Tannase production by Bacillus licheniformis KBR6: Optimization of submerged culture conditions by Taguchi DOE methodology

Tannase production by Bacillus licheniformis KBR6 under submerged fermentation was optimized following Taguchi orthogonal array (OA) design of experiment (DOE). An OA layout of L18 (2¹ × 3⁵) was constructed with six most influensive factors on tannase biosynthesis like, carbon source (tannic acid), phosphate source (KH₂PO₄), nitrogen source (NH₄Cl), metal ion (Mg²⁺), incubation temperature and initial medium pH at three levels for the proposed experimental design. Tannase yield obtained from the 18 batches fermentation with the selected levels of each factors were processed with Qualitek-4 software at bigger is better as quality character and obtained a specific combination of factors with a predicted tannase production of 0.362 U/ml. The optimal combinations of factors (tannic acid, 1.0 g%; KH₂PO₄, 0.45 g%; NH₄Cl, 0.35 g%; MgSO₄, 0.05 g%) obtained from the proposed DOE methodology was further validated by fermentation experiment and the obtained result revealed an enhanced tannase yield of 2.18-fold (from 0.163 U/ml to 0.356 U/ml) from its unoptimized condition. Taguchi approach of DOE resulted in evaluating the main and interaction effects of the factors individually and in combination.     

MESFET MMIC Ka-band transmitter performance forhigh-volume system applications

An MMIC transmitter for high-volume smart munition applications in Ka band is developed using 0.25 μm MESFET technology. The transmitter, consisting of a voltage-controlled oscillator (VCO) and power amplifier (PA), delivers more than 100 mW of power with an overall efficiency of 10% and a linear tuning range of more than 700 MHz around 35 GHz     

Effect of chemical composition and initial heat treatment on the structure and properties of a few dual-phase steels

Dual-phase structures are produced in the three experimental steels, namely A1, A2 and A3, a) by air-cooling from the austenitising temperature (910°C) and then intercritically annealing the ferrite-pearlite structure at 750°C and 810°C followed by water quenching, and b) by water-quenching from the same austenitising temperature and then intercritically annealing the martensitic structure again at 750°C and 810°C followed by water quenching. The ferrite phases present in the alloys A1 and A2 have formed in two different ways: i) before and/or during intercritical annealing (old ferrite) and ii) during cooling of the alloys from the intercritical annealing temperature (new ferrite). The amount of new ferrite has been found to be larger in alloy A1 as compared to alloy A2. Alloy A3 did not show any measurable amount of new ferrite. TEM studies did not reveal any significant difference in microstructure in any of the alloys as a result of the initial heat treatment. The volume percent of martensite is maximum in alloy A2 and minimum in alloy A1, with alloy A3 coming in between. Although the amount of martensite in alloy A1 is somewhat lower than that in alloy A3, the overall strength of alloy A1 is higher than that of alloy A3 due possibly to the significant solid solution hardening of the ferritic matrix caused by silicon. Alloy A2 has been found to have the highest strength amongst the three alloys.     

Piezoelectric micromachined ultrasonic transducers: modeling the influence of structural parameters on device performance

Piezoelectric micromachined ultrasonic transducers (pMUTs), a potential alternative for conventional one-dimensional phased array ultrasonic transducers, were investigated. We used a modeling approach to study the performance of lead zirconate titanate (PZT)-driven pMUTs for the frequency range of 2-10 MHz, optimized for maximum coupling coefficient, as a function of device design. Using original tools designed for the purpose, a comprehensive build-test finite element model was developed to predict and measure the device performance. In particular, the model estimates the device coupling coefficient and the acoustic impedance, besides the readily extractable resonance frequency and bandwidth. To validate the model, a prototype device was built and tested, showing good agreement between the model predictions and experimental results. Modeling results indicate that the coupling coefficient is significantly affected by silicon membrane, PZT, and top electrode thickness as well as the top electrode design. Results also indicate considerable flexibility in maximizing the coupling coefficient while maintaining the device acoustic impedance at a level matching that of the human body. The bandwidth proved to be superior to that of conventional transducers, reaching 102% in some cases.     

Treatment of simulated arsenic contaminated groundwater using GAC‐Cu in batch reactor: Optimization of process parameters

This article deals with the experimental investigation related to the removal of arsenic from a simulated contaminated groundwater by the adsorption onto Cu²⁺ impregnated granular activated carbon (GAC‐Cu) in presence of impurities like Fe and Mn. The effects of adsorbent concentration, pH, and temperature on the percentage removal of total arsenic (As(T)), As(III), and As(V) have been discussed. Under the experimental conditions, the optimum adsorbent concentration for GAC‐Cu has been found to be 6 g/L with an agitation time of 24 h, which reduces the As(T) concentration from 188 to 8.5 µg/L. Maximum removal of As(V) and As(III) has been observed in the pH range of 7–9 and 9–11, respectively. Removal of all the above said arsenic species decreases slightly with increase in temperature. Presence of Fe and Mn increases the adsorption of arsenic species. Under the experimental conditions, at 30°C, maximum % removals of As(T), As(III), As(V), Fe, and Mn are found to be 95.5%, 93%, 98%, 100%, and 40%, respectively. It has also been observed that maximum regeneration (～94%) of spent GAC‐Cu is exhibited by a 5NH₂SO₄ solution.     

Laboratory based approaches for arsenic remediation from contaminated water: recent developments

Arsenic contamination in water has posed severe health problems around the world. In spite of the availability of some conventional techniques for arsenic removal from contaminated water, development of new laboratory based techniques along with enhancement and cost reduction of conventional techniques are essential for the benefit of common people. This paper provides an overview of the arsenic issue in water such as modes of contamination of ground water as well as surface water by arsenic, its metabolism and health impacts, factors influencing arsenic poisoning, fundamentals of arsenic poisoning mechanism and world scenario of arsenic poisoning. It discusses and compares the conventional laboratory based techniques, like precipitation with alum, iron, Fe/Mn, lime softening, reverse osmosis, electro dialysis, ion exchanges, adsorption on activated alumina/carbon, etc., for arsenic removal from contaminated water. It also discusses the best available techniques and mentions the cost comparison among these techniques too. Recent developments in the research on the laboratory based arsenic removal techniques, like improvement of conventional techniques and advances in removal technology along with its scopes and limitations have also been reviewed.     

Statistical Analysis and Optimization of Process Parameters in Wire Cut Machining of Welded Nanostructured Hardfacing Material

Silicon - Wire electric discharge machining (WEDM) is a nontraditional machining technique to cut hard and conductive material with the assistance of a moving electrode. Nanostructured hardfacing...