On the mechanism of stereoselection in Rh-catalyzed asymmetric hydrogenation: a general approach for predicting the sense of enantioselectivity

This account brings together the recent experimental and computational data on the mechanism of Rh-catalyzed asymmetric hydrogenation of activated double bonds. Two alternative reaction pathways (unsaturated and dihydride) are compared. It is suggested that the differences in these mechanisms are not primarily important for stereoselection, since they join in a single pathway before stereoselection occurs. This approach was used to rationalize the present discrepancies in the prediction of the sense of enantioselection for the P-stereogenic ligands and the ligands with backbone chirality.     

Subword complexity of uniform D0L words over finite groups

We deal with the subword complexity of uniform D0L words obtained from group substitutions. Our main interest is whether the subword complexity is “almost proportional” to the length of the factor. We find necessary and sufficient conditions for that. For some cases we show that this is impossible.     

Composites CaCl2/SBA-15 for adsorptive transformation of low temperature heat: Pore size effect

Each specific cycle for adsorptive heat transformation (AHT) requires appropriate adsorbent which ensures the best realization of precisely this cycle. This paper addresses a synthesis of novel composite sorbents “CaCl₂ confined to a meso-structured silicate SBA-15” with variable properties which appear to depend on the SBA pore size (8.1 and 11.8 nm). The equilibrium and dynamics of water sorption have been studied under typical conditions of isobaric stages of AHT cycle. Steep sorption isotherms are found, the pressure at which the sharp increase of water sorption is observed being higher in larger pores. This allows fine adjustment of sorbent properties to cycle boundary temperatures: the stronger water bounding by the salt confined to smaller pores results in the appropriate enhancement of the desorption and condensation temperatures.Comparison of the new composites with other adsorbents promising for AHT showed that mono-sized matrices are encouraging for both tailoring step-like sorption isotherms, managing the step position to fit given AHT cycle and fast water sorption.     

Synthesis, X-ray structure and luminescent properties of Sm^3＋ ternary complex with novel heterocyclic β-diketone and 1,10-phenanthroline （Phen）

A new neutral ternary samarium complex Sm(Phen)HL3 in which Phen is 1,10-phenanthroline and HL is (1,3-bis(1,3-dimethyl-1H-pyrazol-4-yl)-1,3-propanedione) was synthesized. Molecular structure of this complex was determined by X-ray diffraction. Under UV-light this complex is demonstrated bright red luminescence (λmax=647 nm), which was corresponding to the electric dipole 4G5/2→6H9/2 transition in Sm3+ ion. UV-absorption, excitation and emission spectra of the title compound were investigated.     

Long-time behavior of PML absorbing boundaries for layered periodic structures

In this work we consider a special case of the Perfectly Matched Layer (PML) divergence which is observed by the simulation of the planar periodic structures such as photonic crystal slabs or antenna arrays. This divergence is caused by an excitation of long-living artefact evanescent waves in these structures by an incident external pulse. We study the application of the known remedies to this problem: increasing the distance between the structure and PML, employing the κ parameter, employing non-PML absorbers. We also suggest a new simple and effective solution, where the usual PML is backed by an additional absorbing layer.     

Towards scalable synthesis of stochastic control systems

Formal synthesis approaches over stochastic systems have received significant attention in the past few years, in view of their ability to provide provably correct controllers for complex logical specifications in an automated fashion. Examples of complex specifications include properties expressed as formulae in linear temporal logic (LTL) or as automata on infinite strings. A general methodology to synthesize controllers for such properties resorts to symbolic models of the given stochastic systems. Symbolic models are finite abstractions of the given concrete systems with the property that a controller designed on the abstraction can be refined (or implemented) into a controller on the original system. Although the recent development of techniques for the construction of symbolic models has been quite encouraging, the general goal of formal synthesis over stochastic control systems is by no means solved. A fundamental issue with the existing techniques is the known “curse of dimensionality,” which is due to the need to discretize state and input sets. Such discretization generally results in an exponential complexity over the number of state and input variables in the concrete system. In this work we propose a novel abstraction technique for incrementally stable stochastic control systems, which does not require state-space discretization but only input set discretization, and that can be potentially more efficient (and thus scalable) than existing approaches. We elucidate the effectiveness of the proposed approach by synthesizing a schedule for the coordination of two traffic lights under some safety and fairness requirements for a road traffic model. Further we argue that this 5-dimensional linear stochastic control system cannot be studied with existing approaches based on state-space discretization due to the very large number of generated discrete states.     

Spark ignition engine fuel-to-air ratio control: An adaptive control approach

This paper presents the control of spark ignition (SI) internal combustion (IC) engine fuel-to-air ratio (FAR) using an adaptive control method of time-delay systems. The objective is to maintain the in-cylinder FAR at a prescribed set point, determined primarily by the state of the three-way catalyst (TWC), so that the pollutants in the exhaust are removed with the highest efficiency. The FAR controller must also reject disturbances due to canister vapor purge and inaccuracies in air charge estimation and wall-wetting (WW) compensation. Two adaptive controller designs are considered. The first design is based on feedforward adaptation while the second design is based on both feedback and feedforward adaptation incorporating the recently developed adaptive posicast controller (APC). Both simulation and experimental results are presented demonstrating the performance improvement by employing the APC. Modifications and improvements to the APC structure, which were developed during the course of experimentation to solve specific implementation problems, are also presented.     

On smooth optimal control determination

When using the Pontryagin Maximum Principle in optimal control problems the most difficult part of the numerical solution is associated with the non-linear operation of the maximization of the Hamiltonian over the control variables. For a class of problems, the optimal control vector is a vector function with continuous time derivatives. A method is presented to find this smooth control without the maximization of Hamiltonian. Three illustrative examples are considered.     

Millimeter- and submillimeter-wave characterization of various fabrics

Transmission measurements of 14 fabrics are presented in the millimeter-wave and submillimeter-wave electromagnetic regions from 130 GHz to 1.2 THz. Three independent sources and experimental set-ups were used to obtain accurate results over a wide spectral range. Reflectivity, a useful parameter for imaging applications, was also measured for a subset of samples in the submillimeter-wave regime along with polarization sensitivity of the transmitted beam and transmission through doubled layers. All of the measurements were performed in free space. Details of these experimental set-ups along with their respective challenges are presented.     

Poly(2-hydroxyethyl methacrylate) emboli with increased haemostatic effect for correction of haemorrhage of complex origin in endovascular surgery of children

Poly(2-hydroxyethyl methacrylate) (PHEMA) embolization particles with enhanced haemostatic properties were prepared by bulk or suspension polymerisation of 2-hydroxyethyl methacrylate (HEMA) followed by particle soaking in ethamsylate solution. The particles accelerated thrombus formation as evidenced by blood analysis of rabbits with implanted emboli. Usefulness of both spherical and cylindrical PHEMA particles with enhanced haemostatic effect was demonstrated on the embolization of arterial anastomosis, fistulas of the lower extremity and abdominal cavity, haemangioma and arteriovenous malformation of the head of several children.