bluuebunny/crossref_metadata_2025 huggingface dataset:
Lectures on the functional renormalization group method
Authors: Polonyi Janos
Published: August 2006

These introductory notes are about functional renormalization group equations and some of their applications. It is emphasised that the applicability of this method extends well beyond critical systems, it actually provides us a general purpose algorithm to solve strongly coupled quantum field theories. The renormalization group equation of F. Wegner and A. Houghton is shown to resum the loop-expansion. Another version, due to J. Polchinski, is obtained by the method of collective coordinates and can be used for the resummation of the perturbation series. The genuinely non-perturbative evolution equation is obtained by a manner reminiscent of the Schwinger-Dyson equations. Two variants of this scheme are presented where the scale which determines the order of the successive elimination of the modes is extracted from external and internal spaces. The renormalization of composite operators is discussed briefly as an alternative way to arrive at the renormalization group equation. The scaling laws and fixed points are considered from local and global points of view. Instability induced renormalization and new scaling laws are shown to occur in the symmetry broken phase of the scaler theory. The flattening of the effective potential of a compact variable is demonstrated in case of the sine-Gordon model. Finally, a manifestly gauge invariant evolution equation is given for QED.
Theoretical studies of model thin EuTe films with surface elastic stresses
Authors: Radomska Anna , Balcerzak Tadeusz
Published: August 2006

A simple model for the description of thin EuTe films is proposed. The magnetoelastic interactions at the surface are taken into account. The influence of the elastic stresses on magnetic properties of the film is studied, especially with respect to the possibility of antiferromagnetic/ferromagnetic phase transitions.
Model calculations in reconstructions of measured fields
Authors: Makai Mihály , Orechwa Yuri
Published: August 2006

The state of technological systems, such as reactions in a confined volume, are usually monitored with sensors within as well as outside the volume. To achieve the level of precision required by regulators, these data often need to be supplemented with the solution to a mathematical model of the process. The present work addresses an observed, and until now unexplained, convergence problem in the iterative solution in the application of the finite element method to boundary value problems. We use point group theory to clarify the cause of the non-convergence, and give rule problems. We use the appropriate and consistent orders of approximation on the boundary and within the volume so as to avoid non-convergence.
Homotopy of the classical configuration space for the two-magnon sector of a magnetic Heisenberg ring
Authors: Lulek Barbara , Jakubczyk Dorota
Published: August 2006

A finite Heisenberg magnetic ring with an arbitrary single-node spin and two spin deviations from the ferromagnetic saturation is considered as the system of two Bethe pseudoparticles. The set of all relevant magnetic configurations spans a surface which can be recognised as a Mőbius strip. The dynamics of the system imposes the double twist of all regular orbits of the translation symmetry group.
Observation of magnetic field-induced contraction of fission yeast cells using optical projection microscopy
Authors: Yang Xi , Beckwith Andrew , Miller John , Wood Lowell
Published: August 2006

The charges in live cells interact with or produce electric fields, which results in enormous dielectric responses, flexoelectricity, and related phenomena. Here we report on a contraction of Schizosaccharomyces pombe (fission yeast) cells induced by magnetic fields, as observed using a phase-sensitive projection imaging technique. Unlike electric fields, magnetic fields only act on moving charges. The observed behavior is therefore quite remarkable, and may result from a contractile Lorentz force acting on diamagnetic screening currents. This would indicate extremely high intracellular charge mobilities. Besides, we observed a large electro-optic response from fission yeast cells.
Covering group and graph of discretized volumes
Authors: Makai Mihály , Orechwa Yuri
Published: August 2006

We consider a discretized volume V consisting of finite, congruent and attached copies of a tile t. We find a group L V the orbit of which, when applied to t, is just V. We show the connection between the structural matrixQ in the formal solution of a boundary value problem formulated for volume V and the so called auxiliary matrix of the graph Γv associated with V. We show boundary value problems to be isomorphic if the graphs associated with the volumes are isomorphic, or, if the covering groups are Sunada pairs.
Simulation model for shapiro time delay and light deflection experiments
Authors: Biswas Abhijit , Mani Krishnan
Published: August 2006

The time delay experiment proposed by I.I. Shapiro in 1964 and conducted in the seventies was the most precise experiment of general relativity until that time. Further experimentation has improved the accuracy level of both the time delay and the light deflection experiments. A simulation model is proposed that involves only a simple mass and time transformation factor involving velocity of light. The light deflection and the time delay experiments are numerically simulated using this model that does not use the general relativistic equations. The computed values presented in this paper compare well with recent levels of accuracy of their respective experimental results.
XPS Study of group IA carbonates
Authors: Shchukarev A. , Korolkov D.
Published: August 2006

The results of systematic XPS measurements of all alkali metal carbonates (Li, Na, K, Rb and Cs) are presented. The first set of experiments was performed with “as received” commercial carbonate powders under liquid nitrogen conditions using a precooling procedure. A second set of experiments was performed under similar experimental conditions after a preliminary grinding (mechanical activation) of the carbonates. In addition, Na2CO3
*1H2O, NaHCO3 and KHCO3 powders were studied. It was found that sample pre-cooling allows distinction between hydrocarbonates and carbonate hydrates. Storage in air leads to formation of hydrocarbonates at the surface of Li2CO3 and Na2CO3. This phenomenon being more pronounced in the former. In contrast, K2CO3 forms a hydrate with one H2O molecule. Rb2CO3 and Cs2CO3 have hydrocarbonates as well as hydrates at the surface and this is more pronounced for Cs2CO3. Grinding of the carbonates results in the formation of hydrocarbonates at the surface, the tendency to do so was found to increase down the group IA, namely, K<Rb≪Cs. For the most part, the hydrocarbonates formed were unstable in vacuum even under liquid nitrogen conditions. Chemical trends in C 1s and O 1s binding energies in carbonates and hydrocarbonates of the Group IA are discussed and related to the nature of the anion and alkali cation.
Chemometric study of soil analysis data
Authors: Spanos Th. , Simeonov V. , Tsakovski S. , Thiokas D.
Published: August 2006

