Machining characteristics of fine grained AZ91 Mg alloy processed by friction stir processing

AZ91 Mg alloy was considered and friction stir processing (FSP) was adopted to achieve grain refinement to investigate the effect of grain size and secondary phase on machining characteristics during drilling at various speeds and feeds. Super saturated AZ91 Mg alloy was obtained after FSP and the grain refinement was achieved from (166.5±8.7) µm to (21.7±13.5) µm. Surprisingly, hardness reduced for FSP AZ91 Mg alloy (88.95±6.1) compared with AZ91 alloy (108.2±15.6), which was attributed to the reduced secondary phase. However, the mean cutting force for FSP-treated (FSPed) AZ91 Mg alloy was marginally increased. The edge damage of the drilled holes was lower for FSPed AZ91 Mg alloy compared with unprocessed AZ91 Mg alloy. Hence, it can be understood that the grain refinement may slightly increase the cutting forces during drilling but better edge finishing can be achieved in machining of AZ91 Mg alloy.     

Effect of Domestic Processing and Cooking on In Vitro Protein Digestibility of Moth Bean

Protein digestibility (in vitro) of dry seeds of moth bean cultivars varied significantly from 58.69 to 62.06%. The protein digestibility improved significantly when the seeds were given different domestic processing and cooking treatments including soaking, sprouting, ordinary cooking and pressure cooking. Pressure cooking of the seeds presoaked in plain water or mixed mineral salt solution had the most pronounced effect.     

BUBBLE TEMPERATURE MEASUREMENTS ON THE BINARY MIXTURES OF 1,4-DIMETHYLBENZENE WITH ISO -, SEC -, AND TERT - BUTANOLS AT 95 kPa

Bubble temperatures at 95 kPa over the entire composition range were measured for the three binary systems formed by 1,4-dimethylbenzene with iso-, sec-, and tert- butanols. A Swietoslawski-type ebulliometer was used for the measurements. The composition versus temperature measurements are well represented by the Wilson model.     

Analytical evaluation of DC capacitor RMS current and voltage ripple in neutral-point clamped inverters

The sizing of the DC-link capacitor in a three-level inverter is based on the RMS current flowing through it. This paper analyses the DC-link capacitor RMS current in a neutral-point clamped (NPC) inverter and expresses the same as a function of modulation index, line-side current amplitude and power factor. Analytical closed-form expressions are derived for the capacitor RMS current for single-phase half-bridge, single-phase full-bridge and three-phase three-leg topologies of a three-level inverter. The worst-case capacitor current stress is determined for each topology based on the analytical expressions. Further, analytical expressions are derived for the RMS values of low-frequency and high-frequency capacitor currents. These expressions are then used to estimate voltage ripple across the DC capacitor for sinusoidally modulated three-phase NPC inverter. The analytical expressions for the RMS current and voltage ripple are validated experimentally over a wide range of operating points.     

Characterization and in vitro and in vivo evaluation of cross-linked chitosan films as implant for controlled release of citalopram

The aim of the present study is to develop cross-linked chitosan (CH) films that can release drug over an extended period of time and that too in a controlled manner. A solution of different percentages of CH, is prepared in 1% lactic acid, followed by addition of citalopram (CTP) and then reacted with increasing amounts of glutaraldehyde (GL) to obtain films with different cross-linking densities. Prepared films are characterized for their physical and mechanical properties. The films are then subjected to in vitro drug release studies using pH 7·4 phosphate buffer saline (PBS) as dissolution medium and cumulative amount of drug released is calculated. Kinetic analysis of drug release is performed using Power law model and Higuchi’s model. With increase in concentration of CH, water absorption capacity and mechanical strength are increased; whereas, water vapour permeability and elasticity of the films are decreased. The effect of cross-linking agent, GL, is such that with an increase in the amount of GL, water vapour permeability, water absorption capacity and elasticity of the films are decreased; whereas, mechanical strength increased to some extent and then decreased. In vitro release studies indicate that films containing 3% CH, cross-linked with 2–3% GL and films containing 4% CH, cross-linked 1% GL are able to sustain the drug release for a prolonged time along with releasing almost complete drug in a desired period. Out of these batches, films containing 3% CH, cross-linked with 2–3% GL are having sufficient strength, water vapour permeation, water absorption capacity and elongation at break for implantation purpose. The in vitro degradation studies and histopathological studies were carried out with a sample film (batch C3 as in table 1) in rabbit model. In vitro degradation study indicates that the films maintained their integrity for desired implantation. The histopathological studies under optical microscope indicates that on implanting, there is no evidence of any inflammation, any foreign body granuloma or any necrosis or hemorrhage. Tissue configuration remains unaltered after 30 days of implantation. So, it can be suggested that cross-linked CH films of above said composition can be used as implant for long term application in depression and related disorders.     

