Biomedical subjects

R Merritt

Publications and source records attributed to R Merritt.

10 recordsLinked to original sources

PubMed2005

Impact of membrane solid-liquid separation on design of biological nutrient removal activated sludge systems.

Installing membranes for solid-liquid separation into biological nutrient removal (BNR) activated sludge (AS) systems makes a profound difference not only in the design of the BNR system itself, but also in the design approach for the whole wastewater treatment plant (WWTP). In multizone BNR systems with membranes in the aerobic reactor and fixed volumes for the anaerobic, anoxic, and aerobic zones (i.e., fixed volume fractions), the mass fractions can be controlled (within a range) with the interreactor recycle ratios. This zone mass fraction flexibility is a significant advantage in membrane BNR systems over conventional BNR systems with SSTs, because it allows for changing of the mass fractions to optimize biological N and P removal in conformity with influent wastewater characteristics and the effluent N and P concentrations required. For PWWF/ADWF ratios in the upper range (f(q) approximately 2.0), aerobic mass fractions in the lower range (f(maer) < 0.60), and high (usually raw) wastewater strengths, the indicated mode of operation of MBR BNR systems is as extended aeration WWTPs. Although the volume reduction compared with equivalent conventional BNR systems with secondary settling tanks is not as large (40% to 60%), the cost of the membranes can be offset against sludge thickening and stabilization costs. Moving from a flow-unbalanced raw wastewater system to a flow-balanced (f(q) = 1), low (usually settled) wastewater strength system can double the ADWF capacity of the biological reactor, but the design approach of the WWTP changes from extended aeration to include primary sludge stabilization. The cost of primary sludge treatment then has to be paid from the savings from the increased WWTP capacity.

Aerobiosis↗

PubMed2001

Multiple lifestyle and psychosocial risks and delivery of small for gestational age infants.

OBJECTIVE: To examine the occurrence of multiple risk behaviors during pregnancy among women who delivered a live birth and to examine the risk of delivering small for gestational age (SGA) infants for women with multiple risks. METHODS: We used data from the Pregnancy Risk Assessment Monitoring System to conduct the research. Pregnancy Risk Assessment System is a population-based, mixed-mode surveillance system that collects information on maternal behaviors and experiences. We used data for 1997 from 13 (n = 19,331) states that had response rates of over 70%. We considered ten self-reported individual risk behaviors or exposures (eg, smoking, unintended pregnancy) and several demographic variables. The main outcome was SGA. RESULTS: Pregnant women engage in or are exposed to multiple risks and often these risks are inter-related. The occurrence of multiple risks appears to be associated with an increased likelihood of delivering an SGA infant. Compared with women with no reported risks or exposures, the adjusted odds ratios for delivering an SGA infant were as follows: 1.29 (95% confidence interval [CI] 0.69, 2.43) for one, 1.86 (95% CI 1.00, 3.44) for two, 1.67 (95% CI 0.90, 3.10) for three, 2.06 (95% CI 1.10, 3.89) for four, 3.53 (95% CI 1.71, 7.30) for five, and 3.82 (95% CI 1.97, 7.41) for six or more risks or exposures. CONCLUSION: A large proportion of pregnant women engage in or are exposed to multiple risks. Women with a larger number of risks are at greater risk for delivering an SGA infant than women with fewer or no risks.

Adolescent↗

PubMed1997

Moderate alcohol feeding attenuates postinjury vascular cell proliferation in rabbit angioplasty model.

Our studies in the cholesterol-fed rabbit model indicate that moderate alcohol consumption reduces the risk of restenosis by preventing low-density lipoprotein (LDL) oxidation. Eighteen hypercholesterolemic rabbits underwent arterial injury by Fogerty balloon endothelial denudation of iliac arteries. Two weeks later, balloon angioplasty of atherogenic or atherosclerotic arterial segments was performed. Nine rabbits (control) received water ad lib, whereas nine rabbits (moderate alcohol treated) received an average of 2.5 ml alcohol per 500 ml water daily, from the day of feeding hypercholesterolemic diet until they were killed, 10 weeks later. There was a 26% increase in lumen size of the moderate alcohol-treated group compared with the control group. The percentage neointima formation (NI) values of the moderate alcohol-treated and control groups were 77 +/- 2.1 and 61 +/- 1.9, respectively (p < 0.001). The lumen/neointima (L/NI) ratio of the moderate alcohol-treated group was 0.71 +/- 0.07 compared with the control group, 0.33 +/- 0.04 (p < 0.001). The number of foam cells in the moderate alcohol-treated group was threefold less than the control group [i.e., 1.4 +/- 0.4 and 3.9 +/- 0.8, respectively (p = 0.005)]. The arterial lesion malondialdehyde (MDA) values of the control and the moderate alcohol-treated groups were 13.6 +/- 2.8 and 4.4 +/- 0.5 (p = 0.004), respectively. By radioimmunoassay, the moderate alcohol-treated group had less macrophage chemotactic protein-1 (MCP-1; 3,277 cpm/microg protein) and platelet-derived growth factor (PDGF; 2,261 cpm/microg protein) compared with the controls (MCP-1, 4,529 cpm/microg protein; PDGF, 3,583 cpm/microg protein). Thus we conclude that low concentrations of alcohol reduce neointimal formation, and the extent of lipid oxidation, the number of foam cells in the neointimal area and may decrease the expression of MCP-1 and PDGF by reducing LDL oxidation in an animal model of postangioplasty restenosis.

Angioplasty, Balloon↗

PubMed1992