Experimental verification of failure of Amontons' law in polymeric textiles

The dynamic friction of a variety of textile materials was studied and was experimentally proven that the frictional behavior of textile materials do not obey the Amontons' basic law of friction (F/N = μ). Both woven and nonwoven materials with different fiber content and constructional features were used in the study. Results show that the dynamic friction–normal load relationship is not a straight line passing through origin. A statistical approach has been followed to prove the significance of the deviation from the Amontons' law. To the authors' best knowledge, the work reported in this article has for the first time experimentally proven the failure of Amontons' basic law of friction for polymeric textiles, using a novel approach. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3879–3885, 2004     

Numerical prediction of fluid flow and heat transfer in a wavy pipe

IntroductionA pipe with periodically converging-divergingcross-section is one Of the sevens devices employed forenhancing the heat and mass tusfer efficiency. Thenuid flow, to the now passages with a periodicallyvaling cross-section, attains a folly develOPed acmethat differs fundamentally from that for a convelltionalconstant-area flow channel. In the periodically vwigcross-seCtions, the ac developed VelM field repeatsitSelf at cormsponding edal locations in successivecycles. The change of…     

Antibacterial responses of zinc oxide structures against Staphylococcus aureus, Pseudomonas aeruginosa and Streptococcus pyogenes

The antibacterial responses of zinc oxide (ZnO) structures against Staphylococcus aureus, Pseudomonas aeruginosa, and Streptococcus pyogenes were investigated. Two ZnO powder samples, one with rod-like (ZnO-1) and the other with plate-like (ZnO-2) structures, were characterized for their morphological, structural, and optical properties. The rods were 30–120 nm in diameter, and the plates were 40–100 nm thick. XRD results revealed the wurtzite crystallinity of ZnO with average crystallite sizes of 33.72 (ZnO-1) and 39.25 (ZnO-2) nm. ZnO-2 possessed a relatively higher green photoluminescence than that of ZnO-1, suggesting a relatively higher amount of oxygen vacancies in ZnO-2 structures. Optical density measurements showed that both ZnO samples inhibited the growth of S. aureus, P. aeruginosa, and S. pyogenes by 29–98% after 24 h of treatment. The most dramatic growth inhibition was observed in S. pyogenes with 96% and 98% inhibition for ZnO-1 and ZnO-2, respectively, leading to a probable bactericidal phenomenon. The toxicological effect on S. pyogenes was probably due to the absence of catalase, making the bacteria vulnerable to the harmful reactive oxygen species (ROS) released by ZnO. ZnO-1 induced higher inhibition toward S. aureus and P. aeruginosa than that of ZnO-2 because of the smaller particle size of rod structures compared to plate and slab structures. The adhesion of ZnO particles on the membrane of bacteria could be the underlying cause of zinc toxicity effect towards the bacteria. ZnO-1 possessed larger surface area and provided higher amount of zinc atom, thereby inducing higher level of toxicity toward the bacteria. Two possible mechanisms were proposed to explain the inhibition of bacteria, namely, ROS toxicity toward cellular constituents and interaction of zinc with bacteria membrane through adhesion of ZnO particle. Several ZnO morphological-antibacterial correlations were presented in this work.     

A decentralised multi-agent approach to enhance the stability of smart microgrids with renewable energy

This paper presents the impact of large penetration of wind power on the transient stability through a dynamic evaluation of the critical clearing times (CCTs) by using intelligent agent-based approach. A decentralised multi-agent-based framework is developed, where agents represent a number of physical device models to form a complex infrastructure for computation and communication. They enable the dynamic flow of information and energy for the interaction between the physical processes and their activities. These agents dynamically adapt online measurements and use the CCT information for relay coordination to improve the transient stability of power systems. Simulations are carried out on a smart microgrid system for faults at increasing wind power penetration levels and the improvement in transient stability using the proposed agent-based framework is demonstrated.     

Influence of anisotropic stress states on the thermal volume change of unsaturated silt

This study is focused on understanding the influence of anisotropic stress states on the thermal volume change of unsaturated, compacted silt specimens. A thermo-hydro-mechanical true-triaxial cell was used that permits control of the temperature on all six boundaries of a cubical soil specimen as well as control of the suction within the specimen to provide drained conditions during mechanical loading and temperature changes. Six non-isothermal tests were performed as part of this study, each involving suction application, consolidation to a given isotropic or anisotropic stress state, heating and cooling in stages under drained conditions, and unloading. Specifically, tests having minor to major principal stress ratios of 1.0, 0.7, and 0.5 were performed on specimens having initial degrees of saturation of 0.7 and 0.8, complementing tests on the same soil under similar stress states but saturated conditions published in a previous study. Although compressive thermal axial strains were measured in both the major and minor stress directions, a greater thermal axial strain was observed in the direction of the major principal stress for stress ratios less than 1.0. However, similar thermal volumetric strains were observed in all of the tests regardless of the stress state. A small effect of inherent anisotropy was observed due to the formation of the specimens using compaction. Specimens with a lower initial degree of saturation experienced greater thermal volume changes than specimens closer to saturation, possibly due to thermal collapse of the air-filled voids during heating or thermally accelerated creep after application of a given plastic strain during mechanical loading. An empirical relationship to consider the effects of anisotropic stress states and variable saturation was incorporated into an established elasto-plastic model developed for saturated soils under isotropic conditions, and a good fit was obtained between the measurements and predictions.     

