Hollow Cylindrical Structures Research Articles

Guided wave propagation and mode differentiation in hollow cylinders with viscoelastic coatings

Guided wave propagation theories have been widely explored for about one century. Earlier theories on single-layer elastic hollow cylinders have been very beneficial for practical nondestructive testing on piping and tubing systems. Guided wave flexural (nonaxisymmetric) modes in cylinders can be generated by a partial source loading or any nonaxisymmetric discontinuity. They are especially important for guided wave mode control and defect analysis. Previous investigations on guided wave propagation in multilayered hollow cylindrical structures mostly concentrate on the axisymmetric wave mode characteristics. In this paper, the problem of guided wave propagation in free hollow cylinders with viscoelastic coatings is solved by a semianalytical finite element (SAFE) method. Guided wave dispersion curves and attenuation characteristics for both axisymmetric and flexural modes are presented. Due to the fact that dispersion curve modes obtained from SAFE calculations are difficult to differentiate from each other, a mode sorting method is established to distinguish modes by their orthogonality. Theoretical proof of the orthogonality between guided wave modes in a viscoelastic coated hollow cylinder is provided. Wave structures are also calculated and discussed in view of wave mechanics in multilayered cylindrical structures containing viscoelastic materials.

Lipid Nanotubes: A Unique Template To Create Diverse One-Dimensional Nanostructures

Lipid molecules can self-assemble in liquid media into open-ended, hollow cylindrical structures, which are composed of rolled-up bilayer membrane walls. The resultant lipid nanotubes (LNTs) have a few unique properties, such as controllable diameters and length and finely functionalizable surfaces benefitting template-synthesized one-dimensional (1-D) nanostructures, that no other individual templates possess. The elegant hollow cylinders of the LNT can modulate the nucleation, growth, and deposition of inorganic substances on their external and internal surfaces, in the hollow cylinder, and in the bilayer membrane wall. Templating the LNTs enables one to produce diverse 1-D nanostructures, such as nanotubes, concentric tubular hybrids, complex helical architectures, and 1-D arrays of quantum dots.

Geoinspired synthetic chrysotile nanotubes

Since the 1991 discovery of hollow cylindrical carbon-based unidimensional structures, the nanotubular form of matter has been thoroughly investigated leading to a wealth of literature. Their particular features are not limited to graphite but are common in many inorganic highly anisotropic two-dimensional layered compounds. The first non-mineral inorganic nanotubes, constituted of lamellar molybdenum and tungsten disulfides, were synthesized in 1992. Afterwards, a large number of inorganic nanotubes have been synthesized, opening the path to the development of nanoelectronics, due to their dielectric properties. The unique mineral phase that crystallizes with a tubular morphology is chrysotile, which has been tentatively used to prepare ultra-thin wires by filling its hollow nanodimensional core with a conductive material. To overcome its natural heterogeneity in composition, morphology, and structure, synthetic chrysotile-inspired nanotubes have been recently synthesized. These geoinspired nanotubes can be prepared with specific properties, finalized to focused achievements such as preparation of new quantum wires. The existing knowledge on the structural and physicochemical properties of mineral and synthetic chrysotile nanotubes is reviewed, with the aim of emphasizing their potential applications as nonlinear optical and conducting technological devices. Bibliography encompasses over one hundred references.

Thermal fluctuations of grafted microtubules provide evidence of a length-dependent persistence length.

Microtubules are hollow cylindrical structures that constitute one of the three major classes of cytoskeletal filaments. On the mesoscopic length scale of a cell, their material properties are characterized by a single stiffness parameter, the persistence length l(p). Its value, in general, depends on the microscopic interactions between the constituent tubulin dimers and the architecture of the microtubule. Here, we use single-particle tracking methods combined with a fluctuation analysis to systematically study the dependence of l(p) on the total filament length L. Microtubules are grafted to a substrate with one end free to fluctuate in three dimensions. A fluorescent bead is attached proximally to the free tip and is used to record the thermal fluctuations of the microtubule's end. The position distribution functions obtained with this assay allow the precise measurement of l(p) for microtubules of different contour length L. Upon varying L between 2.6 and 47.5 mum, we find a systematic increase of l(p) from 110 to 5,035 mum. At the same time we verify that, for a given filament length, the persistence length is constant over the filament within the experimental accuracy. We interpret this length dependence as a consequence of a nonnegligible shear deflection determined by subnanometer relative displacement of adjacent protofilaments. Our results may shine new light on the function of microtubules as sophisticated nanometer-sized molecular machines and give a unified explanation of seemingly uncorrelated spreading of microtubules' stiffness previously reported in literature.

