Filament Arrangement Research Articles

The three-dimensional arrangement of intermediate filaments in Romney wool cortical cells

The three-dimensional orientation and arrangement of intermediate filaments in Romney wool ortho-, meso-, and paracortical cells has been revealed using single axis high voltage electron tomography. Modelled tomograms confirm that intermediate filaments in orthocortical cells are arranged helically, with the helical angle progressively increasing from the centre to the periphery of macrofibrils. Intermediate filaments in meso- and paracortical cells display parallel arrangements differing mainly in packing density, with the mesocortex packed more tightly than the paracortex. The intermediate filament arrangements observed confirm expectations based on earlier two-dimensional transmission electron microscopy observations by the authors and other researchers. It is expected that these findings will contribute to a better understanding of the biological and structural basis of wool fibre curvature.

MICROFILAMENTS ARE INVOLVED IN RENAL CELL RESPONSES TO SUSTAINED HYDROSTATIC PRESSURE

Increased pressures within renal interstitial fluid, as associated with a number of renal pathologies, could affect cell function and gene expression. The long-term objective of this research is to elucidate kidney cell responses to pathological hydrostatic pressures. In vitro studies were performed in 2 kidney cell lines (cortical tubular and medullary) to determine changes in cell numbers and cytoskeletal (specifically microfilament, microtubule and intermediate filament) arrangement following exposure to pathological (60 cm H2O) pressures. A novel pressure system was used to apply pressure to renal cells for up to 7 days. Cell counts and fluorescent staining were performed to determine alterations in response to pressure. Exposure to pressures of 60 cm H2O resulted in increased renal cell numbers and rearrangement in individual microfilament structures after 7 days. These results prove that hydrostatic pressure alters the function of renal cells. In the future such knowledge of renal cell responses to pressure along with an understanding of the mechanisms involved will aid in the design of novel, targeted drug therapies for treating kidney pathologies.

Diamond coated dental bur machining of natural and synthetic dental materials

Diamond coatings are attractive for cutting processes due to their high hardness, low friction coefficient, excellent wear resistance and chemical inertness. The application of diamond coatings on cemented tungsten carbide (WC-Co) burs has been the subject of much attention in recent years in order to improve cutting performance and tool life. WC-Co burs containing 6% Co and 94% WC with an average grain size 1-3 micron were used in this study. In order to improve the adhesion between diamond and the bur it is necessary to etch away the surface Co to prepare it for subsequent diamond growth. Hot filament chemical vapour deposition (H.F.C.V.D.) with a modified vertical filament arrangement has been employed for the deposition of diamond films. Diamond film quality and purity has been characterised using scanning electron microscopy (S.E.M.) and micro-Raman spectroscopy. The performance of diamond coated WC-Co burs, uncoated WC-Co burs, and diamond embedded (sintered) burs have been compared by drilling a series of holes into various materials such as human teeth, and model tooth materials such as borosilicate glass and acrylic. Flank wear has been used to assess the wear rates of the burs when machining natural and synthetic dental materials such as those described above.

Diamond-Coated Cutting Tools for Biomedical Applications

Diamond coatings are attractive for cutting processes due to their high-hardness, low-friction coefficient; excellent wear resistance, and chemical inertness. The application of diamond coatings on cemented, tungsten carbide (WC-Co) burs has been the subject of much attention in recent years as a method to improve cutting performance and tool life. WC-Co burs containing 6% Co and 94% WC substrate, with an average grain size of 1–3 µm, were used in this study. To improve the adhesion between diamond and WC substrates, it is necessary to etch away the surface Co and prepare the surface for subsequent diamond growth. Hot filament chemical vapor deposition (HFCVD), with a modified vertical filament arrangement, has been used for the deposition of diamond films. Diamond film quality and purity has been characterized using scanning electron microscopy (SEM) and micro-Raman spectroscopy. The performance of diamond-coated WC-Co burs, uncoated WC-Co burs, and diamond-embedded (sintered) burs have been compared by drilling a series of holes into various materials such as human teeth, borosilicate glass, and acrylic teeth. Flank wear has been used to assess the wear rates of the burs when machining biomedical materials such as those just described.

