Irregular Layer Research Articles

Electromagnetic induction in an irregular layer overlying the earth. The 3rd paper: A conducting layer having a plane top and an undulatory bottom.

Electromagnetic induction by a uniform magnetic field in a conducting layer having a plane top and an undulatory bottom is studied. A source field parallel to the surface is assumed. The apparent resistivity (ρa) vs period of magnetic variation (T) relation is obtained at various points over the top surface by means of conventional magneto-telluric technique. The phase vs T relation is also obtained from the electric and magnetic fields studied.It turns out that the ρa-T relation and the phase-T relation are the same as those of the two-layer model developed by Cagniard provided a small amplitude of the undulatory bottom is assumed. Also these relations are independent of the observation point. When the amplitude of undulation is large, however, the ρa-T and the phase-T relations are modified in such a way that an apparently low-resistive zone lies at the prescribed depth of undulatory boundary between the two layers of the original model, the conclusion being on the three-layer MT analysis due to Cagniard.

Unusual Folding and Rolling of Glacio-Lacustrine Sediments, Upper Fraser Canyon, British Columbia: ABSTRACT

Folding and rolling of graded but unconsolidated sediments by at least 720/sup 0/ produced a structure resembling a large Swiss roll about 6 ft wide and 4 ft high. The sediments were initially horizontal and well sorted, grading from coarse sands to fine silts. About 50 ft away, at the same level, the sediments include irregular layers of poorly sorted, ice-rafted pebbles and boulders. The sequence is unconformably overlain by till. The axis of folding appears to be parallel to the eastern wall of the Fraser Canyon. The outcrop is in the Stevens Pit (sand and gravel) immediately east of the Trans-Canada Highway, 2 mi south of Lytton, B.C., at an elevation of 1000 ft, approximately 600 ft above the present level of the Fraser River. The sands and silts accumulated in a lake adjacent to the east margin of a stagnant and relatively small glacier occupying the upper part of the Frazer Canyon. Partial or complete melting of small icebergs caused deposition of coarser material. A subsequent cooling trend led to an advance of the glacier, an advance which at this location caused some of the adjacent and by now frozen sediments to be rolled up like an oldmore » carpet. Further advance of the glacier caused it to override and thus preserve the deformed sequence.« less

Differentiation of the embryonic disc, amnion, and yolk sac in the rhesus monkey

The inner cell mass of the blastocyst has differentiated into epiblast and hypoblast (primitive endoderm) prior to implantation. Since endoderm cells extend beyond the epiblast, it can be considered that both parietal and visceral endoderm are present. At implantation, epiblast cells begin to show marked evidence of polarity. They form a spherical aggregate with their basal ends toward the basal lamina and apical ends toward the interior. The potential for an internal space is formed by this change in polarity of the cells. No cytological evidence of separation of those cells that will form amniotic epithelium from the rest of the epiblast is seen until a cavity begins to form. The amniotic epithelium is originally contiguous with overlying cytotrophoblast, and a diverticulum remains in this position during early development. Epiblast forms a pseudostratified columnar epithelium, but dividing cells are situated toward the amniotic cavity rather than basally. The first evidence of a trilaminar disc occurs when a strand of cells contiguous with epiblast is found extending toward visceral endoderm. These presumptive mesoderm cells are undifferentiated, whereas extraembryonic mesoderm cells are already a distinct population forming extracellular materials. After implantation, visceral endoderm cells proliferate forming an irregular layer one to three cells thick. Visceral endoderm cells have smooth apical surfaces, but very irregular basal surfaces, and no basal lamina. At the margins of the disc, visceral endoderm is continuous with parietal endoderm and reflects back over the apices of the marginal visceral endoderm cells. This sacculation by visceral endoderm cells precedes pinching off of the secondary yolk sac from the remaining primary yolk sac.

