scholarly journals The scattering of light by liquid boundaries and its relation to surface tension. — Part III

1925 ◽  
Vol 109 (750) ◽  
pp. 272-279 ◽  
Keyword(s):  
Surface Tension ◽  
Surface Brightness ◽  
Focal Length ◽  
Free Water ◽  
Surface Scattering ◽  
Maximum Brightness ◽  
Scattering Of Light ◽  
Simple Arrangement ◽  
The Mean ◽  
Special Category

In Part II, the phenomena of the scattering of light by the surface of transparent liquids were described in detail. No reference was, however, made to the case of water, which stands in a special category owing to the exceptional properties of this liquid. Of all known transparent fluids at ordinary temperatures water has the highest surface-tension. Its refractive index is also low, and hence its surface-opalescence may be expected to be very feeble. Fortunately, however, the internal scattering in dust-free water is also very small, being in fact much less than that for any other known liquid, and hence, provided water is obtained dust-free and with an uncontaminated surface, there should be no difficulty in observing its surface-opalescence. This was actually found to be the case. By using water subjected to repeated slow distillation in vacuo in carefully cleaned pyrex glass bulbs, it can be obtained quite pure and dust-free. The surface-opalescence may then be observed, and in agreement with anticipation is found to be very feeble; it exhibits features of polarisation and intensity distribution in different directions very similar to those shown by other liquids. For inter-comparison of the surface-scattering power of different liquids, the following simple arrangement was adopted. A beam of sunlight from a large heliostat was used and reflected vertically upwards by a second mirror inclined at 45°. The beam passed through two lenses of equal focal length, which were placed as near together as possible and formed images of the sun upon the surfaces of the liquids contained in bulbs, placed one above each of the lenses. By varying the apertures of the lenses, the brightness of the opalescent areas on the two liquid surfaces could be varied till they were estimated to be of equal brightness, as seen by the eye placed below the surfaces at approximately the same angle. The angle of observation chosen was in each case slightly greater than the critical angle, so that the surface-scattering had maximum brightness. By taking the mean of a sufficient number of readings, fairly dependable measures could be obtained of the ratio of surface-brightness, at least in the case of liquids, for which the internal scattering was not so large as to interfere with the judgment of the eye.

scholarly journals The scattering of light by liquid boundaries and its relation to surface tension. —Part II

1925 ◽  
Vol 109 (749) ◽  
pp. 150-157 ◽  
Keyword(s):  
Surface Tension ◽  
Surface Effect ◽  
Carbon Disulphide ◽  
Volume Effect ◽  
Surface Scattering ◽  
Angle Of Incidence ◽  
Scattering Of Light ◽  
Transparent Liquid ◽  
Extensive Collection ◽  
The Comparative Study

In the first paper, a description was given of the scattering of light by metallic liquid surfaces, particularly of the manner in which the intensity and state of polarisation of the scattered rays vary with the angle of incidence of the primary rays and the direction of observation. We now proceed to consider the phenomena observed when the clean and dust-free surface of a transparent liquid is strongly illuminated. Whereas in the case of metals we have a very few substances which are liquid at ordinary temperatures, an enormous variety of transparent liquids is available for the purpose of the present study. In fact, at the time the investigation was taken up, an extensive collection of pure organic chemicals had been obtained from Kahlbaum, and bulbs containing some 64 different liquids, rendered dust-free by repeated distillation in cacuo , were ready for a programme of quantitative studies of the internal lightscattering. This collection naturally proved very convenient also for the purpose of the comparative study of the surface-scattering, and the extended observations made possible by its aid served to bring out very clearly the influence on the phenomenon of the surface tension of the liquid, and thus to establish its molecular nature. As already remarked in the first paper, in the case of transparent fluids, the surface-scattering is accompanied by the internal-scattering within the liquid when a pencil of light is concentrated upon the surface, but the two effects are distinguishable from each other in several particulars. By using a good achromatic lens to focus a well-defined image of the sun on the boundary, the surface opalescence appears as a sharply bounded circular or elliptic disc of light, whose aspect varies very much with the direction of observation while that of the internal-scattering does not. The colour of the surface opalescence is also much less blue than that of the internal-scattering, and, indeed, by contrast with it appears nearly white. Green, yellow and red filters held in front of the eye diminish the brightness of the volume effect much more (in increasing order) than they do that of the surface effect, and hence assist greatly in studying or photographing the latter phenomenon. The brightness of the surface-scattering also varies with the direction of observation, while that of the internal-scattering in dust-free liquids is practically invariable. In the case of oblique incidence of the primary beam, the surface-opalescence is conspicuously brighter when viewed in directions adjacent to those of the reflected or transmitted pencils than in other directions. In fact, it then stands out very clearly, and may be distinguished even with liquids such as carbon disulphide or nitrobenzene, in which the internal-scattering is so strong that it usually overpowers the surface effect.