Significant reduction in AC transport self-field losses of Ag-sheathed Bi2223 tapes achievedby changing filament arrangements

Significant reduction in AC transport self-field losses has beenachieved at 77 K for Ag-sheathed Bi2223 multifilamentary tapes withm × n (m,n = 3 or 5) filament arrangements, fabricated via a rectangular deformation process usingtwo-axis rollers. This achievement is not effected by introducing resistive barriers but bychanging filament arrangements. Despite the main contribution being the hysteresis loss ofthe superconductor, the loss values are decreased by approximately 50–70%, compared withthe values for multifilamentary tapes obtained by a standard powder-in-tube process.More complicated filament arrangements achieved via a rectangular deformationprocess lead to further reduction in the loss values. On the basis of numericalcalculations, the loss reduction is mainly ascribed to a division of the field-freecore in the filament groups near the tape edge under AC current transmission.The study should pave the way to removing an obstacle to loss reduction andto developing tape strands with low loss values satisfying practical demands.

Enhancing nucleation density and adhesion of polycrystalline diamond films deposited by HFCVD using surface treaments on Co cemented tungsten carbide

The deposition of diamond films by chemical vapour deposition onto tungsten carbide is an attractive proposition since it can lead to improvements in the life and performance of cutting tools. However, deposition of diamond onto cemented tungsten carbide (WC-Co) dental burs and inserts are problematic due to the cobalt binder in the WC that provides additional toughness to the tool but it causes poor adhesion and low nucleation density. A number of surface treatments can be used to overcome these problems including chemical etching, ion implanting, interlayer coating and bias treatment. Negative biasing of the substrate is attractive because it can be controlled precisely; it is carried out in-situ, gives good homogeneity and results in improved adhesion. On flat substrates, such as copper and silicon, biasing has been shown to give better adhesion, improved crystallinity and smooth surface. In this study, we have used a modified hot filament chemical vapour deposition (HFCVD) system to coat complex shaped tools such as dental burs with polycrystalline diamond films, which have good adhesion and crystallinity. By applying a negative bias to the substrate, we show that the nucleation density, adhesion and surface properties can be improved. The effects of various process parameters such as bias time, emission current, bias voltage and the filament arrangement on the film properties are reported. For machining applications CVD diamond coatings must be hard, wear resistance and having a good quality film.

The influence of filament arrangement on current distribution and AC loss in Bi-2223/Agtapes

State-of-the-art deforming techniques allow the preparation of composite Bi-2223/Ag tapeswith well controlled filament arrangement. This would allow tailoring of the tape’selectromagnetic properties according to specific applications. We studied the possibility toreduce, through a suitable filament ordering, the hysteresis losses caused by anexternal magnetic field perpendicular to the tape’s wide face. For this purpose, thedistribution of shielding electrical currents in multifilamentary superconductingarrays, as a response to a perpendicular AC magnetic field, was investigated boththeoretically and experimentally. We show that due to optimizing of filamentarrangement, the hysteresis loss can be suppressed by one order of magnitude.

Optimization of the filament arrangement at constant radiant heat in HW-CVD for the preparation of compact μc-Si:H at high deposition rates

To obtain high deposition rates for microcrystalline silicon (μc-Si:H) with the Hot-Wire-CVD process under the constraint of a low substrate temperature of 250 °C, various combinations of hot wire arrangements and filament temperatures have been investigated. Raman and infrared spectroscopy and measurements of the dark and photo conductivity are used to evaluate the quality of the material. It is found that lowering the filament–substrate distance at low filament temperature results in a better material quality than higher filament temperatures at larger filament distances. High quality μc-Si:H was deposited at approximately 4 Å s −1 with filament temperatures of 1700–1750 °C and filament–substrate distances of 50–54 mm.

