bluuebunny/crossref_metadata_2025 huggingface dataset:
Aerogel nanoscale magnesium oxides as a destructive sorbent for toxic chemical agents
Authors: Štengl Vaclav , Bakardjieva Snejana , Maříková Monika , Šubrt Jan , Opluštil František , Olšanská Marcela
Published: August 2006

An autoclave hypercritical drying procedure has been used to prepare precursors of MgO from Mg(OCH3)2. This material was prepared with a specific surface area of 1200 m2
g
1. The dehydrated materials consisted of much smaller crystallites than conventionally prepared MgO and were free of OCH3 groups. The precursors and samples of magnesium oxide were taken for experimental evaluation of their reactivity with mustard. The largest percentage of the conversion mustard into non-toxic products after the elapse of the reaction was 77%.
Efficiency assessment of wastewater treatment plant based on SPMD sampling
Authors: Kočí Vladimír , Ocelka Tomáš , Mlejnek Martin , Grabic Roman
Published: August 2006

The efficiency of treatment processes forboth municipal and industrial wastewater (treatment plant-Ostrava, Czech Republic) focused on persistent organic pollutants (POPs) was assessed. Semipermeable membrane devices (SPMDs) as a sampling system were applied. Exposed SPMDs were analyzed both for chemical contaminants of POPs and toxicity response. The chemical analyses of PAHs were made by HPLC-FLD, PCDD/Fs and PCBs were analysed by GC/MS/MS on GCQ or PolarisQ (Thermoquest). Ecotoxicity data on chlorococcal alga Desmodesmus subspicatus (Scenedesmus subspicatus) and luminescent bacteria Vibrio fischeri are presented here. All toxicity data as effective volume Vtox are expressed. The results show good treatment ability of the treatment plant and proved used system as an appropriate tool for efficiency assessment of treatment and/or decontamination processes.
Amidoalkylation of heteroaromatic compounds with adducts of acyl chlorides and 3,4-dihydroisoquinoline and isoquinoline
Authors: Venkov Atanas , Statkova-Abeghe Stela , Donova Atanaska
Published: August 2006

The N-acyliminium intermediates of 3,4-dihydroisoquinoline and salts of isoquinoline with acyl chlorides were successfully used as amidoalkylating reagents toward synthesis of heterocyclic aromatics as indole, pyrrole, thiophene and pyrazine.
Hydrogen yield from water radiolysis in the presence of zeolites
Authors: Cecal Alexandru , Colisnic Dan , Popa Karin , Paraschivescu Andrei , Bilba Nicolae , Cozma Danut
Published: August 2006

This paper reports a study of the decomposition of water by gamma radiolysis in the presence of zeolites ZSM-5, SAPO-5, and MOR. The irradiation is performed using 60Co as a source with 1.12×1015 Bq activity at a 8.3 kGy/h dose rate. The stable products of radiolysis as well as the other chemical species are measured by mass spectrometry. The calculated radiation yield (GH
2) generally decreases in the order: H-ZSM-5>Na-ZSM-5>H-SAPO-5>MOR under the given experimental conditions; the yield is higher in the presence of these catalysts than in their absence.
Crystal structure, infrared and raman spectra of tripotassium trisaccha-rinate dihydrate, K3(C7H4NO3S)3·2H2O
Authors: Jovanovski Gligor , Kaitner Branko , Grupce Orhideja , Naumov Pance
Published: August 2006

The crystal structure of tripotassium trisaccharinate dihydrate, K3(C7H4NO3S)3·2H2O, is triclic, space group
$$P \bar 1, Z = 2$$
. It consists of three crystallographically independent potassium and saccharinato ions as well as two structurally different water molecules. Potassium coordination polyhedra are irregular, with K1 and K3 six-coordinated and the third one K2 seven-coordinated. The K−O distances range from 2.652(9) to 3.100(2) Å(mean: 2.790 Å) whereas the K−N distance is 3.025(3) Å. The water molecules W2 is disordered over three positions with occupancies of approximately 0.6, 0.2 and 0.2. The hydrogen atom (H1W1) of the ordered water molecule (O1W) is hydrogen bonded to the sulfonyl oxygen atom (O11) (R(O...O)=2.976(3) Å), whereas the other hydrogen atom (H2W1) is bifurcated to the carbonyl oxygen atom (O13) (R(O...O)=2.851(3) Å) and the disordered water molecules (O23W) (R(O...O)=3.067(12) Å). The carbonyl oxygens (O13, O23 and O33) and one of the disordered water molecules (O22W) are involved in C−H...O hydrogen bonds (R(C−H...O)=3.027(4)–3.304(9) Å). Structural characteristics of the studied compound are compared with the analogous trisodium trisaccharinate dihydrate and dipotassium sodium trisaccharinate monohydrate. Infrared and Raman spectra of the title compound have been analyzed in relation to the structure, and compared with the spectra of trisodium trisaccharinate dihydrate.
Determination of aristolochic acid by capillary zone electrophoresis
Authors: Kvasnička František , Ševčík Rudolf , Voldřich Michal , Krátká Jana
Published: August 2006

