Theoretical Analysis of Thin Curved Rod Displacements V. P. Lugovoi1)

The paper presents a comparative theoretical analysis of the movements of the curved rods of various curvature forms, which can be applied as tools for ultrasonic treatment of holes in fragile materials. It has been shown that the traditional processing of holes by an ultrasonic method is based on the use of straight rods, in which the amplitudes of displacements on the working – free end corresponds to the value of displacements at the point of its attachment to the ultrasonic oscillation concentrator. Supplementing the configuration of a straight rod with a curvilinear shape in the form of a circular arc or a spiral twisted by one turn will allow obtaining additional displacements caused by the elastic properties of a section with a curved shape. The paper considers several calculated schemes of a curvilinear rod bounded by angles j equal to p/2, p and 2p, fferent direction of the external force action. The obtained results have shown that an increase in the circular arc angle leads to a corresponding increase in the elastic displacement index of the rod free end. In this case, the total displacements of the rod free end will be made from displacements caused by vibrations of the acoustic system and the displacements of a curved thin rod from an external force. Calculations have established that the magnitude of the elastic displacements of curved rods is influenced by the shape and magnitude of the angle, the direction of the external force, the radius of curvature, the rigidity of the cross section. The considered schemes of thin rods with curvilinear sections can find practical application in ultrasonic oscillatory systems for processing small-diameter holes in fragile materials. This increases the intensity of tool oscillations and improves the process performance.

Calculation of the Shaping of a Space Umbrella Antenna During Strong Bending of Radial Rods Connected Along Parallels by Tensile Cables

Abstract— A cyclically symmetric umbrella antenna is considered, the frame of which consists of flexible inextensible radial rods connected in nodes along parallels by tensile cables. In the initial transport position, the multilink rods are packed in packages oriented in the direction of the system axis. After the packing ties are removed, the rods are deployed in radial planes under the action of elastic springs connecting the links, and are fixed in rectilinear positions at a given angle with respect to the axis, at which all cables connecting the same type of rod nodes take the form of regular polygons, while remaining loose. Further, under the action of the force of a damping hydraulic cylinder with pre-compressed springs, the root parts of all rods are slowly turned to the stops. In the final position, the radial rods, connected at the nodes by tensioned cables, take a curved shape. The tensile stiffnesses of the cables are determined so that the radial and axial coordinates of the nodes of the curved rods coincide with the coordinates of the points of the given surface of revolution. A model of strong bending of a flexible inextensible rod is constructed taking into account the unknown radial reactions of tensioned cables acting on it at the nodes. The links of the rod are considered as “cantilever” elements connected in series at the nodes in local coordinate systems, which can make large displacements and turns. The bending of each element is described by two specified functions, the shrinkage of the element due to bending is taken into account in a quadratic approximation. The obtained nonlinear deformation equations of the system, taking into account the geometric connections at the nodes, are solved by the method of successive approximations with respect to the unknown reactions of the cables. The obtained values of the reactions are then used to determine the required tensile stiffness of the cables at the given coordinates of the nodes. As an example of the calculation, a parabolic antenna is considered for various numbers of radial rods and components of links. The estimates of the accuracy of the proposed computational model of the antenna shaping are carried out.

‘Candidatus Xiphinematincola pachtaicus' gen. nov., sp. nov., an endosymbiotic bacterium associated with nematode species of the genus Xiphinema (Nematoda, Longidoridae)

An intracellular bacterium, strain IAST, was observed to infect several species of the plant-parasitic nematode genus Xiphinema (Xiphinema astaregiense, Xiphinema incertum, Xiphinema madeirense, Xiphinema pachtaicum, Xiphinema parapachydermum and Xiphinema vallense). The bacterium could not be recovered on axenic medium. The 16S rRNA gene sequence of IAST was found to be new, being related to the family Burkholderiaceae, class Betaproteobacteria. Fungal endosymbionts Mycoavidus cysteinexigens B1-EBT (92.9 % sequence identity) and ‘Candidatus Glomeribacter gigasporarum’ BEG34 (89.8 % identity) are the closest taxa and form a separate phylogenetic clade inside Burkholderiaceae. Other genes (atpD, lepA and recA) also separated this species from its closest relatives using a multilocus sequence analysis approach. These genes were obtained using a partial genome of this bacterium. The localization of the bacterium (via light and fluorescence in situ hybridization microscopy) is in the X. pachtaicum females clustered around the developing oocytes, primarily found embedded inside the epithelial wall cells of the ovaries, from where they are dispersed in the intestine. Transmission electron microscopy (TEM) observations supported the presence of bacteria inside the nematode body, where they occupy ovaries and occur inside the intestinal epithelium. Ultrastructural analysis of the bacterium showed cells that appear as mostly irregular, slightly curved rods with rounded ends, 0.8–1.2 µm wide and 2.5–6.0 µm long, possessing a typical Gram-negative cell wall. The peptidoglycan layer is, however, evident only occasionally and not detectable by TEM in most cells. Another irregularly occurring shell surrounding the endosymbiont cells or the cell clusters was also revealed, probably originating from the host cell membrane. Flagella or spore-like cells do not occur and the nucleoid is diffusely distributed throughout the cell. This endosymbiont is transmitted vertically through nematode generations. These results support the proposal of IAST as a new species, although its obligate intracellular and obligate endosymbiont nature prevented isolation of a definitive type strain. Strain IAST is therefore proposed as representing ‘Candidatus Xiphinematincola pachtaicus’ gen. nov., sp. nov.

