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Biomedical subjects

M A Dixon

Publications and source records attributed to M A Dixon.

13 recordsLinked to original sources
PubMed2001

The biofiltration of indoor air: air flux and temperature influences the removal of toluene, ethylbenzene, and xylene.

An alternative approach to maintaining indoor air quality may be the biofiltration of air circulated within the space. A biofilter with living botanical matter as the packing medium reduced concentrations of toluene, ethylbenzene, and o-xylene concurrently present at parts per billion (volume) in indoor air. The greatest reduction in concentrations per pass was under the slowest influent air flux (0.025 m s(-1)); however, the maximum amount removed per unit time occurred under the most rapid flux (0.2 m s(-1)). There was little difference between the different compounds with removal capacities of between 1.3 and 2.4 micromol m(-3) biofilter s(-1) (between 0.5 and 0.9 g m(-3) biofilter h(-1)) depending on influent flux and temperature. Contrary to biofilters subjected to higher influent concentrations, the optimal temperatures for removal by this biofilter decreased to less than 20 degrees C at the most rapid flux for all three compounds. Microbial activity was decreased at these cooler temperatures suggesting the biofilter was not microbially limited but rather was limited by the availability of substrate. The cooler temperatures allowed greater partitioning of the VOCs into the water column which had a greater impact on removal than its reduction in microbial activity.

Air Pollutants↗
PubMed2000

The biofiltration of indoor air: implications for air quality.

An alternative method of maintaining indoor air quality may be through the biofiltration of air recirculating within the structure rather than the traditional approach of ventilation. This approach is currently being investigated. Prior to its acceptance for dealing with volatile organic compounds (VOCs) and CO2, efforts were made to determine whether the incorporation of this amount of biomass into the indoor space can have an (negative) impact on indoor air quality. A relatively large ecologically complex biofilter composed of a ca. 10 m2 bioscrubber, 30 m2 of plantings and a 3,500 litre aquarium were established in a 160 m2 'airtight' room in a recently constructed office building in downtown Toronto. This space maintained ca. 0.2 air changes per hour (ACH) compared to the 15 to 20 ACH (with a 30% refresh rate) of other spaces in the same building. Air quality parameters of concern were total VOCs (TVOCs), formaldehyde and aerial spore counts. TVOC and formaldehyde levels in the biofilter room were the same or significantly less than other spaces in the building despite a much slower refresh rate. Aerial spore levels were slightly higher than other indoor spaces but were well within reported values for 'healthy' indoor spaces. Levels appeared to be dependent on horticultural management practices within the space. Most genera of fungal spores present were common indoors and the other genera were associated with living or dead plant material or soil. From these results, the incorporation of a large amount of biomass associated with indoor biofilters does not in itself lower indoor air quality.

Air Pollution, Indoor↗
PubMed2000

Resting energy expenditure in disorders of propionate metabolism.

OBJECTIVES: During intercurrent illness children with methylmalonic acidemia were found to have increased resting energy expenditure (REE). We measured REE in children with disorders of propionate metabolism (methylmalonic and propionic acidemia) when they were well and compared the values with those predicted by the Schofield equation. STUDY DESIGN: Prospective study in tertiary care facility. REE was measured with open-circuit indirect calorimetry under standardized conditions. Predicted REE values were calculated with the Schofield equation. Fourteen subjects with propionic acidemia (n = 3) and methylmalonic acidemia (n = 11) were studied. RESULTS: The median REE was 690 kcal/d (range 186 to 1687 kcal/d), which is significantly reduced, representing 80% +/- 18% of that predicted by the Schofield height and weight equation (P <.01). REE was significantly lower in female compared with male patients for unknown reasons. There were no differences with age or neurologic state. REE was not further reduced in those with chronic renal failure. CONCLUSION: REE in patients with disorders of propionate metabolism is reduced when they are well.

Amino Acid Metabolism, Inborn Errors↗
PubMed1999

Sealed environment chamber for canopy light interception and trace hydrocarbon analyses.

Two sealed chambers were constructed, each measuring approximately 4.5 m x 3 m x 2.5 m (LxWxH). Heat exchangers and air handling components were integrated within the sealed environment. Construction materials were chosen to minimize off-gassing and oxidation. Acceptable materials included stainless steel, Teflon (TM), glass and Heresite (TM) or baked enamel coated metal parts. The glass-topped chambers have externally mounted microwave powered light sources providing minimum PAR at canopy level of 1000 micrometers m-2 s-1. Major gases (CO2, O2) were monitored. Other environmental variables relevant to plant production (humidity, temperature, nutrient solution) were monitored and controlled continuously. Typical environment control capability and system specifications are presented. The facility is described as a venue ideally suited to address specific research objectives in plant canopy light interception, such as the roles of novel microwave powered overhead and inner-canopy light sources for dense plant canopies. In addition, control of recycled hydroponic nutrient solutions and analysis of trace atmospheric hydrocarbons in the context of sealed environment life support can be concurrently monitored.

