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Biomedical subjects

P P David

Publications and source records attributed to P P David.

6 recordsLinked to original sources
PubMed1997

Integrating biological treatment of crop residue into a hydroponic sweetpotato culture.

Residual biomass from hydroponic culture of sweetpotato [Ipomoea batatas (L.) Lam.] was degraded using natural bacterial soil isolates. Sweetpotato was grown for 120 days in hydroponic culture with a nutrient solution comprised of a ratio of 80% modified half Hoagland solution to 20% filtered effluent from an aerobic starch hydrolysis bioreactor. The phytotoxicity of the effluent was assayed with Waldmann's Green' lettuce (Lactuca sativa L.) and the ratio selected after a 60-day bioassay using sweetpotato plants propagated vegetatively from cuttings. Controlled environment chamber experiments were conducted to investigate the impact of filtrate from biological treatment of crop residue on growth and storage root production with plants grown in a modified half Hoagland solution. Incorporation of bioreactor effluent, reduced storage root yield of 'Georgia Jet' sweetpotato but the decrease was not statistically significant when compared with yield for plants cultured in a modified half Hoagland solution without filtrate. However, yield of 'TU-82-155' sweetpotato was significantly reduced when grown in a modified half Hoagland solution into which filtered effluent had been incorporated. Total biomass was significantly reduced for both sweetpotato cultivars when grown in bioreactor effluent. The leaf area and dry matter accumulation were significantly (P < 0.05) reduced for both cultivars when grown in solution culture containing 20% filtered effluent.

Biodegradation, Environmental↗
PubMed1996

Nutrient management effects on sweetpotato genotypes under controlled environment.

Sweetpotato is one of several crops recommended by National Aeronautics and Space Administration (NASA) for bioregenerative life support studies. One of the objectives of the Tuskegee University NASA Center is to optimize growth conditions for adaptability of sweetpotatoes for closed bioregenerative systems. The role of nutrient solution management as it impacts yield has been one of the major thrusts in these studies. Nutrient solution management protocol currently used consists of a modified half Hoagland solution that is changed at 14-day intervals. Reservoirs are refilled with deionized water if the volume of the nutrient solution was reduced to 8 liters or less before the time of solution change. There is the need to recycle and replenish nutrient solution during crop growth, rather than discard at 14 day intervals as previously done, in order to reduce waste. Experiments were conducted in an environmental growth room to examine the effects of container size on the growth of several sweetpotato genotypes grown under a nutrient replenishment protocol. Plants were grown from vine cuttings of 15cm length and were planted in 0.15 x 0.15 x 1.2m growth channels using a closed nutrient film technique system. Nutrient was supplied in a modified half strength Hoagland's solution with a 1:2.4 N:K ratio. Nutrient replenishment protocol consisted of daily water replenishment to a constant volume of 30.4 liters in the small containers and 273.6 liters in the large container. Nutrients were replenished as needed when the EC of the nutrient solution fell below 1200 mhos/cm. The experimental design used was a split-plot with the main plot being container size and genotypes as the subplot. Nine sweetpotato genotypes were evaluated. Results showed no effect of nutrient solution container size on storage root yield, foliage fresh and dry mass, leaf area or vine length. However, plants grown using the large nutrient solution container accumulated more storage root dry mass than those with the small containers. Although plants grown with the smaller containers showed greater water uptake, plant nutrient uptake was lower than with the larger container. All genotypes evaluated showed variation in their responses to all parameters measured.

Biomass↗
PubMed1994

Effects of several environmental factors on sweetpotato growth.

Effects of relative humidity, light intensity and photoperiod on growth of 'Ga Jet' and 'TI-155' sweetpotato cultivars, using the nutrient film technique (NFT), have been reported. In this study, the effect of ambient temperature regimes (constant 28 degrees C and diurnal 28:22 degrees C day:night) and different CO2 levels (ambient, 400, 1000 and 10000 microliters/L--400, 1000 and 10000 ppm) on growth of one or both of these cultivars in NFT are reported. For a 24-h photoperiod, no storage roots were produced for either cultivar in NFT when sweetpotato plants were grown at a constant temperature of 28 degrees C. For the same photoperiod, when a 28:22 degrees C diurnal temperature variation was used, there were still no storage roots for 'TI-155' but the cv. 'Ga Jet' produced 537 g/plant of storage roots. For both a 12-h and 24-h photoperiod, 'Ga Jet' storage root fresh and dry weight tended to be higher with a 28:22 degrees C diurnal temperature variation than with a constant 28 degrees C temperature regime. Preliminary results with both 'Ga Jet' and 'TI 155' cultivars indicate a distinctive diurnal stomatal response for sweetpotato grown in NFT under an ambient CO2 level. The stomatal conductance values observed for 'Ga Jet' at elevated CO2 levels indicated that the difference between the light- and dark-period conductance rates persisted at 400, 1000, and 10000 microliters/L.

Biomass↗
PubMed1982

Strategies for improving the work status of patients after coronary artery bypass surgery.

Postoperative work status was evaluated by follow-up questionnaire in 326 men who underwent coronary bypass graft surgery (CABG) between September 1969 and December 1972 (mean follow-up 30 months) and in 1217 men younger than age 60 years operated upon between January 1973 and June 1978 (mean follow-up 36 months). Work status was also assessed 1 year after operation in 59 men younger than age 60 years enrolled in a pilot rehabilitation program between November 1978 and March 1980 and in 62 comparable patients who underwent CABG during the same period but did not participate in the program. The percentage of patients working at completion of follow-up was 58% in the first survey, 61% in the second survey, 86% in the pilot study and 82% in the control group. The percentages of patients who resumed work during follow-up were 69%, 76%, 92% and 89% in the respective groups. This improvement was related primarily to a shorter period of preoperative unemployment; the percentage of patients operated on after less than 3 months of inactivity increased from 20% between 1969 and 1972, to 50% between 1973 and 1978, to 84% in 1979-1980. The prognosis for return to work was influenced, in order of predictive value, by the length of preoperative unemployment, type of physical activity in preoperative occupation, noncardiovascular illness, education, anginal class and duration of symptoms. Of patients with a good or excellent preoperative prognosis, 94% were working 1 year after CABG. We conclude that the working status of patients after CABG is excellent in subgroups with preoperative unemployment of 3 months or less and in a socioeconomic level above poverty; application of an individualized postoperative rehabilitation program should be limited to patients whose prognosis for return to work is poor according to the above predictive factors and the psychosocial evaluation.

Adult↗