Role of iron oxide impurities in electrocatalysis by multiwall carbon nanotubes: An investigation using a novel magnetically modified ITO electrodes

The role of iron oxide impurities in the electrocatalytic properties of multiwall carbon nanotubes (MWCNTs) prepared by catalytic chemical vapour decomposition method (CCVD) is studied in detail. A novel magnetically modified electrodes have been developed by which MWCNTs were immobilized on indium-tin oxide (ITO) electrodes, without any chemical binders. The electro-catalytic oxidation of dopamine, and reduction of hydrogen peroxide have been studied by cyclic voltammetry on magnetically modified electrodes with (i) MWCNTs with occluded iron oxide impurities (Fe-MWCNTs), (ii) MWCNTs grown on iron oxide nanoparticle particulate films (Io-MWCNTs) and (iii) pristine iron oxide nanoparticle particulate film (Io-NPs). A shift towards less positive potentials for the oxidation of dopamine was observed which is in the order of Fe-MWCNTs < Io-MWCNTs < Io-NPs. Similarly, trend towards less negative potentials for the reduction of hydrogen peroxide was observed. Thus, the electrocatalytic activities displayed by MWCNTs have been attributed to the iron oxide impurities associated with it. The systematic variation was related to the nature of interaction of iron oxide nanoparticles with MWCNT surface.     

Biomonitoring of endosulfan toxicity in human

Chemicals are comprehensively used worldwide to control herbs, weeds, pests, and other competing agents with various growing crops. The consumption of crops grown with these chemicals (even in small quantities) can upshot into accumulation in the human body. People can accidentally inhale these hazardous chemicals if they are in an area where they were applied. These chemicals can be ingested in a human with contaminated food and drinks. Ultimately it causes various adverse effects (chronic toxicity, teratogenic, mutagenic, carcinogenic effect, reproductive, and organ toxicity) on human health. Among the pool of these chemicals used as pesticides in the environment, exposure of endosulfan to humans has a potential health risk throughout the globe. The poisoning of endosulfan is reported frequently in society, therefore, this article highlights the toxicological and other harmful properties of endosulfan to humans and emphasized its essential biomonitoring. Its quick monitoring and effective hazard evaluation are possible with multi-omics technologies and some other analytical approaches. This review summarizes the introduction and mechanism of action of endosulfan along with some other toxic chemicals used in the agriculture work, the toxicity of endosulfan in human/environment, and importantly its biomonitoring (detection of chemicals and their metabolites in a biological sample) in human because biomonitoring is often considered as the most preferred method. Biomonitoring could be easily done in human samples (blood, hair, milk, and urine) with a multi-omics approach, which is a quick, reliable, and state-of-the-art technique.     

Precipitation hardening and hydrogen embrittlement of aluminum alloy AA7020

AA7020 Al–Mg–Zn, a medium strength aluminium alloy, is used in welded structures in military and aerospace applications. As it may be subjected to extremes of environmental exposures, including high pressure liquid hydrogen, it could suffer hydrogen embrittlement. Hydrogen susceptibility of alloy AA7020 was evaluated by slow strain-rate tensile testing, and delayed failure testing of hydrogen-charged specimens of air-cooled, duplexaged, and water-quenched duplex agedmaterials. The resistance to hydrogen embrittlement of the alloy was found to be in the order of air-cooled duplex aged alloy > as-received (T6 condition) > water quenched duplex aged material.     

Software reliability growth models based on cluster point processes

Two stochastic models on the growth of software errors under an imperfect debugging environment are discussed. The errors that are introduced into the software during the developmental phase are called primary errors, and these are assumed to be distributed according to a non-homogeneous Poisson process. Imperfect debugging of primary errors generates further errors, called secondary errors, into the system. These secondary errors are assumed to be generated according to a cluster point process. Two types of cluster point processes are considered, the Neyman-Scott and the Bartlett-Lewis cluster processes. The mean value functions for the number of primary and secondary errors are developed for both models and we use these to obtain some important reliability measures. We also develop a cost model and obtain its corresponding optimal release policies. Finally, we discuss parameter estimation based on the criterion of maximum likelihood and present a numerical example.     

Dielectric behaviour of sodium and potassium doped magnesium titanate

Pure phase of magnesium titanate (MgTiO $_{\boldsymbol{3}})$ was obtained at 1100°C by both the conventional solid-state method as well as by the flux method starting from hexahydrated magnesium nitrate and titanium dioxide as the reactants. MgTiO $_{\boldsymbol{3}}$ doped with Na or K was also prepared by the solid-state route. Na and K doped compositions led to monophasic MgTiO $_{\boldsymbol{3}}$ below 5 mol % dopant concentration while biphasic mixture of MgTiO $_{\boldsymbol{3}}$ (major phase) and MgTi $_{\boldsymbol{2}}$ O $_{\boldsymbol{5}}$ (minor phase) were obtained at higher dopant concentration. The dielectric constant and dielectric loss of MgTiO $_{\boldsymbol{3}}$ were found to be almost the same irrespective of the preparative method. MgTiO $_{\boldsymbol{3}}$ doped with 5 mol % of Na and K ions displayed optimum dielectric properties.