Layer Of Granular Material Research Articles

Criteria for geotextile filters in clayey soils

In filtration processes, the action of protective filters involves two well-known interrelated aspects: to selectively retain the particles transported by water flow and to facilitate stabilization of soil, by creating a stable natural filter at the soil-filter interface. The paper analyses the distinct approach that should be adopted in the design concept of geotextile protective filters applicable to cohesive and non-cohesive soils. Accepting that the soil structure and grading are the determining factors in the formation of a natural filter at the soil-filter interface, the conditions offered by cohesive soils seem even less favourable than those offered by non-cohesive soils. Laboratory tests, as well as the tests carried out on physical models, have revealed that the filtering capability of geotextile filters on clayey soils improves when a thin layer of granular material is applied in the contact area. In addition to the increased operational advantages obtained in the filtering process, this procedure ensures protection of geotextile filters against clogging during the construction stage.

Corneal stromal wound healing in rabbits after 193-nm excimer laser surface ablation.

An argon fluoride excimer laser (193 nm) with a moving slit delivery system was used to perform anterior myopic keratomileusis in both eyes of 24 New Zealand white rabbits. Rabbits were killed immediately after ablation and at intervals up to 100 days. By slit-lamp microscopy, four rabbits at day 100 exhibited four clear corneas and four corneas had central, spotty, subepithelial haze. Light and electron microscopy documented corneal healing. In the early stages a transient acellular zone in the anterior stroma appeared over a period of three weeks, followed by an increased number of fibrocytes. In the corneas with opacification, focal areas of 20-microns-thick subepithelial scarring were present. An unexpected finding was transient damage to posterior stromal keratocytes and endothelial cells. The endothelium produced a layer of granular material that migrated anteriorly across Descemet's membrane. Immunochemistry at day 6 showed a marked staining for collagen IV, proteoglycans, fibronectin, and laminin.

Isothermal axisymmetric flow of an incompressible fluid in radial contact apparatus

A method is proposed for the calculation of the axisymmetric flow of an incompressible fluid in a radial apparatus with a nonmoving layer of granular material. An engineering method is developed to evaluate the degree of flow nonuniformity in equipment of this type, thus making it possible operationally to choose among structural solutions in the design of this equipment.

A review of fixed phagocytic and pinocytotic cells of decapod crustaceans, with remarks on hemocytes

Clearance of foreign materials from the hemocoel of decapod crustaceans involves several distinct kinds of cells. Proteins, and possibly viruses below 30 nm diameter, are known to be removed by the branchialpodocytes, which are specialized pinocytotic nephrocytes located in the gills. These cells, and podocytes of the antennal gland (excretory organ) which may also be of importance in clearance, are similar to podocytes of Bowman's capsule of the vertebrate kidney. Phagocytic clearance of particulate material (with possible exception of the small viruses) is accomplished by three kinds of cells, one free and the other two fixed to tissues facing hemal spaces. The hemocytes, free cells suspended in the hemolymph, are the most abundant and generalized of these phagocytic cells. Phagocyticreservecells are applied to myofibers in the heart of penaeid and palaemonid shrimp, and probably the same as reserve cells found throughout the hemocoel of all decapods. They are minimally involved in clearance of injected carbon and carmine, but are not known to phagocytize naturally occurring particles such as bacteria or viruses. The fixedphagocytes are very important in the clearance of some substances. They are located on the exterior surfaces of arterioles in hemal spaces of the hepatopancreas. They are highly specialized cells designed to sequester large amounts of various types of particulate matter, not only through phagocytosis but by trapping and retaining vast numbers of particles within a net- or sievelike layer of granular material which surrounds the free surface of the fixed phagocyte. Derivation, morphology, development, and function of the above cell types are described and discussed.

Ultrastructure of the colon of Locusta migratoria.

The ultrastructure of the colon of Locusta migratoria is described. The colon is lined by a thick cuticle that, for the most part, adheres to the underlying epithelium. The cuboid epithelial cells are characterized by moderate invaginations of the apical and, to a lesser extent, basal plasma membranes; the lateral plasma membranes are relatively flat. The bulk of the mitochondria are located in the apical region of the cell and are not particularly associated with any of the plasma membranes. The basal region of the cells contains much rough endoplasmic reticulum, glycogenlike granules, and a predominance of spherical, electron-dense bodies of various sizes. Where muscle fibers make contact with the epithelium, the cells are much reduced; the cytoplasm is usually less electron-dense, and, typically, the nucleus has a thick layer of granular material associated with the inner nuclear membrane. The apical and basal plasma membranes of the reduced epithelial cells contain numerous hemidesmosomes. The apical hemidesmosomes occur in pairs around an extracellular space that contains electron-opaque material. The latter forms tonofibrillae that extend into the endocuticle. Bundles of microtubules are associated with the hemidesmosomes. The tubules traverse the cell from the apical to the basal region. The possible significance of these findings is discussed.

