Hollow Filaments Research Articles

Sheath/Core형 나일론/PET 고중공 복합사 및 직물물성 연구

This paper surveys the physical properties of sheath/core nylon/PET high hollow composites filaments and its fabrics according to the various elution conditions such as concentration of elution, eluted time and eluted temperature. For this purpose, sheath/core nylon/PET filament was texturized and four kinds of fabric specimens were woven with different warp and weft densities. These grey fabrics were eluted with two kinds of concentrations of NaOH (30g/l, 40g/l), three kinds of eluted temperatures ) and two kinds of eluted times (60min, l20min). The elution characteristics of these specimens were investigated and discussed with different elution conditions. In addition, the mechanical properties such as extensibility, bending rigidity, shear modulus and compressional work of these specimens aceording to the elution conditions were analysed and summarized with cross-sectional shapes of eluted filaments measured by SEM.

Developmental Variation in the Dermal Glands and Wax Secretions of the Mealybug, Phenacoccus fraxinus (Hemiptera: Coccoidea: Pseudococcidae)

A microscopic study of the dermal glands and wax secretions of the mealybug Phenacoccus fraxinus Tang demonstrated that the type, structure, size, quantity and distribution of dermal glands varied with life stage. These variations resulted in different quantities and morphology of waxy secretions with development. The apertures of the trilocular pores were initially small, irregular narrow seams on 1st instars. By the 3rd nymphal stage, these apertures were large and figure-8 shaped. Slender wax filaments were produced in the 1st stage, whereas wax filaments produced in the 3rd stage had an indentation along the middle. These tilocular pores were distributed on the dorsum and the venter of both stages, corresponding to the shape of the aperture. Quinquilocular pores were characterized by a thick rim and were scattered on the ventral surface, but these were not distributed in spiracle furrows as observed with other scale insects. Tubular ducts were composed of 2 layers—outer and inner ductiles—that resulted in the wax secreted from them being long, hollow filaments that served as a framework for the cocoon and ovisac structures. Wax production from these tubular ducts occurred at two distinct times during development. One occurred in late autumn and was produced by the older 2nd -instar nymphs. These waxy filaments were used to construct cocoons for the overwintering mealybugs. The other event occurred in early summer with adult females. These filaments were used to construct the ovisac. During other times of the year, these tubular ducts produced no additional wax.

Mechanics of microtubules modeled as orthotropic elastic shells with transverse shearing

Microtubules are hollow cylindrical filaments of the eukaryotic cytoskeleton characterized by extremely low shear modulus. In this paper, an orthotropic elastic shell model with transverse shearing is developed to study the effects of transverse shearing on shell-like mechanics of microtubules. The study is based on a detailed comparison between four elastic beam and shell models with and without transverse shearing. It is shown that the length-dependent flexural rigidity of microtubules predicted by the present orthotropic shell model with transverse shearing is in good agreement with known experimental data and is consistently close to that given by the Timoshenko-beam model. Our results show that transverse shearing is essential for shell-like deformation of microtubules when the axial wave-length is not extremely long (compared to the diameter of microtubules which is ~25 nm) or the circumferential wave-number is larger than unity. In particular, transverse shearing is found to significantly lower the critical pressure for buckling of a long microtubule under radial pressure and leads to an even better agreement with recently observed experimental data. These results suggest that the 2D orthotropic shell model with transverse shearing is suitable to study the shell-like mechanics of microtubules for short axial wave-length and circumferential wave-number exceeding unity.

Surface deflection of a microtubule loaded by a concentrated radial force

Microtubules are hollow cylindrical filaments of a eukaryotic cytoskeleton which aresensitive to externally applied radial forces due to their low circumferential elastic modulus.In this work, an orthotropic elastic shell model for microtubules is used to study the surfaceradial deflection of a microtubule loaded by a concentrated radial force generated by eithera single molecular motor or a radial indentation tip. Our results show that themaximum surface radial deflection of a microtubule generated by a concentrated radialforce of a few pN can be as large as a few nanometers (a significant fraction ofthe radius of microtubules), which could cause significant surface morphologicalnon-uniformity of the microtubule. In contrast, radial indentation under a much largercompressive force, which can be as large as a few hundreds of pN, will causehardening of the circumferential elastic modulus almost equal to the longitudinalmodulus of microtubules. In this case, our results show that a microtubule canwithstand a concentrated radial compressive force as large as a few hundreds ofpN, with a maximum radial deflection not more than a few nanometers, in goodagreement with recent experiments on radial indentation of microtubules. Theseresults offer useful data and new insights into the basic understanding of elasticinteraction between microtubules and molecular motors and radial indentation ofmicrotubules.

