Tb3Sc2Al3O12-TbScO3 eutectic self-organized microstructure for metamaterials and photonic crystals application

Eutectics are the materials with foreseen application in the field of photonic crystals and metamaterials. In this paper, the dependence on chemical composition of the microstructures of terbium-scandium-aluminium gamet and terbium-scandium perovskite (Tb₃Sc₂Al₃O₁₂-TbScO₃) eutectics has been studied. The growth of the eutectic rods by the micro-pulling down method is presented, using compositions with several different volume fractions of the garnet and the perovskite phases, V_TSAG:V_TSP = 4, 3, 2, 1, 1/2. The phases have been characterized by powder X-ray diffraction and energy dispersive spectrometry. The relationship between the lattice constant of individual phases and the chemical composition is presented. The unidirectional growth of microrods has been also investigated by electron backscattering diffraction.     

Synthesis and reactivity of bis(cycloamidinium-2-yl)alkane bromide tribromides,brominating agents and tectons for molecular engineering

Bis(cycloamidine-2-yl)alkanes easily form bromide tribromide salts in the reduction-oxidation processes with bromine. Bis(tetrahydroimidazolium-2-yl)ethane and bis(hexahydropyrimidinium-2-yl)-ethane bromide tribromides are such new convenient brominating agents for aromatic amides in chemo- and regioselective electrophilic substitutions and α-bromination reactions. Correspondence: Katarzyna Ostrowska, Department of Organic Chemistry, Jagiellonian University, R. Ingardena 3, PL-30060 Kraków, Poland.     

A quartz crystal microbalance study on oxidation of a cobalt electrode in an alkaline solution

The electrochemical behaviour of an electrodeposited cobalt was studied in an aqueous 1 M KOH solution at potentials below ?700 mV vs. saturated calomel electrode. An Electrochemical Quartz Crystal Microbalance and a Rotating Ring Disk Electrode were used in the studies. Formation of a hardly reducible passive layer is responsible for time evolution of cyclic voltammetry curves. This layer can be reduced only by holding potential below ?900 mV. The role of active Co dissolution in the evolution of CV profiles is of minor importance.     

Pulse radiolysis of 9-anthrylmethylammonium cation in aqueous solution

The reaction of hydrated electron with 9-anthrylmethylammonium cation to form the respective anthracene radical anion in aqueous solution has been studied by the method of pulse radiolysis. The rate constant of the reaction of with is reported. It is demonstrated that the anthracene radical anion is unstable and undergoes further reactions. The spectra of transient intermediates, leading to the final reduction products, are presented.     

1′-Carbopalladated-4-ferrocenyl-1,3-oxazolines as catalysts for Heck reactions: Further evidence in support of the Pd(0)/Pd(II) mechanism

1′-Carbopalladated complexes derived from 4-ferrocenyl-1,3-oxazolines are reported in this paper as efficient catalysts for the Heck coupling of iodo- and bromoarenes with alkenes. Experimental evidence points out strongly towards the involvement of a Pd(0)/Pd(II) catalytic cycle in the mechanism of the reaction. For the first time, the disassembly of the carbopalladated complex via coupling with the olefin in a non-catalytic Heck reaction has been demonstrated to be the origin of the release of Pd(0) from the palladacycle carrier.     

The formyl fluoride photochemical laser: photochemistry and energy content of the HF photoelemination product

Photolysis (λ > 1650 Å) of formyl fluoride (HFCO) leads to HF infrared laser emission. The energy content of the HF photoelemination primary product is only a small fraction (≈ 7%) of the available excess energy. Fluorine atoms may also be produced as primary photochemical products.     

Identification of secondary metabolites in medicinal and spice plants by NIR-FT-Raman microspectroscopic mapping

This paper demonstrates the special potential of vibrational NIR FT Raman microspectroscopy for the study of fennel fruits, chamomile inflorescence and curcuma roots to obtain detailed information about their microstructure and chemical composition. Microscopic Raman maps of fennel fruits demonstrate that anethole, which is the main essential oil component, is present in the whole mericarp with highest concentration at the top of the fruit. In situ measurements obtained of the essential oil cells are dominated by two bands observed at 1657 cm(-1) and 1609 cm(-1) which are characteristic for anethole. Raman images of chamomile inflorescence show that spiroethers, identified by significant bands between 2150 and 2250 cm(-1), are accumulated in the middle part of the flower head. Due to the intense curcumin bands in the Raman spectrum of curcuma root, the distribution of this dyeing substance can be clearly determined; highest concentration of curcumin was observed on the core of the root.     

Lagrangean and Hamiltonian fractional sequential mechanics

The models described by fractional order derivatives of Riemann-Liouville type in sequential form are discussed in Lagrangean and Hamiltonian formalism. The Euler-Lagrange equations are derived using the minimum action principle. Then the methods of generalized mechanics are applied to obtain the Hamilton’s equations. As an example free motion in fractional picture is studied. The respective fractional differential equations are explicitly solved and it is shown that the limitα→1⁺ recovers classical model with linear trajectories and constant velocity. Presented at the 11th Colloquium “Quantum Groups and Integrable Systems”, Prague, 20–22 June 2002.     

Existence of a hexatic phase in porous media

Molecular simulations for simple fluids in narrow slit-shaped carbon pores exhibit crystal-hexatic and hexatic-liquid transitions that are consistent with Kosterlitz-Thouless-Halperin-Nelson-Young theory. The temperature range over which the hexatic phase is stable is dramatically widened under confinement. Remarkably, the transitions, which are continuous for a single adsorbed layer, become weakly first order when the pore can accommodate two molecular layers. Nonlinear dielectric effect measurements for CCl4 and aniline in activated carbon fibers (pore width 1.4 nm) show divergence at these transitions, confirming the hexatic phase.     

Nondestructive analysis of single rapeseeds by means of Raman spectroscopy

The value of different vegetable oils can be correlated with the content of polyunsaturated fatty acids, especially omega‐3‐fatty acids such as linolenic acid, because of their contribution to healthy nutrition. One expression for the degree of unsaturation is the iodine value normally measured with gas chromatography. The use of Raman spectroscopy allows a rapid calculation of the iodine value and, in addition, only in a minimal sample volume. Therefore, this method can be used in single rapeseeds in order to predict the iodine value before harvesting. Additionally, the method can also be used for breeding investigations. Here, the lipid content and composition of a plant can be predicted by measuring the seedling without destruction. Copyright © 2006 John Wiley & Sons, Ltd.