<Emphasis Type="Italic">Brassica rapa</Emphasis> var. <Emphasis Type="Italic">japonica</Emphasis> Leaf Extract Mediated Green Synthesis of Crystalline Silver Nanoparticles and Evaluation of Their Stability,Cytotoxicity and Antibacterial Activity

Silver nanoparticles (AgNPs) were successfully synthesized from the reduction of Ag⁺ using AgNO₃ solution as a precursor and Brassica rapa var. japonica leaf extract as a reducing and capping agent. This study was aimed at synthesis of AgNPs, exhibiting less toxicity with high antibacterial activity. The characterization of AgNPs was carried out using UV–Vis spectrometry, energy dispersive X-ray spectrometry, fourier transform infrared spectrometry, field emission scanning electron microscopy, X-ray diffraction, atomic absorption spectrometry, and transmission electron microscopy analyses. The analyses data revealed the successful synthesis of nano-crystalline Ag possessing more stability than commercial AgNPs. The cytotoxicity of Brassica AgNPs was compared with commercial AgNPs using in vitro PC12 cell model. Commercial AgNPs reduced cell viability to 23% (control 97%) and increased lactate dehydrogenase activity at a concentration of 3 ppm, whereas, Brassica AgNPs did not show any effects on both of the cytotoxicity parameters up to a concentration level of 10 ppm in PC12 cells. Moreover, Brassica AgNPs exhibited antibacterial activity in terms of zone of inhibition against E. coli (11.1?±?0.5 mm) and Enterobacter sp. (15?±?0.5 mm) which was higher than some previously reported green-synthesised AgNPs. Thus, this finding can be a matter of interest for the production and safe use of green-AgNPs in consumer products.     

Compressive mechanical properties of sawdust/high density polyethylene composites under various strain rate loadings

This article is concerned with the static and dynamic mechanical properties of high‐density polyethylene (HDPE) reinforced with sawdust (SD) at a strain rate of up to 10³ s^?1. In this study, the static and dynamic properties of HDPE/SD composites with different filler loadings of 5, 10, 15, 20, and 30 wt% SD were deliberated at different levels of strain rates (0.001, 0.01, 0.1, 650, 900, and 1100 s^?1) using a conventional universal testing machine and the split Hopkinson pressure bar apparatus. The results showed that the stress–strain curves, yield behavior, stiffness, and strength properties of the HDPE/SD composites were strongly affected by both the strain rate and the filler loadings. Furthermore, the rate sensitivityof the HDPE/SD composites showed a great dependency on the applied strain rate, increasing as the strain rate increased. However, the thermal activation values showed a contrary trend. Meanwhile, for the postdamage analysis, the results showed that the applied strain rates influenced the deformation behavior of the tested HDPE/SD composites. Moreover, for the fractographic analysis at dynamic loading, the composites showed that all the specimens underwent a severe catastrophic deformation. J. VINYL ADDIT. TECHNOL., 24:162–173, 2018. © 2016 Society of Plastics Engineers     

Synthesis of multiwalled carbon nanotubes supported on M/MCM-41 (M = Ni,Co and Fe) mesoporous catalyst by chemical vapour deposition method

Aim of this research is to develop an effective way in producing multi-walled carbon nanotubes (MWNTs) via chemical vapour deposition method using acetylene as carbon source and synthesized mesoporous M/MCM-41 (M?=?Ni, Co and Fe) as catalyst. The mesoporous MCM41 is synthesized by using sodium metasilicate as silica source of frameworks and cetyltrimethylammonium bromide as template. The effect of temperatures and growth times are investigated to produce MWNTs with high yield and high quality. The low-angle X-ray diffraction (XRD), Fourier transform infrared spectroscopy and scanning electron microscopy results verified the formation of MCM41. Meanwhile, high-angle XRD, Raman spectra and transmission electron microscopy results confirmed the synthesized carbon nanotubes at 600?°C and growth time for 30 min are multi-walled. The yield obtained is 1353 mg in 30 min. It shows that the MCM-41 has a promising potential to produce MWNTs at low cost and shorter duration.     

Thermally Resistive Electrospun Composite Membranes for Low‐Grade Thermal Energy Harvesting

In this work, thermally insulating composite mats of poly(vinylidene fluoride) (PVDF) and polyacrylonitrile (PAN) blends are used as the separator membranes. The membranes improve the thermal‐to‐electrical energy conversion efficiency of a thermally driven electrochemical cell (i.e., thermocell) up to 95%. The justification of the improved performance is an intricate relationship between the porosity, electrolyte uptake, electrolyte uptake rate of the electrospun fibrous mat, and the actual temperature gradient at the electrode surface. When the porosity is too high (87%) in PAN membranes, the electrolyte uptake and electrolyte uptake rate are significantly high as 950% and 0.53 µL s^?1, respectively. In such a case, the convective heat flow within the cell is high and the power density is limited to 32.7 mW m^?2. When the porosity is lesser (up to 81%) in PVDF membranes, the electrolyte uptake and uptake rate are relatively low as 434% and 0.13 µL s^?1, respectively. In this case, the convective flow shall be low, however, the maximum power density of 63.5 mW m^?2 is obtained with PVDF/PAN composites as the aforementioned parameters are optimized. Furthermore, multilayered membrane structures are also investigated for which a bilayered architecture produces highest power density of 102.7 mW m^?2.     

