(2E)-3-(4-Bromophenyl)-1-(2-methyl-4phenyl-3-quinolyl)prop-2-en-1-one

The conformation about the ethene bond [1.316 (3) angstrom] in the title compound, C25H18BrNO, is E. The quinoline ring forms dihedral angles of 67.21 (10) and 71.68 (10)degrees with the benzene and bromo-substituted benzene rings, respectively. High-lighting the non-planar arrangement of aromatic rings, the dihedral angle formed between the benzene rings is 58.57 (12)degrees.

Studies on the conformation of amino acids XII. Energy calculations on prolyl residue

The favoured conformations of the prolyl residue have been obtained by calculating their potential energies arising from bond-angle strain, torsion-angle strain, non-bonded and electrostatic interatomic energies. In addition to the five membered ring, the peptide unit at the amino end (with ω = 180°) and the C′ atom at the carboxyl end have been taken into account. It is found that there are two local minima in the configurational space of the parameters defining the conformation, as is actually observed-one (denoted by B) with Cγ displaced on the same side as C′, which is lower in energy than the other (denoted by A) with Cγ displaced on the opposite side of C′. The other four atoms Cδ, N, Cα, Cβ are nearly in a plane. The conformations of minimum energy (for both A and B) have bond angles very close to the mean observed values while the torsion angles are well within the range observed in various structures for each type. Taking into account the fact that the influence of neighbouring molecules in a crystal structure may make the conformation of a molecule different from the minimal one, the ranges of the conformational parameters for which the energy is within 0.6 kcal/mole above the minimum value (called the "most probable range") and within 1.2 kcal/mole (called the "probable range") have been determined. The ranges thus obtained, agree well with observation, and most of the observed data lie within the most probable ranges, although differing appreciably from the conformation of minimum energy. The study has been extended, in a limited way, to the conformation of the ring in the amino acid proline. Since the nitrogen is tetrahedral in this (as contrasted with being planar in the prolyl residue), it is found that any one of the five atoms can be out of plane (either way), with the other four lying nearly in a plane. These correspond to low energy conformations (up to 1.2 kcal/mole above the minimum). One such example, in which the Cα atom is out of plane is known for dl-proline · HCl. It is also shown that in these calculations energies due to bond length distortions can be neglected to a good degree of approximation, provided the 'best' values of the bond lengths for the particular compound are used in the theoretical calculations.

Ring-Opening-Induced Toughening of a Low-Permittivity Polymer-Metal Interface

Integrating low dielectric permittivity (low-k) polymers to metals is an exacting fundamental challenge because poor bonding between low-polarizability moieties and metals precludes good interfacial adhesion. Conventional adhesion-enhancing methods such as using intermediary layers are unsuitable for engineering polymer/metal interfaces for many applications because of the collateral increase in dielectric permittivity. Here, we demonstrate a completely new approach without surface treatments or intermediary layers to obtain an excellent interfacial fracture toughness of > 13 J/m(2) in a model system comprising copper. and a cross-linked polycarbosilane with k similar to 2.7 obtained by curing a cyclolinear polycarbosilane in air.Our results suggest that interfacial oxygen catalyzed molecularring-opening and anchoring of the opened ring moieties of the polymer to copper is the main toughening mechanism. This novel approach of realizing adherent low-k polymer/metal structures without intermediary layers by activating metal-anchoring polymer moieties at the interface could be adapted for applications such as device wiring and packaging, and laminates and composites.

1,3,6-Trimethylpyrano[4,3-b]pyrrol-4(1H)-one

All the non-H atoms of the title compound, C10H11NO2, are almost coplanar [maximum deviation = 0.040 (3) angstrom]. The crystal structure is stabilized by C-H center dot center dot center dot O hydrogen bonds.

Non-destructive discrimination of Bell states by NMR using a single ancilla qubit

Discrimination of Bell states plays an important role in a number of quantum computational protocols such as teleportation and secret sharing. However, most of the protocols dealing with Bell state discrimination in the literature either involve performing correlated measurements or destroying the entanglement of the system. Here, we demonstrate an NMR-based experimental realization of a protocol for Bell state discrimination, following a scheme proposed by Gupta et al (quant-ph/0504183v1, 23 April 2005), which does not destroy the Bell state under consideration. Using the proposed protocol, one can deterministically distinguish the Bell states, without performing a measurement using the entangled basis. State discrimination is performed through two independent measurements on one ancilla qubit, which leaves the Bell states unchanged.

