Velocity of second sound in rotating liquid helium

Measurements of the velocity of second sound in rotating liquid helium show a velocity reduction proportional to the angular velocity. An explanation based on the theory of Hall and Vinen is in quantitative agreement with the measurements.     

Thermotropic biaxial nematic phase in liquid crystalline organo-siloxane tetrapodes

Infrared absorbance measurements have been carried out on two liquid crystalline organo-siloxane tetrapodes. Results unambiguously show the existence of a biaxial nematic phase below a uniaxial nematic phase. The three components of IR absorbance are used to calculate the various order parameters. On cooling, a weak first-order transition from isotropic to nematic is observed, followed by a second-order phase transition to biaxial nematic where the biaxiality parameters are found to be significantly large. Results are supported by observations from conoscopy and texture. Temperature dependences of the order parameters are well explained by the mean-field model for a biaxial phase.     

Tight-Binding study of Boron structures

We have performed Linearized Augmented Plane Wave (LAPW) calculations for five crystal structures (alpha, dhcp, sc, fcc, bcc) of Boron which we then fitted to a non-orthogonal tight-binding model following the Naval Research Laboratory Tight-Binding (NRL-TB) method. The predictions of the NRL-TB approach for complicated Boron structures such as R105 (or β-rhombohedral) and T190 are in agreement with recent first‐principles calculations. Fully utilizing the computational speed of the NRL-TB method we calculated the energy differences of various structures, including those containing vacancies using supercells with up to 5000 atoms.     

Protein–polymer hybrids: Conducting ARGET ATRP from a genetically encoded cleavable ATRP initiator

Protein–polymer hybrids are an important class of biomaterials. Described is the preparation of a genetically incorporated a non-canonical amino acid (nCAA) containing an ester linked atom transfer radical polymerization (ATRP) initiator, followed by a controlled “grafting from” polymerization. A Methanococcus jannaschii tyrosyl-tRNA synthetase/tRNA_CUA pair was selected to genetically encode p-bromoisobutyryloxymethyl-l-phenylalanine (biF) in response to an amber codon. This biF was directly incorporated into green fluorescent protein (GFP) at residue 134 generating biF-GFP. Activators regenerated by electron transfer (ARGET) ATRP was conducted under biologically relevant conditions to graft well-defined poly(oligo ethylene oxide methacrylate) from the biF-GFP. The biF-GFP retained its biofluorescence properties throughout the polymerization indicating the utility of ARGET ATRP for preparing protein–polymer hybrids. The presence of a base-labile ester bond in the initiator, allowed cleavage of the grafted polymer from the protein and directly analyze their molecular weight and molecular weight distribution using gel permeation chromatography (GPC). The cleaved final polymer had a M_n = 27,000 and a molecular weight distribution of M_w/M_n = 1.27.     

Optimization of the Microwave-Assisted Ortho Ester Claisen Rearrangement: Application to Monoterpenols

Two monoterpenols, perillyl alcohol and nerol, have been converted into their γ,δ-unsaturated ester derivatives following a modified process of microwave-assisted ortho ester Claisen rearrangement. The yields obtained (>90%) are better than those previously obtained. The optimized process needs less reaction time (5 min), smaller amount of reagent, and no solvent.