Preparation and Physical Properties of Hollow Polyester Filaments with High Breathability, Water Absorption and Release Rates

This paper reports the preparation of hollow polyester filaments with high water absorption and release rates, and the study of their physical properties using differential scanning calorimetry, thermogravimetric analysis, density gradient, gel permeation chromatography, rheometry and statistical regression analysis. Four readily soluble poly(ethylene glycol)-modified cationic dyeable poly(ethylene terephthalate) (PEG-CDPET) polymers were prepared, with 3 mol % of the sodium salt of dimethyl 5-sulfo-isophthalate (SIPM). The poly(ethylene glycol) (PEG) contents were 3 and 6 wt% and the number-average molecular weights ([Formula: see text]) of the PEG were 600 and 8000 (g/mol). Blends of regular PET and PEG-CDPET were spun into hollow filaments. These hollow filaments were then drawn and treated with aqueous sodium hydroxide. The crystallinity of the PEG-CDPET polymers declined as the PEG content increased, given a fixed SIPM content. Furthermore, the crystallinity of the PEG-CDPET polymers declined as the [Formula: see text] of the PEG increased for the same SIPM and PEG contents. The SIPM and PEG segments did not change the original PET unit cell. The sodium sulphonate (–SO3Na) functional groups and the PEG molecules were only on the crystal surface and in the amorphous regions. Obviously, the rate constants for alkaline hydrolysis were in the order: PEG-CDPET polymer<<CDPET polymer<regular PET polymer. The water-absorption and release and the heat retention properties of alkali treated PET/PEG-CDPET polyblend hollow filaments were better than those of the regular PET filaments. The porous nature of the large filaments (from 0.02-1 μm in diameter) was observed after alkali treatment of the PET/PEG-CDPET polyblend hollow filaments. Additionally, the hollowness of the PET/PEG-CDPET polyblend filaments was observed to increase from 40 to 42% after alkali treatment.

Physical Properties of R-PET/CD-PET Polyblended Hollow Filaments and Their Kinetics of Alkaline Hydrolysis

Cationic dyeable poly(ethylene terephthalate) (CD-PET) was formed by copolymerizing dimethylterephthalate (DMT),5-sodium sulfonate dimethyl isophthalate (SIPM) with a molar ratio of 2% and ethylene glycol (EG). Blends of regular poly(ethylene terephthalate) (R-PET) and CD-PET were spun into hollow filaments. The filaments were then treated with aqueous NaOH. This study investigated the physical properties of R-PET/CD-PET polyblended hollow filaments and their kinetic behavior of alkaline hydrolysis using differential scanning calorimetry (DSC), wide angle x-ray diffraction (WAXD), the density gradient method, gel permeation chromatography (GPC), rheometer measurement and statistical analysis using the regression method. Experimental results indicate that the rate constant of alkaline hydrolysis was CD-PET hollow filaments >R-PET/CD-PET polyblended hollow filaments > R-PET hollow filaments. For the alkaline hydrolysis kinetics equation of R-PET, CD-PET/R-PET polyblended and CD-PET hollow filaments: −dW/dt=KCαAβ, β is equal to 1. Moreover, R2 of the kinetics equation for α from 1.06∼1.29 was better than that of α=1.

Organic Crystal Templating of Hollow Silica Fibers

The incipient crystallization of needlelike forms of organic salts, such as ammonium dl-tartrate or ammonium oxalate, has been used for the templating of sol−gel reactions to produce hollow silica fibers and filaments with geometrically shaped channels. By judicious control of both the crystallization and hydrolysis−condensation processes, flexible tubes with continuous wall structures, often only 30 nm in thickness, can be produced.