A simple and rapid capillary zone electrophoresis (CZE) method for the determination of aristolochic acid (AA) in dietary supplements and selected herbs is described. A clear separation of AA from other sample constituents was achieved within 5 minutes without any sample clean up. A mixture of 20 mM-morpholinethanesulphonic acid+10 mM-BisTrisPropane+0.2% hydroxyethylcelullose in 10% methanol serves as a background electrolyte. The linearity, accuracy, intra-assay and detection limit of the developed method are 200–6000 ng/mL, 95–103%, 3.5%, and 50 ng/ml, respectively. Ease of use, sufficient sensitivity and low running cost are the most important attributes of the CZE method. The proposed CZE method was compared with HPLC.
Removal of 60Co2+ and 137Cs+ ions from low radioactive solutions using Azolla caroliniana willd. water fern
Authors: Popa Karin , Cecal Alexandru , Humelnicu Doina , Caraus Ioan , Draghici Camelia
Published: August 2006

This study concerns the removal of the 137Cs+ and 60Co2+ β+γ-radioactive ions in Azolla caroliniana Willd. water fern. The living fern and two different types of biosorbent prepared from Azolla caroliniana were tested to remove the above-mentioned radioactive ions from dilute solutions, in the absence and in the presence of the ionic competition. Effective 137Cs+ and 60Co2+ ions removal from low radioactive wastewaters was demonstrated. The time dependent K d(t) values were calculated from the absorption data. These results indicate that removal process achieved equilibrium in about 120 min and that it involves two steps: rapid and slow absorption; the active process (metabolic bioaccumulation on the living fern) was responsible for above one half of the total removal process. A thin layer radiochromatography study leads to the conclusion that the biochemical components in which 137Cs+ and 60Co2+ place themselves are of a polysaccharide and lipoid fractions.
Theoretical study of structure, vibrational and electronic spectra of isomers of methyl-3-methoxy-2-propenoate
Authors: Virdi Ajit , Gupta V. , Sharma Archna
Published: August 2006

A systematic quantum mechanical study of the possible conformations, their relative stabilities, vibrational and electronic spectra and thermodynamic parameters of methyl-3-methoxy-2-propenoate has been reported for the electronic ground (S0) and first excited (S1) states using time-dependent and time-independent Density Functional Theory (DFT) and RHF methods in extended basis sets. Detailed studies have been restricted to the E-isomer, which is found to be substantially more stable than the Z-isomer. Four possible conformers c′Cc, c′Tc, t′Cc, t′Tc, of which the first two are most stable, have been identified in the S0 and S1 states. Electronic excitation to S1 state is accompanied with a reversal in the relative stability of the c′Cc and c′Tc conformers and a substantial reduction in the rotational barrier between them, as compared with the S0 state. Optimized geometries of these conformers in the S0 and S1 states are being reported. Based on suitably scaled RHF/6-31G** and DFT/6-311G** calculations, assignments have been provided to the fundamental vibrational bands of both these conformers in terms of frequency, form and intensity of vibrations and potential energy distribution across the symmetry coordinates in the S0 state. A complete interpretation of the electronic spectra of the conformers has been provided.
Flow-injection analysis with a small cylindrical wire type electrode
Authors: Denchev Zhivko , Nikolov Nikola
Published: August 2006

An amperometric detector with a small thin mercury film electrode is described. The device demonstrates advantageous operational characteristics such as small dispersion (D<2) and “memory effect” (me<0.6%), extensive maximum sample frequency (msf −200 samples/h), and high sensitivity. It has been proven useful in flow-injection analysis at a constant potential under hydrodynamic conditions.
Voltammetric determination of the trace amounts of bromate in drinking water after pre-concentration on hydrous γ-Al2O3
Authors: Kościelna Honorata , Ren Maria
Published: August 2006

