Elliptical Fields Research Articles

Characterization of a GABAergic population of interstitial amacrine cells in the teleost retina

We used postembedding immunocytochemistry with an antiserum against BSA-conjugated GABA to study the inner plexiform layer of a cyprinid teleost, the roach. In this part of the retina, we observed a distinct banding pattern of GABA-positive material. There was a narrow unstained region separating the distal sublamina a from the proximal sublamina b; each sublamina was further subdivided into four ( a) and two ( b) sublayers of heavier staining, respectively. Using three-dimensional reconstruction of series of half-micron tangential sections, we were able to characterize a population of interstitial amacrine cells which contained GABA-like immunoreactive material. These cells had elliptical dendritic fields (area: about 0.04 mm 2) and conspicuous, thick processes (dia. 4–5 μm). In tangential sections, the dendrites of individual cells appeared to be in close contact, occasionally resulting in difficulties in defining the boundaries of a single dendritic field. Two subpopulations of these cells were observed, one in each sublamina. By comparison with a catalogue of Golgi impregnated amacrine cells and cells microinjected with Lucifer Yellow or HRP, the identity of this type of interstitial amacrine cell is established and its possible physiological properties discussed. Apart from this GABA positive type, a second population of interstitial amacrine cell was observed which did not show positive reaction to the GABA antiserum used.

Seismic hazard in the Sannio-Matese area of Italy

The assessment of seismic hazard at five selected sites in the Sannio-Matese region is based on the computer program SRAMSC. Owing to the extensive historical data base for the output parameter, the MSK intensiy is chosen. The seismicity model is made up of five narrow area seismic sources. Circular or elliptical macroseismic fields are assigned to individual sources. A generalized Kovesligethy equation is used for this purpose as the attenuation relationship. The study reveals similar and a rather high hazard at the sites at Benevento, Boiano, and Melfi, which are located in the zone of highest seismic activity. At the Pomigliano and Lucera sites, the assessed hazard is much lower.

Cell populations of the ganglion cell layer: displaced amacrine and matching amacrine cells in the pigeon retina.

The proportion and size distribution of ganglion and non-ganglion cells in the ganglion cell layer of different areas of the pigeon retina was examined in whole-mounts of the retina by retrograde axonal transport of horseradish peroxidase (HRP) from large brain injections. A maximum of 98% of cells were labelled in the red field and a maximum of 77% in the peripheral yellow field. Unlabelled cell bodies were 30% smaller than labelled ganglion cells and had a mean diameter of 6.2 microns and a size range of 4 to 9 microns. The morphology of cells in the ganglion cell layer was examined by Golgi staining of retinal whole-mounts. Small glia, displaced amacrine and ganglion cells were found. Displaced amacrine cell bodies were about 30% smaller than ganglion cells and their size distribution was similar to the unlabelled cells in HRP preparations. Displaced amacrine cells had small rounded cell bodies (mean diameter 6.2 microns) increasing in size with eccentricity, and a unistratified dendritic tree of fine, nearly radial, varicose dendrites in sublamina 4 of the inner plexiform layer. They had elliptical dendritic fields (mean diameter 66 micron) aligned parallel to the retina's horizontal meridian. A population of amacrine cells was found with somas at the inner margin of the inner nuclear layer and soma and dendritic morphology matching those of displaced amacrines. These amacrine cells had unistratified dendritic trees at the junction of sublaminae 1 and 2 of the inner plexiform layer. Pigeon displaced amacrine cells and their matching amacrines are similar to starburst cells of the rabbit retina.(ABSTRACT TRUNCATED AT 250 WORDS)

Spatiotemporal Nonlinear Analysis of Frog Horizontal Cells

The shapes of horizontal cell receptive fields in the frog retina were determined using a retinotopic mapping technique based on a 16 X 16 spatial array of stimuli. Fields derived from first order kernel magnitude were sometimes circular but more often elliptical. Morphologic studies of Golgi stained horizontal cells showed most to be elliptical with a non random orientation tending to orthogonality. It is suggested that this feature makes unlikely an explanation of field eccentricity based on cell alignment. It is noted that cell axons tend to cross the retina in a line and may function as an extended dendrite to provide the eccentric and elliptical receptive fields.

