Indole derivatives as agrochemicals

The synthesis of indole derivatives prepared as potential agrochemicals is reported. The 1-carbamoyl-2-indolinones 5 showed moderate nematicidal activity while the acylureas 8 were weak insecticides. The 2,4-dinitrophenyl oxime 11c proved to be a potent herbicide with a narrow spectrum of activity.     

A new photocyclization approach to the rare 1,3-thiazino[6,5-b]indol-4-one derivatives

The analogs of indole phytoalexin cyclobrassinon have been prepared in four steps from corresponding 1-substituted 2-chloroindole-3-carboxylic acids, employing a hitherto unknown photochemical cyclization of new indolyl thiocarbamates to 1,3-thiazino[6,5-b]indole-4-one derivatives as a key step.     

Enhancement of room temperature sub-bandgap light emission from silicon photonic crystal nanocavity by Purcell effect

We report the enhancement of sub-bandgap photoluminescence from silicon via the Purcell effect. We couple the defect emission from silicon, which is believed to be due to hydrogen incorporation into the lattice, to a photonic crystal (PhC) nanocavity. We observe an up to 300-fold enhancement of the emission at room temperature at 1550 nm, as compared to an unpatterned sample, which is then comparable to the silicon band-edge emission. We discuss the possibility of enhancing this emission even further by introducing additional defects by ion implantation, or by treating the silicon PhC nanocavity with hydrogen plasma.     

An X-ray diffraction study of liquid chlorine

The static structure of liquid chlorine at room temperature is investigated by means of X-ray diffraction. From comparisons with previous neutron and X-ray data, it appears that most of the discrepancies present in the liquid structure factor between neutron and X-ray studies have been removed. Some experimental difference in the two structure factors still remains and one possible explanation is that the electron density distribution of liquid chlorine differs from that derived within the independent atom approximation.     

Spectral projected gradient and variable metric methods for optimization with linear inequalities

A family of variable metric methods for convex constrained optimizationwas introduced recently by Birgin, Martínez and Raydan.One of the members of this family is the inexact spectral projectedgradient (ISPG) method for minimization with convex constraints.At each iteration of these methods a strictly convex quadraticfunction with convex constraints must be (inexactly) minimized.In the case of the ISPG method it was shown that, in some importantapplications, iterative projection methods can be used for thisminimization. In this paper the particular case in which theconvex domain is a polytope described by a finite set of linearinequalities is considered. For solving the linearly constrainedconvex quadratic subproblem a dual approach is adopted, by meansof which subproblems become (not necessarily strictly) convexquadratic minimization problems with box constraints. Thesesubproblems are solved by means of an active-set box-constraintquadratic optimizer with a proximal-point type unconstrainedalgorithm for minimization within the current faces. Convergenceresults and numerical experiments are presented.     

Above the band gap structures in Ge nanoparticles: optical-absorption spectra

Summary We report absorption measurements on Ge nanoparticles in the range 0.6–6 eV. By reducing the dot average radius to about 13 ?, one observes a relevant blue-shift of theE ₁+Δ ₁ andE ₂ peaks and a change of the oscillator strength of the two main structures. Simulations using effective-medium theories have been carried out and the embedding matrix contribution to the measured properties has been evaluated. The different behaviour of the absorption peaksE ₁,E ₁+Δ ₁ andE ₂ under quantum confinement has been related to their specific nature within the whole Brillouin zone. The authors of this paper have agreed to not receive the proofs for correction.     

Maximum-exponent scaling behavior of optical second-harmonic generation in finite multilayer photonic crystals

Scaling laws of second-harmonic generation (SHG) in nonlinear Bragg stacks (or finite one-dimensional photonic crystals) as a function of the number N of periods are explored. While it is known that SHG scales like the sixth power of N when phase matching is achieved, we find maximal scaling like the eighth power of N under appropriate non-phase-matching conditions with the pump and harmonic waves being resonant with band-edge states. In this framework we introduce the concept of self-adaptive coherence length that scales with the system length. An analytical treatment based on coupled-mode equations clarifies the conditions for obtaining different scaling laws as a function of filling factor in the photonic gap map.