Oblate Spheroidal Shape Research Articles

A taxonomic revision of Rhizophora L. (Rhizophoraceae) in Thailand.

A taxonomic revision of Rhizophora L. (Rhizophoraceae) in Thailand is presented. Two species, R. apiculata Blume and R. mucronata Poir., are enumerated with updated morphological descriptions, illustrations and a taxonomic identification key, together with notes on distributions, habitats and ecology, phenology, conservation assessments, etymology, vernacular names, uses, and specimens examined. Three names in Rhizophora, are lectotypified: R. apiculata and two associated synonyms of R. mucronata (i.e., R. latifolia Miq. and R. macrorrhiza Griff.). R. longissima Blanco, a synonym of R. mucronata, is neotypified. All two Rhizophora species have a conservation assessment of Least Concern (LC). Based on the morphological identification, these two species can be distinguished from one another by the shape and width of the leaf laminae and the length of a terminal stiff point of the leaf laminae; the type and position of the inflorescences and the number of flowers per inflorescence; the character and color of the bracteoles; the presence or absence of the flower pedicels; the shape of the mature flower buds; the shape, color, and texture of the sepals; the shape, character, and the presence or absence of hairs of the petals; the number of stamens per flower; the size of the fruits; the color and size of the hypocotyls; the color and diameter of the cotyledonous cylindrical tubes; and the color of the colleters and exudate. The thick cuticles, sunken stomata, large hypodermal cells, and cork warts are adaptive anatomical features of leaves in Rhizophora that live in the mangrove environments. The pollen grains of Thai Rhizophora species are tricolporate, prolate spheroidal or oblate spheroidal shapes, small-sized, and reticulate exine sculpturing.

Analyzing the early impact dynamics of single droplets impacting onto wetted surfaces

Single droplet impacts onto thin wall-films are a common phenomenon in many applications. For sufficiently high impact velocities, the droplet impact process consists of three phases, i.e., initial contact stage, droplet deformation with radial momentum transfer inducing an upward rising lamella, and crown propagation. Here, we present the results of a combined numerical and experimental study focusing on the early dynamics of the impact process. Specifically, the effects of the initial droplet shape, wall-film thickness, and contact line motion are analyzed. Prior to impact, an oblate spheroidal droplet shape was observed. Using direct numerical simulation, we show that the droplet shape affects the impact dynamics only during the first two phases, as it is one of the key parameter influencing the correct prediction of the impact zone. The contact line propagation is described by a square-root-time dependence R¯CL=ατ for both, dry and wetted surfaces. On dry surfaces, the advancement of the contact line is determined by the rolling motion of the truncated droplet. On wetted surfaces, the value of the α-parameter is controlled by two concurrent effects, namely, rolling motion and wall-film inertia. For impact onto thin films, the rolling motion prevails. With increasing wall-film height, the droplet penetrates into the soft substrates and wall-film inertia becomes the controlling factor. These insights into the early impact dynamics on wetted surface are important for the formulation of a unified modeling approach.

Mass Modelling of Eggs Based on Shape Index Using Regression Analysis

This study was conducted to determine the correlation between the mass of eggs based on its geometrical dimensions characteristics such as length (L), width (W), geometric mean diameter (GMD), the first and second projection areas (PA1, PA2), criteria area (CAE), oblate spheroid volume (Vosp), measured volume (Vm) and shape index (SI). Based upon the SI, eggs were characterized as sharp (<72), normal (72 -76) and round (>76), respectively. For mass prediction, different classifications viz. dimension as 1st classification, projection area as 2nd classification, and volume as 3rd classification were considered. 1st classification (dimension), 2nd classification (projection area), and 3rd classification (volume) were considered. The analysis was executed using 33 linear regression models and the models were recommended by considering maximum coefficient of determination (R2) and minimum regression standard error (RSE). Based on the modelling analysis, 10 model equations based on the selected classifications were recommended for mass estimation. The findings of this investigation will be helpful for the researchers involved in the design and development of process equipments in the production and processing of eggs.

