Total Count Method Research Articles

Distribution of heterotrophic bacteria in relation to the concentration of particulate organic matter in seawater

The relationship between the number of bacteria and the concentration of particulate organic carbon (POC) in seawater was investigated. In coastal seawater in summer, the POC concentration showed better correlation to the density of bacteria obtained by the viable plate count method (viable count, V.C.) than by the total direct count method (total count, T.C.). The number of attached bacteria (A) showed significant fluctuation, both laterally on a geographical scale and vertically in the water column; on the other hand, the number of free-living bacteria (F) was relatively constant. The POC concentration had a much higher correlation with A (r = 0.8795) than with T.C. (r = 0.7339), and had a low correlation with F (r = 0.6935). Moreover, a very good correlation was observed between the density of bacteria obtained by V.C. and A (r = 0.9153). These results indicate that when the concentration of particulate organic matter (POM) increases, some free-living bacteria become attached to POM, and grow on the surface of POM. These communities of attached bacteria have the ability to make colonies on plate media and can be counted as the "viable plate count."

Pulsed Neutron Measurement of Single and Two-Phase Liquid Flow

Use of radioactive tracers for flow velocity measurements is well developed and documented. Measurement techniques involving pulsed sources of fast (14 MeV) neutrons for in-situ production of tracers can be considered as extensions of the old methods. Improvements offered by these Pulsed Neutron Activation (PNA) techniques over conventional radioisotope techniques are (1) non-intrusion into the system, (2) easier introduction and better mixing of the tracer, and (3) no requirement to handle large amounts of relatively long lived radioactive materials. Just as in conventional tracer techniques, flow velocity measurements by PNA methods can be based on the transit-time or the total-count method. A very significant difference of the PNA technique from conventional methods is that the induced activity is proportional to the density of the fluid, and that PNA techniques can be used for density measurements (of two-phase flows) in addition to flow velocity measurement. Original equations were derived that relate experimental data to the mass flow velocity and the average density. The accuracy of these equations is not effected by the flow regime. Experimental results are presented for tests performed on liquid sodium loops, on air-water loops, on the EBR-II reactor and on the LOFT reactor. Current instrumentation development programs (detectors, pulsed neutron sources) are discussed.

Krypton-85. A versatile tracer for industrial process applications

85Kr is a convenient gas tracer for industrial process use, particularly for flow rates and leak testing. Extension of these uses is described here. The flow rate of pure hydrogen sulfide gas from a petroleum refinery to a chemical plant was measured by the total count method. The small sample stream of H 2S, after passing through the counting apparatus, was totally absorbed in caustic thereby avoiding any release to the atmosphere. A leak test made to decide between a heat exchanger leak and catalyst deterioration absolved both possible causes, when interpretation of the tracer discharge curve indicated that the problem rested in the catalytic reactor. Shutdown and inspection of the reactor revealed an opening which permitted internal bypassing of gas. A heat exchanger leak was found in which the gas tracer was used even though only liquid flowed on the sample side. This technique works where a carrier gas strips dissolved 85Kr from the liquid for gas counting.

Ragweed pollen generation and sampling methods for filtration studies.

The means of generating and measuring the concentration of ragweed pollen particles for air filtration studies is discussed. The development of an inexpensive in-line impaction type sampler which collects the sample on filter paper is described. The advantages of the total particle count method when using this sampler are also defined. The effect of sampling an air steam without using an isokinetic probe was investigated; a non isokinetic sampling train was found to give results with accuracy comparable to isokinetic data. Another part of the study was to examine the "shadowing" effect of one sampling probe. Means are given for adjusting data for this effect.

Structure-Activity Relationships of Tetracyclines I: Inhibition of Cell Division and Protein and Nucleic Acid Syntheses in Escherichia coli W

The kinetics of inhibition of Escherichia coli in a peptone broth as a function of the concentration of 18 tetracyclines were determined. Viable and total cell count methods were used to measure rates of cell division. Rates of protein and nucleic acid syntheses were determined simultaneously by a membrane filter technique in conjunction with the Folin-Lowry assay and the orcinol reaction, respectively. The relationship of these rate constants to antibiotic concentration is an accurate estimate of activity under the test conditions. Different times before onset of inhibition of protein synthesis, cell division, and nucleic; acid synthesis are observed in kinetic experiments. These differences are interpreted as being consistent with theories of primary inhibition of protein-synthesizing systems.

