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Biomedical subjects

D R Hall

Publications and source records attributed to D R Hall.

At least 19 recordsLinked to original sources
PubMed2006

Low-loss passive alignment of single-mode fibers in low-temperature cofired ceramics using CO2 laser fabricated U-grooves.

We report a step toward optoelectronic integration on low-temperature cofired ceramics substrates in the form of fiber alignment U-grooves. The precision of the CO2 laser machining of green state ceramic for this purpose is investigated. The groove-writing process with a speed of 1 mm/s was carried out in air at room temperature and ambient pressure. The process is to a large extent self-cleaning without any gas jet assist. By analysis of groove profiles after firing of a near-zero shrinkage green tape formulation, it is shown that the cutting accuracy is approximately 2 microm, which is at the fundamental limit set by the particle size (1-5 microm). We demonstrate low-loss butt coupling of <1 dB for single-mode fibers using the laser written U-grooves. The technique exhibits a potential for fabrication of low-cost fiber ribbon and fiber array connectors.

Journal Article↗
PubMed2006

High-throughput sample handling and data collection at synchrotrons: embedding the ESRF into the high-throughput gene-to-structure pipeline.

An automatic data-collection system has been implemented and installed on seven insertion-device beamlines and a bending-magnet beamline at the ESRF (European Synchrotron Radiation Facility) as part of the SPINE (Structural Proteomics In Europe) development of an automated structure-determination pipeline. The system allows remote interaction with beamline-control systems and automatic sample mounting, alignment, characterization, data collection and processing. Reports of all actions taken are available for inspection via database modules and web services.

Data Collection↗
PubMed2006

Postmenopausal hormone therapy and quality of life.

OBJECTIVE: To evaluate whether hormonal therapy (HT) had any significant effect on quality of life (QoL) in a selected group of postmenopausal women. METHODS: The study was conducted in a specialist private practice in Tygerberg, Cape Town, South Africa, over an 18-month period ending in July 2003. A questionnaire using the Utian Quality of Life (UQoL) scale was posted to all women with established postmenopausal status, seen over this period. 541 questionnaires were posted, 421 returned and 398 could be used. Women gave written informed consent. RESULTS: The average age of the women was 60 years. 313 women (78.6%) were using hormone therapy (HT) while 275 women (69.1%) reported concomitant medical problems. HT users had significantly higher scores in three of the four QoL domains, namely, occupational (p=0.046), emotional (p=0.03), and sexual (p=0.009). There was no significant difference in the health domain (p=0.2). CONCLUSION: This study found that post-menopausal South African women experienced that HT had a positive effect on global quality of life.

Emotions↗
PubMed2006

Localized CO2 laser damage repair of fused silica optics.

A technique has been developed for the localized treatment of laser damage sites in fused silica optics by CO2 laser melt-flow smoothing, by using a 50 to 125 microm diameter beam in a regime that avoids mass removal by ablation. A detailed calibration of the laser irradiance for the threshold ablation of craters was carried out for a range of beam diameters and pulses in the 20 micros to 200 ms range. The results agree with a thermal model that also provides estimates of the melt depth for the different irradiation conditions. Smoothing trials for glass melting at irradiance values just below the ablation threshold irradiance were conducted to determine the optimum conditions and limits for the smoothing process. The technique has been found to remove damage pits up to a depth of 0.5 microm, while the small melt depth associated with localized treatment limits the smoothing to a <or=5 microm lateral size.

Journal Article↗
PubMed2006

Identification of components of male-produced pheromone of coffee white stemborer, Xylotrechus quadripes.

