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Biomedical subjects

D R Paul

Publications and source records attributed to D R Paul.

8 recordsLinked to original sources
PubMed2006

The impact of the covert manipulation of macronutrient intake on energy intake and the variability in daily food intake in nonobese men.

OBJECTIVE: To investigate the effect of macronutrient composition on ad libitum food intake in nonobese men. DESIGN: Balanced, incomplete-block, crossover study where subjects received two of three treatments. Macronutrient composition was manipulated by providing 2.1 MJ/day high-carbohydrate (CHO), high-fat (FAT), and/or high-protein (PRO) drinks every day over the course of two, 8-week periods. SUBJECTS: In all, 12 healthy normal weight men (age: 39+/-9 years, BMI: 24.1+/-1.4 kg/m2). MEASUREMENTS: Ad libitum food intake was measured continuously for 16 weeks at the Beltsville Human Nutrition Research Center (BHNRC). Body composition (DEXA) and body weight were also measured. RESULTS: Average energy intake (EI) during weeks 1 and 2 was lower for CHO than FAT (P<0.05), but this effect disappeared by week 3. EI during CHO increased by 11% from week 1 to 8 through the increased selection of carbohydrate and protein-containing foods, but not fat foods. Food intake was variable, both between and within subjects, but was not related to macronutrient composition. CONCLUSION: EI appears to be influenced by macronutrient composition in the short-term when diets are modified, but the effect dissipates in a few weeks if the diet is maintained. These data suggest the presence of macronutrient-specific regulatory mechanisms in the body, but do not support the notion that a high intake of any of the three macronutrients suppresses EI over a prolonged period of time. The high variability in food intake does not appear to be related to macronutrient composition.

Adult↗
PubMed2005

The interlayer swelling and molecular packing in organoclays.

Understanding the interlayer swelling and molecular packing in organoclays is important to the formation and design of polymer nanocomposites. This paper presents recent experimental and molecular simulation studies on a variety of organoclays that show a linear relationship between the increase of d-spacing and the mass ratio between organic and clay. A denser molecular packing is observed in organoclays containing surfactants with hydroxyl-ethyl units. Moreover, our simulation results show that the head (nitrogen) groups are essentially tethered to the clay surface while the long hydrocarbon chains tend to adopt a layering structure with disordered conformation, which contrasts with the previous assumptions of either the chains lying parallel to the clay surface or being tilted at rather precise angles.

Journal Article↗
PubMed2005

Clay-based polymer nanocomposites: research and commercial development.

This paper reviews the recent research and development of clay-based polymer nanocomposites. Clay minerals, due to their unique layered structure, rich intercalation chemistry and availability at low cost, are promising nanoparticle reinforcements for polymers to manufacture low-cost, lightweight and high performance nanocomposites. We introduce briefly the structure, properties and surface modification of clay minerals, followed by the processing and characterization techniques of polymer nanocomposites. The enhanced and novel properties of such nanocomposites are then discussed, including mechanical, thermal, barrier, electrical conductivity, biodegradability among others. In addition, their available commercial and potential applications in automotive, packaging, coating and pigment, electrical materials, and in particular biomedical fields are highlighted. Finally, the challenges for the future are discussed in terms of processing, characterization and the mechanisms governing the behaviour of these advanced materials.

Aluminum Silicates↗
PubMed2001

Carbohydrate-loading during the follicular phase of the menstrual cycle: effects on muscle glycogen and exercise performance.

The effects of employing a high-carbohydrate diet (carbohydrate-loading) to increase glycogen storage in skeletal muscle are not well established in female athletes. On 4 occasions--2 familiarization trials and 2 experimental trials--6 well-trained female subjects completed 6 x 15-min continuous intervals of cycling (12 min at 72% VO2max, 1 min at maximal effort, and 2 min at 50% VO2max), followed by a time trial 15 min later. The women consumed their habitual diets (HD; 6-7 g carbohydrate/kg lean body mass) for 3 days after the second familiarization trial and before the first experimental trial. During the 3 days following the first experimental trial, the subjects consumed a high-carbohydrate diet (CD; 9-10 g carbohydrate/kg lean body mass) prior to the second experimental trial. Mean (+/-SEM) pre-exercise muscle glycogen concentrations were greater after CD versus HD (171.9+/-8.7 vs. 131.4+/-10.3 mmol/kg wet weight, P < 0.003). Although 4 of the 6 subjects improved their time-trial performance after CD, mean performance for the time trial was not significantly different between diets (HD: 763.9+/-35.6 s; CD: 752.9+/-30.1 s). Thus, female cyclists can increase their muscle glycogen stores after a carbohydrate-loading diet during the follicular phase of the menstrual cycle, but we found no compelling evidence of a dietary effect on performance of a cycling time trial performed after 90 min of moderate-intensity exercise.

Bicycling↗
PubMed1982

Dissolution-controlled transport from dispersed matrixes.

A simplified mathematical model for dissolution-controlled transport from dispersed matrixes is presented. Analytical solutions have been obtained previously when solute diffusion totally controls the transport process. However, when solute dissolution offers the limiting resistance to mass transport, the solution reduces to a form where the mass released varies directly with time. Experimental release rates of a drug from a dispersed polymeric matrix into water were measured for a range of drug particle sizes in order to test the applicability of the proposed model; the agreement between theory and experimental is good.

Delayed-Action Preparations↗
PubMed1979

Hearing in military personnel.

Impaired hearing is an occupational hazard prevalent not only in industry but also in the armed forces. A survey to establish its prevalence in the SAF land forces was conducted. A sample of 2,564 subjects obtained through multistage proportional sampling was studied of whom 1,521 "normal" subjects were finally analysed. 403 subjects i.e. 26.5%, showed evidence of impaired hearing. The highest incidence was in the Artillery. The frequency most commonly affected was 6,000 Hz and the commonest presenting symptom was tinnitus. A Hearing Conservation Programme is described. Comparisons with the situations in Singapore's industries are made.

Ear Protective Devices↗
PubMed1976

Cardiovascular and respiratory changes in response to change of posture in the very obese.

Circulatory and respiratory effects of change of posture from sitting to supine were studied in 11 obese patients scheduled for gastric bypass operations. Patients were studied on the morning of operation before any medication was given. Average weight was 138.8 kg, 108.6 per cent above ideal weight. Change of posture from sitting to supine was associated with 11 per cent increase in oxygen consumption (VO2), 35.5 per cent increase in cardiac output (CO), 35.8 per cent increase in cardiac index, 17.85 per cent decrease in arteriovenous oxygen difference, 31 per cent increase in mean pulmonary arterial pressure, 44 per cent increase in pulmonary-artery wedge pressure, 21.5 per cent decrease in peripheral resistance (PR), 6 per cent decrease in heart rate, and 17.7 per cent increase in venous admixture (QS/Qt). All these changes were significant. There was no change in mean arterial pressure, alveolo-arterial O2 difference and respiratory rate. The increase in CO was attributed to reduction in PR and to increased V02 probably due to increased work of breathing.

Adult↗