scholarly journals Effect of a newly developed pastille on the salivary flow rate in subjects with dry mouth symptoms: a randomized, controlled, monocentric clinical study

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
S. Bielfeldt ◽  
D. Wilhelm ◽  
C. Neumeister ◽  
U. Schwantes ◽  
K. -P. Wilhelm
Keyword(s):  
Surface Tension ◽  
Flow Rate ◽  
Gum Arabic ◽  
Salivary Flow ◽  
Salivary Flow Rate ◽  
Dry Mouth ◽  
Main Ingredient ◽  
Control Product ◽  
Swallowing Problems ◽  
The Mean

Abstract Background Xerostomia is associated with several diseases and is a side effect of certain drugs, resulting from reduced saliva secretion. Often, aged and sometimes younger people suffer from (idiopathic) xerostomia. Chewing gum and sucking pastilles may relieve symptoms of xerostomia by increasing the salivary flow rate due to the mechanical effect of sucking and gustatory stimulation. Swallowing problems and the urge to cough or experiencing a tickling sensation in the throat might be alleviated through a reduction in dry mouth symptoms. We investigated whether a pastille containing four polysaccharides increased the salivary flow rate and relieved the symptoms of dry mouth. Methods Participating subjects with xerostomia were randomized into two equally balanced treatment groups. Subjects received the pastille on Day 1 and a control product (Parafilm®) on Day 3, or vice versa. Unstimulated saliva was collected every 2.5 min for 0–10 min. Stimulated saliva was collected after subjects sucked the pastille or the control product. The salivary flow rate was determined gravimetrically, and, in parallel, the feeling of dry mouth was assessed using a visual analog scale. Saliva surface tension was measured in pooled saliva samples (0–5 min of sampling). Additionally, in stimulated saliva from six subjects who sucked the pastille, the presence of the main ingredient—gum arabic—was examined by Raman spectroscopy. Results Chewing the pastille significantly increased the mean salivary flow rate by 8.03 g/10 min compared to the mean changes after chewing the control product (+ 3.71 g/10 min; p < 0.0001). The mean score of dry mouth was significantly alleviated by the pastille (− 19.9 ± 17.9 mm) compared to the control product (− 3.3 ± 18.1 mm). No difference between the two products was seen regarding the saliva surface tension. Gum arabic was present in the saliva of all investigated subjects for up to 10 min after sucking the pastille. Conclusions The pastille was well tolerated and effective in increasing the salivary flow rate and reducing mouth dryness after sucking. These results were in line with the detection of the main ingredient, gum arabic, in saliva for up to 10 min after sucking the pastille. Trial registration German Register Clinical Trials (Deutsches Register Klinische Studien, DRKS) DRKS-ID: DRKS00017393, Registered 29 May 2019, https://www.drks.de/drks_web/navigate.do?navigationId=trial. HTML&TRIAL_ID = DRKS00017393.

