The efficiency of the oxidation of carbon nanofibers with various oxidizing agents

The oxidation of carbon nanofibers (CNFs) with various oxidizing agents; 6 M HNO₃, KMnO₄, RuO₄, and a mixture of concentrated H₂SO₄/HNO₃ is studied to determine the reaction conditions that optimizes yield and chemical functionalization. The oxidized nanofibers were examined by scanning electron microscopy, and Raman spectroscopy to characterize the defects caused by oxidation. The amount of acidic sites generated during oxidative treatment was quantified by reacting them with amine terminated octadecane and the subsequent quantification of the products of this grafting process by Fourier transform infrared spectroscopy. The concentrated H₂SO₄/HNO₃ mixture created the maximum number of carboxylic acid groups and the highest amount of defect sites, but had very low yield (∼12%). Six molar of HNO₃ generated fewer defect sites and a lower number of -COOH groups, but did exhibit a 70% yield. RuO₄ and KMnO₄ resulted in similar amounts of overall defect sites, however the yield and amount of -COOH groups for KMnO₄ treated CNF were significantly lower than the RuO₄ treatment. Overall, oxidation of these CNF with RuO₄ provides the best balance of yield and carboxylation.     

Fungal colonization and biochemical changes in coffee beans undergoing monsooning

Changes in the mycofloral composition and concentrations of proteins, reducing sugars, phenols and tannins in coffee beans were analysed during different weeks of monsooning in Coffea arabica L. (Arabica) and C. canephora Pierre ex Froehner (Robusta). The highest fungal populations occurred during the fourth to seventh week of the monsooning process and the dominant fungal species were Aspergillus niger, Aspergillus tamarii, Aspergillus candidus, Penicillium spp. and Absidia heterospora. The protein and reducing sugar content increased steadily while the tannin content decreased beyond the detectable limit during monsooning. The phenolic content, however, was found to decline in the case of Robusta and increase slightly in Arabica. Throughout the study the monsooned coffee beans had different mycoflora and varied biochemical composition compared to non-monsooned coffee beans.     

Interfacial Behavior and Debonding Failures in FRP-Strengthened Concrete Slabs

It has been demonstrated, through laboratory investigations and various field projects, that the external bonding of fiber- reinforced polymer (FRP) laminates is an effective technique for the structural enhancement of reinforced concrete slabs. In such applications, failure is generally governed by debonding of the FRP laminate. Nevertheless, numerical simulations to date of FRP-strengthened slabs have usually been based on the assumption of full bond between the concrete and FRP. In this study, the interfacial behavior between the FRP laminates and the concrete substrate is accounted for by introducing appropriate bond-slip models for the interface in a nonlinear finite-element analysis of FRP-strengthened two-way slabs. The numerical model is capable of simulating slabs strengthened in shear or in flexure; it can be applied to arbitrary FRP configurations, and can also accommodate both passive as well as prestressed FRP strengthening schemes. Results are presented in terms of load-deflection relationships, ultimate load capacities, failure modes, and interfacial slip and stress distributions. When compared to test results reported in the literature, the analysis is shown to lead to excellent predictions in that, for the entire set of FRP-strengthened specimens considered, the average of the numerical-to-experimental load capacity ratios is 0.966, with a standard deviation of 0.066. Furthermore, in all cases when FRP debonding was observed experimentally, the analysis correctly predicted the mode of failure.     

Single-layer-coated beam splitters for the division-of-amplitude photopolarimeter

A design procedure is presented for a near-optimal, single-layer-coated prism beam splitter that serves as the key optical element of the division-of-amplitude photopolarimeter (DOAP). For given film and substrate refractive indices, the angle of incidence and film thickness are selected such that the ellipsometric differential phase shifts in reflection and transmission deltar, and deltat, differ by +/- pi/2, and the normalized determinant of the instrument matrix is maximized. The best results are obtained by using high-index films on low-index substrates. This is illustrated by examples of ZnS and GaP films on silica prisms in the visible and Si, Ge, and PbTe films on Irtran 1 substrates in the infrared. A 16 degrees Si-prism DOAP beam splitter at the 1.55-microm lightwave-communications wavelength is also presented. It uses a 163-nm SiO2 coating on the entrance face to satisfy the optimum delta condition at 73 degrees incidence, and the determinant of the instrument matrix is 78.23% of its theoretical maximum. The exit face of the Si prism is antireflection coated with a 208-nm Si3N4 film.     

