Oblate Spheroidal Shape Research Articles

Pollen morphology in Brazilian species of Gloxiniinae (Gesneriaceae): variation in apertures and pattern of ornamentation

Gloxiniinae comprises herbs and subshrubs usually growing on rocky outcrops, rocky fields or gallery forests. For Gesneriaceae in some cases variations in pollen morphology allow the differentiation of genera and species. We studied the pollen grains of ten Brazilian species of Gloxiniinae (Gesneriaceae), including the genera Chautemsia, Gloxinia, Goyazia, Mandirola and Seemannia with the purposes of describing the pollen morphology of these genera, and contributing to the taxonomic characterization of the group and a better delimitation of genera and species of Gesneriaceae. The pollen grains were acetolyzed, measured, photographed and described qualitatively. Quantitative data were analyzed through descriptive and multivariate statistics. Non-acetolyzed pollen grains were observed in SEM and TEM in order to provide more details of the ornamentation and the structure of the exine. The analyzed species differ as to the pollen amb, shape, length, width and ends of colpi, presence or absence of margo, type of endoaperture and exine ornamentation. We found circular, subcircular and subtriangular amb, oblate spheroidal and subprolate shape, long or very long colpi, narrow, wide or very wide, with or without margo, lalongate or lolongate endoaperture in microreticulate or reticulate pollen grains. The reticulate ornamentation appears in the Gloxinia species’ pollen grains, and lolongate endoapertures represent the pattern for the subtribe pollen grains except in Chautemsia. The pollen grain metrics examined by principal component analysis allow generic distinction. We conclude that qualitative and quantitative pollen data help to delimit the genera and species of Gloxiniinae.

Palynological studies on some medicinal mallows from Punjab, India.

Seven plant species belonging to family Malvaceae were subjected to standard palynological studies in order to generate data for pollen characterization and identification of medicinally important mallows from Punjab, NW India. Pollen grains of this family are unique being porate and echinate having isolated spines. Pollen grains are either 3-porate, 6-7 porate or polypantoporate with oblate spheroidal shape and reticulate or semitectate reticulate exine. Based on various palynological parameters like the range in size, shape, aperture, exine thickness, ornamentation, etc. key to identification of presently studied taxa has been evolved.

Verified solutions for the gravitational attraction to an oblate spheroid: Implications for planet mass and satellite orbits

Forces external to the oblate spheroid shape, observed from planetary to galactic scales, are demonstrably non-central, which has important ramifications for planetary science. We simplify historic formulae and derive new analytical solutions for the gravitational potential and force outside a constant density oblate. Numerical calculations that sum point mass contributions in a >109 element mesh confirm our equations. We show that contours of constant force and potential about oblate bodies are closely approximated by two confocal families whose foci (f) respectively are (9/10)½ae and (3/5)½ae for a body with f = ae. This leads to useful approximations that address internal density variations. We demonstrate that the force on a general point is not directed towards the oblate's center, nor are forces simply proportional to the inverse square of that distance, despite forces in the equatorial and axial directions pointing towards the center. Our results explain complex dynamics of galactic systems. Because most planets and stars have an aspect ratio >0.9, the spherical approximation is reasonable except for orbits within ∼2 body radii. We show that applying the “generalized” potential, which assumes central forces, yields J2 values half those expected for oblate bodies, and probably underestimates masses of Uranus and Neptune by ∼0.2%. We show that the inner Saturnian moons are subject to non-central forces, which may affect calculations of their orbital precession. Our new series should improve interpretation of flyby data.