Air Conditioning↗
PubMed1999

Regulating plant/insect interactions using CO2 enrichment in model ecosystems.

The greenhouse environment is a challenging artificial ecosystem in which it is possible to study selected plant/insect interaction in a controlled environment. Due to a combination of "direct" and "indirect" effects of CO2 enrichment on plant photosynthesis and plant development, canopy productivity is generally increased. In this paper, we discuss the effects of daytime and nighttime CO2 enrichment protocols on gas exchange of pepper plants (Capsicum annuum L, cv Cubico) grown in controlled environments. In addition, we present the effects of thrips, a common Insect pest, on the photosynthetic and respiratory activity of these plant canopies. Carbon dioxide has diverse effects on the physiology and mortality of insects. However, our data indicate that thrips and whiteflies, at least, are not killed "directly" by CO2 levels used to enhance photosynthesis and plant growth. Together the data suggest that the insect population is affected "indirectly" by CO2 and that the primary effect of CO2 is via its effects on plant metabolism.

Animals↗
PubMed1998

An investigation of tactile and visual stimuli in the roadway environment.

208 motorists were observed at Florida International University, in Miami, Florida as part of a study of the influence of speed humps on motorists' behavior at pedestrian crossings. It was hypothesized that the presence of a speed hump will affect motorists' behavior by compelling them either to yield or stop at a pedestrian crossing to enable a pedestrian to cross safely. A between-subjects experimental design was employed to measure motorists' reactions. Analysis indicated that the relationship is strong between drivers' behavior and the presence or absence of this roadway stimulus. There was also evidence that female drivers may take more precautionary actions than male drivers. This information is useful for roadway designers and traffic psychologists.

Accidents, Traffic↗
PubMed1998

The use of biofilters to improve indoor air quality: the removal of toluene, TCE, and formaldehyde.

A biofilter composed of a scrubber, a hydroponic planting system, and an aquatic system with green plants as a base maintained air quality within part of a modern office building. The scrubber was composed of five parallel fiberglass modules with external faces of porous lava rock. The face, largely covered with mosses, was wetted by recirculating water. Air was drawn through the scrubber and the immediately adjacent hydroponic region by a dedicated air handling system. The system was challenged for 4 weeks with three common indoor organic pollutants and removed significant amounts of all compounds. A single pass through the scrubber removed 10% of the trichloroethylene and 50% of the toluene. A single pass lowered formaldehyde air concentrations to 13 micrograms m-3 irrespective of influent levels (ranging between 30 and 90 micrograms m-3). The aquatic system accumulated trichloroethylene but neither toluene nor formaldehyde, suggesting the rapid breakdown of these materials. The botanical components removed some pollutants.

Air Conditioning↗
PubMed1996

Uncooked cornstarch--efficacy in type I glycogenosis.

Uncooked cornstarch (UCCS) loads in 14 patients with type 1 glycogenosis revealed that satisfactory glycaemia was achieved for a median of 4.25 hours (range 2.5 to 6). Length of glycaemia was related weakly to UCCS dose, but not to patient age or measures of metabolic control. Careful monitoring is required during UCCS treatment.

Adolescent↗
PubMed1992

Intercurrent illness in inborn errors of intermediary metabolism.

Metabolic decompensation may occur in patients with disorders of intermediary metabolism during intercurrent illness. To prevent complications it is normal practice to change the diet to an 'emergency regimen'. The mainstay of this is a high carbohydrate intake, using soluble glucose polymer, given as frequent drinks by day and during the night. Additional therapy is given for some disorders. Practical details of the treatment are outlined.

Acidosis↗
PubMed1986

Families of adolescent clients and nonclients: their environments and help-seeking behaviors.

Family demographic characteristics, family structure, family environment, and help-seeking variables were explored through interviews with two groups of Afro-American adolescents, including 52 clients and 52 nonclients. One parent of each adolescent was also interviewed. The ratio of single-parent families in the two groups differed significantly. Using one-way analysis of variance, significant differences were found between the means of the groups on five of the ten Family Environment Scale (FES) subscales. The family groups differed significantly on only one help-seeking variable, use of formal helpers. Adolescent client families reported using formal helpers more than did adolescent nonclient families (F = 2.69; df 102; p less than 0.05).

Adolescent↗
PubMedDate not supplied

Geriatric depression.

In late life, depression is the most prevalent functional psychiatric disorder. Because the presentation may be multicausal and clinically complex, early assessment of biologic and psychosocial factors, diagnosis, and appropriate referral are important in ameliorating the associated morbidity and mortality. Nurses must have current knowledge and skills to assess mood states of elderly persons and to implement appropriate interventions. Successful management of depression in the elderly results in a reformulation of purpose and an enhanced quality of life.

Age Factors↗