PubMed · 13958441
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V F KATSITADZE. 1963. [Membrane filter].. https://pubmed.ncbi.nlm.nih.gov/13958441/
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Using projection geometry, algebraic formulas, and different beam indicating devices (BIDs), the surface area and volume of tissue exposed for a hypothetical patient was determined. Combinations of 4 BID lengths and shapes were used: 4-inch (10.2 cm.) pointed plastic, 8-inch (20.3 cm.) round plastic, 14-inch (35.6 cm.) round aluminum, and 14-inch (35.6 cm.) rectangular aluminum. As each subject BID was progressively lengthened and collimated, the area and volume of tissue exposed was reduced. The calculated area and volume of exposed tissue for the 14-inch rectangular aluminum open-ended lead-lined BID was 16.6 cm.2 and 327.7 cm.3, respectively. This represented 9% of the area and 8% of the volume of tissue exposed using the 4-inch round pointed plastic BID or a 91% (area) and 92% (volume) reduction in patient exposure.
Detection of the foodborne pathogen Listeria monocytogenes requires that food samples be processed to remove proteins and lipids, concentrate microorganisms to a detectable concentration, and recover the concentrated cells in a small volume compatible with micron-scale biochips. Mechanistic considerations addressed in this research include the roles of membrane structure, pore size, and detergents in maximizing recovery of cells from a complex biological fluid. The fluid in this case was a food sample (hotdog extract) inoculated with L. monocytogenes. This study showed how membrane filtration using a syringe filter is able to concentrate L. monocytogenes by 95x with up to 95% recovery of living microorganisms by concentrating 50 mL of food sample into a volume of 500 microL. Tween 20 was added to the sample to prevent irreversible adsorption of the microorganism to the membrane and thereby help to ensure high recovery. Comparison of polycarbonate, mixed cellulose, nylon, and PVDF membranes with 0.2 to 0.45 microm pores showed the 0.2 microm polycarbonate membrane with straight through, mono-radial pores gives the highest recovery of living microorganisms. The mixed cellulose, nylon, and PVDF membranes have a fibrous structure whose characteristic openings are much larger than their effective pore size cut-offs of 0.22 or 0.45 microm. We define conditions for rapid membrane-based cell concentration and recovery that has the potential to supplant enrichment steps that require a day or more. This approach has the added benefit of facilitating examination of a large amount of fluid volume by reducing its volume to a range that is compatible with the microliter scales of biochip or other biosensor detection systems.
UNLABELLED: Reactive oxygenated species (ROS) not only exist in living organisms, they also exist in our environment. Combustion process and photochemical reactions are the major source of environmental ROS, and combustion process produced ROS has been gradually gaining attention in recent years. The purpose of this study is to determine the concentrations of ROS in the mainstream smoke of cigarettes sold in the marketplace using the DCFH2 fluorescence method and to understand particulate and gaseous concentrations of ROS. This research will also discuss the relationship between ROS and nicotine, found in popular cigarette brands, as well as the effectiveness of cigarette filters to remove ROS. Results indicate that the ROS concentration of mainstream smoke is 18.64-54.81 nmol H2O2/l while the correlation coefficients of nicotine and tar to total ROS are 0.959 and 0.909, respectively. Gaseous ROS concentrations are 14.32-39.03 nmol H2O2/l, and make up 71.21-85.99% of the total. It can be clearly seen therefore, that ROS exist mainly in the gaseous phase. Particulate ROS is dominant at PM2.5 (ROS(TSP)/ROS(PM2.5) is 0.652-0.959). The experimental results involving the tobacco leaves and cigarette ash show that ROS in mainstream smoke comes from the combustion process and not from the tobacco leaves. There is no effective means of eliminating ROS from mainstream smoke, regardless of whether a cigarette filter contains active charcoal. PRACTICAL IMPLICATIONS: This study showed that cigarette combustion will produce high concentration of ROS, and this high concentration of ROS in mainstream cigarette smoke probably is one major factor contributing to a high incidence of lung cancer in smokers. Environmental tobacco smoke (ETS) or second-hand smoke is a major indoor air pollutant that could potentially harm non-smokers. We will try to determine the ROS in ETS in the future.