On the drag-out problem in liquid film theory

2008 ◽  
Vol 617 ◽  
pp. 283-299 ◽  
Author(s):  
E. S. BENILOV ◽  
V. S. ZUBKOV
Keyword(s):  
Surface Tension ◽  
Liquid Film ◽  
Constant Velocity ◽  
Stokes Equations ◽  
Film Theory ◽  
Infinite Plate ◽  
Self Similar Solution ◽  
Self Similar ◽  
The Mean ◽  
Steady Solutions

We consider an infinite plate being withdrawn (at an angle α to the horizontal, with a constant velocity U) from an infinite pool of viscous liquid. Assuming that the effects of inertia and surface tension are weak, Derjaguin (C. R. Dokl. Acad. Sci. URSS, vol. 39, 1943, p. 13.) conjectured that the ‘load’ l, i.e. the thickness of the liquid film clinging to the plate, is l=(μU/ρgsinα)1/2, where ρ and μ are the liquid's density and viscosity, and g is the acceleration due to gravity.In the present work, the above formula is derived from the Stokes equations in the limit of small slopes of the plate (without this assumption, the formula is invalid). It is shown that the problem has infinitely many steady solutions, all of which are stable – but only one of these corresponds to Derjaguin's formula. This particular steady solution can only be singled out by matching it to a self-similar solution describing the non-steady part of the film between the pool and the film's ‘tip’.Even though the near-pool region where the steady state has been established expands with time, the upper, non-steady part of the film (with its thickness decreasing towards the tip) expands faster and, thus, occupies a larger portion of the plate. As a result, the mean thickness of the film is 1.5 times smaller than the load.

Particle paths in nonlinear Schrödinger models in the presence of linear shear currents

2018 ◽  
Vol 855 ◽  
pp. 322-350 ◽  
Author(s):  
C. W. Curtis ◽  
J. D. Carter ◽  
H. Kalisch
Keyword(s):  
Surface Tension ◽  
Schrödinger Equation ◽  
Nonlinear Schrödinger Equation ◽  
Schrodinger Equation ◽  
Nonlinear Schrodinger Equation ◽  
Stokes Drift ◽  
Carrier Wave ◽  
Nonlinear Schrödinger ◽  
The Mean ◽  
Background Shear

We investigate the effect of constant-vorticity background shear on the properties of wavetrains in deep water. Using the methodology of Fokas (A Unified Approach to Boundary Value Problems, 2008, SIAM), we derive a higher-order nonlinear Schrödinger equation in the presence of shear and surface tension. We show that the presence of shear induces a strong coupling between the carrier wave and the mean-surface displacement. The effects of the background shear on the modulational instability of plane waves is also studied, where it is shown that shear can suppress instability, although not for all carrier wavelengths in the presence of surface tension. These results expand upon the findings of Thomas et al. (Phys. Fluids, vol. 24 (12), 2012, 127102). Using a modification of the generalized Lagrangian mean theory in Andrews & McIntyre (J. Fluid Mech., vol. 89, 1978, pp. 609–646) and approximate formulas for the velocity field in the fluid column, explicit, asymptotic approximations for the Lagrangian and Stokes drift velocities are obtained for plane-wave and Jacobi elliptic function solutions of the nonlinear Schrödinger equation. Numerical approximations to particle trajectories for these solutions are found and the Lagrangian and Stokes drift velocities corresponding to these numerical solutions corroborate the theoretical results. We show that background currents have significant effects on the mean transport properties of waves. In particular, certain combinations of background shear and carrier wave frequency lead to the disappearance of mean-surface mass transport. These results provide a possible explanation for the measurements reported in Smith (J. Phys. Oceanogr., vol. 36, 2006, pp. 1381–1402). Our results also provide further evidence of the viability of the modification of the Stokes drift velocity beyond the standard monochromatic approximation, such as recently proposed in Breivik et al. (J. Phys. Oceanogr., vol. 44, 2014, pp. 2433–2445) in order to obtain a closer match to a range of complex ocean wave spectra.

scholarly journals Constructed Wetlands in Latin America and the Caribbean: A Review of Experiences during the Last Decade