High‐Speed Motion Pictures of Nearly Steady, Uniform, Two‐Dimensional, Inertial Flows of Granular Material

Nearly steady, uniform, essentially two‐dimensional (except for grain spins) flows of 6‐mm‐diameter cellulose‐acetate spheres were generated in an inclined glass‐walled channel 3.7 m long and just 6.25 mm wide. The bed consisted of spheres like those in the flows, which were glued with random spacing to an aluminum bar. Filming was done with a 16‐mm camera at rates from 40 to 120 times normal. The flows were almost entirely inertial. They typically consist of three zones: a basal grain‐layer gliding zone, in which irregular layers of grains slide over one another in card‐deck shear fashion and free paths are short; a middle chaotic zone, in which grain motions are highly random and homogeneous, as in a dense gas, and free paths are about a grain diameter; and a superincumbent saltational zone, in which grain motions are also gas‐like but free paths are long and noticeably curved. Steepening the inclination or reducing the discharge can eliminate the grain‐layer gliding and chaotic zones entirely, whereas the converse can diminish markedly the saltational zone. Translational energy loss in impacts is approximately normally distributed about a mean of 27% and is independent of relative velocity of impact. Profiles of mean downstream velocity, granular temperature (mean‐square fluctuation velocity), and bulk density in a flow almost wholly saltational show slip at the bed of 20% of the mean flow velocity, temperature a maximum midway in the flow, and density decreasing almost linearly with distance from the bed.

The role of magmatic reaction, diffusion and annealing in the evolution of coronitic microstructure in troctolitic gabbro from Risör, Norway

AbstractCoronas of symplectic pargasite [XMg = 68, XCa = 69, XSi = 68] + spinel [SP45] and orthopyroxene [EN70] separate cumulus plagioclase [AN64] and olivine [FO64] in troctolitic gabbro from Risör, Norway. Coronas with a primary microstructure characterized by low-angle grain boundaries have the mineral assemblage layer sequence,PLAGIOCLASE : PARGASITE + SPINEL : ORTHOPYROXENE + SPINEL : ORTHOPYROXENE : OLIVINE, whereas those with an annealed microstructure have the layer sequence,PLAGIOCLASE : PARGASITE + SPINEL : PARGASITE : ORTHOPYROXENE : OLIVINE.Primary symplectite consists of fan-shaped grains of pargasite that open toward plagioclase and are ribbed by rods of spinel. On annealing to a single grain, low-angle grain boundaries disappear and spinel rods rotate into parallel positions. Primary orthopyroxene, initially radial to layer contacts, anneals to a single grain, rimming olivine. Irregular discontinuous layers and plumes of symplectic orthopyroxene+spinel disappear on annealing and a monomineralic layer of pargasite forms between orthopyroxene and the amphibole symplectite.The identity of composition of intercumulus pargasite and orthopyroxene with the same phases in primary coronas, the occurrence of primary and annealed coronas rimming cumulus ilmenite and the occurrence of radial orthopyroxene separating grains of cumulus olivine and separating cumulus olivine and plagioclase argue for the origin of primary coronas by fractional crystallization of spinel-saturated troctolitic magma at a pressure greater than 5 kbar.Irreversible thermodynamic calculations show that the mineral assemblage layer sequence of the primary coronas is diffusionally unstable and that this instability provides the driving force for their spontaneous transformation to the stable mineral assemblage layer sequence of the annealed coronas.

Plasma waves in inhomogeneous conducting films

In the present communication the dispersion equation is obtained for tangential plasma oscillations in a thin irregular layer while taking into account the effects of the electric field not being a potential. Study of the obtained equation shows that damping caused by the radiation from the layer for long-wave oscillations can be dominant.

