Smooth Side Research Articles

Coculture of endothelial and smooth muscle cells on a collagen membrane in the development of a small-diameter vascular graft

In this study, we have evaluated the feasibility of developing a biodegradable collagenous small diameter vascular graft of 2 mm diameter and 1 cm length. In brief, bi-layer type I collagen membrane was fabricated under vacuum suction and lyophilization methods. The smooth muscle cells were inoculated into the lower side of the porous membrane, while endothelial cells were seeded onto upper smooth side of the membrane. After cultured for 7 days, the vascular substitute was either harvested for in vitro examination or in vivo implanted in the subcutaneous layer for biocompatibility test. The tubular vascular prosthesis was then used as a temporary absorbable guide that served as an in vivo vascular graft to promote the complete regeneration of rat inferior vena cava. After implantation for 12 weeks, a thin continuous layer of endothelial cells and smooth muscle cells were lined with the vascular lumen and tunic media, respectively. Histology results showed that there were no signs of significant thrombogeneity and intima hyperplasia. This tissue engineered vascular substitute not only had enough tensile strength and good biocompatibility, but also advanced vascular regeneration. In the future, we suggest that this biodegradable vascular substitute will provide with the possibility in application on small diameter prosthetic grafts in artificial blood vessels.

Si Etching with High Aspect Ratio and Smooth Side Profile for Mold Fabrication

A silicon etching process for imprint mold fabrication is developed. For the imprint mold, an etching profile with a smooth side wall is fabricated in order to obtain good release characteristics. The alternative process using C4F8 plasma and SF6+O2 plasma is applied using an inductively coupled plasma etcher. The relation between the etching profiles and the process parameters is examined under various etching conditions. A vertical etching profile without a side wall scallop can be obtained at 60% O2 content. A pattern 0.12 µm wide with an aspect ratio of 27 is fabricated. A silicon mold is fabricated by the etching process under good etching conditions. Fine patterns on the mold are transferred to a 2-mm-thick poly(methyl methacrylate) (PMMA) plate by the thermal imprinting. Since a mold pattern with a smooth side wall is used, the mold can be released from the PMMA substrate without difficulty. A fine pattern 0.12 µm in wide is transferred to the PMMA substrate.

Proton beam writing: a tool for high-aspect ratio mask production

P-beam writing (proton beam writing), a direct write 3D nano lithographic technique has been employed for the production of X-ray masks in a single step fabrication process, with high aspect ratios and extremely smooth absorber edges. P-beam writing employs a focused MeV proton beam scanned in a predetermined pattern over a resist (e.g. PMMA or SU-8), which is subsequently chemically developed. P-beam writing in combination with electroplating appears ideally suited to directly write X-ray masks with nano sized features, high aspect ratios, small lateral feature sizes, and smooth and vertical sidewalls. Sub 100 nm resist structures with aspect ratios up 160 have been produced, as well as metallic (nickel) structures down to the 100 nm level. Preliminary tests on p-beam written X-ray test masks show that Ni stencils can be fabricated with a thickness of 2–20 μm, smooth side walls, feature details down to 1 μm, and aspect ratios up to 20.

Mechanical quadrature methods and their extrapolation for solving first kind Abel integral equations

This paper presents high accuracy mechanical quadrature methods for solving first kind Abel integral equations. To avoid the ill-posedness of problem, the first kind Abel integral equation is transformed to the second kind Volterra integral equation with a continuous kernel and a smooth right-hand side term expressed by weakly singular integrals. By using periodization method and modified trapezoidal integration rule, not only high accuracy approximation of the kernel and the right-hand side term can be easily computed, but also two quadrature algorithms for solving first kind Abel integral equations are proposed, which have the high accuracy O ( h 2 ) and asymptotic expansion of the errors. Then by means of Richardson extrapolation, an approximation with higher accuracy order O ( h 3 ) is obtained. Moreover, an a posteriori error estimate for the algorithms is derived. Some numerical results show the efficiency of our methods.