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1744
Author(s):  
Marco A. Rodriguez-Dominguez ◽  
Dennis Konnerup ◽  
Hans Brix ◽  
Carlos A. Arias
Keyword(s):  
Latin America ◽  
Plant Species ◽  
Constructed Wetlands ◽  
Oxygen Demand ◽  
Free Water ◽  
Sufficient Information ◽  
Local Conditions ◽  
Latin America And Caribbean ◽  
The Mean ◽  
Low Performance

The review aims to report the state-of-the-art constructed wetlands (CW) in the Latin America and Caribbean (LAC) region not limited to national and local conditions. The aim is with a broader view, to bring updated and sufficient information, to facilitate the use of the CW technology in the different countries of LAC. Thus, 520 experiences extracted from the 169 reviewed documents in 20 countries were analyzed. According to the data, horizontal subsurface flow wetlands are the most reported CW in the region (62%), the second most common CW technology in the region is free water surface CW (17%), then vertical flow systems (9%), followed by intensified constructed wetlands (8%), and finally French systems (4%). The performance for nutrient removal is analyzed, finding that the mean of Chemical Oxygen Demand (COD), Total Nitrogen (TN), and Total Phosphorous (TP) removal efficiencies varies from 65% to 83%, 55% to 72%, and 30% to 84%, respectively. The results suggest a generally good performance for COD and TN removal, but a low performance for TP removal. Regarding plant species used for CWs, 114 different plant species were reported, being until now the most extensive report about plant species used in CWs in the LAC region.

Influence of nucleating agent type on the morphology of extruded polyetherimide foam for printed circuit boards*

2019 ◽  
Vol 56 (3) ◽  
pp. 317-341 ◽  
Author(s):  
Clemens Keilholz ◽  
Daniel Raps ◽  
Thomas Köppl ◽  
Volker Altstädt
Keyword(s):  
Surface Tension ◽  
Printed Circuit Boards ◽  
Particle Diameter ◽  
Nucleating Agent ◽  
Nucleating Agents ◽  
Circuit Boards ◽  
Printed Circuit ◽  
Foam Morphology ◽  
The Mean ◽  
Mean Particle Diameter

This work focuses on the development of foamed high temperature thermoplastic substrates for printed circuit boards. For this application it is necessary to achieve mean cell diameters smaller than 30 µm in order to be able to realize vias and high packaging densities (miniaturization). Different additives as nucleating agents, namely macro- and micro-crystalline talc, silica, calcium carbonate, and wollastonite, were melt-compounded with polyetherimide using a twin-screw extruder. Foamed samples are prepared by foam extrusion using a slit die and CO2 as physical blowing agent. The aim of this study is to analyze the influence of the mean particle size and the particle surface tension on the mean cell diameters. Therefore, the shape of the additives, the foam morphology, and the elongational viscosity were considered. The additives with a suitable particle size and surface tension exhibit a positive influence on the foam morphology, resulting in smaller cell diameters (<30 µm), a narrower cell size distribution and a foam density lower than 900 kg/m3. If the mean particle diameter of the nucleating agents is lower than 0.6 µm in this study, no nucleation effect could be observed. This is related to the fact that no heterogeneous nucleation occurs, if the particle diameter is too small. If the mean particle diameter of the used additives is larger than 1.5 µm, which could be demonstrated in this study in case of polyetherimide, then the additive acts as nucleating agent and heterogeneous nucleation occurs. Furthermore, it was observed that the mean cell diameter was affected by the different surface tensions of the studied nucleating agents.

Free Water Clearance in Patients with Essential Hypertension

1973 ◽  
Vol 45 (4) ◽  
pp. 469-477
Author(s):  
E. J. Dorhout Mees ◽  
H. de Graaf
Keyword(s):  
Salt Intake ◽  
Free Water ◽  
Normal Subjects ◽  
Mean Value ◽  
Exponential Relationship ◽  
Free Water Clearance ◽  
Uncomplicated Hypertension ◽  
The Mean ◽  
Different Levels ◽  
Water Clearance

1. Free water clearance (CH2O) was measured in sixteen normal subjects and twenty-five patients with uncomplicated hypertension at different levels of salt intake. 2. In normal subjects CH2O and Na+ excretion were related thus: log Na+ excretion = 0·1685 + 0·1508 × CH2O. At a given value for Na+ excretion the standard deviation for CH2O was ±1·5 ml min−1. 3. The mean value for the ratio CH2O/creatinine clearance was higher in the hypertensive patients than in controls at all levels of Na+ excretion. 4. Most previous studies reporting decreased values for CH2O in hypertension can be explained by the exponential relationship between CH2O and Na+ excretion.

