Biomedical subjects

B G Drake

Publications and source records attributed to B G Drake.

10 recordsLinked to original sources

PubMed2004

Engineering concepts for inflatable Mars surface greenhouses.

A major challenge of designing a bioregenerative life support system for Mars is the reduction of the mass, volume, power, thermal and crew-time requirements. Structural mass of the greenhouse could be saved by operating the greenhouse at low atmospheric pressure. This paper investigates the feasibility of this concept. The method of equivalent system mass is used to compare greenhouses operated at high atmospheric pressure to greenhouses operated at low pressure for three different lighting methods: natural, artificial and hybrid lighting.

Air Conditioning↗

PubMed2003

The clonal structure of Quercus geminata revealed by conserved microsatellite loci.

The scrub oak communities of the southeastern USA may have existed at their present locations for thousands of years. These oaks form suckers, and excavations of root systems suggest that clones may occupy very large areas. Resolution of the clonal nature of scrub oaks is important both to manage the tracts of this ecosystem that remain, and in conducting long-term ecological studies, where the study area must substantially exceed the area occupied by any single clone. Microsatellites were used to determine the genetic diversity of a dominant oak species within a 2-ha long-term experimental site on Merritt Island at the Kennedy Space Center. This area contains a long-term study of the effects of elevated CO2 on the ecosystem. Conservation of seven microsatellite loci, previously identified in the sessile oak, Quercus petraea, was tested in two Florida scrub oak species, Q. geminata and Q. myrtifolia. Sequence analysis revealed that all seven microsatellite loci were conserved in Q. geminata and five loci were conserved in Q. myrtifolia. Six microsatellite loci were polymorphic in Q. geminata and these were subsequently used to investigate the clonal structure of the Q. geminata population. Twenty-one unique combinations of microsatellites, or haplotypes, occurred only once, whereas the remaining 26 individuals belonged to a total of seven different haplotypes. Trees with identical haplotypes were in close proximity, supporting the interpretation that they were clones. The results showed that there is significant genetic diversity within the 2-ha experimental site. Microsatellites provided a powerful and noninvasive tool for distinguishing individual genotypes and determining an adequate area for long-term ecosystem studies.

Base Sequence↗

PubMed1996

The role of public opinion in drug resource allocation decisions.

Drug resource allocation decisions have a very real and direct impact on the public, due to cost and availability constraints resulting from these decisions. This presents an opportunity for public opinion to play an important role in influencing decisions that have far-reaching effects. Public opinion regarding pharmaceutical issues is influenced by drug companies, special interest groups, researchers and others. Since these groups often have conflicting goals, they may send contradictory messages to the public. In this article, we examine the issues of who comprises the public, how public opinion is influenced and what impact public opinion does and should have on drug resource allocation decisions. We emphasise that, for appropriate resource allocation decisions to be made, there is a continuing need to conduct high quality outcomes research and to continue the trend of increasing interest in how drugs are used rather than how much is sold or how much they cost. There is also a major role for pharmacoeconomic research to play in this issue, with a real need to make such research accessible and understandable by the public, including patients, physicians, pharmacists and policy makers, so that policy decisions can be based on such research.

Drug Therapy↗

PubMed1995

Patient outcomes following unicompartmental or bicompartmental knee arthroplasty. A meta-analysis.

The purpose of this study was to summarize the literature describing patient outcomes following unicompartmental and bicompartmental knee arthroplasty. Original studies were included in this meta-analysis if they enrolled 10 or more patients at the time of an initial knee arthroplasty and measured patient outcomes using a global knee rating scale. Forty-six studies on unicompartmental prostheses and 18 studies on bicompartmental prostheses met these criteria. For unicompartmental studies, the total number of enrolled patients was 2,391, with a mean enrollment of 47 patients and a mean follow-up period of 4.6 years. The mean patient age was 66 years; 67% were women, 75% had osteoarthritis, and 16% underwent bilateral knee arthroplasty. The mean postoperative global rating scale score was 80.9. The overall complication rate was 18.5% and the revision rate was 9.2%. Studies published after 1987 reported better outcomes, but also tended to enroll older patients and patients with osteoarthritis and higher preoperative knee rating scores. For bicompartmental studies, the total number of enrolled patients was 884, with a mean enrollment of 44 patients and a mean follow-up period of 3.6 years. The mean patient age was 61 years; 79% were women, 31% had osteoarthritis, and 29% underwent a bilateral arthroplasty. The mean postoperative global rating scale score was 78.3. The overall complication rate was 30% and the revision rate was 7.2%. Although bicompartmental studies reported lower mean postoperative global rating scale scores, these studies tended to enroll patients with worse preoperative knee rating scores. Recent improvements in patient outcomes following unicompartmental knee arthroplasty appear to be due, at least partially, to changes in patient selection criteria. Patient outcomes appear to be worse for bicompartmental arthroplasties than for other prosthetic designs; however, patients enrolled in these studies had more poorly functioning knees before surgery and actually had greater absolute improvements in global knee rating scores.