Organic matter-solid phase interactions are critical for predicting arsenic release and plant uptake in Bangladesh paddy soils

Agroecological zones within Bangladesh with low levels of arsenic in groundwater and soils produce rice that is high in arsenic with respect to other producing regions of the globe. Little is known about arsenic cycling in these soils and the labile fractions relevant for plant uptake when flooded. Soil porewater dynamics of field soils (n = 39) were recreated under standardized laboratory conditions to investigate the mobility and interplay of arsenic, Fe, Si, C, and other elements, in relation to rice grain element composition, using the dynamic sampling technique diffusive gradients in thin films (DGT). Based on a simple model using only labile DGT measured arsenic and dissolved organic carbon (DOC), concentrations of arsenic in Aman (Monsoon season) rice grain were predicted reliably. DOC was the strongest determinant of arsenic solid-solution phase partitioning, while arsenic release to the soil porewater was shown to be decoupled from that of Fe. This study demonstrates the dual importance of organic matter (OM), in terms of enhancing arsenic release from soils, while reducing bioavailability by sequestering arsenic in solution.     

Extraction of natural dyes for textile dyeing from coloured plant wastes released from the food and beverage industry

The food and beverage industry releases considerable amounts of wastes which contain natural dyes. Such wastes could serve as a sources for the extraction of natural dyes for textile‐dyeing operations. The extraction of brilliant yellow and red colours from fruits and vegetables is of particular interest. Wastes, e.g. pressed berries, pressed grapes, distillation residues from strong liquor production, and wastes and peels from vegetable processing, have been extracted with boiling water and test dyeings on wool yarn were performed. Colour strength, shade and fastness properties of the dyeings have been tested. The extracts were applied as direct dyes and in the presence of iron(II) or alum mordants. The results prove the potential of such wastes as a source for natural dyestuff extraction. To obtain textile dyeings with acceptable fastness properties, however, rigorous selection of dyes and development of suited processes is required. A considerable number of red natural dyes need further research to optimise the low level of fastness to light. Copyright © 2005 Society of Chemical Industry     

Follow-up of patients with superior vena cava syndrome by functional analysis of radionuclide venography

The postnatal development of rat sublingual glands was analyzed by morphometric and radioautographic studies. The absolute number of each cell type was evaluated by the Aherne II morphometric method for cell counting and labeling indices of these cell types were determined in radioautographs from animals injected with 3H-thymidine. The quantitative cell population kinetic studies were accompanied by morphologic analysis of the modifications in each gland structure. The data concerning evolution of number of each cell type were submitted to analysis by least squares fit-exponential curve. The exponential equations duplication times for the acinar, serous demilune, intercalated duct, striated duct and stroma cells from 2 to 30 days of age were 7.5, 9.0, 10.8 and 9.5 days, respectively. On the other hand, the mean labeling indices for the same cell types during the same period were 9.5%, 5.8%, 7.2%, 3.3% and 4.3%, respectively. Thus, the intercalated duct cells exhibited the second highest labeling index and the slowest growth rate, while the striated duct cells showed the lowest labeling index and the third highest duplication time. The fact that the striated duct cell labeling index does not explain the relatively short duplication time of these cells, suggests that cells from other neighboring morphologic compartments, probably from intercalated duct, migrate and differentiate into striated ducts cells.     

Effect of Steareth-20 on the Release of Nitrofurantoin from Propylene Glycol Monostearate Microspheres

In vitro release of nitrofurantoin (NFT) from microspheres of propylene glycol monostearate (PGM) was investigated at NFT:PGM ratios of 1:1, 1:1.5, 1:3, 1:4, 1:5, and 1:9 in distilled water at 37°C. The rate and extent of drug release declined with decreasing NFT:PGM ratio. A maximum drug release of 52.4% over 24 hr was recorded for the microspheres of formulation I (highest load). The effect of Steareth-20 (ESA) over the concentration range of 0.01% to 0.1% w/w of PGM on the size of the microspheres and on the release profile of nitrofurantoin from the microsphere formulations was examined at NFT.PGM ratios of 1:1 and 1:4. The cumulative % of NFT released over a 24-hr period was found to be maximum at ESA concentration of 0.03% and 0.05% w/w of PGM. The plots of T₅₀ versus %w/w of ESA exhibited two minima, the first at 0.03% ESA and a second, weaker than the first, at 0.05% ESA, paralleling the earlier observations. Scanning electron micrographs of the exhausted microspheres revealed a very porous matrix of PGM at the ESA concentration of 0.03%. The formulations containing 0.03% and 0.05% ESA had the smallest mean particle diameter and the minimum contact angles (water over PGM-ESA films) corresponding to the two critical micelle concentrations (CMC), at 0.025% and 0.05% w/w.     

A study on the mechanical and electrical reliability of individual carbon nanotube field emission cathodes

Individual carbon nanotube (CNT) field emission characteristics present a number of advantages for potential applications in electron microscopy and electron beam lithography. Mechanical and electrical reliability of individual CNT cathodes, however, remains a challenge and thus device integration of these cathodes has been limited. In this work, we present an investigation into the reliability issues concerning individual CNT field emission cathodes. We also introduce and analyze the reliability of a novel individual CNT cathode. The cathode structure is composed of a multi-walled carbon nanotube (MWNT) attached by Joule heating to a nickel-coated Si microstructure. The junction of the CNT and the Si microstructure is mechanically and electrically robust to withstand the strong electric field conditions that are typical for field emission devices. An optimal Ni film coating of 25?nm on the Si microstructure is required for mechanical and electrical stability. Experimental current-voltage data for the new cathode structure definitively demonstrates carbon nanotube field emission. Additionally, we demonstrate that our new nanofabrication method is capable of producing sophisticated cathode structures that were previously not realizable, such as one consisting of two parallel MWNTs, with highly controlled CNT lengths with 40?nm accuracy and nanotube-to-nanotube separations of less than 10?μm.