TinyLev acoustically levitated water: Direct observation of collective, inter-droplet effects through morphological and thermal analysis of multiple droplets

HypothesisUnderstanding the crystallization of atmospheric water can require levitation techniques to avoid the influence of container walls. Recently, an acoustic levitation device called the TinyLev was designed, which can levitate multiple droplets at room temperature. Proximal crystallization may affect droplet phase change and morphological characteristics. MethodologyIn this study, acoustically levitated pure water droplets were frozen individually and in pairs or triplets using a TinyLev device. Nucleation, bulk crystal growth, and melting were observed using digital and infrared cameras concurrently. FindingsInitially, the acoustic field forced the droplets into an oblate spheroid shape, though the counteracting force of the cooling stream caused them to circularize. Droplet geometry was thus the net result of streaming forces and surface tension at the acoustic boundary layer/air–liquid interface. Nucleation was determined to be neither homogeneous nor heterogeneous but secondary, and thus dependent on the cooling rate and not on the degree of supercooling. It was likely initiated by aerosolized ice particles from the air or from droplets that had already nucleated and broken up. The latter secondary ice production process resulted in multi-drop systems with statistically identical nucleation times. Notably, this meant that the presence of interfacial rupture at an adjacent droplet could influence the crystallization behaviour of another. After the formation of an initial ice shell around the individual droplets, dendritic protrusions grew from the droplet surface, likely seeded by the same ice particles that caused nucleation, but at a quasi-liquid layer. When freezing was complete, it was determined that the frozen core had undergone a volumetric expansion of 30.75%, compared to 9% for pure, sessile water expansion. This significantly greater expansion may have resulted from entrained air bubbles at the inner solid–liquid interface and oscillations at the moving phase boundary caused by changes in local acoustic forces. Soon after melting began, acoustic streaming, the buoyancy of the remaining ice, and convective currents caused by both an inner thermal gradient and thermocapillary effects along the air–liquid interface, all contributed to the droplet spinning about the horizontal axis.

STUDY OF SELF-SUPERPOSABLE LIQUID IN OBLATE SPHEROIDAL SHAPE

The paper studiesthe self-superposable motion of a liquid of a fluid which is incompressible in nature in oblate spheroidal shape. An incompressible fluid is defined as the fluid whose volume or density does not change with pressure. Thus, the main aim of this paper is to solve the basic equations of fluid dynamics in oblate spheroidal coordinates considering self-superposable nature of the fluid. The paper includes the study of nature of vorticity and irrotationality and has not considered the boundary conditions in theanalysis. Lastly, the paper determines the pressure distribution and the solutions contain a set of constants.

Forces and conservation laws for motion on our spheroidal Earth

We explore the forces and conservation laws that govern the motion of a hockey puck that slides without friction on a smooth, rotating, self-gravitating spheroid. The earth's oblate spheroidal shape (apart from small-scale surface features) is determined by balancing the gravitational forces that hold it together against the centrifugal forces that try to tear it apart. The earth achieves this shape when the apparent gravitational force on the puck, defined as the vector sum of the gravitational and centrifugal forces, is perpendicular to the earth's surface at every point on the surface. Thus, the earth's spheroidal deformations neutralize the centrifugal and gravitational forces on the puck, leaving only the Coriolis force to govern its motion. Motion on the spheroid therefore differs profoundly from motion on a rotating sphere, for which the centrifugal force plays a key role. Kinetic energy conservation reflects this difference: On a stably rotating spheroid, the kinetic energy is conserved in the rotating frame, whereas on a rotating sphere, it is conserved in the inertial frame. We derive these results and illustrate them using CorioVis software for visualizing the motion of a puck on the earth's spheroidal surface.

