Novel carboxylated pyrrole- and carbazole-based monomers. Synthesis and electro-oxidation features

Carboxylated pyrrole (Pyr, a index)- and carbazole (Cbz, b index)-containing monomers 6-7a/b and 9a/b have been readily synthesized from the monobenzyl ester of L-glutamic acid and triamine 2 using Clauson-Kaas and amide coupling reactions. In contrast to Pyr-containing compounds 6-7a, and 9a, the three Cbz-containing monomers 6-7b, and 9b have been found electroactive and were successfully electropolymerized on a Pt electrode resulting in the deposition of corresponding insoluble electroconducting polyCOOH polyCbz-films poly(6-7b) and poly(9b).     

Frequency conversion in novel materials and its application to high resolution gas sensing

We have constructed a compact room-temperature mid-infrared spectrometer and gas sensor, based on quasi-phase matched difference-frequency generation in periodically poled ferroelectric crystals of the KTiOPO₄ family, namely: KTiOPO₄, KTiOAsO₄ and RbTiOAsO₄. The wide tunabilty of the spectrometer (3.1–3.75 μm) enables us to cover an entire vibrational band of gases such as methane and nitrous oxide. The high spectral resolution (1 MHz) is used to investigate the spectral profile of the hyperfine components of a single rotational transition. The sensitivity of the described spectrometer is 75 parts per million. Applications of this technology include the detection of polluting or toxic gases, biomedical sensing, atmospheric research, volcanic monitoring and industrial process control.     

Monotonicity testing and shortest-path routing on the cube

We study the problem of monotonicity testing over the hypercube. As previously observed in several works, a positive answer to a natural question about routing properties of the hypercube network would imply the existence of efficient monotonicity testers. In particular, if any set of source-sink pairs on the directed hypercube (with all sources and all sinks distinct) can be connected with edge-disjoint paths, then monotonicity of functions $f:\{ 0,1\} ^n \to \mathcal{R}$ can be tested with O(n/∈) queries, for any totally ordered range $\mathcal{R}$ . More generally, if at least a µ(n) fraction of the pairs can always be connected with edge-disjoint paths then the query complexity is O(n/(∈µ(n))). We construct a family of instances of Ω(2 ⁿ ) pairs in n-dimensional hypercubes such that no more than roughly a $\frac{1} {{\sqrt n }}$ fraction of the pairs can be simultaneously connected with edge-disjoint paths. This answers an open question of Lehman and Ron [16], and suggests that the aforementioned appealing combinatorial approach for deriving query-complexity upper bounds from routing properties cannot yield, by itself, query-complexity bounds better than ≈ n ^3/2. Additionally, our construction can also be used to obtain a strong counterexample to Szymanski’s conjecture about routing on the hypercube. In particular, we show that for any δ > 0, the n-dimensional hypercube is not $n^{\tfrac{1} {2} - \delta }$ -realizable with shortest paths, while previously it was only known that hypercubes are not 1-realizable with shortest paths. We also prove a lower bound of Ω(n/∈) queries for one-sided non-adaptive testing of monotonicity over the n-dimensional hypercube, as well as additional bounds for specific classes of functions and testers.     

Spectral and temporal holograms with nonlinear optics

In this Letter we show how encoding techniques for computer-generated holograms may be used to arbitrarily shape a nonlinearly generated spectrum and consequently the temporal shape by modulating the quadratic nonlinear coefficient. We give examples of a modulation pattern and a simple setup that can generate high-order Hermite-Gauss and Airy functions through difference-frequency generation from a transform-limited Gaussian pulse, under practical fabrication considerations.     

