Clogging Rate Research Articles

The effect of ovarian steroids on sickle cell deformability.

Sickle cell disease (SCD) is an incurable debilitating disease affecting the Afro-Caribbean population. The combined oral contraceptive pill (COCP), an effective and popular method of contraception, is often denied to women with SCD for fear that the disease process may have a synergistic effect on the coagulation changes associated with contraceptive steroids. In this study red cell deformability was assessed in 10 women with SCD and 10 comparable women with normal AA haemoglobin. Neither group was on exogenous hormones. The red cells were taken in the follicular phase of the menstrual cycle when women have low endogenous levels of oestradiol and progesterone. The effect of the steroids contained in the COCP on red blood cells was simulated by incubation with therapeutic concentrations of oestradiol and progesterone. Red cell deformability is a measure of the ease with which erythrocytes flow through small capillaries and was assessed using the parameters red cell transit time (RCTT) and clogging rate (CR). Therapeutic concentrations of oestradiol and progesterone did not appear to influence red cell deformability in women with SCD or normal AA haemoglobin.

Leukocyte flow properties, polymorphonuclear membrane fluidity, and cytosolic Ca2+ content in subjects with vascular atherosclerotic disease with and without noninsulin-dependent diabetes mellitus.

The aim of this research was the evaluation of white blood cell (WBC) filtration, reflecting WBC flow properties, polymorphonuclear cell membrane fluidity, and cytosolic Ca2+ content in subjects with vascular atherosclerotic disease (VAD) and in VAD subjects with noninsulin-dependent diabetes mellitus (NIDDM), in good hemodynamic balance. The authors examined WBC filtration (unfractionated, mononuclear [MN], polymorphonuclear [PMN] cells), using the St. George Filtrometer and considering, respectively, the initial relative flow rate (IRFR) and the clogging rate (CR); the PMN membrane fluidity, employing the fluorescent probe TMA-DPH and calculating the fluorescence polarization degree; and the PMN cytosolic Ca2+ content, adopting the fluorescent probe Fura 2-AM and considering the ratio between the Fura 2-Ca2+ complex and the unchelated Fura 2 fluorescence intensity. The obtained data showed that only the filtration parameters (IRFR, CR) of unfractionated WBCs discriminated normal subjects from VAD groups, whereas the filtration parameters of MN and PMN cells did not demonstrate any distinction. PMN membrane fluidity did not distinguish normal subjects from VAD groups, whereas PMN cytosolic Ca2+ content was significantly increased in VAD groups in comparison with normal subjects. No relationship was evident between WBC filtration and plasma metabolic parameters; the correlations obtained between PMN filtration and other PMN parameters need further investigation.

Effects of Orifice Size on Microsprinkler Clogging Rates

The clogging rates of microsprinkler emitters with orifice diameters of 0.76 mm (0.03 in., black base), 1.02 mm (0.04 in., blue base), 1.27 mm (0.05 in., green base), and 1.52 mm (0.06 in., red base) were evaluated in a citrus grove over a three-year period. The experiment used a randomized complete block design with eight emitters per plot and five replications of each treatment. The irrigation water was drawn from a pond, treated with one of two water conditioners, and filtered through a sand media filter. Every three months, each emitter was inspected and those that were clogged were examined to determine the cause of clogging. All fouled emitters were thoroughly cleaned and/or replaced. Overall, 46% of the clogging was due to algae, 34% was from ants and spiders, 16% was from snails, and 4% was from physical particles such as sand and bits of PVC. About 20% of the black base emitters required cleaning or replacement during each quarter compared to about 14% of the blue base, 7% of the green base, and 5% of the red base emitters. The total clogging rate was found to be inversely related to the orifice area of the emitters during the three-year study.

The effect of prolonged perfusion with a membrane oxygenator (PPMO) on white blood cells

