Conical Head Research Articles

Axisymmetric Mechanical Analysis of Ceramic Heads for Total Hip Replacement

An axisymmetric, mechanical analysis of conical press-fit ceramic heads is performed. The head strength and its fracture modes are assessed experimentally. The stress field is examined by finite element, strain gauge and photoelastic methods. An alternative head design, characterized by a cylindrical engagement with the stem, is analysed with the same techniques and its merits are explored.

Evolutionary Modification of Echinoid Sperm Correlates with Developmental Mode: (direct development/evolution of development/sea urchins/sperm morphology/genome size).

A significant fraction of living sea urchin species have completely or partially eliminated the pluteus larval stage and instead develop directly from embryo to adult. Direct developing sea urchins develop from large buoyant eggs. We present data to show that evolution of these large eggs is accompanied by the evolution of spermatozoa with elogate heads, in contrast with the conical sperm heads typical of most echinoids. Two congeneric Australian species, Heliocidaris tuberculata, which develops via a pluteus, and H. erythogramma, a direct developer, were investigated in detail. The sperm of H. erythrogramma have an elongate head (11 μm in length) as compared to the conical sperm head (5.6 μm) of H. tuberculata. Electrophoretic analysis of the sperm histones indicates that no unusual histones or protamines are associated with modified head morphology. Genome sizes were determined by flow cytometry. H. erythrogramma has a haploid genome size of 1.3 pg as compared to a haploid genome size of 0.95 pg for H. tuberculata. Other direct developing echinoids have elongate sperm heads, and co-evolution of gametes is indicated as a common feature of evolution of direct development in echinoids. The most extreme case, the direct developing cidaroid sea urchin, Phyllacanthus parvispinus, possesses the longest and narrowest sperm head (20 μm × 1 μm) ever observed in an echinoid.

Resistance of pentration of a conical rod into an elastoplastic material

Results are given of experiments for studying the penetration of a rod with a conical head section into steel St. 3 and aluminum alloy D16T at rate of 0-400 m/sec. Calculation relationshps are obtained for estimating the resistance to static and high-speed penetration of a rod with a concial head section into a semi-infinite elastoplastic material. A region is established for a reduction in penetration resistance connected with material warm-up. The prevailing effect of the ductile component of resistance on its increase within the range of rates studied is demonstrated.

High performance disc filter for dewatering mineral slurries

The operation of conventional disc filters often suffers from incomplete cake removal, filtrate blow-back and limited throughput rates. A modern disc filter has been developed to meet the increased requirements, especially those imposed by continuous pressure filtration. This disc filter is characterised by its extremely compact and flow-favourable design. Special features include a conical control head and tapered filter segments. The filter can be operated with vacuum or overpressure and at rotational speeds of up to 18rpm which is unique for disc filtration. A mineral slurry as well as even finer pulps with flotation tailing were filtered under industrial conditions. High throughput rates have been achieved just by increasing the disc velocity. An improved discharge system allows even thin filter cakes to be completely removed from the cloth. Thus a machine principle known since decades has been developed to new maturity and is available for industrial application.

On the Efficiency of Different Head Shapes to Perforate Thin Targets

Thomson’s approach to the perforation of thin metal targets is used to compare the efficiency of conical, parabolic, tangent ogival and secant-ogival heads, Thompson’s approximation of an ogival head and Kucher’s optimal head. Well-established empirical evidence suggests that for this type of target the tangent-ogival head is the most efficient one for the usual ratios of head length to radius of projectile. This is theoretically confirmed and explained by this paper.

Large deflection analysis of conical head pressure vessels

The present work investigates the nonlinear behaviour at and near the junction of cylindrical and conical shells under internal or external pressure. The results are useful for studying conical head pressure vessels and components of missiles, spacecrafts, underwater vessels, nuclear reactors, etc.Reissner's basic concept for the large deformation of axisymmetric shells, with proper modification and specialization, are used in the derivation of the governing equations for the present problem. The nonlinear differential equations are then solved by the multisegment method of integration developed byKalnins andLestingi. Results of this analysis indicate that the linear theory is very inadequate and conservative in its prediction of stresses and deformations in the region of the junction of the cylindrical and conical parts. In this analysis the tip of the conical part, where present, is assumed to be replaced by a very small spherical cap meeting tangentially with the conical part, in order to avoid singularity and to render the solution more realistic.

