Word Finder - permeability

definition

The property of being permeable

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The rate of flow of a fluid through a porous material

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A measure of the ability of a rock to transmit fluids (such as oil or water)

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A quantitative measure of the degree of magnetization of a material in the presence of an applied magnetic field (measured in newtons per ampere squared in SI units).

The first exact experiments demonstrating the changes which occur in the permeability of iron,, 3 Phil.

In regard to water, all soils have two actions - namely, permeability and absorbability.

So far, the best results have been attained with aluminium, and the permeability was greatest when the percentages of manganese and aluminium were approximately proportional to the atomic weights of the two metals.

The values of the permeability corresponding to the highest and lowest temperatures are given in the following table.

The silicon-iron had, in fields up to about Io, a greater permeability than a sample of the best Swedish charcoal-iron, and its hysteresisloss for max.

Equations (33) and (34) show that when, as is generally the case with ferromagnetic substances, the value of is considerable, the resultant magnetic force is only a small fraction of the external force, while the numerical value of the induction is approximately three times that of the external force, and nearly independent of the permeability.

Low hysteresis is the chief requisite for iron which is to be used for transformer cores, and it does not necessarily accompany high permeability.

This was followed at the close of the same year by the discovery of the magnetic condition of all matter, a discovery which initiated a prolonged and fruitful study of paramagnetic and diamagnetic phenomena, including magnecrystallic action and " magnetic conducting power," now known as permeability.

Owing, however, to the very variable permeability of the strata, the tributaries of the Thames, when separately gauged in dry seasons, yield the most divergent results.

Imagine for a moment that the sand grains were by any means rendered immobile without change in the permeability of their interspaces; we could then dispense with the iron or brickwork lining of the well; but as there would still be no cracks or fissures to extend the area of percolating water exposed to the open well, the yield would be very small.

The areas of research are listed below Increased epithelial permeability in airways is known to be associated with the hyperactivity of the asthmatic airway.

They show varying permeability to a range of monovalent and divalent cations.

This type of arrangement is found in the kidney glomerulus, where the basal lamina acts as a permeability barrier or sieve.

The permeability of the tomato epidermal peels to the exogenous chemicals was tested and found to be adequate.

New sensors will include a cone penetrometer (CPT ), permeability probe and a resistivity probe.

Nystatin however, binds to ergosterol and alters membrane permeability and hence allows leakage of intracellular contents.

Exudate - the fluid plasma which leaks out of blood vessels due to an increase in capillary permeability.

These molecules induce smooth muscle contraction and enhance vascular permeability.

To identify the effect of IL-6 on intestinal permeability.

Ni Resist can exhibit low levels of magnetic permeability i.e. they can be non magnetic.

The models include trapping of gas and reduction of water relative permeability in the presence of trapped gas.

Mr Shattock believes that low levels of IAG may be caused by increased gut permeability resulting from the presence of measles virus.

Also, water vapor permeability is important for certain products.

It all depends on the oxygen permeability of plastic water bottles.

For example, to establish the fracture history or fault zone permeability.

These artificial composites exhibit the unusual left-handedness, i.e. simultaneously negative permittivity and negative permeability.

In basement reservoirs matrix porosity is effectively close to zero and most of the storage capacity and permeability is due to fractures.

Ewing has also studied the effect of vibration in conferring upon iron an apparent or spurious permeability of high value; this effort also is most conspicuous when the magnetizing force is weak.

The members of the first class influence the endothelial plates of the capillaries injuriously, inducing thereby increased permeability; those of the second class (sugar, &c.), on injection into the blood, attract water from the tissues and cause a condition of hydraemic plethora with increased capillary pressure.

High vapor permeability allows any moisture collected by the sheets to dry out naturally.

Some patients also suffer loss of protein from the body that often results in low blood levels of albumin and total protein (protein-losing enteropathy) due to increased GI tract permeability.

Its physical properties, permeability by water, extensibility and elasticity, receive their interpretation in the needs of the latter.

The peculiarity of the protoplasm in almost every cell is that it is especially active in the regulation of its permeability by water.

The response to the stimulus takes the form of increasing the permeability of particular cells of the growing structures, and so modifying the degree of the turgidity that is the precursor of growth in them.

The extent of the area affected and of the variation in the turgor depends upon many circumstances, but we have no doubt that in the process of modifying its own permeability by some molecular change we have the counterpart of muscular contractibility.

Thus the scenery of a limestone country depends on the solubility and permeability of the rocks, leading to the typical Karst-formations of caverns, swallowholes and underground stream courses, with the contingent phenomena of dry valleys and natural bridges.

The permeability of most material substances differs very slightly from unity, being a little greater than I in paramagnetic and a little less in diamagnetic substances.

In the case of the ferromagnetic metals and some of their alloys and compounds, the permeability has generally a much higher value.

No substance has yet been discovered having a negative susceptibility sufficiently great to render the permeability (= I +471K) negative.

The total magnetic induction or flux corresponds to the current of electricity (practically measured in amperes); the induction or flux density B to the density of the current (number of amperes to the square centimetre of section); the magnetic permeability to the specific electric conductivity; and the line integral of the magnetic force, sometimes called the magnetomotive force, to the electro-motive force in the circuit.

If a hollow sphere 7 of which the outer radius is R and the inner radius r is placed in a uniform field Ho, the field inside will also be uniform and in the same direction as Ho, and its value will be approximately 3 i - R 3 For a cylinder placed with its axis at right angles to the lines of force, 2 = Ho (41) 2 +4(-2)(i - R2) These expressions show that the thicker the screen and the greater its permeability o, the more effectual will be the shielding action.

The presence of ordinary impurities usually tends to diminish the permeability, though, as will appear later, the addition of small quantities of certain other substances is sometimes advantageous.

When it is mechanically hardened by hammering, rolling or wire-drawing its permeability may be greatly diminished, especially under a moderate magnetizing force.

An experiment by Ewing showed that by the operation of stretching an annealed iron wire beyond the limits of elasticity the permeability under a magnetizing force of about 3 units was reduced by as much as 75%.

The permeability of a soft iron wire, which was tapped while subjected to a very small magnetizing force, rose to the enormous value of about 80,000 (Magnetic Induction, § 85).

An excellent instrument of the class is Ewing's permeability bridge.

If, however, the permeability of the test rod differs from that of the standard, the number of lines of induction flowing in opposite directions through the two rods will differ, and the excess will flow from one yoke to the other, partly through the air, and partly along the path provided by the bent bars, deflecting the compass needle.

Steel behaves in a similar manner, but the maximum permeability is not so high as in iron, and the fall, when the critical point is approached, is less abrupt.

Specimens of curves showing the relation of induction to magnetic field at various temperatures, and of permeability to temperature with fields of different intensities, are given in figs.

They showed that the permeability of this sample of iron was considerably diminished at the lower temperature.