Transient [3,3] Cope rearrangement of 3,3-dicyano-1,5-dienes: computational analysis and 2-step synthesis of arylcycloheptanes.

A simple and modular route to arylcycloheptene scaffolds is reported. The two-step route from Knoevenagel adducts and allylic electrophiles is made possible through the design of a Cope rearrangement that utilizes a "traceless" activating group to promote an otherwise thermodynamically unfavorable transformation. Experimentally, the [3,3] rearrangement occurrs transiently at room temperature with a computed barrier of 19.5 kcal mol-1, which ultimately allows for three-component bis-allylation. Ring-closing metathesis delivers the arylcycloheptane and removes the activating group. This report describes the design and optimization of the methodology, scope and mechanistic studies, and computational analysis

Quantum optical effective-medium theory for loss-compensated metamaterials

A central aim in metamaterial research is to engineer sub-wavelength unit cells that give rise to desired effective-medium properties and parameters, such as a negative refractive index. Ideally one can disregard the details of the unit cell and employ the effective description instead. A popular strategy to compensate for the inevitable losses in metallic components of metamaterials is to add optical gain material. Here we study the quantum optics of such loss-compensated metamaterials at frequencies for which effective parameters can be unambiguously determined. We demonstrate that the usual effective parameters are insufficient to describe the propagation of quantum states of light. Furthermore, we propose a quantum-optical effective-medium theory instead and show that it correctly predicts the properties of the light emerging from loss-compensated metamaterials.Comment: 6 pages, 3 figures. Accepted for Physical Review Letter

Antimicrobial activity of the ethanolic extract of Bryonopsis laciniosa leaf, stem, fruit and seed

Antimicrobial activity of ethanolic extract of the leaf, stem, seed and fruit of an Indian medicinal plant, Bryonopsis laciniosa, used traditionally as potent medication in healing several ailments such as adenopathy, ague, asthma, bronchitis, cholera, colic, consumption, convulsion, cough, fertility and phthisis, was tested against different pathogenic microorganisms by agar well diffusion method. Leaf and stem extracts of B. Laciniosa exhibited antimicrobial activity against different Gram positive and Gram negative bacteria. The extents of the growth inhibition of bacteria were measured for each extract and Staphylococcus aureus, Micrococcus luteus and Bacillus cerues exhibited significant growth inhibition zone. Minimum inhibitory concentrations (MIC) exhibited by stem extract against the tested organisms ranged between 0.156 and 5 mg/ml; and for leaf extracts it varied between 0.625 and 10 mg/ml. Antimicrobial activities of the crude plant extracts were comparable to those of the standard antibiotics. This study concluded that B. Laciniosa used as a traditional medicinal plant has antimicrobial activity against pathogenic microorganisms

On higher derivative corrections to Wess-Zumino and Tachyonic actions in type II super string theory

We evaluate in detail the string scattering amplitude to compute different interactions of two massless scalars, one tachyon and one closed string Ramond-Ramond field in type II super string theory. In particular we find two scalar field and two tachyon couplings to all orders of $\alpha'$ up to on-shell ambiguity. We then obtain the momentum expansion of this amplitude and apply this infinite number of couplings to actually check that the infinite number of tachyon poles of S-matrix element of this amplitude for the $p=n$ case (where $p$ is the spatial dimension of a D$_p$-brane and $n$ is the rank of a Ramond-Ramond field strength) to all orders of $\alpha'$ is precisely equal to the infinite number of tachyon poles of the field theory. In addition to confirming the couplings of closed string Ramond-Ramond field to the world-volume gauge field and scalar fields including commutators, we also propose an extension of the Wess-Zumino action which naturally reproduces these new couplings in field theory such that they could be confirmed with direct S-matrix computations. Finally we show that the infinite number of massless poles and contact terms of this amplitude for the $p=n+1$ case can be reproduced by Chern-Simons, higher derivative corrections of the Wess-Zumino and symmetrized trace tachyon DBI actions.Comment: 51 pages, some refs and comments added, typos are removed. Almost all ambiguities in BPS and non-BPS effective actions have been addresse