Evaluation of Structural,Tensile and Thermal Properties of Banana Fibers

Recognizing the importance of properties of the plant fibers for their use in polymeric composites and nonavailability of data on tensile, thermal, and other properties of banana fibers of Karnataka (India), a study was undertaken with the objective of determining some of these properties. This article presents determination of structural aspects of the fibers by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) techniques; obtaining stress-strain curves and tensile properties by tensile testing; finally, thermal properties by differential scanning calorimetry and thermogravimetric analysis. FTIR spectrum of banana fibers showed aromatic character, while XRD results indicated the fiber to have mainly the cellulose I structure and crystallinity index of 52%. Thermal-degradation details of fiber samples were revealed by thermal studies. Stress-strain curves of banana fibers suggested their brittle nature with moderate values of tensile strength, but low percentage elongation. Weibull analysis of obtained tensile strength values revealed variation of “characteristic strength” values from 3800 MPa at 99% reliability to 22,700 MPa with 0.01% reliability. Morphology studies revealed the number of defects along the length of the fiber, while fractured surface exhibited flat surface with intracellular fractures clearly indicating brittle nature of the fiber.     

Nutrient content,in vitro ruminal fermentation characteristics and methane reduction potential of tropical tannin‐containing leaves

BACKGROUND: Plant tannins as rumen modifiers are better than chemicals or antibiotic‐based modifiers since these compounds are natural products which are environmentally friendly and therefore have a better acceptance with regard to feed safety issues. Tropical plants containing phenols such as tannins were found to suppress or eliminate protozoa from the rumen and reduce methane and ammonia production. The screening of these plants is an important step in the identification of new compounds and feed additives which might contribute to mitigate rumen methanogenesis. The present study was carried out to determine the efficacy of tannins from tropical tree leaves for their methane reduction properties. RESULTS: Activity of tannins, as represented by the increase in gas volume with the addition of polyethylene glycol (PEG)‐6000 as a tannin binder (tannin bioassay) was highest in Ficus bengalensis (555%), followed by Azardirachta indica (78.5%). PEG addition did not alter (P > 0.05) methane percentage in Ficus racemosa, Glyricidia maculata, Leucena leucocephala, Morus alba and Semaroba glauca, confirming that tannins in these samples did not affect methanogenesis. The increase (P < 0.05) in protozoa population with PEG was maximal in Ficus religiosa (50), followed by Moringa oleifera (31.2), Azardirachta indica (29.9) and Semaroba glauca (27.5). There was no change (P > 0.05) in the protozoa population in Autocarpus integrifolia, Ficus bengalensis, Jatropha curcus, Morus alba and Sesbania grandiflora, demonstrating that methane reduction observed in these samples per se was not due to defaunation effect of the tannin. The increase in total volatile fatty acid concentration in samples with PEG ranged from 0.6% to > 70%. The highest increase (%) in NH₃‐N was recorded in Azardirachta indica (67.4), followed by Ficus mysoriensis (35.7) and Semaroba glauca (32.6) leaves, reflecting strong protein binding properties of tannin. CONCLUSION: The results of our study established that in vitro methanogenesis was not essentially related to the density of protozoa population. Tropical tree leaves containing tannins such as Autocarpus integrifolia, Jatropha curcus and Sesbania grandiflora have the potential to suppress methanogenesis. Therefore tannins contained in these plants could be of interest in the development of new additives in ruminant nutrition. Copyright © 2012 Society of Chemical Industry     

Synthesis and characterization of nonlinear optical side-chain polyimides containing the thiadiazole chromophores

Thermally stable second-order nonlinear optical (NLO) polyimides were synthesized using a standard condensation polymerization technique. The polyimides were prepared from 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and pyromellitic dianhydride (PMDA) with two aromatic azo- and diazo-diamine derivatives as the NLO chromophores. The resulting polyimides were characterized by FTIR, ¹H-NMR, UV-vis spectroscopies, differential scanning calorimetry, thermogravimetric analysis, and gel permeation chromatography. The weight-average molecular weights of polyimides determined by gel permeation chromatography (GPC) were in the range of 32,100 to 39,300 (M_w/M_n = 1.58–1.74). All the polyimides exhibited an excellent solubility in many of the aprotic polar organic solvents, manifesting that these polyimides offer good processability. The glass transition temperature for the resulting polyimides was in the range of 152 to 194°C and most of them showed high thermal stability. Particularly, the polyimides containing diazo group and PMDA backbone showed an enhanced thermal stability and glass transition temperature. The second harmonic generation (SHG) coefficients (d₃₃) of the poled polyimide films range from 43.71 to 80.49 pm/V at 532 nm. Further, it is noticed that there was no SHG decay below 180°C because of the partial main-chain character of the polyimide structure, which is acceptable for nonlinear optical device applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Chromia-Assisted Decarburization of W-Rich Ni-Based Alloys in Impure Helium at 1273 K (1000 °C)

The microstructure and surface stability of two experimental W-rich Ni-based alloys have been studied at 1273 K (1000 °C) in an impure-He environment containing only CO and CO₂ as impurities. The alloy Ni-2.3Al-12Cr-12W contained 0.08 wt pct carbon in solution, whereas the second alloy Ni-2.3Al-3Mo-12Cr-12Co-12W contained M₆C carbides at the same carbon level. Both alloys, which were preoxidized with ~2.3 μm Cr₂O₃ layer, were decarburized completely within 50 hours of exposure to the helium gas mixture at 1273 K (1000 °C) via the following chromia-assisted decarburization reaction: Cr₂O₃ (s) + 3C_alloy (s) → 2Cr (s) + 3CO (g). Microstructural observations, bulk carbon analysis, and microprobe measurements confirmed that the carbon in solid solution reacted with the surface chromium oxide resulting in the simultaneous loss of chromia and carbon. The Cr produced by the decomposition of the Cr₂O₃ diffused back into the alloy, whereas CO gas was released and detected by a gas chromatograph. Once the alloy carbon content was reduced to negligible levels, subsequent exposure led to the uninterrupted growth of Cr₂O₃ layer in both alloys. In the preoxidized alloys, chromia-assisted decarburization rates were slower for an alloy containing carbides compared with the alloy with carbon in solid solution only. The formation of Cr₂O₃ is shown to be the rate-limiting step in the chromia-assisted decarburization reaction. Exposure of as-fabricated alloys to the impure-He environment led to the formation of a thin layer of Al₂O₃ (<1 μm) between the substrate and surface Cr₂O₃ oxide that inhibited this decarburization process by acting as a diffusion barrier.     

Phytochemistry, traditional uses and pharmacology of Eugenia jambolana Lam. (black plum): A review

Eugenia jambolana Lam. (syn. Syzigium cumini (L.) SKEELS; S. jambolana DC; Family: Myrtaceae), commonly known as black plum or Jamun is a plant native to India. Annually the trees produce oblong or ellipsoid fruits (berries). They are green when raw and purplish black when fully ripe. The ripe fruits are sweetish sour to taste and are used to prepare health drinks, squashes, juices, jellies and wine. Studies have shown that the berries contain carbohydrates, minerals and the pharmacologically active phytochemicals like flavonoids, terpenes, and anthocyanins. Jamun is a plant with known ethnomedicinal uses. Before the discovery of insulin, Jamun was useful in the treatment of diabetes and is an integral part in the various alternative systems of medicine. Scientific studies have shown that the various extracts of Jamun possess a range of pharmacological properties such as antibacterial, antifungal, antiviral, anti-genotoxic, anti-inflammatory, anti-ulcerogenic, cardioprotective, anti-allergic, anticancer, chemopreventive, radioprotective, free radical scavenging, antioxidant, hepatoprotective, anti-diarrheal, hypoglycemic and antidiabetic effects. The present paper reviews these aspects and also addresses the lacunas in the existing knowledge.     