Self-assembling properties of ionisable amphiphilic drugs in aqueous solution

Hypothesis: Common amphiphilic drug molecules often have a more rigid nonpolar part than conventional surfactants. The rigidity is expected to influence the self-assembling properties and possibly give rise to aggregation patterns different from that of regular surfactants.Experiments: We have investigated self-assembling properties of the hydrochloride salts of adiphenine (ADP), pavatrine (PVT), and amitriptyline (AMT) at concentrations up to 50 wt% using small-angle x-ray scattering, dynamic light scattering, cryo-transmission electron microscopy, and surface tension measurements.Findings: All drugs form small micelles of oblate spheroidal shape at concentrations above the critical micelle concentrations (CMC). The micelles grow weakly in size up to about 20 wt%, where the aggregation number reaches a maximum followed by a slight decrease in size at higher drug concentrations. We observe a correlation between the decrease in micelle size at high concentrations and an increasing charge of the micelles, as the degree of ionization increases with increasing drug concentration and decreasing pH. In contrast to what has previously been reported, the aggregation behavior of all studied drugs resembles the closed association behavior of conventional surfactants with a short aliphatic chain as hydrophobic tail group i.e. the micelles are always small in size and lack a second CMC. CMC values were determined with surface tension measurements, including also lidocaine hydrochloride (LDC) and chlorpromazine hydrochloride (CHL).

Crystal Structure and Predominant Defects in CdS Quantum Dots Fabricated by the Langmuir-Blodgett Method.

The crystal structure and shape of the CdS quantum dots (QDs) obtained by the Langmuir-Blodgett method were studied by transmission electron microscopy, extended X-ray absorption fine structure spectroscopy (EXAFS), and ultraviolet spectroscopy. X-ray photoelectron spectroscopy (XPS) and stationary photoluminescence spectroscopy (PL) methods were used to determine the dominant surface defects. Initially synthesized QDs within the Langmuir-Blodgett film of fatty behenic acid have a cubic structure and oblate spheroid shape, while free-standing QDs obtained after the matrix evaporation have a wurtzite structure and sphere-like shape. QDs within the matrix demonstrate a wide PL band centered at 2.3 eV corresponding to defect-assisted radiative recombination; after the matrix annealing and passivation of the QD surface in an ammonia atmosphere, the PL spectrum demonstrates a high-intensity band-edge peak together with a low-intensity defect-assisted shoulder. It was established that sulfur (VS) vacancies are the dominating defects. A model of simultaneous band-edge and defect-assisted recombination through the VS level was proposed.

Spore characterisation and its taxonomic significance in ferns from Lagos State, Nigeria

The gradual disappearance of ferns due to biodiversity loss occasioned by anthropogenic activities and global climate change necessitated the need to document and study palynologically pteridophytes in Lagos State. Their peculiar habitat is fast declining in many urban centres of the world, including Nigeria. Previous studies in Nigeria mainly addressed their distribution, with limited reports on their morphology and systematic significance. Hence, we conducted a field survey and characterised the spore morphology of the encountered ferns in Lagos State, Nigeria, using light microscopy (LM) and scanning electron microscopy (SEM). We recorded nine species belonging to nine genera and five families. The studied species varied in spore size, shape, and ornamentation. Spores’ sizes ranged between 30 μm × 32 μm in Nephrolepis biserrata and 122 μm × 127 μm in Ceratopteris cornuta. Symmetrically, they were bilateral or radial, and ranged in size between very large, large, and medium. Despite marginal differences in polar to equatorial diameter ratios (P/E ratios), the oblate-spheroidal shape class was found to be a synapomorphic character. We observed relationships between the spore shape and the corresponding aperture type. SEM revealed different spore ornamentation types – tuberculate, canaliculate, rugate/rugulate, reticulate, verrucate, tuberculate, and echinate. Our findings propose the potential use of spore P/E ratio and SEM as taxonomic diagnostic tools in Pteridophyte systematics. However, further studies with more representative species are needed to evaluate the factors influencing spore morphology and its taxonomic significance. Overall, this study provides insights into the systematics of ferns in Lagos State and would aid fern identification in palynology and palaeopalynology.