Oogenesis of Cardiochiles nigriceps viereck (Hymenoptera : Braconidae): Histochemistry and development of the chorion with special reference to the fibrous layer

A fibrous layer on the surface of eggs of the parasitoid, Cardiochiles nigriceps (Hymenoptera : Braconidae), has been implicated by earlier studies in the evasion from encapsulation by host hemocytes. The present histochemical and ultrastructural study was undertaken to characterize fibrous layer material and to determine the source of fibrous layer and other components of the eggshell. The fibrous layer contains neutral glyco- or mucoprotein; acidic mucoproteins or glycosaminoglycans are absent. The mature eggshell is resolved into 5 morphologically distinct layers by electron microscopy: (from inner to outer) vitelline envelope, endochorion, an electron-dense “irregular layer”, papilliary layer and fibrous layer. During oogenesis each eggshell layer is laid down sequentially in the order mentioned above. Eggshell material appears to be produced by the follicle cells because these develop extensive rough endoplasmic reticulum and golgi apparatus and exhibit apparent exocytotic activity at the plasma membrane adjacent to the egg.

P-SV resonances in irregular low-velocity surface layers

Near-surface geological properties can have a large effect on the character of seismic arrivals. While it has long been recognized that a large velocity contrast between the surface layer and the substrate can cause reverberation of the seismic signal, the effects of small scale lateral heterogeneity on the wave field propagation have, to our knowledge, not been treated in detail. We show that lateral heterogeneity in the surface region can strongly alter the character of arriving seismic signals by causing a resonant coupling to the surface modes of the medium. We describe the effect using propagator matrix formalism and the Born approximation. We demonstrate the effect using finite difference simulations of P-SV wave propagation for a model containing a low-velocity surface layer having roughness along its interface with an elastic half-space. These simulations show that when a planar pulse is incident upon the low-velocity layer, the roughness induces a strong resonant coupling to Rayleigh modes, a condition which cannot occur for a laterally invariant medium. The resonant coupling causes a long coda following the direct seismic arrival. Frequency-wavenumber analysis of the simulated seismic arrivals recorded over the rough low-velocity layer shows that the scattered energy is distributed in FK space principally along the dispersion curves of the surface modes of the average smooth low-velocity layer. The amplitude of the simulated signal is modulated as a function of frequency according to reverberations in a smooth surface layer. Both the concentration of energy along the Rayleigh dispersion curves in FK space and the frequency modulation are predicted by the propagator matrix-Born scattering analysis.

Sclerotin and lipid in the waterproofing of the insect cuticle

In all the cuticles studied waterproofing is effected by extracuticular material, a mixture of sclerotin precursors and lipids, exuded from the tubular filaments of the pore canals. In Rhodnius larval abdomen it is a layer of thickness similar to the outer epicuticle, believed to be composed of ‘sclerotin’ and wax. in Schistocerca larval sternal cuticle and in Carausius sternal cuticle it is similar. In Tenebrio adult sternal cuticle of the abdomen, in both the extracuticular exudation and the contents of the distal endings of the tubular filaments, the wax component is obscured by hard ‘sclerotin’. In Manduca larva a very thin layer of ‘sclerotin’ and wax is covered by an irregular wax layer, average 0.75 μm, twice the thickness of the inner epicuticle. In Periplaneta and Blattella the abdominal cuticle is covered by a soft waxy layer, often about 1μm thick, which is mixed with argentaffin material. Below this is a very thin waterproof layer of wax and ‘sclerotin’ continuous with the contents of the tubular filaments, which is readily removed by adsorptive dusts. In Apis adult abdominal terga free wax plus sclerotin precursors form a thin layer which is known to be removed by adsorptive dusts. In Calliphora larva there is a very thin layer of the usual mixed wax and sclerotin and below this a thick (0.5 μm) layer, lipid staining and strongly osmiophil, likewise extracuticular and exuded from the epicuticular channels. This material (which is often called ‘outer epicuticle’) has the same staining and resistance properties as the true outer epicuticle on which it rests. In the abdomen of Calliphora adult the waterproofing wax-sclerotin mixture forms a thin layer over the entire cuticle including the surface of the microtrichia. There is also a thin detachable layer of free wax on the surface.

Electromagnetic induction in an irregular layer overlying the earth. The 2nd paper A semi-infinite medium of finite conductivity having an undulatory surface.