A differential pulse voltammetric (DPV) method for the determination of bromate in drinking water, after pre-concentration on γ-Al2O3, is proposed. The reduction peak of bromate has been observed at the potential Ep-−1.6 V in an ammonia buffer as a supporting electrolyte. The method has been successfully applied to determine a bromate concentration of 2.5 μg·l−1 in drinking water (RSD=6.1%, n=7). A sample pre-treatment with a column filled with mixed cation-exchange resin in Ag, Ba and H forms was needed before pre-concentration of bromate on alumina.
QSPR modeling aqueous solubility of polychlorinated biphenyls by optimization of correlation weights of local and global graph invariants
Authors: Castro Eduardo , Toropov Andrey , Nesterova Alexandra , Nabiev Ozad
Published: August 2006

Aqueous solubilities of polychlorinated biphenyls have been correlated with topological molecular descriptors which are functions of local and global invariants of labeled hydrogen filled graphs. Morgan extended connectivity and nearest neighboring codes have been used as local graph invariants. The number of chlorine atoms in biphenyls has been employed as a global graph invariant. Present results show that taking into account correlation weights of global invariants gives quite reasonable improvement of statistical characteristics for the prediction of aqueous solubilities of polychlorinated biphenyls.
The role of quantum interference in determining transport properties of molecular bridges
Authors: Walczak Kamil
Published: August 2006

An analytical approach to the electron transport phenomena in molecular devices is presented. The analyzed devices are composed of various molecular bridges attached to two semi-infinite electrodes. Molecular system is described within the tight-binding model, while the coupling to the electrodes is analyzed through the use of Newns-Anderson chemisorption theory. The current-voltage (I-V) characteristics are calculated through the integration of transmission function in the standard Landauer formulation. The essential question of quantum interference effect of electron waves is diseussed in three aspects: (i) the geometry of a molecular bridge, (ii) the presence of an external magnetic field and (iii) the location of chemical substituent.
Characterization and sorption properties of Aspergillus niger waste biomass
Authors: Ŝpanêlová M. , Machoviĉ V. , Březina M.
Published: August 2006

The structure and the biosorption properties of fungal biomass of Aspergillus niger originated from citric acid fermentation industry was investigated. This waste biomass, produced in high quantity in carefully controlled industrial processes, has certain favourable characteristics that may be improved for its usefulness. In environmental chemistry, it is known for the removal of heavy metals cations. In this work, different alkaline treatments (1M NaOH/20°C/24 h and 10M NaOH/107°C/6 h) were used to evaluate the dependence of sorption properties of biomass on the cell wall composition. The biosorption was studied by the batch method, with the biomass concentration of 1 g/l, at pH 6. The adsorption of lead was more effective than that of cadmium. The biosorption capacity was evaluated using the biosorption isotherm derived from the equilibrium data. At pH 6, the maximmum lead biosorption capacity estimated with the Langmuir model was 93 mg/g dry biomass.
Functionalization of polyolefins by reactive processing
Authors: Zelenetskii A. , Volkov V. , Artem’eva N. , Sizova M. , Nikol’skaya V. , Egorova N.
Published: August 2006

From the study of the modification of PE and PP with maleic anhydride, maleic acid and an acid salt of maleic acid (sodium maleate) in a liquid or solid state, it was shown that the main controlling factor in the solid state modification of polyolefins is the joint plastic deformation of the system components. The changes of molecular characteristics were investigated by gel permeation chromatography. It was shown, that the molecular weight of modified PP samples increases at times by linking with intermolecular associates in the solutions. The formation of associates plays essential role in the behaviour of solutions of modified PP. The morphology of modified PP samples was investigated by scanning electron microscopy. It was shown, that intermolecular association strongly influences on the processes of formation and growth of nucleus and the structure of generated polymeric materials.
Hydride generation atomic absorption spectrometry with insitu graphite tube trapping for the determination of Se (IV) and Se (VI) in baltic sea water samples
Authors: Niedzielski P. , Siepak M. , Dudzińska-Huczuk B.
Published: August 2006

This paper reports the results of an optimisation study for a procedure to determine the total selenium and its inorganic species, Se(IV) and Se(VI) using atomic absorption spectrometry combined with hydride generation and in-situ trapping of the analyte on the inner walls of the graphite tube. With the use of the proposed modification, a detection limit (3σ) of 0.018 ng/ml is achieved. This paper presents exemplary results, according to the proposed procedure, for selenium determination in samples of marine water. The concentrations of selenium in the samples ranged from <0.02 ng/ml to 0.16ng/ml of Se(IV) and from <0.02 ng/ml to 0.10 ng/ml of Se(VI).
Multivariate statistical assessment of polluted soils
Authors: Simeonov Vasil , Einax Juergen , Tsakovski Stafan , Kraft Joerg
Published: August 2006