Effects of anisotropy on absorption cross-section spectra of medium-sized spheroidal corundum particles

Context. It has been widely accepted that corundum particles condense in the atmospheres of oxygen-rich asymptotic giant branch stars and effectively produce an infrared emission feature at 13 μm. Laboratory experiments have predicted that these particles have the shape of oblate spheroids. Aims. We investigate the influence of the material anisotropy of uniaxial corundum on absorption cross section spectra of medium sized spheroidal particles in the infrared spectral region. Methods. We compared absorption cross-section spectra of the anisotropic corundum particles gained by finite-difference time-domain simulations to spectra calculated by a weighted sum approximation of the according fictive isotropic materials, with one material having the dielectric function of the a–b-plane and the other having the dielectric function of the c-axis of corundum. We carried out investigations for different axes ratios of the spheroids, particles volumes, and different geometries of the dielectric axes to the particle axes as well as to the polarization and propagation direction of the incident light. Results. We observed several effects attributed to anisotropy that are non-additive, so that they cannot be reproduced with the combined spectra of the isotropic materials. Conclusions. Care should be taken when calculating the corundum infrared spectrum with simpler approaches. When particle sizes above 1 μm are to be considered, the T-matrix formalism delivers correct band shifts and bulk modes for many, but not all bands. This remains true in orientation-averaged spectra and for particles in the 0.1 μm size range.

Use of Pollen Morphology Traits for Identifying Species of Centaurea L. Asteraceae in Kurdistan-Iraq

The polleniferous material of Centaurea taxa grow in Kurdistan-Iraq was collected. Samples were tested using scanning electron microscopy (SEM) and light microscopy (LM). In the polar view, pollen grain outlines are mostly triangular or triangular-circular. In equatorial view, the elliptic shape is common, while circulars or semicircular shapes are rare. The exine sculpture is scabrate, and the tectum is perforate. Number of sculpture microspinules/ µm², and their heights together with the number of wall perforations provide significant characters for taxa delimitation. Pollen grains of all species are of medium size, very few of some species pollen are larger or smaller in size. Species producing subprolate pollen shape is common, while oblate spheroidal and Prolate spheroidal shapes are less common. The principal component analysis and the discriminant analysis can recognize 65.478% and 87.54% of the total variability respectively; moreover, the discriminant function can correctly classify 125 or 78.125% out of 160 observations for pollen traits.

Dynamics of bubbles rising in pseudo-2D bubble column: Effect of confinement and inertia

2D Rectangular columns, formed within a thin gap between two enclosed parallel plates, are often used in visualisation and CFD studies of multiphase flows. In this study, a numerical analysis is performed on the dynamics of a bubble rising in such setup (D = 5–7 mm, Re ≈ 1000–2000), with the aim of determining the effect of the size of the gap (h) on the velocity field around it. For most cases, the bubble adopts an oblate spheroidal shape, with chaotic rise behaviour and continual fluctuations in both aspect ratio, orientation, and velocity. The bubble aspect ratio generally decreases with increasing level of confinement, because of increased level of resistance provided by the walls. With increasing Reynolds number, however, the bubble (D = 7 mm, h/D = 1) is found to display a more elongated oblate spheroidal shape and a rise behaviour that is largely rectilinear. This change in behaviour has been attributed towards severe disruptions in the development of toroidal vortex formation at the walls, confining the formation of hairpin vortices towards the side interface of the bubble at the centreline of the column. This prevents the development of large-scale fluctuations and confines the path oscillation of the bubble towards high-frequency fluctuations. Further, the formation of a region of recirculating flow is also evident, as a result of rapid detachment of vortices at the bubble equator. Intense fluctuation in velocity in the horizontal direction parallel to the wall is developed, and the dissipation in this fluctuation, as well as in the time-averaged velocity below the bubble, is found to occur more gradually than in the case of columns with larger gaps.