Preserving the rheological properties of whole blood cells is vital for their smooth passage in the capillaries without causing blockage and disturbances in the microcirculation. To evaluate the effect of mechanical trauma on the rheology of white blood cells during prolonged perfusion with membrane oxygenation (PPMO), 16 in vitro experiments were conducted for 72 hours. The St George Carrimed Filtrometer was used to estimate the plasma white cell filtration rates (P-WFR). Also an in vitro estimation of the ability of individual cells to pass through capillaries, the white blood cell clogging rate (WBC-CR), the number of clogging particles (WBC-CP), the total white blood cell count (T-WBC) and two in vitro estimations to assess the effect of aggregates and stiff cells in blocking the microcirculation were performed. The traumatized white cells reduced their mean P-WFR by 37% +/- 9, 72% +/- 2 and 76% +/- 2 at 24, 48 and 72 hours respectively (p < 0.001). The mean WBC-CR was increased to 15.2 +/- 1.5, 32.6 +/- 2.2 and 40.3 +/- 8.3 x 10(2)%/ml at 24, 48 and 72 hours respectively (p < 0.001). The mean WBC-CP was increased to 6.6 +/- 1.5, 9.7 +/- 1.2 and 13.9 +/- 2.1 x 10(6)/ml at 24 hours (p < 0.05), 48 and 72 hours respectively (p < 0.001). The T-WBC was decreased to 55% +/- 0.3, 23% +/- 0.2 and 14% +/- 0.1 and 14% +/- 0.1 at 24, 48 and 72 hours respectively (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of low concentrations of assimilable organic carbon (AOC) in water on biological clogging of sand beds

Infiltration of pretreated surface water with recharge wells is hampered by biological clogging processes in the aquifer. The influence of the concentration of easily assimilable organic carbon (AOC) in water on clogging was investigated in filter beds operated under well-defined laboratory conditions using acetate as a model substrate. Acetate concentrations in the water as low as 0.01 mg C/l promoted clogging with the main head loss, caused by bacterial growth, in the first centimeter of the sand bed. An empirical model was developed describing a linear relationship between the operation period to reach a certain increase in head loss ( T Pi ) and the reciprocal value of the acetate concentration or acetate load [ L ac g C/ (m 2 · d)] at a constant filtration rate. The rate of clogging, designated as the microbiological clogging factor ( C r), is defined by the slope of the linear relationship between the square root of the increase of the head loss ( P 1 1 2 ) and the operation time. This linear relationship demonstrated that the increase in clogging rate was constant with time. Observations at several locations with experimental recharge wells revealed that the AOC concentration is an important parameter for the biological clogging potential of water. The AOC concentration of water used for infiltration in a recharge well should be less than 0.01 mg acetate-C equiv/l to prevent biological clogging for a period of more than a year.

Mesh-size effects on drift sample composition as determined with a triple net sampler

Nested nets of three different mesh apertures were used to study mesh-size effects on drift collected in a small mountain stream. The innermost, middle, and outermost nets had, respectively, 425 µm, 209 µm and 106 µm openings, a design that reduced clogging while partitioning collections into three size groups. The open area of mesh in each net, from largest to smallest mesh opening, was 3.7, 5.7 and 8.0 times the area of the net mouth. Volumes of filtered water were determined with a flowmeter. The results are expressed as (1) drift retained by each net, (2) drift that would have been collected by a single net of given mesh size, and (3) the percentage of total drift (the sum of the catches from all three nets) that passed through the 425 µm and 209 µm nets. During a two day period in August 1986, Chironomidae larvae were dominant numerically in all 209 µm and 106 µm samples and midday 425 µm samples. Large drifters (Ephemerellidae) occurred only in 425 µm or 209 µm nets, but the general pattern was an increase in abundance and number of taxa with decreasing mesh size. Relatively more individuals occurred in the larger mesh nets at night than during the day. The two larger mesh sizes retained 70% of the total sediment/detritus in the drift collections, and this decreased the rate of clogging of the 106 µm net. If an objective of a sampling program is to compare drift density or drift rate between areas or sampling dates, the same mesh size should be used for all sample collection and processing. The mesh aperture used for drift collection should retain all species and life stages of significance in a study. The nested net design enables an investigator to test the adequacy of drift samples.

Effects of metformin on haemorheology, lipid parameters and insulin resistance in insulin-dependent diabetic patients (IDDM)

We have evaluated the effect of metformin on haemorheology, lipid levels and insulin resistance in insulin-dependent diabetic patients over a 6-week period. Rheological parameters remained unaltered except for the whole blood clogging rate which decreased significantly. No effect on lipid levels was seen. The main effect of metformin was limited to daily insulin requirement and insulin units kg bw. Bearing in mind the negative effects of high insulin levels, metformin could be useful in the prevention of atherogenesis in insulin-dependent diabetic patients.

