Mechanochemical Synthesis of High Crystalline Cerium Hexaboride Nanoparticles from CeO2‐B2O3‐Mg Ternary System

High crystalline cerium hexaboride (CeB₆) nanoparticles (NPs) were synthesized using mixture of mag‐ nesium (Mg), cerium oxide (CeO₂) and boron oxide (B₂O₃) via the mechanochemical process at room tem‐ perature. Based on the results, magnesiothermic reduction of B₂O₃ occurred after about 2 h of milling in a mechanically induced self‐sustaining reaction (MSR). The significant amount of heat produced by the reduction reaction resulted in CeO₂ reduction to elemental Ce which finally reacted with elemental B and formed CeB₆ compound. According to XRD analyses, the degree of crystallinity and lattice parameter of the product was calculated about 93 % and 4.1458 Å, respectively. The morphology observations revealed that the synthesized CeB₆ had semi‐cubic shape with the range of size 25–60 nm. The synthesis of CeB₆ during the thermal treatment was studied by simultaneous thermal analysis (STA) technique. It was found that the reduction of B₂O₃ took place after melting of Mg meanwhile, no CeB₆ phase achieved even up to 1100 °C.     

A successful combination of the equivalent material concept and the averaged strain energy density criterion for predicting crack initiation from blunt V-notches in ductile aluminum plates under mixed mode loading

Crack initiation from blunt V-notch borders in ductile A16061-T6 plates is investigated experimentally and theoretically under mixed mode I/II loading. Experimental observations with naked eye during loading indicated large plastic deformations around the notch tip at the onset of crack initiation, demonstrating large-scale yielding failure regime for the aluminum plates. To theoretically predict the experimentally obtained value of the maximum load that each plate could sustain, i.e. the load-carrying capacity, without performing elastic-plastic failure analyses, the equivalent material concept (EMC) is combined with a well-known brittle fracture criterion, namely the averaged strain energy density (ASED) criterion. It is shown that the combined EMC-ASED criterion could successfully predict the experimental results for various V-notch angles and radii.     

N-tert-Butoxycarbonylation of amines using H3PW12O40 as an efficient heterogeneous and recyclable catalyst

The commercially available heteropoly acid H₃PW₁₂O₄₀ (0.5 mol %) is a very efficient and environmentally benign catalyst for N-tert-butoxycarbonylation of amines (primary, secondary) with di-tert-butyl dicarbonate at room temperature in short reaction times (<10 min). No competitive side products such as isocyanates, ureas, N,N-di-tert-butoxycarbonyls, O-Boc and oxazolidinones were observed. Chiral α-amino alcohols and esters afforded the corresponding N-Boc derivatives chemoselectively in excellent yields.     

Carbon nanotube-based electrochemical sensors for quantifying the 'heat' of chilli peppers: the adsorptive stripping voltammetric determination of capsaicin

A sensitive electroanalytical methodology for the determination of capsaicin using adsorptive stripping voltammetry (AdsSV) at a multiwalled carbon nanotube modified basal plane pyrolytic graphite electrode (MWCNT-BPPGE) is presented. This analytical method is then further developed using a multiwalled carbon nanotube screen-printed electrode (MWCNT-SPE) demonstrating the proof-of-concept that this approach can easily be incorporated into a sensing device which is both facile to use and inexpensive to produce. Capsaicin is the chemical responsible for the hot taste of chilli peppers, and measuring the concentration of capsaicin is an indicator of how hot any given chilli pepper, hot sauce and other related foodstuffs are. Standard additions plots for AdsSV of capsaicin at open circuit potential at a MWCNT-BPPGE exhibits two linear ranges, from 0.5 to 15 microM and from 15 to 60 microM. Using the first range of calibration curve, a detection limit of 0.31 microM (based on 3sigma) is obtained. The plot of standard additions of capsaicin determined using the disposable MWCNT-SPE shows a linear range between 0.5 and 35 microM and a detection limit of 0.45 microM. MWCNT-BPPGE and MWCNT-SPE are successfully utilized for the determination of capsaicin in real samples, such as a few commercially available hot pepper sauces, and the determined values are in excellent agreement and correlation with the average Scoville unit values reported in the literature for these sauces. To the best of our knowledge, this is the first electroanalytical method using MWCNT-BPPGE or MWCNT-SPE reported for the determination of capsaicin. This method offers advantages such as precision and objectivity over the well-known but potentially subjective Scoville method (based on organoleptic testing by human tasting panels) and is facile and inexpensive compared to existing HPLC methods.     