Solid Free-Form Fabrication of Metallic Components

The influence of process parameters on shape stability and surface smoothness of cylindrical and rectangular castings produced by fused spinning deposition (FSD) method was investigated. The optimum conditions to control the shape and smoothness of side surface of the castings produced by the FSD method without water-cooling were limited to a narrow range of process parameters. The casting with a stable shape and a smooth side surface was obtained with the aid of water-cooling. The tensile strength of the castings produced by the FSD method was 1.4 times higher than those of the specimens cast into metal-mold and sand-mold, due to a finer equiaxed grain structure of the FSD castings. Employing the combination of the deposition patterns for tube and solid castings, some practical metallic components were fabricated by the FSD method.

Surface Morphology and Island Shape of MOVPE Grown InGaN Nano-Island Ensembles Studied by STM

The dependence of the InGaN/GaN(0001) surface morphology on the growth parameters of metal organic vapour phase epitaxy (MOVPE) at 650°C has been investigated using scanning tunneling microscopy. After deposition of InGaN under In-rich growth conditions, a preferential nucleation of islands at defects of the GaN substrate film is found. The islands have a large size (diameter ~ 80 nm, height ~10 nm) and show a spiral disc-like shape with an atomically flat surface, and the wetting layer surface appears very smooth. For thicker InGaN layers, In-droplets are formed on top of the large islands and the wetting layer becomes rougher. For InGaN growth at a reduced In partial pressure, hexagonal islands with an atomically flat top surface are formed and pyramidal islands of triangular base with smooth side facet structures are observed. The effects of growth rate and V/III flux ratio on the InGaN surface morphology have also been studied and the results indicate that a slower growth reduces the large island formation probability whereas a high V-III flux ratio enhances it. All findings are discussed in terms of thermal diffusion, In-incorporation and thermal decomposition.

Hydrothermal synthesis of single-crystalline hexagonal prism ZnO nanorods

In the present work, single-crystalline hexagonal prism ZnO nanorods have been successfully synthesized via a PEG-assisted hydrothermal route at 140 °C. The structure of the products has been characterized by XRD. TEM and SEM images indicated that the as-synthesized nanorods are wurtzite ZnO with diameters ranging from 60 to 120 nm and lengths of hundreds of nanometers. The smooth prismatic side planes and tips of the rods have been observed. The results also show that short-chain polymer PEG plays a crucial role in the formation of 1D ZnO nanostructures. This facile, reproducible, and effective low-cost approach should promise us a future large-scale synthesis of ZnO nanostructures for many important applications in nanotechnology.

Characterization of ZnO/diamond SAW devices elaborated on the smooth nucleation side of MPACVD diamond

AbstractWe designed a SAW filter in this work by combining the piezoelectric ZnO film with a freestanding double layer diamond film deposited using CH4–H2 pulsed MPACVD process through two growth stages. The AFM measurements on the nucleation side of the diamond film has shown that this side is smooth enough to perform photolithography process in the SAW device elaboration, while the good quality of the diamond film produced on this side has been confirmed through Raman spectroscopy.Furthermore, the ZnO films having their c axis perpendicular to the substrate were deposited using reactive magnetron sputtering under the optimal experimental conditions found from XRD measurements. In the SAW device elaboration on this ZnO/bilayer diamond structure, aluminium interdigital transducers (IDTs) were developed by conventional contact UV photolithography on the nucleation side of the freestanding diamond. The frequency response of the device presents harmonics of the acoustic wave modes propagating in the smooth diamond nucleation side. The good agreement obtained between the experimental and theoretical frequency responses attests that the elastic properties of the ZnO and the diamond are similar to those of the single crystal assumed in the theoretical study. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Sildenafil: efficacy, safety, tolerability and mechanism of action in treating erectile dysfunction

Sildenafil citrate is marketed under the trademark name Viagra® and is widely used to treat male erectile dysfunction; therapeutic uses of this medication for other diseases related to vascular dysfunction are emerging. When used as recommended, the drug has a strong clinical efficacy and safety profile in a broad spectrum of the male population. Its widespread use and effects of long-term exposure to the drug due to particular treatment regimens or inappropriate use mandate an ongoing update of its molecular mechanism, pharmacological profile and associated safety issues. This review focuses on biochemical and pharmacological features of sildenafil, the active component in Viagra, interaction of sildenafil with phosphodiesterase 5, pharmacokinetic parameters, action in smooth muscle, side effects, safety profile and prospects for other uses.

