Green Machining to Net Shape Alumina Ceramics Prepared Using Different Processing Routes

In the present study, the net shape manufacturing of alumina ceramics was carried out using computer numerically controlled (CNC) machining of differently processed alumina green bodies using different tool materials and geometries. In case of a carbide-coated tool, severe wear was observed; on the contrary, a diamond-coated tool was used successfully. The profile of the as-machined surface was found to be smooth using diamond-coated flat tool. Near net shape alumina was demonstrated using CNC green machining from optimized machining conditions. Optical micrograph and the surface roughness of the as-machined samples showed good surface finish for the green bodies with higher binder content.     

Anomalous quantum transport through a thin film of varying impurity density with the distance from the film surface

We explore a novel transport phenomenon by studying the effect of disorder on electron transport through a thin film of varying disorder strength with the distance from its surface. A simple tight-binding model is used to describe the film which is attached to two metallic electrodes, where the coupling of this film to the electrodes is treated through the use of Newns-Anderson chemisorption theory. It is found that, in the strong disorder regime the current amplitude through the film increases with the increase of the disorder strength, while it decreases in the weak disorder regime. This strange behavior is completely opposite to that of a conventional disordered system. Our results also predict that the electron transport is significantly influenced by the finite size of the thin film.     

Metal‐Free Synthesis of Chlorinated β‐Amino Ketones via an Unexpected Reaction of Imines with Arylacetylenes in 1,1,1,3,3,3‐Hexafluoro‐2‐propanol

The metal‐free reaction of terminal arylacetylenes with α,α‐dichloroaldimines in 1,1,1,3,3,3‐hexafluoro‐2‐propanol as the sole solvent results in the rapid and selective formation of γ,γ‐dichloro‐β‐amino ketones. In this solvent the expected dichlorinated propargylamines and/or allylic amines are not formed. The dichloromethylene moiety of the aldimine acts as an activating group and is essential to accomplish this transformation. Electron‐rich acetylenes lead to the best results and work well with all imines (with or without α′‐H at the nitrogen substituent), while electron‐deficient acetylenes only reacted with N‐tert‐butylaldimines (no α′‐H). The mechanistic pathway showed 1,1,1,3,3,3‐hexafluoro‐2‐propanol to protonate the aldimine, which in the rate‐determining step will react with the arylacetylene to form a resonance‐stabilized allene cation, which is trapped by a HFIP molecule giving rise to an enol ether, which promptly hydrolyzes to furnish exclusively the β‐amino ketones. Using DFT techniques we found that the first C C bond forming step is the rate‐determining step and is associated with a barrier of about 21 kcal mol⁻¹.

     

Role of V2O5 on the formation of chemical mullite from aluminosilicate precursor

Aluminosilicate precursor for the processing of mulite ceramics was synthesized chemically from inorganic salts following colloidal route. V₂O₅ was used as a sintering additive in different ratios with the precursor powder. The powder mixes were compacted and sintered at different elevated temperatures. The sintered masses were characterized by measuring the bulk density, porosity, flexural strength and fracture toughness. The extent of mullitization and final microstructure of the sintered masses were investigated by scanning electron microscopy and XRD analysis. It was observed that V₂O₅ exhibited favourable effect on the formation of properly crystallized mullite and in the improvement of different mechanical properties.     

Design and Synthesis of Xanthone Analogues Conjugated with Aza-aromatic Substituents as Promising G-Quadruplex Stabilizing Ligands and their Selective Cancer Cell Cytotoxic Action

We have examined the stabilization of higher-order noncanonical G-quadruplex (G4) DNA structures formed by the G-rich sequences in the promoter region of oncogenes such as c-MYC, c-KIT, VEGF and BCl2 by newly synthesized, novel nitrogen-containing aromatics conjugated to xanthone moiety. Compounds with N-heterocyclic substituents such as pyridine (XNiso), benzimidazole (XBIm), quinoxaline (XQX) and fluorophore dansyl (XDan) showed greater effectiveness in stabilizing the G4 DNA as well as selective cytotoxicity for cancer cells (mainly A549) over normal cells both in terms of UV-Vis spectral titrations and cytotoxicity assay. Both fluorescence spectral titrimetric measurements and circular dichroism (CD) melting experiments further substantiated the G4 stabilization phenomenon by these small-molecular ligands. In addition, these compounds could induce the formation of parallel G4 structures in the absence of any added salt condition in Tris ⋅ HCl buffer at 25 °C. In a polymerase stop assay, the formation of stable G4 structures in the promoter of oncogenes and halting of DNA synthesis in the presence of the above-mentioned compounds was demonstrated by using oncogene promoter as the DNA synthesis template. Apoptosis-mediated cell death of the cancer cells was proved by Annexin V-PI dual staining assay and cell-cycle arrest occurred in the S phase of the cell cycles. The plausible mode of binding involves the stacking of the xanthone core on the G4 DNA plane with the possibility of interaction with the 5’-overhang as indicated by molecular dynamics simulation studies.     

Impact of Stone-Wales and lattice vacancy defects on the electro-thermal transport of the free standing structure of metallic ZGNR

We report the effect of topological as well as lattice vacancy defects on the electro-thermal transport properties of the metallic zigzag graphene nano ribbons at their ballistic limit. We employ the density function theory–Non equilibrium green’s function combination to calculate the transmission details. We then present an elaborated study considering the variation in the electrical current and the heat current transport with the change in temperature as well as the voltage gradient across the nano ribbons. The comparative analysis shows, that in the case of topological defects, such as the Stone-Wales defect, the electrical current transport is minimum. Besides, for the voltage gradient of 0.5 Volt and the temperature gradient of 300 K, the heat current transport reduces by \({\sim }62\,\%\) and \({\sim }50\,\%\) for the cases of Stones-Wales defect and lattice vacancy defect respectively, compared to that of the perfect one.     

Minimization of exit burr in face milling of medium carbon steel by exit edge beveling

Elimination, or reduction, of burrs formed during machining is drawing focus of manufacturers and researchers since long or suppressing a burr regarding its formation or removal of it through a suitable deburring process. Deburring is an extra process often required to undertake, and it involves additional time and cost. Presence of burr may cause several problems, such as difficulty in assembly, dimensional inaccuracy, injury to the operator, etc. Like other industries, avoidance of burr on milled component surfaces in railways is of concern. In the present investigation, formation of burr in face milling is tried to reduce by beveling the exit edge of blocks of medium carbon steel (45C8) which is widely used in railways for manufacture of different components. Cutting conditions are also varied to observe the effect on burr formation. It is observed that at an exit edge bevel angle of 15°, negligible burr is formed at most of the cutting conditions undertaken, and hence, recommended.     

Study of Optimal Adaptive Rule in Testing Composite Hypothesis

Abstract

In this article on sequential adaptive testing, we have studied the optimal allocation between two populations for testing a composite hypothesis involving the parameters, with the goal of decreasing allocation of one of the treatments to the order of the logarithm of the sample size while decreasing the probability of incorrect selection to zero. We have proved the result for large sample sizes both mathematically and by simulation studies.     

Models for Sorption Isotherms for Foods: A Review

This article presents basic concepts related to the thermodynamics of sorption of water and measurement of sorption isotherm for food materials. A comprehensive review of the widely used sorption models is presented. Various statistical techniques used to ascertain the effectiveness of a model to describe the sorption data are discussed. It is anticipated that this article will provide useful information to researchers pursuing work on sorption behavior of food materials as well as modeling of drying processes.