Assembly of thick filaments and myofibrils occurs in the absence of the myosin head

We investigated the importance of the myosin head in thick filament formation and myofibrillogenesis by generating transgenic Drosophila lines expressing either an embryonic or an adult isoform of the myosin rod in their indirect flight muscles. The headless myosin molecules retain the regulatory light-chain binding site, the alpha-helical rod and the C-terminal tailpiece. Both isoforms of headless myosin co-assemble with endogenous full-length myosin in wild-type muscle cells. However, rod polypeptides interfere with muscle function and cause a flightless phenotype. Electron microscopy demonstrates that this results from an antimorphic effect upon myofibril assembly. Thick filaments assemble when the myosin rod is expressed in mutant indirect flight muscles where no full-length myosin heavy chain is produced. These filaments show the characteristic hollow cross-section observed in wild type. The headless thick filaments can assemble with thin filaments into hexagonally packed arrays resembling normal myofibrils. However, thick filament length as well as sarcomere length and myofibril shape are abnormal. Therefore, thick filament assembly and many aspects of myofibrillogenesis are independent of the myosin head and these processes are regulated by the myosin rod and tailpiece. However, interaction of the myosin head with other myofibrillar components is necessary for defining filament length and myofibril dimensions.

Morphology of Poly(4-methyl-1-pentene) Melt-spun Hollow Filament.

The morphology in the bulk and at the surfaces of melt-spun poly-(4-methyl-1-pentene) hollow filaments was investigated by using several etching methods and electron microscopy to clarify the formation mechanism of an asymmetric membrane formed with a melt-spinning method. Stacked lamellar crystals were formed in the bulk and at the inner wall of the hollow filaments, and dual skin layers were observed at the outer wall. The outermost layer was composed of lamellar crystals, which were highly oriented in a plane parallel to the surface. The other layer was composed of non-oriented lamellar crystals. The lamellar crystals in the latter layer incline to orient in the plane perpendicular to the machine direction at higher draft ratios. The thickness of the layers decreases with the increase of draft ratio. These layers were also found at the inner wall when an oxygen-containing gas was introduced instead of nitrogen into the boar of the hollow filament. It was suggested, therefore, that the degradation of polymer at the surface of the hollow filament causes the skin layers to be produced as mentioned above.

Hydrogen production via the direct cracking of methane over silica-supported nickel catalysts

We have investigated the catalytic cracking of methane as an alternative route for the production of hydrogen from natural gas. Nickel supported on silica was found to be active for this reaction producing stoichiometric amounts of hydrogen and carbon. SEM and TEM characterization of the spent catalyst indicated that carbon deposits on the catalyst in the form of hollow cylindrical filaments, with a nickel particle located on the tip of each filament. As a result, deactivation due to carbon deposition does not occur until the carbon filaments begin to interfere with each other and the silica surface, due to the spatial limitations of the pore structure of the catalyst. The deactivated catalyst can be fully regenerated by either oxidation in air or steam gasification of the deposited carbon. Additional hydrogen is produced during the steam regeneration process.

Three-Dimensional Structure of HIV-1 Rev Protein Filaments

The HIV-1 Rev protein facilitates the export of incompletely spliced and unspliced viral mRNAs from the nucleus. Rev polymerizes into two types of filamentsin vitro. In the presence of RNA, Rev forms poorly ordered structures, while in the absence of RNA it polymerizes into regular hollow filaments. We have determined the helical structure of the latter filaments by analysis of cryo-electron micrographs, taking into account STEM measurements of mass-per-unit-length. They are made up of Rev dimers, arranged in a six-start helix, with 31 dimers in 2 turns, a pitch angle of 45°, and an interstrand spacing of 3.8 nm. Three-dimensional reconstruction at 2.1 nm resolution reveals a smooth outer surface and a featured inner surface, with outer and inner diameters of ≈14.8 and ≈10.4 nm, respectively. The Rev dimer has a “top-hat” shape with a cylinder ≈3.2 nm in diameter and ≈2.2 nm high, pointing inward: the thinner rim areas pack together to form the filament wall. Raman spectroscopy shows polymerized Rev to have ≈54% α-helix and 20–24% β-sheet content. Electron microdiffraction of aligned filaments reveals a broad meridional reflection at ≈(0.51 nm)−1, suggesting approximate alignment of the α-helices with the filament axis. Based on these data, a molecular model for the Rev filament is proposed.