The Bronze Hut Urn in the Metropolitan Museum of Art

ON A RECENT VISIT to New York I had occasion, through the kindness of my colleagues in the Department of Greek and Roman Art of the Metropolitan Museum, to examine the bronze hut urn (Figures 14) that was on exhibition in the room dedicated to Etruscan antiquities. The urn,' constructed of sheet bronze, is in the shape of a hut with an oval plan and with vertical walls that slope slightly inward toward the top. A bronze strip, bent to an angle of nearly ninety degrees, serves to join the base of the walls to the sheet that forms the floor of the urn. The various parts are held together by rivets: eleven on the bottom, with large, slightly convex heads, and eighteen, with conical heads, along the lower part of the wall. A bronze molding attached with small bronze pins and incised with vertical hatching runs along the lower edge of the wall and the jambs of the doorway; similar moldings frame the door itself and mark the junction of the roof and the eaves. The trapezoidal doorway is surrounded on three sides by bronze strips fastened to the wall by means of eight bronze rivets with conical heads. Horizontal eyelets are attached to the middle of each of the two vertical strips, and a similar eyelet is attached to the center of the door by three small rivets with hemispherical heads; a long bronze pin with a conical head passes through the three eyelets, thus closing the urn. To either side of the entrance are vertical pilaster strips, each attached to the wall by two nails with hemispherical heads; each strip is capped by a rounded, capital-like protuberance tapered at the top. On the opposite side of the urn are two more pilaster strips, plain and without capitals; their position does not correspond exactly to that of the first pair but is determined by the rafters of the roof. The roof is divided into four somewhat convex

A computer program for nonlinear analysis of pressure vessels

This paper describes the nonlinear analysis of pressure vessels necessary for taking into account the large deformations that take place at the junctions of shells of different geometries. Specifically, a computer program has been developed, based on both the linear and nonlinear theories of shells, which obtains numerical solutions for the most commonly used types of pressure vessels, namely those with spherical, ellipsoidal or conical heads and also flat-end pressure vessels. A multisegment integration technique has been used to obtain the solutions of the governing equations. The computed solutions are found to be highly accurate when compared with the known results of simple shells, as no nonlinear analysis is reported in the literature on the shell junctions in pressure vessels.

The fine structure of the spermatozoa of Siphonaria algesirae (Gastropoda, Pulmonata).

The sperm of Siphonaria algesirae (Gastropoda, Pulmonata), a species with internal fertilization, was studied by light and electron microscopy. The spermatozoon is a very long, uniflagellate cell composed of a conical head with an apical acrosome, a midpiece with a helically coiled external sheath containing a complex mitochondrial derivative with a wavelength of ∼ 5.5 μm, and an endpiece. There are no axonemal microtubules. Instead, nine homogeneous coarse fibers with transverse striations in the apical zone project toward the anterior section of the midpiece. In the posterior zone of the midpiece the coarse fibers are differentiated in a common microtubular axoneme. The complex mitochondrial derivative of the midpiece shows an organized group of 100 Å diameter spherical particles. Externally the midpiece is surrounded along its length by a cylinder formed by two membranes. A complex structure separates the transitional zone between the midpiece and the endpiece.

ThePentoxylonplant

The various dispersed organs belonging to thePentoxylonplant viz.Pentoxylon(stem),Nipaniophyllum(leaf),Sahnia(male flower) andCarnoconites(female cone) have been studied in detail. Apart from the long shoots (type 1 shoots), the plant bore three different kinds of short shoots: the thick woody short shoots, each with a broadly conical head (type 2 shoots); the slender parenchymatous short shoots (type 3 shoots); and the slightly thicker parenchymatous short shoot (type 4 shoot) terminating in aSahniaflower. In addition to the well knownNipaniophyllum raoileaves a second species,N. hobsoniisp. nov., is recognized. InSahniathe sporangiophores were borne on a collar-like structure formed by the raised margin of the receptacle. The broadly conical head of the thick woody short shoot (type 2 shoot) might be the basis of the cone-bearing branchlets ofCarnoconitesfruits. The seeds ofCarnoconitesare spirally arranged rather than being in longitudinal rows as previously suggested.Pentoxylonwas probably a shrubby plant which grew beside water. It sent up erect branched leafy shoots which after a few seasons of growth flopped onto the ground or on other stems, making a thicket. Although the stem,Pentoxylon, resemblesMedullosaandRhexoxylonanatomically, the reproductive parts of the plant,SahniaandCarnoconites, are unlike those of any group of gymnosperms. ThePentoxylonplant is accordingly regarded as an extinct gymnosperm of unknown affinity.Nipanioxylon guptaihas previously been regarded as related toPentoxylon, but its holotype is believed to be a conifer and has nothing to do with thePentoxylonplant.

