Non-Abelian spin liquid in a spin-one quantum magnet

We study a time-reversal invariant non-Abelian spin-liquid state in an SU(2) symmetric spin S=1 quantum magnet on a triangular lattice. The spin liquid is obtained by quantum disordering a noncollinear nematic state. We show that such a spin liquid cannot be obtained by the standard projective construction for spin liquids. We also study the phase transition between the spin liquid and the noncollinear nematic state and show that it cannot be described within the Landau-Ginzburg-Wilson paradigm.     

A heuristic method for RCPSP with fuzzy activity times

In this paper, we propose a heuristic method for resource constrained project scheduling problem with fuzzy activity times. This method is based on priority rule for parallel schedule generation scheme. Calculation of critical path in this case requires comparison of fuzzy numbers. Distance based ranking of fuzzy number is used for finding the critical path length and concept of shifting criticality is proposed for some of the special cases. We also propose a measure for finding the non-integer power of a fuzzy number. We discuss some properties of the proposed method. We use an example to illustrate the method.     

Astroparticle physics: Working group report

The astroparticle physics working group witnessed intense discussion and activity covering a broad range of topics ranging from supergravity and baryogenesis to compact stars and the large scale structure of the Universe. A summary of some of the subject areas in which collaborations were initiated during WHEPP-5 is presented below.     

Synthesis of gold–poly(methyl methacrylate) core–shell nanoparticles by surface‐confined atom transfer radical polymerization at elevated temperature

Surface‐confined atom transfer radical polymerization was used to prepare gold nanoparticle–poly(methyl methacrylate) core–shell particles at elevated temperature. First, gold nanoparticles were prepared by the one‐pot borohydride reduction of tetrachloroaurate in the presence of 11‐mercapto‐1‐undecanol (MUD). MUD‐capped gold nanoparticles were then exchanged with 3‐mercaptopropyltrimethoxysilane (MPS) to prepare a self‐assembled monolayer (SAM) of MPS on the gold nanoparticle surfaces and subsequently hydrolyzed with hydrochloric acid. The extent of exchange of MUD with MPS was determined by NMR. The resulting crosslinked silica‐primer layer stabilized the SAM of MPS and was allowed to react with the initiator [(chloromethyl)phenylethyl] trimethoxysilane. Atom transfer radical polymerization was conducted on the Cl‐terminated gold nanoparticles with the CuCl/2,2′‐bipyridyl catalyst system at elevated temperature. The rates of polymerization with the initiator‐modified gold nanoparticles exhibited first‐order kinetics with respect to the monomer, and the number‐average molecular weight of the cleaved graft polymer increased linearly with the monomer conversion. The presence of the polymer on the gold nanoparticle surface was identified by Fourier transform infrared spectroscopy and transmission electron microscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3631–3642, 2005     

Standing waves in a non-linear 1D lattice: Floquet multipliers, Krein signatures, and stability

We construct a class of exact commensurate and incommensurate standing wave (SW) solutions in a piecewise smooth analogue of the discrete non-linear Schrödinger (DNLS) model and present their linear stability analysis. In the case of the commensurate SW solutions the analysis reduces to the eigenvalue problem of a transfer matrix depending parametrically on the eigenfrequency. The spectrum of eigenfrequencies and the corresponding eigenmodes can thereby be determined exactly. The spatial periodicity of a commensurate SW implies that the eigenmodes are of the Bloch form, characterised by an even number of Floquet multipliers. The spectrum is made up of bands that, in general, include a number of transition points corresponding to changes in the disposition of the Floquet multipliers. The latter characterise the different band segments. An alternative characterisation of the segments is in terms of the Krein signatures associated with the eigenfrequencies. When one or more parameters characterising the SW solution is made to vary, one occasionally encounters collisions between the band-edges or the intra-band transition points and, depending on the the Krein signatures of the colliding bands or segments, the spectrum may stretch out in the complex plane, leading to the onset of instability. We elucidate the correlation between the disposition of Floquet multipliers and the Krein signatures, presenting two specific examples where the SW possesses a definite window of stability, as distinct from the SW’s obtained close to the anti-continuous and linear limits of the DNLS model.     

Simulation and analysis of nasalized vowels based on magnetic resonance imaging data

In this study, vocal tract area functions for one American English speaker, recorded using magnetic resonance imaging, were used to simulate and analyze the acoustics of vowel nasalization. Computer vocal tract models and susceptance plots were used to study the three most important sources of acoustic variability involved in the production of nasalized vowels: velar coupling area, asymmetry of nasal passages, and the sinus cavities. Analysis of the susceptance plots of the pharyngeal and oral cavities, -(B(p)+B(o)), and the nasal cavity, B(n), helped in understanding the movement of poles and zeros with varying coupling areas. Simulations using two nasal passages clearly showed the introduction of extra pole-zero pairs due to the asymmetry between the passages. Simulations with the inclusion of maxillary and sphenoidal sinuses showed that each sinus can potentially introduce one pole-zero pair in the spectrum. Further, the right maxillary sinus introduced a pole-zero pair at the lowest frequency. The effective frequencies of these poles and zeros due to the sinuses in the sum of the oral and nasal cavity outputs changes with a change in the configuration of the oral cavity, which may happen due to a change in the coupling area, or in the vowel being articulated.     

Syntheses and structures of mononuclear lutetium imido complexes with very short Lu-N bonds

The reaction of 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-imine (ImDippNH) with trimethylsilylmethyllithium and anhydrous lutetium trichloride affords the imido complex [LuCl2(ImNDipp)(THF)3], which, on further reaction with dipotassium cyclooctatetraenide, K2(C8H8), leads to the half-sandwich cyclooctatetraenyl complex [(eta8-C8H8)Lu(ImNDipp)(THF)2]; both complexes contain very short Lu-N bond lengths, which are shorter than any previously reported Lu-N distances.     

Microcontact printing of Concanavalin A and its effect on mammalian cell morphology

In this study a major lectin called Concanavalin A (ConA) has been micropatterned on a glass substrate by microcontact printing and the patterns have been characterized with fluorescent and atomic force microscope for their uniformity. Interaction of the patterns with mammalian cells has been investigated by culturing L929 mouse fibroblast cells on the ConA printed glass surface. Cell culture results obtained from the microcontact printed patterns have also been compared and benchmarked with another patterning technique named micromolding in capillaries (MIMIC). It has been revealed that in spite of molecular level heterogeneity and agglomeration of protein molecules in microcontact printed form, they can still interact with cell surface glycoproteins, impede the mobility of membrane receptor which results in altered morphology of the fibroblast cells.     

Diastereoselective michael initiated ring closure on vinyl sulfone-modified carbohydrates: a stereospecific and general route to alpha-substituted cyclopropanes

Suitably designed vinyl sulfone-modified furanosides act as substrates for Michael initiated ring closure reactions yielding cyclopropanated carbohydrates. The strategy is general in nature and gives access to cyclopropanes with predefined chiralities on three consecutive carbons with varying substitutions at the alpha-position.