Total Body Counting in the Assessment of Vitamin B12: Absorption in Patients with Pernicious Anemia, Achlorhydria Without Pernicious Anemia and in Acid Secretors

Abstract The absorption of 58Co-vitamin B12 was assessed by the method of total body counting in 25 patients with frank P.A., five with latent P.A., 47 with achlorhydria but without malabsorption of vitamin B12 and 47 acid-secreting patients. A total of 192 tests was done. With or without prior stimulation of intrinsic factor secretion by pentagastrin the upper level of absorption of vitamin B12 in patients with frank or latent P.A. was 25 per cent. Taking an equivocal result to be 21-25 per cent inclusive, the total body counting method was able to distinguish P.A. patients from those with achlorhydria without P.A. with 87 per cent accuracy and one per cent error and from non-P.A. achlorhydric patients and acid secretors combined with 91 per cent accuracy and 0.5 per cent error. Pentagastrin stimulation did not improve the separation between achlorhydric patients with and without P.A. but raised the lower limit of retention of vitamin B12 from 24 to 44 per cent in the acid secreting patients. The method of total body counting is recommended as a method of assessing vitamin B12 absorption.

Point dilution methods of investigating ground water flow by means of radioisotopes

To apply the point‐dilution method of measuring the rate of ground water flow by tracers, the distortion of the flow field by the well must be known. The distortion can be calculated with sufficient accuracy if the permeabilities of the aquifer, k3, of the gravel pack, k2, and of the well screen, k1, fulfill the condition k3 ≤ k2 ≤ k1. The tracer must be adequately mixed during the dilution procedure. Experiences obtained from model tests are applied in investigations in the field. By using peak‐to‐peak and total count methods in wells where vertical flow occurred, we could determine the depths and the rates of inflow and outflow, which relate to seepage under dams and water exploration. To determine the direction of ground water flow, a radio tracer was injected into a well‐screen section and, after having left the well‐screen, was detected by a collimated detector. The use of tracers that are fixed on the soil is advisable; 198Au, having been homogeneously distributed within the dilution volume initially, has proved most suitable. Strong vertical currents in the well represent a serious obstacle in field measurements of the rate and of the direction of ground water flow.

Flow rate measurements of condensable gases by the carrier-gas method

The flow of a condensable gas, such as steam, can be measured with noncondensable krypton-85 tracer by a modification of the total-count method. A noncondensable carrier gas is added to a sample stream just ahead of a condenser which removes the condensable gas. The carrier gas then carries the tracer through a counting chamber. From the known rate of flow of the carrier gas, the measured rate of collection of condensate and the total counts registered by a Geiger-Müller counter sensitive to krypton-85 beta rays, the condensable gas flow rate may be calculated. The method was successfully tested on high pressure steam flows.

Kinetics and Mechanisms of Action of Antibiotics on Microorganisms V: Chloramphenicol and Tetracycline Affected Escherichia coli Generation Rates

Total and viable count methods were used to study Eschericbia coli generation rates at various temperatures and tetracycline and chloramphenicol concentrations. The negative dependence of apparent first-order generation rate constants on concenrrations of these antibiotics was determined for all temperatures. The coincidence of the heat of activation for E. coli growth in antibiotic-free media and for the inhibitory rate constants was observed. The facile reversibility of antibiotic effects to predictable rates of E. coli generation in the subinhibitory concentration ranges of these antibiotics was demonstrated. A quantitative model consistent with the observed concentration dependencies and observed reversibilities is proposed which relates antibiotic partitioning from the media, a critical value for protein synthesis that results in microbial generation, and the present concept that these antibiotics compete for ribosomal binding sites and so inhibit the function of messenger RNA in protein synthesis.

Gas flow measurements by the total-count method

Simple equipment and procedures for storing, dispensing, injecting and counting krypton-85 are described for gas-flow measurements by the total-count method. A sample stream from the gas line being measured is passed through a counting chamber at atmospheric pressure, and the radioactivity is counted with a thin-walled β-ray tube. An example of a flow-rate and a leak-rate measurement in an industrial plant is given.