1,3,5‐Triazino Peptide Derivatives: Synthesis,Characterization, and Preliminary Antileishmanial Activity

A library of short di‐, tri‐, and tetra‐peptides with an s‐triazine moiety at the N terminus and either an amide or ethyl ester C terminus was prepared in solution and on the solid phase. The two remaining positions of the s‐triazine moiety were substituted with methoxy, morpholino, or piperidino groups. All the synthesized peptide derivatives were analyzed by HPLC and fully characterized by IR spectroscopy, ¹H and ¹³C NMR spectroscopy, elemental analysis, and mass spectrometry (MALDI TOF/TOF). A preliminary study of the antileishmanial activity of the 1,3,5‐triazinyl peptide derivatives revealed that four dipeptide amide derivatives showed higher antipromastigote or antiamastigote activity than the reference standard drug miltefosine with no significance acute toxicity.     

Optimization of cutting parameters in micro end milling operations in dry cutting condition using genetic algorithms

Micro end milling with fine grained carbide end mills is an economical way to machine small and medium lots of micro components. Considering the sensitivity of the slender end mills which are very costly compared to conventional end mills, it is imperative that the machining parameters are chosen appropriately so as to ensure maximum tool life and minimum possible production cost without violating any of the imposed constraints. Unlike in conventional end milling operations the tool life in micro end milling operations increases with axial depth of cut till it equals the tool diameter and this makes it even difficult to ascertain the appropriate depth of cut to machine a specific component. In this paper the influence of depth of cut on tool life is illustrated and depth of cut is also considered as one of the decision variables in the optimization problem. More over in this paper Genetic Algorithms (GA) based on natural laws of evolution is used to optimize the cutting parameters. Finally a test case is presented to give a clear picture of the application of the optimization algorithm.     

Factors affecting the machining accuracy of a chucked workpiece

A deviation in shape called ‘out-of-roundness’ is commonly observed in machined workpieces held by three-jaw chucks in turning operations. This out-of-roundness is due mainly to the variation in the stiffness of the workpiece-chuck-spindle system; the stiffness being higher when the cutting force is acting against a jaw and lower when acting along a jaw. This variation in stiffness of the workpiece-chuck-spindle system, termed here ‘directional orientation’, also leads to the generation of a type of parametric vibration.An attempt has been made to get rid of this effect of directional orientation by optimizing the contact between the jaw face and workpiece. Cutting tests were conducted on tapered testpeices with full contact between the jaws and the testpiece. Various contact chord lengths and spindle speeds were used. Measurements of out-of-roundness, limiting depth of cut and radial cutting force were made for analysis. Results show that where the deviation in shape of the testpiece has a three-pronged profile, and the peak at the third multiple is significant in the frequency spectrum of the radial cutting force, a contact chord length equal to the radius of the testpiece gives the optimized clamping condition.     

The Nanometer-Sized Eutectic Structure of Si/CrSi<Subscript>2</Subscript> Thermoelectric Materials Fabricated by Rapid Solidification

Nanostructuring is known to be an effective method to improve thermoelectric performance but, generally, it requires complex procedures and much labor. In the present study, self-assembled nanometer-sized composite structures of silicon (Si) and chromium disilicide (CrSi₂) were easily fabricated by the rapid solidification of a melt with a eutectic composition. Ribbon-like samples were obtained with a dominant nanostructure of fine aligned lamellae with a spacing range of 20–35 nm. The thermoelectric power factor of the ribbon was observed to be 1.2 mW/mK² at room temperature and reached 3.0 mW/mK² at 773 K. The thermal conductivity was 65% lower than that of a bulk eutectic sample. The results suggest that this method is promising for fabricating an effective nanostructure for thermoelectric performance.     

Separation of heavy metal and protein from wastewater by sulfonated polyphenylsulfone ultrafiltration membrane process prepared by glycine betaine enriched coagulation bath

This work deals with a simple and eco-friendly approach for the development of ultrafiltration membranes for the separation of environmentally hazardous substances from the water source. Polysulfone and sulfonated polyphenylsulfone blend ultrafiltration membranes were fabricated by the non-solvent induced phase inversion technique. Prepared membranes were characterized for their morphology, hydrophilicity, porosity, filtration and antifouling properties. The blend membranes with 15 wt% of sPPSU demonstrated the best performance with water flux of 190.33 Lm^?2h^?1 and flux recovery ratio of 86.56%. The effect of aq. glycine betaine (GB) coagulation bath on the membrane property and performance was studied and compared with commonly used additives such as NaCl and NMP. The GB in coagulation bath exhibited better flux and performance with protein rejection of 66.3%, 74.0% and 91.2% for trypsin, pepsin, and bovine serum albumin, respectively, and heavy metal rejection of 75.2% and 87.6% for polymer enhanced ultrafiltration of Cd²⁺ and Pb²⁺ ions, respectively.