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Biomedical subjects

D Lucas

Publications and source records attributed to D Lucas.

137 records · Page 8Linked to original sources
PubMedDate not supplied

Branch migration and the international dispersal of families.

This paper discusses the dispersal of facilities where family members migrate to different destination countries. Terminology for internationally dispersed families is proposed, and the term branch migration is suggested for the migration of related people from the same source country to different destination countries. Data from two 1993 surveys of senior secondary students show that 22% of Sydney students and 20% of Hong Kong students have relatives in two or more other countries. The data suggest that many Asian migrant families have branched between the US, Canada, Australia and other migrant-receiving nations. The causes and implications of the international dispersal of families are discussed.

Asia↗
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Release in vivo of Met-enkephalin and encrypted forms of Met-enkephalin from brain and spinal cord of the anesthetized cat.

Processing of the proenkephalin molecule will result in peptide fragments in which the pentapeptide YGGFM is included. We have employed a molecular sieve (2 kDa) separation, enzyme hydrolysis radioimmunoassay (RIA) treatment sequence which permits concurrent measurement of Met-enkephalin (Enk) and several enkephalin-encrypting (X-Enk) peptides in a single sample. Using this protocol, the release of Enk and X-Enk (total Enk-Enk) greater and less than 2 kDa from spinal cord and the mesencephalic aqueductal grey was assessed under resting conditions and during stimulation of the sciatic nerve in the chloralose-urethane anesthetized cat. Under resting conditions measurable levels of Enk (10.5 +/- 4.7; 9.1 +/- 2.1 pg/min) and X-Enk (47.8 +/- 19.7; 45.7 +/- 12.3 pg/min) are found in aqueductal and spinal superfusates, respectively. The X-Enk measured under resting and evoked conditions in aqueductal and spinal perfusates is associated almost exclusively (greater than 90-95%) with fragments greater than 2 kDa in size. There results, showing the relative absence of detectable levels of X-Enk forms greater than 2 kDa, were confirmed by reverse phase chromatography. During sciatic nerve stimulation, the levels of both Enk and X-Enk were mildly elevated in spinal and ventricular perfusates. With the addition of thiorphan (10(-5) M), though there was no effect on the resting release of either Enk or X-Enk, the levels of Enk measured under evoked conditions were significantly augmented in both ventricular and spinal perfusates.

Amino Acid Sequence↗
PubMedDate not supplied

Excimer laser fragmentation-fluorescence spectroscopy as a method for monitoring ammonium nitrate and ammonium sulfate particles.

Excimer laser fragmentation-fluorescence spectroscopy (ELFFS) is shown to be an effective detection strategy for ammonium nitrate and ammonium sulfate particles at atmospheric pressure and room temperature. Following photofragmentation of the ammonium salt particle, fluorescence of the NH fragment is observed at 336 nm. The fluorescence signal is shown to depend linearly on particle surface area for laser intensities varying from 1.2 x 10(8) to 6 x 10(8) W/cm2. The 100 shot (1 s) detection limits for ammonium nitrate range from 20 ppb for 0.2 microm particles to 125 ppb for 0.8 microm particles, where these concentrations are expressed as moles of ammonium ion per mole of air. For ammonium sulfate, the 100 shot (1 s) detection limits vary from 60 ppb for 0.2 microm particles to 500 ppb for 1 microm particles. These detection limits are low enough to measure ammonium salt particles that form in the exhaust of combustion processes utilizing ammonia injection as a nitric oxide control strategy.

Air Pollutants↗
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An experimental and numerical study of the thermal oxidation of chlorobenzene.

A combustion-driven flow reactor was used to examine the formation of chlorinated and non-chlorinated species from the thermal oxidation of chlorobenzene under post-flame conditions. Temperature varied from 725 to 1000 K, while the equivalence ratio was held constant at 0.5. Significant quantities of chlorinated intermediates, vinyl chloride and chlorophenol, were measured. A dominant C-Cl scission destruction pathway seen in pyrolytic studies was not observed. Instead, hydrogen-abstraction reactions prevailed, leading to high concentrations of chlorinated byproducts. The thermal oxidation of benzene was also investigated for comparison. Chemical kinetic modeling of benzene and chlorobenzene was used to explore reaction pathways. Two chlorobenzene models were developed to test the hypothesis that chlorobenzene oxidation follows a CO-expulsion breakdown pathway similar to that of benzene. For the temperatures and equivalence ratio studied, hydrogen abstraction by hydroxyl radicals dominates the initial destruction of both benzene and chlorobenzene. Chlorinated byproducts (i.e., chlorophenol and vinyl chloride) were formed from chlorobenzene oxidation in similar quantities and at similar temperatures to their respective analogue formed during benzene oxidation (i.e., phenol and ethylene).

Journal Article↗
PubMedDate not supplied

Evaluation of combustion by-products of MTBE as a component of reformulated gasoline.

Methyl tertiary-butyl ether (MTBE) is a gasoline oxygenate that is widely used throughout the US and Europe as an octane-booster and as a means of reducing automotive carbon monoxide (CO) emissions. The combustion by-products of pure MTBE have been evaluated in previous laboratory studies, but little attention has been paid to the combustion by-products of MTBE as a component of gasoline. MTBE is often used in reformulated gasoline (RFG), which has chemical and physical characteristics distinct from conventional gasoline. The formation of MTBE by-products in RFG is not well-understood, especially under "worst-case" vehicle emission scenarios such as fuel-rich operations, cold-starts or malfunctioning emission control systems, conditions which have not been studied extensively. Engine-out automotive dynamometer studies have compared RFG with MTBE to non-oxygenated RFG. Their findings suggest that adding MTBE to reformulated gasoline does not impact the high temperature flame chemistry in cylinder combustion processes. Comparison of tailpipe and exhaust emission studies indicate that reactions in the catalytic converter are quite effective in destroying most hydrocarbon MTBE by-product species. Since important reaction by-products are formed in the post-flame region, understanding changes in this region will contribute to the understanding of fuel-related changes in emissions.

Journal Article↗
PubMedDate not supplied

Are personnel in transplant hospitals in favor of cadaveric organ donation? Multivariate attitudinal study in a hospital with a solid organ transplant program.

INTRODUCTION: A considerable number of professionals who work in a hospital could be against organ donation, which means that when the time comes, they could act as an obstacle to donation. The objective of this study was to analyze the attitude of hospital professionals toward organ donation and to determine the factors that influence this attitude in a Spanish center with a transplant program. MATERIALS AND METHODS: The study was carried out in a third-level Spanish hospital with a solid organ transplant program. A random sample was taken (n = 1262) and stratified by job category and type of service. Attitude was evaluated using a validated questionnaire. Contact was made in each service with the person responsible for each of the job categories in order to distribute the survey. The survey was completed anonymously and was self-administered. Student's t-test, the chi-squared test, and logistic regression analysis were applied in the statistical analysis. RESULTS: The survey completion rate was 93% (n = 1168). Most respondents were in favor of donation [69% (n = 808)]. Of those who are not in favor, 29% (n = 105) provide fear of apparent death as the reason whilst most do not give a reason (negative assertion; 57%; n = 206). There are many factors related to this attitude toward donation, which are evident in the multivariate analysis: (i) job category, in which physicians are twice as likely to be in favor of donation than ancillary personnel (OR = 2.02); (ii) a respondent's knowledge of brain death (OR = 1.64); (iii) having discussed the matter of organ donation and transplantation within the family (OR = 1.89); (iv) a preference for other options apart from burial (OR = 3.66); (v) being in favor of the performance of autopsy if it were necessary (OR = 2.76); (vi) not being concerned about mutilation of the cadaver (OR = 2); and (vii) having a partner with a favorable attitude toward donation (OR = 2.2). CONCLUSIONS: Attitude toward cadaveric organ donation among personnel in a transplant hospital is similar to that described in the general public and is determined by many factors. The following factors are most noteworthy: (i) job category; (ii) knowledge of the concept of brain death; (iii) consideration of the matter of donation in the family; and (iv) fear of manipulation of the cadaver. In view of this attitude, which is similar to that of the general public, it is necessary to carry out promotion activities if we want to increase cadaveric donation rates.

Adult↗
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A regulated workforce?

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Allied Health Personnel↗
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Fertility and family planning in southern and central Africa.

Southern Africa comprises a zone where the total fertility rate is below 6 births per woman. To the north is a ring of countries with higher fertility and relatively low contraceptive prevalence rates. The experience of South Africa, Botswana, and Zimbabwe, which have successful family planning programs, is compared with that of neighboring countries.

Adult↗