Two new XP(O)[NHC(CH3)3]2 phosphoramidates,with X = (CH3)2N and [(CH3)3CNH]2P(O)(O)

In N,N′‐di‐tert‐butyl‐N′′,N′′‐dimethylphosphoric triamide, C₁₀H₂₆N₃OP, (I), and N,N′,N′′,N′′′‐tetra‐tert‐butoxybis(phosphonic diamide), C₁₆H₄₀N₄O₃P₂, (II), the extended structures are mediated by P(O)...(H—N)₂ interactions. The asymmetric unit of (I) consists of six independent molecules which aggregate through P(O)...(H—N)₂ hydrogen bonds, giving R₂¹(6) loops and forming two independent chains parallel to the a axis. Of the 12 independent tert‐butyl groups, five are disordered over two different positions with occupancies ranging from to . In the structure of (II), the asymmetric unit contains one molecule. P(O)...(H—N)₂ hydrogen bonds give S(6) and R₂²(8) rings, and the molecules form extended chains parallel to the c axis. The structures of (I) and (II), along with similar structures having (N)P(O)(NH)₂ and (NH)₂P(O)(O)P(O)(NH)₂ skeletons extracted from the Cambridge Structural Database, are used to compare hydrogen‐bond patterns in these families of phosphoramidates. The strengths of P(O)[...H—N]_x (x = 1, 2 or 3) hydrogen bonds are also analysed, using these compounds and previously reported structures with (N)₂P(O)(NH) and P(O)(NH)₃ fragments.     

Bond Fukui functions as descriptor of the electron density reorganization in π conjugated systems

The bond Fukui function is introduced and tested as a new reactivity index capable of predicting the evolution of bond breaking and formation processes during an organic reaction involving π conjugated systems. As an illustration, we examine many cases where substituted ethylenes and dienes may respond to different reagents to yield cycloaddition, Michael addition, and other reactions at double bonds.     

Independent mistakes in large games

Economic models usually assume that agents play precise best responses to others' actions. It is sometimes argued that this is a good approximation when there are many agents in the game, because if their mistakes are independent, aggregate uncertainty is small. We study a class of games in which players' payoffs depend solely on their individual actions and on the aggregate of all players' actions. We investigate whether their equilibria are affected by mistakes when the number of players becomes large. Indeed, in generic games with continuous payoff functions, independent mistakes wash out in the limit. This may not be the case if payoffs are discontinuous. As a counter-example we present the n players Nash bargaining game, as well as a large class of “free-rider games.” Received: November 1997/Final version: December 1999     

Effect of Extraction Methods and In Vitro Bio-Accessibility of Microencapsulated Lemon Extract

The extraction of bioactive compounds from fruits, such as lemon, has gained relevance because these compounds have beneficial properties for health, such as antioxidant and anticancer properties; however, the extraction method can significantly affect these properties. High hydrostatic pressure and ultrasound, as emerging extraction methods, constitute an alternative to conventional extraction, improving extractability and obtaining extracts rich in bioactive compounds. Therefore, lemon extracts (LEs) were obtained by conventional (orbital shaking), ultrasound-assisted, and high-hydrostatic-pressure extraction. Extracts were then microencapsulated with maltodextrin at 10% (M10), 20% (M20), and 30% (M30). The impact of microencapsulation on LEs physicochemical properties, phenolics (TPC), flavonoids (TFC) and relative bio-accessibility (RB) was evaluated. M30 promoted a higher microencapsulation efficiency for TPC and TFC, and a longer time required for microcapsules to dissolve in water, as moisture content, water activity and hygroscopicity decreased. The RBs of TPC and TFC were higher in microcapsules with M30, and lower when conventional extraction was used. The data suggest that microencapsulated LE is promising as it protects the bioactivity of phenolic compounds. In addition, this freeze-dried product can be utilized as a functional ingredient for food or supplement formulations.     

Relationship between solvation energy, chemical potential and hardness variations

Starting from a density functional theory (DFT) formalism describing the energy change from one ground state representing an isolated solute, to another one representing the same solute in the field of the solvent, it is possible to obtain a simple and useful expression for the solvation energy in terms of the variation of the electronic chemical potential and global hardness associated to the change from gas to solution phase. Since both properties may be obtained from an orbital theory within the approximate Self Consistent Reaction Field (SCRF) methodology, the proposed model is expected to be useful for the analysis of chemical reactivity in solution.