Single cell assay with an automated capillary microinjection system

An automated capillary microinjection system with computer controlled positioning of the cells and of the capillary, and its applications and advantages arc described. About 1500 injections are possible in one hour, with high reproducibility. In cytoplasmic and nuclear injections more than 90% and 85% of the cells are successfully injected. Using FITC-Dextran at a concentration of 0.5% as a fluorescently labelled coinjection marker, 99% of the cells can be retrieved in cultrue medium even 48 hours after unjection. The coordinates of the cells are stored in the computer and accuracy in statistical evaluation of experiments is improved in coparison to the manual techniques. Methods for preparatin and handling of glass capillaries were developed resulting in reproducible form and significantly reduced clogging rate. The improved characteristics offered by this system are demonstrated in studies leading to the confirmation of existence of mRNA(s) inhibiting cell proliferation. Functional screening by cell injections of cDNA libraries and of size fractionated mRNA molecules can be performed efficiently with the automated microinjection system.

Self-expanding biliary stents: preliminary clinical experience.

Nine self-expanding metallic stents were implanted in 7 patients to relieve biliary obstruction. One patient had a benign stricture and 6 patients had malignant stenoses. The stent was inserted percutaneously on a 7 F delivery catheter in 6 patients. Endoscopic transpapillary implantation was performed in one patient. After release the stent expanded to a diameter of 8-10 mm. The correct position was checked by fluoroscopy and cholangiography. In addition, percutaneous cholangioscopy was carried out in 6 patients. No complications were observed within 30 days. Clinical improvement was seen in all patients. After a mean follow-up period of 11 weeks (range: 3-17) 6 of the 7 patients are still alive with no evidence of biliary reobstruction. One patient died of disseminated malignancy. The initial results are promising. The wide-bore diameter, the macroporous configuration and the small surface area of the implanted self-expanding stents would seem to be associated with lower rates of infection, clogging and migration as compared with conventional endoprostheses. Further trials are warranted to determine the future role of self-expanding stents in biliary obstruction.

Large bore percutaneous endoscopic gastrostomy using the Russell technique

In 1984 Russell et aU introduced a new and simpli­ fied technique of percutaneous endoscopic gastros­ tomy insertion that required only a single passage of the gastroscope compared with the technique of Gau­ derer et a1. 2 Although this technique is easy to perform, well tolerated by patients, and accompanied by a low complication rate, we found, at our institution, that the 16 F Russell introducer allowing placement of a 14 F Foley catheter with its small inside diameter was accompanied by an unacceptably high rate of tube clogging. Clogging was seen even when canned nutri­ tional supplements were used and was especially com­ mon when crushed pill fragments were administered. We now report our experience using the Russell tech­ nique and a 20 F introducer sheath allowing the place­ ment of an 18 F Foley catheter.

Effect of Feeding Tube Properties and Three Irrigants on Clogging Rates N. METHENY, P. EISENBERG, AND M. MCSWEE‐NEY Department of Medical‐Surgical Nursing, School of Nursing, St. Louis University, Jewish Hospital of St. Louis, St. Louis, Missouri, East Carolina University, Greenville, North Carolina

Effect of Feeding Tube Properties and Three Irrigants on Clogging Rates N. METHENY, P. EISENBERG, AND M. MCSWEE‐NEY Department of Medical‐Surgical Nursing, School of Nursing, St. Louis University, Jewish Hospital of St. Louis, St. Louis, Missouri, East Carolina University, Greenville, North Carolina

Single cell assay with an automated capillary microinjection system

An automated capillary microinjection system with computer-controlled positioning of the cells and of the capillary, and its applications and advantages, is described. The system is easy in handling and manipulation. About 1500 injections are possible in 1 h, with high reproducibility. In cytoplasmic and nuclear injections more than 90 and 85 % of the cells are successfully injected. Using FITC-dextran at a concentration of 0.5 % as a fluorescently labeled coinjection marker, 99 % of the cells can be retrieved in culture medium even 48 h after injection. The coordinates of the cells are stored in the computer and accuracy in statistical evaluation of experiments is improved in comparison to the manual techniques. Methods for preparation and handling of glass capillaries were developed resulting in reproducible form and significantly reduced clogging rate. The improved characteristics offered by this system are demonstrated in studies leading to the confirmation of existence of an mRNA inhibiting DNA synthesis in cells. Functional screening by cell injections of cDNA libraries and of size-fractionated mRNA molecules can be performed efficiently with the automated microinjection system.

Stability of residual fuel oils.

