Band 5, Heft 12

We present a theoretical study of the spin dynamics in perovskite-like multiferroics with homogeneous magnetic order in the presence of external magnetic and electric fields. A particular example of such material is BeFeO 3 in which the spin cycloid can be suppressed by application of external magnetic field, doping or by epitaxial strain. Understanding the effect of the external electric field on the spin-wave spectrum of these systems is required for devices based on spin wave interference and other innovative advances of magnonics and spintronics. Thus, we propose a model for BiFeO 3 in which the thermodynamic potential is expressed in terms of polarization P\boldsymbol{P}, antiferrodistortion Ω\boldsymbol{\Omega}, antiferromagnetic moment L\boldsymbol{L} and magnetization M\boldsymbol{M}. Based on this model, we derive the corresponding equations of motion and demonstrate the existence of electromagnons, that is, magnons that can be excited by electric fields. These excitations are closely related to the magnetoelectric effect and the dynamics of the antiferrodistortion Ω\boldsymbol{\Omega}. Specifically, the influence of the external electric field on the magnon spectra is due to reorientation of both polarization P\boldsymbol{P} and antiferrodistortion Ω\boldsymbol{\Omega} under the influence of the electric field and is linked to emergence of a field-induced anisotropy.

This review outlines the recent advances in the field of asymmetric phase-transfer catalysis and the ion-pair concept including alkylation of amino acids and peptides, oxyindoles and other substrates, conjugate additions, fluorinations, photo-induced phase-transfer catalysis, Nitro-Mannich reactions, heterocyclizations and cycloadditions for the preparation of heterocycles, derivatization of isoxazoles, umpolung conjugate addition of imines and other three asymmetric reactions.

At present, Polylactic acid (PLA) is one of the most used biodegradable polyesters. The good properties and its biodegradability make that PLA can replace the fossil fuel derived polymers in different applications. PLA can be synthesized by using different methodologies. Among them, the most widely used forms on an industrial scale are the direct polycondensation of Lactic acid and the ring-opening polymerization of cyclic Lactide. The final properties of the obtained PLA are dependent on the used stereoisomers of the raw materials (Lactic acid and/or Lactide) and the conditions employed to polymerize them. Therefore, the comprehension of the synthetic mechanism of PLA is crucial to control the stereoregularity of PLA, which in turn results in an improvement of the polymer properties. So, distinct mechanisms for the synthesis of PLA by ring-opening polymerization using different catalysts systems (organometallic catalysts, cationic catalyst, organic catalyst, bifunctional catalysts) are examined in this review.

This article covers the most commercially important type of photochromic dye. It outlines which of its subclasses are of most use and how they are manufactured. The history of the industrial exploitation of this kind of colorant is briefly given before illustrating its versatility with examples of the most useful ways in which photochromic properties can be manipulated by making adjustments to molecular structure.

The presented chapter deals with technological aspects concerning industrial production of major inorganic chemicals such as sulfuric, nitric and phosphorous acids. The idea was to highlight the main assumptions related to their fabrication as well as to point out novel aspects and perspectives concerning their industry. The main attention will be paid to raw materials and their transformation in order to obtain indirect precursors of inorganic acids – acid anhydrides. Characteristics of the individual stages of synthesis, with a special regard to the process conditions will be also of key importance. The environmental impact of this particular technology will be raised and discussed. Finally, the review over recently published scientific papers, concerning innovative solutions in inorganic acids production, will be performed.