Effect of Extraction Techniques and Solvents on Antioxidant Activity of Pomegranate (<Emphasis Type="Italic">Punica granatum</Emphasis> L.) Leaf and Stem

The effect of commonly used techniques and solvents in the antioxidant activities of Pomegranate leaves and stems were studied. The extraction techniques compared were successive, individual (cold percolation), and decoction methods in both parts using solvents viz. petroleum ether, toluene, ethyl acetate, acetone, and water. The antioxidant activity of all the different solvent extracts of leaves and stem was evaluated using antioxidant assays like 2,2-diphenyl-1-picryl hydrazyl free radical scavenging assay, superoxide anion radical scavenging assay and ferric-reducing antioxidant power. Total phenol and flavonoid content was also measured. Successive extraction was a better technique to extract the antioxidants from pomegranate than other techniques evaluated in the present study. For the aqueous extraction, decoction method was found to be the best method to extract the antioxidants and it is the most convenient, exhaustive, and time-saving extraction technique for both parts of pomegranate. The results showed that the extracting solvent significantly altered the antioxidant property estimations of pomegranate leaf and stem. High correlations between phenolic compositions and antioxidant activities of pomegranate extracts were observed. High levels of antioxidant activities were detected in pomegranate leaf as compared to stem indicating that the leaf may serve as an excellent source of natural antioxidants.     

Porosity control in metal-assisted chemical etching of degenerately doped silicon nanowires

We report the fabrication of degenerately doped silicon (Si) nanowires of different aspect ratios using a simple, low-cost and effective technique that involves metal-assisted chemical etching (MacEtch) combined with soft lithography or thermal dewetting metal patterning. We demonstrate sub-micron diameter Si nanowire arrays with aspect ratios as high as 180:1, and present the challenges in producing solid nanowires using MacEtch as the doping level increases in both p- and n-type Si. We report a systematic reduction in the porosity of these nanowires by adjusting the etching solution composition and temperature. We found that the porosity decreases from top to bottom along the axial direction and increases with etching time. With a MacEtch solution that has a high [HF]:[H(2)O(2)] ratio and low temperature, it is possible to form completely solid nanowires with aspect ratios of less than approximately 10:1. However, further etching to produce longer wires renders the top portion of the nanowires porous.     

Recent progress in barium zirconate proton conductors for electrochemical hydrogen device applications: A review

Electrochemical hydrogen devices like fuel cells are widely investigated as promising technologies to mitigate the rising environmental challenges and enhance the renewable energy economy. In these devices, proton-conducting oxides (PCOs) are applied as electrolyte materials to transport protons. Excellent physical stability and higher proton transport number are two essential properties of electrolyte materials. Doped BaZrO₃ (BZO) is a solid ion-conducting perovskite material with high chemical stability and good proton-conducting properties at an intermediate temperature range of 400–650 °C. Therefore, BZO is an attractive material among the exciting proton-conducting oxides as electrolyte material. To enhance the proton transport properties and improve the material fabrication process of BZO, techniques such as the use of dopants, sintering aid, synthesis methods are crucial. The present review work highlights the applications of BZO as electrolyte material in electrochemical hydrogen devices such as hydrogen isotopes separation systems, hydrogen sensors, hydrogen pumps, and protonic ceramic fuel cells (PCFCs) or solid oxide fuel cells (SOFCs). The central section of this review summarizes the recent research investigations of these applications and provides a comprehensive insight into the various synthesis process, doping, sintering aid, operating environments, and operating condition's impact on the composition, morphology, and performance of BZO electrolyte materials. Based on the reviewed literature, remarks on current challenges and prospects are provided. The presented information on in-depth analysis of the physical properties of barium zirconate electrolyte's along with output performance will guide aspirants in conducting research further on this field.     

Improved properties of hydroxyapatite–carbon nanotube biocomposite: Mechanical,in vitro bioactivity and biological studies

The present work describes a simple shear mixing technique for developing a hydroxyapatite (HAp)–carbon nanotube (CNT) nanocomposite and the effect of reinforcement on the physical, mechanical, in vitro bioactivity and biological properties of HAp. XRD and FTIR confirmed that the main phase of the composites is HAp. HRTEM images demonstrated the formation of a two-dimensional nanocomposite structure, whereas FESEM images indicated the formation of nanosized HAp grains featuring sporadically distributed CNT molecules. No major phase changes in HAp were observed with up to 5% added CNT. However, adding more than 1% CNTs caused an increase in internal crystal strain and increased substitution of CO₃²⁻ for OH⁻ and PO₄³⁻ groups in pure HAp. The average crystallite size increased from ~46 nm to ~100 nm with only 0.5% added CNT, remained nearly unaffected up to 2% CNTs thereafter and suddenly decreased at 5% CNTs (~61 nm). The FESEM and HRTEM images clearly showed the attachment of MWCNT chains on HAp grains, which directly affected the samples' fracture toughness and flexural strength. Of the samples, 1% showed maximum values of K_1C, whereas 5% showed maximum values of HV and three-point bending flexural strength. The in vitro bioactivity indicated increased apatite formation on the sample surface up to 1% CNTs after 24 weeks. However, adding 2% and 5% CNTs resulted in a manifold increase in apatite formation up to 12 weeks, after which dissolution increased up to 24 weeks, possibly due to increased substitution of CO₃²⁻ for OH⁻ and PO₄³⁻ groups. This result is confirmed by the FTIR studies. For all added CNT contents, all samples exhibited high haemocompatibility. However, there was a compromise between the observed mechanical properties and in vitro bioactivity studied up to 24 weeks, and care must be taken before selecting any final application of the nanocomposites.     

