Investigation of Entry Region Turbulent Flows of Non-Gray Gases

The entrance region turbulent flow between parallel planes has been investigated numerically. Variation of fluid properties with temperature has been considered. Monte Carlo simulation has been used with a narrow band non-gray model to investigate radiative transfer. The effects of radiative transfer and variable properties have been separately and systematically considered. Representative results are included for carbon monoxide and carbon dioxide. For the conditions considered, the results show that the variable properties exert a stronger influence compared to radiative transfer alone.     

Solid-state fermentation of new substrates for production of cellulase and other biopolymer-hydrolyzing enzymes

Applied Biochemistry and Biotechnology -     

Quasicrystalline and related phases in titanium based alloy systems

Amongst the non-aluminium based quasicrystalline alloys, investigations of titanium containing alloys in regard to the occurrence and stability of quasicrystalline phases have aroused considerable interest in recent years. Employing X-ray and TEM techniques a systematic investigation of the influence of substitution for Fe by Si and Ni on the stability of icosahedral phase in rapidly quenched Fe-Ti alloy has been carried out. The occurrence of metastable phases including commensurately modulated phase and the decagonal phase in Fe-Ti-Si system have been found. In addition, the occurrence ofstructural disorder manifested by arcs of diffuse scattering in diffraction patterns and anisotropy in the shape of idffraction spots has also been pointed out. It has been observed that 6 at.% of Si in Fe-Ti-Si system results in the formation of single-phase icosahedral quasicrystals. We have shown that contrary to some earlier reported results on Ti₂Ni, Ti₂Ni(Si) and Ti₅₆Ni₂₃Fe₅Si₁₆ alloys do not possess the icosahedral phase. In Ti₆₈Fe_26−xNi_xSi₆ alloy system, icosahedral phase formation ability is limited to the value of x < 9. The occurrence of icosahedral phase in these alloy systems has been analysed in terms of e/a ratio.     

Electrical conductivity and structural behaviour of Al65Cu20Ru15 quasicrystalline alloy

The low temperature conductivity σ (T) and the magnetoresistance (up to 8 T) of a phason disorder free pure Al₆₅Cu₂₀Ru₁₅ quasicrystalline alloy, prepared by melt casting, has been investigated in the temperature range from 1.3 K to 200 K. In the temperature range 1.3 to 20 K the conductivity exhibits a -variation, whereas for the range 20 to 200 K a linearT-dependence has been observed. The analysis of magnetoresistance data reveals the presence of weak localization and electron-electron interaction effects. The positive nature of the magnetoresistance indicates the presence of spin orbit scattering. The σ∞ behaviour prevailing over such a wide temperature range has been observed for the first time for Al₆₅Cu₂₀Ru₁₅. A quantitative analysis of the -variation in terms of electron-electron interaction yields a very low density of states at the Fermi level.     

Stereoselective synthesis of 3-alkylidene/alkylazetidin-2-ones from azetidin-2,3-diones

Azetidin-2,3-diones have been used as synthons for the synthesis of C-3 alkylidene/alkylazetidin-2-ones. Some of the 3-alkylazetidin-2-ones are well known for their cholesterol absorption inhibitor activity. A regio and stereoselective Grignard reaction on a keto group followed by dehydration using PPh₃/CCl₄ reagent is a key step in this synthesis. Hydrogenation of the 3-alkylideneazetidin-2-ones provided stereoselectively cis-3-alkylazetidin-2-ones in very good yields.     

1-Methylimidazolium chlorochromate: A new Cr(VI) oxidant and use of anhydrous acetic acid as the catalyst for the oxidation of primary and secondary alcohols

The synthetic potential of a new Cr(VI) reagent, viz., 1-methylimidazolium chlorochromate, analogous to Corey's reagent-PCC, has been examined. Anhydrous acetic acid has been found to catalyze the oxidation reaction.     

