Circumferential Polarization Research Articles

Mutual influence of electrical, mechanical and acoustic fields under the radiation of sound by circular systems with screen, formed from cylindrical piezoceramic radiators

With the help of coupled fields method in multiply connected regions, we obtained analytical relations describing the physical fields of cylindrical piezoceramic radiators with circumferential polarization, which are part of cylindrical systems with a screen in the internal cavity. Based on the obtained relationships, quantitative estimates of the parameters of the electric, mechanical, and acoustic fields of the radiatos are performed when operating in circular systems with a screen, the analysis of which revealed the degree of influence of the fields on each other.

О КОЛЕБАНИЯХ ПЬЕЗОКЕРАМИЧЕСКОГО ЦИЛИНДРА С ОКРУЖНОЙ ПОЛЯРИЗАЦИЕЙ

The paper deals with of the problem of radial vibrations of a piezoceramic cylinder with circumferential polarization taking into account rheology. The piezoelectric characteristics of the cylinder are functions of the radial coordinate. The cylinder is considered as a piecewise homogeneous electroelastic body consisting of individual prisms. Assuming that the sectioned cylinder is infinitely long and there are no axial deformations in it, boundary value problems on the plane deformation of infinitely long prisms are constructed. In the special case, when all prisms of the sectioned cylinder are in identical conditions of electric loading and external mechanical loads are absent, the boundary problem for the cylinder reduces to the boundary problem for a separate prism. Rheological properties were modeled within the framework of the correspondence principle by replacing the material characteristics with complex moduli-functions of the vibration frequency. A comparison of the concept of complex modules with the widespread linear frequency approximation of the corresponding functions is performed. The solution of the problem was based on the method of shooting. The results of computational experiments on the determination of the amplitude-frequency characteristics for some laws of material inhomogeneity are presented. A series of computational experiments for various inhomogeneity laws and for a different set of initial data is performed, which made it possible to analyze the dependence of the resonant frequencies on the laws of variation of physical characteristics and rheology. A method for reconstructing of the inhomogeneity laws from information on the values of dimensionless functions-radial displacement and radial stress in a certain set of points inside the region using spline approximations is performed. The results of computational experiments have shown sufficient effectiveness of the proposed method.

The properties of mechanical fields of shielded sonar radiators with power structure depending on parameters of shield

The numerical analysis of mechanical fields of cylindrical antennas formed of cylindrical radiator with power structure, which formed of piezoceramic shell with a circumferential polarization and acoustically soft flat shield which are non closed circumferential shell with finite thickness was obtained. Comparative analysis of the frequency properties of radiators allowed to establish a number of subtle effects in the formation of mechanical fields of shielded radiators depending on the type of their structure and parameters of their shields. References 7, figures 5.

Paramecium tetraurelia basal body structure.

Paramecium is a free-living unicellular organism, easy to cultivate, featuring ca. 4000 motile cilia emanating from longitudinal rows of basal bodies anchored in the plasma membrane. The basal body circumferential polarity is marked by the asymmetrical organization of its associated appendages. The complex basal body plus its associated rootlets forms the kinetid. Kinetids are precisely oriented within a row in correlation with the cell polarity. Basal bodies also display a proximo-distal polarity with microtubule triplets at their proximal ends, surrounding a permanent cartwheel, and microtubule doublets at the transition zone located between the basal body and the cilium. Basal bodies remain anchored at the cell surface during the whole cell cycle. On the opposite to metazoan, there is no centriolar stage and new basal bodies develop anteriorly and at right angle from the base of the docked ones. Ciliogenesis follows a specific temporal pattern during the cell cycle and both unciliated and ciliated docked basal bodies can be observed in the same cell. The transition zone is particularly well organized with three distinct plates and a maturation of its structure is observed during the growth of the cilium. Transcriptomic and proteomic analyses have been performed in different organisms including Paramecium to understand the ciliogenesis process. The data have incremented a multi-organism database, dedicated to proteins involved in the biogenesis, composition and function of centrosomes, basal bodies or cilia. Thanks to its thousands of basal bodies and the well-known choreography of their duplication during the cell cycle, Paramecium has allowed pioneer studies focusing on the structural and functional processes underlying basal body duplication. Proteins involved in basal body anchoring are sequentially recruited to assemble the transition zone thus indicating that the anchoring process parallels the structural differentiation of the transition zone. This feature offers an opportunity to dissect spatio-temporally the mechanisms involved in the basal body anchoring process and transition zone formation.

Centrosome RNA: A Molecular Basis for Non-Equivalence of Triplets in Centrioles and Centrosomes?