The present paper deals with chemometric interpretation of soil analysis data collected from 31 sampling sites in the region of Kavala and Drama, Northern Greece. The determination of 16 different chemical and physicochemical characteristics is principally needed for prognosis of the land treatment and fertilizing. The study carried out indicates that the application of multivariate statistical approaches could reveal new and specific information about sampling sites. It has been found that they could be divided into four general patterns: pattern 1 contains dominantly inorganic and alkaline soil samples from semi-mountainous regions in close proximity to the seacoast; pattern 2 indicates the same soil sample type and regional location as pattern 1 but is far from the coastal line; pattern 3 includes samples from sites from the plains with organic and alkaline soils with close proximity to the coast; pattern 4 resembles pattern 3 as soil type but involves samples from sites far from the shore. Further, six latent factors were identified, conditionally named “structural”, “acidic”, “nutritional”, “salt”, “microcomponents” and “organic”. Finally, an apportioning procedure was carried out to find the source contributions in the measured analytical values. In this way the routine estimation of the soil quality could be improved.
Multilayer mirror systems to form hard X-ray beams
Authors: Akhsakhalyan Anton , Akhsakhlyan Aram , Kharitonov Alexander , Kluenkov Eugenie , Murav’ev Vladimir , Salashchenko Nikolay
Published: August 2006

This paper is an overview of the research activities carried out in the past five years at the Institute for Physics of Microstructures RAS and “X-ray” Company towards the manufacture of multilayer mirror systems capable of forming X-ray beams in the subnanometer range of wavelengths. The systems fabrication technology is presented, including techniques for producing supersmooth surfaces of specified shape, methods of graded multilayer structure deposition on such surfaces, and the principles of designing optimal mirror parameters. The characteristics of a quadrelliptical reflector—a novel high light-gathering power four-corner focusing system—are reported.
The Hurwitz determinants and the signatures of irreducible representations of simple real Lie algebras
Authors: Rudy Alexander
Published: August 2006

The paper deals with the real classical Lie algebras and their finite dimensional irreducible representations. Signature formulae for Hermitian forms invariant relative to these representations are considered. It is possible to associate with the irreducible representation a Hurwitz matrix of special kind. So the calculation of the signatures is reduced to the calculation of Hurwitz determinants. Hence it is possible to use the Routh algorithm for the calculation.
Bivariant Chern classes for morphisms with nonsingular target varieties
Authors: Yokura Shoji
Published: August 2006

W. Fulton and R. MacPherson posed the problem of unique existence of a bivariant Chern class—a Grothendieck transformation from the bivariant theory F of constructible functions to the bivariant homology theory H. J.-P. Brasselet proved the existence of a bivariant Chern class in the category of embeddable analytic varieties with cellular morphisms. In general however, the problem of uniqueness is still unresolved. In this paper we show that for morphisms having nonsingular target varieties there exists another bivariant theory
$$\tilde {\mathbb{F}}$$
of constructible functions and a unique bivariant Chern class γ:
$$\tilde {\mathbb{F}} \to {\mathbb{H}}$$
.
Some alternating sums of Lucas numbers
Authors: Čerin Zvonko
Published: August 2006

We consider alternating sums of squares of odd and even terms of the Lucas sequence and alternating sums of their products. These alternating sums have nice representations as products of appropriate Fibonacci and Lucas numbers.
Quaternionic geometry of matroids
Authors: Hausel Tamás
Published: August 2006

Building on a recent paper [8], here we argue that the combinatorics of matroids are intimately related to the geometry and topology of toric hyperkähler varieties. We show that just like toric varieties occupy a central role in Stanley’s proof for the necessity of McMullen’s conjecture (or g-inequalities) about the classification of face vectors of simplicial polytopes, the topology of toric hyperkähler varieties leads to new restrictions on face vectors of matroid complexes. Namely in this paper we will give two proofs that the injectivity part of the Hard Lefschetz theorem survives for toric hyperkähler varieties. We explain how this implies the g-inequalities for rationally representable matroids. We show how the geometrical intuition in the first proof, coupled with results of Chari [3], leads to a proof of the g-inequalities for general matroid complexes, which is a recent result of Swartz [20]. The geometrical idea in the second proof will show that a pure O-sequence should satisfy the g-inequalities, thus showing that our result is in fact a consequence of a long-standing conjecture of Stanley.
Bolzano’s intermediate-value theorem for quasi-holomorphic maps
Authors: Bayoumi Aboubakr
Published: August 2006

We extend Bolzano’s intermediate-value theorem to quasi-holomorphic maps of the space of continuous linear functionals from l
p into the scalar field, (0< p<1). This space is isomorphic to l
∞.
Magnetic field and currents in HTSC films
Authors: Gaikovich K. , Nozdrin Yu. , Zhilin A.
Published: August 2006

