2d haplotype) showed a primary IgM response with an IgG component appearing after the secondary immunization. The antibody response was accompanied by a positive DTH reaction in responder strains. Nonresponder mice (H-2b or H-2k haplotypes) showed neither IgM nor IgG antibodies and the DTH reaction was negative. Administration of the antigen as a complex with an immunogenic carrier was not effective in inducing a response in nonresponder mice. In guinea pig studies, it was found that strain 2 animals were able to mount an antibody response against the TNP-hapten and a DTH response against the polypeptide backbone. Strain 13 animals gave no anti-TNP antibodies at the lower dose levels and DTH activity was entirely negative for all doses of immunizing antigen. Replacement of the TNP hapten by the arsanilazo dipeptide derivative, BOC-gly-ARA-tyrosine, converted the nonresponder strain 13 guinea pigs into complete responders showing antibody and DTH reactions to both the hapten and the polypeptide backbone.

Animals↗