Conical Segment Research Articles

Fine Structure of the Retinal Photoreceptors of the Domestic Cat (Felis catus)

The morphology of the retinal photoreceptors of the domestic cat (Felis catus) has been investigated by light and electron microscopy. In this species the photoreceptors can be readily differentiated and adequately described by the classical terminology of rods and cones, with rods being the more numerous. Rods are long slender cells with inner and outer segments of much the same diameter. Cones are shorter cells with a conical outer segment that tapers distally and an inner segment which is wider than the outer segment. Both rods and cones are highly polarized and compartmentalized cells and consist of an outer segment, a connecting cilium, an inner segment, a nuclear region and a synaptic process leading to an expanded synaptic ending. Morphological similarities and differences are noted between the rods and cones for the various regions of these cells.

Non-linear stability problem of an open conical sandwich shell under external pressure and compression

The stability problem of a shallow sandwich shell of conical segment shape, subjected to uniform external pressure and compression along generators is analysed based on the finitedeformation theory. With the help of the Ritz method the system of five non-linear, heterogeneous equations is obtained. They are the basic equations of elastic stability of the shell under consideration. The results of numerical calculations are presented in diagrams, which show the influence of basic mechanical properties and geometric parameters of the shell on the value of the upper and lower critical load.

Propagation of standing waves in axisymmetric cavities enclosing an inhomogeneous medium

This paper studies how gradients in speed of sound c and density ρ influence standing waves in an axisymmetric cavity. The c and ρ gradients are assumed independent of radial and circumferential coordinates of the cavity and to vary only along its axis. The effects on propagation of the c and ρ gradients are studied separately. First, the problem with a step function as c gradient in a cylindrical cavity is treated in detail since it is amenable to analytical solution. A smooth c gradient described by exponential functions is considered. In this case, a transfer matrix coupled to a numerical integration procedure is adapted to the solution of the differential equation governing the axial dependence. The quasilinear c2 gradient follows and it also yields to analysis. The poor energy transmission characteristics of transverse standing waves in cylindrical cavities with c gradient prompted consideration of a geometry that includes two cylindrical segments with different cross sections joined by a conical connector. The transfer matrix method couples the acoustics of various segments of cavities. The radial dependence in the conical segment is determined by the method of shooting while the axial dependence follows from numerical integration. The analysis is then extended to cavities with concentric center bodies. An approximation considers piecewise conical frustra and leads to discontinuous pressure gradients at the junction of conjoined segments. The approximate analysis is tested against numerical results from an accurate simulation that invokes a Green's function and surface elements with account made for medium inhomogeneity.

Oboe normal mode adjustment via reed and staple proportioning

We have analyzed a simple theoretical model of an oboe, having a truncated conical air column of variable length and a reed assembly consisting of a tapered neck leading to a closed, cylindrical cavity. Proportions are chosen for this assembly so that its input admittance at the bottom of the neck is very closely the same function of frequency as the admittance of the missing conical segment at the apex of the air column for frequencies below the tone-hole cutoff. The most important requirements are that the reed assembly by itself possess the same volume and lowest-mode frequency as the missing apex. The intervals between the first-mode frequency and the below-cutoff frequencies of the second, third, and fourth modes of the model instrument can be made harmonic to within five cents as the length of the air column is varied to sweep the first mode through an octave range. We have investigated the effects of small variations in the proportions of the reed assembly on the natural frequencies of the model instrument. The results provide practical guidance for adjustment of the reed structure of a real oboe to special features of its own not-quite-conical acoustical behavior.

Hyperballistic Vehicle Dynamics

An earlier developed Newtonian theory for prediction of the unsteady aerodynamics of hemisphere-cylinder-flare bodies has been extended to other hyperballistic geometries of general interest. Using generalized Newtonian theory, the effect of Mach number is accounted for down to moderate supersonic speeds. The nose geometry can be described analytically or given in tabular form for a slender axisymmetric shape, which can include slope discontinuities. The embedded aft body can also be of a general shape, described by a series of conical segments, including the cylinder as a conical segment of zero slope.

Oboe normal mode adjustment via reed‐staple proportioning

We have analyzed a simple theoretical model of an oboe, having a truncated conical air column of variable length and a reed assembly consisting of a tapered neck leading to a closed, cylindrical cavity. Proportions are chosen for this assembly so that its input admittance at the bottom of the neck is very closely the same function of frequency as the admittance of the missing conical segment at the apex of the air column for frequencies below the tone‐hole cutoff. The most important requirements are that the reed assembly by itself possess the same volume and lowest‐mode frequency as the missing apex. The intervals between the first‐mode frequency and the below‐cutoff frequencies of the second, third, and fourth modes of the model instrument can be made harmonic to within five cents as the length of the air column is varied to sweep the first mode through an octave range. We have investigated the effects of small variations in the proportions of the reed assembly on the natural frequencies of the model instrument. The results provide practical guidance for adjustment of the reed structure of a real oboe to special features of its own not‐quite‐conical acoustical behavior.

