The Theory of Osmosis

2003 ◽  
Author(s):  
Larry D. Howlett
Keyword(s):  
Osmotic Pressure ◽  
Atmospheric Pressure ◽  
Traditional Theory ◽  
Theoretical Determination ◽  
Concentration Difference ◽  
Capillary Action ◽  
The Difference ◽  
Basic Equations ◽  
Thermodynamic Derivation

A fresh view for explaining the process of osmosis and the phenomenon of osmotic pressure is presented. The process of osmosis was identified and modeled more than 100 years ago. Others have unsuccessfully challenged the original model developed by J.H. van’t Hoff. We revisit the basic equations and assumptions used in the thermodynamic derivation of the osmosis model. And, we propose a small but significantly different view of the traditional theory of osmosis. From this new view of osmosis and the osmosis experiment, we conclude that osmosis occurs at atmospheric pressure. In cellular membranes, flow from the solvent to the solution is related to the vapor pressure difference determined from the concentration difference with Raoult’s law. Furthermore, we suggest that osmotic pressure as determined from the osmosis experiment is related to both the solution properties and the membrane characteristics. We suggest that the difference between experimental and theoretical determination of osmotic pressure can be attributed to capillary action that may occur in some man made membranes.

Barometrical observations, showing the effect of the direction of the wind on the difference between distant barometers

1843 ◽  
Vol 4 ◽  
pp. 386-387
Keyword(s):  
Atmospheric Pressure ◽  
The North ◽  
Heating And Cooling ◽  
Westerly Winds ◽  
Different Seasons ◽  
The Subject ◽  
The Difference ◽  
The Times ◽  
The One

The author institutes a comparison between the barometric heights as observed at the Apartments of the Royal Society, and at his house in Herefordshire, in the neighbourhood of Ross, with a view to ascertain the influence of prevailing winds on the atmospheric pressure. The barometers thus compared together were of the same construction, and by the same maker; and the times of observation, namely nine o’clock a. m. and three o’clock p. m., were the same at both places, the distance between which is 110 miles in longitude, and about 20 in latitude. The degree of accordance in the march of the two barometers is exhibited by that of curves traced on three sheets accompanying the paper. The results are given in eight tables. The author agrees with Schubler in ascribing the currents prevailing in the atmosphere to the variable relations of heating and cooling which obtains between the Atlantic Ocean and the continent of Europe at different seasons; the facts ascertained by the series of observations here presented being in accordance with that hypothesis. If the northerly and westerly winds in England be partly the effect of the expansion of the air on the continent, then the barometer which is nearest to the continent, or in this instance that at London, ought to be relatively more depressed than the one more distant; or if the southerly and easterly winds be regarded as proceeding to the ocean, then, for a similar reason, the barometer nearest to the ocean ought to be relatively depressed; and that both these effects are produced, is shown by the tables. This view of the subject also, the author remarks, is corroborated by Raymond’s observations, detailed in his memoir on the determination of the height of Clermont Ferrand, from which it appears that with the north winds, the southern barometer was most depressed; while the reverse occurred with the southerly winds.

scholarly journals Prediction of initial shape of functionally graded ceramic pre-forms for near-net-shape sintering

2003 ◽  
Vol 35 (1) ◽  
pp. 5-12 ◽  
Author(s):  
A.L. Maximenko ◽  
Der Biest ◽  
E.A. Olevsky
Keyword(s):  
Numerical Procedure ◽  
Continuum Theory ◽  
Functionally Graded ◽  
Theoretical Determination ◽  
Initial Shape ◽  
Ceramic Components ◽  
Near Net Shape ◽  
The Difference ◽  
The Continuum

Sintering of macroscopically inhomogeneous ceramic components is always accompanied by shape distortions due to the difference in shrinkage rates of powder elements. The objective of the present investigation is the theoretical determination of initially distorted shapes of the green bodies needed to provide near-net-shape sintered components. Calculations are based on a finite element implementation of the continuum theory of sintering. In this theory, sintering is considered as a creep under the influence of the compressive ?sintering stress?. To predict the initial shapes of the components the ?inverse? numerical procedure is used when the component is assumed to swell from the final shape to the initial one under the influence of the pressure equal (with the exception of sign) to the sintering stress.

scholarly journals Thermal Conductivity of Frozen Sediments Containing Self-Preserved Pore Gas Hydrates at Atmospheric Pressure: An Experimental Study

Geosciences ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 65 ◽  
Author(s):  
Evgeny Chuvilin ◽  
Boris Bukhanov
Keyword(s):  
Thermal Conductivity ◽  
Physical Properties ◽  
Gas Hydrates ◽  
Atmospheric Pressure ◽  
The Self ◽  
Needle Probe ◽  
Hydrate Saturation ◽  
The Difference ◽  
Hydrate Bearing Sediments

The paper presents the results of an experimental thermal conductivity study of frozen artificial and natural gas hydrate-bearing sediments at atmospheric pressure (0.1 MPa). Samples of hydrate-saturated sediments are highly stable and suitable for the determination of their physical properties, including thermal conductivity, due to the self-preservation of pore methane hydrate at negative temperatures. It is suggested to measure the thermal conductivity of frozen sediments containing self-preserved pore hydrates by a KD-2 needle probe which causes very little thermal impact on the samples. As shown by the special measurements of reference materials with known thermal conductivities, the values measured with the KD-2 probe are up to 20% underestimated and require the respective correction. Frozen hydrate-bearing sediments differ markedly in thermal conductivity from reference frozen samples of the same composition but free from pore hydrate. The difference depends on the physical properties of the sediments and on changes in their texture and structure associated with the self-preservation effect. Namely, it increases proportionally to the volumetric hydrate content, hydrate saturation, and the percentage of water converted to hydrate. Thermal conductivity is anisotropic in core samples of naturally frozen sediments that enclose visible ice-hydrate lenses and varies with the direction of measurements with respect to the lenses. Thermal conductivity measurements with the suggested method provide a reliable tool for detection of stable and relict gas hydrates in permafrost.

