Immobilization of β-galactosidase onto polymeric supports

Poly(vinyl alcohol) cross-linked with para-formaldehyde (PVA–F) and natural polysaccharide–chitosan in bead form and salicylic acid–resorcinol–formaldehyde polymeric resin (SRF) in powder form were used for immobilization of β-galactosidase through covalent linkages. Various activation processes and conditions were optimized. Immobilized enzyme showed very good storage stability at room temperature. Durability of the enzyme was also improved on immobilization. On repeated use of enzyme immobilized on chitosan beads, no loss was observed in enzyme activity even after 10 batches. Michaelis constant K_m and maximum reaction velocity V_m were calculated for free and immobilized enzyme systems. Effect of pH and temperature on enzyme activity was estimated and energy of activation (E_a) and inactivation constant (K_i) for free and immobilized enzyme were calculated. © 1995 John Wiley & Sons, Inc.     

Estimation of fuzzy memberships from histograms

Based on the conclusions drawn in the bijective transformation between possibility and probability, a method is proposed to estimate the fuzzy membership function for pattern recognition purposes. A rational function approximation to the probability density function is obtained from the histogram of a finite (and sometimes very small) number of samples. This function is normalized such that the highest ordinate is one. The parameters representing the rational function are used for classifying the pattern samples based on a max-min decision rule. The method is illustrated with examples.     

Anomaly of arch of atlas--a rare cause of symptomatic canal stenosis in children

Symptomatic canal stenosis at the level of atlas (C1) without atlantoaxial dislocation is thought to be very rare in children. Though common, anomalies of the arch of atlas are generally incidental findings in X-rays. High cord compression due to a narrow canal from a bifid posterior arch, or an absent posterior arch, is a very rare condition. We report 5 children with high cord compression from stenosis of C1 arch.     

Dielectric properties of K2Zn2(SO4)3 and (NH4)2 Mg2(SO4)3

Dielectric constant (ɛ), dielectric loss (tan δ) and conductivity (σ) for K₂Zn₂(SO₄)₃ and (NH₄)₂ Mg₂(SO₄)₃ have been measured over the frequency range 100 Hz — 100 kHz and in temperature range 30°C — 400°C. The values of static dielectric constant at room temperature are 7.67 and 4.80 for K₂Zn₂(SO₄)₃ and (NH₄)₂ Mg₂(SO₄)₃ respectively. The plots of log σ against reciprocal temperature at different frequencies of these samples merge into a straight line beyond 250°C and the activation energies calculated in this region are found to be 0.67 eV and 1.98 eV for K₂Zn₂(SO₄)₃ and (NH₄)₂ Mg₂(SO₄)₃ respectively.     

The pressure-volume relation of ytterbium up to 9 GPa

The pressure-volume relation of ytterbium has been determined up to 9 Gpa using tungsten carbide opposed anvil high pressure x-ray camera. The fcc phase of ytterbium is observed between one atmosphere and 4 GPa and the bcc phase above 3·5 GPa. The bcc phase can be metastably retained down to 1 GPa by gradually decreasing the pressure from a region where only bcc phase alone is observed. The bulk modulus,B ₀, at zero pressure and the pressure derivative of the bulk modulus,B’ ₀, are determined by fitting Murnaghan equation to the pressure-volume data. The following values were obtained:B ₀=16·3 GPa andB’ ₀=3·6 for the fcc phase, andB ₀=14·7 GPa andB’ ₀=1·5 for the bcc phase. Based on the present data it is suggested that the thermodynamic equilibrium pressure for fcc ⇆ bcc transformation in ytterbium is below 3·5 GPa. The valence change under pressure has been discussed.     

Characteristics and composition of indian wood apple seed and oil

Indian wood apple seed (Feronia elephantum Correa) constituting 6% (dry weight basis) of the fruit, contains 34% oil and 28% protein. The kernel comprises 62% of the seed. The oil is yellow with an iodine value 131, saponification value 192, unsaponifiable matter 1%. Fatty acid profile of oil by GLC is: palmitic 19.3, stearic 7.3, oleic 27.2, linoleic 19.8 and linolenic 26.4%.     

Biopreservative technologies of food: an alternative to chemical preservation and recent developments

Food Science and Biotechnology - Despite centuries of developing strategies to prevent food-associated illnesses, food safety remains a significant concern, even with multiple technological...     

Water absorption behavior of PALF/GF hybrid polyester composites

The water absorption characteristics of pineapple leaf fiber (PALF)/glass fiber (GF) hybrid polyester(PER) composites, and chemically modified PALF/polyester composites were evaluated by immersion in distilled water at 28, 60, and 90°C. The diffusion properties of the intimately mixed (IM) and the layered hybrid composite GPG (Glass skin and PALF core) of different PALF/GF ratio at the three temperatures were compared in order to identify the environmental ageing mechanism at different temperatures. The effect of temperature on the kinetics and thermodynamics of diffusion were also examined. The water uptake of both IM and GPG hybrid composites was decreased with increase in glass fiber content; the lowest water uptake was observed for 0.46 V_f GF hybrid composite. Among the chemically modified composites, vinyl tri 2‐methoxy ethoxy silane treated composites showed the lowest water uptake. Finally, parameters like diffusion, sorption, and permeability coefficients were determined. It was observed that equilibrium water uptake is dependent on the nature of the composite and temperature. Experimental results were also compared with theoretical predictions. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers