Size Of Capillaries Research Articles

Condensation-evaporation cycles in pore and capillary systems according to the Kelvin model

A useful analysis of the simplest pore and capillary systems is conducted in order to pinpoint when adsorption and desorption of water vapor is a reversible process without a hysteresis loop and when it is irreversible and triggered by critical values of relative humidity (RH). On the basis of the Kelvin formula, some critical values of RH have been found to be a function of the size and arrangement of porosities and capillaries. Besides the hysteresis, the geometry of the pore and capillary system may cause air pockets to be entrapped within the body, so that in many cavities, as in the well known ‘ink bottle’, the condensation in an external cavity may prevent condensation in the more internal ones.

Microstructure and water sorption mechanism of coconut pith

AbstractThe water sorption isotherm of coconut pith is studied in order to get an insight into the nature of the sorption process. The surface area available for adsorption, heat of adsorption and approximate size of possible capillaries are computed from the isotherm. A considerable hysteresis effect is observed. The cell structure of coconut pith is studied using an optical microscope. On the basis of the computations and microscopic observations, the similarity of the sorption process with that of woody materials is established.

Quantitative Study of Optic Nerve Head Capillaries in Experimental Optic Disk Pallor

We obtained quantitative measurements of capillary numbers, areas, and diameters in atrophic (pale) and normal primate optic nerve heads. The number of capillaries per square millimeter in pale optic disks was not significantly different from that in normal optic disks. Because the loss of all nerve fibers leads to a 50% decrease in nerve head substance, capillaries must atrophy to maintain a constant relationship between capillary number and tissue volume. The mean size of individual capillaries in atrophic nerve heads was smaller than normal, leading to a decrease of more than 27% in the percentage of tissue volume occupied by capillaries. When this decrease in capillary volume was mimicked in the normal optic disk by reducing the hematocrit value, optic disk pallor did not result. Hence, the development of optic disk pallor appears to be the result of thinning of the neural tissue of the rim of the optic disk and the consequent change in tissue composition and optical transparency, rather than of a loss of optic disk capillaries.

The ultrastructure of human fibrosing alveolitis

This report describes the ultrastructural findings in 37 patients who underwent open lung biopsy which yielded diagnoses of fibrosing alveolitis. A spectrum of lesions are categorized for the capillary endothelium and its basement membrane, the interstitial space and its fibrocellular components, and the alveolar epithelium and its basement membrane. The findings typify the different pulmonary cellular reactions to injury. Evidence for cellular regeneration and death in both epithelial and endothelial cell populations include atypical epithelial cell proliferation, capillary basement membrane multilamination, decrease in capillary lumen size and prominent pericytic ensheathment of pulmonary capillaries. Within the interstitium of the lung, proliferation of collagen and elastic fibers are documented, but in addition, abundant myofibroblasts and smooth muscle cells are present. No ultrastructural evidence of immune complex deposition was found in this study. The morphologic findings of fibrosing alveolitis further support the widespread concept that the lung responds to various injuries in a similar manner and undergoes a common reparative response regardless of etiology.

Orientation Preference In The Growth Of Alkali Metal Single Crystals By Using Bridgeman Technique

The single crystals of alkali metals (Na, K, Li, Rb and Cs) have been obtained in varying sizes of glass capillaries by using Bridgeman technigue without employing a seed. The cubic crystals grown this way are theoretically [3] expected to have random orientations. We checked the theory by determining the distribution of orientations for each metal and found that there is no obvious preferred orientation about any crys- tallographic axis. analysİs and Binomial distribution have been used as mathematical tools in experimental varification of the theory of random orientations and our data have been found to support it to a considerable extent.

Skeletal Muscle Capillaries in Nondiabetics

To evaluate the variations of capillary calibers and those of basal lamina (BL), pericytes, endothelium, and lumen within a sample of skeletal muscle and among samples from different anatomic sites, areas occupied by total capillary cross sections, by the lumen, endothelium, pericytes, and BL were measured on electron micrographs. Twenty capillary cross sections from each of the 41 specimens of skeletal muscle from 23 nondiabetic males were used. For all parameters, a marked variation was noted within each specimen, between specimens from identical sites of different individuals, and between different anatomic sites of the same individuals. In general, the capillaries are largest in the lower leg and foot muscles; the lumen is smallest at the levels of mid-thigh and lower leg; the capillaries of the lower extremity have a greater investment of BL, endothelium, and pericytes than the capillaries of the trunk and hand muscles. The areas occupied by endothelial cytoplasm, pericyte cytoplasm, and by BL are larger in bigger capillaries apparently owing to greater circumference. In addition, the capillaries of the leg, particularly those of the lower leg, have an absolutely greater investment of BL than capillaries from proximal sites. Reasons for these regional differences in the overall size of capillaries and in the investment of BL are not known.