586. Colour changes in heated and unheated milk: IV. the theoretical background to the reflectance changes in separated milk

1955 ◽  
Vol 22 (2) ◽  
pp. 200-204 ◽  
Author(s):  
H. Burton
Keyword(s):  
Soluble Protein ◽  
Colloidal Particles ◽  
Theoretical Background ◽  
General Level ◽  
Colloidal Solutions ◽  
Casein Micelles ◽  
Scattering Of Light ◽  
Colour Changes ◽  
Mean Size ◽  
The Mean

The theory of the scattering of light in colloidal solutions is considered. As a result it is suggested that the reflectance changes in milk which involve a rise or fall in the general level of reflectance are caused by an increase or decrease in the mean size of the colloidal particles. Whether the particles responsible are the casein micelles or the soluble protein depends on the phenomenon to be explained.The change in reflectance on the browning of milk, which is dependent on wavelength, is considered to have a more complex cause, involving the production of absorbing molecules.

scholarly journals Probing Galactic Outskirts with Dragonfly

2016 ◽  
Vol 11 (S321) ◽  
pp. 137-146 ◽  
Author(s):  
Roberto Abraham ◽  
Allison Merritt ◽  
Jielai Zhang ◽  
Pieter van Dokkum ◽  
Charlie Conroy ◽  
...  
Keyword(s):  
Surface Brightness ◽  
Wide Field ◽  
Rich Variety ◽  
Neutral Gas ◽  
Early Results ◽  
Low Surface Brightness ◽  
Stellar Halo ◽  
Nearby Galaxies ◽  
The Mean ◽  
The Rich

AbstractWe describe the challenges inherent to low surface brightness imaging and present some early results from the Dragonfly Nearby Galaxies survey. Wide field, ultra-low surface brightness imaging (μg > 31 mag arcsec−2) of the first eight galaxies in the survey reveals a rich variety in the distribution of stars in the outskirts of luminous nearby galaxies. The mean stellar halo mass fraction is 0.009 ± 0.005 with a peak-to-peak scatter of a factor of > 100. Some galaxies in the sample feature strongly structured halos resembling that of M31, but three of the eight galaxies have halos that are completely undetected in our data. We conclude that spiral galaxies as a class exhibit a rich variety in stellar halo properties, implying that their assembly histories have been highly non-uniform. While the outskirts of some galaxies are dominated by halos with the rich substructures predicted by numerical simulations, in other cases the outermost parts of galaxies are simply the extrapolated smooth starlight from enormous stellar disks that closely trace neutral gas morphology out to around 20 scale lengths.

Motion driven by surface-tension gradients in a tube lining

1974 ◽  
Vol 62 (4) ◽  
pp. 737-751 ◽  
Author(s):  
Stephen H. Davis ◽  
An-Kuo Liu ◽  
George R. Sealy
Keyword(s):  
Boundary Layer ◽  
Surface Tension ◽  
Circular Tube ◽  
Fluid Layer ◽  
Approximate Solutions ◽  
Thin Layers ◽  
Planar Case ◽  
Inner Surface ◽  
The Mean ◽  
Axial Surface

A fluid layer that lines the inner surface of a circular tube has motion induced by axial surface-tension gradients. The lubrication equations for the system are analysed and it is found that even for thin layers the motions differ markedly from those in planar layers. The planar case serves as a class of outer solutions. These approximate solutions are modified by a boundary-layer correction where the mean surface tension is important.

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