The coffee white stem borer, Xylotrechus quadripes Chevrolat (Coleoptera: Cerambycidae), is the foremost pest of arabica coffee in India, Sri Lanka, China, Vietnam, and Thailand. Previous work showed that female beetles were attracted to traps baited with male beetles. Analyses of volatiles from male X. quadripes of Indian origin by gas chromatography (GC) linked to electroantennographic (EAG) recording from a female beetle antenna showed three male-specific components comprising more than 90% of the volatiles, two of which elicited EAG responses. The major EAG-active component was produced at up to 2 microg hr(-1) insect(-1) and was identified as (S)-2-hydroxy-3-decanone (I) by comparison of GC data, and mass (MS), infrared, and nuclear magnetic resonance (NMR) spectra with those of synthetic standards. The second component was identified as 3-hydroxy-2-decanone (II) produced in part by isomerization of I under the conditions of the GC analysis, although the NMR spectrum suggested it is naturally produced at up to 7% of I. The minor component that elicited an EAG response, present at 7% of the amount of I, was identified as (S,S)-2,3-dihydroxyoctane (III) from GC and MS data. 2-Hydroxy-3-octanone (0.2-0.5% of I), 2,3-decanedione (2% of I), 2-phenylethanol (3% of I), and octanoic acid (4% of I) were also identified in volatiles from male beetles. A general, stereospecific synthetic route to the enantiomers of 2-hydroxy-3-alkanones from the enantiomers of ethyl lactate was developed. The enantiomers of III were synthesized from (E)-2-octene by Sharpless asymmetric dihydroxylation. (S)-(I) was attractive to male X. quadripes in laboratory bioassays, but addition of (S,RS)-(III) at 10% of I reduced attractiveness. In field trials carried out in India with sticky, cross-vane traps, (S)- and (RS)-(I) attracted male X. quadripes and addition of (S,S)-(III) at 10% of I reduced attractiveness. Significant numbers of female Demonax balyi Pascoe (Coleoptera: Cerambycidae) were sometimes caught in traps baited with (S)-(I) alone.

Animals↗
PubMed2006

The effects of host physiology on the attraction of tsetse (Diptera: Glossinidae) and Stomoxys (Diptera: Muscidae) to cattle.

In Zimbabwe, studies were made of the numbers of tsetse (Glossina spp.) and stable flies (Stomoxys spp.) attracted to cattle of different nutritional status, age and sex. Host odours were analysed to determine the physiological basis of these differences and improved methods are described for measuring rates of production of kairomones. Seasonal fluctuations in host weight, related to changes in pasture quality, had no significant effect on attraction of tsetse or Stomoxys. However, both attraction to different individuals and carbon dioxide production by these individuals were strongly correlated with weight, suggesting a possible link. Attraction to the odour from different types of cattle decreased in the order ox>cow>heifer>calf, and oxen were twice as attractive as calves of less than 12 months old. Lactation did not alter the relative attractiveness of cows. Calves less than six months old produced lower levels of carbon dioxide, acetone, octenol and phenols than oxen, but for older calves and cows, levels of production of known kairomones and repellents were similar to those of an ox. Carbon dioxide produced by cattle varied according to time of day and the animal's weight; cattle weighing 500 kg produced carbon dioxide at a mean rate of 2.0 l min(-1) in the morning and 2.8 l min(-1) in the afternoon compared to respective rates of 1.1 and 1.9 l min(-1) for cattle weighing 250 kg. Artificially adjusting the doses of carbon dioxide produced by individual cattle to make them equivalent did not remove significant differences in attractiveness for tsetse but did for Stomoxys. Increasing the dose of carbon dioxide from 1 to 4 l min(-1) in a synthetic blend of identified kairomones simulating those produced by a single ox, increased attractiveness to tsetse but not to the level of an ox. The results suggest that the main sources of differences in the attractiveness of individual cattle are likely to be variation in the production of carbon dioxide and, for tsetse, other unidentified kairomone(s). The biological and practical implications of these findings are discussed.

Acetone↗
PubMed2005

The care and nurture of undulator data sets.

Undulator radiation is the X-ray source of choice for modern macromolecular crystallography beamlines. Here, the basic properties of undulator sources are described and it is indicated why they make such good X-ray sources for macromolecular crystallography. Collection of excellent data from these beamlines is not always straightforward; therefore, a number of rules are postulated for undulator data collection and guidelines are offered which will help to ensure a satisfactory experiment.

Crystallization↗
PubMed2005

The attitudes of two groups of South African women towards mode of delivery.

