Changes In Particle Concentration Research Articles

Migration of suspended particles in plane stationary ultrasonic field

The time-averaged motion of microscopic particles in plane stationary sound fields is investigated. A generalized kinetic theory of particle migration in which the effect of particle diltusion is taken into account is formulated and the particle distributions at the rather early stage and after a sufficient sound irradiation are derived analytically from the theory. It is found that the nodal change of particle concentration of microscopic polystyrene latex dispersions is well predicted by the present theory, independently of the particle size, the sound frequency and the energy density of sound. The condition of formation of the Kundt's tube striation is also characterized theoretically.

Relationships between seston, available food and feeding activity in the common mussel Mytilus edulis

The feeding and metabolic rates of Mytilus edulis L. of different body sizes were measured in response to changes in particle concentrations ranging from 2 to 350 mg l-1. Rates of oxygen consumption were not significantly affected by changes in seston concentration, whereas clearance rates gradually declined with increasing particle concentration. Pseudofaeces production was initiated at relatively low seston concentrations (<5 mg l-1). Marked seasonal changes were recorded in the composition of suspended particulates (seston) in an estuary in south-west England. Total seston was sampled at frequent intervals throughout an annual cycle and analysed in terms of: particle size-frequency distributions, total dry weight (mg l-1), inorganic content, chlorophyll a, carbohydrate, protein and lipid. The particulate carbohydrate, protein and lipid content provided an estimate of the food content of the seston. The results are discussed in terms of the “food available” to a nonselective suspension feeder, such as M. edulis, during a seasonal cycle. The effect of inorganic silt in suspension was mainly to limit by “dilution” the amount of food material ingested rather than to reduce the amount of material filtered by the mussel. In winter, the food content of the material ingested was 5%, and this increased to 25% during the spring and summer.

Studies on the electrolyte flocculation of oil/water emulsion with special reference to cationic bindings at isoelectric points

The stable toluene-in-water emulsions were prepared using sorbiton monolaurate as emulsifier. The electrokinetic potentials of the system were measured electrophoretically. The energy profiles revealed the high degree of stability of the emulsion and reversible flocculation took place in secondary minima. The flocculation studies have been carried out by measuring change in particle concentration on ageing the system haemocytometrically. Adsorption constants, number of binding sites available, charge density and electrochemical free energy of adsorption have also been evaluated with the help of flocculating concentration at isoelectric point.

Determination of the smallest particle size detectable in condensation nucleus counters by observation of the coagulation of SO 2 photo-oxidation products

The method proposed by Walter et al. (1973) for determining the smallest particle size detectable in condensation nucleus counters (CNC) was conducted experimentally. A dynamic flow system was developed for observation of the particle concentration changes due to coagulation for particles produced by heteromolecular nucleation of H 2SO 4 and water vapor through the irradiation of SO 2 and carrier gas with u.v.-light. Experiments indicate the presence of thermal coagulation as well as other processes. Evidence was found to isolate the coagulation effects from other processes. A smallest particle size detectable in condensation nucleus counters with standard expansion ratio thus was determined to be r L = 1.6 × 10 −7 cm.

The feeding rates of the pelagic tunicate Pegea confederata and two other salps1

The filtration rates of Pegea confederata, Salpa maxima, and Cyclosalpa affinis were measured. Filtration rates increase exponentially with increasing length and body carbon. Filtration rates exceeding 100 ml min‒1 were recorded. The mucous net of P. confederata can retain particles at least as small as 0.7 µ. There appears to be no change in filtration rate with changes in particle concentration. Filtration rate per microgram of carbon increases with increasing body weight of salps in contrast to ascidians, perhaps because salps use muscular pumping rather than ciliary currents to transport water. The filtration rates recorded suggest that the role of salps in the open ocean ecosystem may be more important than previously assumed.