Dispersion and persistence of tracer in river flow measurements

The total-count method was demonstrated to be useful for accurate measurement of the flow in turbulent natural streams over a range of 5–1000 ft 3/sec. Duplicate measurements are reproducible to 1 per cent, and the absolute accuracy is within 5 per cent. The distance along the stream from where the tracer is added to where it is counted must be great enough to allow complete transverse mixing of the tracer. On the other hand, it should not be so great that longitudinal dispersion spreads the tracer over a time too long for convenient measurement. There is a considerable lattitude between these limits where the highest accuracy can be attained. Within these limits, gold-198 persists in the stream with losses too small to affect the accuracy. One man, unassisted, can measure the flow rate of a stream in one or two hours. The longitudinal dispersion of a tracer wave can be represented roughly by a Gaussian error function over a small segment of a stream. The mixing coefficient D varies with the dimensions and contour of the stream bed. Values from 80–270 ft 2/sec were found for adjacent segments of the same stream. A rough correlation of D with the size and velocity of the stream was found: D ≅ 2.5 (Qv) 1 2 . Based on this, a formula was derived for the distance required for complete transverse mixing in a turbulent stream: L min = aQ 1 3 . If L is expressed in feet and Q in ft 3/sec, the value of a is about 200 when the tracer is added at one edge, and about 50 when it is added in mid-stream. Дoкaзывaeтcя, xтo мeтoд пoлнoгo oтcxeтa пpимeним для тoxнoгo пзмepeния тexeния в тypбyлeнтныч ecтecтвeнныч пoтoкaч для жнaxeний пocлeднич, пpocтиpaющичcя oт 0,1 дo 30 м 3/ceк. Пoвтopныe измepeния мoгyт coвepшaтьcя c 1% oтклoнeниeм a aбcoлютнaя тoxиocть лeжнт в пpeдeлe 5%. Paccтoяниe вдoль пoтoкa, oт мecтa гдe paдиoaктивньй индикaтop клaдeтcя дo мecтa, гдe oн пoдcxитывaeтcя, дoлжнo быть дocтaтoxным, xтoбы oбecпexить пoлнoe пoпepexнoe пepeмeшивaниe paдиoaктивнoгo индикaтopa. C дpyгoй cтopoны, oнo нe дoлжнo выть нacтoлькo вeликo, xтo пpoдoльнaя диcпepcия pacпpocтpaнялa бы paдиoaктивньй индикaтop в тexeнии cлишкoм дoлгoгo вpeмeни для yдoвлeтвopитeльнoгo измepeния. Пpeдeлы, мeждy кoтopыми мoжнo дocтиxь нaивыcшeй тoxнocти, шиpoкo oтcтoят дpyг oт дpyгa. B этич пpeдeлaч, эoлoтo-198 ocтaeтcя в тoтoкe, a пoтepи cлишкoм нeзaxитeльны для тoгo, xтoбы пoвлиять нa тoxнocть. Oдин xeлoвeк, бeз вcякoй пocтopoннeй пoмoщи, мoжeт измepить cкopocтв тexeния peки зa oдин или дбa xaca. Пpoдoльнaя диcпepcия вoлны paдиoaктивнoгo индикaтopa мoжeт быть пpиблизитeльнo пpeдcтaвлeнa Гayccoвcкoй фyнкциeй пoгpeшнocти нa мaлый oбъeм тexeния. Кoэфициeнт пepeмeшивaния D мeняeтcя c paзмepaми и кoнтypoм pexнoгo днa. Для cмeжныч oбъeмoв тoгo жe пoтoкa нaйдeны знaxeния oт 7 дo 25 м 2/ceк. Уcтaнoвлeнa пpиблизитeльнaя кoppeляция для D в зaвиcимocти oт вeлиxины и cкopocти пoтoкa: D ⋟ 2.5 (Qv) 1 2 . Ha этoм ocнoвaнии былa выpaбoтaнa фopмaлa дopмлa дaющaя paccтoяниe нeoбчoдимoe для пoлнoгo пoпepexнoгo пepeмeшивaния в тypбyлeнтнoм пoтoкe: L min = aQ 1 3 . Ecли L выpaжaeтcя в м aQ в м 3/ceк., тo знaxeниe a вyдeт paвнятьcя пpиблизитeльнo 200 кoгдa paдиoaктивный индикaтop клдeтcя c oднoгo бopeгa, и пpиблизитeльнo 50, кoдa oн клaдeтcя c cepeдины пoтoкa.