Works have been published about RNA in centrioles, basal bodies and centrosomes but the issue has never been faced and examined in depth. Indeed RNA may really represent the informational molecule that turns the sophisticated architecture of these organelles into highly directional organizing centers: RNA may be the Molecular Basis for Non-Equivalence of the centriolar circumferential polarity and the foundation of chirality of centrioles, the most probable organizers of bilateral symmetry in Metazoa.

Electrical properties of cylindrical piezoceramic emitters with power and compensated design with circumferential polarization

Based on the common technical positions, obtained extensive numerical data on the electrical properties of cylindrical piezoceramic emitters with compensated and power design. On its base, was found quantitative relationship between electric current module, active and reactive components of the electrical resistance of these emitters and the type of used polarization, the physical parameters of different formulations of the piezoceramic shell emitters, the geometrical dimensions of the emitter design and physical characteristics of the medium filling their internal cavity. Comparative analysis of the obtained data allowed us to establish a few of subtle effects in the behavior of the electric fields of this type emitters.Reference 8, figures 10.

Physical fields of hydroacoustic antenna consisting of the angle of the horn and the piezoceramic transducer with a circumferential po-larization

Considered hydroacoustic antenna consisting of the angle of the horn reflector soft type and placed in his mouth cylindrical piezoceramic transducer with a circumferential polarization. Thus the design of the transmitter can be power or compensating type.The problem was solved by methods related fields and analytical expressions describing the physical fields of the horn antenna – acoustic, mechanical and electrical. These fields are presented in the form of expansions in series of the wave functions of the circular cylindrical coordinate system with unknown expansion coefficients which are determined from the boundary conditions and the matching conditions at the interfaces between fields areas. Solution is reduced to an infinite system of linear algebraic equations.References. 4, Fig. 2.

The Spherical Reference System of Metazoan Cells

Centrioles, through their 9-fold symmetry, circumferential polarity (non-equivalence of their 9 triplets) and orthogonal arrangement, may build a biological interface tool that recognizes topogenic molecular signals and translates them by delivering targeted complexes (polarity and adhesion factors, transmembrane receptors, mRNAs) into their expected locations, precisely connecting, like a wiring device, each targeted complex with the corresponding correctly-oriented microtubule. Through this tool (the centrosome and its aster of robust microtubules) DNA can draw, build and “label” an intrinsic finely tuned 3D grid line of the cell. Counterclockwise circumferential polarity of the mother centriole is the natural candidate to be the molecular basis of Metazoan bilateral symmetry. The following analysis aims to support the idea that there are well known molecular mechanisms capable of realizing the circumferential non-equivalence of the triplets and the reversal orientation of mother centriole rotational polarity: starting from experimental facts (the requirements of a spherical reference system based on two orthogonal protractors show a surprising correspondence with the evidence emerging from numerous experimental studies on centrioles and centrosomes), some plausible hypotheses are formulated (and logical consequent considerations deducted) to show that the proposed geometrical main role of the centrosome has robust and solid biophysical and biochemical foundations.

A resonance-bending mode magnetoelectric-coupling equivalent circuit

Magnetoelectric (ME) coupling equivalent circuits for L-T (longitudinal magnetization and transverse polarization), L-L (longitudinal magnetization and longitudinal polarization), and C-C (circumferential magnetization and circumferential polarization) modes have been developed for laminated ME composites in prior reports. Here, we report the modeling of laminated magnetostrictive/piezoelectric bilayer composites operated in bending mode. By introducing the concept of mechanical voltage and mechanical current, a bending-mode ME coupling equivalent circuit was developed, which is useful to predict the ME coefficients in the region around the resonance frequency.

Wave characteristics in functionally graded piezoelectric hollow cylinders

Based on linear three-dimensional piezoelasticity, the Legendre orthogonal polynomial series expansion approach is used for determining the wave characteristics in hollow cylinders composed of the functionally graded piezoelectric materials (FGPM) with open circuit. The displacement and electric potential components, expanded in a series of Legendre polynomials, are introduced into the governing equations along with position-dependent material constants so that the solution of the wave equation is reduced to an eigenvalue problem. Dispersion curves for FGPM and the corresponding non-piezoelectric hollow cylinders are calculated to show the piezoelectric effect. The influence of the ratio of radius to thickness is discussed. Electric potential and displacement distributions are used to show the piezoelectric effect on the flexural torsional mode. The influence of the polarizing direction on the piezoelectric effect is illustrated. For the radial and axial polarization, the piezoelectric effect reacts mostly on the longitudinal mode. For circumferential polarization, the piezoelectric effect reacts mostly on the torsional mode. In the FGPM hollow cylinder, piezoelectricity can weaken the guided wave dispersion.