A non-orthogonal distributed space-time coded protocol - Part 1:Signal model and design criteria

In this two-part series of papers, a generalized non-orthogonal amplify and forward (GNAF) protocol which generalizes several known cooperative diversity protocols is proposed. Transmission in the GNAF protocol comprises of two phases - the broadcast phase and the cooperation phase. In the broadcast phase, the source broadcasts its information to the relays as well as the destination. In the cooperation phase, the source and the relays together transmit a space-time code in a distributed fashion. The GNAF protocol relaxes the constraints imposed by the protocol of Jing and Hassibi on the code structure. In Part-I of this paper, a code design criteria is obtained and it is shown that the GNAF protocol is delay efficient and coding gain efficient as well. Moreover GNAF protocol enables the use of sphere decoders at the destination with a non-exponential Maximum likelihood (ML) decoding complexity. In Part-II, several low decoding complexity code constructions are studied and a lower bound on the Diversity-Multiplexing Gain tradeoff of the GNAF protocol is obtained.

Non-unitary-weight Space-Time Block Codes with Minimum Decoding Complexity

Space-Time Block Codes (STBCs) from Complex Orthogonal Designs (CODs) are single-symbol decodable/symbol-by-symbol decodable (SSD); however, SSD codes are obtainable from designs that are not CODs. Recently, two such classes of SSD codes have been studied: (i) Coordinate Interleaved Orthogonal Designs (CIODs) and (ii) Minimum-Decoding-Complexity (MDC) STBCs from Quasi-ODs (QODs). The class of CIODs have non-unitary weight matrices when written as a Linear Dispersion Code (LDC) proposed by Hassibi and Hochwald, whereas the other class of SSD codes including CODs have unitary weight matrices. In this paper, we construct a large class of SSD codes with nonunitary weight matrices. Also, we show that the class of CIODs is a special class of our construction.

Increasing ionic conductivity of polymer-sodium salt complex by addition of a non-ionic plastic crystal

Ionic conductivity and other physico-chemical properties of a soft matter composite electrolyte comprising of a polymer-sodium salt complex and a non-ionic plastic crystal are discussed here. The electrolyte under discussion comprises of polyethyleneoxide (PEO)-sodium triflate (NaCF3SO3) and succinonitrile (SN). Addition of SN to PEO-NaCF3SO3 resulted in significant enhancement in ionic conductivity. At 50% SN concentration (with respect to weight of polymer), the polymer-plastic composite electrolyte room temperature (= 25 degrees C) ionic conductivity was similar to 1.1 x 10(-4) Omega(-1) cm(-1), approximately 45 times higher than PEO-NaCF3SO3. Observations from ac-impedance spectroscopy along with X-ray diffraction, differential scanning calorimetry and Fourier transform inrared spectroscopy strongly suggest the enhancement in the composite is ionicconductivity due to enhanced ion mobility via decrease in crystallinity of PEO. The free standing composite polymer-plastic electrolytes were more compliable than PEO-NaCF3SO3 thus exhibiting no detrimental effects of succinonitrile addition on the mechanical stability of PEO-NaCF3SO3. We propose that the exploratory PEO-NaCF3SO3-SN system.discussed here will eventually be developed as a prototype electrolyte.for sodium-sulfur batteries capable of operating at ambient and.sub-ambient conditions. (C) 2010 Elsevier B.V. All rights reserved.

Low-Complexity Near-ML Decoding of Large Non-Orthogonal STBCs using Reactive Tabu Search

Non-orthogonal space-time block codes (STBC) with large dimensions are attractive because they can simultaneously achieve both high spectral efficiencies (same spectral efficiency as in V-BLAST for a given number of transmit antennas) as well as full transmit diversity. Decoding of non-orthogonal STBCs with large dimensions has been a challenge. In this paper, we present a reactive tabu search (RTS) based algorithm for decoding non-orthogonal STBCs from cyclic division algebras (CDA) having largedimensions. Under i.i.d fading and perfect channel state information at the receiver (CSIR), our simulation results show that RTS based decoding of 12 X 12 STBC from CDA and 4-QAM with 288 real dimensions achieves i) 10(-3) uncoded BER at an SNR of just 0.5 dB away from SISO AWGN performance, and ii) a coded BER performance close to within about 5 dB of the theoretical MIMO capacity, using rate-3/4 turbo code at a spectral efficiency of 18 bps/Hz. RTS is shown to achieve near SISO AWGN performance with less number of dimensions than with LAS algorithm (which we reported recently) at some extra complexity than LAS. We also report good BER performance of RTS when i.i.d fading and perfect CSIR assumptions are relaxed by considering a spatially correlated MIMO channel model, and by using a training based iterative RTS decoding/channel estimation scheme.

