The synthesis of carbon nanostructures from tea plant wastes

Tea wastes are rich in carbon, nitrogen and potassium but poor in phosphorus, which signifies that they can also be used to reduce metal oxides after they are carbonised. The tea wastes were carbonised at the first stage. The sample, which was put into a ladle with screw cap, was carbonised in a muffle furnace at 400, 500, 600, 700 and 800°C for 30, 60, 90, 120, 240, 360, 720 and 1440?min. It was determined that carbon and sulphur contents of the sample carbonised at 800°C for 1440?min were 94.68 and 0.05%, respectively. Calorific value of the same sample was 8652?cal?g^?1. It was found that with increasing temperature, carbon ratio of the carbonised samples increased and their sulphur ratio decreased from 0.39 to 0.05%. The carbonised structure was subjected to the milling process as the second stage. In the milling process, particle size of the carbon-rich sample was brought into nano size and the structure acquired the energy, required for the third stage. The amorphous carbon structure obtained after the milling process was subjected to annealing process at 1400°C as the third stage. As a result of these processes, carbon nanotubes (CNTs), carbon nano-onion structures and amorphous carbon structures were determined in the structure.     

Vanadium oxide solubility in CaO–SiO2–VOX system

The solubility of vanadium oxide in the SiO₂–CaO–VO_X system was investigated as a function of basicity (CaO/SiO₂) at a fixed temperature of 1600°C and oxygen partial pressure of 10^?10?atm. Formed phases and microstructures of saturated samples were identified with SEM–EDS analysis and XRD. Maximum solubility of vanadium oxide was between 15 and 20% independent of basicity. Pure karelianite (V₂O₃) was formed in all samples at saturation of vanadium oxide. The morphology of karelianite changed with the change in basicity in the slag, where needles or threads were formed for slags with basicity B2?=?0.54 and B2?=?0.67 and stars or dendritic patterns were formed with basicity B2?=?1.0 and B2?=?1.22. Wollastonite (CaSiO₃) was also formed in the slags with star or dendritic patterns.     

Moisture uptake and hygroexpansion of wood fiber composite materials with polylactide and polypropylene matrix materials

Effects of butantetracarboxylic acid (BTCA) modification, choice of matrix, and fiber volume fraction on hygroexpansion of wood fiber composites have been investigated. Untreated reference wood fibers and BTCA‐modified fibers were used as reinforcement in composites with matrices composed of polylactic acid (PLA), polypropylene (PP), or a mixture thereof. The crosslinking BTCA modification reduced the out‐of‐plane hygroexpansion of PLA and PLA/PP composites, under water‐immersed and humid conditions, whereas the swelling increased when PP was used as matrix material. This is explained by difficulties for the BTCA‐modified fibers to adhere to the PP matrix. Fiber volume fraction was the most important parameter as regards out‐of‐plane hygroexpansion, with a high‐fiber fraction leading to large hygroexpansion. Fiber‐matrix wettability during processing and consolidation also showed to have a large impact on the dimensional stability and moisture uptake. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Parallel eigenvalue reordering in real Schur forms

A parallel algorithm for reordering the eigenvalues in the real Schur form of a matrix is presented and discussed. Our novel approach adopts computational windows and delays multiple outside‐window updates until each window has been completely reordered locally. By using multiple concurrent windows the parallel algorithm has a high level of concurrency, and most work is level 3 BLAS operations. The presented algorithm is also extended to the generalized real Schur form. Experimental results for ScaLAPACK‐style Fortran 77 implementations on a Linux cluster confirm the efficiency and scalability of our algorithms in terms of more than 16 times of parallel speedup using 64 processors for large‐scale problems. Even on a single processor our implementation is demonstrated to perform significantly better compared with the state‐of‐the‐art serial implementation. Copyright © 2009 John Wiley & Sons, Ltd.     

Wear Mechanisms in Galling: Cold Work Tool Materials Sliding Against High-strength Carbon Steel Sheets

Transfer and accumulation of adhered sheet material, generally referred to as galling, is the major cause for tool failure in sheet metal forming. In this study, the galling resistances of several tool steels were evaluated against dual-phase high-strength carbon steel using a SOFS tribometer, in which disc-shaped tools were slid against a real sheet surface in dry sliding test conditions. Three different frictional regimes were identified and characterized during sliding, and any transition in friction corresponded to a transition in wear mechanisms of the sheets. The performance of the tools depended on load, material and the particular frictional regime. Best overall performance was obtained by nitrogen-alloyed powder metallurgy tool steel.     