Collisional formation of top-shaped asteroids and implications for the origins of Ryugu and Bennu

Asteroid shapes and hydration levels can serve as tracers of their history and origin. For instance, the asteroids (162173) Ryugu and (101955) Bennu have an oblate spheroidal shape with a pronounced equator, but contain different surface hydration levels. Here we show, through numerical simulations of large asteroid disruptions, that oblate spheroids, some of which have a pronounced equator defining a spinning top shape, can form directly through gravitational reaccumulation. We further show that rubble piles formed in a single disruption can have similar porosities but variable degrees of hydration. The direct formation of top shapes from single disruption alone can explain the relatively old crater-retention ages of the equatorial features of Ryugu and Bennu. Two separate parent-body disruptions are not necessarily required to explain their different hydration levels.

Effect of non-spherical particles on burning behavior during aluminum combustion

The shape of an aluminum particle is assumed to be spherical or an equivalent sphere during the combustion process. Such an assumption lacks objectivity and leads to unreasonable approximations of burning efficiency and performance. To investigate the influence of non-spherical particles on burning behavior, this study focused on a theoretical and experimental investigation of the combustion of nanoscale aluminum ellipsoidal particles. Models for prolate and oblate spheroids in aluminum combustion were established to explore combustion properties such as mass release rate, linear burning rate, burning rate, and burnout time. To validate the theoretical results, combustion experiments were conducted on three samples. Reasonable agreement between the results of numerical simulation and experimental findings was obtained in terms of the particle burning characteristics. It was found that particle morphology (such as prolate or oblate spheroid shape) and size play a significant role in the combustion performance of nanosized aluminum particles.

Orbit classification in the Copenhagen problem with oblate primaries

AbstractThis article aims to numerically investigate the orbital dynamics of the planar circular‐restricted three‐body problem, where the two primary bodies have equal masses and an oblate spheroid shape. By numerically integrating several large sets of initial conditions of both retrograde and prograde orbits, we classify them into three main categories: (a) bounded (regular or chaotic), (b) escaping, and (c) collision orbits. We reveal the motion of the test particle by presenting color‐coded diagrams, where the initial conditions are mapped to the orbit type and studied as a function of the total orbital energy (or equivalently of the Jacobi constant) as well as of the oblateness coefficient. Our numerical results are compared with related previous ones, corresponding to the classical version of the planar‐restricted three‐body problem. The presented outcomes have practical physical applications as they can be used for modeling the motion of a massless test particle in the gravitational field of a binary system of two oblate exoplanets.

Pollen micromorphological analysis of tribe Acacieae (Mimosaceae) with LM and SEM techniques.

The morphology of pollen grains of the 06 species of tribe Acacieae (Mimosaceae) belonging to one genus were investigated using scanning electron microscopic (SEM) and light microscopic (LM) approach. Lactic acid acetolysis method was used for (LM) while non-acetolysis for (SEM). The species were examined for the both qualitative and quantitative palynological features. Qualitatively the pollen was studied for the shape, exine sculpturing, pollen shape, and pollen type. Oblate spheroidal shape of pollen was observed in Accacia modesta. Subprolate shape in Accaca nilotica. In Accacia farnesiana, prolate pollen was examined while prolate spheroidal in Acacia tortilis and spheroidal pollen grains were studied in Acacia catechu, respectively. Pollen exine sculpturing of the studied tribe possesses novel variation. Foveolate, reticulate, foveolate-psilate, faint reticulate, fossulate, perforate, and scrabate exine sculpturing were noticed. Colpi were absent in all species. Excessive variation was observed in both qualitative and quantitative character of pollen. SPSS software was use for the quantitative measurement of the pollen grains. The current study will be helpful for the identification of the problematic species and phylogenetic studies of family Mimosaceae.

Viability estimation and morphological characterization of pollen Datura suaveolens Willd (Solanaceae)

