A new design for the pin and V-blocks tribometer

A compact and vacuum compatible design for the generally used pin and V-blocks tribometer is presented. The device has two built-in transducers for measurement of the applied load and friction torque, from which the coefficient of friction is determined. The design, construction and calibration of the transducers are described in detail. The use of the test rig is illustrated by tribotests in air and in high vacuum environments for the study of the tribological behaviour of a bonded solid lubricant film on various substrate materials.     

Microstructural changes in a mechanically alloyed Al-6.2Zn-2.5Mg-1.7Cu alloy (7010) with and without particulate SiC reinforcement

Elemental powders of Al, Zn, Mg, and Cu (corresponding to the composition of 7010 aluminium alloy) were milled in a high-energy attritor with and without additions of SiC particulates. The microstructural changes taking place in the milled powders (which eventually lead to mechanical alloying) are found to be retarded by SiC additions. High-resolution techniques such as electron probe microanalysis (EPMA) and transmission electron microscopy/energy-dispersive X-ray analysis (TEM/EDX) revealed the presence of localized solute-rich regions long after the diffraction line from these solutes had ceased to appear in the X-ray diffractograms. Zinc appears to be more difficult to be mechanically alloyed into aluminum than either Cu or Mg in spite of its comparatively larger diffusivity in aluminum.     

Baker's yeast expressing the Japanese encephalitis virus envelope protein on its cell surface: induction of an antigen‐specific but non‐neutralizing antibody response

Live recombinant Saccharomyces cerevisiae yeast expressing the envelope antigen of Japanese encephalitis virus (JEV) on the outer mannoprotein layer of the cell wall were examined for their ability to induce antigen‐specific antibody responses in mice. When used as a model antigen, parenteral immunization of mice with surface‐expressing GFP yeast induced a strong anti‐GFP antibody response in the absence of adjuvants. This antigen delivery approach was then used for a more stringent system, such as the envelope protein of JEV, which is a neurotropic virus requiring neutralizing antibodies for protection. Although 70% of cells were detected to express the total envelope protein on the surface by antibodies raised to the bacterially expressed protein, polyclonal anti‐JEV antibodies failed to react with them. In marked contrast, yeast expressing the envelope fragments 238–398, 373–399 and 373–500 in front of a Gly–Ser linker were detected by anti‐JEV antibodies as well as a monoclonal antibody but not by antibodies raised to the bacterially expressed protein. Immunization of mice with these surface‐expressing recombinants resulted in a strong antibody response. However, the antibodies failed to neutralize the virus, although the fragments were selected based on neutralizing determinants. Copyright © 2009 John Wiley & Sons, Ltd.     

Structure and physical properties of grafted jute fiber

Jute fiber was grafted by acrylonitrile and methylmethacrylate monomers in raw and bleached condition. It was also noted that optimum grafting takes place after about 4 h of grafting. It was also noted that in bleached jute fiber, the grafting percentage is higher at all stages of grafting but the tenacity value at the highest add-on is practically the same as that of raw fiber with much less add-on. The crystalline orientation of the grafted jute fiber was correlated with the fiber tenacity. The moisture regain (%) of the fiber after grafting showed a decreasing trend with an increase in grafting percentage. No structural change of the fiber occurred due to grafting. © 1995 John Wiley & Sons, Inc.     

Aromatic polyesters (polyarylates) containing arylene sulfone ether linkages

A series of soluble aromatic polyesters (polyarylates) containing arylene sulfone ether linkages and having inherent viscosities of 0.36–1.10 dl/g were prepared by the two-phase low temperature polycondensation of 4,4′-[sulfonyl-bis(p-phenyleneoxy)]dibenzoyl chloride and 3,3′-[sulfonylbis(p-phenyleneoxy)]-dibenzoyl chloride with various bisphenols in an organic solvent-aqueous alkaline solution system in the presence of a phase transfer catalyst. Bisphenols 4,4′-[sulfonylbis(p-phenyleneoxy)]diphenol and 3,3′-[sulfonylbis(p-phenyleneoxy)]-diphenol were synthesized in quantitative yields by an improved procedure. The aromatic polyesters prepared were characterized by infrared spectroscopy, elemental analysis, solution viscosity, thermogravimetric analysis, differential scanning calorimetry and X-ray diffraction. The polyesters prepared had glass transition temperatures in the range 150–230°C and initial decomposition temperatures of 397–491°C. They gave transparent, tough and flexible films by the solution casting technique.     

Studies on Dehydration of Sapota (Achras zapota)

Sapota (Achras zapota) is a tropical fruit found in several parts of India. It is one of the most popular fruits besides mango, custard apple, and several others. Once ripe, it needs to be consumed within a couple of days due to the highly perishable nature of this exquisite fruit variety. The best way to increase the shelf-life is through the process of dehydration of peeled sapota. In the present study, the convective air drying of sapota pulp was carried out and compared with low-temperature drying techniques such as heat pump-assisted drying and freeze drying. The sapota paste was dried in a convective dryer to study the effect of operating parameters such as air temperature and air velocity. In addition, the effect of additives such as oat and wheat fibers and the paste thickness on drying was also studied. The critical analysis of dehydrated sapota was carried out in terms of water activity, sugar content, color, and rehydration ratio. The drying data were analyzed using Page's model and Newton's model on the basis of root mean square error (RMSE), reduced χ square (χ²) and correlation coefficient (R²).     

Single op-amp sinusoidal oscillators suitable for generation ofvery low frequencies

The authors present some op-amp-based single-element controlled sinusoidal oscillator structures which can generate very low frequencies (VLF). In contrast to earlier VLF oscillators which have large frequency of the oscillations sensitivities and/or require two to five op-amps, the proposed circuits make it possible to generate VLF oscillations in a minimally sensitive manner while requiring only a single op-amp. The experimental results prove the validity of the theoretical formulations     

A modified rule-of-mixtures for prediction of tensile strengths of unidirectional fibre-reinforced composite materials

Measured ultimate tensile strengths in unidirectional fibre-reinforced composite materials have been observed to deviate from the linear predictions of the classical rule-of-mixtures relationship. The physical factors responsible are fibre-fibre interaction, inhomogeneous fibre distribution in the matrix and fibre misorientation to the loading direction. A recent modification to the classic rule-of-mixtures to account for fibre-fibre interaction has already resulted in good agreement between measured and predicted values of ultimate tensile strengths at high fibre volume fractions for Kevlar/epoxy composites. Additional modifications to the rule of mixtures to incorporate both fibre misorientation and inhomogeneous spread have been presented here. These modifications result in greater agreement between measured and predicted ultimate tensile strengths at low fibre volume fractions while retaining the accuracy of prediction at higher fibre volume fractions. Good agreement between measured and predicted values of inhomogeneous fibre spread were obtained at high fibre volume fractions. Furthermore, these additions to the classic rule-of-mixtures can be used to gauge the extent of each of the physical factors responsible for ultimate tensile strength reduction in unidirectional composite materials.     

New voltage controlled oscillators using CFOAs

In this paper, some new current feedback operational amplifier (CFOA)-based voltage-controlled oscillators (VCOs) have been introduced. The proposed circuits offer a number of advantageous features over previously known CFOA-based VCOs. The workability of the presented circuits has been demonstrated using AD844 CFOAs and BFW10 FETs.