Magnetic field measurements above type-II superconductor films in a remanent magnetization state have been used to determine two dimensional surface current distributions. Using the Biot-Savart law for the surface current density, integral equations (of 2-D convolution type) for two components of current have been obtained. These equations have been solved by employing Tikhonov's method of generalized discrepancy, and the surface current pattern in superconductors as well as the magnetic field distribution on the film surface have been obtained. Current peculiarities related to various kinds of inhomogeneities, specific character of the film form, and a laser pulse effect have been observed. In particular, it was discovered that a laser pulse can signficantly redistribute the film currents without changing the total number of current vortices in the film.
Electron spectral density of the half-filled Hubbard model in the atomic limit at finite temperature
Authors: Ovchinnikov Sergei , Shneyder Elena
Published: August 2006

We have calculated the spectral function and density of states of halffilled two-dimensional Hubbard model in the Hubbard-I approximation assuming an antiferromagnetic long range order at low temperature and compared results to the QMC data. It occurs that calculated functions are in a qualitative agreement with the QMC one. We have also shown that Neel ordered state dispersion has the similar form to the spin density wave one.
Application of the Volterra filter in experimental diffraction data processing
Authors: Jurečka Stanislav , Jurečková Mária
Published: August 2006

The effective signal in x-ray diffraction analysis of material properties often contains high frequency (noise) and low frequency (trend) components as additive parts. It is necessary to extract the effective signal from the noise to ensure high quality of signal processing. Digital filters of Volterra type are proposed for filtering purposes and a comparison of Volterra filtration implemented on x-ray diffraction data versus results from a set of other digital filters is given.
Steady-state analytical solutions for the lattice boltzmann equation
Authors: Házi Gábor
Published: August 2006

A general class of analytical solutions of the lattice Boltzmann equation is derived for two-dimensional, steady-state unidirectional flows. A subset of the solutions that verifies the corresponding Navier-Stokes equations is given. It is pointed out that this class includes, e.g., the Couette and the Poiseuille flow but not, e.g., the basic Kolmogorov flow. For steady-state non-unidirectional flows, first and second order solutions of the lattice Boltzmann equation are derived. Practical consequences of the analysis are mentioned. Differences between the technique applied here and those used in some earlier works are emphasized.
Formation and dynamics of Saturn and its disk simulated by using a new N-body model
Authors: Pavlov A. , Pavlova Y.
Published: August 2006

The formation of Saturn and its disk is simulated using a new N-body self-gravitational model. It is demonstrated that the formation of the disk and the planet is the result of gravitational contraction of a slowly rotated particle cloud that have a shape of slightly deformed sphere. The sphere was flattened by a coefficient of 0.8 along the axis of rotation. During the gravitational contraction, the major part of the cloud transformed into a planet and a minor part transformed into a disk. The thin structured disk is a result of the electromagnetic interaction in which the magnetic forces acting on charged particles of the cloud originate in the core of the planet. The simulation program gives such parameters of Saturn as the escape velocity of about 35 km/s at the surface, density, rotational velocities of the rings and temperature distribution.
Positron annihilation study for cadmium (electronic structure and enhancement effect)
Authors: Hamid A.
Published: August 2006

The three dimensional electron density in momentum space ρ(p) and in wave vector space n(k) was reconstructed for cadmium (Cd). The measurements were performed using the two dimensional angular correlation of annihilation radiation (2D-ACAR) technique. Enhanced contributions in the spectra were observed around 5.5 mrad, discussed in terms of a Kahana-like enhancement effect. From another viewpoint, Fermi radii were analyzed in the (λM K), (ALM) and (AHK) planes, and they showed a maximum deviation of about 4% from the free electron Fermi radius. Moreover, comparisons to a radio-frequency size effect (RFSE) experiment and theoretical band structure calculations (using augmented plane wave (APW), linear combination of atomic orbital (LCAO) and linear muffin tin orbital (LMTO) methods) were examined. The results showed a qualitative agreement with both APW and LCAO calculations. However, a favorable agreement with the APW method was determined via Fermi surface dimensions. The differences of bands' occupation of n(k) between the current work and the APW method were argued in view of positron wave function in Cd.
On regular polynomial endomorphisms of ℂ2 without bounded critical orbitswithout bounded critical orbits
Authors: Stawiska Małgorzata
Published: August 2006

We study conditions involving the critical set of a regular polynomial endomorphism f∶ℂ2↦ℂ2 under which all complete external rays from infinity for f have well defined endpoints.
Rank 4 vector bundles on the quintic threefold
Authors: Madonna Carlo
Published: August 2006

By the results of the author and Chiantini in [3], on a general quintic threefold X⊂P
4 the minimum integer p for which there exists a positive dimensional family of irreducible rank p vector bundles on X without intermediate cohomology is at least three. In this paper we show that p≤4, by constructing series of positive dimensional families of rank 4 vector bundles on X without intermediate cohomology. The general member of such family is an indecomposable bundle from the extension class Ext
1 (E, F), for a suitable choice of the rank 2 ACM bundles E and F on X. The existence of such bundles of rank p=3 remains under question.
Generalized interval exchanges and the 2–3 conjecture
Authors: Friedland Shmuel , Weiss Benjamin
Published: August 2006