Nondestructive Evaluation of Ceramic Candle Filter with Various Boundary Conditions

Nondestructive evaluation (NDE) using a dynamic characterization technique was conducted to study ceramic candle filters. Ceramic candle filters are hollow cylindrical structures made of porous ceramic materials used to protect gas turbine in coal-fired power plants. Deterioration and failure of ceramic filters occurs after being exposed to high-temperature and high-pressure operational environment over a period of time. This paper focuses on the development of an NDE method that can predict the in-situ structural stiffness of the candle filters while still being attached to the plenum. A combination of laboratory testing, theoretical analysis, and finite element method (FEM) simulations are presented. The candle filters were tested using a laser vibrometer/accelerometer setup with variable boundary restraints. A variable end-restraint Timoshenko beam equation was derived to determine the dynamic response of the candle filters with simulated in-situ boundary conditions. Results from the FEM simulation were verified with the analysis to determine the stiffness degradation of the candle filters as well as the boundary conditions. Results from this study show that the vibration characteristics can be used effectively to evaluate both the structural stiffness and the in-situ boundary restraints of the ceramic candle filters during field inspections.

Synthesis route for obtaining manganese oxide-based nanostructures

Hollow and solid cylindrical nanometric structures of mixed valent manganese oxide-based compounds were obtained by wetting sacrificial porous substrates. Plastic templates with pores ranging 0.05–1 μm were employed; a two-stage thermal process was performed to obtain La 0.325Pr 0.300Ca 0.375MnO 3 or La 2/3Sr 1/3MnO 3. Polycrystalline self-standing tubes were obtained for pore size higher than 0.2 μm, while wires were obtained for diameters below 0.1 μm. We discuss the role of the template pore size in determining the synthesis route, the formation of different intermediate compounds, and different morphologies.

Self-Assembly and Subsequent Accumulation of Lipid Nanotubes at Oil/Water Interfaces

We utilized oil/water interfaces as a new field to produce lipid nanotubes (LNTs), which are formed by the self-assembly of lipid molecules, and possess hollow nanometer-wide cylindrical structures. Compared to the self-assembling field in bulk water, oil/water interfaces produced shorter lipids nanotubes less than 10 microm long more efficiently. In addition, we found that the oil/water interface accumulates lipid nanotubes spontaneously. This methodology is favorable to fabricate LNTs as new nano-fluidic devices, or sensors that require accumulation and alignment in two dimensions.

Axial crush of hollow cylindrical structures with various polygonal cross-sections: Numerical simulation and experiment

The crush behaviors of hollow cylindrical structures with various regular polygonal cross-sections are numerically investigated under axial compression using the FEM program code of the public domain version of DYNA3D. The effects of wall thickness and plastic hardening rate of material on the crush behavior are also investigated. Crush strength increases as the number of corners of the cross-section increases, though it almost saturates for the number of corners beyond 11. Cross-sectional shape with less than six corners should be avoided to take a regulated collapse pattern. The effect of number of polygonal corners on enhancement in crush strength becomes more prominent as the initial wall thickness decreases. Higher plastic hardening rate stabilizes the collapse pattern, where it is a symmetric accordion mode in circular cross-section, otherwise asymmetric diamond one occurs. Further, for hollow cylindrical structures with circular or square cross-section which are aluminum alloy extrusions, quasi-static and impact axial compression tests and the corresponding computations are carried out. As for the circular cross-section, the number of corners induced during collapse increases as the initial wall thickness decreases both in the experiment and the numerical simulation. Crush strength is lower for square cross-section than that for circular one. This tendency agrees with the computational result.