Human embryoid body-derived stem cells in co-culture with bladder smooth muscle and urothelium

Objectives Human pluripotent stem cells have excellent regenerative abilities, making them attractive in bladder regeneration. Porcine small intestinal submucosa (SIS) is an established matrix well-suited to the urinary tract. We evaluated the ability of human embryonic germ (hEG) cell-derived stem cells to form a composite graft on SIS, grown alone or in combination with human bladder smooth muscle cells (SMCs) or urothelial (URO) cells. Methods The hEG cell-derived cell line SDEC had the best-fit profile for smooth muscle, as determined by its gene and protein expression. SDEC cells were seeded on SIS, either on its serosal or mucosal surface, and cultured for 7 or 14 days. Co-cultures of stem cells with URO cells or SMCs were also assessed under similar conditions. The grafts were analyzed by histologic examination for cell growth, morphology, and matrix penetration. Results SDEC cells grew in a monolayer on SIS, with a marked increase in three-dimensional growth when co-cultured with URO cells or SMCs. Penetration of the matrix was evident when seeded on the rough surface of the SIS, progressing with time. Stratification of the cell layers occurred on the smooth side of the SIS. Conclusions This is the first description of hEG cell-derived stem cells in co-culture with bladder cells. hEG cell-derived stem cells grow well on SIS even when seeded at low concentrations in the presence of bladder cells (URO cells or SMCs). These composite grafts will be ideal to evaluate the in vivo functional characteristics of stem cells using an animal model of bladder regeneration.

Proton beam writing using the high energy ion nanoprobe LIPSION

Proton beam writing (PBW) is a very unique technique capable of the direct creation of three dimensional structures with a very high aspect ratio. Since the high energy ion nanoprobe LIPSION has a very high spatial resolution and is therefore well suited for the creation of structures in the micrometre range or below, it is planned to establish the PBW technique at the University of Leipzig. The results of the first proton beam writing experiments at the LIPSION nanoprobe are presented in this article. Structures with high aspect ratio and smooth side walls with an edge definition of ∼0.2μm were created in negative SU-8 photo resist using 2.25MeV protons. Furthermore, investigations were carried out concerning the mechanical stability of single free standing walls in order to collect information for the targeted production of samples with smaller feature sizes in the submicrometre range. Up to now, wall widths down to 1.5μm were achieved. However, smaller feature sizes could not be obtained due to beam spot fluctuations which enlarge the wall width by a factor of three. Self-supported structures were produced using 2.25MeV protons and subsequently 1.5MeV helium ions demonstrating the stability and accuracy of these real three dimensional structures. In addition, different methods for online dose normalization were tested showing that ionoluminescence is the most suitable method for this purpose.

Optimization of Back Side Cleaning Process to Eliminate Copper Contamination

Copper (Cu) contamination at the wafer bevel, back side surface, and exclusion zone is identified step-by-step following a typical dual-damascene process. The shield ring of a physical vapor deposition system does not protect the exclusion zone and bevel efficiently. Also, Cu may dissolve and accumulate in the solvent used for post dielectric etch clean. Dissolved Cu atoms may then redeposit on the wafer surface. Furthermore, the rough back side surface traps Cu atoms easier than the smooth front side surface. If there is no film on the back side surface, post chemical mechanical polish cleaning using dilute HF cannot remove Cu at the back side surface. An optimized single-wafer spin-etch process was proposed. An optimal etchant consisting of HF, and with ratios 0.5:3:1:0.5 showed excellent performance. Experiments demonstrated that a very short, 10 s, back side clean can totally remove Cu from back side surface, bevel, and 2 mm exclusion zone. A “wafer shift” procedure was also proposed to solve the pinmark issue near the edge pin due to etchant remnant. The optimized cleaning technique shows shorter process time and higher cleaning efficiency than those reported previously. © 2005 The Electrochemical Society. All rights reserved.

