The design of a radio frequency quadrupole LINAC for the RIB project at VECC Kolkata

A radio frequency quadrupole LINAC has been designed for the VECC-RIB project for an input beam energy of 1.0 keV/u and q/A≥1/16. The output energy will be about 90 keV/u for a 3.4 m long, 35 MHz structure. A half-scale cold model of the RFQ has been fabricated and tested for rf structure design study. The beam dynamics and rf-structure design along with the results of the cold model tests will be presented.     

Diameter-dependent coercivity of cobalt nanowires

We show that the coercivity of electrochemically grown cobalt nanowires (NWs) within the pores of a polycarbonate membrane can be changed to a large extent by tuning their diameters. The face centered cubic crystalline structure of the NWs having diameter in the range of 10 to 200 nm could be retained. Smaller diameter wires (below 30 nm) are found to be single crystalline and oriented in the [110] growth direction, but for higher diameter wires the crystallite size became very small. Magnetization measurements with an applied field parallel to the axis of the NWs show that the nature of the M–H loop changes from square to linear as the diameter of the NWs increases. The coercivity was found to be 1700 Oe and 480 Oe at 5 K (1000 Oe and 250 Oe at 300 K) for 10 nm and 100 nm wires, respectively. The observed changes in the nature of the M–H loop and in coercivity could be explained following the Stoner–Wohlfarth model and using the fact that the domain size reduces as the diameter of the wires increases.     

Effect of nanofillers on thermal and transport properties of potassium iodide–polyethylene oxide solid polymer electrolyte

In order to enhance the ionic conductivity of polyethylene oxide (PEO)–KI(80:20) based alkaline polymer electrolytes, nanosized inorganic filler ZnS has been incorporated into PEO–KI matrix and the corresponding nanocomposite polymer electrolytes are synthesized by the usual solution casting procedure. Atomic force microscope image of composite polymer electrolyte exhibits that the introduction of ZnS nanoparticles changes the surface morphology and aggregates them to form an arborization pattern. The prepared nanocomposite polymer electrolyte reveals an ionic conductivity of about 10^?4 S cm^?1 for 5 wt% ZnS at room temperature.     

A computational perspective on the kinetics and thermochemistry of the gas phase reactions of 1, 1-dichlorodimethylether (DCDME) with OH radical at 298 K

Kinetics and thermochemistry of the gas phase reactions between CH₃OCHCl₂ (DCDME) and OH radical are investigated theoretically. The geometries and all the stationary points on the potential energy surface are calculated at BHandHLYP/6-311G(d,p) method. The energy information is further refined at CCSD(T)/6-311G(d,p) level of theory. Reaction profiles are modelled including the formation of two pre-reactive and post-complexes. The rate constants, which are evaluated by Canonical Transition State Theory (CTST) including tunnelling correction at 298 K, are in very good agreement with the available experimental data. The percentage contributions of both reaction channels are also reported at 298 K. The hydrogen abstraction reaction from the –CHCl₂ group is found to be dominant leading to the formation of CH₃OCCl₂ + H₂O. Using group-balanced isodesmic reactions, the standard enthalpies of formation for CH₃OCHCl₂, CH₃OCCl₂ and CH₂OCHCl₂ are also reported.     

L1 regression estimate and its bootstrap

We study the asymptotic distribution of the L ₁ regression estimator under general conditions with matrix norming and possibly non i.i.d. errors. We then introduce an appropriate bootstrap procedure to estimate the distribution of this estimator and study its asymptotic properties. It is shown that this bootstrap is consistent under suitable conditions and in other situations the bootstrap limit is a random distribution. This work was supported by J.C. Bose National Fellowship, Government of India     

Ruthenium Catalyzed Intramolecular C−X (X=C,N, O,S) Bond Formation via C−H Functionalization: An Overview

Ruthenium catalyzed C−H activation is well known for its high tolerance towards the functional group and broad applicability in organic synthesis and molecular sciences, with significant applications in pharmaceutical industries, material sciences, and polymer industry. In the last few decades, enormous progress has been observed with ruthenium-catalyzed C−H activation chemistry. Notably, the vast majority of the C−H functionalization known in the literature are intermolecular, although the intramolecular variant provides fascinating new structural facet starting from the simple molecular scaffolds. Intramolecular C−H functionalization is atom economical and step efficient, results in less formation of undesired products which is easy to purify. This has created a lot of interest in organic chemistry in developing new synthetic strategies for such functionalization. The focus of this review is to present the relatively unexplored intramolecular functionalization of C−H bonds into C−X (X=C, N, O, S) bonds utilizing versatile ruthenium catalysts, their scope, and brief mechanistic discussion.     

Boron trifluoride–etherate in fluorinated alcohols: A powerful promoter system for intramolecular alkyne–aldehyde metathesis of o-(3-arylpropargyloxy)benzaldehydes

Boron trifluoride–etherate (BF₃·OEt₂) in 2,2,2‐trifluoroethanol (TFE) was found to be a highly efficient promoter system for the intramolecular alkyne–aldehyde metathesis of o-(3-arylpropargyloxy)benzaldehydes. The reaction produces the corresponding 3-aroyl-2H-chromenes in excellent yields under metal-free conditions.