Conventional and rotating magnetoelectric effect of a half-filled spin-electron model on a doubly decorated square lattice

A conventional and rotating magnetoelectric effect of a half-filled spin-electron model on a doubly decorated square lattice is investigated by exact calculations. An importance of the electron hopping and spatial orientation of the electric field upon a magnetoelectric effect is examined in detail. A critical temperature may display one or two consecutive round maxima as a function of the electric field. Although the rotating magnetoelectric effect (RME) does not affect the ground-state ordering, the pronounced RME is found close to a critical temperature of continuous phase transition. It is shown that RME is amplified upon strengthening of the electric field, which additionally supports thermal fluctuations in destroying a spontaneous antiferromagnetic long-range order.     

Nanocrystalline alloys of Fe-Cu-Nb-Si-B after neutron irradiation

Transmission Mössbauer spectroscopy was used to study changes induced by irradiation of amorphous and nanocrystalline samples. In an as-cast sample neutrons mostly affect the orientation of a net magnetic moment. The average hyperfine field decreases towards higher neutron fluencies. In the case of the nanocrystalline samples a new disordered structure is created in the amorpous remainder corresponding to boride phases as it is shown in the samples isothermally heated from 1 to 8 hours. The structural changes of the amorphous remainder depend on the stage of crystallization and total neutron fluencies.     

Genetic algorithms for solving the discrete ordered median problem

In this paper we present two new heuristic approaches to solve the Discrete Ordered Median Problem (DOMP). Described heuristic methods, named HGA1 and HGA2 are based on a hybrid of genetic algorithms (GA) and a generalization of the well-known Fast Interchange heuristic (GFI). In order to investigate the effect of encoding on GA performance, two different encoding schemes are implemented: binary encoding in HGA1, and integer representation in HGA2. If binary encoding is used (HGA1), new genetic operators that keep the feasibility of individuals are proposed. Integer representation keeps the individuals feasible by default, so HGA2 uses slightly modified standard genetic operators. In both methods, caching GA technique was integrated with the GFI heuristic to improve computational performance. The algorithms are tested on standard ORLIB p-median instances with up to 900 nodes. The obtained results are also compared with the results of existing methods for solving DOMP in order to assess their merits.     

Acidity of montmorillonite pillared by alumina, zirconia and chromia

Acidic properties of Al-, Zr- and Cr- pillared montmorillonites prepared from Jelšovy Potok bentonite (Central Slovakia) have been investigated using temperature-programmed desorption of ammonia. The number of acid sites varied with different interlayer cations from 0.06 to 0.23 mmol g⁻¹. The character of acid sites was similar in the case of Al- and Zr- forms. It is obvious that the chromium analogue contains fewer acid sites, nevertheless, they seem to be stronger compared to Al- and Zr- pillared montmorillonites.     

A radial-partition fluoroimmunoassay for the detection of Hepatitis B surface antigen with the streptavidin/biotin complex

A sandwich technique based on the very affinity between avidin and biotin is used. Antibodies are covalently bound to glass-fibre on which the antigen is captured. The discs are then treated in sequence with monoclonal antibodies of high selectivity, species-specific anti-IgG (biotin-linked), streptavidin and β-galactosidase, (biotin-linked). The discs are then incubated with the substrate, 4-methylumbelliferyl-β-d-galactopyranoside and the fluorescence is measured in an automatic immunoassay system.     

A fluoroimmunoassay for screeing of hepatitis B surface antigen

A fast, sensitive sandwich fluorimmunoassay for hepatitis B surface antigen (HB_s-ag) is described. Rabbit antibodies to HB_s-ag are covalently bound to the centre of a glass-fiber filter disk. The second antibody is a swine anti-human HB_s-ag conjugated with β-d-galactosidase from E. coli. The substrate is 4-methylumbelliferyl-β-d-galactopyrano-side. The technique is applied with the Stratus system which does the entire test in 8 min. the detection limit is 1 ng ml^?1, and the results correlate well with a radioimmunoassay technique.     

Nearly uniform distribution of edges among k-subgraphs of a graph

We investigate the behavior of the function f = f(n, k, e) defined as the smallest integer with the following property: If in a graph on n vertices, the numbers of edges in any two induced subgraphs on k vertices differ by at most e, then the graph or its complement has at most f edges. One of the results states that . © 1929 John Wiley & Sons, Inc.     

Structural study and magnetic properties of copper(II) thiophene-2-carboxylate with 4-pyridinemethanol and isonicotinamide

The synthesis and characterization of [Cu(5-Me-2-tpc)₂(4-pyme)₂] (I), [Cu(3-Me-2-tpc)₂(4-pyme)₂] (II), [Cu(2-tpc)₂(4-pyme)₂] (III), [Cu(2-tpc)₂(isonia)₂(2-tpcH)] (IV), [Cu(5-Me-2-tpc)₂(isonia)₂(5-Me-2-tpcH)] (V), [Cu₂(2-tpc)₄(4-pyme)₂] (VI), [Cu₂(3-Me-2-tpc)₄(isonia)₂] (VII) (where 2-tpc is 2-thiophenecarboxylate, 3-Me-2-tpc is 3-methyl-2-thiophenecarboxylate, 5-Me-2-tpc is 5-methyl-2-thiophenecarboxylate and 4-pyme is 4-pyridinemethanol and isonia is isonicotinamide) are reported. The complexes under study were characterized by electronic, IR and EPR spectroscopy, magnetic susceptibility over the temperature range and X-ray structure analysis. Structural studies revealed a distorted tetragonal-bipyramidal environment around the copper ion for monomeric complexes I–V. The structure of dimeric complexes VI and VII consists of units of the known paddle-wheel dicopper(II) tetracarboxylates, which are made up of four thiophene-2-carboxylate ions thus bridging the two copper atoms. The complex molecules of all compounds are connected through H-bonds into supramolecular chains or frameworks. The spectral and magnetic properties are discussed with regard to X-ray data.     

Design rules for the large two-photon absorption diketopyrrolopyrrole-based quadrupolar symmetrical chromophores

Two-photon absorption of a series of symmetrical diketopyrrolopyrrole (DPP) derivatives is studied by means of density functional theory applied to second-order response function. Several important issues in modeling are highlighted which must be addressed for a reliable reproduction of the experimental results. A comparison of the theoretical results with the experimental ones indicates that the computed two-photon absorption (TPA) cross sections show a good agreement for the three-state model in case of symmetrical quadrupolar DPP derivatives with donor ending groups. Although the results of TPA cross section observed for the systems with strong electron accepting ending groups seem to be overestimated for the three-state model. At the same time using an algorithm for the direct calculation of the third-order processes by the solving dynamic coupled-perturbed Hartree–Fock equation shows relatively good qualitative results for both donor and acceptor ending groups; however, it was found to be less accurate quantitatively for the already published experimental results. Thus, to obtain a valid overview, supposedly, both methods have to be considered. In general, in the present paper, a strategy toward molecular tailoring of large TPA cross-sectional materials is described, which can be extremely useful tool to predict materials’ properties prior to synthesis and measurements.