Optimization of Supercritical Carbon Dioxide Extraction of Xanthones from Mangosteen Pericarp by Response Surface Methodology

Mangosteen fruit pericarp is one of the important sources of bioactive compound xanthone. Supercritical carbon dioxide (SC-CO₂) extraction was employed to extract xanthones from mangosteen fruit pericarp at three different levels of pressure (200–300 bar), temperature (40–60 °C) and solvent to material ratio (100–300 kg/kg). The optimal conditions for the total xanthone yield and the influence of parameters were determined by response surface methodology (RSM) using Box–Behnken design. In our study, the increase in total xanthone yield in SC-CO₂ fluid extraction depends more on the solute’s vapor effect. From response surface plots, pressure, temperature and solvent to material ratio exhibited independent and interactive effects on the extraction of xanthones. A regression equation for predicting the total xanthone yield was derived by statistical analysis, and a model with predictive ability of 0.99 was obtained. Maximum xanthone yield of 8.01% was predicted by RSM at 60 °C, 300 bar and a solvent to material ratio of 300 kg/kg while experimentally a yield of 7.56% was achieved. HPLC analysis was carried out for the optimum conditions for the identification and quantification of the xanthones. The antioxidant activities of the extracts were investigated by ferric reducing antioxidant power (FRAP) and the results showed that the extracts were enriched with antioxidant compound.     

Isolation and identification of pelargonidin 3-glucoside in mangosteen pericarp

In the present study, we have identified pelargonidin 3-glucoside, along with two known anthocyanin; cyanidin 3-sophoroside and cyanidin 3-glucoside, from acidified, methanolic extract of mangosteen pericarp. The compounds were separated by preparative HPLC after purification by partition against ethyl acetate and Amberlite XAD-7. The structures of the compounds were confirmed by high performance liquid chromatography (HPLC), UV–Vis absorption spectra, high-resolution electrospray mass spectrometry and 1D, 2D nuclear magnetic resonance (NMR) spectroscopy. This new pigment family adds to the growing body of data supporting the use of natural colourants in food. Cyanidin 3-sophoroside was the major anthocyanin detected in large amount (76.1%), followed by cyanidin 3-glucoside (13.4%) and pelargonidin 3-glucoside (6.2%).     

Optimal redundant placement of PMUs in Indian power grid — northern,eastern and north-eastern regions

Effective utilization of renewable energy sources and efficient management of electric energy are essential for any developing countries like India. This can be envisioned through the implementation of concepts of smart grid (SG). One of the key requisites for SG implementation is that the grid should be completely observable. Renovation of conventional Indian power grid to a SG necessitates incorporation of the phasor measurement units (PMUs) in the present power grid measurement and monitoring system. Since the cost of PMU is high and any bus containing a PMU makes the neighboring connected buses observable, optimal placement of PMUs is very important for complete observability of the grid. This paper proposes optimal redundant geographical locations in the northern, eastern and north-eastern regions of Indian power grid for PMU placement. The PMUs installed in these geographical locations will make the grid completely observable and maintain the observability under the conditions of failure of some PMUs or branch outages. Integer linear programming has been used for finding the optimal PMU locations. The results proposed in this paper can be a stepping stone for revamping the Indian power grid to a SG ensuring complete observability during different contingency conditions.     

A Power Optimized Continuous-Time ∆Σ ADC for Audio Applications

We present design considerations for low-power continuous-time modulators. Circuit design details and measurement results for a 15 bit audio modulator are given. The converter, designed in a 0.18 mum CMOS technology, achieves a dynamic range of 93.5 dB in a 24 kHz bandwidth and dissipates 90 muW from a 1.8 V supply. It features a third-order active-RC loop filter, a very low-power 4-bit flash quantizer, and an efficient excess-delay compensation scheme to reduce power dissipation.     

Influence of Annealing on Electrical Properties of an Organic Thin Layer-Based n-Type InP Schottky Barrier Diode

The electrical properties of a fabricated Au/polymethylmethacrylate (PMMA)/n-InP Schottky barrier diode have been analyzed for different annealing temperatures using current–voltage (I–V) and capacitance–voltage (C–V) techniques. It is observed that the Au/PMMA/n-InP structure shows excellent rectifying behavior. The extracted barrier height and ideality factor of the as-deposited Au/PMMA/n-InP Schottky contact are 0.68 eV (J–V)/0.82 eV (C–V) and 1.57, respectively. However, the barrier height (BH) of the Au/PMMA/n-InP Schottky contact increases to 0.78 eV (J–V)/0.99 eV (C–V) when the contact is annealed at 150°C for 1 min in nitrogen atmosphere. Upon annealing at 200°C, the BH value decreases to 0.72 eV (J–V)/0.90 eV (C–V) and the ideality factor increases to 1.48. The PMMA layer increases the effective barrier height of the structure by creating a physical barrier between the Au metal and the n-InP. Cheung’s functions are also used to calculate the series resistance of the Au/PMMA/n-InP structure. The interface state density (N _ss) is found to be 6.380 × 10¹² cm^?2 eV^?1 and 1.916 × 10¹² cm^?2 eV^?1 for the as-deposited and 150°C-annealed Au/PMMA/n-InP Schottky contacts, respectively. These results indicate that the interface state density and series resistance have a significant effect on the electrical characteristics of Au/PMMA/n-InP Schottky barrier devices. Finally, it is noted that the diode parameters change with increasing annealing temperature.     

Effect of different thermomechanical processing on structure and mechanical properties of electron beam melted niobium

Among the refractory metals and alloys, niobium and niobium alloys are used in variety of high temperature applications ranging from light bulbs to rocket engines because of its high melting and boiling point, lower density, good ductility at room temperature and high corrosion resistance. In this paper the effects of different thermomechanical processing on structure and mechanical properties of electron beam melted niobium ingot was investigated. The correlation among the different processing conditions and microstructure as well as mechanical properties have been investigated using optical microscope, SEM, UTM and microhardness testing. The results show that the cold forging response of EB melted ingot was very poor, where as oxidation resistant coated ingot and ingot sealed in evacuated stainless steel jacket were successfully forged at 900 °C. The cast and hot forged EBM niobium ingot was cold rolled without any intermediate annealing. The hot forged, cold rolled and annealed niobium sheets exhibit better strength as compared to cold rolled and annealed niobium sheets. The mechanical properties of all the niobium sheets processed by using different processing conditions are superior to the properties specified by ASTM standard.     

Effect of water and isooctane absorption on the flexural fatigue strength of a sheet molding compound

The effect of water and isooctane absorption on the flexural fatigue strength of a sheet molding compound (SMC-R30) is investigated. Absorption of water reduces the fatigue life of specimens of SMC-R30 as compared to the fatigue life of specimens tested in air. Absorption of isooctane reduces the fatigue life much more than absorption of water.     

MADCR:Mobility Aware Dynamic Clustering-Based Routing Protocol in Internet of Vehicles

Internet of Vehicles (IoV) is an evolution of the Internet of Things (IoT) to improve the capabil-ities of vehicular ad-hoc networks (VANETs) in in-telligence t...