Electromagnetic induction by a uniform magnetic field in a semi-infinite medium of finite conductivity having a sinusoidal undulation at the surface is studied. The source field is assumed to be parallel to the mean surface. The apparent resistivity (ρa) vs. period of variation (T) relation is obtained at various points over the undulating surface by means of conventional magneto-telluric technique. The phase vs. T and the transfer function vs. T relations are also obtained from the electric and magnetic fields studied in this paper.It turns out that the ρa-T relation is little affected by the surface undulation. The order of magnitude of ρa value at various points over the surface does not vary although ρa for a longer period variation takes on a relatively lower value at a depressed portion of the undulatory surface. On the other hand, the transfer function vs. T relation differs from observation point to observation point depending upon the position of observation point on the undulatory topography.

Microwave emission from an irregular snow layer

Emission from an irregular snow layer is modeled by a layer of Mie scatterers using the radiative transfer method. Comparisons are made with measurements showing snow wetness effects and rough air-snow boundary effects. For convenience of reference, theoretical model behavior is also illustrated.

ULTRASTRUCTURE AND DEVELOPMENT OF THE MICROSPORANGIUM OF PSEUDOTSUGA MENZIESII (MIRB.) FRANCO. I. DORMANT STAGES

The dormant (mid‐November to mid‐February) microsporangia of Pseudotsuga menziesii (Douglas‐fir) contain pollen mother cells (PMC's) in diffuse diplotene, surrounded by 1–2 layers of tapetal cells and 3–4 layers of microsporangial wall cells. At the beginning of dormancy, PMC's are large and their walls are lysed. The cell walls contain a thick layer of loosely‐arranged fibrils which are produced in large vesicles in the PMC cytoplasm and are secreted across the plasma membrane. PMC's contain several layers of rough ER. The inner tangential and the radial walls of the tapetal cells are lysed. During dormancy the PMC's form many new autophagic vacuoles, the chromatin consists of a network of fine threads comprised of medium‐sized granules of uniform size and the nucleoli split. The outer tapetal wall is thick and becomes encrusted by an irregular lipid layer. The tapetal cytoplasm is similar to the PMC cytoplasm but is devoid of amyloplasts. The tapetal cytoplasm shows secretory activity at the beginning of dormancy and again near the end of dormancy. The later secretory activity results in the deposition of a spongy material, especially along the radial and inner walls of the tapetal cells. Tapetal cells contain 1–2 large nuclei which show prominent and irregular clumps of chromatin. Subcellular developmental changes occur in the dormant microsporangia of Pseudotsuga in much the same manner as has been reported for Pinus.

Reentrant ventricular arrhythmias in the late myocardial infarction period. 9. Electrophysiologic-anatomic correlation of reentrant circuits.

We studied isochronal maps of ventricular activation during ventricular arrhythmias induced by programmed premature stimulation in dogs 3-5 days after ligation of the left anterior descending coronary artery. The entire epicardial surface and selective intramural sites were recorded using a computerized multiplexing technique. The electrophysiologic data were correlated with the anatomic characteristics of the infarction. In nine of 17 dogs (55%), the induced ventricular rhythm was due to reentrant activation in the surviving epicardial layer overlying the infarction. The irregular epicardial layer (up to 4 mm thick) had grossly intact myocardial fibers on microscopic examination but showed abnormal electrophysiologic characteristics. The stimulated premature beat that initiated reentry produced a continuous arc of functional conduction block within the surviving epicardial layer. The activation wave front circulated slowly around both ends of the arc of block, rejoined on the distal side of the arc before breaking through the arc to reactivate an area proximal to the block. This resulted in splitting of the initial single arc of block into two arcs. Reentrant activation continued as two synchronous circuits that traveled clockwise around one arc and counterwise around the other. Reentry spontaneously terminated when the leading edge of both reentrant circuits encountered refractory tissue, resulting in the coalescence of the two arcs of block into one. The present study may increase the understanding of the electrophysiologic mechanism of some ventricular repetitive responses and tachyarrhythmias induced by programmed premature stimulation in the clinical laboratory.