Densoisporites polaznaensis sp. nov. with comments on its relation to Viatcheslavia vorcutensis Zalessky

A new species of lycopsid microspores, Densoisporites polaznaensis., is described. The spores were extracted from clayey matrix containing stems and phylloids of Viatcheslavia vorcutensis Zalessky, a characteristic lepidophyte of the lowermost Upper Permian (Solikamskian) of the Ural Mountains and Russian Platform. The fossils studied came from the Polazna Locality of the Ufimian (Roadian) age, situated near Perm City, Russia. The spores of D. polaznaensis are 30-69 µm, round to subtriangular, having almost smooth proximal side with clearly visible trilete scar with rays extended to the spore equator. Distal side of the spores has a fine granulate relief, formed by widely spaced distinct granulae. The sporoderm is two-layered; the outer layer consists of numerous interlaced lamellae and the inner layer includes a single lamella. At some sections, in the central region of spores, "laminated zones" were detected in the inner layer. There is a weakly developed cavity in the sporoderm. Viatcheslavia vorcutensis is represented by wide stem fragments (up to 30 cm in diameter). Leaf cushions are present on old lowermost stem parts, but any attached phylloids/sporophylls were not found, the phylloids/sporophylls obviously were shed. Leaf cushions usually are round, with clear scar of leaf attachment and ligular depression on the upper margin of the cushion. Two small areas of parenchymatous tissues (possible parichnos) are occasionally seen. On the basis of cooccurrences and typological extrapolation with related taxa of lycophytes belonging to the family Pleuromeiaceae, it is suggested that microspores of Densoisporites polaznaensis were produced by Viatcheslavia vorcutensis. The palaeoecology of Viatcheslavia vorcutensis interpreted as a halophytic plant is discussed.

Macro‐scale bed roughness of the siple coast ice streams in West Antarctica

AbstractSubglacial bed conditions are key to understanding ice stream behaviour and evolution, with bed roughness reflecting substrate composition and flow resistance. Here we present an analysis of bed roughness in the Siple Coast region of West Antarctica from airborne radio‐echo sounding data. The ice streams are associated generally with low bed roughness values, which decrease downstream. The bed of the slow‐flowing Ice Stream C (∼10 000 km2) is also characterized by being smooth at all scales (wavelengths ranging from 5 km to in excess of 40 km). Furthermore, the bed is smooth either side of Ice Stream C. This suggests the location of the ice stream is controlled by internal ice sheet dynamics rather than by bed morphology. If the ice stream were encouraged to migrate laterally, when active, there would be little resistance offered by the subglacial morphology. Other inter‐ice stream regions are rough, however, indicating a subglacial topographic influence on ice stream position. Bed roughness increases up‐flow of ice streams, which, unless the bed is modified, may limit the inland migration of these systems. Copyright © 2004 John Wiley & Sons, Ltd.

Fabrication of high aspect ratio 100nm metallic stamps for nanoimprint lithography using proton beam writing

We report a way of fabricating high-quality void-free high-aspect-ratio metallic stamps of 100nm width and 2μm depth, using the technique of proton beam writing coupled with electroplating using a nickel sulfamate solution. Proton beam writing is a one-step direct-write process with the ability to fabricate nanostructures with high-aspect-ratio vertical walls and smooth sides, and as such has ideal characteristics for three-dimensional (3D) stamp fabrication. Nanoindentation and atomic force microscopy measurements of the nickel surfaces of the fabricated stamp show a hardness and side-wall roughness of 5GPa and 7nm, respectively. The fabricated 100nm 3D stamps have been used to transfer test patterns into poly(methylmethacrylate) films, spin coated onto a silicon substrate. Proton beam writing coupled with electroplating offers a process of high potential for the fabrication of high quality metallic 3D nanostamps.