Aged↗

PubMed1994

Patient outcomes following tricompartmental total knee replacement. A meta-analysis.

OBJECTIVE: To provide estimates of patient outcomes following tricompartmental knee replacement and to examine variation in outcomes due to patient and prosthesis characteristics. DATA SOURCES: English-language articles identified through a computerized literature search and bibliography review. STUDY SELECTION: Studies were included if they enrolled 10 or more patients at the time of initial knee replacement and measured patient outcomes using a global knee-rating scale. DATA EXTRACTION: Each study was subjected to a blinded qualitative assessment and unblinded abstraction of patient characteristics, surgical techniques, and outcomes. DATA SYNTHESIS: A total of 130 studies reporting patient outcomes on 154 cohorts satisfied inclusion criteria. The total number of enrolled patients was 9879 with a mean enrollment of 64.1 patients. The mean follow-up was 4.1 years. The mean patient age was 65.0 years, 71.7% of patients were women, 62.6% had osteoarthritis, and 26.6% underwent bilateral knee replacement. Global rating scale scores improved by 100% for the typical enrolled patient, and 89.3% of patients reported good or excellent outcomes. Anatomic classification of the prosthesis, percentage of enrolled patients with osteoarthritis, publication year, and number of enrolled patients explained 27% of the variation in reported mean postoperative global rating scale scores. The weighted mean complication rate was 18.1%, and the mean mortality rate per year of follow-up was 1.5%. The overall rate of revision during 4.1 years was 3.8%. CONCLUSIONS: Tricompartmental knee replacement was a safe and effective procedure for the patients reported in these studies. The knee pathology and the type of prosthesis were significant predictors of outcomes. Limitations in the reporting style of these articles severely constrain the ability to explore variation in outcomes due to study, patient, or prosthesis characteristics and restrict their generalizability.

Aged↗

PubMed1994

Global rating systems used in assessing knee arthroplasty outcomes.

Global, aggregated knee rating systems are commonly used to assess patient outcomes following knee arthroplasty. In this study, the authors performed a systematic literature search and found that 17% of the English-language studies addressing primary knee arthroplasty reported on patient outcomes following the procedure using a standardized global rating system. The authors describe, in detail, the rating systems' development and format. This study found 34 different rating systems represented in the literature from 1972 to 1992. Great variability was found in the rating systems' design and utilization. Additionally, these condition-specific, physician-based rating systems did not have documented studies demonstrating their reliability or validity. Future research will need to address the issues of selecting and aggregating outcome measures and of deriving any necessary weighting schemes. The ability of researchers to compare patient outcomes across studies will be enhanced when there is consistency in reported outcome measures.

Humans↗

PubMed1991

Effect of the Long-Term Elevation of CO(2) Concentration in the Field on the Quantum Yield of Photosynthesis of the C(3) Sedge, Scirpus olneyi.