Electrochemical Tuning of Magnetism in Ordered Mesoporous Transition-Metal Ferrite Films for Micromagnetic Actuation

Controlling magnetism in situ and in a reversible manner using battery redox chemistry is a new concept in the wider field of magnetoelectrics, and electrochemical lithium tuning of electrode materials is one such approach. Here we show that the general idea of combining nanomagnetism and electrochemical energy storage concepts can be applied to ordered mesoporous spinel ferrite thin films. Via an evaporation-induced self-assembly method, a series of cobalt and nickel ferrites (CoFe2O4, Co0.5Ni0.5Fe2O4, and NiFe2O4) were prepared and characterized by electron microscopy, grazing-incidence small- and wide-angle X-ray scattering, 57Fe Mossbauer spectroscopy, and magnetometry. The dip-coated films after heating in air to temperatures beyond 600 °C are single phase with partially inverted spinel structures and exhibit 15–20 nm pores of oblate spheroidal shape arranged on a cubic lattice. Magnetic measurements clearly show stable ferrimagnetic ordering at room temperature, especially for the cobalt-based mater...

Evaporation of oblate spheroidal droplets: A theoretical analysis

ABSTRACTThe time-dependent evaporation of an oblate spheroidal droplet that undergoes forced convection was numerically investigated by solving the governing equations of energy, mass, and momentum. The research results elucidate the effects of oblate spheroid shape on droplet evaporation. A quantitative evaluation of spheroidal geometrical parameters (i.e., equatorial diameter, surface area, and volume) reveals that the evaporation rate increases at a much higher rate for an oblate droplet that approaches a disk-like shape of the same equivalent volume as a sphere. The variation of local Sherwood number on the surface of an oblate spheroid was obtained for the Reynolds number (2 ≤ Re ≤ 150) and the droplet axis ratio (0.1 ≤ Axr ≤ 0.9).

Determination of Shape and Sphericity of Silicon Quantum Dots Imaged by EFTEM‐Tomography

The shape of size‐controlled silicon nanocrystals (Si NCs) embedded in SiO2 is investigated by tomographic energy‐filtered transmission electron microscopy (EFTEM). The sphericity of the quantum dots is determined by computational analyses. In contrast to other fabrication methods, we demonstrate that the NCs in superlattices are non‐agglomerated, individual clusters with slightly oblate spheroidal shape. This allows for low surface‐to‐volume ratios and thereby low non‐radiative defect densities as required by optoelectronic or sensing applications. A near‐spherical shape is also a prerequisite for the direct comparison of Si quantum dots (QDs) with theoretical simulations.

Toroidal high-spin isomers in the nucleus 120304

Strongly deformed oblate superheavy nuclei form an intriguing region where the toroidal nuclear structures may bifurcate from the oblate spheroidal shape. The bifurcation may be facilitated when the nucleus is endowed with a large angular moment about the symmetry axis with $I=I_{z}$. The toroidal high-$K$ isomeric states at their local energy minima can be theoretically predicted using the cranked self-consistent Skyrme-Hartree-Fock method. We use the cranked Skyrme-Hartree-Fock method to predict the properties of the toroidal high-spin isomers in the superheavy nucleus $^{304}{120}_{184}$.

Experimental study of bubble dynamics of isolated bubbles in water pool boiling at subatmospheric pressures

The purpose of this work is to expose specific features of bubble dynamics in water pool boiling at low pressure in comparison with the atmospheric pressure. At subatmospheric pressures, the boiling environment is known to be very non-homogeneous, both in terms of pressure and subcooling degree. As a consequence, thermophysical properties of the fluid are not homogeneous either. These non-homogeneities are supposed to be responsible for the particular shape, size and departure frequency of bubble observed at low pressure.Experiments of water pool boiling were conducted at saturation state from atmospheric pressure (Tsat=100°C) down to 4.2kPa (Tsat=30°C) with a single imposed heat flux at the heater. Videos of each experiment were recorded with a high speed camera in order to analyze the bubble dynamics for different pressures.Increases of the bubble size and of the detachment frequency are observed as the pressure decreases while the bubble shape changes: a near-spherical shape at atmospheric pressure to an oblate spheroidal shape in the lowest investigated pressure range through a mushroom shape and/or vapor columns due to the rapid growth of successive bubbles sucked into the wake of the first one in the range of intermediate pressures. Recondensation of bubbles occurs rapidly after departure because of the subcooling degree. A home-made image processing software allowed calculating some quantitative parameters of the bubble dynamics such as the instantaneous volume and the departure frequency from the video records.

