Phase Relations and Stability Studies in the Si3N4-SiO2-Y2O3 Pseudoternary System

Composite powders were hot-pressed to determine the phase relations in the Si₃N₄-SiO₂-Y₂O₃ pseudoternary system. Four quaternary compounds, Si₃Y₂O₃N₄, YSiO₂N, Y₁₀Si₇O₂₃N₄, and Y₄Si₂O₇N₂, were identified. Studies of polyphase and single-phase materials in this system showed that these 4 compounds are unstable under oxidizing conditions. Materials within the Si₃N₄-Si₂N₂O-Y₂Si₂O₇ compatibility triangle precluded the unstable compounds, and are extremely resistant to oxidation.     

Enhancement of the conjugated linoleic acid and vitamin A and E contents in goat milk through green fodder feeding

Twelve lactating crossbred goats (Sanan × Beetal) in early lactation were divided into two groups of six each. Group I was fed on fresh berseem fodder ( Trifolium alexandrinum ), whereas group II was fed on berseem fodder and concentrate mixture in 1 : 1 ratio to fulfil their nutritional requirements as per National Research Council (1981 ). Feed intake and milk yield were recorded daily, and milk samples were collected on 0, 30, 45 and 60 days of experimental feeding for the estimation of fat, vaccenic acid, conjugated linoleic acid (CLA), vitamins A and E, and total antioxidant activity. There was no effect ( P >  0.05) of dietary treatments on daily as well as total milk yield and milk fat, solids-not-fat and total solids, although average total CLA (mg/g fat) content in milk during the trial was higher( P <  0.01) in group I (18.92) in comparison to group II (10.94). Vitamin A content averaged 0.46 and 0.27 µg/mL and vitamin E, 1.20 and 1.38 µg/mL in milk of groups I and II, respectively, were higher in the berseem-fed group ( P <  0.01) and total antioxidant activity of milk was also higher ( P <  0.01) in group I than in group II.     

Chitosan-encapsulated ZnS : M (M: Fe<Superscript>3+</Superscript> or Mn<Superscript>2+</Superscript>) quantum dots for fluorescent labelling of sulphate-reducing bacteria

Chitosan-encapsulated Mn²⁺ and Fe³⁺-doped ZnS colloidal quantum dots (QDs) were synthesized using chemical precipitation method. Though there are many reports on bio-imaging applications of ZnS QDs, the present study focussed on the new type of microbial-induced corrosive bacteria known as sulphate-reducing bacteria, Thiobacillus novellus. Sulphate-reducing bacteria can obtain energy by oxidizing organic compounds while reducing sulphates to hydrogen sulphide. This can create a problem in engineering industries. When metals are exposed to sulphate containing water, water and metal interacts and creates a layer of molecular hydrogen on the metal surface. Sulphate-reducing bacteria then oxidize the hydrogen while creating hydrogen sulphide, which contributes to corrosion for instance, in pipelines of oil and gas industries. In this study, detection and labelling of sulphate-reducing bacteria is demonstrated using fluorescent QDs. Chitosan capped ZnS QDs were synthesized using dopants at different doping concentrations. UV–Vis spectroscopy, XRD and FTIR characterizations were done to identify the optical band gap energy, crystal planes and determine the presence of capping agent, respectively. The morphology and the average particle size of 3.5 ± 0.2 nm were analysed using TEM which substantiated UV–Vis and XRD results. Photoluminescence spectroscopy detected the bacteria attachment to the QDs by showing significant blue shift in bacteria conjugated ZnS QDs. Fluorescence microscopy confirmed the fluorescent labelling of QDs to Thiobacillus novellus bacteria cells making them ideal for bio-labelling applications.     

Spin canting phenomenon in cadmium doped cobalt ferrites, CoCd x Fe2−x O 4 ( x = 0·0, 0·2, 0·4, 0·6, 0·8 and 1·0), synthesized using sol–gel auto combustion method

Synthesis of non-collinear (spin canted) ferrites having the formula, CoCd _x Fe_2???x O ₄ (x?= 0·0, 0·2, 0·4, 0·6, 0·8 and 1·0), has been carried out using the sol–gel auto combustion method. The ferrite samples show an interesting magnetic transition from Neel to Yafet–Kittel configuration, as the Cd^2?+? concentration is increased beyond x?= 0·4. The FT–IR spectra confirm the formation of the metal oxide bond as they exhibit two frequency bands in the range of ~595 cm^???1 and ~450 cm^???1, corresponding to the tetrahedral and the octahedral stretching vibrations of the metal oxide, respectively. The structural evolutions of the nanophase investigated using powder X-ray diffraction (XRD) technique show that the average crystallite size is ~ 35 nm. The magnetic studies reveal that the saturation magnetization, M _s , increases up to x?= 0·4 and decreases when the value of x is >0·4. It is proposed that the incorporation of Cd^2?+? ion takes place into the tetrahedral sites and up to x?= 0·4, Neel’s model is followed. But for x?> 0·4, canting of spins occurs, as explained by Yafet–Kittel (Y–K) model. The d.c. resistivity decreases as a function of temperature, indicating semiconducting nature of the ferrites and the positive value of Seebeck coefficient establishes p-type conduction behaviour for all the ferrite samples.     

NUMERICAL METHOD AND RANDOM ANALYSIS OF CEMENT CONCRETE EXPANSION

The numerical method and random analysis of cement concrete expansion are given.A mathematical procedure is presented which includes the nonlinear charac teristics of the concrete.An expression is presented to predict the linear restrained expansion of expansive concrete bar restrained by a steel rod.The results indicate a rapid change in strains and stresses within initial days, after which the change gradually decreases.A reliable and accurate method of predicting the behavior of the concrete bulkheads in drifts is presented here.Extensive sensitivity and parametric studies have been performed. The random density distributions of expansive concrete are given based on the restricted or unrestricted condition. These studies show that the bulkhead stress fields are largely influenced by the early modulus of the concrete and the randomness of the ultimate unrestrained expansion of the concrete.