CO(2) concentration was elevated throughout 3 years around stands of the C(3) sedge Scirpus olneyi on a tidal marsh of the Chesapeake Bay. The hypothesis that tissues developed in an elevated CO(2) atmosphere will show an acclimatory decrease in photosynthetic capacity under light-limiting conditions was examined. The absorbed light quantum yield of CO(2) uptake (ø(abs) and the efficiency of photosystem II photochemistry were determined for plants which had developed in open top chambers with CO(2) concentrations in air of 680 micromoles per mole, and of 351 micromoles per mole as controls. An Ulbricht sphere cuvette incorporated into an open gas exchange system was used to determine ø(abs) and a portable chlorophyll fluorimeter was used to estimate the photochemical efficiency of photosystem II. When measured in an atmosphere with 10 millimoles per mole O(2) to suppress photorespiration, shoots showed a ø(abs) of 0.093 +/- 0.003, with no statistically significant difference between shoots grown in elevated or control CO(2) concentrations. Efficiency of photosystem II photochemistry was also unchanged by development in an elevated CO(2) atmosphere. Shoots grown and measured in 680 micromoles per mole of CO(2) in air showed a ø(abs) of 0.078 +/- 0.004 compared with 0.065 +/- 0.003 for leaves grown and measured in 351 micromoles per mole CO(2) in air; a highly significant increase. In accordance with the change in ø(abs), the light compensation point of photosynthesis decreased from 51 +/- 3 to 31 +/- 3 micro-moles per square meter per second for stems grown and measured in 351 and 680 micromoles per mole of CO(2) in air, respectively. The results suggest that even after 3 years of growth in elevated CO(2), there is no evidence of acclimation in capacity for photosynthesis under light-limited conditions which would counteract the stimulation of photosynthetic CO(2) uptake otherwise expected through decreased photorespiration.

Journal Article↗

PubMed1976

Seasonal changes in reflectance and standing crop biomass in three salt marsh communities.

Reflectance of red (656-705 nm) and infrared (776-826 nm) solar radiation and standing crop biomass were measured in three salt marsh communities at intervals of approximately 2 weeks between February and August 1974. Red reflectance declined at the onset of greening in each community and was correlated with standing crop of green biomass. Infrared reflectance increased substantially in the shrub community but less in the grass and sedge communities. The inverse of red reflectance was found to be a reliable predictor of green biomass in sedge and grass communities, but not in a shrub community.

Journal Article↗

PubMed1972

Aftereffects of low and high temperature pretreatment on leaf resistance, transpiration, and leaf temperature in xanthium.

Leaf resistance for water vapor (total diffusion resistance minus boundary layer resistance), transpiration, and leaf temperature were measured in attached leaves of greenhouse-grown Xanthium strumarium L. plants that had been pretreated for 72 hours with high (40 C day, 35 C night), or low (10 C day, 5 C night) air temperatures. Measurements were made in a wind tunnel at light intensity of 1.15 cal cm(-2) min(-1), air temperatures between 5 and 45 C, and wind speed of 65 cm sec(-1). Leaf resistances in low temperature pretreated plants were higher (8 to 27 sec cm(-1)) than in controls or high temperature pretreated plants (0.5 to 3 sec cm(-1)) at leaf temperatures between 5 and 25 C. Thus, the pretreatment influenced stomatal aperture.

Journal Article↗

PubMed1970

Temperature and transpiration resistances of xanthium leaves as affected by air temperature, humidity, and wind speed.

Transpiration and temperatures of single, attached leaves of Xanthium strumarium L. were measured in high intensity white light (1.2 calories per square centimeter per minute on a surface normal to the radiation), with abundant water supply, at wind speeds of 90, 225, and 450 centimeters per second, and during exposure to moist and dry air. Partitioning of absorbed radiation between transpiration and convection was determined, and transpiration resistances were computed.Leaf resistances decreased with increasing temperature (down to a minimum of 0.36 seconds per centimeter). Silicone rubber replicas of leaf surfaces proved that the decrease was due to increased stomatal apertures. At constant air temperature, leaf resistances were higher in dry than in moist air with the result that transpiration varied less than would have been predicted on the basis of the water-vapor pressure difference between leaf and air.The dependence of stomatal conductance on temperature and moisture content of the air caused the following effects. At air temperatures below 35 C, average leaf temperatures were above air temperature by an amount dependent on wind velocity; increasing wind diminished transpiration. At air temperatures above 35 C, leaf temperatures were below air temperatures, and increasing wind markedly increased transpiration. Leaf temperatures equaled air temperature near 35 C at all wind speeds and in moist as well as in dry air.

Journal Article↗