We introduce the notion of a generalized interval exchange
$$\phi _\mathcal{A} $$
induced by a measurable k-partition
$$\mathcal{A} = \left\{ {A_1 ,...,A_k } \right\}$$
of [0,1).
$$\phi _\mathcal{A} $$
can be viewed as the corresponding restriction of a nondecreasing function
$$f_\mathcal{A} $$
on ℝ with
$$f_\mathcal{A} (0) = 0, f_\mathcal{A} (k) = 1$$
. A is called λ-dense if λ(A
i∩(a, b))>0 for each i and any 0≤ a< b≤1. We show that the 2–3 Furstenberg conjecture is invalid if and only if there are 2 and 3 λ-dense partitions A and B of [0,1), such that
$$f_\mathcal{A} \circ f_\mathcal{B} = f_\mathcal{B} \circ f_\mathcal{A} $$
. We give necessary and sufficient conditions for this equality to hold. We show that for each integer m≥2, such that 3∤2m+1, there exist 2 and 3 non λ-dense partitions A and B of [0,1), corresponding to the interval exchanges on 2m intervals, for which
$$f_\mathcal{A} $$
and
$$f_\mathcal{B} $$
commute.
On the riemann zeta-function and the divisor problem
Authors: Ivić Aleksandar
Published: August 2006

Let Δ(x) denote the error term in the Dirichlet divisor problem, and E(T) the error term in the asymptotic formula for the mean square of
$$\left| {\varsigma \left( {\tfrac{1}{2} + it} \right)} \right|$$
. If
$$E^* \left( t \right) = E\left( t \right) - 2\pi \Delta ^* \left( {t / 2\pi } \right)$$
with
$$\Delta ^* \left( x \right) = - \Delta \left( x \right) + 2\Delta \left( {2x} \right) - \tfrac{1}{2}\Delta \left( {4x} \right)$$
, then we obtain
$$\int_0^T {\left( {E^* \left( t \right)} \right)^4 dt \ll _e T^{16/9 + \varepsilon } } $$
. We also show how our method of proof yields the bound
$$\sum\limits_{r = 1}^R {\left( {\int_{tr - G}^{tr + G} {\left| {\varsigma \left( {\tfrac{1}{2} + it} \right)} \right|^2 dt} } \right)^4 \ll _e T^{2 + e} G^{ - 2} + RG^4 T^\varepsilon } $$
, where T
1/5+ε≤G≪T, T<t
1<...<t
R≤2T, t
r
+1−t
r≥5G (r=1, ..., R−1).
Nondegenerate cohomology pairing for transitive Lie algebroids, characterization
Authors: Kubarski Jan , Mishchenko Alexandr
Published: August 2006

The Evens-Lu-Weinstein representation (Q
A, D) for a Lie algebroid A on a manifold M is studied in the transitive case. To consider at the same time non-oriented manifolds as well, this representation is slightly modified to (Q
Aor, Dor) by tensoring by orientation flat line bundle, Q
Aor=QA⊗or (M) and D
or=D⊗∂Aor. It is shown that the induced cohomology pairing is nondegenerate and that the representation (Q
Aor, Dor) is the unique (up to isomorphy) line representation for which the top group of compactly supported cohomology is nontrivial. In the case of trivial Lie algebroid A=TM the theorem reduce to the following: the orientation flat bundle (or (M), ∂Aor) is the unique (up to isomorphy) flat line bundle (ξ, ∇) for which the twisted de Rham complex of compactly supported differential forms on M with values in ξ possesses the nontrivial cohomology group in the top dimension. Finally it is obtained the characterization of transitive Lie algebroids for which the Lie algebroid cohomology with trivial coefficients (or with coefficients in the orientation flat line bundle) gives Poincaré duality. In proofs of these theorems for Lie algebroids it is used the Hochschild-Serre spectral sequence and it is shown the general fact concerning pairings between graded filtered differential ℝ-vector spaces: assuming that the second terms live in the finite rectangular, nondegeneration of the pairing for the second terms (which can be infinite dimensional) implies the same for cohomology spaces.
A geometric theory of harmonic and semi-conformal maps
Authors: Kock Anders
Published: August 2006

We describe for any Riemannian manifold M a certain scheme M
L, lying in between the first and second neighbourhood of the diagonal of M. Semi-conformal maps between Riemannian manifolds are then analyzed as those maps that preserve M
L; harmonic maps are analyzed as those that preserve the (Levi-Civita-) mirror image formation inside M
L.
On higher order geometry on anchored vector bundles
Authors: Popescu Paul
Published: August 2006

Some geometric objects of higher order concerning extensions, semi-sprays, connections and Lagrange metrics are constructed using an anchored vector bundle.
Determination of inorganic arsenic species As(III) and As(V) by high performance liquid chromatography with hydride generation atomic absorption spectrometry detection
Authors: Niedzielski P. , Siepak M. , Novotny K.
Published: August 2006

The paper presents the principles and advantages of a technique combining high performance liquid chromatography and hydride generation atomic absorption spectrometry (HPLC-HGAAS) applied to speciation analysis of inorganic species of arsenic As(III) and As(V) in ground water samples. With separation of the arsenic species on an ion-exchange column in the chromatographic system and their detection by the hydride generation atomic absorption spectrometry, the separation of the analytical signals of the arsenic species was excellent at the limits of determination of 1.5 ng/ml As(III) and 2.2 ng/ml As(V) and RSD of 4.3% and 7.8% for the concentration of 25 ng/ml. The hyphenated technique has been applied for determination of arsenic in polluted ground water in the course of the study on migration of micropollutants. For total arsenic concentration two independent methods: HGICP-OES and HGAAS were used for comparison of results of real samples analysis.
Evaluation of 13C NMR spectra of cyclopropenyl and cyclopropyl acetylenes by theoretical calculations
Authors: Ananikov Valentine
Published: August 2006