Sinanaerobacter Chloroacetimidivorans Sp. Nov., An Obligate Anaerobic Bacterium Isolated From Anaerobic Sludge

An obligate anaerobic bacterial strain (BAD-6T) capable of degrading acetochlor and butachlor was isolated from an anaerobic acetochlor-degrading reactor. Cells were Gram-positive, straight to gently curved rods with flagella. The major fermentation products in peptone-yeast (PY) broth were acetate and butyrate. The optimum temperature and pH for growth was 30 °C and 7.2−7.5, respectively. The major cellular fatty acids (>10%) were C14:0 FAME, C16:0 FAME and cyc-9,10-C19:0 DMA. Genome sequencing revealed a genome size of 4.80 Mb, a G+C content of 43.6 mol% and 4741 protein-coding genes. The most closely related described species on the basis of 16S rRNA gene sequences was Anaerovorax odorimutans NorPutT in the order Clostridiales of the class Clostridia with sequence similarity of 94.9 %. The nucleotide identity (ANI) value and digital DNA–DNA hybridization (dDDH) between the genomes of strain BAD-6T and Ana. odorimutans NorPutT are 70.9% and 15.9%, respectively. Based on the distinct differences in phylogenetic and phenotypic characteristics between strain BAD-6T and related species, Sinanaerobacter chloroacetimidivorans gen. nov., sp. nov. is proposed to accommodate the strain. Strain BAD-10T is the type strain (= CCTCC AB 2021092T = KCTC 72521T).

Determination of effective stiffness properties of multilayered composite beams

Starting from a Cosserat-type model for curved rods, we derive analytical expressions for the effective stiffness coefficients of multilayered composite beams with an arbitrary number of layers. For this purpose, we employ the comparison with analytical solutions of some bending, torsion, and extension problems for three-dimensional beams and rods. The layers of the composite beam consist of different orthotropic or isotropic non-homogeneous elastic materials. We apply the obtained general formulas to calculate exact analytical solutions of some beam problems and compare them with corresponding results of numerical simulations. The numerical study shows a wide range of validity and applicability of the obtained formulas.

A generalized density-modulated twist-splay-bend phase of banana-shaped particles

In 1976, Meyer predicted that bend distortions of the nematic director field are complemented by deformations of either twist or splay, yielding twist-bend and splay-bend nematic phases, respectively. Four decades later, the existence of the splay-bend nematic phase remains dubious, and the origin of these spontaneous distortions uncertain. Here, we conjecture that bend deformations of the nematic director can be complemented by simultaneous distortions of both twist and splay, yielding a twist-splay-bend nematic phase. Using theory and simulations, we show that the coupling between polar order and bend deformations drives the formation of modulated phases in systems of curved rods. We find that twist-bend phases transition to splay-bend phases via intermediate twist-splay-bend phases, and that splay distortions are always accompanied by periodic density modulations due to the coupling of the particle curvature with the non-uniform curvature of the splayed director field, implying that the twist-splay-bend and splay-bend phases of banana-shaped particles are actually smectic phases.

Maricaulis alexandrii sp. nov., a novel dimorphic prosthecate and active bioflocculants-bearing bacterium isolated from phycosphere microbiota of laboratory cultured highly-toxic Alexandrium catenella LZT09

An aerobic, Gram-stain-negative, straight or curved rods, prosthecate bacterium designated as LZ-16-1T was isolated from phycosphere microbiota of highly-toxic and laboratory cultured dinoflagellate Alexandrium catenella LZT09. This new isolate produces active bioflocculanting exopolysaccharides (EPS). Cells were dimorphic with non-motile prostheca, or non-stalked and motile by a single polar flagellum. Growth occurred at 10-40 °C, pH 5–9 and 1–8 % (w/v) NaCl, with optimum growth at 25 °C, pH 7–8 and 2-4 % (w/v) NaCl, respectively. Phylogenetic analysis based on 16S rRNA indicated that strain LZ-16-1T was affiliated to the genus Maricaulis, and closely related to Maricaulis parjimensis MCS 25T (99.48%) and M. virginensis VC-5T (99.04%),. However, based on genome sequencing and phylogenomic calculations, the average nucleotide identity (ANI) and digtal DNA-DNA genome hybridization (dDDH) values between the two strains were only 85.0 and 20.9%, respectively. Strain LZ-16-1T owned Q-10 as predominant isoprenoid quinone; summed feature 8, C16:0, C17:0, C18:0, C18:1 ω9c and summed feature 9 as dominant fatty acids; and sulfoquinovosyl diacylglycerol, glycolipids and unidentified phospholipid as major polar lipids. The genomic DNA G+C content is 63.6 mol%. Physiological and chemotaxonomic characterization further confirmed the distinctiveness of strain LZ-16-1T from other Maricaulis members. Thus, strain LZ-16-1T represents a novel species of the genus Maricaulis, for which the name Maricaulis alexandrii sp. nov. (type strain LZ-16-1T=KCTC 72194T=CCTCC AB 2019006T) is proposed .

ELASTIC BENDING OF A DRILL STRING IN AN ELLIPTICAL WELL WITH GEOMETRIC IMPERFECTIONS

The problem is posed of determining the resistance forces and internal forces in the drill string during drilling and when performing tripping operations in a curved well. The object of the study is the geometry of the centerline of deep inclined well trajectories. The aim of the work is to formulate and solve new problems of structural mechanics about nonlinear deformation of drill strings in directional wells. To study the mechanics of elastic bending of drill strings in directional wells, the methods of structural mechanics of flexible curved rods were used; methods of differential geometry and theory of surfaces; numerical Runge-Kutta method. The study of the influence of geometric imperfections of the borehole centerline on the forces of contact interaction between the drill string and the borehole wall has been carried out. The case is considered when geometric imperfections have the form of a localized spiral of variable radius. KEY WORDS: OIL AND GAS WELLS, CURVED TRAJECTORY, DRILLING COLUMN, RESISTANCE FORCES.