Novel spacer design improves observed flux

In spiral wound membrane (SWM) modules, spacers are essential for keeping the membrane leaves apart. Feed side spacers also enhance flux by promoting eddies, but the disadvantage of spacers is that they increase the pressure loss along the flow channel. The effect of the filament diameter, mesh length and arrangement of spacer filaments was investigated experimentally for ultrafiltration (UF) of dextran and whey solutions. For conventional 2-layer feed spacers, a reduction of the mesh length first increases flux and then flux decreases beyond some optimum mesh length while pressure loss increases continuously with a decrease of the mesh length. An advanced 3-layer spacer (A3LS) is developed with superior mass transfer characteristics and less fouling propensity when compared with conventional 2-layer spacers. The 3-layer spacer improves flux without covering additional membrane area by filaments adjacent to the membrane wall under both fouling and non-fouling conditions. However, the current A3LS design also increases the pressure loss. Under fouling conditions the A3LS has more than 20% higher flux when compared with the 2-layer spacer.

Role of Rho kinase and actin filament in the increased vascular permeability of skin venules in rats after scalding

Objective: To investigate the role of the Small GTPase Rho and endothelial cytoskeleton in the increased vascular permeability of rat skin after scalding. Methods: Rats were subjected to scalding local ventral skin and a venule was isolated from scalded skin and cannulated by micropipette. The venular permeability was measured with a fluorescence ratio technique and expressed with the permeability coefficient to albumin ( P a). The venular F-actin filaments were observed by staining with rhodamine phalloidin and laser confocal scanning microscopy. A specific Rho kinase inhibitor Y-27632 was added into vessel bathing solution or preincubated with vessels to evaluate the role of Rho kinase in regulating of vascular barrier function. Results: Scalding increased P a value of skin venule about threefold compared to normal skin venules ( P<0.01) and was maintained for 120 min. Inhibition of Rho kinase with Y-27632 (30 μmol/l in low-concentration group; 60 μmol/l in high-concentration group) significantly attenuated the hyperpermeability responses to scalding in a dose dependent fashion. A prominent peripheral actin rim (PAR) existed at the outer area of endothelial cells and apparently delineated the cell-to-cell borders. In the control group, the PARs were arranged smoothly and fairly continuously. However, occasionally PARs did show focal interruption with focal fluorescein isothiocyanate (FITC)-albumin leakage. In the burned group, PARs were less organized and accompanied by a large amount of FITC-albumin leakage. Inhibition of Rho kinase with Y-27632 dramatically reduced P a value with recovery of actin filament arrangement in venule after scalding. Conclusion: Burn leads to dermal venular permeability increase with endothelial cytoskeleton depolymerization and disruption. Rho signal transduction pathway is involved in these responses.

Performance and characterisation of CVD diamond coated, sintered diamond and WC–Co cutting tools for dental and micromachining applications

Diamond coatings are attractive for cutting processes due to their high hardness, low friction coefficient, excellent wear resistance and chemical inertness. The application of diamond coatings on cemented tungsten carbide (WC–Co) tools was the subject of much attention in recent years in order to improve cutting performance and tool life. WC–Co tools containing 6% Co and 94% WC substrate with an average grain size 1–3 μm were used in this study. In order to improve the adhesion between diamond and WC substrates, it is necessary to etch away the surface Co and prepare the surface for subsequent diamond growth. Hot filament chemical vapour deposition with a modified vertical filament arrangement has been employed for the deposition of diamond films. Diamond film quality and purity have been characterised using scanning electron microscopy and micro-Raman spectroscopy. The performance of diamond coated WC–Co bur, uncoated WC–Co bur, and diamond embedded (sintered) bur have been compared by drilling a series of holes into various materials such as human teeth, borosilicate glass and porcelain teeth. Flank wear has been used to assess the wear rates of the tools. The materials subjected to cutting processes have been examined to assess the quality of the finish. Diamond coated WC–Co microdrills and uncoated microdrills were also tested on aluminium alloys. Results show that there was a 300% improvement when the drills were coated with diamond compared to the uncoated tools.