The locations of triangular equilibrium points in elliptic restricted three-body problem under the oblateness and radiation Effects

The Restricted Three-Body Problem (R3BP) considers motion of a third infinitesimal object under the gravitational influences of the primaries (bigger and smaller massive bodies) whose orbits are around the center of mass. If the orbits are elliptical, this belongs to Elliptic R3BP (ER3BP). In planar case it possesses five equilibrium points consisting of three collinear (L1, L2, and L3) and two triangular (L4 and L5). To mimic a better astrophysical R3BP, such as motion of a satellite in star-planet system, the classical problem can be generalized by considering the effects of radiation pressure and oblate spheroid shape on the primaries. We study analytically the locations and the stability of L4 and L5 equilibrium points in the frame of ER3BP with incorporating the effects of radiation for bigger primary and oblateness for smaller primary. Our study suggests that the oblateness factor (A2) and the radiation factor (q1) shift the positions of L4 and L5 points compared with the classical ones. We also find that there is a stability limit for motion of the third body around these points.

Morphology of sol-gel porous In-Ga-Zn-O thin films as a function of annealing temperatures

The physics of solution-processed thin films is studied with the example of In-Ga-Zn-O. After annealing at 450°C, the films become fully inorganic and the pore distribution is modeled by a hexagonal close-packed based structure. The surface porosity is approximately 0.23 and the volume porosity deduced from small-angle X-ray scattering is approximately 0.26. The corresponding specific surface area is in the range of 65m2g−1. An instability model allows to successfully describe the film morphology. The solution diffusion coefficient, estimated from the rate of thinning as a function of temperature, follows an Arrhenius behavior with an activation energy of approximately 9.1×103Jmol−1 and a pre-exponential coefficient D0 of approximately 1.8×10−8m2s−1. Moreover, the surface tension-to-viscosity ratio of the solution is determined from the surface morphology. In addition, the observed phase separation between ZnO and Ga2O3 may come from the solubility difference of these oxides in the solvent. This separation has a major consequence on the electronic material properties. Finally, during cooling, the large tensile stress occurring between the film and the substrate is relaxed by the pores which adopt an oblate spheroid shape. The surface energy of In-Ga-Zn-O is then estimated to 1.5Jm−2 from the pressure on the spheroidal pore.

A Theoretical Study of Indentation with an Oblate Spheroid Shape

In this study, firstly we introduced general mathematical concepts related to the geometrical form of ellipse and ellipsoid. Secondly, the hardness was calculated when we used an indenter having a geometrical shape of an oblate spheroid; the mathematical expressions of static hardness were determined as functions of the applied load, the radius or the depth of the imprint area. The general static hardness formula was expressed considering the projected and the real area imprint of the oblate spheroid indenter. Thirdly mathematical assumptions were introduced in order to simplify the mirohardness and nanohardness formulas when we used the real imprint area. Finally we did a comparative study between the oblate spheroid and the spherical indenters.

Static black holes with axial symmetry in asymptoticallyAdS4spacetime

The known static electrovacuum black holes in a globally ${\mathrm{AdS}}_{4}$ background have an event horizon which is geometrically a round sphere. In this work we argue that the situation is different in models with matter fields possessing an explicit dependence on the azimuthal angle $\ensuremath{\varphi}$, which, however, does not manifest at the level of the energy-momentum tensor. As a result, the full solutions are axially symmetric only, possessing a single (timelike) Killing vector field. Explicit examples of such static black holes are constructed in Einstein--(complex) scalar field and Einstein--Yang-Mills theories. The basic properties of these solutions are discussed, looking for generic features. For example, we notice that the horizon has an oblate spheroidal shape for solutions with a scalar field and a prolate one for black holes with Yang-Mills fields. The deviation from sphericity of the horizon geometry manifests itself in the holographic stress tensor. Finally, based on the results obtained in the probe limit, we conjecture the existence in Einstein-Maxwell theory of static black holes with axial symmetry only.