The molecular structure of agrobacterium VirE2-single stranded DNA complexes involved in nuclear import

Nuclear import of DNA is a central event in genetic transformation of plant cells by Agrobacterium tumefaciens. Agrobacterium elicits tumors on plant hosts by transporting a single-stranded (ss) copy of the bacterial transferred DNA (T-DNA) from its Ti (tumor-inducing) plasmid into the plant cell nucleus. Presumably, the process of T-DNA nuclear import is mediated by two agrobacterium proteins, VirD2 and VirE2, which are thought to directly associate with the transported T-DNA. Both proteins have been shown to contain functional nuclear localizations signals (NLS). Recently, VirE2 alone has been shown to actively transport ssDNA into the plant cell nucleus. To understand the process of DNA nuclear import, it is important to know the structure of the transport intermediate. To this end, complexes of VirE2 and ssDNA were analyzed by scanning transmission electron microscopy (STEM). This analysis suggests that VirE2 packages ssDNA into semi-rigid, hollow cylindrical filaments with a telephone cord-like coiled structure. The outer diameter of these complexes is too large to enter the nucleus by diffusion but is within the size exclusion limits of the active nuclear import. Detailed mass analysis of VirE2-ssDNA filaments is presented and a structural model is proposed.

On the energetics of tubular fullerenes

The binding energy of a long monolayer carbon tubule is compared to that of the planar graphene strip resulting from unrolling the tubule. It turns out that the tubule is energetically less stable than the strip when its radius is smaller than a critical value. The limiting radius is reached when the elastic energy stored in bending the strip exceeds the energy recovered from stitching its dangling bonds along the tubule generator. This criterion gives a critical radius of order 3 Å. A growth model proposed by Tibbetts for multilayer, hollow graphitic filaments is also discussed. The model indicates that filaments smaller than about 15 Å outer radius should preferably grow as single-layer tubules, while filaments larger than about 20 Å could accommodate an increasing number of cylindrical layers.

Electron microscopy of a double helical tubular filament in keyhole limpet (Megathura crenulata) hemolymph.

A approximately 25 nm hollow double helical filament has been detected ultrastructurally in the cell-free supernatant from hemolymph of the keyhole limpet Megathura crenulata (Gastropoda: Prosobranchia: Fissurellidae). Subsequently, much higher concentrations of this material were found in the cell pellet from hemolymph. Both negative staining and thin sectioning have been performed in an attempt to obtain a preliminary structural characterization of this new filament. It is proposed that the filaments are released or secreted from blood hemocytes in response to bleeding, but it has not been possible to define absolutely an intracellular organelle containing this material. It is shown that the hollow filaments, which have fine fibrillar surface extensions, are readily distinguishable from collagen fibrils and from tubular (multi-decameric) keyhole limpet hemocyanin (KLH).

Hysteresis losses in hollow superconducting filaments and in multifilament systems

The magnetization of hollow superconducting filaments in a perpendicular applied field is calculated numerically using a mathematical model. With this model the hysteresis losses over a closed cycle of the applied field, as well as the instantaneous power dissipation in the filament, can be calculated. Theoretical results are compared with data from experiments using wire with hollow Nb 3Sn filaments. Demagnetization effects caused by the influence of the field of one filament on another are studied and, finally, bridging between neighouring filaments and its influence on the effective filament diameter and the hysteresis losses are discussed.

AC-losses in the ECN concept of the NET-TF-conductor

Analysis of the conditions on the toroidal-field coils of the Next European Torus machine indicates that the largest AC-loss contributions are to be expected from coupling losses in the flat superconducting cable, and to a lesser extent from hysteresis losses in the niobium-tin filaments. Coupling losses are caused by currents in a transverse direction induced by the pulsed field perpendicular to the broad side of the cable. These losses are inversely proportional to the transverse resistivity of the cable. The influence on the transverse resistivity of wires having a copper-nickel shell around the wire-filament zone was verified experimentally. Theoretical calculations of the transverse resistivity of the flat cable are discussed. Hysteresis losses in a perpendicular AC field were measured experimentally in two types of multifilamentary niobium-tin wire, both having hollow filaments. A simple model for calculating hysteresis losses in hollow filaments is also reported. >

Characteristics of discharges inside simulated tree channels under impulse voltage

The authors attempt to characterise the electrical discharges initiated in hollow filaments of small diameter in low-density polyethylene. This study is related to electrical treeing, a pre-breakdown phenomenon in certain polymers submitted to high electrical stresses. A positive single pulse voltage was applied to a channel prepared in a polyethylene specimen. The channel diameter ranges from 1 mm to 13 mu m and the gap from 1 to 5 mm. The characteristics of the discharges growing in the channels were recorded and compared with free air discharges under the same conditions. It is shown that the channel walls disturb the discharge below a critical value of the ratio between the channel diameter ( Phi ) and the gap (d). A quicker heating of the gas is assumed to explain the behaviour of these confined volumes.