Ultrastructure of induced iprodione-insensitive isolates of Botrytis cinerea

Transmission-electron microscopy has shown that strains of B. cinerea insensitive to iprodione accumulate a layer of granular material in the cytoplasm around the circumference of hyphae, adjacent to the plasmalemma, when grown in iprodione-amended agar. A role for the material in insensitivity to iprodione is suggested.

Transmission and scanning electron microscope studies on the surface coat of the oral mucosa in the rat.

Following treatment with either Ruthenium red or Alcian blue, the exposed surface of oral mucosa from the rat was examined in either the scanning or transmission electron microscope. The oral surfaces of half the specimens were vigorously washed prior to treatment with Ruthenium red or Alcian blue. The appearance of all scanning electron microscope specimens was compatible with that seen in the transmission electron microscope. All the washed Ruthenium red and Alcian blue and the unwashed Ruthenium red specimens had a continuous layer of granular material over the oral surface of the epithelial cells. A thick precipitate of saliva covered the unwashed Alcian blue specimens. The probable reasons for the precipitation of saliva by the Alcian blue are discussed. The possible nature, origins and functions of the Ruthenium red and Alcian blue positive surface covering are discussed.

Nonstationary heating of a fixed granular mass

The reduction of the system of heat-transfer equations in phases of a disperse medium to a single equation is considered. The problem of heating a layer of granular material by a stream of hot fluid is investigated as an illustration.

Circulation of the solid phase through a vertical gas jet injected into a layer of granular material

A method is developed for determining the mass of particles circulating through a vertical gas jet. On the basis of experimental data dependences are obtained for determining the circulation of particles and the velocities of their motion in the jet.

A new and unusual eimerian (protozoa: Eimeriidae) from the liver of the Gulf killifish, Fundulus grandis.

Oocysts and sporocysts of Eimeria funduli sp. n. are described from the Gulf killifish, Fundulus grandis, on the basis of light microscopy, transmission and scanning electron miscroscopy, and location in the liver of infected hosts. The spherical sporulated oocysts of E. funduli isolated from liver tissue measure 20-31 (25) micrometer across with ovoid sporocysts 9-11 X 5-7 (10 X 6) micrometer. A micropyle, polar granule, and oocyst residuum are absent, but sporocysts have Stieda and substieda bodies, a few residual granules, and 10-25 (15) unique projecting structures with expanded distal portions that we term "sporopodia". Sporopodia 1-3 (2) micrometer high support a transparent membrane that completely surrounds the sporocyst. Sporozoites have one large posterior refractile body. Ultrastructurally, the oocyst wall consists of two thin layers of granular material: an electron-dense outer layer with a rough external surface and an electron-lucent inner one of approximately equal thickness. One or two unit membranes line the inner surface of the inner layer. Each layer is 40-60 (55) nm thick. The sporocyst wall, 78-130 (110) nm thick, consists of an electron-lucent material with the outer surface being more electron dense and giving rise to osmiophilic sporopodia; closely associated with these and the outer surface are one or two unit membranes. A thin osmiophilic layer of fine granular material lines the inner surface.

Ultrastructural changes in spermatozoa of the brush-tailed possum, Trichosurus vulpecula (Marsupialia), during epididymal transit. Part I: The flagellum.

During epididymal transit, a fibre network and an array of vesicles develop in the posterior two-thirds of the midpiece in sperm of the Brush-tailed possum, Trichosurus vulpecula. The fibre network is developed by the time the sperm reach the corpus epididymidis, and is composed of evenly spaced, helically arranged fibres lying immediately beneath the plasma membrane. The angle of these fibrous helices is always counter to that of the underlying mitochondrial helix. Separating the fibre network from the mitochondria is a layer of granular material which develops at the same time, and over the same length of the midpiece as the fibre network. A somewhat tenuous fibre network is found between the fibrous sheath and plasma membrane in the anterior principal piece of sperm from all regions of the epididymis. The array of vesicles is developed by the time sperm reach the cauda epididymidis. The vesicles resemble pinocytotic vesicles; some appear as invaginations of the plasma membrane, and are open to the medium surrounding the spermatozoon by a narrow neck, while others are entirely enclosed within the spermatozoon, and lie at varying distances between the plasma membrane and the layer of granular material.