Overcoming the adverse effects of substrate on the waveguiding properties of plasmonic nanoparticle chains

We have studied numerically the propagation of surface plasmon polaritons (SPPs) in linear periodic chains of plasmonic nanoparticles of different shapes. The chains are deposited on top of a thick dielectric substrate. While in many commonly considered cases the substrate tends to suppress the SPP propagation, we have found that this adverse effect is practically absent in the case when the nanoparticles have the shape of oblate spheroids with sufficiently small aspect ratio (e.g., nanodisks) whose axes of symmetry coincide with the axis of the chain.

Liquid-body resonance while contacting a rotating superhydrophobic surface.

We advance a scheme in which a liquid body on a stationary tip in contact with a rotating superhydrophobic surface is able to maintain resonance primarily from stick-slip events. With tip-to-surface spacing in the range 2.73 ≤ h < 2.45 mm for a volume of 10 μL, the liquid body was found to exhibit resonance independent of the speed of the drum. The mechanics were found to be due to a surface-tension-controlled vibration mode based on the natural frequency values determined. With spacing in the range 2.45 ≤ h < 2.15 mm imposed for a volume of 10 μL, the contact length of the liquid body was found to vary with rotation of the SH drum. This was due to the stick-slip events being able to generate higher energy fluctuations causing the liquid-solid contact areas to vary since the almost oblate spheroid shape of the liquid body had intrinsically higher surface energies. This resulted in the natural frequency perturbations being frequency- and amplitude-modulated over a lower frequency carrier. These findings have positive implications for microfluidic sensing.

Self-consistent internal structure of a rotating gaseous planet and its comparison with an approximation by oblate spheroidal equidensity surfaces

In an important paper, Roberts (1963b) studied the hydrostatic equilibrium of an isolated, self-gravitating, rapidly rotating polytropic gaseous body based on a controversial assumption/approximation that all (outer and internal) equidensity surfaces are in the shape of oblate spheroids whose eccentricities are a function of the equatorial radius and whose axes of symmetry are parallel to the rotation axis. We compute the three-dimensional, finite-element, fully self-consistent, continuous solution for a rapidly rotating polytropic gaseous body with Jupiter-like parameters without making any prior assumptions about its outer shape and internal structure. Upon partially relaxing the Roberts’ approximation by assuming that only the outer equidensity surface is in the shape of an oblate spheroid, we also compute a finite-element solution with the same parameters without making any prior assumptions about its internal structure. It is found that all equidensity surfaces of the fully self-consistent solution differ only slightly from the oblate spheroidal shape. It is also found that the characteristic difference between the fully self-consistent solution and the outer-spheroidal-shape solution is insignificantly small. Our results suggest that the Roberts’ assumption of spheroidal equidensity surfaces represents a reasonably accurate approximation for rotating polytropic gaseous bodies with Jupiter-like parameters. The numerical accuracy of our finite-element solution is checked by an exact analytic solution based on the Green’s function using the spheroidal wave function. The three different solutions in non-spherical geometries – the fully self-consistent numerical solution, the numerical solution with the outer spheroidal shape and the exact analytical solution – can also serve as a useful benchmark for other solutions based on different numerical methods.

Pollen morphology of Poaceae (Poales) in the Azores, Portugal

The objective of this study was to expand knowledge on the Poaceae and morphologically describe pollen grains of species occurring in the Azores Archipelago, Portugal. Pollen grains from each species under study were subjected to standard acetolysis, mounting of at least three permanent slides of each species for observations and measurement of pollen grains under light and scanning electron microscope. With regard to pollen morphology, all pollen grains were arranged as monads, with a single pore-type aperture – monoporate, featuring annulus and operculum; and outline in polar view circular, sub-circular and ovalate. Most species featured pollen size small, except for Agrostis stolonifera with pollen size very small, Brachypodium sylvaticum with pollen size medium, Zea mays with pollen size large. Species endemic to the archipelago show ornamentation pattern ranging between areolate-microechinate, microechinate, microrugulate-microechinate and verrucate-microechinate, most of which feature exine surface areolate-microechinate. Among endemic species, Rostraria azorica stood out for its oblate-spheroidal shape, whereas most species showed prolate-spheroidal shape.