The oviduct musculature of the cockroach Leucophaea maderae and its response to various neurotransmitters and hormones

AbstractThe musculature of the oviduct consists of an outer, irregular layer of longitudinal muscle and an inner layer of circular muscle. The four basic modes of activity—compression, segmentation, peristalsis, and reverse peristalsis—were evident in the isolated oviduct. These spontaneous events often occurred in an organized sequence. In fact eggs could be transported down the lateral oviducts by this myogenic activity once the sphincter between the common oviduct and vagina was severed. Myographic recordings were made of only the contractions of the longitudinal muscles.L‐glutamate caused a distinct phasic contraction at 2.2 × 10−5 M. The response became larger and more complex as the concentration of the amino acid was increased. Acetylcholine (1.6 × 10−5 M) caused either a phasic or tonic response, or a combination thereof. By contrast, 5HT and tyramine simply increased the frequency of small phasic contractions, although in some preparations both monoamines caused an inhibition. The ecdysones, a juvenile hormone analogue (1 × 10−6 M), and prostaglandin E2 had no effect on oviduct activity.Initially high KCI solutions (162 mM) without Ca++ induced a strong contraction but subsequent additions failed to do so. However, when a high KCI solution (158 mM) with 2 mM Ca++ was added to the preparation the response was partially restored. Also the potent calcium antagonist Mn++ (2mM) can suppress spontaneous activity.

Scattering and depolarization of electromagnetic waves in irregular stratified spheroidal structures of finite conductivity – full wave analysis

Scattering and depolarization of electromagnetic waves in irregular stratified, spheroidal structures (bodies of revolution) are investigated. Using complete expansions for the electromagnetic fields, Maxwell's equations are converted into sets of first order coupled differential equations for the forward and backward wave amplitudes. To obtain these generalized telegraphists' equations, exact boundary conditions are imposed at each of the interfaces between the irregular layers of the structure and Green's theorems are used to avoid term-by-term differentiation of the complete expansions. The electromagnetic parameters of the medium are assumed to vary as functions of the radial distance and the latitude. Excitations by arbitrary distributions of electric and magnetic sources are considered. Thus, this work can be applied to propagation in irregular ionospheric and tropospheric ducts. The solutions are shown to satisfy duality and reciprocity relationships in electromagnetic theory.

Palygorskite-Sepiolite Clays of Lebrija, Southern Spain

AbstractThe Upper Pliocene sediments near Lebrija in southern Spain contain commercial deposits of palygorskite and sepiolite. These sediments of continental origin consist chiefly of carbonate, marl, and clay resting on marine Pliocene quartzose sand. The lowest unit, the “Marly-Calcareous Bed,” consists of sepiolite-rich marl associated with concretions and irregular layers of chert, <0.5 m thick, and local diatomite layers, as well as limestone, sandy limestone, marl, and clayey sandstones. This unit has a maximum thickness of 30 m and contains three clay-mineral suites as follows: (1) bottom—sepiolite ± palygorskite; (2) center—sepiolite and palygorskite ± illite; (3) top—palygorskite and illite, ± sepiolite and smectite. Sepiolite decreases and palygorskite and illite increase toward the top, reflecting the composition of detrital material supplied to the basin. Beds 0.5–1 m thick locally and containing 50 to 60% sepiolite have been called “Tierra del Vino” (wine earth) because the material formerly was used to clarify and purify wine. The sepiolite-rich beds are as much as 15 m thick in the eastern part of the area. The upper unit is called the “Palygorskite Bed” because certain layers, 0.3 to 3 m thick, contain 35 to 75% palygorskite. The palygorskite-rich layers are interbedded with limestone and marl, and the entire unit is 15 m thick. The total resource of palygorskite is estimated at about 9 million tonnes.The sediments are believed to have been deposited in a brackish, lacustrine environment. Originally, tectonic stability and an arid climate favored the formation of sepiolite at about pH 8. Later, after significant weathering of the source rocks, detrital illite was transformed to palygorskite in the Mg- and Si-rich waters. Here, palygorskite was also precipitated directly.