Structural inheritance in Paramecium: ultrastructural evidence for basal body and associated rootlets polarity transmission through binary fission

One main difference between basal bodies and centrioles resides in the expression of their polarity: centrioles display a structural nine-fold radial symmetry, whereas basal bodies express a circumferential polarity, thanks to their asymmetric set of rootlets. The origin of this polarity during organelle duplication still remains under debate: is it intrinsic to the nine-fold structure itself (i.e. the nine microtubular triplets are not equivalent) or imposed by its immediate environment at time of assembly? We have reinvestigated this problem using the Ciliate Paramecium, in which the pattern of basal body duplication is well known. In this cell, all basal bodies produced within ciliary rows appear immediately anterior to parental ones. Observations on cells fixed with the tannic acid protocol suggest that, to be competent for basal body assembly, parental basal bodies have to be individually associated with a complete set of rootlets (monokinetid structure). During pro-basal body assembly, full microtubular triplets were detected according to a random circumferential sequence; during the whole process, the new basal body and its associated rootlets maintained structural relations with the parental monokinetid structure by way of specific links. These results strongly suggest that basal body and associated rootlets (kinetid) polarity is driven by its immediate environment and provide a basis for the structural heredity property observed by Sonneborn some decades ago.

Polarimetry and Unification of Low-Redshift Radio Galaxies

We have made high-quality measurements of the polarization spectra of 13 FR II radio galaxies and taken polarization images for 11 of these with the Keck telescopes. Seven of the eight narrow-line radio galaxies (NLRGs) are polarized, and six of the seven show prominent broad Balmer lines in polarized light. The broad lines are also weakly visible in total flux. Some of the NLRGs show bipolar regions with roughly circumferential polarization vectors, revealing a large reflection nebula illuminated by a central source. Our observations powerfully support the hidden quasar hypothesis for some NLRGs. According to this hypothesis, the continuum and broad lines are blocked by a dusty molecular torus, but can be seen by reflected, hence polarized, light. Classification as a NLRG, a broad-line radio galaxy (BLRG), or a quasar therefore depends on orientation. However, not all objects fit into this unification scheme. Our sample is biased toward objects known in advance to be polarized, but the combination of our results with the 1996 findings of Hill, Goodrich, and DePoy show that at least six out of a complete, volume and flux-limited sample of nine FR II NLRGs have broad lines, seen either in polarization or P{alpha}.The BLRGs in ourmore » sample range from 3C 382, which has a quasar-like spectrum, to the highly reddened IRAS source FSC 2217+259. This reddening sequence suggests a continuous transition from unobscured quasar to reddened BLRG to NLRG. Apparently the obscuring torus does not have a distinct edge. The BLRGs have polarization images that are consistent with a point source broadened by seeing and diluted by starlight. We do not detect extended nebular or scattered emission, perhaps because it is swamped by the nuclear source. Our starlight-corrected BLRG spectra can be explained with a two-component model: a quasar viewed through dust and quasar light scattered by dust. The direct flux is more reddened than the scattered flux, causing the polarization to rise steeply to the blue. Strong rotations of the electric vector position angle across H{alpha} in 3C 227 and 3C 445 may be explained by systematic orbital motions in an equatorial broad-line region. (c) (c) 1999. The American Astronomical Society.« less

Polarities of the centriolar structure: Morphogenetic consequences

Centrioles and basal bodies are two versions of the same conserved eukaryotic organelle and share two remarkable properties: nine-fold symmetry of their microtubular shaft and capacity to generate a new organelle in a fixed geometrical relationship to the mother organelle. It can thus be postulated that what is true for basal bodies is likely to be true also for centrioles. While the functions of centrioles are difficult to dissect, the functions of basal bodies are easier to approach. Over more than two decades, studies on protists have led to the notion that ciliary and flagellar basal bodies display polarities, not only a proximo-distal polarity, like in centrioles, but also a circumferential polarity accorded to the polarities of the cell and of its cytoskeleton. The major cytological and genetical data, mainly of Chlamydomonas, Paramecium and Tetrahymena, which support the notion that the microtubule triplets of basal bodies are non-equivalent, are reviewed. The morphogenetic implications of this circumferential anisotropy, perpetuated through the process of basal body duplication itself, are discussed. The question is raised of the possibility that centrioles also display a circumferential polarity, like basal bodies, and whether at least certain of their functions depend on such asymmetries.

Some effects of the circumferential polarization of current on thin-wire antennas

Although small, the circumferential polarization of current on thin-wire antennas has a very substantial effect on the circumferential variation of the longitudinal component of current.