Low-Complexity Near-MAP Decoding of Large Non-Orthogonal STBCs Using PDA

Non-orthogonal space-time block codes (STBC) from cyclic division algebras (CDA) are attractive because they can simultaneously achieve both high spectral efficiencies (same spectral efficiency as in V-BLAST for a given number of transmit antennas) as well as full transmit diversity. Decoding of non-orthogonal STBCs with hundreds of dimensions has been a challenge. In this paper, we present a probabilistic data association (PDA) based algorithm for decoding non-orthogonal STBCs with large dimensions. Our simulation results show that the proposed PDA-based algorithm achieves near SISO AWGN uncoded BER as well as near-capacity coded BER (within 5 dB of the theoretical capacity) for large non-orthogonal STBCs from CDA. We study the effect of spatial correlation on the BER, and show that the performance loss due to spatial correlation can be alleviated by providing more receive spatial dimensions. We report good BER performance when a training-based iterative decoding/channel estimation is used (instead of assuming perfect channel knowledge) in channels with large coherence times. A comparison of the performances of the PDA algorithm and the likelihood ascent search (LAS) algorithm (reported in our recent work) is also presented.

Belief Propagation Based Decoding of Large Non-Orthogonal STBCs

In this paper,we present a belief propagation (BP) based algorithm for decoding non-orthogonal space-time block codes (STBC) from cyclic division algebras (CDA) having large dimensions. The proposed approachinvolves message passing on Markov random field (MRF) representation of the STBC MIMO system. Adoption of BP approach to decode non-orthogonal STBCs of large dimensions has not been reported so far. Our simulation results show that the proposed BP-based decoding achieves increasingly closer to SISO AWGN performance for increased number of dimensions. In addition, it also achieves near-capacity turbo coded BER performance; for e.g., with BP decoding of 24 x 24 STBC from CDA using BPSK (i.e.,n576 real dimensions) and rate-1/2 turbo code (i.e., 12 bps/Hz spectral efficiency), coded BER performance close to within just about 2.5 dB from the theoretical MIMO capacity is achieved.

A self-consistent formulation for analysis and generation of non-uniform DNA structure

A fully self-consistent formulation is described here for the analysis and generation of base-pairs in non-uniform DNA structures, in terms of various local parameters. It is shown that the internal "wedge parameters" are mathematically related to the parameters describing the base-pair orientation with respect to an external helix axis. Hence any one set of three translation and three rotation parameters are necessary and sufficient to completely describe the relative orientation of the base-pairs comprising a step (or doublet). A general procedure is outlined for obtaining an average or global helix axis from the local helix axes for each step. A graphical representation of the local helix axes in the form of a polar plot is also shown and its application for estimating the curvature of oligonucleotide structures is illustrated, with examples of both A and B type structures.

Conformations of three heterocyclicperhydropyrrolobenzofurans and polymeric assembly via co-operative inter-molecular C-H center dot center dot center dot O hydrogen bonds

In 1-cyclo-hexyl-6,6,8a-trimethyl-3a,6,7,8a-tetra-hydro-1H-1-benzofuro[2,3-b]pyrrole-2,4(3H,5H)-dione, C19H27NO3, (I), and the isomorphous compounds 6,6,8a-trimethyl-1-phenyl-3a,6,7,8a-tetra-hydro-1H-1-benzofuro[2,3-b]pyrrole-2,4(3H,5H)-dione, C19H21NO3, (II), and 6,6,8a-trimethyl-1-(3-pyridyl)-3a,6,7,8a-tetra-hydro-1H-1-benzofuro[2,3-b]pyrrole-2,4(3H,5H)-dione, C18H20N2O3, (III), the tetra-hydro-benzo-dihydro-furo-pyrrolidine ring systems are folded at the cis junction of the five-membered rings, giving rise to a non-planar shape of the tricyclic cores. The dihydro-furan and pyrrolidine rings in (I) are puckered and adopt an envelope conformation. The cyclo-hexene rings adopt a half-chair conformation in all the mol-ecules, while the substituent N-cyclo-hexyl ring in (I) assumes a chair form. Short intra-molecular C-HcO contacts form S(5) and S(6) motifs. The isomorphous compounds (II) and (III) are effectively isostructural, and aggregate into chains via inter-molecular C-HcO hydrogen bonds.

A Training-Based Iterative Detection/Channel Estimation Scheme for Large Non-Orthogonal STBC MIMO Systems

In this paper, we propose a training-based channel estimation scheme for large non-orthogonal space-time block coded (STBC) MIMO systems.The proposed scheme employs a block transmission strategy where an N-t x N-t pilot matrix is sent (for training purposes) followed by several N-t x N-t square data STBC matrices, where Nt is the number of transmit antennas. At the receiver, we iterate between channel estimation (using an MMSE estimator) and detection (using a low-complexity likelihood ascent search (LAS) detector) till convergence or for a fixed number of iterations. Our simulation results show that excellent bit error rate and nearness-to-capacity performance are achieved by the proposed scheme at low complexities. The fact that we could show such good results for large STBCs (e.g., 16 x 16 STBC from cyclic division algebras) operating at spectral efficiencies in excess of 20 bps/Hz (even after accounting for the overheads meant for pilot-based channel estimation and turbo coding) establishes the effectiveness of the proposed scheme.