Plastic Beads Research Articles

EXPERIMENTS ON DENSITY AND TURBIDITY CURRENTS: I. MOTION OF THE HEAD

Two series of experiments were performed in a lucite flume 5 meters long, 50 cm deep, and 15.4 cm wide. In the first series saline density currents were formed by pumping salt solutions at constant discharge into the tilted flume. In the second series, the flume was horizontal and turbidity currents were formed by the releasing of suspensions of plastic beads from a box at one end.In both series of experiments a characteristic head was formed at the front of the flow. It was found that the motion of the head in the turbidity current experiments was closely described by laws developed by Keulegan (1958) for saline surges, and it is concluded that certain aspects of the motion of turbidity current heads can be investigated indirectly by means of experiments on density currents formed from clay suspensions or salt solutions.The salt-solution experiments were designed to investigate the effect of bottom slope on the motion of density current heads. It was found that the velocity of density (and by inference, turbidity) current heads on slopes up to 4% is adequately expressed by Keulegan's formula[Formula: see text]where v is the velocity of the head, Δρ is the difference between the density of the current (ρ) and that of the overlying water, d2 is the thickness of the head, and g is the acceleration due to gravity. The numerical coefficient is approximately constant, but may increase slightly with increase in slope. The form of the equation differs greatly from that of the Chézy equation which has previously been used for the analysis of the movement of turbidity currents.Observations were also made regarding the shape of the head and the motion within and in front of the head.

Turbidity-Current Experiments: ABSTRACT

Experiments were performed in the W. M. Keck Laboratory, California Institute of Technology, using a lucite channel 5 meters long, 50 cm. deep, and 15.4 cm. wide. Turbidity-current were produced by releasing suspensions of plastic beads from a lock at one end of the channel. The bottom of the flume was horizontal and before release of the suspension the water level was the same within the lock and the main channel; the experimental results may therefore be compared with the results obtained by Keulegan (1958) for saline surges. Experiments were performed at two depths (20 and 30 cm.), and two suspension concentrations (about 25% and 45% concentration by volume) were used. The sediment consisted of perfectly spherical plastic beads with a density of 1.52 and an av rage size of 0.18 mm. The results show that the shape of the head, the initial velocity, and the relation between the velocity of the head and its thickness and density are very similar to those reported for saline surges. The velocity of the head is given by the equation [EQUATION] where g^prime = g^Dgre/e, d2 is the thickness of the head, and C is a coefficient with a value of 0.75. In another series of experiments, with saline density currents, it was found that C varies little with increase in slope of the bottom, up to a slope of 0.04. The velocity (u) of the water near the bottom, at a distance x in front of the head, was found to be given by the equation [EQUATION] Two types of graded bed were formed, depending on the concentration of the suspension used. The normal type of graded bed, formed by surges with low sediment concentration, shows continuous grading within the bed at nearly all percentiles. The coarse-tail type of graded bed, formed by high-concentration surges, shows little grading through most of the bed, except for the coarsest 2-5 per cent of the size distribution. The differences between the two types of grading can be related to the depositional mechanics, which are revealed by slow-motion movies. In low-concentration flows, the bed is deposited layer by layer. In high-concentration flows, most of the bed is deposited first as an expanded or quick bed which continues to shear and to be disturbed by waves which form at the i terface between the bed and the flow above. As the bed comes to rest, the waves disappear and the upper surface becomes perfectly flat. A 300-foot color movie of the experiments will be shown. End_of_Article - Last_Page 627------------

ENRICHMENT OF SERINE-ACCEPTOR SOLUBLE RNA BY NUCLEIC ACID GELS.

Nucleic acid gels prepared by ultraviolet irradiation of polyuridylic acid on plastic beads can absorb a species of soluble RNA with increased serine-acceptor activity.

Density Ranges of Plastic Beads for Milk Density Measurement

Density Ranges of Plastic Beads for Milk Density Measurement

Estimating Solids-Not-Fat in Herd Milk Using the Plastic Bead Method of Golding

This study was made to derive and compare equations for estimating solids-not-fat (SNF) in herd milk using the plastic bead method of Golding. Milk was sampled from farm bulk tanks at delivery on alternate days from 64 herds for 1 yr. In all, 1,423 herd samples were analyzed for per cent milk fat, per cent protein (dye-binding), specific gravity (plastic bead method), and per cent total solids by oven-drying. Percentage SNF was estimated by difference (per cent total solids-per cent milk fat).Multiple regression equations were calculated and compared for estimating per cent SNF from density. Single equations were unsatisfactory, because of significant differences between the partial regressions for breeds. The most efficient equations were those including density and per cent milk fat or per cent protein within six milk fat intervals. For these, the standard errors of estimate ranged from 0.11 to 0.14% SNF, and fractions due to regression ranged from 0.60 to 0.77. The average deviations for annual herd averages among herds was 0.04% SNF, with 95% confidence limits of 0.10% SNF. For months the average deviation was 0.05% SNF with 95% confidence limits of 0.14% SNF.

