Accurate determination of the voltage of a transmission electron microscope (TEM) by 〈0 1 2〉 CBED-HOLZ analyses using GaAs crystal

Convergent beam electron diffraction (CBED) is a powerful technique to estimate lattice distortion and lattice strain in crystals. The positions of the higher-order Laue-zone (HOLZ) lines in the transmitted disc of CBED patterns are very sensitive to the lattice parameter, and can therefore be used to estimate changes in the lattice parameter. This offers the possibility to calculate lattice misfit and lattice strain. The positions of the HOLZ lines depend not only on the lattice parameter, but also on the operating voltage of the microscope. It is essential to know the actual voltage of the microscope. In the present work, (1 0 0) GaAs crystal has been used as a standard. Cross-sectional TEM specimens were prepared by argon ion beam thinning technique using a liquid nitrogen cold stage. 〈0 1 2〉 on-zone CBED technique has been used to estimate the actual voltage of the transmission electron microscope (Philips EM430T TEM), when the voltage was set at 250 kV. CBED-HOLZ simulation and analyses have been done, using JEMS software, to correlate with the experimental data. The methodologies adopted for estimating the actual voltage of TEM are discussed in this paper. The studies have also been cross-checked using 〈0 1 2〉 and 〈2 3 3〉 zone axes using (1 0 0) silicon standard. The techniques established are found to be suitable for TEMs operating at a setting voltage of about 250 kV. For the TEM studies, a regular double-tilt specimen holder is required in order to be able to get to the desired zone axes. When the experiments were repeated using a cryogenic double-tilt holder, an improvement in the sharpness of HOLZ lines was observed. Wherever possible, the use of the cryogenic double-tilt holder is recommended. Care must, however, be taken to ensure that effects such as lattice parameter changes (due to temperature changes), phase transformations etc can be properly accounted for.     

Solvent Transport Characteristics of Thermoplastic Elastomer Blends Based on Nylon and NBR

Transport characteristics of chlorinated hydrocarbon through Nylon/NBR (Acrylonitrile Butadiene Rubber) blend has been investigated with special reference to the effect of blend ratio, compatibilizer and effect of dynamic crosslinking. An attempt has been made to correlate the diffusion characteristics with morphology of the blend. Fine and uniform distribution of the dispersed domains with a stable morphology were obtained by dynamic vulcanization. Depending on the composition, blends show dispersed/matrix and co‐continuous phase morphologies. The various transport parameters such as diffusion coefficient (D), permeation coefficient (P) and sorption coefficients (S) were evaluated at different diffusion conditions such as temperature and percentage of compatibilizer. The equilibrium solvent uptake decreases with an increase in the concentration of NBR in the blends. Finally thermodynamic parameters were evaluated from the diffusion data. POLYM. ENG. SCI., 57:231–236, 2017. © 2016 Society of Plastics Engineers     

How consistent is the satellite derived SST–LHF relationship in comparison with observed values?

Time series data for sea surface temperature (moored buoy), wind speed, air temperature, sea level pressure, relative humidity, short wave radiation and rainfall were collected close to the Lakshadweep islands for five months from July 2000 to cover two seasons, namely summer monsoon and autumn. Day and night passes of TMI data for the same period were analysed to compare with the observed values. Daily mean values were then generated from both satellite‐derived as well as observed parameters and daily latent heat flux (LHF) values computed using the advanced COARE‐3.0 version of the model. In concurrence with earlier studies, the observed LHF–SST relationship was inverse as the SST during this season seldom fell below 27°C. On the contrary, the satellite derived LHF–SST relationship exhibited a direct correlation. It is also observed that the satellite underestimation of SST increases linearly on either side of a threshold value of 28.5°C. Although the SST over the eastern Arabian Sea was generally above 27°C, the satellite underestimation often produced SSTs less than 27°C, thereby supporting a linear relationship with LHF, as suggested by Zhang and McPhaden. Similarly for SSTs higher than 28°C, the satellite underestimation prevented a further decrease of LHF (to sustain the linear relationship) by virtue of the inverse relationship for SSTs higher than 28°C. The overestimation of SST and wind speed in the satellite scenario generates a virtual enhancement of LHF values without cooling the sea surface. The linear relationship between SST and LHF is thus nothing but a virtual display of the observed inverse SST–LHF relationship.     

Dehydration and Crystallization Kinetics of Zirconia-Yttria Gels

Zirconia and zirconia-yttria gels containing 4 and 8 mol % yttria were obtained by coprecipitation and drying at 373 K. The dehydration and crystallization behavior of the dried gels was studied by DSC, TG, and XRD. The gels undergo elimination of water over a wide temperature range of 373–673 K. The peak temperature of the endotherm corresponding to dehydration and the kinetic constants for the process were not influenced by the yttria content of the gel. The enthalpy of dehydration observed was in good agreement with the heat of vaporization data. The dehydration was followed by a sharp exothermic crystallization process. The peak temperature of the exotherm and the activation energy of the process increased with an increase in yttria content, while the enthalpy of crystallization showed a decrease. The "glow effect" reduced with increasing yttria content. Pure zirconia crystallizes in the tetragonal form while the zirconia containing 4 and 8 mol% yttria appears to crystallize in the cubic form.     