Epoxy polymers. III. Factors affecting the cure

AbstractThe rate of cure of epoxy polymers appears to be diffusion‐controlled, and after gelation is dependent upon the capillary dimensions in a floccular matrix. The floccule dimensions and packing determine the size of the interfloccular capillaries and are inversely related to the cure temperature. The degree of cure is inversely related to the pregelation cure temperature (thermal history, including preheat) and directly related to the total cure time.

Vascular zoning in the adrenal cortex of the normal and hypophysectomized rat with observations on the distribution of lipids.

SUMMARY Within the adrenocortical capillary pattern demonstrated by intravitam injection of Indian ink, a zoning into three concentric areas is apparent: (1) an outer injected zone comprising the capillaries of the z. glomerulosa; (2) an intermediate z. lucida of poorly-filled capillaries, corresponding to the 'z. intermedia' (see text, p. 134) plus a variable width of the outer z. fasciculata; (3) an inner injected zone comprising capillaries in the z. reticularis and inner z. fasciculata. A close correspondence in extent was found by various measurements between the z. glomerulosa, the outer injected zone and the outer sudanophil zone of lipid-stained preparations. A zone described as the 'z. lucida' (see text, p. 138) is more extensive than the sudanophobic zone. Following hypophysectomy: (a) The z. intermedia and the sudanophobic zone show a linear increase in extent with time. (b) The z. glomerulosa increases in width up to the 5th week, but thereafter decreases to reach a steady state. (c) Shrinkage, principally of the inner two cortical cellular zones, results in a closer approximation and narrowing of capillaries. With time there is a general reduction in the number and size of cortical capillaries throughout the cortex. (d) Normal vascular zoning in the cortex is apparent for about 3 weeks.

AN ESTIMATION OF THE VOLUME OF WATER MADE AVAILABLE BY ROOT EXTENSION

Modern views on plant-soil moisture relations stress the importance of continuous elongation of roots into new regions of the soil as an important factor in making water available to plants. It was long believed that as roots absorb the available water from the soil particles with which they are in direct contact more water is made available by capillary movement from more distant soil particles. Investigations conducted during the past 15 years indicate that this belief is not true, capillary movement of water toward the roots being so slow under average field conditions that it is of negligible importance. A brief discussion of soil-water relations will show why capillary movement is relatively unimportant. If a limited amount of water is applied to a large volume of soil a part of the soil will be wetted uniformly while the remainder is unaffected. This situation is often observed after a shower which has wetted the upper three or four inches of soil, leaving a sharp line of demarcation between the moist soil and the dry soil beneath. The movement of water in a dry soil can occur only from larger to smaller capillaries. As Puri (6) has indicated, water will move from a wet soil to a dry soil only if the dry soil contains some capillaries smaller than the largest ones in the wet soil which are full of water. Water movement from wet soil to dry soil continues until contact is broken between the smaller capillaries of the dry soil which are responsible for the movement. When continuity of the liquid phase is thus broken visible movement of water ceases. The swelling of certain types of soil colloids when wetted is also of importance in inhibiting water movement by reducing the size of capillaries to a diameter so small that water molecules cannot readily pass. The amount of water held by capillarity in the soil after it has been uniformly distributed by gravitational and capillary forces is usually termed the field capacity (Veihmeyer and Hendrickson, 10). Under field conditions well drained soils are usually assumed to be at their field capacity a day or two after being wetted by rain or irrigation. Shantz (7) stated that on theoretical grounds the capillary movement of water from moister to drier regions in soils at or below their field capacity would be very slow and this was experimentally verified by Keen (3) and Veihmeyer and Hendrickson (9). According to Puri (6) when soil moisture is restricted to capillaries formed by particles having a diameter of 0.001 mm. or smaller relatively little water is available to plants. He considers that particles coarser than clay are mainly responsible for retaining moisture available to plants, whereas clay aids in the conservation of