Heat and Mass Transfer during Drying of Lentil Based on the Non-Equilibrium Thermodynamics: A Numerical Study

This paper aims to present a mathematical model, based on the thermodynamics of irreversible processes to describe both the heat and mass transfer (liquid and vapor) during the drying of bodies with oblate spheroidal shape. The model was applied to describe drying of lentil grain, considering variables transport coefficients and convective boundary conditions at the surface of the solid. All equations were presented in oblate spheroidal coordinates and numerically solved by using the finite-volume method. Results of the average moisture content, average temperature, liquid flux, vapor flux, and moisture content and temperature distributions inside a lentil kernel during drying process (T=40 oC, RH=50% and v=0.3 m/s) were presented and analyzed.

An exact solution for arbitrarily rotating gaseous polytropes with index unity

Many gaseous planets and stars are rapidly rotating and can be approximately described by a polytropic equation of state with index unity. We present thefirst exact analytic solution, under the assumption of the oblate spheroidal shape, for an arbitrarily rotating gaseous polytrope withindexunityinhydrostaticequilibrium,givingrisetoitsinternalstructureandgravitational field. The new exact solution is derived by constructing the non-spherical Green’s function in terms of the oblate spheroidal wavefunction. We then apply the exact solution to a generic object whose parameter values are guided by the observations of the rapidly rotating star α Eridani with its eccentricity Eα = 0.7454, the most oblate star known. The internal structure and gravitational field of the object are computed from its assumed rotation rate and size. We also compare the exact solution to the three-dimensional numerical solution based on a finite-element method taking full account of rotation-induced shape change and find excellent agreement between the exact solution and the finite-element solution with about 0.001percent discrepancy.

Cross-type optical separation of elastic oblate capsules in a uniform flow

The dynamic behavior of an elastic capsule with an initially oblate spheroidal shape during cross-type optical separation was numerically investigated. The penalty immersed boundary method was adopted for the fluid-membrane interaction, and the optical force calculation was conducted by using the ray optics method including the ray-surface intersection algorithm. The oblate elastic capsule of b/a = 0.5 with different surface Young's moduli and different initial inclination angles was considered. The oblate capsule with higher surface Young's moduli was less deformed, and was more migrated for each initial inclination angle. Unlike the oblate rigid particle, the initially inclined capsules with moderate inclination angles were similarly migrated since the oblate elastic capsule was deformed during rotation near the laser beam axis. The oblate capsules can be separated according to the surface Young's modulus, except for nearly non-inclined capsules. As the fluid velocity decreased, the migration distance increased. The maximum deformation parameter was insensitive to the fluid velocity. Furthermore, a new dimensionless number (Sec) was introduced to predict the migration distance of the oblate elastic capsule.

Nanostructured ZnO thin films prepared by sol–gel spin-coating

ZnO thin films deposited on silica flat plates were prepared by spin-coating and studied by applying several techniques for structural characterization. The films were prepared by depositing different numbers of layers, each deposition being followed by a thermal treatment at 200°C to dry and consolidate the successive layers. After depositing all layers, a final thermal treatment at 450°C during 3h was also applied in order to eliminate organic components and to promote the crystallization of the thin films. The total thickness of the multilayered films – ranging from 40nm up to 150nm – was determined by AFM and FESEM. The analysis by GIXD showed that the thin films are composed of ZnO crystallites with an average diameter of 25nm circa. XR results demonstrated that the thin films also exhibit a large volume fraction of nanoporosity, typically 30–40vol.% in thin films having thicknesses larger than ∼70nm. GISAXS measurements showed that the experimental scattering intensity is well described by a structural model composed of nanopores with shape of oblate spheroids, height/diameter aspect ratio within the 0.8–0.9 range and average diameter along the sample surface plane in the 5–7nm range.