The species Datura suaveolens W. belongs to the family Solanaceae. It is a natural shrub species of the Himalayas, is widely distributed in South America and Brazil. In Brazil it is cultivated for medicinal and ornamental purposes. The objective of this work was to perform the morphological characterization and verify the pollen viability of the D. suaveolens species by means of colorimetric tests in order to determine the best dye for the species. Flower buds of Datura suaveolens were collected with occurrence in the municipality of Alta Floresta, MT. The experiment was carried out at the Cytogenetic and Tissue Culture Laboratory at the State University of Mato Grosso, Alta Floresta University Campus. For the estimation of pollen viability, three different dyes were evaluated: lugol, Alexander’s reactive and acetic orcein. For the pollen morphology, forty pollen grains stained with 3% safranin were analyzed. The morphological parameters analyzed were: equatorial diameter, polar diameter, size and shape and opening of the pollen grains. The diameter measurements were measured with the help of ImageJ software. The Alexander’s reactive is the most recommended colorimetric method for the pollen viability analysis of Datura Suaveolens because it revealed the highest average of viable pollen and presents a better visual distinction between viable and non-viable pollen. The Datura Suaveolens species has large pollen grains with Oblate-Spheroidal shape, the opening of the pollen is 3-pore type. The mean polar diameter of the species is 70.99 μm and the equatorial diameter is 67.94 μm.

Shape evolution and bubble formation of acoustically levitated drops

In this study, we investigated the shape evolution and bubble formation of acoustically levitated drops upon increasing the sound intensity. Here, a levitated liquid drop evolves progressively from an oblate spheroidal shape to a flattened film to a thin bowl-shaped film, eventually forming a closed bubble. Through systematic experiments, numerical simulation, and scaling analysis, we demonstrate that the buckled geometry of the liquid film can drastically enhance the suction effect of acoustic radiation pressure at its rim, forming a significant pressure gradient inside the film which causes an abrupt area expansion and bubble formation. Our results provide the mechanical origin responsible for the shape evolution and bubble formation of acoustically levitated drops, and highlight the role of buckled geometry in the levitation and manipulation of liquid films in an ultrasound field.

A simple explicit homogenization solution for the macroscopic elastic response of isotropic porous elastomers

An approximate homogenization solution is put forth for the effective stored-energy function describing the macroscopic elastic response of isotropic porous elastomers comprised of incompressible non-Gaussian elastomers embedding equiaxed closed-cell vacuous pores. In spite of its generality, the solution — which is constructed in two successive steps by making use first of an iterative technique and then of a nonlinear comparison medium method — is fully explicit and remarkably simple. Its key theoretical and practical features are discussed in detail and its accuracy is demonstrated by means of direct comparisons with novel computational solutions for porous elastomers with four classes of physically relevant isotropic microstructures wherein the underlying pores are: (i) infinitely polydisperse in size and of abstract shape, (ii) finitely polydisperse in size and spherical in shape, (iii) monodisperse in size and spherical in shape, and (iv) monodisperse in size and of oblate spheroidal shape.

Spall strength dependence on grain size and strain rate in tantalum

We examine the effect of grain size on the dynamic failure of tantalum during laser-shock compression and release and identify a significant effect of grain size on spall strength, which is opposite to the prediction of the Hall-Petch relationship because spall is primarily intergranular in both poly and nanocrystalline samples; thus, monocrystals have a higher spall strength than polycrystals, which, in turn, are stronger in tension than ultra-fine grain sized specimens. Post-shock characterization reveals ductile failure which evolves by void nucleation, growth, and coalescence. Whereas in the monocrystal the voids grow in the interior, nucleation is both intra - and intergranular in the poly and ultra-fine-grained crystals. The fact that spall is primarily intergranular in both poly and nanocrystalline samples is a strong evidence for higher growth rates of intergranular voids, which have a distinctly oblate spheroid shape in contrast with intragranular voids, which are more spherical. The length of geometrically-necessary dislocations required to form a grain-boundary (intergranular) void is lower than that of grain-interior (intragranular) void with the same maximum diameter; thus, the energy required is lower. Consistent with prior literature and theory we also identify an increase with spall strength with strain rate from 6 × 106 to 5 × 107 s−1. Molecular dynamics calculations agree with the experimental results and also predict grain-boundary separation in the spalling of polycrystals as well as an increase in spall strength with strain rate. An analytical model based on the kinetics of nucleation and growth of intra- and intergranular voids and extending the Curran-Seaman-Shockey theory is applied which shows the competition between the two processes for polycrystals.