Polyacrylate/silica hybrid materials: A step towards multifunctional properties

Organic/Inorganic hybrid systems present a promising alternative for the creation of high-performance materials due to their biphasic structure that imparts multifunctional properties. The sol-gel process which initiated with the synthesis of inorganic glasses has now become a synthetic route for organic-inorganic assemblies due to several advantages such as mild processing conditions and the freedom to play with the structures of precursors. This versatility of the low-temperature sol-gel process provides an opportunity to engineer both the phases resulting in a synergistic combination or entirely new set of properties fruitful for different applications. This review highlights the several pathways for synthesis of silica particles, the interfacial modification and the classification of hybrid materials based on the method of incorporation of an inorganic moiety in the organic matrix along with the structure-property relationship, and the characterization to develop a fundamental understanding of the process. The nature of bonding between the two different species greatly affects the hybrid nanostructure and thus, the bulk properties of the system. In particular, acrylate/silica system has been focused due to its distinctive properties such as transparency, gloss, and strength that find large-scale application in the field of coatings, plastics and rubbers.Abbreviations: °: Degree; °C: Degree Celsius; ¹H NMR: Proton nuclear magnetic resonance; A°: Angstrom; AHAS: N-(3-acryloxy-2-hydroxyl propyl)-3-amino-propyltriethoxysilane; AIBA: 2,2′-Azobis(2-methylpropionamidine) dihydrochloride; AIBN: 2,2′-Azobis(2-methylpropionitrile); Al: Aluminium; APDMES: Aminopropyldimethylethoxysilane; APTES: 3-Aminopropyltriethoxysilane; ATRP: Atom transfer radical polymerization; CERAMERS: Ceramically Modified Monomers; CTAB: Cetyltrimethylammonium bromide; DFMA: Dodecafluoroheptyl methacrylate; DMF: Dimethylformamide; DPSD: Diphenylsilanediol; FESEM: Field Emission Scanning Electron Microscope; FTIR: Fourier-transform infrared spectroscopy; GPTMS: 3-Glycidoxypropyltrimethoxysilane; HDTMS: Hexadecyltrimethoxysilane; HEMA: 2-Hydroxyethyl methacrylate; HLB: Hydrophilic-Lyophilic Balance; HMDS: Hexamethyldisilazane; HPC: Hydroxypropyl Cellulose; IPN: Interpenetrating Network; KPS: Potassium persulfate; LCST: Lower critical solution temperature; McPTMS: 3-Mercaptopropyltrimethoxysilane; MOI: 2-(methacryloyloxy)ethyl isocyanate; MPEGMA: Monomethoxy-capped poly(ethylene glycol) methacrylate; MPTMS: 3-methacryloxypropyltrimethoxysilane; MTC: 2-(methacryloyl) ethyltrimethylammonium chloride; MTES: Methyltriethoxysilane; MTMS: Methyltrimethoxysilane; NMP: Nitroxide-Mediated Polymerization; ORMOCERs: Organically Modified Ceramics; ORMOSILs: Organically Modified Silica; OTES: Octyltriethoxysilane; OTMS: Octadecyltrimethoxysilane; PAA: Poly(acrylic acid); PDMS: Polydimethylsiloxane; PEO-PPO-PEO: Poly (ethylene oxides)-b-poly (propylene oxides)-b-poly (ethylene oxides); PHPS: Perhydropolysilazane; PMMA: Poly(methyl methacrylate); POSS: Polyhedral Oligomeric Silsesquioxane; PTMO: Poly(tetramethylene oxide); PTMS: Phenyltrimethoxysilane; PTMS: Phenyltrimethoxysilane; PVP: Poly (vinylpyrrolidone); RAFT: Reversible addition- fragmentation chain transfer; Si: Silicon; Sn: Tin; Ta: Tantalum; TBN: 4-(triethoxysilyl)butyronitrile; TEM: Transmission Electron Microscopy; TEMED: N,N,N′,N′-tetramethylethylenediamine; TEOS: Tetraethoxysilane; Tg: Glass-Transition Temperature; THF: Tetrahydrofuran; Ti: Titanium; TMOS: Tetramethoxysilane; UV: Ultraviolet; VTES: Vinyltriethoxysilane; VTMS: Vinyltrimethoxysilane; Zr: Zirconium

• Highlights

• Advantages of hybrid systems over the conventional materials

• Discusses the fundamental aspects of sol-gel chemistry

• Focusses on a detailed classification of hybrid polymers

• Covers different synthetic strategies, properties, and applications in diverse fields

     

Spectrophotometric determination of Fe(III) with tiron in the presence of cationic surfactant and its application for the determination of iron in Al-alloys and Cu-based alloys

A sensitive Spectrophotometric method for the determination of iron with tiron and a cationic surfactant, cetylpyridinium chloride, at pH 5.6 is reported. The complex is extracted into a chloroform-propan-2-ol (41) mixture and shows maximum absorbance at 520 nm. Beer's law is obeyed in the range 1–14 g/ml with an average molar absorptivity of 15800 l mol^–1 cm^–1. The molar ratio as determined by Job's method for Fe:tiron:CPC is 143. Interferences by various ions are examined. Zr, Ti and Mo interfere heavily. The method is applied for the determination of iron in Al-based and Cu-based alloys, using appropriate masking agents.