Facile synthesis of lactones and dihydronaphthalenes from methyl 2-isobutenyl (or 2-isopentenyl)cinnamates as the common intermediates

We prepared three different types of compounds, two α-alkylidene-γ-butyrolactones and 3,4-dihydronaphthalene-2-carboxylic acid from methyl 2-isobutenylcinnamates or methyl 2-isopentenylcinnamates as the common intermediates, which were derived from the acetates of Baylis-Hillman adducts.     

Thermal decomposition kinetics of Co(II), Ni(II), Cu(II) and Zn(II) complexes of dihydrazinium ethylenediamine-tetraacetate

Hydrazinium ethylenediaminetetraacetatometalate complexes of the type, N₂H₅ [M(Hedta)·H₂O] were subjected to systematic TG/DTG analysis. The decomposition process consists of three stages. Kinetic parameters were evaluated for each of these stages using the Coats-Redfern equation.     

Exact solution of Marangoni convection in a binary fluid with throughflow and Soret effect

The onset of Marangoni convection in a non-reactive binary fluid layer in the presence of throughflow and Soret effect is determined. The bottom boundary of the fluid layer is assumed to be either conducting or insulating to temperature and solute concentration perturbations while the top boundary is free and insulating. The linear stability analysis is followed and an exact solution is obtained for the corresponding eigenvalue problem by assuming that stationary convection is exhibited at the neutral state. The contribution from the Soret effect is seen only when the throughflow is weak, but however for a wider range of upward throughflow when the bottom boundary is conducting. The instability gets advanced/delayed when the Soret parameter assumes negative/positive values. The results agree well with the existing results in the literature for some particular cases.     

Atom Michelson interferometer on a chip using a Bose-Einstein condensate

An atom Michelson interferometer is implemented on an "atom chip." The chip uses lithographically patterned conductors and external magnetic fields to produce and guide a Bose-Einstein condensate. Splitting, reflecting, and recombining of condensate atoms are achieved by a standing-wave light field having a wave vector aligned along the atom waveguide. A differential phase shift between the two arms of the interferometer is introduced by either a magnetic-field gradient or with an initial condensate velocity. Interference contrast is still observable at 20% with an atom propagation time of 10 ms.     

Probabilistic electron density distribution in CdTe at RT and 200K

The bonding between the atoms in the II‐VI compound semiconductors has always been a subject of rigorous research because of their tremendous applications in a variety of fields. The bonding and ionic character in CdTe at 300 and 200 K have been determined quantitatively as well as qualitatively using single crystal X‐ray data sets and MEM (Maximum Entropy Method) as the tool for the reconstruction of the electron densities distributed within the unit cell. The ab‐initio band calculation of the total and valence charge densities have been carried out theoretically by means of the local density approximation (LDA) method in support of the experimentally derived MEM maps. The difference density maps show fewer errors between the theoretical and experimental charge density and thus gives credence to the results accordingly. Along the bonding direction [111], the mid‐bond electron densities are found to be 0.233 e/ų and 0.284 e/ų at 300 K and 200 K at distances 1.4026 Å and 1.4036 Å respectively. The densities along [100] and [110] show an increase in the charge concentration at the bond at lower temperatures. © 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

Aerodynamic force measurement using 3-component accelerometer force balance system in a hypersonic shock tunnel

A new three-component accelerometer force balance has been designed, calibrated and tested in hypersonic shock tunnel (HST2) of Indian Institute of Science. The newly designed balance is able to measure aerodynamic forces (within test time of one millisecond) on test models at angles of attack from 0 to 12°. Two models, a blunt cone with after body and a blunt cone with after body and frustum are used to establish the accuracy of the force balance. The tests were conducted for the above two configurations with a constant Mach number of 8 and total enthalpy of 2.0 MJ/kg. The effectiveness of the balance is demonstrated by comparing the forces and moments of measured data with AGARD models. The flow fields around the test model are simulated using a 3D axisymmetric Navier–Stokes solver and the simulated results were compared with the measured values. Measured and computed force data are matched within ±10% for two different models tested here. The accuracy of the force balance is also estimated with the Newtonian theory and the values are approximately ±10% for the axial component and ±8% for the normal and pitching moment components.      

Reply to the Letter-to-the-Editor of Dr. Noble Jacob regarding article “Radon isotope assessment of Submarine Groundwater Discharge (SGD) in Coleroon River Estuary,Tamil Nadu,India”, DOI: https://doi.org/10.1007/s10967-018-5877-2

Journal of Radioanalytical and Nuclear Chemistry -     

Shock tunnel study of spiked aerodynamic bodies flying at hypersonic Mach numbers

A three-component accelerometer balance system is used to study the drag reduction effect of an aerodisc on large angle blunt cones flying at hypersonic Mach numbers. Measurements in a hypersonic shock tunnel at a freestream Mach number of 5.75 indicate more than 50% reduction in the drag coefficient for a 120° apex angle blunt cone with a forward facing aerospike having a flat faced aerodisc at moderate angles of attack. Enhancement of drag has been observed for higher angles of attack due to the impingement of the flow separation shock on the windward side of the cone. The flowfields around the large angle blunt cone with aerospike assembly flying at hypersonic Mach numbers are also simulated numerically using a commercial CFD code. The pressure and density levels on the model surface, which is under the aerodynamic shadow of the flat disc tipped spike, are found very low and a drag reduction of 64.34% has been deduced numerically.