Comparison of Relative Accuracy between Testing Semimonthly Composites or Single Random Samples of Herd Milk for Composition

Summary The relative accuracy of testing composites or single random samples for composition was compared for milk samples from 30 herds. The bulk milk from each herd was sampled on alternate days for 2 wk during February, May, August, and November. Percentage milk fat in composite samples averaged 0.055 and 0.021% less than the average of the fresh milk aliquots, respectively, for Laboratories I and II. The average per cent SNF (TS gravimetric—F Babcock) in composite samples was 8.95%, compared with 8.91% in their fresh milk aliquots. For testing composite samples for per cent SNF, the plastic bead method of Golding was equal or superior to the gravimetric procedure. Two random tests for per cent milk fat each 2 wk for herds on alternate-day delivery estimated per cent milk fat as accurately as one test of a composite sample. Comparisons between testing single random samples and the average of the fresh milk aliquots over 2-wk periods showed variations from regression (S y · x ) of 0.13, 0.10, 0.13, 0.11, 0.08, and 0.12%, respectively, for milk fat, SNF (gravimetric), SNF (plastic beads-single equation), SNF (plastic bead-milk fat interval equations), milk protein, and lactose + mineral.

Influence of Breed and Milk Fat Percentage when Estimating Solids-Not-Fat in Milk of Individual Cows by the Plastic Bead Method of Golding

Influence of Breed and Milk Fat Percentage when Estimating Solids-Not-Fat in Milk of Individual Cows by the Plastic Bead Method of Golding

Continuous-Flow Mechanical Cell Disintegrator

A mechanical cell disintegrator is described which efficiently ruptures bacteria, molds, actinomycetes, and yeasts. Cells were broken continuously in a chamber by rapid shaking of a mixture of cell suspension, plastic beads, and air. Volume capacity for complete breakage varied with experimental conditions and the microorganism involved, and ranged from 840 ml/hr to greater than 4,470 ml/hr. Subcellular preparations made with the machine retained a high level of enzymatic activity.

Continuous-flow mechanical cell disintegrator.

A mechanical cell disintegrator is described which efficiently ruptures bacteria, molds, actinomycetes, and yeasts. Cells were broken continuously in a chamber by rapid shaking of a mixture of cell suspension, plastic beads, and air. Volume capacity for complete breakage varied with experimental conditions and the microorganism involved, and ranged from 840 ml/hr to greater than 4,470 ml/hr. Subcellular preparations made with the machine retained a high level of enzymatic activity.

Plastic Beads as a Supporting Medium in Nutriculture Systems1

Plastic Beads as a Supporting Medium in Nutriculture Systems¹

Accuracy of the Plastic Bead Method of Measuring Solids-not-fat of Milk Under Field Conditions1,2

Summary The plastic bead method of measuring solids-not-fat (SNF) content of milk is a practical test for use by DHIA supervisors in the field. This method can be as accurate under field conditions as in the laboratory. The mean differences between duplicate readings in the field, between duplicates in the laboratory, and between duplicate readings in the field and the laboratory were .07, .14, and .16% SNF, respectively. Correlations between duplicate readings, between methods, and between field and laboratory were .86 or greater. Although the lactometer method appears slightly more accurate than the bead method, the difference is so small as to merit little consideration in practical use.

Vascular lesions in experimental pulmonary embolism

Numerous experimental studies have shown that it is possible to produce pulmonary vascular lesions by different methods. Two of the most effective methods are: (a) multiple embolization with blood clots, and (b) pulmonary hypertension produced by shunting systemic flow into the pulmonary artery or into one of its branches. Since many studies have failed to separate the effects of multiple emboli from those of pulmonary hypertension, a series of experiments were planned in which unilateral multiple pulmonary embolism was produced by injecting autologous fibrin clots in one group of animals, autologous whole blood clots in a second group, and plasticbead emboli in a third group of dogs. Appropriate controls received the emboli through a peripheral vein, whereas the experimental animals were embolized through a catheter introduced into the left pulmonary artery. Another group of animals received a single embolization of whole blood clots into the left pulmonary artery and were sacrificed at intervals varying between 0 and 72 hours. The results were that in all animals which received fibrin or clotted blood emboli the three following types of pulmonary vascular lesions were found: (a) organized or partially organized clots in the lumen of arteries with minimal lesions in the wall, with the exception of, (b) a peculiar vacuolated aspect of the endothelium that was in intimate contact with the clots, and (c) peripheral arteriolitis without alteration in the arteriolar wall, accompanied by focal hemorrhage, usually localized at the branching sites of vessels. These lesions appeared 24 hours after the injection of emboli. No anatomic traces of pulmonary hypertension were found. No anatomic changes were seen in those instances in which plastic beads were given. The results are discussed and it is pointed out that, whereas organized thrombi and endothelial vacuolation are due to the presence of the embolus, areteriolitis is probably the result of a fibrin factor. Pulmonary hypertension and hypersensitivity can be discarded as causal agents of the vascular lesions found in these experiments.