A convenient methodology was developed for a very accurate calculation of 13C NMR chemical shifts of the title compounds. GIAO calculations with density functional methods (B3LYP, B3PW91, PBE1PBE) and 6-311+G(2d,p) basis set predict experimental chemical shifts of 3-ethynylcyclopropene (1), 1-ethynylcyclopropane (2) and 1,1-diethynylcyclopropane (3) with high accuracy of 1–2 ppm. The present article describes in detail the effect of geometry choice, density functional method, basis set and effect of solvent on the accuracy of GIAO calculations of 13C NMR chemical shifts. In addition, the particular dependencies of 13C chemical shifts on the geometry of cyclopropane ring were investigated.
Synthesis of aldehydes and ketones by the dehydrogenation of alcohols in the presence of a Raney nickel/aluminium isopropoxide/alumina catalyst
Authors: Tarta Ilie , Silberg Ioan , Vlassa Mircea , Oprean Ioan
Published: August 2006

The synthesis of aldehydes and ketones by the dehydrogenation of allylic and secondary alcohols using a Raney-Ni-Al(i-OPr)3-Al2O3 catalyst without hydrogen acceptors is presented.
The synthesis and the structure elucidation of N,O-diacetyl derivative of cyclic 3-hydroxymelatonin
Authors: Siwicka Aleksandra , Reiter Russel , Tian Dun , Wojtasiewicz Krystyna , Leniewski Andrezej , Maurin Jan , Błachut Dariusz , Czarnocki Zbigniew
Published: August 2006

Melatonin was subjected to an oxidation to give 3-hydroxymelatonin. All spectroscopic data for this compound were collected. Ab initio calculations for both possible configurations were performed. X-ray data on N,O-diacetyl derivative of 3-hydroxymelatonin allowed the unambigous structure determination.
Crystal structure and spectral characterization of dimethylthallium (III) complexes with 2-mercaptonicotinic acid and esters
Authors: Toma Monica , Sánchez Agustín , García-Tasende María , Casas José , Sordo José , Castellano Eduardo , Ellena Javier
Published: August 2006

Synthesis, spectral properties and crystal structure of dimethylthallium(III) complexes with 2-mercaptonicotinic acid (2mna), 2-mercapto-methyl-nicotinate (2mmn), 2-mercapto-ethyl-nicotinate (2men) and 2-mercapto-isopropyl-nicotinate (2min) are reported. The compounds were characterized using IR, multinuclear NMR (1H,13C,205Tl) and mass spectrometry (electrospray, ES-API). The molecular structures of [TlMe2(2mna)]·H2O, (1), [TlMe2(2mmn)], (2), [TlMe2(2men)], (3) and [TlMe2(2min)], (4) were determined by the single-crystal X-ray diffraction. In 1, the monodeprotonate O,S-bidentate ligand chelates one dimethylthallium (III) unit and simultaneously bridges (O and S) between two of these organometallic units. The Tl-O1′ and Tl-S″ interactions are leading to polymeric chain linked in a three-dimensional network by the hydrogen bonds formed between the water molecule and the oxygen O (2) atom of the acid. The thallium atom is in a distorted octahedral environment with a [TlC2O2S2] kernel. Compounds 2, 3 and 4 are similar, in all the cases already mentioned the ligand is NH deprotonated and is strongly coordinated to two dimethylthallium (III) units through the N and S atoms. Two additional weak interactions with the O and S atoms lead to a [TlC2NOS2] kernel for the metal atom, in which the coordination polyhedron is a very distorted octahedron with the methyl groups occupying the apical positions.
Dithiobiuretes in reactions with electrophilic acetylenes. New derivatives of 1,3,5-dithiazines,-thiadiazines and-triazines as the products of competing reactions of nucleophilic cycloaddition
Authors: Glotova Tatýana , Protsuk Nadezhda , Albanov Alexander , Lopyrev Valentin , Dolgushin Gennadii
Published: August 2006

The nucleophilic addition of 2,4-dithiobiurete, 1- and 1,4-substituted 2,4-dithiobiuretes (2 a-e) with benzoylacetylene (1) has been studied. 2-(Benzoylmethyl)-4-(R1-imino)-6-(R2-imino)dihydro-4H-1,3,5-dithiazinium perchlorates (3 a-e) are obtained in glacial acetic acid (AcOH) in the presence of equimolar quantities of HClO4. The reaction of benzoylacetylene with 1,5-diphenyl-2,4-dithiobiurete in either of MeOH, C6H6, or MeCN solvents proceeds non-selectively to give a mixture of products such as 2-(benzoylmethyl)-4,6-di(phenylimino)dihydro-4H-1,3,5-dithiazine (5), 2-(benzoylmethyl)-4-(β-benzoylvinyl)thio-3-phenyl-6-(phenylimino)-3,6-dihydro-2H-1,3,5-thiadiazine (8), 2-(benzoylmethyl)-1,3-diphenylhexahydro-1,3,5-triazine-4,6-dithione (7) and N-(β-benzoylvinyl)-N-phenylthioureas (6).
Synthesis of 4-aryloxy-7-nitrobenzofurazan derivatives from 4-chloro-7-nitrobenzofurazan and various phenoxide anions (including pharmaceuticals) in the presence of crown ethers
Authors: Bem Marioara , Caproiu Miron , Stoicescu Dan , Constantinescu Titus , Balaban Alexandru
Published: August 2006