The total-count technique: A new principle in flow measurement

This paper describes a new principle for measuring flow in all kinds of streams. A known quantity of radiotracer A is mixed in the following stream. A counter fixed in or near the stream, some distance downstream, registers a total of N counts from the tracer while it passes. The flow rate Q is given by the relation Q= AF N The constant factor F is determined by laboratory calibration of the counter. This simple formula is a completely general expression for the absolute flow rate of liquids and gases in any kind and size of conduit. It applies without modification over an extremely wide range. The total count above and below the junction of confluent streams measures the flow at each point. The total count in a divergent stream, no matter what fraction of the tracered stream it carries, depends only on the flow of the whole stream. These principles are applied to measure flow of water and oil in pipes in operating industrial plants. Also, water flow is measured in open channels and natural streams. Other applications of the total-count method are to the measurement of leaks in condensers and heat exchangers, and of entrainment in distillation columns.

Total-Count Technique in the Refinery

A new principle in measuring flow rates, called the total-count method, is based on measurement of the total number of counts from a radioactive tracer as it flows past a detector. (W. L.H.)

FACTORS AFFECTING THE PATHOGENICITY OF BACTERIA TO POTATO TUBERS. I

An isolate of Erwinia aroideae caused much more rotting of potato tubers than did isolates of Pseudomonas sp., Flavobacterium sp., and Pseudomonas syringae; filtrates from cultures of each of the bacteria in potato extract had about the same macerating activity. Pseudomonas sp. and P. syringae, but not Erwinia aroideae or Flavobacterium sp., were agglutinated in three different types of potato extract at the normal pH of potato tubers.Measurements of growth by turbidity and total count methods were compared. In undisturbed potato sap, Erwinia aroideae had grown much more after 12 hr. than had Flavobacterim sp. and Pseudomonas syringae. Erwinia aroideae also grew more rapidly than Pseudomonas sp., but in this case the difference was caused largely by a longer lag phase.The two species of Pseudomonas grew far less rapidly in potato sap cultures shaken hourly than in undisturbed cultures. Erwinia aroideae grew slightly more rapidly in disturbed culture. Measured by the total count method, growth of Flavobacterium sp. was better in undisturbed cultures, but the opposite result was obtained when growth was measured turbidimetrically.With a small inoculum, growth of Erwinia aroideae and of Pseudomonas sp. was delayed by as much as 3 days in potato sap sterilized by heat. This effect was not obtained with an inoculum twenty times bigger, with potato extract, or with sap sterilized by filtration.Potato sap reduced the macerating activity of preparations from each bacterium; oxidation of the sap had no further effect. Production of macerating enzymes by Flavobacterium sp. and Pseudomonas syringae, but not by Erwinia aroideae and Pseudomonas sp., was less in potato sap than in potato extract. Erwinia aroideae secreted macerating enzymes into potato sap much more rapidly during the first 12 hr. of growth than did Pseudomonas sp.The activities of filtrates from cultures of Erwinia aroideae and Pseudomonas sp. were higher at the pH of the culture at the time of sampling than at higher and lower values.The addition of CaCO3 to media apparently increased the pH optimum for macerating activity of Erwinia aroideae and, to a lesser extent, Pseudomonas sp. preparations.There was little difference in the toxicity of preparations of similar macerating activity from cultures of the four organisms.

EVALUATION OF METHODS OF ESTIMATING POPULATIONS OF THE SHEEP KED, MELOPHAGUS OVINUS (L.) (DIPTERA: HIPPOBOSCIDAE), ON MATURE EWES AND YOUNG LAMBS

Six methods of estimating populations of the sheep ked, Melophagus ovinus (L.), on mature ewes and young lambs of four breeds were evaluated. The actual populations were determined by picking off and counting all the keds. The total live count method gave the highest degree of accuracy, the ratios of the sample counts to the actual populations not being affected by variations in the degree of infestation, body size, or fleece characteristics. A valid estimate was obtained by counting all the keds on only one side of the sheep. In the vertical parting methods the ratios increased as the distance between the partings decreased, and counts were affected by marked differences in body size and fleece characteristics. The 12-inch parting method accounted for only a small portion of the ked population and the accuracy was low. In the 5-minute count the ratio depended on the degree of infestation, body size, and to a lesser degree the fleece characteristics.