Demonstrating the relative polarity of non-conducting liquids

The apparatus described is based on the principle that an increase in the dielectric constant of the medium causes a decrease in the force of attraction between charged particles (in this case, two plastic beads).

Comparative Accuracy of the Plastic Bead Method of Golding and the Lactometer Method of Watson for Routine Determination of Solids-not-fat in Milk

The plastic bead method of Golding was evaluated as a rapid test for solids-not-fat in the milk of individual cows. Ten plastic beads each varying 1mg. in density in the range of 1.025 to 1.034 are placed in a 4-oz. sample jar fitted with a plastic grid and a metal screw-cap. Milk is sampled directly into the sample jar and after the fat has been liquefied by heating to 104° F. and holding for 5min., the test is made by counting the number of sinking beads at 68° F. A formula for converting the number of sinking beads to per cent SNF was calculated, using 1,873 milk samples from Guernsey, Holstein, and Jersey cows of 53 herds. This formula is: per cent SNF = 9.13−0.279 B + 0.307% F where B is the number of plastic beads sinking at 68° F. and per cent F is the percentage fat in the milk. In a second experiment, plastic beads and the lactometer of Watson were compared, using gravimetric assays for reference. On 300 milk samples from six breeds the standard deviation from regression was 0.17% SNF for the lactometer and 0.18% SNF for the plastic beads. The plastic bead method is sufficiently accurate for the routine testing of milk of individual cows for per cent SNF. The method is simple and rapid and requires no more milk than is routinely sampled for DHIA testing.

The demonstration of pulmonary arteriovenous shunts in normal human subjects, and their increase in certain disease states.

The evidence for existence of arteriovenous shunts in the normal human lung is strong but necessarily indirect. Simultaneous measurements of oxygen tension in alveolar air and in arterial blood consistently show a degree of venous admixture in both normal and abnormal subjects (1), but no information has been obtained about the path taken by this unventilated blood. The passage of small glass or plastic beads through the pulmonary circulation has demonstrated potential pathways as large as 200ju in diameter (2, 3), but this technique involves an artificial distention of the vascular bed and gives no information about the extent to which such pathways may function physiologically. The present investigation was based on the hypothesis that the decreased venous inflow to the right atrium and reduced blood flow through the pulmonary vessels during the Valsalva maneuver, as well as the rebound effects after release of the maneuver, might alter the flow through such shunts, and that this alteration could be detected by continuous measurement of the systemic arterial oxygen saturation. No distinction would necessarily be made by this technique between true arteriovenous anastomoses, with ventilation-perfusion ratio of zero, and poorly ventilated alveolar capillaries, with ventilation-perfusion ratio below the average for the whole capillary bed. We have studied nine normal subjects, and 16 patients with cardiac or pulmonary disease; results in 12 additional patients with intracardiac shunts have been included for comparison.

Evidence of the Atrial Location of Receptors Influencing Urine Flow

Receptors believed responsible for the diuresis of negative pressure breathing have been located by observing the effect on urine flow of a stepwise engorgement of the intrathoracic vascular bed. Distension of the pulmonary arterial tree (injection of plastic beads) and of the entire pulmonary circulation (snares on the pulmonary veins) were without effect. A diuresis was however elicited by expansion of a balloon in the left atrium. It is concluded that stretch receptors in the left atrium and terminal pulmonary veins are instrumental in a mechanism linking changes in the actively circulating blood volume with homeostatic responses of the kidney.

A Falling Sphere Method for Studying Clotting in Systems of Purified Blood Components

Summary1. To study the coagulation of the fibrinogen-thrombin system, a simple rapid method has been developed which measures the time required for the developing coagulum to stop the fall of a plastic bead in a glass tube containing the fibrinogen-thrombin mixture.2. The “clotting time” thus obtained, increases somewhat with the age of the thrombin and fibrinogen solutions.3. Kinetic studies of the coagulation process indicate that there is no change in viscosity for a considerable time after the mixing of thrombin and fibrinogen, but that this phase is followed by an abrupt increase in viscosity signifying coagulation of the system.4. The rate of clotting varies with thrombin concentration in a roughly linear fashion.