OBJECTIVE: To determine whether 2 specific groups of women prefer vaginal or abdominal delivery. METHODS: Forty-six black and 54 colored (of mixed race, the predominant population group) primigravidas and 59 black and 62 colored multigravidas were interviewed between April 2003 and February 2004 at Tygerberg Hospital, Tygerberg, South Africa. RESULTS: Among primigravidas, 89% of black women and 83% of colored women preferred vaginal delivery. Among the multigravidas, 86% of black women and 79% of colored women preferred vaginal delivery. Most women believed that they would recover more quickly (65%) and with less pain (32%) after vaginal delivery. Forty-one percent of all women viewed episiotomy as the greatest disadvantage of vaginal delivery, while 43% were unaware of any advantage to cesarean delivery. CONCLUSION: Most colored and black women preferred vaginal over cesarean delivery. A challenge to healthcare personnel is to educate women about both routes.

Adolescent↗
PubMed2005

Current patient perceptions on the menopause: a South African perspective.

OBJECTIVE: To evaluate current patient perspectives on the postmenopausal period in South Africa. METHODS: The study was conducted in a specialist private practice in Tygerberg, Cape Town, South Africa during 2004. All women with established postmenopausal status, seen over a period of 18 months, received a survey questionnaire by post. Of the 541 questionnaires that were posted, 421 were returned and 410 were used. Women gave written informed consent. RESULTS: The average age of the women was 60 years, with almost half (49%) greater than 10 years postmenopausal, and 78.5% were using hormonal therapy (HT). Of note is that 42% had been on HT for more than 10 years. The doctor was the most important source of information (87%), the most frequent reason for initiation of, and the second most frequent reason for discontinuation of therapy. The most important advantages of HT given were skeletal protection (85%) and treatment of vasomotor symptoms (70%), while development of breast cancer was given as the most prominent disadvantage (79%). CONCLUSION: This group of women was well informed regarding current indications and developments concerning HT. Despite their socioeconomic status, the doctor remained the key factor with regard to information and decision-making.

Adult↗
PubMed2004

Investigation of long-range female sex pheromone of the European tarnished plant bug, Lygus rugulipennis: chemical, electrophysiological, and field studies.

The European tarnished plant bug, Lygus rugulipennis, is an important pest of agricultural and horticultural crops throughout Europe. Adult male L. rugulipennis were previously shown to be attracted to traps baited with live virgin females, which suggests the females produce a sex pheromone. Volatiles produced by virgin female L. rugulipennis were shown to contain three components, hexyl butyrate, (E)-2-hexenyl butyrate, and (E)-4-oxo-2-hexenal which elicited electroantennographic (EAG) responses from males in analyses by linked gas chromatography-electroantennography (GC-EAG). They were produced in 1.5:1:0.08 ratio, respectively, by single females. Collections from 1, 2, or 4 virgin females showed the proportions of hexyl butyrate and (E)-4-oxo-2-hexenal to increase relative to that of (E)-2-hexenyl butyrate with increasing number of females. Although these compounds were found in body extracts of both male and female L. rugulipennis, they were not detected in volatiles released by virgin males. EAG dose-response studies showed that both males and females responded to these chemicals with minimal differences in sensitivity between the sexes or to the three components, except that males were more responsive than females to (E)-4-oxo-2-hexenal at the two highest doses tested. Release rates of the compounds from rubber septa, polyethylene vials, and polyethylene sachets were measured under laboratory conditions. Four field tests were carried out using sticky traps baited with all possible binary and tertiary combinations of the three chemicals using different combinations of dispensing systems. Catches of male L. rugulipennis in baited traps were similar to those in unbaited traps. Significantly fewer females were caught on traps baited with blends containing hexyl butyrate than on traps without hexyl butyrate or unbaited traps in one test and overall. The roles of the three compounds and possible reasons for their failure to attract males are discussed.

Aldehydes↗
PubMed2004

Responses of Teretrius nigrescens toward the dust and frass of its prey, Prostephanus truncatus.