Aqueous Extraction and Enzymatic Destabilization of Coconut Milk Emulsions

Fresh and mature coconuts were subjected to deshelling, paring and disintegration. The coconut milk was extracted, treated with an enzyme (protease) at different concentrations and centrifuged, in order to separate it into coconut cream and aqueous phases. Subsequently, coconut cream was subjected to chilling (different temperatures) and thawing to ambient temperature (29 ± 2 °C) followed by centrifugation to obtain a clear virgin coconut oil (VCO). Coconut milk treated with aspartic protease at concentration of 0.02 mg/g, resulted in 90.4 ± 1.2% yield. A maximum yield of 95.3 ± 1.0% was obtained when the treatment of coconut milk with aspartic protease at concentration of 0.02 mg/g was followed by chilling (5 °C) and thawing. Physicochemical properties and fatty acid compositions were evaluated and compared with commercial coconut oil samples. It was found that the oil obtained from present study is low with respect to free fatty acids (0.31%) and peroxide value (0.81 mequiv O₂/kg) when compared with the commercial coconut oil samples. Sensory evaluation was also carried out to ensure the product acceptability.     

Carburization of W- and Re-rich Ni-based alloys in impure helium at 1000 °C

The surface and microstructure stability of experimental W- and Re-rich Ni-based alloys in an impure-helium environment containing only CO and CO₂ as impurities (ppm level) have been investigated at 1000 °C. All the alloys carburized during 50 h of exposure, and, depending on the alloy composition, different carbides of the type M₆C, M₇C₃ and M₂₃C₆ formed on the alloy surface, in grain interiors and at grain boundaries. Microprobe analysis and Calphad-based calculations indicated that the chromium carbides (particularly Cr₂₃C₆) were enriched by rhenium. Extended exposure (225 h) led to the disappearance of surface transient carbides and the growth of surface oxide Cr₂O₃ occurred.     

Effect of different treatments for the destabilization of coconut milk emulsion

Coconut milk is an emulsion which is stabilized by naturally occurring proteins. The main objective of the present work is to explore different methods employing thermal, pH, chilling, enzyme treatments and combination of enzyme treatments followed by chilling and thawing for effective destabilization of the coconut milk emulsion. Stability of emulsion is evaluated by measuring the creaming index and observed for the changes in structure of oil droplets, using phase contrast microscope. Combination of treatments (enzyme treatment at 37 °C followed by chilling and thawing) of coconut milk emulsion has resulted in highest yield of 94.5%. Physico-chemical properties and fatty acid compositions are evaluated for coconut oil obtained by combination of treatments and compared with that of commercial coconut oil. It is found that the oil obtained by combination of treatments is low with respect to free fatty acids and peroxide value and high in lauric acid content.     

Response Surface Modeling and Optimization of Gelcast Fused Silica Micro Hybrid Ceramic Composites

Silicon - In the current work, Response Surface Methodology (RSM) was effectively implemented to the technique of fabrication of fused silica (SiO2) advanced hybrid ceramic composites using...     

MHD Williamson nanofluid across a permeable medium past an extended sheet with constant and irregular thickness

The main resource of this paper is to establish over fluid flows sheet using mathematical modeling for constant and variable thickness by including magnetic fields, electric fields, porous medium, heat propagation/immersion, and radiative heat relocation. The Implicit Finite Difference Method (IFDM) is applied to simplify using similarity conversions to implicate partial differential equations to convert into ordinary differential equations. IFDM has been implemented in MATLAB to tabulate numerical observations of the local parameters. Nusselt and Sherwood numbers are analyzed and measured for different parameters in different constant and variable thickness conditions of fluid properties. The influence of various parameters is explained through temperature, velocity, concentration, and nanoparticle volume fraction graphical representations. The coefficient of the skin friction for irregular fluid properties is shown to have a greater influence than that compared for constant fluid properties. Nevertheless, there is a reverse case in the local Nusselt number that is lower for the fluctuating fluid properties than with constant fluid properties. The results showed high-exactness computational outcomes are attained from the IFDM.