Iron Losses Due to Elliptically Polarized Magnetic Fields

The iron losses occurring in an 11-mil cube-textured silicon-iron specimen, a 12-mil singly oriented silicon-iron specimen, and a 14-mil nonoriented silicon-iron specimen when subjected to a 60-cps elliptically polarized magnetic field (EPMF) are measured by means of a technique described previously and these EPMF losses are presented and compared. In general, the loss due to the EPMF was found to be equal to or less than the sum of the 60-cps alternating losses at the two induction levels that are the major and minor components of the EPMF. In the singly oriented and nonoriented silicon-iron specimens, a decrease in the losses for increasing flux densities for large elliptical fields is observed. The decrease continues until the eddy current loss becomes sufficiently large compared to the decrease in the rotational hysteresis loss to cause an increase in the total loss. This behavior was not found in the cube-textured specimen. An empirical expression, derived from the known pure alternating losses, is given which predicts the EPMF losses within 10% except at large EPMF's.

Horizontal wind fields and pressure gradient

AbstractThe method adopted in deriving the geostrophic and gradient wind relations, that of specifying a wind field and deriving the pressure field from it, is extended to find pressure fields for other flow patterns. The motion is referred to contours of isobaric surfaces and the analysis is limited to motion in terms of Cartesian co‐ordinates. Simple linear fields of motion introducing divergence and deformation are examined. It is found that fields which include deformation, e.g., cols and elliptical fields, are associated with appreciable acceleration and cross‐isobar flow, and that the addition of divergence leads to marked changes of pattern with time. Divergence imposed on solid rotation leads to marked cross‐isobar flow for pressure tendencies of average amount. A primitive cyclone model, moving to the east with a convergent centre of solid rotation surrounded by a simple vortex, is presented, and the pressure field resembles that of a deepening secondary. Finally it is shown that a translating cellular pattern resembles the waves observed in the upper troposphere.

Effect of electric field on Tyndall scattering

The study of the action of an electric field on the scattering intensity of sols has thus led to interesting results. The study is useful in determining the shape of the particles. The present technique would be supplementary to the studies of double refraction, in that the latter cannot be conveniently investigated in a highly scattering system. With slightly conducting sols, large fields can be used so as to produce saturation effects. Under such conditions, the use of rotating fields would bring about a unique orientation of the discs. A superposition of two A.C. fields of different cycles at right angles to each other would have the same effect as the circular field. The use of elliptical fields would reveal any want of equality of the two axes in the plane of discs of flat particles. The technique itself is simpler than the flow technique. Since there is often a large difference in the dielectric constant between the particles and the medium, the orientation is marked even with small fields, and the electric field is thus more powerful than the magnetic field in bringing about orientation.

Hysteresis Torque in Elliptically Polarized Fields

In ferromagnetic materials if the magnitude and direction of the magnetic field intensity are changed hysteresis occurs. This, in general, is of two types: the usual alternating hysteresis, and the torque component of hysteresis which gives rise to the rotational loss when the direction of the magnetic field intensity is changed and the magnitude is held fixed. By means of a torque magnetometer, the time average of the torque has been observed as a function of the applied magnetic field intensity for elliptical fields of different eccentricity. For the silicon iron disk investigated, and with the field along one axis (the first axis) as a parameter, the time average of the torque increases with applied field along the mutually perpendicular axis, reaching a maximum value at the bend in the magnetization curve and then decreases as saturation is approached. The torque curves first increase, go through a limiting curve, and then decrease as the field along the first axis is increased. A qualitative explanation of the shape and variation of the torque curves with field strength is suggested.