Teretrius nigrescens is considered to be a specialized predator of Prostephanus truncatus, a serious pest of stored maize and dried cassava roots. Using a bait-bag behavioral bioassay, this investigation found T nigrescens to be strongly arrested by dust and frass produced by P. truncatus on maize, whereas responses to maize flour were weak. Attempts to increase the arrestiveness of flour by altering its physical properties (coarseness or particle size range) were unsuccessful. The arrestive property of dust/frass did not degrade with long-term storage nor did it volatilize or degrade with oven baking up to 150 degrees C. However, extraction with methanol and reapplication was successful in transferring the arrestive property from the dust/frass onto maize flour. The prey dust/frass also induced more oviposition than did maize flour, as judged by production of F1 offspring. The results provide strong evidence for the existence of a high boiling point compound(s) in P. truncatus dust/frass that acts as a contact kairomone for T nigrescens. This, or another compound(s) also seems to act as an oviposition stimulant for female T. nigrescens.

Animals↗
PubMed2003

Phenotypic plasticity of Rhyzopertha dominica pheromone signaling: the effects of different hosts and presence of conspecific females on male produced aggregation pheromone.

Male Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) release an aggregation pheromone consisting of a blend of two components, dominicalure 1 (D1) and Dominicalure 2 (D2). Pheromone from single insects, in different contexts, was collected and measured to determine if this signal is phenotypically plastic. Release rates were lowered when males were moved from maize grains to groundnut kernels or when moved from solitary occupation of maize grain to grain occupied by seven females. The pheromone release was increased again once these moves were reversed. The release of D1 was more affected than D2: thus, on groundnuts or in the presence of females, less pheromone was released and the proportion of D1 in the blend was lowered. Possible reasons for the modifications of the signal are discussed.

Animal Communication↗
PubMed2003

Minor components in the sex pheromone of legume podborer: Maruca vitrata development of an attractive blend.

The legume podborer, Maruca vitrata (syn. M. testulalis) (F.) (Lepidoptera: Pyralidae) is a pantropical pest of legume crops. Sex pheromone was collected by gland extraction or trapping of volatiles from virgin female moths originating in India, West Africa, or Taiwan. Analysis by GC-EAG and GC-MS confirmed previously published findings that (E,E)-10,12-hexadecadienal is the most abundant EAG-active component with 2-5% of (E,E)-10,12-hexadecadienol also present. At least one other EAG response was detected at retention times typical of monounsaturated hexadecenals or tetradecenyl acetates, but neither could be detected by GC-MS. Laboratory wind-tunnel bioassays and a field bioassay of blends of (E,E)-10,12-hexadecadienal with (E,E )-10,12-hexadecadienol and a range of monounsaturated hexadecenal and tetradecenyl acetate isomers indicated greatest attraction of males was to those including (E,E)-10,12-hexadecadienol and (E)-10-hexadecenal as minor components. In subsequent trapping experiments in cowpea fields in Benin, traps baited with a three-component blend of (E,E)-10,12-hexadecadienal and these two minor components in a 100:5:5 ratio caught significantly more males than traps baited with the major component alone, either two-component blend, or virgin female moths. Further blend optimization experiments did not produce a more attractive blend. No significant differences in catches were found between traps baited with polyethylene vials or rubber septa, or between lures containing 0.01 and 0.1 mg of synthetic pheromone. Significant numbers of female M. vitrata moths, up to 50% of total catches, were trapped with synthetic blends but not with virgin females. At present there is no clear explanation for this almost unprecedented finding, but the phenomenon may improve the predictive power of traps for population monitoring.

Animals↗
PubMed2003

The profile and complications of women with placental abruption and intrauterine death.

The aim of this study was to evaluate the profile and outcome of patients with placental abruption and intrauterine death. It was a retrospective study over 2 years from 1 January 1999 to 31 December 2000. All women (n = 96) presenting with placental abruption and intrauterine death at a tertiary referral center were identified from the records of weekly perinatal mortality meetings. Data were reviewed by a single researcher. Hypertensive disorders were diagnosed in 75 per cent (n = 72) women, most often at admission once intrauterine death had already occurred. Thirty-nine per cent had a previous history of hypertensive disease during pregnancy, placental abruption, intrauterine death, or preterm delivery. Twenty-two per cent of patients (n = 21) were unbooked. Major maternal complications occurred in 53 per cent of women. There were no maternal deaths. In conclusion, previous obstetric history and hypertensive disorders are important factors in women with placental abruption causing intrauterine death. Severe complications are common but careful management in a tertiary center can reduce their impact.

Abruptio Placentae↗