Safety Advantages of Prestressed Concrete Reactor Vessels

An attempt has been made to explain the advantages of the behavior of prestressed concrete reactor vessels in a simple, brief, and qualitative form. In contrast to the property of spontaneous propagation of brittle fracture in massive steel plates, the failure of one prestressing wire or tendon does not propagate into the adjacent wires or tendons. The pressure-deflection curve does not end by a sudden failure, but the decrease of slope on approach to failure is gradual and even after formation of through cracks the vessel would close if depressurized. The energy absorption capability in post-elastic deformation is much higher than that of a steel vessel which could fail by brittle fracture. A weak part is the top closure slab, but if it is designed sufficiently thick to assure that a separation of a conical segment does not create a hole through the slab, and if much higher safety factors are used than those for the barrel sections, a very favorable failure behavior is assured. Comparison of the behavior of concrete and steel vessels in accidental exposure to high temperature and the role of moisture in concrete deserve further investigation.

Water and ion regulation in cicadas in relation to xylem feeding

Cicadas feed on xylem fluid. This is hypotonic to the haemolymph and contains high concentrations of potassium, sodium, calcium, magnesium, chloride, and phosphate ions. The urine contains the same ions in the same proportions but in slightly lower concentrations. Amino acids and sucrose are present in xylem fluid and traces of amino acids are also found in urine. Water is rapidly shunted from foregut to hindgut via the filter chamber. Injection of xylem fluid into the oesophagus results in an immediate tenfold increase in flow rate in the ileum. The osmotic pressure of xylem fluid in the filter chamber rapidly rises whilst the osmotic pressure in the anterior part of the ileum rapidly falls. Absorption of nutrients and ions into the haemolymph probably occurs in the conical segment and anterior tubular midgut. Storage excretion of divalent ions occurs in the mid-midgut and ions may be transported from the haemolymph into the posterior tubular midgut. The Malpighian tubules secrete a fluid slightly hypertonic to blood containing K + (42 mM/l.] and Na + (14 mM/l.). The osmotic pressures within the internal Malpighian tubules and internal midgut in the filter chamber are considerably higher than the osmotic pressure of the xylem fluid when it first enters the filter chamber proper. Passive osmosis will occur and water will be shunted into the ileum. Reabsorption of K + and Na + occurs in the ileum.

Studies on water and ion transport in homopteran insects: Ultrastructure and cytochemistry of the cicadoid and cercopoid midgut

The midgut of cicadoid and cercopoid insects is differentiated at the anatomical, ultrastructural and cytochemical levels into a conical segment, anterior, mid, and posterior midgut. The cells of the conical segment and anterior midgut are cytochemically very similar. They differ in ultrastructure, the anterior midgut cells having a submicrovillar row of mitochondria and a very marked mucoprotein coat investing the microvilli. The mid-midgut contains mineral spherites, which are formed in cisternae in the endoplasmic reticulum, and ferritin. The posterior midgut differs cytochemically from the anterior midgut and the cells are characterized by deep narrow basal invaginations and the absence of a mucoprotein coat investing the microvilli. It is suggested that nutrient absorption occurs in the conical segment and anterior midgut. Ion absorption may also occur in the anterior midgut. Storage excretion of calcium, magnesium and phosphate occurs in the mid-midgut. Ferritin is also stored here but may be found in other regions of the midgut, particularly in the cicada. The posterior midgut may be involved in ion secretion which could be related to filter chamber function.

On hypersonic flow past conical segment bodies at large angle of attack

On hypersonic flow past conical segment bodies at large angle of attack

Study of flow in subsonic and transonic regions of a laval nozzle

A technique that makes it possible to calculate the flow in the subsonic, transonic, and supersonic regions of a Laval nozzle is proposed in [1]. In this method, based on numerical solution of the inverse problem of nozzle theory, a stable three-point difference scheme with variable layer step is used. The computation method is justified, and several asymptotic solutions are constructed; some qualitative characteristics of transonic flows are also noted. However, in [1] no parameteric study was made of flow in the subsonic and transonic regions. In this paper the method of [1] is used to study the dependence of the flow parameters on the geometric characteristics of the subsonic and transonic parts of the nozzle. The influence of the adiabatic exponent and the shape of the transonic region on flow in the supersonic part of the nozzle is examined. The numerical solution is compared with the results of special experiments in which flow in nozzles is studied using the technique proposed in [1]. 1. Parametric study of flow in the subsonic and transonic regions. The geometry of the subsonic and transonic regions of modern nozzles is characterized by the throat contour radius R2, conical segment slope 00, radius R1 of transition from conical to cylindrical segments, and contraction ratio n (ratio of radius of entrance to cylindrical part of nozzle to throat section radius) (Fig. 1). We examine the influence of these parameters on flow in the subsonic and transonic regions of the nozzle.

An hypothesis to account for a basic distinction between rods and cones

Autoradiographic studies indicate that outer segment disc formation continues throughout life in rods but not in cones. The outer segments of developing rods in amphibia are cone-shaped. The following hypothesis accounts for these observations. The first discs formed at the base of the outer segment are small. Progressively larger discs subsequently displace the smaller ones away from the base, producing a conical outer segment. At this stage of development, disc formation in cones is arrested. In rods, disc formation continues, disc diameter becomes stabilized, and the old discs are shed, thereby producing a cylindrical outer segment.