PIXE & XRD analysis of nanocrystals of Fe, Ni and Fe2O3

Nanocrystalline materials have become a subject of both scientific and industrial importance in the past decade. The present work deals with the preparation of α-Fe and Ni powders by high-energy ball mill method and chemically prepared α-Fe₂O₃ powders of nano crystalline type respectively. There is a need to characterize the trace elements in order to check the purity of these samples. The results of trace element analysis of these nanocrystals by using PIXE, characterization and size determination by XRD using Debye-Scherrer formula with full-width at half-maximum(FWHM) have been discussed.Nanocrystallinity is examined already by (TEM,FTIR and MICRO-RAMAN) experiments done previously.     

Improved sliding wear-resistance of alumina with sub-micron grain size: A comparison with coarser grained material

Un-lubricated sliding wear behaviour of sub-micron grained (average grain size, G = 0.45 μm), self-mated alumina was studied using conformal-contact with a unidirectional pin-on-disc wear testing machine. The wear characteristics of higher grained alumina samples (G = 0.95 and 4 μm) are also studied under self mating condition for comparative analysis by using similar test parameters and identical test configuration. Sub-micron grained alumina exhibits substantially higher wear resistance compared to the alumina of larger grain size. Scanning electron microscopy of the worn out test samples reveals that in un-lubricated condition, compaction of wear debris on sliding surface governs the wear characteristics of the present set of alumina. In many cases, partly revealed intergranular fracture was noticed. The strength of adhesion of the compacted wear debris with sliding surface increases with decreasing grain size. In case of alumina of larger grain size, the stability of the compacted layer decreases due to cracking. For sub-micron grained alumina, compacted layer of debris with increased adherence efficiently protects the virgin material resulting substantial decrease in wear loss.     

Allergenic relationship among four common and dominant airborne palm pollen grains from Eastern India

BACKGROUND: Palm pollen grains are predominant aeroallergens in the tropics including India. Evidence of allergenic crossreactivity had been reported from various parts of the world on different families, e.g. Poaceae, Asteraceae, etc. No such information is available about the palm pollen of tropical countries. OBJECTIVES: The present study was undertaken to find out the allergenic relationship, if any, in four common and important palm pollen in India. METHODS: A 2-year aerobiological survey was carried out at Madhyamgram situated at the suburban fringe of Calcutta Metropolis using Burkard volumetric sampler to know the seasonal variation of Areca catechu, Borassus flabellifer, Cocos nucifera and Phoenix sylvestris among others. Skin-prick tests (SPT) were performed with the relevant pollen extracts on the respiratory allergic patients. Sera from the subjects were tested directly by ELISA for estimating the allergen specific IgE. ELISA inhibitions and dot blotting were performed with pooled patients sera and four palm pollen extracts to detect the cross-reactivity. RESULTS: Among 70 patients, Areca catechu exhibited the maximum percentage (48.5%) of positive responses followed by Cocos nucifera (45.7%), Phoenix sylvestris (42.85%) and Borassus flabellifer (38.5%). On an average, 30-50% of the patients showed positive skin reactions and enhanced specific IgE level to more than one palm pollen extract. Further evidence of allergenic crossreactivity among the four palm pollen grains were provided by dot blotting and ELISA inhibition studies. In ELISA inhibition, a distinct inhibition was obtained with comparable amounts of the pollen extracts. CONCLUSION: The suburban aerobiological survey of Calcutta and SPT results confirmed that the relevant pollen types are significant contributors of aeroallergen load of the study area. ELISA inhibition studies with the pooled patients sera using antihuman IgE probe revealed the presence of shared allergenic components among the four palm pollen grains.     

Anti‐Icing Superhydrophobic Surfaces Based on Core‐Shell Fossil Particles

A novel approach for the design of functional coatings using fossil diatomaceous earth particles decorated by a thin layer of grafted polymer chains is reported. The polymer‐modified diatomaceous earth particles are able to form liquid marbles, superhydrophobic surfaces, and are highly promising for the design of anti‐icing coatings.