The effect of substrate roughness on air entrainment in dip coating

Dynamic wetting failure was observed in the simple dip coating flow with a series of substrates, which had a rough side and a comparatively smoother side. When we compared the air entrainment speeds on both sides, we found a switch in behaviour at a critical viscosity. At viscosity lower than a critical value, the rough side entrained air at lower speeds than the smooth side. Above the critical viscosity the reverse was observed, the smooth side entraining air at lower speed than the rough side. Only substrates with significant roughness showed this behaviour. Below a critical roughness, the rough side always entrained air at lower speeds than the smooth side. These results have both fundamental and practical merits. They support the hydrodynamic theory of dynamic wetting failure and imply that one can coat viscous fluids at higher speeds than normal by roughening substrates. A mechanism and a model are presented to explain dynamic wetting failure on rough surfaces.

Surface acoustic wave properties of freestanding diamond films

"Ideal" diamond has the highest acoustic velocity of any material known, and is of great interest as a substrate material for high frequency surface acoustic wave (SAW) device structures. However, little is known of the acoustic wave propagation properties of polycrystalline diamond grown by chemical vapour deposition (CVD) techniques, the commercially accessible form of this material. We report on propagation of laser-generated SAW on three forms of freestanding CVD diamond samples, "white" polycrystalline, "black" polycrystalline, and "highly oriented" diamond. Despite differing sample nature, SAW waves propagating along the smooth (nucleation) side of the diamond showed similar velocities in the range 10600-11900 ms(-1). These results are discussed in terms of the potential of each form of CVD diamond for SAW device fabrication.

Proton beam writing: a progress review

A new direct write 3D nano lithographic technique has been developed at the Centre for Ion Beam Applications (CIBA) in the Physics Department of the National University of Singapore. This technique employs a focused MeV proton beam which is scanned in a predetermined pattern over a resist (e.g. PMMA or SU-8), which is subsequently chemically developed. The secondary electrons induced by the primary proton beam have low energy and therefore limited range, resulting in minimal proximity effects. Low proximity effects coupled with the straight trajectory and high penetration of the proton beam enables the production of 3D micro and nano structures with well-defined smooth side walls to be directly written into resist materials. In this review the current status of proton beam writing will be discussed; recent tests have shown this technique capable of writing high aspect ratio walls up to 160 and details down to 30 nm in width with sub-3 nm edge smoothness.

Non-polar interactions between cholesterol and phospholipids: a molecular dynamics simulation study

A 15-ns molecular dynamics simulation of the fully hydrated dimyristoylphosphatidylcholine-cholesterol (DMPC-Chol) bilayer containing ∼22 mol% Chol was carried out. An 8-ns trajectory was analysed to investigate the effect of Chol on the chain packing in the bilayer core. While the packing of DMPC chains on the smooth α-face side of the Chol ring is similar to that in the pure DMPC bilayer, the packing on the rough β-face side is less regular and less tight. Two methyl groups located on the Chol β-face disturb the packing; in effect, van der Waals (vdW) interactions between Chol rings and DMPC chains are weaker than the ones between sole DMPC chains. VdW interactions between an alkyl chain of DMPC and an isooctyl tail of Chol are similarly strong as those between two DMPC chains.

Non-polar interactions between cholesterol and phospholipids: a molecular dynamics simulation study

A 15-ns molecular dynamics simulation of the fully hydrated dimyristoylphosphatidylcholine-cholesterol (DMPC-Chol) bilayer containing ∼22 mol% Chol was carried out. An 8-ns trajectory was analysed to investigate the effect of Chol on the chain packing in the bilayer core. While the packing of DMPC chains on the smooth α-face side of the Chol ring is similar to that in the pure DMPC bilayer, the packing on the rough β-face side is less regular and less tight. Two methyl groups located on the Chol β-face disturb the packing; in effect, van der Waals (vdW) interactions between Chol rings and DMPC chains are weaker than the ones between sole DMPC chains. VdW interactions between an alkyl chain of DMPC and an isooctyl tail of Chol are similarly strong as those between two DMPC chains.