This study deals with the application of several multivariate statistical methods (cluster analysis, principal components analysis, multiple regression on absolute principal components scores) for assessment of soil pollution by heavy metals. The sampling was performed in a heavily polluted region and the chemometric analysis revealed four latent factors, which describe 84.5 % of the total variance of the system, responsible for the data structure. These factors, whose identity was proved also by cluster analysis, were conditionally named “ore specific”, “metal industrial”, “cement industrial”, and “steel production” factors. Further, the contribution of each identified factor to the total pollution of the soil by each metal pollutant in consideration was determined.
Polymer-Titanium hybrids obtained by radical polymerization and Sol-Gel process
Authors: Donescu Dan , Serban Sever , Gosa Kristiana , Petcu Cristian
Published: August 2006

The possibility to prepare hybrids made by poly(vinyl acetate) (PVAc), poly(methyl methacrylate) (PMMA) and/or poly(ethyl acrylate) (PEtA) with TiO2 was studied. The processes of polymer formation-radical polymerization and sol-gel process for inorganic network —were achieved simultaneously. Due to a high reactivity of titanium isopropoxide (TIP) in the sol-gel process, a complexant comonomer, allyl acetoacetate (AlAcAc), was used. Covalent bonds between polymer and inorganic chains were obtained by addition of trialkoxysilane derivates with vinyl (VTES) or methacryloyl (MPTS) groups. The presence of TIP inhibits the radical polymerization of vinyl acetate (VAc). The PVAc-TiO2 hybrids were produced by the sol-gel process of TIP in the presence of pre-obtained PVAc. Except for VTES and MPTS, trialkoxysilane derivates with methyl (MeTES), octyl (OTES) and phenyl (PTES) groups were used. The thermal stability of hybrids is strongly affected by TiO2 presence and by the type of trialkoxysilane derivates. The thermal stability of PVAc hybrids decreases in the presence of TiO2 inorganic network. The glass transition temperature of polymers increases in the presence of the inorganic network.
Thermal behavior of some aromatic copolyethers containing a propylenic spacer
Authors: Hurduc Nicolae , Damian Cristina , Tarus Anca , Toader Violeta , Hurduc Natalia
Published: August 2006

The main objective of this paper is to study the thermal stability of some aromatic copolyethers containing a propylenic spacer. Some of the investigated copolyethers displayed a liquid crystalline (LC) behavior, with the presence of the mesogenic groups in the main chain, inducing high values of the thermal transition temperatures. As a consequence, a thermal stability study was necessary to establish the maximum temperature value for the LC behavior characterization. A thermal degradation mechanism is proposed, taking into consideration the azobenzenic unit as the weakest link in the polymer chain and thus, the starting point of the thermal degradation process. The degradation mechanisms were correlated with the chemical structure and the polarity and conformation of the chains. Conformational analysis was performed using molecular simulations. Freeman-Caroll and Coats-Redfern methods were used to calculate some kinetic characteristics.
Speciation analysis of inorganic form of arsenic in ground water samples by hydride generation atomic absorption spectrometry with insitu trapping in graphite tube
Authors: Niedzielski Przemysław , Siepak Marcin
Published: August 2006

This paper presents the results of a study on the optimization of the determination of total arsenic and its species using the absorption atomic spectrometry method combined with hydride generation and in-situ concentration on the inner walls of the graphite tube. To ensure a maximum efficiency of the in-situ analyte concentration on the graphite tube walls, a palladium modifier subjected to preliminary thermal reduction was used. The limits of detection (3σ) were 0.019 ng/mL for total As and 0.031 ng/mL for As(III) at the preliminary analyte concentration for 60s. The optimised procedure of the analyte concentration on the inner walls of the atomiser (graphite tube) was applied for determinations of arsenic in samples of ground water. The content of arsenic in the samples studied varied from 0.21 ng/mL to 0.80 ng/mL for As(III), and from 0.19 ng/mL to 1.24 ng/mL for As(V).
Ion flux's pressure dependence in an asymmetric capacitively coupled rf discharge in NF3
Authors: Mateev Emil , Zhelyazkov Ivan
Published: August 2006

Starting from an analytical macroscopic/phenomenological model yielding the self-bias voltage as a function of the absorbed radio-frequency (rf) power of an asymmetric capacitively coupled discharge in NF3 this paper studies the dependence of the ion flux onto the powered electrode on the gas pressure. An essential feature of the model is the assumption that the ions' drift velocity in the sheath near the powered electrode is proportional to E
α, where E=−ΔU (U being the self-bias potential), and α is a coefficient depending on the gas pressure and cross section of elastic ion-neutral collisions. The model also considers the role of γ-electrons, stochastic heating as well as the contribution of the active electron current to the global discharge power balance. Numerically solving the model's basic equations one can extract the magnitude of the ion flux (at three different gas pressures) in a technological etching device (Alcatel GIR 220) by using easily measurable quantities, notably the self-bias voltage and absorbed rf power.
Is there the radion in the RS2 model?
Authors: Smolyakov Mikhail , Volobuev Igor
Published: August 2006

