Thermal Conductivity of Silicate and Borate Glasses

Thermal conductivities of silicate and borate glasses were determined at 30°C by steady-state methods. From the experimental data, factors representing the contribution of individual oxides (on a weight-percent basis) were calculated by the least-squares method. The experimental thermal conductivities and those calculated from the factors obtained agree fairly well.     

The microstructure of buccal cavity and alimentary canal of Siganus rivulatus: Scanning electron microscope study

The microstructure of the oral cavity and alimentary canal of herbivorous fish Siganus rivulatus collected from the Red Sea were investigated by using scanning electron microscope (SEM). The results showed that S. rivulatus has three types of teeth, tri‐cusped, bi‐cusped, and papilliform. A taste bud (Type I) was recorded in the oropharyngeal cavity. Characteristic styles of microridges on the cell's surface inside the buccal cavity were recorded. Also, the distribution of the mucous cells in the lining of the mouth cavity, alimentary canal was observed. Mucosal folds along the distinct parts of alimentary canal, showed characteristic pattern which was complex in the intestinal mucosa. The results concluded that there are characteristic microstructures according to feeding habitat compared with other bony fishes.     

Volatiles Retention in the Drying of Skin Forming Materials PART 2: Natural Materials

ABSTRACT

The retention of ethanol as a simulated flavour was determined by drying single droplets in a horizontal wind tunnel, with fructose, reconstituted skim milk or coffee as the flavour encapaulant. Droplet temperature histories, ethanol content, and crust structure were evaluated for each encapsulant. No enhancement of volatile retention was obtained with the fructose eolutions irrespective of initial concentration, air velocity, or air temperature. Enhancement of the volatiles retention with the coffee and skim milk solutions correlated with an increase in initial solide concentration. resulting from selective diffusion phenomena and the formation of a resistant skin. In both cases air velocity had no significant effect upon volatiles retention. Skin forming materials with similar characteristics would be advantageous for flavour retention.     

Dielectric properties of new fully conjugated 2H‐ and metal‐pyrazinoporphyrazine network polymers

2,7‐Di‐tert‐butylpyrene was oxidized to 2,7‐di‐tert‐butylpyrene‐4,5,9,10‐tetraone. The latter through condensation reaction with vicinal diamine such as diaminomaleodinitrile afforded heterocyclic monomer, 2,7‐di‐tert‐butyl pyrene[4,5][9,10]bis(2,3‐pyrazine‐5,6‐dinitrile), which was cyclotetramerized to the corresponding 2H‐ and metal‐pyrazinoporphyrazine‐based network polymers (2H‐PyzPz and M‐PyzPz, M = Co, Ni, Zn, or Cu). Elemental analytical results, Infrared, and NMR spectral data of the new prepared molecules are consistent with their assigned formulations. Molecular masses and metal contents of the synthesized polymers proved to be of high molecular masses, which confirm the efficiency of tetramerization polymerization and complexation reactions. Dielectric permittivity, ε′, loss tangent, tan δ, and ac conductivity, σac(ω), of 2H‐PyzPz and M‐PyzPz films were studied as a function of temperature and frequency. It was found that dielectric permittivity, ε′, decreases with the increase of frequency and increases with the increase in temperature. Ac conductivity, σac(ω), is found to vary as Bωs and the frequency exponent, s, is less than unity around room temperature indicating a dominant hopping process. On the other hand, σac(T) of all samples is thermally activated with low activation energies. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Fabrication and modification of polyvinylchloride based heterogeneous cation exchange membranes by simultaneously using Fe-Ni oxide nanoparticles and Ag nanolayer: Physico-chemical and antibacterial characteristics

Polyvinylchloride-blend-styrene butadiene rubber based nanocomposite cation exchange membranes were prepared by solution casting technique. Iron-oxide nanoparticles and Ag-nanolayer were simultaneously utilized as filler and surface modifier in membrane fabrication. The effects of Ag-nanolayer film thickness on membrane physicochemical and antibacterial characteristics of nanocomposite PVC-blend-SBR/Iron-oxide nanoparticles were studied. SEM images showed membrane roughness decreasing by Ag nanolayer thickness increasing. Membrane charge density and selectivity declined by Ag nanolayer coating up to 5 nm in membranes and then showed increasing trend by more nanolayer thickness. Ionic flux also showed increasing trend. Membranes showed good ability in E-Coli removal. 20 nm Ag-nanolayer coated membrane showed better performance compared to others.     