Performance and characterisation of CVD diamond coated, sintered diamond and WC–Co cutting tools for dental and micromachining applications

Diamond coatings are attractive for cutting processes due to their high hardness, low friction coefficient, excellent wear resistance and chemical inertness. The application of diamond coatings on cemented tungsten carbide (WC–Co) tools was the subject of much attention in recent years in order to improve cutting performance and tool life. WC–Co tools containing 6% Co and 94% WC substrate with an average grain size 1–3 μm were used in this study. In order to improve the adhesion between diamond and WC substrates, it is necessary to etch away the surface Co and prepare the surface for subsequent diamond growth. Hot filament chemical vapour deposition with a modified vertical filament arrangement has been employed for the deposition of diamond films. Diamond film quality and purity have been characterised using scanning electron microscopy and micro-Raman spectroscopy. The performance of diamond coated WC–Co bur, uncoated WC–Co bur, and diamond embedded (sintered) bur have been compared by drilling a series of holes into various materials such as human teeth, borosilicate glass and porcelain teeth. Flank wear has been used to assess the wear rates of the tools. The materials subjected to cutting processes have been examined to assess the quality of the finish. Diamond coated WC–Co microdrills and uncoated microdrills were also tested on aluminium alloys. Results show that there was a 300% improvement when the drills were coated with diamond compared to the uncoated tools.

Chemical vapour deposition diamond coating on tungsten carbide dental cuttingtools

Diamond coatings on Co cemented tungsten carbide (WC-Co) hard metal tools are widelyused for cutting non-ferrous metals. It is difficult to deposit diamond onto cutting tools,which generally have a complex geometry, using a single step growth process. Thispaper focuses on the deposition of polycrystalline diamond films onto dental tools,which possess 3D complex or cylindrical shape, employing a novel single stepchemical vapour deposition (CVD) growth process. The diamond deposition iscarried out in a hot filament chemical vapour deposition (HFCVD) reactor with amodified filament arrangement. The filament is mounted vertically with the drill heldconcentrically in between the filament coils, as opposed to the commonly usedhorizontal arrangement. This is a simple and inexpensive filament arrangement. Inaddition, the problems associated with adhesion of diamond films on WC-Cosubstrates are amplified in dental tools due to the very sharp edges and unpredictablecutting forces. The presence of Co, used as a binder in hard metals, generallycauses poor adhesion. The amount of metallic Co on the surface can be reducedusing a two step pre-treatment employing Murakami etching followed by an acidtreatment. Diamond films are examined in terms of their growth rate, morphology,adhesion and cutting efficiency. We found that in the diamond coated dental tool thewear rate was reduced by a factor of three as compared to the uncoated tool.

Observation of self-organized filaments in a dielectric barrier discharge of Ar gas

Symmetric self-organized discharge filaments have been observed in the rf (500 kHz) dielectric barrier discharge of Ar gas between two parallel quartz plates with a MgO film. The arrangement of the filaments is confined around the center on the quartz plate plane. With increasing voltage, the number of filaments increases, and the area of filament arrangement also increases. The arrangement of the filaments does not move if the quartz plate with a MgO film is employed, while the whole arrangement rotates without a MgO film. According to the results of current–voltage measurements, Lorentz attractive force is much smaller than Coulomb repulsive force. This suggests that a confinement potential exists as in the case of two-dimensional Coulomb systems in a parabolic potential. However, some of the filament arrangements do not match to those for charged particles in the Coulomb systems, which suggests that the confinement potential does not have pure parabolic profile.

AC losses of multifilamentary Bi-2223/Ag conductors with different geometry and filament arrangement

This paper presents results from numerical modeling of nontwisted multifilamentary Bi-2223/Ag conductors with various geometry and filament arrangement. Anisotropic models of J/sub c/(B) and n(B) have been employed in finite element method simulations under different operating conditions - with applied ac transport current, in external parallel and perpendicular ac magnetic field, and with combined current and field of varying orientation. AC losses and current distributions in square and round Bi-2223/Ag wires with different filament arrangement have been calculated and compared to those of a 7-filamentary tape. It is demonstrated that the shape factor of the conductors and the orientation of the local magnetic field with respect to the individual filaments are of primary importance for the ac loss magnitude in different applications. Outlined are the advantages of using conductors with specific filament configuration for a given application.