‘New dimensions for manufacturing’ — A UK strategy for nanotechnology

This chapter discusses the nanotechnology and nano engineered membranes. Self-assembly of molecules or large groups of molecules is a key feature in nanotechnology. Nanotechnology deals with structures having at least 1D that is sufficiently small, of the order of about one to several hundred nanometers. It is concerned with materials and systems whose structures and components exhibit novel and improved physical, chemical, and biological properties. It enables the exploitation of novel phenomena and processes because of their nanoscale size. The chapter presents some examples of nano and micro engineered membrane technology and its use for nano engineered devices. A technique to pattern surfaces is to evaporate a target material through a thin membrane (shadow mask) with well-defined perforations. Photonic crystals are artificially three-dimensional structures fabricated in an optical material (crystal or amorphous) with unit cells whose dimensions are comparable to the optical wavelength. Nano and microsieves can be used as stencils for patterning, as photonic crystals, but they can also be used as a proper solid support for thin functional membranes. Nanotubes are the hollow cylindrical structures. The chapter discusses the nano printing and etching with phase separated membranes. Research goal in biomembrane science is to study the function of natural biomembranes and to engineer new types of biomembrane materials on the nanometer scale.

有限な薄氷盤に囲まれた固定式中空円筒構造物の地震流力弾性解析

The hydroelastic response of fixed hollow cylindrical structures surrounded by thin floating ice sheet of finite width during earthquakes is formulated. The 'elastic shell theory is used for structures, whereas the potential flow theory is applied to fluid domain. The sea ice is idealized as the annular rigid boundary that is connected with semi-infinite free surface. The hydrodynamic pressure is obtained in closed form by domain division method. Wet mode properties in beam mode of hollow cylindrical structure are evaluated by Rayleigh-Ritz method. Modal superposition approach is used to calculate the earthquake response against horizontal ground motion. Numerical examples are presented to illustrate the changes in hydrodynamic pressures and earthquake responses due to the width of ice sheet.

A finite-element analysis of magnetically driven recirculating flow in electromagnetic near net shape casting

Electromagnetic processing has been used in the metals industry for the casting of near net shape products from liquids, liquid-solid slurry or semi-solids. Magnetically driven flow often occurs in electromagnetic processing systems and can have significant implications for both process optimization and quality control. This paper presents a finite-element analysis of the complex electromagnetic and fluid flow phenomena in the electromagnetic casting of near net shape products, with particular emphasis being placed on the casting of hollow cylindrical structures. The computational methodology is based on a combination of the volume-integral method and the finite-element method, with the former for the electromagnetic field distributions and the latter for magnetically driven recirculating flow. With the model, the electromagnetic and fluid-flow phenomena are studied as a function of operating conditions such as inductor positions, screen positions, input currents and imposed field frequencies. The results show that the flow in an annular liquid pool is characterized by two anti-rotating loops, as opposed to a single loop in solid ingot casting. It is found: that the maximum velocity is linearly proportional to the applied currents; that the insertion of screens deeply into the inductor loops reduces the flow intensity and reverses the main flow direction; and that the phase angle has no effect on the fluid flow. Calculated results are compared with measurements taken on a pilot electromagnetic caster for the axial magnetif field along the gap between the screen and the side of the molten metal, good agreement between the two being obtained.

Membrane-bound high molecular mass proteinases from human erythrocytes

Two high molecular mass proteinases, multicatalytic proteinase (MCP) and a new high molecular mass proteinase (HMP) with only chymotrypsin-like activity (Khan et al. (1994) J. Biol. Chem. 269, 10016–10021) from human erythrocyte membranes, have been compared. For this purpose, MCP was purified from human erythrocyte membranes in the active form towards synthetic peptide substrates; it also hydrolysed the protein substrates [14C]methyl casein and [14C]oxidised insulin β chain at 37°C. MCP from plasma membranes exhibited hollow cylindrical structures also typical of cytosolic forms. Radiolabelled diisopropyl fluorophosphate, [3H]DFP, a serine proteinase inhibitor, labelled a hand of Mr 23 000 in membrane MCP. By contrast, no labelling was obtained with HMP. Chymotrypsin-like activity of HMP was also found to be insensitive to DFP. On the other hand, DFP inhibited chymotrypsin-like and peptidylglutamyl peptide hydrolysing activities of membrane MCP, with no effect on its trypsin-like activity. The inhibition of MCP by DFP was concentration-dependent. These studies showed that MCP and HMP represent two distinct kinds of proteinases with chymotrypsin-like activities and can be distinguished by the serine proteinase inhibitor DFP.

The transverse elastic impact response of thick hollow cylinders

The two objectives of the studies in this paper were to determine the transient elastic impact response of thick-walled hollow cylindrical structures and to determine how this response was affected by the presence of flaws in the cylinder. These studies were aimed at determining the feasibility of using the impact-echo method for detecting flaws in the cylindrical concrete structures, such as pipes. Three-dimensional finite element models and laboratory specimens containing various types of flaws at known locations were used in the studies. It is shown that, for a hollow cylinder having a length greater than about eight times its outer diameter, the impact response as measured at points close to the impact point is composed of a number of resonant frequencies caused by cross-sectional (flexural) modes and a thickness frequency caused by dilatational waves reflected between the inner and outer wall surfaces. Equations are presented which relate the response of a hollow cylinder to the frequency of the fundamental cross-sectional (flexural) mode of a solid circular bar. It is shown that the location of cracks, areas of reduced wall thickness, and honeycombing as well as the depth of surface-opening cracks can be determined.

Effect of alcohol chain length on tubule formation in 1,2-bis(10,12-tricosadiynoyl)- sn-glycero-3-phosphocholine

Aqueous dispersions of 1,2-bis(10,12-tricosadiynoyl)- sn-glycero-3-phosphocholine, on cooling below the chain melting temperature, form hollow cylindrical structures known as ‘tubules’. We have studied the formation of tubules in methanol/water, ethanol/water and n-propanol/water. For each alcohol, there is a defined window of alcohol/water ratios in which the lipid precipitates with the tubule morphology. As the chain length of alcohol is increased, the window shifts towards lower alcohol fraction. Light scattering studies show that at very low lipid concentrations the tubules self-assemble directly from the isotropic phase where as for lipid concentrations greater than 4 mg/ml an intermediate L α phase is observed. These results indicate that the mechanism of tubule formation may be dependent on lipid concentration.

X-Ray Diffraction Studies of Tubules Formed from a Diacetylenic Phosphocholine Lipid

AbstractThe diacetylenic phosphocholine lipid 1,2-bis(10, 12-tricosadiyonol)-sn-glycerol- 3-phosphocholine forms, upon cooling below the chain melting temperature, hollow cylindrical structures known as ‘tubules’. These tubules are approximately one micron in diameter and may range from tens to hundreds of microns in length. We have carried out x-ray diffraction studies of tubules (1) in 75/25 ethanol/water by volume and (2) in a dessicated state. We present results which show marked differences in the nature of both the in-plane and inter-layer correlations associated with the wrapped multilayer structure of the tubules in the two states.

Lateral phase separation based on chirality in a polymerizable lipid and its influence on formation of tubular microstructures

No difference is believed to exist between the physical properties of racemic and enantiomeric phospholipids. We report here the first observation of lateral phase separation of phospholipids on the basis of the chirality of the glycerol backbone. The chiral polymerizable diacetylenic lecithin 1,2-bis-(10,12-tricosadiynoyl)- sn-glycero-3-phosphocholine, or l-DC 8,9PC, spontaneously forms hollow cylindrical structures, or tubules, and similar right-handed helices. To determine the influence of chirality of the lipid on the morphology of the resultant microstructures, d-DC 8,9 and rac-DC 8,9PC were synthesized. The T vs. X L phase diagram for the lipids in excess water indicates formation of a racemic mixture, with no appreciable co-crystallization of the enantiomers in the bilayer plane. When exposed to tubule-forming conditions, rac-DC 8,9PC produced tubules, right- and left-handed helices, and a small proportion of anomalous microstructures such as flat and loosely-wound sheets, and pairs of tubules linked by sheets. The formation of chiral structures is consistent with the thermodynamic data, suggesting that lateral phase separation on the basis of chirality is responsible for formation of tubules from rac-DC 8,9PC liposomes, and that when monomer is precipitated from alcoholic solution the resultant microstructures are of predominantly one handedness or the other. The unusually poor miscibility of the enantiomers is the low temperature phase can be explained by hydrocarbon chain packing constraints imposed by the diacetylene moiety.