Curling Deformations and Stresses of Insulated Rigid Pavements

The problems associated with freezing and thawing of the subgrade soil underneath highway and airfield pavements in countries with cold winters like Canada are well known. In the southern parts of Canada, the subgrade can be protected from freezing by a thick layer of granular material or a thin insulating layer. In northern regions, layers of granular materials or insulation can maintain the subgrade in a frozen condition.Previous studies have shown that extruded polystyrene foam is effective as an insulating material. However, the effect of this material on the physical behavior of pavements has not previously been investigated.To study the effect of a thin insulating layer on the curling deformation and thermal properties of rigid pavements two concrete slabs were cast in the field. One slab was laid over a 1½ in (4 cm) thick layer of styrofoam, while the second slab was cast over a 1½ in. (4 cm) thick layer of sand without insulation. A 10 in. (25 cm) subbase layer of compacted gravel was used underneath both slabs.Both slabs were instrumented from surface through foundation to determine the temperature distribution and to establish the curling behavior of the slabs. Periodic readings were taken during one warm and one cold weather period. The results derived from these readings have indicated that insulation reduces curling deformation of pavement slabs and does not significantly effect temperature gradients across their thickness.

A scanning electron microscopic study of the luteo‐follicular complex. II. Events leading to ovulation

Morphological changes on the ovarian surface of different mammals both before and during ovulation have been examined by scanning electron microscopy. Preovulatory follicles were blisterlike structures that protruded markedly from the ovarian surface. Basal areas of preovulatory follicles were covered with polyhedral cells containing numerous microvilli, whereas on the lateral surfaces, superficial cells were elongated and possessed few microvilli. At the apex of the follicle, cells were very flattened and possessed few microvilli, which were present only in regions of intercellular contact. In some apical areas, cells appeared to be degenerating, whereas in other regions, groups of cells had "sloughed off." In addition, a fluidlike material was observed to exude from intercellular spaces of the superficial epithelium and to cover some apical cells. By transmission electron microscopy, the same fluidlike material was observed to (1) infiltrate the connective tissue of the tunica albuginea, (2) accumulate under the basal lamina, and (3) distend intercellular spaces of the superficial epithelium. Just prior to ovulation, large, irregular areas of the apex were ruptured and the oocyte, covered with a large amount of fluid, appeared to emerge from the follicle. At ovulation, the oocyte was not completely covered with follicle cells and the zona pellucida was clearly evident. The surface of the zona was quite irregular and contained numerous infoldings, channels and crypts. Follicle cells had polyhedral or star shapes and possessed large cytoplasmic evaginations that obliquely penetrated the zona. Both the zona pellucida and corona cells were covered with a fine layer of granular material. The SEM results and parallel TEM observations suggest that a local increase of fluids (edema) may be an important factor in the final decomposition of the distended and weakened apex of the preovulatory follicle. In addition, the participation of follicle cells, smooth muscle cells and the oviduct in the escape of the oocyte from the ruptured follicle is discussed.

Ultrastructural study of the neural fat-body system in the cockroach Periplaneta americana

The neural fat-body system of the ventral nerve cord in the cockroach Periplaneta americana was studied with the light and electron microscopes. This adipose tissue surrounds the connectives and extends over the ganglia. The adipose cells typically contain numerous extremely large lipid inclusions, pleomorphic lysosomes, and tightly packed glycogen granules. The neural lamella consists of a thick inner layer rich in collagen fibers and a thin outer layer of granular material. At points where the fat body is attenuated, this granular layer is split and the outer lamina is reflected superficially to ensheath and apparently to anchor the fat body.

The ignition of a thin layer of explosive by impact

The behaviour of thin layers of solid materials under drop-weight impact is studied with the aid of high-speed photographic and pressure-measuring techniques. Photographic sequences taken with a high-speed framing camera show that explosive materials suffer large-scale deformation before initiation of explosion. The sample may undergo plastic flow in bulk, show evidence of partial fusion, and even (with PETN) melt completely. There is also evidence of Munroe jetting and instability of flow of material at the anvil/layer interfaces. The flow speed of the sample during these processes is considerable and may reach 300 m/s. When ignition of the layer occurs it does so at a small number of local hot spots, following which rapid combustion develops at speeds of 200-700 m/s. Strain-gauge measurements show that the pressures attained during drop-weight impact are typically 0.5-1 GPa (5–10 kbar) and the duration of impact 300–500 μs. In the course of impact of a thin layer of granular material a sharp pressure drop may occur, frequently from several hundred MPa down to zero. With an explosive layer, ignition occurs immediately following the instant of the pressure drop. The sudden fall in pressure is due to mechanical failure of the sample, and correlation of the two experiments shows that this is the cause of the very high flow speeds attained during impact. On the basis of these results a possible mechanism of ignition is suggested.