Measurements of the equilibrium factor for 222Rn daughters in dwellings in India

As part of an ongoing project to assess the population dose from indoor radon and its daughters in India, a set of parallel measurements was made in more than 150 houses of different types to estimate indoor radon and progeny levels. Time-integrated solid state nuclear track detectors were employed for the measurement of radon concentration and potential alpha energy exposure level. From these values the equilibrium factor (F) between radon and its progeny was estimated for each house. An average F value of 0.39 was obtained.     

Microbiologically influenced corrosion of AISI type 304 stainless steels under fresh water biofilms

The influence of biofilms formed by microorganisms on the corrosion behaviour of stainless steel (SS) in various fresh water environments was studied using electrochemical techniques. Biofilm characterization studies showed an algal‐dominated biofilm in the normal dark and light exposures, whereas, in the continuous dark exposures, bacterial‐dominated biofilm was observed. The open circuit potential (OCP) and the breakdown potential (E_b) of the specimens with biofilms showed a positive shift compared to those of the freshly polished specimens. Though ennoblement of breakdown potential showed protective nature of biofilm, ageing of the algal‐dominated biofilm was found to initiate localised corrosion of the substratum due to the heterogeneities in the biofilm, creating anodes and cathodes. In the case of specimens containing 123‐day old algal‐dominated biofilm, steady increase in current density was observed during polarization starting from OCP which is indicative of initiation and steady propagation of crevice corrosion.     

Applications of artificial neural networks for refrigeration, air-conditioning and heat pump systems—A review

In this paper, an attempt has been made to review the applications of artificial neural networks (ANN) for energy and exergy analysis of refrigeration, air conditioning and heat pump (RACHP) systems. The studies reported are categorized into eight groups as follows: (i) vapour compression systems (ii) RACHP systems components, (iii) vapour absorption systems, (iv) prediction of refrigerant properties (v) control of RACHP systems, (vi) phase change characteristics of refrigerants, (vii) heat ventilation air conditioning (HVAC) systems and (viii) other special purpose heating and cooling applications. More than 90 published articles in this area are reviewed. Additionally, the limitations with ANN models are highlighted. This paper concludes that ANN can be successfully applied in the field of RACHP systems with acceptable accuracy.     

A comparative study of vegetable oil methyl esters (biodiesels)

In the present study, rubber seed oil, coconut oil and palm kernel oil, which are locally available especially in Kerala (India), are chosen and their transesterification processes have been investigated. The various process variables like temperature, catalyst concentration, amount of methanol and reaction time were optimized. Biodiesel from rubber seed oil (with high free fatty acid) was produced by employing two-step pretreatment process (acid esterification) to reduce acid value from 48 to 1.72 mg KOH/g with 0.40 and 0.35 v/v methanol-oil ratio and 1.0% v/v H₂SO₄ as catalyst at a temperature of 63(±2) °C with 1 h reaction time followed by transesterification using methanol-oil ratio of 0.30 v/v, 0.5 w/v KOH as alkaline catalyst at 55(±2) °C with 40 min reaction time to yield 98-99% biodiesel. Coconut oil and palm oil, being edible oils, transesterification with 0.25 v/v methanol-oil ratio, 0.50% w/v KOH as at 58(±2) °C, 20 min reaction time for coconut oil and 0.25% v/v methanol-oil ratio, 0.50% w/v KOH as alkaline catalyst at 60(±2) °C for palm kernel oil will convert them to 98-99% biodiesel. The brake thermal efficiency of palm oil biodiesel was higher with lower brake specific fuel consumption, but rubber seed oil biodiesel(ROB) showed less emission (CO and NO_x) compared to other biodiesels.     

Functional food components of Antigonon leptopus tea

The tubers and flowers of Antigonon leptopus, belonging to the family Polygonaceae, are consumed as food in several parts of the world. The aerial portion, including flowers, is used in the preparation of tea used as a cold remedy. This prompted us to investigate its functional food qualities and found that the methanol extract of the aerial parts of A. leptopus, inhibited lipid peroxidation (LPO) by 89% and cyclooxygenase enzymes, COX-1 and COX-2 by 50.4% and 72.5%, respectively, at 250 μg/ml. Purification of the methanolic extract yielded n-hentriacontane (1), ferulic acid (2), 4-hydroxycinnamic acid (3), quercetin-3-rhamnoside (4), and kaempherol-3-glucoside (5) along with β-sitosterol, β-sitosterol-glucoside and d-mannitol. Compounds 3, 4 and 5 inhibited LPO by 19.5%, 41.0%, and 60.5%, respectively, at 5 μg/ml. Similarly, compounds 3, 4 and 5 inhibited COX-1 enzyme by 64.7%, 16.9%, and 38.5% and COX-2 enzyme by 87.4%, 88.8%, and 90.2%, respectively, at 25 μg/ml. Compounds 3, 4 and 5 showed 50% inhibition (IC₅₀) at 17.4%, 68.9% and 36.3 μg/ml, against COX-1 and 8.57%, 7.86% and 6.78 μg/ml for COX-2, respectively. This is the first report of the isolation of compounds 2–5 from A. leptopus and their LPO and COX inhibitory activities.