scholarly journals OSMOTIC PROPERTIES OF THE EGG CELLS OF THE OYSTER (OSTREA VIRGINICA)

1941 ◽  
Vol 25 (2) ◽  
pp. 215-227 ◽  
Author(s):  
Balduin Lucké ◽  
R. A. Ricca
Keyword(s):  
Cell Surface ◽  
Osmotic Pressure ◽  
Cell Volume ◽  
Diffraction Method ◽  
Egg Cell ◽  
Concentration Difference ◽  
Wide Range ◽  
The Difference ◽  
Inactive Cell ◽  
Osmotic Properties

Investigations of the osmotic properties of oyster eggs by a diffraction method for measuring volumes have led to the following conclusions: 1. The product of cell volume and osmotic pressure is approximately constant, if allowance is made for osmotically inactive cell contents (law of Boyle-van't Hoff). The space occupied by osmotically inactive averages 44 per cent of cell volume. 2. Volume changes over a wide range of pressures are reversible, indicating that the semipermeability of the cell during such changes remains intact. 3. The kinetics of endosmosis and of exosmosis are described by the equation, See PDF for Equation, where dV is rate of volume change; S, surface area of cell, (P-Pe), the difference in osmotic pressure between cell interior and medium, and K, the permeability of the cell to water. 4. Permeability to water during endosmosis is 0.6µ3 of water per minute, per square micron of cell surface, per atmosphere of pressure. The value of permeability for exosmosis is closely the same; in this respect the egg cell of the oyster appears to be a more perfect osmometer than the other marine cells which have been studied. Permeability to water computed by the equation given above is in good agreement with computations by the entirely different method devised by Jacobs. 5. Permeability to diethylene glycol averages 27.2, and to glycerol 20.7. These values express the number of mols x 10–15 which enter per minute through each square micron of cell surface at a concentration difference of 1 mol per liter and a temperature of 22.5°C. 6. Values for permeability to water and to the solutes tested are considerably higher for the oyster egg than for other forms of marine eggs previously examined. 7. The oyster egg because of its high degree of permeability is a natural osmometer particularly suitable for the study of the less readily penetrating solutes.

FRACTIONAL DETERMINATIONS OF URINARY 17-KETOSTEROIDS IN HYPEREMESIS GRAVIDARUM

1962 ◽  
Vol 41 (1) ◽  
pp. 123-128 ◽  
Author(s):  
Pentti A. Järvinen ◽  
Sykkö Pesonen ◽  
Pirkko Väänänen
Keyword(s):  
Hyperemesis Gravidarum ◽  
First Trimester ◽  
Control Group ◽  
Before And After ◽  
Daily Urine ◽  
First Trimester Of Pregnancy ◽  
The Difference

ABSTRACT The fractional determination of 17-ketosteroids in the daily urine was performed in nine cases of hyperemesis gravidarum and in four control cases, in the first trimester of pregnancy both before and after corticotrophin administration. The excretion of total 17-KS is similar in the two groups. Only in the hyperemesis group does the excretion of total 17-KS increase significantly after corticotrophin administration. The fractional determination reveals no difference between the two groups of patients with regard to the values of the fractions U (unidentified 17-KS), A (androsterone) and Rest (11-oxygenated 17-KS). The excretion of dehydroepiandrosterone is significantly higher in the hyperemesis group than in the control group. The excretion of androstanolone seems to be lower in the hyperemesis group than in the control group, but the difference is not statistically significant. The differences in the correlation between dehydroepiandrosterone and androstanolone in the two groups is significant. The high excretion of dehydroepiandrosterone and low excretion of androstanolone in cases of hyperemesis gravidarum is a sign of adrenal dysfunction.

THE SUBJECT FIELD OF INSTITUTIONAL EDUCATION: THE SENSE AND PROSPECTS OF DEVELOPMENT IN UKRAINE

2020 ◽  
pp. 25-38
Author(s):  
Irina Mordous
Keyword(s):  
Decisive Role ◽  
Subject Field ◽  
National Education ◽  
Progressive Development ◽  
Separate Area ◽  
Economic Transformations ◽  
The Difference ◽  
The Individual ◽  
Political Economic

The development of modern civilization attests to its decisive role in the progressive development of institutions. They identified the difference between Western civilization and the rest of the world. Confirmation of the institutional advantages of the West was its early industrialization. The genesis and formation of institutionalism in its ideological and conceptualmethodological orientation occurs as a process alternative to neoclassic in the context of world heterodoxia, which quickly spread in social science. Highlighting institutional education as a separate area of sociocultural activity is determined by the factor of differentiation of institutional theory as a whole. A feature of institutional education is its orientation toward the individual and his/her transformation into a personality. The content of institutional education is revealed through the analysis of the institution, which includes a set of established customs, traditions, ways of thinking, behavioral stereotypes of individuals and social groups. The dynamics of socio-political, economic transformations in Ukraine requires a review of the foundations of national education and determination of the prospects for its development in the 21st century in the context of institutionalism.

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