Determination of Volume of a Partially Full Horizontal Cylindrical Tank With Conical Heads

Determination of Volume of a Partially Full Horizontal Cylindrical Tank With Conical Heads

Spermatogenesis in the Non-Scrotal Bat–<i>Rhinopoma kinnear</i><i>i</i> Wroughton (Microchiroptera: Mammalia)

Spermatogenesis in the non-scrotal, insectivorous microchiropteran, Rhinopoma kinneari Wroughton, is a cyclic phenomenon. It comprises (i) eleven cell associations, and (ii) 16 evolutive steps in spermiogenesis. In the seminiferous epithelium, spermatogonia of the A, intermediate (In), and B type are characteristically present. Leptotene, pachytene and diakinesis stages were easily discerned in dividing spermatocytes. During the 16-step spermiogenesis, the acrosomic system develops through the Golgi, cap, acrosome and maturation phases. The relative frequency of various cell associations differs markedly and is significantly at variance with other mammalian species. Fully formed spermatozoa are dimorphic with conical or blunt heads.

Description of Helicotylenchus amplius n. sp. and a key to the Canadian species of the genus (Nematoda: Hoplolaimidae)

Helicotylenchus amplius n. sp., a parthenogenetic plant-parasitic spiral nematode in Canada, is described and illustrated. The distinguishing characters are a thick, digitate ventral tail projection with a terminal mucro, fine annulations on the tail end and open-ended lateral field, a conical head, stylet length of 26–29 μm, and a deep vulval atrium and large uterus which occupies most of the body width. A key is provided to aid in the identification of the Canadian species of Helicotylenchus Steiner, 1945.

Joining by plating: Optimization of occluded angle

An empirical method for predicting the minimum angle necessary for maximum joint strength in materials joined by plating was developed by way of a proposed power law failure function whose coefficients are taken from ring shear and conical head tensile data for plating/substrate combinations and whose exponent is determined from one set of plated joint data. Experimental results are presented for Al-Ni-Al (7975-T6) and AM363-Ni-AM363 joints, and the failure function is used to predict joint strengths for Al-Ni-Al (2024-T6), UTi-Ni-UTi and Be-Ni-Be.

The spermatozoon of arthropoda. XXX. The multiflagellate spermatozoon in the termite Mastotermes darwiniensis.

In this paper the spermatozoon of the termite Mastotermes darwiniensis is described. It is the first example of a multiflagellate sperm cell in animals. The sperm consists of a conical head and 100 flagella. Other remarkable features of this sperm cell are the absence of an acrosome, the presence of centrioles containing doublet microtubules instead of triplets, and the presence of axonemes devoid of central tubules and with doublets bearing only one arm. The flagella are feebly motile.

Computer-Controlled System for the Investigation of the Flow behind Wings

A completely computer-controlled wind-tunnel test facility designed for measurements of the vortical flow tie Id behind a lifting swept-back wing is described. The vortex generator model is a pressure-plotted rootmounted half-wing. To avoid unrepresentative end effects, distributed wingroot suction is applied over an area surrounding the root chord. The detailed design and calibration of the root suction system is discussed. Flow field measurements were made using a precalibrated non-nulling blunted conical five-hole probe. The use of the conical head made probe calibration over a wide flow angle range, and the consequent memory required to store the calibration data, a simple task. The program developed can calculate and plot, on-line, the three components of velocity and vorticity, the total pressure loss coefficient, and the circulation distribution. Because of the speed and large capability for data handling, detailed flow surveys behind the wing were made feasible. As a result of these automated flowfield measurements, it was possible to account for almost all of the vorticity shed from the wing. The rollup is neither complete nor axisymmetric in form within five wingspans downstream.