Intracisternal A-type particles in murine neoplasias with and without paraprotein production.

Immature plasma cell neoplasias induced in BALB/c mice with subcellular leukaemic extracts were investigated with the electron microscope for virus‐like particles. A‐type particles located in the cisternae of the endoplasmic reticulum and in the perinuclear space were the only virus‐like particles observed. The A‐type particles average 70 mü in transverse diameter. They display two electron‐dense shells around a 30 mü wide electron‐translucent core. In most instances the particle surface is covered by a layer of granular material with moderate electron‐density. A few electron‐dense granules are noted in the core of some A‐type particles. The A‐type particles apparently are formed by inward budding from the membrane of the endoplasmic reticulum and occur whether or not the neoplasm produces paraprotein. The findings are discussed in light of our knowledge on leukaemic lesions in mice with plasma cell neoplasia.

NEMATOCYSTS OF THE SEA ANEMONEMETRIDIUM

Six types of nematocysts and their nematocytes in tentacles and acontia of the sea anemone Metridium senile fimbriatum were studied by electron microscopy. Microbasic b-mastigophores, microbasic amastigophores, and basitrichs have one fundamental feature in common: a straight, complexly-folded shaft with dense spines pointing apically. An additional resemblance between a b-mastigophore and a basitrich is the possession of a long, narrow, coiled thread bearing spines. An amastigophore is characterized by a short, looped, unspined thread and a cup-shaped granular matrix. Atrich and holotrich nematocysts have a coiled, spined tube of uniform diameter which lies in an evenly granular matrix filling the entire capsule. The above five nematocysts have three flaps at the apex of the capsule which open upon discharge, and each nematocyte possesses a flagellum with which is associated one or two centrioles and a striated rootlet. The long rootlet of the b-mastigophorebearing nematocyte passes through a circular band of fibrils surrounding the neck region of the capsule, and the short rootlet of the atrich lies in a dense fibrous sheath surrounding all but the apex of the capsule. The spirocyst differs from the other nematocysts in having a thin, ridged, singlewalled capsule; an inverted tube containing bundles of tubules; an apical disk covered only by a thin layer of granular material and the nematocyst membrane; and the absence of a flagellum in its nematocyte. Theories of excitation and mechanism of discharge of nematocysts and the function of spirocysts are discussed in the light of this and other recent studies of the fine structure of nematocysts. Special attention is drawn to the probable role of the folds in the walls of shaft and thread in increasing the length of the tube upon discharge.

FINE STRUCTURE AND MORPHOGENIC MOVEMENTS IN THE GASTRULA OF THE TREEFROG, HYLA REGILLA.

The blastoporal groove of the early gastrula of the treefrog, Hyla regilla, was examined with the electron microscope. The innermost extension of the groove is lined with invaginating flask- and wedge-shaped cells of entoderm and mesoderm. The distal surfaces of these cells bear microvilli which are underlain with an electron-opaque layer composed of fine granular material and fibrils. The dense layer and masses of vesicles proximal to it fill the necks of the cells. In flask cells bordering the forming archenteron the vesicles are replaced by large vacuoles surrounded by layers of membranes. The cells lining the groove are tightly joined at their distal ends in the region of the dense layer. Proximally, the cell bodies are separated by wide intercellular spaces. The cell body, which is migrating toward the interior of the gastrula, contains the nucleus plus other organalles and inclusions common to amphibian gastrular cells. A dense layer of granular material, vesicles, and membranes lies beneath the surface of the cell body and extends into pseudopodium-like processes and surface undulations which cross the intercellular spaces. A special mesodermal cell observed in the dorsal lining of the groove is smaller and denser than the surrounding presumptive chordamesodermal cells. A long finger of cytoplasm, filled with a dense layer, vesicles and membranes, extends from its distal surface along the edge of the groove, ending in a tight interlocking with another mesodermal cell. Some correlations between fine structure and the mechanics of gastrulation are discussed, and a theory of invagination is proposed, based on contraction and expansion of the dense layer and the tight junctions at distal cell surfaces.

On the mechanical testing of thermoelectric modules

Computer simulation predicts that horizontal size segregation can be obtained in a vertically vibrated layer of granular material. This behavior is a consequence of two distinct phenomena that are unique to excited granular media: vibration which causes the large grains to rise to the top of the layer, and a vibrating base with a sawtooth surface profile which can produce stratified flows in opposite directions at different heights within the layer. The result of combining these effects is that large and small grains are horizontally driven in opposite directions.

Single-phase flow of fluids through a layer of granular material

Single-phase flow of fluids through a layer of granular material