Diffusion to a random array of identical spherical sinks

The effect of the insertion of one additional spherical sink on the steady state diffusion field of particles migrating to a random array of identical sinks of the same type is determined. The change in particle concentration as a function of the distance from the inserted sink, when averaged over all permissible configurations of the original array, is shown to be of the same form as that arising from insertion of a sink of the same type in a homogeneous lossy medium. The loss rate per atom in this effective medium is found to be of the form DkM2(c̃ (r) − c̄), where D is the particle diffusivity, c̃(r) an ensemble-averaged concentration (atomic fraction) defined in the text, and c̄ is the prescribed concentration at each sink surface. The sink strength, kM2, is calculated to be kM2 = λ2 {1 + λa − λ2a2 (16 + γ + ln 6λa)}, with λ2 = 4πCa and γ Euler's constant, C being the average volume concentration of sinks, a their common radius. These results are shown to substantiate the standard rate theory treatment of simultaneous diffusion to many sinks and confirm the existence of correction terms in λa to the sink strength normally employed in this method. L'effet de l'insertion d'un piège additionnel de forme sphérique sur le champ de diffusion à l'état stationnaire de particules en migration à travers un arrangement aléatoire de pièges identiques de même type est discuté. Il est montré que la variation de concentration des particules en fonction de la distance au piège inséré, quand on fait la moyenne de toutes les configurations possibles de l'arrangement initial, est de la même forme que celle provenant de l'insertion d'un piege de même type dans un milieu homogène. Le taux de perte par atome dans ce milieu effectif a été trouvé égal àDkM2(c̃ (r) − c̄), oú D est la diffusivité des particules, c̃(r) une concentration moyenne (fraction atomique) définie dans le texte et c̄ est la concentration prescrite pour chaque surface de piège. La force du piège, kM2, est calculée comme étant égale à λ2 [1 + λa − λ2a2 (16 + γ + ln 6λa)avec λ2 = 4πCa et λ la constante d'Euler, C étant la concentration en volume moyenne des pièges, a leur rayon commun. Ces résultats sont présentés comme confirmant le traitement théorique classique de diffusion simultanée vers de nombreux pièges et l'existence de termes correctifs dans λa pour la force des pièges normalement utilisée dans cette méthode. Es wurde der Einfluss des Einbaus einer zusätzlichen sphärischen Senke auf das stationäre Diffusionsfeld von Teilchen untersucht, die zu statistisch angeordneten identischen Senken desselben Typs wandern. Die Änderung der Teilchenkonzentration als Funktion des Abstandes von der eingebauten Senke hat bei einer Mittelung über alle erlaubten Konfigurationen der ursprünglichen Anordnung dieselbe Form wie jene, die vom Einbau einer Senke derselben Art in einem Medium mit homogen verschmierten Senken herrührt. Die Verlustrate pro Atom in diesem effektiven Medium hat die Form DkM2(c̃ (r) − c̄), wobei D der Teilchendiffusionskoeffizient, c̃(r) eine im Text definierte gemittelte Konzentration einer Einheit als Atombruch und c̄ die vorgeschriebene Konzentration an jeder Oberfläche der Senken ist. Die Stärke kM2 der Senke wird angegeben als kM2 = λ2 {1 + λa − λ2a2 (16 + γ + ln 6λa)}, wobei λ2 = 4πCa und γ die Eulersche Konstante ist; C ist die mittlere Volumenkonzentration und a der gemeinsame Radius der Senken. Die Ergebnisse erhärten die klassische reaktionskinetische Behandlung einer gleichzeitigen Diffusion zu vielen Senken und bestätigen die Existenz von λa-Korrekturtermen für die Stärke der Senke, die bei dieser Methode normalerweise verwendet wird.

Lidar study of atmospheric particulate over the city of London

Abstract The laser radar (lidar) is capable of detecting weak concentrations of particulate in the lower atmosphere at ranges up to several kilometres. Through this technique, models of thermal convection and theories of particulate diffusion may be studied by observing the spatial and temporal changes in particulate concentration. A pulsed ruby lidar has been assembled at this University, with scanning optics located at an elevated position overlooking the city. Criteria have been evolved here for deriving profiles of extinction coefficient, and particulate number and mass concentration from the lidar signatures. Sample profiles of particulate concentrations are given for comparison with the design prediction of lidar sensitivity.

Water-affected fraction of natural 1.5–9 μ diameter aerosol particles

The water-affected fraction of a given size class of an aerosol population reflects the change in particle concentration when that population becomes hydrosolized. The water-affected fraction was determined for natural aerosol particles in the 1.5–9 μ diameter size range. The largest change was observed in the 1.5–3 μ size group in a polluted atmosphere, especially in the presence of scattered rain and overcast sky. The aggregates formed through evaporation of cloud droplets seem to be the principal source of smaller hydrosol particles. Parallel determination of changes in air concentration of chloride particles and water-affected fraction of aerosol particles, coupled with analysis of air parcel trajectories, showed excellent agreement in identification of the movement of maritime air parcels over the central part of the continent (Colorado).