A Leakage-Based Precoding Scheme for Downlink Multi-User MIMO Channels

In multiuser MIMO downlink communications, it is necessary to design precoding schemes that are able to suppress co-channel interference. This paper proposes designing precoders by maximizing the so-called signal-to-leakage-and-noise ratio (SLNR) for all users simultaneously. The presentation considers communications with both single- and multi-stream cases, as well as MIMO systems that employ Alamouti coding. The effect of channel estimation errors on system performance is also studied. Compared with zero-forcing solutions, the proposed method does not impose a condition on the relation between the number of transmit and receive antennas, and it also avoids noise enhancement. Simulations illustrate the performance of the scheme     

Electrochemical bleaching of kraft bagasse pulp using a new cell design

In situ single‐stage electrochemical bleaching of kraft bagasse pulp was carried out in a cylindrical agitated vessel fitted with four graphite rod anodes and a cylindrical stainless steel screen cathode, using NaCl as an electrolyte. The effect of current density, pH, NaCl concentration, impeller rotational speed, temperature, and pulp consistency on the rate of bleaching was studied. It was found that the rate of bleaching increased with increasing current density, NaCl concentration, and temperature and decreased with increasing pH and pulp consistency. The effect of temperature was found to fit Arrhenius equation with an activation energy of 0.515 kcal/mol, which denotes a diffusion‐controlled mechanism. Energy consumption (EC) calculation showed that EC ranged from 0.225 to 3.11 kWh/kg dry pulp depending on the current density. The strength of bleached pulp was little affected by bleaching lying within an acceptable range.     

AC susceptibility and hyperfine interactions of vanadium substituted barium nanohexaferrites

Vanadium ions substituted BaFe₁₂O₁₉ nanohexaferrites, BaFe_12-xV_xO₁₉ (0.0?≤x?≤?0.1), were produced through the sol-gel auto-combustion route. The structure, morphology and the elemental compositions of various products were examined using X–ray powder diffraction, scanning electron microscopy coupled with EDX and EDS elemental mapping. These techniques confirmed the formation of the desired Ba-nanohexaferrite phases. The crystallites size was found to be 55–58?nm range for all products. The magnetic properties of BaFe_12-xV_xO₁₉ nanohexaferrites were investigated by Mossbauer spectroscopy, ZFC-FC magnetizations and AC susceptibility. The evolutions in the values of hyperfine magnetic field, isomer shift, quadrupole splitting, and line width were deduced via Mossbauer analysis. The experiments of ZFC and FC magnetizations indicated that no blocking temperature is observed in the temperature interval 2–400?K, which signals the typical ferromagnetic (FM) behavior for the produced nanohexaferrites. A super-spin glass like behavior is noticed at lower temperatures. The experiments AC susceptibility confirmed that the strength of magnetic interactions is enhanced for lower content of V³⁺ (x?=?0.02). For higher amount of V³⁺, the magnetic interactions are weakened. The obtained results are mainly accredited to the substitutions of Fe³⁺ ions by V³⁺ ions.     

Synthesis of novel dyestuffs containing sulphonamido moieties and their application on wool and polyamide fibres

A new series of azo disperse dyestuffs were prepared by the reaction of sulphanilamidodiazonium chloride derivatives with indan-1,3-dione. Application of these dyes on wool and nylon 6.6 gave excellent results. The synthesised compounds show good biological activity towards different microorganisms.