Ultrastructure of skin in primary systemic amyloidosis

Amyloid masses were found in the dermis of two brothers suffering from primary amyloidosis. The masses consisted of fibrils, composed in turn of twin hollow filaments of amyloid. An amyloid filament appeared as a 3 nm thick lucent core with a 2 nm thick wall. Occasionally 4--6 filaments were packed together in one fibril. The twin filaments were slightly twisted, with a twisting angle of 2.5 degrees and a coiling pitch of 1 160 nm. Wavy shapes of amyloid fibrils were also seen in elastic fibres. Amyloid fibrils were found in elastic fibres, under the basal lamina of the epidermis, sweat gland epithelium and Schwann cells; also around perineural cells, perivascular cells and, in one of the brothers, in collagen fibril bundles. No amyloid fibrils were found under the endothelial basal lamina. It would appear that amyloid fibrils are pathological fibrils belonging to the elastic fibre-basal lamina system.

Antennal chemoreceptors of the desert burrowing cockroach, Arenivaga sp.

The antennae of Arenivaga have six types of chemoreceptor sensilla. Some of these have unusual morphological features which may be adaptations for survival in a dry habitat. The sensory dendrites are well protected by cuticular structures, and in some receptors stimulatory molecules must pass through long channels or through pores filled with strands to reach the sensory cells. Large grooved pegs (possibly pheromone receptors) are numerous on antennae of adult males, and grooved sensilla are described here in detail for the first time. Thin-walled pegs, present in males and females, do not have pore tubules or hollow filaments as observed in many other insects. Rather, they contain structures designated here as pore strands, since they have a dense core rather than a light center as previously described for pore tubules and filaments. These strands do not appear to be evaginations of the dendritec membrane, but are probably formed in association with the cuticular structures of the sensilla.

The fine structure of Giardia muris.

Giardia is a noninvasive intestinal zooflagellate. This electron microscope study demonstrates the fine structure of the trophozoite of Giardia muris in the lumen of the duodenum of the mouse as it appears after combined glutaraldehyde and acrolein fixation and osmium tetroxide postfixation. Giardia muris is of teardrop shape, rounded anteriorly, with a convex dorsal surface and a concave ventral one. The anterior two-thirds of the ventral surface is modified to form an adhesive disc. The adhesive disc is divided into 2 lobes whose medial surfaces form the median groove. The marginal grooves are the spaces between the lateral crests of the adhesive disc and a protruding portion of the peripheral cytoplasm. The organism has 2 nuclei, 1 dorsal to each lobe of the adhesive disc. Between the anterior poles of the nuclei, basal bodies give rise to 8 paired flagella. The median body, unique to Giardia, is situated between the posterior poles of the nuclei. The cytoplasm contains 300-A granules that resemble particulate glycogen, 150- to 200-A granules that resemble ribosomes, and fusiform clefts. The dorsal portion of the cell periphery is occupied by a linear array of flattened vacuoles, some of which contain clusters of dense particles. The ventrolateral cytoplasm is composed of regularly packed coarse and fine filaments which extend as a striated flange around the adhesive disc. The adhesive disc is composed of a layer of microtubules which are joined to the cytoplasm by regularly spaced fibrous ribbons. The plasma membrane covers the ventral and lateral surfaces of the disc. The median body consists of an oval aggregate of curved microtubules. Microtubules extend ventrally from the median body to lie alongside the caudal flagella. The intracytoplasmic portions of the caudal, lateral, and anterior flagella course considerable distances, accompanied by hollow filaments adjacent to their outer doublets. The intracytoplasmic portions of the anterior flagella are accompanied also by finely granular rodlike bodies. No structures identifiable as mitochondria, smooth endoplasmic reticulum, the Golgi complex, lysosomes, or axostyles are recognized.