Enhanced stability and sensitivity of ionic liquid-carbon paste electrodes at elevated temperatures

We describe the operation of ionic liquid-carbon paste electrodes at elevated temperatures and the effect of heating on the electrode performance and response. Using cyclic and square wave voltammetry and amperometry, it is shown that signals can be enhanced and stabilized by increasing the temperature of the operating solution. At low temperature, the electrode was susceptible to electrode fouling and showed poor stability, sensitivity, and linearity. An order of magnitude improvement of response for ascorbic acid was possible by operating the electrode at 60 degrees C compared to 0 degrees C. This study represents the first report showing that the analytical response of ionic liquid-carbon paste electrodes can be improved by operating them at elevated temperatures for a number of applications.     

Nonlocal vibration analysis of circular double-layered graphene sheets resting on an elastic foundation subjected to thermal loading

Based on the nonlocal elasticity theory, the vibra-tion behavior of circular double-layered graphene sheets (DLGSs) resting on the Winkler- and Pasternak-type elas-tic foundations in a thermal environment is investigated. The governing equation is derived on the basis of Eringen’s nonlocal elasticity and the classical plate theory (CLPT). The initial thermal loading is assumed to be due to a uniform temperature rise throughout the thickness direc-tion. Using the generalized differential quadrature (GDQ) method and periodic differential operators in radial and cir-cumferential directions, respectively, the governing equation is discretized. DLGSs with clamped and simply-supported boundary conditions are studied and the influence of van der Waals (vdW) interaction forces is taken into account. In the numerical results, the effects of various parameters such as elastic medium coefficients, radius-to-thickness ratio, thermal loading and nonlocal parameter are examined on both in-phase and anti-phase natural frequencies. The results show that the thermal load and elastic foundation respec-tively decreases and increases the fundamental frequencies of DLGSs.     

Description of Atom-Field Interaction via Quantized Caldirola-Kanai Hamiltonian

In this paper we outline an approach to the study of atom-field interacting systems, where the Hamiltonian of the field is simply inspired from the quantized Caldirola-Kanai Hamiltonian. As a simple physical realization of the model, the interaction between a two-level atom with such a single-mode field is studied. The explicit form of the atom-field entangled state associated with the considered system is analytically deduced and the dynamics of a few of its physical properties is numerically evaluated. To achieve the latter purposes, the temporal behavior of the degree of entanglement, atomic population inversion as well as sub-Poissonian statistics and quadrature squeezing of the field are evaluated. Moreover, the effects of the intensity of initial field and the damping parameter within the Caldirola-Kanai Hamiltonian on the above-mentioned criteria are investigated. As is shown, by adjusting the latter evolved parameters one can appropriately tune the discussed physical quantities.     

Effects of nanofluid and radiative heat transfer on the double-diffusive forced convection in microreactors

Journal of Thermal Analysis and Calorimetry - Understanding transport phenomena in microreactors remains challenging owing to the peculiar transfer features of microstructure devices and their...     

Synthesis,crystal structure,cholinesterase inhibitory activity,evaluation of insecticidal activities,and computational studies of new phosphonic acids

Molecular Diversity - In an attempt to obtain the modified and novel insecticides with low human toxicity, a series of novel mono-, bis-, and tetraphosphonic acid derivatives were designed and...