4-Chloro-7-nitrobenzofurazan reacts by nucleophilic substitution with phenoxide anions derived from estriol (2c), ethynylestradiol (2d), phenol (3e), guaiacol (3f), 2,6-dimethoxyphenol (3g), eugenol (3h), isoeugenol (3i), the cytostatic Etoposide (4), and Reichardt’s betaine (5) in the presence of crown ethers affording the corresponding 4-aryloxy-7-nitrobenzofurazan derivatives 6c, 6d, 7e-7i, 8, and 9. The structure of these compounds was confirmed by NMR spectra. Hydrophobicity/hydrophilicity parameters were investigated by reverse phase thin-layer chromatography.
Preliminary observations on the copolymerisation of acceptor monomer:donor monomer systems under microwave irradiation
Authors: Fellows Christopher
Published: August 2006

The mechanistic rationalisation of specific ‘microwave effects’ previously reported in a range of chemical reactions suggests that they may be observable in the freeradical copolymerisation of comonomer pairs capable of forming donor-acceptor complexes. Polymerisation under microwave irradiation is carried out for several comonomer pairs with weak donor-acceptor interactions, and no acceleration in rate or change in degree of alternation attributable to changes in propagation are observed. An increase in reaction rate of 150–200 % is observed for all systems, with trends in molecular weight suggesting this was due to an increase in radical flux. This is consistent with earlier reports of rate enhancement for free-radical polymerisations using the initiator 2,2′-azobis-isobutyronitrile, and it is proposed that microwave irradiation may reduce the amount of geminate radical recombination.
Synthesis, characterization and structure of the Bis(methyl-cyclopentadienyl)vanadium(IV) carboxylates
Authors: Vinklarek Jaromír , Honzíĉek Jan , Císařová Ivana , Pavliŝta Martin , Holubová Jana
Published: August 2006

The 1,1’-dimethylvanadocene dichloride ((C5H4CH3)2VCl2) reacts in aqueous solution with various carboxylic acids giving two different types of complexes. The 1,1’-dimethylvanadocene complexes of monocarboxylic acids (C5H4CH3)2V(OOCR)2 (R=H,CCl3, CF3, C6H5) contain two monodentate carboxylic ligands, whereas oxalic and malonic acids act as chelate compounds of the formula (C5H4CH3)2V(OOC-A-COO) (A=−, CH2). The structure of the (C5H4CH3)2 V(OOCCF3)2 complex was determined by single crystal X-ray diffraction analysis. The isotropic and anisotropic EPR spectra of all the complexes prepared were recorded. The obtained EPR parameter values were found to be in agreement with proposed structures.
Moravia: A 3-, 8-connected cubic structural pattern in space group Pm3m
Authors: Bucknum Michael , Castro Eduardo
Published: August 2006

This paper describes the crystal structure of a novel, hypothetical 3-,8-connected cubic structural pattern with the binary stoichiometry A3B8. The novel pattern lies in space group Pm3m, number 221. It possesses the Wells point symbol (4468812)3(43)8 and has the Wellsean Schläfli index (6, 4.3636). It is derived from the Andreini space filling arrangement of octahedra and cuboctahedra by replacing the areas where there are face-sharing of the polyhedra with the inscription of 3-connected, trigonal planar vertices, and retaining the points where the polyhedra share vertices in cube coordination. The structure-type could be representative of a binary metal oxide in which the metal cation attains a relatively high oxidation state of 51/3+. Possible metal oxide models for the structure-type include M3O8 (where M is a Group 6 or 7 elements).
Aromatic λ3 heterocycles XIV. Fosfinine-ether macrocyclesheterocycles XIV. Fosfinine-ether macrocycles
Authors: Pacureanu Liliana , Mracec Mircea
Published: August 2006

The geometry and electronic structure of several phosphinine-ether macrocycles were investigated at semiempirical level. The calculated geometries are in good agreement with experimental data. Compared to phosphinine, the coordinative abilities of phosphinineether macrocycles based on energy considerations suggest a little lowered π acceptor character, while π donor character is improved. The molecular environment causes a significant mixing of phosphinine and phenyl substituent π levels. The geometry and electronic properties of phosphinine-ether macrocycles can provide significant host coordination properties for guest species.
Thermodynamic model of crystallization and melting of small particles
Authors: Samsonov Vladimir , Malkov Oleg
Published: August 2006

The size dependence of the nanocrystal melting temperature has been investigated based on a nonequilibrium thermodynamics approach. An expression has been derived for the melting temperature that, contrary to the classical Tomson formula, takes into account the metastable character of the crystal nucleus-melt shell equilibrium. Quantitative estimations have been carried out for small spherical particles of aluminum, tin, and lead.
Glass-forming ability and thermal stability of Fe62Nb8−xZrxB30 and Fe72Zr8B20 amorphous alloys?
Authors: Shapaan M. , Lábár J. , Varga L. , Lendvai J.
Published: August 2006

Glass-forming ability (GFA) and thermal stability of Fe62Nb8B30, Fe62Nb6Zr2B30 and Fe72Zr8B20 at % amorphous alloys were investigated by calorimetric (DSC and DTA) measurements. The crystallization kinetics was studied by DSC in the mode of continuous versus linear heating and it was found that both the glass transition temperature, Tg, and the crystallization peak temperature, Tp, display strong dependence on the heating rate. The partial replacement of Nb by Zr leads to lower Tg and Tx temperatures and causes a decrease of the supercooled liquid region. JMA analysis of isothermal transformation data measured between Tg and Tx suggests that the crystallization of the Fe62Nb8B30 and Fe62Nb6Zr2B30 amorphous alloys take place by three-dimensional growth with constant nucleation rate. Nb enhances the precipitation of the metastable Fe23B6 phase and stabilizes it up to the third crystallization stage. Zr addition increases the lattice constant of Fe23B6 and, at the same time, decreases the grain size.
Critical fields of a superconducting cylinder
Authors: Zharkov G.
Published: August 2006

