Synthesis and quadratic molecular hyperpolarizabilities of two new chiral boronates: Computational and experimental study

A monomeric boronate and an oxobridged chiral dimer were obtained by reaction of the ligand derived from 4-diethylaminosalicylaldehyde with (R)-(−)-phenylglycinol, and phenyl boronic acid or boric acid. The compounds were fully characterized by spectroscopic techniques (¹H, ¹³C, ¹¹B NMR, elemental analyses, IR and masses spectrometry); and their molecular hyperpolarizabilities were investigated by the electric field induced second harmonic (EFISH) technique and semi-empirical calculations. The experimental quadratic hyperpolarizability which is equal to 9.8 × 10⁻³⁰ cm⁵ esu⁻¹ at 1.064 μm for the monomeric derivative rises to 19.5 × 10⁻³⁰ cm⁵ esu⁻¹ in the dimeric specie.     

Coupled chaotic oscillators and their relation to a central pattern generator for artificial quadrupeds

Animal locomotion employs different periodic patterns known as animal gaits. In 1993, Collins and Stewart recognized that gaits possessed certain symmetries and characterized the gaits of quadrupeds and bipeds using permutation symmetry groups, which impose constraints on the locomotion center called the central pattern generator (CPG) in the animal brain. They modeled the CPG by coupling four nonlinear oscillators and found that it was possible to reproduce all symmetries of the gaits by changing the coupling strength. Here we propose to extend this idea using coupled chaotic oscillators synchronized using the Pyragas method in order to characterize the CPG symmetries. We also evaluate the time series behavior when the foot is in contact with the ground: this has potential robotic applications.     

Configuration and leishmanicidal activity of (-)-argentilactone epoxides

Epoxidation of argentilactone (1) with m-chloroperbenzoic acid gave a diasteromeric mixture of 2 and 3 in a ratio 1.8 : 1, with total yield 60%. The configuration of 7,8-oxirane ring for both diasteromers was determined by NMR analysis. Reaction of 1 with urea hydrogen peroxide gave the 3,4-epoxide (4) in 65% yield. The in vitro activity of 2, 3, 4 and argentilactone against Leishmania amazonensis was tested, only epoxides (2) and (3) showed leishmanicidal effect.     

Stationary Bifurcations Control with Applications

Given a family of nonlinear control systems, where the Jacobian of the driver vector field at one equilibrium has a simple zero eigenvalue, with no other eigenvalues on the imaginary axis, we split it into two parts, one of them being a generic family, where it is possible to control the stationary bifurcations: saddle-node, transcritical and pitchfork bifurcations, and the other one being a non-generic family, where it is possible to control the transcritical and pitchfork bifurcations. The polynomial control laws designed are given in terms of the original control system. The center manifold theory is used to simplify the analysis to dimension one. Finally, the results obtained are applied to two underactuated mechanical systems: the pendubot and the pendulum of Furuta.     

The minimization of open stacks problem: A review of some properties and their use in pre-processing operations

Pre-processing operations that reduce the size of a problem may be decisive for solving or not solving practical instances of a NP-hard problem. In this article we review some properties suggested in the literature for the minimization of open stacks problem that can be used in pre-processing operations to reduce the instances sizes. We also present a new pre-processing technique that may be very effective in reducing the size of an instance. We present computational tests with the suggested pre-processing operations applied on sets of MOSP instances of the literature and we show that the reductions obtained can be significant.     

Refractive index change mechanisms in femtosecond laser written ceramic Nd:YAG waveguides: micro-spectroscopy experiments and beam propagation calculations

The effect that femtosecond laser filamentation has on the refractive index of Nd:YAG ceramics, and which leads to the formation of waveguide lasers, has been studied by micro-spectroscopy imaging, beam propagation experiments and calculations. From the analysis of the Nd³⁺ luminescence and Raman images, two main types of laser induced modifications have been found to contribute to the refractive-index change: (i) a lattice defect contribution localized along the self-focusing volume of the laser pulses, in which lattice damage causes a refractive-index decrease, and (ii) a lattice strain-field contribution around and inside the filaments, in which the pressure-driven variation of the inter-atomic distances causes refractive-index variations. Scanning near-field optical-transmission and end-coupling experiments, in combination with beam propagation calculations, have been used to quantitatively determine the corresponding contribution of each effect to the refractive-index field of double-filament waveguides. Results indicate that the strain-field induced refractive-index increment is the main mechanism leading to waveguiding, whereas the damage-induced refractive-index reduction at filaments leads to a stronger mode confinement.     

Microwave synthesis of 1-aryl-1H-pyrazole-5-amines

A microwave-mediated synthesis of 1H-pyrazole-5-amines utilizing 1?M HCl at 150?°C was developed in order to provide products in a matter of minutes with minimal purification. Most reactions are complete in only 10?min and can be isolated via a simple filtration without the need for further purification by column chromatography or recrystallization. This method tolerates a range of functional groups and can be performed on milligram to gram scales.     

Evaluation of UV-C induced changes in Escherichia coli DNA using repetitive extragenic palindromic-polymerase chain reaction (REP-PCR)

Ultraviolet radiation is an efficient inactivation method for a broad range of bacteria, viruses and parasites. Inactivation of microorganisms by UV-B and UV-C radiation is driven through modifications in their genomic DNA, being the most stable DNA-lesions different kinds of pyrimidine dimers (PDs) (e.g., cyclobutane pyrimidine dimers (CPDs) and other photoproducts). Taking into account that these modifications inhibit the DNA polymerization in vivo as well as in vitro, in the present work the usefulness of the REP-PCR assay to detect UV-induced changes in the Escherichia coli DNA was evaluated. In vitro amplification of DNA extracted at different times after UV treatment showed a disappearance of amplicons of higher size as time of treatment increases. When the bacteria were let to progress through their dark repair process, modifications in the electrophoretic patterns by REP-PCR were observed again. Amplified bacterial DNA tended to recover the profile showed at the beginning of treatment. In addition, the reappearance of bands of higher molecular size was associated to an increase in their signal intensity probably due to a higher amplification rate. Results of REP-PCR were correlated to the colony-forming ability of E. coli. It was concluded that REP-PCR appears as a rapid, robust, useful complementary methodology to monitor the impact of UV irradiation--at a molecular level--on the inactivation and the mechanisms of repair, applicable on a broad spectrum of microorganisms.     

Inside Cover: Charge‐Conversional Polyionic Complex Micelles—Efficient Nanocarriers for Protein Delivery into Cytoplasm (Angew. Chem. Int. Ed. 29/2009)

A highly efficient protein delivery into cytoplasm is described by K. Kataoka, and co‐workers on page 5309 ff. The charge‐density increase of a protein cargo by reversible modification, which was based on the charge‐conversional moieties citaconic amide and cis‐aconitic amide, helped the stability of protein/block copolymer polyionic complex (PIC) micelles. The rapid protein charge conversion in endosomes induced the dissociation of the PIC micelles and efficient endosomal escape.