Ultrastructural study of adhesion of enterotoxigenic Escherichia coli to erythrocytes and human intestinal epithelial cells.

The adhesion to erythrocytes and human intestinal epithelial cells of enterotoxigenic Escherichia coli strains H10407, B2C, and H10407P, expressing colonization factor antigen I (CFA/I), CFA/II, and type 1 fimbriae, respectively, was examined by electron microscopy. CFA and type 1 fimbriae were visualized by negative staining in thin sections after en bloc staining with ruthenium red and by immune labeling with antisera raised against purified fimbriae. By negative and ruthenium red staining, CFA/I, CFA/II, and type 1 fimbriae were indistinguishable and appeared as approximately 7-nm-diameter hollow cylindrical structures up to 1.5 micron in length; strain B2C also produced 2- to 3-nm-diameter flexible fibrillar fimbriae. Bacteria producing CFA/I, CFA/II, and type 1 fimbriae adhered to and agglutinated human, bovine, and guinea pig erythrocytes, respectively; CFA/I and CFA/II also mediated attachment of bacteria to the brush border of isolated human duodenal enterocytes. Electron microscopy of agglutinated erythrocytes and enterocytes with adherent bacteria showed, in each case, that bacterial adhesion involved the formation of many interactions between the tips of fimbriae and receptors on the erythrocyte or enterocyte brush border membrane. Immune labeling allowed different fimbrial antigens mediating bacterial attachment to human enterocytes to be identified.

Evidence against interconversion of microtubules and filaments.

MICROTUBULES, hollow cylindrical structures of diameter ∼250 A and variable length, consisting of 13 protofilaments (diameter ±40 A), are now generally accepted as an essential constituent of most eukaryotic cells. They have been implicated in such diverse functions as: maintenance of cell shape, intracellular transport and organisation, movement (particularly slow morphogenetic movement) and control of cell surface topography (for review see ref. 1).

Characterization of rhapidosomes of Saprospira grandis

Physical and chemical properties of rhapidosomes, rod-shaped particles produced by Saprospira grandis and related marine flexibacteria, are described. The particles, which are composed of two hollow cylindrical structures, one partially encasing the other, bear a striking resemblance to tail components (core and contracted sheath) of various bacteriophages (e.g. the T-even phages of Escherichia coli). The core is approximately 4300 Å in length and 90 Å in diameter with an axial channel 25 Å in diameter running through it. The sheath is approximately 2000 Å in length and 280 Å in diameter with a channel 110 Å in diameter. Molecular weights of 17 × 10 6 and 60 × 10 6 were estimated for the core and sheath, respectively. The presence of helical grooves of long pitch on the surface of the rhapidosome sheath was demonstrated by both the negative-staining and shadow-casting techniques. As observed previously (Reichle & Lewin, 1968) twelve curved projections were seen around the periphery of the rhapidosome sheath when viewed in cross section. Our evidence suggests that these projections represent a morphological characteristic of a subunit. In contrast to reports (Correll & Lewin, 1964; and Correll, 1968) that rhapidosomes are composed of protein and highly 2′- O-methylated RNA, our results indicate that the particles do not contain a nucleic acid component. Amino-acid analyses of crystalline core and purified sheaths show that they are distinctly different proteins. Both particles are resistant to a variety of reagents which normally dissociate proteins into subunits. The possibility that rhapidosomes, like many morphologically similar particles, are portions of a defective bacteriophage, the genome of which has become associated with the genetic system of the bacterium, is discussed.

GENERAL AND PRACTICAL CALCULATION FORMULAE OF THE STRESSES IN HOLLOW CYLINDRICAL SHELL DUE TO FORCED VIBRATION

No reasonable and desirable calculation formula has been provided up to this time for the stress caused by earthquake in the hollow cylindrical shell. Therefore, in this paper the author proposed both of general and practical calculation formulae of stresses due to the forced vibration, solving the well-known three simultaneous equations of motion, and introduced the stress calculation graphs by means of which the stresses caused by earthquake in the reinforced concrete hollow cylindrical structures can be calculated. In addition, some discussion was given to the damage of the fodder storage silos which was damaged by the great earthquake of 1952 at the southeastern district of Hokkaido so called Tokachi-Oki Earthquake.