Emissions of sesquiterpenes from spruce sawdust during drying

Large amounts of sawdust are dried to produce particleboard and pellets. During drying and densification, volatile organic compounds are emitted. These may contribute to the formation of tropospheric ozone. In this study, sesquiterpene emissions from Norway spruce sawdust dried in a continuous spouted bed at 140–200?°C have been investigated, and patterns of co-variation between sesquiterpene emissions and drying parameters have been elucidated. For sawdust dried to moisture contents suitable for pellets production, about 10–20?mg sesquiterpenes were emitted per kg oven dry sawdust. The sesquiterpene emissions amounted to about 20% of the monoterpene emissions. Drying at 200 °C caused markedly larger sesquiterpene emissions than did drying at 140 or 170 °C. The sesquiterpene emissions increased considerably at low wood moisture contents. While it has long been known that monoterpenes are emitted during the processing of wood, this study shows that sesquiterpenes are of considerable importance too.     

Nanosized fibers' effect on adult human articular chondrocytes behavior

Tissue engineering with chondrogenic cell based therapies is an expanding field with the intention of treating cartilage defects. It has been suggested that scaffolds used in cartilage tissue engineering influence cellular behavior and thus the long-term clinical outcome. The objective of this study was to assess whether chondrocyte attachment, proliferation and post-expansion re-differentiation could be influenced by the size of the fibers presented to the cells in a scaffold. Polylactic acid (PLA) scaffolds with different fiber morphologies were produced, i.e. microfiber (MS) scaffolds as well as nanofiber-coated microfiber scaffold (NMS). Adult human articular chondrocytes were cultured in the scaffolds in vitro up to 28 days, and the resulting constructs were assessed histologically, immunohistochemically, and biochemically. Attachment of cells and serum proteins to the scaffolds was affected by the architecture. The results point toward nano-patterning onto the microfibers influencing proliferation of the chondrocytes, and the overall 3D environment having a greater influence on the re-differentiation. In the efforts of finding the optimal scaffold for cartilage tissue engineering, studies as the current contribute to the knowledge of how to affect and control chondrocytes behavior.     

Temperature dependence of cohesive laws for an epoxy adhesive in Mode I and Mode II loading

The influence of the temperature on the cohesive laws for an epoxy adhesive is studied in the glassy region, i.e. below the glass transition temperature. Cohesive laws are derived in both Mode I and Mode II under quasi-static loading conditions in the temperature range $-30\le T \le 80^{\,\circ }$ C. Three parameters of the cohesive laws are studied in detail: the elastic stiffness, the peak stress and the fracture energy. Methods for determining the elastic stiffness in Mode I and Mode II are derived and evaluated. Simplified bi-linear cohesive laws to be used at any temperature within the studied temperature range are derived for each loading mode. All parameters of the cohesive laws are measured experimentally using only two types of specimens. The adhesive has a nominal layer thickness of 0.3 mm and the crack tip opening displacement is measured over the adhesive thickness. The derived cohesive laws thus represent the entire adhesive layer as having the present layer thickness. It is shown that all parameters, except the Mode I fracture energy, decrease with an increasing temperature in both loading modes. The Mode I fracture energy is shown to be independent of the temperature within the evaluated temperature span. At $80^{\,\circ }$ C the Mode II fracture energy is decreased to about 2/3 of the fracture energy at $-30^{\,\circ }$ C. The experimental results are verified by finite element analyses.     

PNIPAAm-grafted thermoresponsive microcarriers: Surface-initiated ATRP synthesis and characterization

In this study, we developed novel thermoresponsive microcarriers as a powerful tool for cell culture and tissue engineering applications. For this purpose, two types of commercially available spherical microparticles (approximately 100 μm in diameter), dextran-based Sephadex® and vinyl acetate-based VA-OH (Biosynth®), were used and themoresponsive poly(N-isopropylacrylamide) (PNIPAAm) was grafted to the beads' surfaces by surface-initiated atom transfer radical polymerization (SI-ATRP). Initially, hydroxyl groups of microbeads were reacted with 2-bromopropionyl bromide to form ATRP macroinitiator. Then, NIPAAm was successfully polymerized from the initiator attached microbeads by ATRP with CuBr/2,2′-dipyridyl, catalyst complex. Furthermore, grafted and ungrafted microbeads were characterized by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, scanning electron microscope (SEM), atomic force microscopy (AFM) and electron spectroscopy for chemical analysis (ESCA). The results of characterization studies confirmed that PNIPAAm was successfully grafted onto both dextran and vinyl acetate-based beads by means of ATRP reaction and thus, grafted microbeads gained thermoresponsive characteristics which will be evaluated for cell harvesting in further studies.