Biomedical subjects
Publications and source records attributed to V G Harris.
Perpendicular magnetic anisotropy energy in rf magnetron sputtered amorphous TbFe films is measured to increase exponentially with pair-order anisotropy induced by the selective resputtering of surface adatoms during film growth.
We report the results of polarized Co EXAFS experiments on a series of CoPt3 films grown by molecular beam epitaxy on (100) MgO singe crystal substrates over a range of temperatures from 473 K to 1073 K. These samples exhibit substantial perpendicular magnetic anisotropy that is strongly dependent on the substrate growth temperature Tg. We measure a preference for in-plane Co-Co pairs that is correlated with the magnetic properties.
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Diffraction anomalous fine-structure (DAFS) experiments measure Bragg peak intensities as continuous functions of photon energy near a core-level excitation. Measuring the integrated intensity at each energy makes the experiments prohibitively slow; however, in many cases DAFS can be collected quickly by measuring only the peak intensity at the center of the rocking curve. A piezoelectric-actuator-driven stage has been designed and tested as part of a sample-angle feedback circuit for locking onto the maximum of the rocking curve while the energy is scanned. Although software peak-tracking requires only a simple calculation of diffractometer angles, it is found that the additional hardware feedback dramatically improves the reproducibility of the data.
A preliminary study of 329 colposcopy patients was conducted to investigate the prevalence of endocervical chlamydial infection using the VIDAS Chlamydia Enzyme Immune Assay (EIA) and Chlamydia Immune Fluorescent Antigen (IFA) collection kits. The overall antigen positive rates of five of the 329 (1.5%) in the study group compared exactly with the four out of the 260 (1.5%) in the gynaecological outpatient controls. Women in the age group 16-20 years had the highest Chlamydia detection rates (7%) followed by those aged 21-30 years (2.3%). Four of the 119 (3.4%) single women in the study group were Chlamydia antigen positive compared with one of the 210 (0.5%) married women (P < 0.005). Among the controls, three of the 65 (4.6%) single and one of the 195 (0.5%) married women were positive. In both the study and control populations, Chlamydia antigen was more prevalent among younger women and non-contraceptive users. Routine screening in colposcopy patients may not be cost effective, but a policy of selective screening in young single women aged 20 years or less should be considered. Larger sample studies using the more specific and sensitive DNA amplification techniques would have probably yielded higher detection rates and are recommended.
The inefficiency of the Ayres Spatula in detecting abnormality in cervical cytology has been demonstrated recently in a number of trials. In a randomized single-blind trial we have compared the Multispatula with the Ayres Spatula in a group of 158 women who previously had abnormal smears and had been referred to colposcopy clinics in the Lewisham and North Southwark Health Authority of London. The quality of the smears, as assessed by the presence or absence of endocervical cells, revealed that the Multispatula (87.3% pick-up) produced significantly better smears (p less than 0.005) compared with the Ayres Spatula (54.4% pick-up). In 149 smears collected with the Multispatula, atypia was confirmed. However, in only 129 smears taken with the Ayres Spatula were abnormal smears detected (p decreases less than 0.005). We concluded that the Multispatula produces a better quality smear which results in a decreased false negative rate in comparison with the Ayres Spatula.
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We questioned 181 healthy pregnant women about their urological symptoms during pregnancy; frequency and stress incontinence were commonest. The incidences of stress incontinence and urge incontinence were increased and that of hesitancy was decreased by pregnancy. Descent of the presenting part did not affect any of these symptoms.
Following a child playground equipment injury prevention project conducted in New York State in 1977, there was a 42 per cent reduction in playground equipment hazards, and a 22.4 per cent reduction in playground related injuries treated in the two largest hospitals of one of the program sites. Knowledge about unsafe playground practices and equipment hazards improved after the workshops for playground personnel. This approach to injury prevention deserves further study.
Oral glucose tolerance tests were performed during late pregnancy, on the second and fifth days of the puerperium and finally six weeks after delivery in a group of 12 healthy women. The glucose response showed no significant change from the pregnancy values on the second and fifth days of the puerperium but each woman had returned to 'normal' by the sixth week post partum. In contrast, the insulin response had returned to the non-pregnant value by the second day of the puerperium.
Two theories related to uterine action have been brought together to see whether the site of placental implantation influences the onset of labour: (1) that uterine contractions begin asymmetrically from a "pacemaker" in one uterine horn, and (2) that progesterone from the placenta blocks myometrial contractility primarily at the site of implantation. Case records were examined of 182 patients who had placental locations performed and who had a spontaneous onset of labour. Where the placenta was implanted in the right upper quadrant of the uterus labour occurred on average four days sooner than when it was implanted in the left upper quandrant: the difference was statistically significant.
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The genus Leptospira can be divided into three groups based on purine analogue sensitivity and lipase (trioleinase) activity. Group 1 contains members of the "parasitic complex" of leptospires which initially cannot grow in media containing 10 mug of 2,6-diaminopurine (DAP) per ml or 200 mug of 8-azaguanine per ml. In addition, leptospires in this group possess lipase activity. Group 2 also contains members of the "parasitic complex" of leptospires. Although these leptospires are similarly sensitive to 8-azaguanine, they differ from group 1 leptospires in that they grow in media containing 10 mug of DAP per ml, and they do not possess detectable lipase activity. Group 3 consists of leptospires belonging to the "biflexa complex." These leptospires are resistant to both purine analogues and have lipase activity.
A definite relationship exists between the resistance of leptospires to the antibody-complement system and virulence. Leptospires capable of producing either lethal or renal infections in hamsters or guinea pigs were resistant to the leptospiricidal action of antibody and complement. Avirulent leptospires, in contrast to the virulent organisms, were rapidly immobilized and killed by these serum substances. The change of a virulent culture to the avirulent state as a result of growth in culture media was accompanied by the loss of resistance to antibody and complement. Virulent leptospires were phenotypically altered when grown in the presence of the purine analogue, 8-azaguanine. The cells became sensitive to antibody and complement without a corresponding decrease in virulence. The basis for a leptospiral virulence factor, the ability to multiply in vivo, appears to reside in their capacity to resist the leptospiricidal activity of the host antibody-complement system. The immune leptospiricidal assay provides a simple and rapid method of determining the virulence of a culture.
The minimal growth temperature of the pathogenic leptospires is between 13 and 15 C. The saprophytic leptospires have a minimal growth temperature between 5 and 10 C, or approximately 5 C below that of the pathogens. The capability of the saprophytic leptospires to grow at temperatures below those which allow the growth of the pathogenic leptospires provides a simple method of discrimination. With an inoculum yielding approximately 8 x 10(7) cells per ml in the test medium and an incubation temperature of 13 C, the saprophytic leptospires were easily differentiated from the pathogenic leptospires. All 13 saprophytic leptospires tested grew in the 10% rabbit serum medium at 13 C, whereas none of the 20 pathogens grew during the 30-day incubation period.