Body Form and Locomotion in Sharks

A revised interpretation of the mode of action of the heterocercal tail in sharks shows that the upturned tail axis tends to produce a thrust directed downwards behind the centre of balance of the fish and thus gives a moment turning the head upwards. This is countered in two ways—by the rotation of the tail along its longitudinal axis during each lateral beat, and through the action of the ventral hypochordal lobe. The shape of the tail and the mode of action of the tail in all sharks so far considered reflects a balance between these three factors, in all of them the net effect being the production of a forward thrust from the tail that passes directly through the centre of balance of the fiish. There is normally therefore no tendency for the fish to turn around the centre of balance in a sagittal plane but there is a net sinking effect that is countered by the planning effect of the pectoral fins and the ventral surface of the head. A study of 56 species of sharks shows that the tail is constructed according to a remarkably consistent common plan, the extremes being the high angled rather symmetrical tail of pelagic sharks such as hums, Lamna and Rhincodon and the straight tails of benthic sharks such as Ginglymostoma in which a ventral hypochordal lobe is absent. When the general body shape of sharks, including the position of insertion of the median and paired fins and the pattern of growth of fin surface areas is considered, the uniformity of the shark body plan and locomolor function is further emphasised. Four patterns of body form in sharks are recognised: 1) The fast swimming pelagic sharks and the whale sharks have a tail with a high aspect ratio, a conical head, a lateral fluke on the caudal peduncle. 2) The generalised sharks typified by the Carcharhinidae, have lower heterocercal angles, a flattened ventral surface on the head and lack the caudal fluke. 3) The demersal sharks typified by the catsharks (Scyliorhinidae) have a very low, almost straight tail. The ventral hypochordal lobe is absent and the first dorsal fin is posterior in position. 4) The squalomorph sharks are distinct in the absence of the anal fin, presence of a marked epicaudal lobe in the tail and often an elevated insertion of the pectorals. The anal and second dorsal fins are always the smallest fins and the pectorals grow at the fastest rate. In general there is an inverse relationship between size and rale of growth of all fins and the ventral surface of the head. In hammerheads the growth data confirms that the head has a significant planing action in swimming. The pectoral, second dorsal and anal fins show an extreme constancy of position of insertion in all sharks studied. The locomotor mechanism of sharks is adapted for an efficient cruising swimming but at the same time, the potential instability in the sagittal plan allows for the production of turning moments that are used in attack and feeding.

Bifurcation buckling of shells of revolution including large deflections, plasticity and creep

A summary is first presented of the conceptual difficulties and paradoxes surrounding plastic bifurcation buckling analysis. Briefly discussed are nonconservativeness, loading rate during buckling, and the discrepancy of buckling predictions with use of J2 flow theory vs J2 deformation theory. The axisymmetric prebuckling analysis, including large deflections, elastic-plastic material behavior and creep is summarized. Details are given on the analysis of nonsymmetric bifurcation from the deformed axisymmetric state. Both J2 flow theory and J2 deformation theory are described. The treatment, based on the finite-difference energy method, applies to layered segmented and branched shells of arbitrary meridional shape composed of a number of different elastic-plastic materials. Numerical results generated with a computer program based on the analysis are presented for an externally pressurized cylinder with conical heads.

Comparisons of test and theory for nonsymmetric elastic-plastic buckling of shells of revolution

Experimental and analytical buckling pressures are presented for very carefully fabricated thin cylindrical shells with 45, 60 and 75° conical heads and for cylindrical shells with torispherical heads pierced by axisymmetric cylindrical nozzles of various thicknesses and diameters. Nonsymmetric buckling occurs at pressures for which some of the material is loading plastically in the neighborhoods of stress concentrations caused by meridional slope discontinuities. The buckling pressures for the cone-cylinder vessels are predicted within 2.6 per cent and for the pierced torispherical vessels within 4.4 per cent with use of BOSOR5, a computer program based on the finite difference energy method in which axisymmetric large deflections, nonlinear material properties and nonsymmetric bifurcation buckling are accounted for. The predicted buckling pressures of the pierced torispherical specimens are rather sensitive to details of the analytical model in the neighborhood of the juncture between the nozzle and the head. The buckling pressures of the cone-cylinder vessels can be accurately predicted by treatment of the wall material as elastic, enforcement of the full compatibility conditions at the juncture in the prebuckling analysis, and release of the rotation compatibility condition in the bifurcation (eigenvalue) analysis.

Cytoarchitecture of nucleus sphericus in the common boa, Constrictor constrictor.

AbstractThe normal anatomy of nucleus sphericus in the common boa (Constrictor constrictor) is described here on the basis of routine light microscopic and Golgi material. Nucleus sphericus is a cup‐shaped aggregation of cells lying in the forebrain posterior to the anterior commissure and consisting of three concentric layers. The marginal layer is subependymal, is continuous rostrally with the anterior commissure, and contains fusiform cells with discoidal dendritic fields tangent to the mural layer, Marginal cell axons entwine mural cell dendrites. The mural layer forms the walls of the cup and appears as a closed ring of cells in transverse sections. Mural cell dendrites extend radially into the marginal and hilar layers and horizontally within the mural layer. All of these dendrites are profusely covered by dendritic spines with conical heads and slender stalks. Mural cell axons ascend to the marginal layer. The hilar layer forms the cup's cavity containing scattered cells whose dendrites extend in all directions and whose axons approach the cup's mouth. Afferent fibers in the nucleus run predominately at right angles to mural cell dendrites bearing varicosities at irregular intervals.