Stratigraphic relationships within Martian polar cap deposits

Deposits of layered ice and dust accumulate on the smooth and banded terrains of the north and south polar cap deposits, while erosion of equator-facing slopes of layered terrain expose these layers. Banded terrain occurs at exposures of irregular layers resulting from slight erosion of the feather edges of layers deposited on pole-facing trough walls. These deposits unconformably overlap onto adjacent layered terrain. Stripping of layers occurs in areas of strong, multidirectional wind, forming striped terrain. Local wind scour has also produced steep scarps with crescentic planform, often associated with dune fields positioned immediately downwind. Unconformities are common within layered deposits in areas of complex topography at the north pole. These indicate that episodes of deposition of 5–10 layers alternate with slight erosion of pole-facing trough walls. Troughs that strike north-south alternate between erosional widening and deepening and depositional infilling, creating multiple unconformities. Troughs near the equatorward limit of polar deposits increase in relief by deposition on adjacent smooth terrain and, locally, by erosional deepening. Troughs may migrate poleward, replacing the relief increase by depositional infilling when they near the poles.

A structure with an irregular layer lattice in poly(γ‐methyl L‐glutamate‐co‐γ‐benzyl L‐glutamate) film

AbstractTwo types of films showing different characteristic x‐ray equatorial patterns were prepared from chloroform and N,N‐dimethylformamide solutions of poly(γ‐methyl L‐glutamate‐co‐γ‐benzyl L‐glutamate). In the film cast from chloroform solution, the x‐ray pattern on the equator consisted of a remarkable mixture of sharp and diffuse reflections, with the sharp reflections corresponding to integral values of 1/3k. On the other hand, in the film cast from N,N‐dimethylformamide solution, a well‐defined x‐ray pattern was observed. An explanation for this characteristic pattern of chloroform‐cast film was made on the basis of a structural model wherein stacking faults or dislocations are incorporated into the ordered structure characteristic of N,N‐dimethylformamide‐cast film. Two domains divided by a stacking fault are mutually displaced along the (100) crystal planes, but the shape and size of the unit cell is everywhere the same. The intensity distribution of x‐ray diffraction was calculated as a function of the probability of a stacking fault occurring in a regular sequence of (100) planes. The best correspondence with observation was obtained with a stacking fault in every three layers, on the average.

Scattering from a Rayleigh layer with an irregular interface

A theory of wave scattering from an inhomogeneous irregular layer has been developed with the radiative transfer method. It is shown that there is a basic difference between the plane and irregular layer formulation. When the inhomogeneities are represented by the Rayleigh scatterers, the plane layer problem can be solved with three Fourier components, whereas the irregular layer requires additional Fourier components until convergence is achieved. In general, smaller numbers of Fourier components are required for thicker layers. Comparisons between the backscattering coefficients of a plane versus an irregular Rayleigh layer indicate that the rough surface boundary causes the level difference between the like and the cross polarized returns to be smaller than the plane case. In addition, polarized returns may be dominated by surface roughness effects near vertical incidence. While the cross polarized return continues to be dominated by volume scattering parameters, the interaction between rough surface and volume scattering can cause significant change in both its angular shape and its level.

Emission from a Rayleigh layer with irregular boundaries

A theory of microwave emission from an irregular layer of Rayleigh scatterers is developed by combining an existing matrix doubling method for volume scattering with the Kirchhoff method in surface scattering. Effects of the layer boundaries are illustrated by comparing layers with plane boundaries vs layers with rough top or bottom boundaries and irregular layers. It is found that the major effect of an irregular top layer boundary is to slow down the variation of the layer emission as a function of the nadir angle and the major effect of an irregular bottom boundary is to increase the level of the layer emission. Comparisons of the developed layer model with snow emission indicate the potential use of such models in data interpretation.