The self-consistent solutions of the nonlinear Ginzburg-Landau equations, which describe the behavior of a superconducting mesoscopic cylinder in an axial magnetic field H (provided there are no vortices inside the cylinder), are studied. Different, vortex-free states (M-, e-, d-, p-), which exist in a superconducting cylinder, are described. The critical fields (H
1, H
2, H
p, H
i, H
r), at which the first or second order phase transitions between different states of the cylinder occur, are found as functions of the cylinder radius R and the GL-parameter
$$\kappa $$
. The boundary
$$\kappa _c (R)$$
, which divides the regions of the first and second order (s, n)-transitions in the icreasing field, is found. It is found that at R→∞ the critical value, is
$$\kappa _c = 0.93$$
. The hysteresis phenomena, which appear when the cylinder passes from the normal to superconducting state in the decreasing field, are described. The connection between the self-consistent results and the linearized theory is discussed. It is shown that in the limiting case
$$\kappa \to {1 \mathord{\left/ {\vphantom {1 {\sqrt 2 }}} \right. \kern-\nulldelimiterspace} {\sqrt 2 }}$$
and R ≫ λ (λ is the London penetration length) the self-consistent solution (which correponds to the socalled metastable p-state) coincides with the analitic solution found from the degenerate Bogomolnyi equations. The reason for the existence of two critical GL-parameters
$$\kappa _0 = 0.707$$
and
$$\kappa _0 = 0.93$$
in, bulk superconductors is discussed.
Higher harmonics in the voltage on a superconducting wire carrying AC electrical current
Authors: Tebano Riccardo , Gömöry Fedor
Published: August 2006

The problem of determining the harmonic content in the voltage that appears on a superconducting wire carrying cosine-like AC current was resolved theoretically, using two approaches. First, the Fourier components of the voltage spectrum were found by numerical integration. Importance of individual terms was established, leading to two conclusions: a) it is the cosine component of the 3rd harmonic that represents the bulk of harmonic distortion, b) for the practical purposes it is sufficient to consider higher harmonics with n ≤ 7. Then, the analytical formulas were derived. While for the sine components a general expression containing an infinite series was found, closed-form formulas were derived for the cosine components of the harmonics 1, 3, 5, 7. Consequences of the results to the experimental technique used to study the AC transport properties of superconductors are discussed.
The characteristic X-ray spectra of free atoms of metals
Authors: Antsiferov P.
Published: August 2006

The article presents the results of a study of characteristic X-ray spectra of free atoms by means of a new simple technique. A pulsed electron beam was used for evaporation and to create inner-shell vacancies in free atoms of metals. The spectra were obtained with the help of an X-ray monochromator which allowed precise comparison between the free-atoms spectra and corresponding solid-state spectra. The shifts of the peaks were measured and found to be in the range Δλ/λ≈10−5–10−4. The K-, L- and M-series spectra were studied. A number of the free-atoms spectra revealed structure which was not resolved in the solid-state spectra and which is of interest for atomic structure calculation applications. This electron beam technique for the investigation of X-ray characteristic spectra of free atoms can be used for the refinement of X-ray wavelength standards.
Nematic ordering problem as the polymer problem of the excluded volume
Authors: Yakunin A.
Published: August 2006

Based on a solution of the polymer excluded volume problem, a technique is proposed to estimate some parameters at the isotropic-nematic liquid crystal phase transition (the product of the volume fraction of hard sticks and the ratio of the stick length, L, to its diameter, D; the maximum value of this ratio at which one cannot regard the stick as hard). The critical exponents are estimated. The transition of a swelling polymer coil to ideal is revealed as the polymerization degree of a macromolecule increases. The entanglement concentration obtained agrees with experimental data for polymers with flexible chains. The number of monomers between neighbor entanglements is assumed to be the ratio L/D. A comparison of the theory with other ones and recent experimental data is made.
On quantum iterated function systems
Authors: Jadczyk Arkadiusz
Published: August 2006

A Quantum Iterated Function System on a complex projective space is defined through a family of linear operators on a complex Hilbert space. The operators define both the maps and their probabilities by one algebraic formula. Examples with conformal maps (relativistic boosts) on the Bloch sphere are discussed.
Leptonic constant of the pseudoscalar B c meson
Authors: Kiselev Valery
Published: August 2006

We calculate the leptonic constant for the pseudoscalar ground state of the B c meson in the framework of a QCD-motivated potential model taking into account the two-loop anomalous dimension for the heavy quark current in nonrelativistic QCD as matched with full QCD.
Nonlinear dynamics of mechanical system with external excitation
Authors: Ryczek Bogusław
Published: August 2006

This paper attends to the problem of vibration of a self-excited mechanical system with a relatively complicated, history dependent dry friction model. The experimentally identified friction model allows description of various cases of stationary and transient motion. The system is composed of a lumped mass that interacts with a belt by means of dry friction. The system is additionally subjected to an external harmonic excitation through elastic element. The main objective of the experimental research has been focused on the analysis of the system behaviour for various values of the excitation frequency. This paper includes also computer simulation of the vibration of the considered system and comparison between the results of experimental and theoretical analysis. The comparison enables the assumed friction model for steel-polyester pair to be verified. It was another goal of the investigations.
Hochschild Cohomology of skew group rings and invariants
Authors: Marcos E. , Martínez-Villa R. , Martins Ma.
Published: August 2006