Nutritive value of marine oils. II. Effects ofin vivo antioxidants in feeding menhaden oil to swine

Five pair-groups of swine were fed diets composed of crude feed materials to which 10% of clay-bleached, light cold-pressed menhaden oil was added. The oil was allowed to oxidize under controlled conditions and aliquots of fresh and oxidized oil were removed at peroxide values (PV) of 2.6, 15.5, and 61—each of which was fed to one group of animals. Two additional animal groups received diets containing the highly oxidized oil (PV=61) plus either alpha-tocopherol acetate or ethoxyquin. All oils were stored frozen and were mixed with the diets daily. Lard was fed at a similar 10% level to a control group of pigs. Both feed intakes and weight gains were progressively reduced as the diet oil was more highly oxidized. As oxidation of the oil increased, intensity of “yellow fat” increased and hemoglobin and hematocrit levels were progressively decreased. Both alpha-tocopherol acetate and ethoxyquin actedin vivo to improve feed intake, rate of gain, and blood condition, and eliminated the incidence of steatitis. Paper I in this series appeared in the Journal of Nutrition79, 323–332 (1963). Carried out under Contract No. 14-17-0001-352, U.S.D.I. Bureau of Commercial Fisheries. Technical Paper 1615, Oregon Agricultural Experiment Station.     

Delamination growth in long composite tubes under external pressure

Delamination growth is a phenomenon known to reduce the integrity of laminated composite structural elements and may lead to premature failures. In the present study, state of the art procedures of delamination growth analysis are overviewed. The energy release rate calculation is formulated for composite delaminated tubular cross sections and specialized to a finite element model for delamination buckling and growth analysis of long laminated composite tubes taking into account initial geometric imperfections, large deformations, contact between delamination faces and material degradation. It is, then, used to study the potential of delamination growth in a hybrid composite tube. Parametric studies are conducted to assess the effects of delamination length, location and geometric imperfection on growth.     

Functionalized multi-walled carbon nanotubes for oil spill cleanup from water

The growing global economy resulted in an incessant increase in transportation and exploitation of oil. Hence, the oil spillage has been considered a serious threat to aquatic and terrestrial ecosystems. Therefore, water purification has been considered a major challenge around the world. There are numerous classical methods available for oil removal from water, but owing to multiple defects and disadvantages, research efforts have focused to find such adsorbents which can improve oil adsorption capability. Traditional adsorbent material typically applied in oil removal includes activated carbon, organoclays, wool, zeolites, etc. These materials suffer from several drawbacks such as low absorption capacity, non-selective absorption, and complicated reusability, whereas nano-adsorbents offer multiple advantages such as having multiple sorption sites, large surface area, short intra-particle diffusion distance, tuneable pore size, and ease of low-temperature modification. Multi-walled carbon nanotubes (MWCNTs) are extensively used adsorbent materials with a strong affinity for the removal of organic pollutants. The functionalization MWCNTs further increase the sorption capacity of adsorbents manifolds to remove organic materials. These nanocomposites are also compatible with green materials and considered environmentally friendly adsorbents. This review paper aims at providing an insight to understand the properties of the MWCNTs and their potential use to adsorb hydrocarbons from water. Moreover, the synthesis methods of those materials, their modification procedures including the functionalization with metal oxide nanoparticles, and applications are also discussed in detail.

Graphic abstract

     

The effect of combined aids on users performance in collaborative virtual environments

Multimedia Tools and Applications - For Collaborative Virtual Environments (CVEs), many interaction techniques have been developed. Depending on the purpose of the collaborative work, techniques of...