A developmental study was carried out on residual oil stability evaluation methods that most closely predict actual performance of the oils. A newly developed spot test which is based on the ASTM spot test and modified for wider applications is a simpler evaluation method. Fairly good correlations were found between the more widely known evaluation methods and the spot test. In regard to performance tests, a purifier test and a filter test were carried out using laboratory apparatus that simulated actual field practices, and the spot rating of the new spot test correlated with both the amount of sludge removed by the purifier and the strainer clogging rate. The stability of fuels during storage was remarkably influenced by a scale effect in laboratory tank storage tests. When residues and cuttei stocks were blended to make residual fuel oils, the stability of fuels during storage could be guaranteed by selecting optimum combinations of residue and cutter stock properties.

Pressure Distribution Design for Septic Tank Systems

Pressure distribution of septic tank effluent in subsurface soil absorption systems is gaining in popularity. This method of effluent distribution has the advantage over other methods of providing dosing in addition to more uniform distribution which reduces the rate of soil clogging and prevents localized overloading. However, the application of these networks has been limited because of the complexity of their design. To overcome this difficulty, the design criteria are discussed and a simplified design procedure presented.

Colmatage naturel d'un milieu filtrant par les particules en suspension dans l'eau

This paper contains a general study on the natural clogging of porous media by suspended sediment in water. This creates with time a decrease in the permeability coefficient and consequently a reduction of the seepage flow.Two theories are presented and compared for the prediction of the rate of clogging in nature. The two approaches have been verified by experimental data obtained from tests carried out at Laval University. Results have permitted the limits of application of each method to be denned.

Clogging Rate of Screens as Affected by Particle Size

ABSTRACT A general expression has been formulated for assess-ing the screening duration effect on particle en-trapment in the perforations. This expression contains both clogging and passage rate factors, defined for each size fraction of the material to be screened. A sim-plified version of the expression, based solely on clog-ging rate factors, can be used for determining the trap-ping of oversize particles, as they cannot pass through the screen perforations. Methods for determining the clogging rate factors for oversize and undersize parti-cles are detailed. The effect of particle size on the clogging rate is investigated. The validity of the expres-sions has been confirmed by experiments conducted with seeds.

Pore Gas Composition Under Sewage Spreading

AbstractSeptic tank effluent was applied to sand in laboratory lysimeters. Dosing frequencies of 2/day and 6/day were used to observe relationships between changes in the composition of the pore gas and the clogging of the sand. The rate of clogging in the 2/day unit was less than that in the 6/day unit. This reduced rate of clogging was related to pore‐gas and moisture content changes which occurred in the sewage dosing and drainage cycles. The longer cycle of the 2/day frequency provided more oxygen over a greater percentage of the total elapsed time. In the 6/day lysimeter the rapid soil clogging, which is characteristic for anaerobic conditions, started while the oxygen concentration in the pore gas was greater than 13 percent. Water‐filled pores or water films, occurring as the result of an increase in the moisture content, may have provided anaerobic sites in the presence of the high pore‐gas oxygen. Carbon dioxide inhibition of microbial growth did not cause the rapid phase of clogging. Moisture or oxygen determinations may be suitable guides for prevention of the rapid phase of soil clogging.

Tundish nozzle blockage in continuous casting

Examination of the phenomenon of nozzle blockage, encountered during casting of aluminum-killed steel, resulted in the following conclusions: 1. The mechanism of clogging is a complex process involving the precipitation of alumina in the bore of the nozzle augmented by dendritic growth of entrapped steel. 2. At low aluminum concentrations (<0.01% Al soluble), the alumina branches were found to be embedded in a matrix of MnAlSi-oxides, while at higher concentrations (≥0.01% Al soluble) the matrix tended to disappear with the clog consisting only of alumina and frozen steel. 3. Although the tendency for build-up to occur was found even at low aluminum concentrations, complete blockage of the nozzle was encountered only at concentrations ≥ 0.008% Al soluble. 4. While reducing reoxidation of the steel in the tundish through complete shielding decreased the rate of clogging, it did not completely eliminate the problem. 5. A new nozzle design with improved heat transfer characteristics eliminated blockage under strictly controlled operation. However, the stringent requirements for high tundish preheat ≥ 2450 °F) and a minimum steel temperature of 2800 °F, together with the unresolved problem of canting of the stream, are believed to impose serious limitations under actual plant conditions. 6. The concept of a variable orifice for casting achieved by an oversized nozzle with stopper rod control represents a solution to the problem of nozzle blockage. However, application of this technique to the casting of high quality billets depends on the significance of the following: (a) the practicability of a shrouded tundish stream; (b) development of a control system to prevent large variations in casting rate: and (c) the effect of agglomerated alumina, washed out of the nozzle, on product quality.