Let A be a k-algebra and G be a group acting on A. We show that G also acts on the Hochschild cohomology algebra HH
⊙
(A) and that there is a monomorphism of rings HH
⊙
(A)
G→HH
⊙
(A[G]). That allows us to show the existence of a monomorphism from HH
⊙
(Ã)
G into HH
⊙
(A), where Ã is a Galois covering with group G.
Toxicological evaluation of exposed SPMD membranes
Authors: Kočí Vladimír , Mlejnek Martin , Kochánková Lucie
Published: August 2006

This article is focused on bioassay evaluation of exposed SPMDs. Toxicity testing of SPMD extract is a suitable complementary parameter to chemical analysis. Vtox as an integrative parameter describing toxic properties of extract from membrane and thus a level of contamination of assessed ambient is presented here. Two examples of practical use of Vtox is demonstrated: a course of toxicity throw wastewater treatment plant with industrial inlets and increase of toxicity in surface water body caused by leakages of POPs from industrial plant.
Modeling and simulation of free radical polymerization of styrene under semibatch reactor conditions
Authors: Curteanu Silvia
Published: August 2006

The first part of this approach is concerned with the elaboration of a radical polymerization model of styrenne, based on a kinetic diagram that includes chemical and thermal initiation, propagation, termination by recombination and chain transfer to the monomer. Furthermore, volume contraction during polymerization is considered, as well as the gel and glass effects. The mathematical formalism that describes the model in terms of moments is explored in detail. The model was then used to predict the changes in monomer conversion and molecular weight after intermediate addition of initiator and monomer. The results of this operation are dependent on the conditions of the reaction mass, quantity, and moment of substance addition. Therefore, the simulations were performed at different times with respect to the gel effect; before, during and after this phenomenon, and also with respect to different temperatures and initiators. Increasing the initiator concentration before the gel effect leads to an earlier appearance of the phenomenon and to a decrease in molecular weight. The ratio
$$\bar M_w /\bar M_n $$
reveals a polydispersity index smaller for the intermediate addition of initiator. No significant changes take place during or after the gel effect. If along with the initiator, unreacted monomver (used to dissolve the initiator) enters the reactor, a small dip in conversion is observed. The general conclusion of this paper reveals the intermediate addition of initiator as a method to control polymer properties and to prevent the “dead-end” polymerization of styrene.
A study of sample mineralization methods for arsenic analysis of blood and urine by hydride generation and graphite furnace atomic absorption spectrometry
Authors: Sysalova Jirina , Spevackova Vera
Published: August 2006

Mineralization procedures for blood and urine suitable for the determination of arsenic by Hydride Generation Atomic Absorption Spectrometry (HGAAS) are studied on model samples, and the results are utilized in biological monitoring investigations. The objective of this work is to obtain good total As recoveries for both matrices regardless of added As species (As(III), As(V), DMA, MMA, AsB, or AsC). Prior to the HGAAS analyses, preparation procedures were controlled under optimised conditions by graphite furnace atomic absorption spectrometry (GFAAS). Two preparation procedures for urine give As recoveries close to 100% by HGAAS: a) dry ashing at 420°C with Mg(NO3)2 on a hot plate, and b) microwave oven decomposition with (NH4)2S2O8. For blood samples, As recoveries by HGAAS range between 95 and 108% for all species when using dry ashing after a pretreatment of samples with HNO3 and H2O2 in a microwave oven. Wet digestion with (NH4)2S2O8 in a microwave oven gives recoveries very near 100% for Asinorg. and MMA. For other As species in spiked blood samples, recoveries of less than 20% As are found. Precision and detection limits obtained by both techniques are evaluated as well. For arsenic concentrations of 20 μg dm−3 or more in blood and urine, a chemical modifier is recommended for GFAAS analysis; it may or may not be proceeded by a mineralization step. For low As levels encountered in the unexposed population, the HGAAS technique provides reliable results only if a very complete mineralization procedure is used.
Simple synthesis of 3-acyl-5-alkyl(aryl)isoxazoles from terminal alkynes and nitrates of alkaline metals or ammonium
Authors: Rogachev Victor , Filimonov Victor , Kulmanakova Julya , Yusubov Mehman , Bender Wolfgang
Published: August 2006

A simple and general synthesis of 3-acyl-5-alkyl(aryl)isoxazoles by reaction of terminal alkynes with nitrates in acetic acid in the presence of SO3 or alkaline salts is described.
New transformation of cycloalkanone acetals by peracids α,ω-dicarboxylic acids synthesis
Authors: Terent'ev Alexander , Chodykin Sergey
Published: August 2006

A new process of oxidation of cycloalkanone acetals under the action of in situ generated performic acid has been found. The main products of the reaction are α, ω-dicarboxylic acids obtained with the yield up to 77% depending on the size of acetals ring. The process has been explored and optimized on the example of the dodecanedioic acid synthesis (a valuable industrial product).
Dehydrogenation studies of dihydronicotinamide adenine dinucleotide (NADH) with methylene blue in the presence of the copper hexcyanoferrate(II) complex and light
Authors: Tewari Brij
Published: August 2006

The effects of copper ferrocyanide and light on the dehydrogenation rate of NADH by methylene blue is studied. The results suggest that the dehydrogenation rate of NADH with methylene blue is enhanced by copper ferrocyanide. Light also affects the reaction rate.