Reduction in AC transport self-field losses for Ag-sheathed Bi2223 tapes by changing filament arrangements using two-axial rollers

Without introduction of resistive barriers, we succeeded in reducing AC transport self-field losses at 77 K for Ag-sheathed Bi2223 multifilamentary tapes with the m/spl times/n (m,n=3, 5) filament arrangements, fabricated by a rectangular deformation process using passive two-axial rollers. In spite of the main contribution of hysteresis loss of superconductor, the transport losses for the samples are reduced by approximately 50-70% compared with the values for Ag-sheathed Bi2223 tapes by a standard powder-in-tube process. Further change in filament arrangements using two-axial rollers leads to a further reduction in the loss values. From numerical calculations, the loss reduction is mainly ascribed to a division of field-free-core under AC current transmission.

AC transport losses for Ag-sheathed (Bi,Pb)-2223 tapes prepared by rectangular deformation process

We studied the alternating-current (AC) transport self-field losses at 77 K for Ag-sheathed (Bi,Pb)-2223 tapes prepared by a rectangular deformation process. The rectangular multifilamentary wires with different filament arrangements were fabricated by a two-axial roller (TAR) machine, and subsequently they were converted to the multifilamentary tapes by the standard one-axial flat rolling and heat treatments. Although the losses of investigated tapes are mainly dominated by the hysteresis loss of the superconductor in the frequency range between 40 and 200 Hz, the loss behaviors strongly depend on their cross sectional geometry. The effect of filament arrangements on both the magnetic flux penetration and the loss generations in the multifilamentary tapes under AC current transmission is discussed through numerical analysis.

A progress in reducing AC transport losses of Ag-sheathed Bi2223 tapes by a rectangular deformation using two-axial rollers

Significant reduction in AC transport losses at 77 K and self-field has been achieved for Ag-sheathed Bi2223 multifilamentary tapes with the m× n ( m, n=3 or 5) filament arrangements, which were fabricated by a rectangular deformation process using passive two-axial rollers without any resistive barriers. Despite the main contribution of the hysteresis loss of superconductor, the transport losses for the samples are reduced by approximately 50–70% compared with those for Ag-sheathed Bi2223 tapes by a standard powder-in-tube process. More complicated filament arrangements by a rectangular deformation process lead to a further reduction in the loss values. Numerical calculations show that the loss reduction mainly results from a division of field-free-core under AC current transmission.

Numerical modelling and AC losses of multifilamentary Bi-2223/Ag conductors with various geometry and filament arrangement

This paper presents results from numerical modelling of non-twisted multifilamentary Bi-2223/Ag conductors with various geometry and filament arrangement. New anisotropic models of J c( B) and n( B) have been employed in finite element method simulations under different operating conditions––with applied AC transport current, in external parallel and perpendicular AC magnetic field, and with combined current and field of varying orientation. AC losses, as well as current and magnetic flux densities in square and round Bi-2223/Ag wires with different filament arrangement have been calculated and compared to those of a 7-filamentary tape. The notion of effective I c( B) in transport current applications is introduced and discussed. It is demonstrated that the shape factor of the conductors and the orientation of the local magnetic field with respect to the individual filaments are of primary importance for the AC loss magnitude in different applications. Outlined are the advantages of using conductors with specific filament configuration for a given application.

Influence of cross-sectional geometry and lateral Jc distribution on AC transport losses of Ag-sheathed Bi-2223 tapes

We investigated the influence of cross-sectional geometry and lateral critical current density ( J c) distributions on the AC transport self-field losses at 77 K for the Ag-sheathed (Bi,Pb)-2223 multifilamentary tapes. The modified powder-in-tube method composed of a rectangular deformation and an ordinary rolling process was applied to prepare tapes with different filament arrangements. The trapped magnetic field profiles on the tape wide face in a remanent state indicate that J c distributions along a width direction of the cross-section are strongly influenced by the filament arrangement in each tape. The measured AC transport losses show significant dependence on the filament arrangement, although the main contribution to the losses comes from the hysteresis loss in superconductor filaments. This is caused by the shape of field-free-core and flux-penetration regions, varying with filament arrangement and non-uniformity of J c values along the width direction.