We analyse the physical boundary conditions at infinity for metric fluctuations and gauge functions in the RS2 model with matter on the brane. We argue that due to these boundary conditions the radion field cannot be gauged out in this case. Thus, it represents a physical degree of freedom of the model.
Fowler-nordheim tunnelling in Au−TiO2−Ag film structures
Authors: Aarik J. , Bichevin V. , Jõgi I. , Käämbre H. , Laan M. , Sammelselg V.
Published: August 2006

I-V-characteristics have been measured for Au−TiO2−Ag structures with TiO2 layers of 30 and 180 nm thickness. The TiO2 films were grown by atomic layer deposition (ALD) technique. In the case of negative bias on the Au electrode, the conduction currents through TiO2 layers follow the Fowler-Nordheim formula for field emission over several orders of magnitude. The bulk of the currents may be attributed to tunnelling, seemingly through a Schottky barrier at the Au−TiO2 junction. In the case of reversed polarity the currents are also observed, but cannot be interpreted as tunnelling.
Industrial challenges for numerical simulation of crystal growth
Authors: Bogdanov M. , Ofengeim D. , Zhmakin A.
Published: August 2006

Numerical simulation of industrial crystal growth is difficult due to its multidisciplinary nature and the complex geometry of the real-life growth equipment. An attempt is made to itemize physical phenomena dominant in the different methods for growth of bulk crystals from the melt and the vapor phase as well as to review corresponding numerical approaches. Academic research and industrial applications are compared. Development of a computational engine and a graphic user interface of the industry-oriented codes is discussed. A simulator for the entire growth process of bulk crystals by sublimation method is described.
A system of units compatible with geometry
Authors: Jancewicz Bernard
Published: August 2006

Alternative system of fundamental units: length, time, action, electrical charge is presented instead of the present one: length, time, mass and electrical current. It contains more quantities which are scalars under scalings. Then it is possible to recognize from the unit, what kind of a geometric quantity is a given physical quantity. This is the reason why the new system of units is called compatible with geometry.
Elastic shape memory effect in In-Pb alloys in the temperature range 0.48–180 K
Authors: Natsik V. , Fomenko L. , Lubenets S.
Published: August 2006

Pseudoelasticity caused by pseudotwinning in short-range ordered In-Pb alloys (6, 8 and 11.6 at. % Pb) is studied in the temperature range 0.48–180 K. The mechanical hysteresis parameters, namely, the thermodynamic stress τT which provides the reversibility of plastic deformation and the frictional stress τf which characterizes the resistance offered by crystal lattice and its defects to twin boundaries motion are estimated. It is found that athermal processes determine the reversible deformation: the mechanical parameters τT and τf do not depend on temperature and strain rate. The stress τT increases and the stress τf decreases with increasing Pb content. One of the main conditions of the exhibition of superelasticity is the fulfillment of the inequality τT>τf.
On the lyman problem
Authors: Kolár Václav
Published: August 2006

This paper attempts to answer Lyman's question (1990) on the non-uniqueness in defining the 3D measure of the boundary vorticity-creation rate. Firstly, a straightforward analysis of the vorticity equation introduces a definition of a general vorticity flux-density tensor and its ‘effective’ part. The approach is strictly based on classical field theory and is independent of the constitutive structure of continuous medium. Secondly, the fundamental question posed by Lyman dealing with the ambiguity of the 3D measure of the boundary vorticity-creation rate for incompressible flow is discussed. It is shown that the original 3D measure (for an incompressible Newtonian fluid defined by Panton 1984), which is reminiscent of an analogy to Fourier's law, is in its character ‘effective’ and plays a crucial role in the prognostic vorticity transport equation. The alternative 3D measure proposed by Lyman includes, on the other hand, a ‘non-effective’ part, which plays a role in the local determination of the ‘effective’ measure as well as in a certain diagnostic integral boundary condition.
Decoherence within a single atom
Authors: Bene Gyula
Published: August 2006

An “almost diagonal” reduced density matrix (in coordinate representation) is usually a result of environment induced decherence and is considered the sign of classical behavior. We show that the proton of a ground state hydrogen atom can indeed possess such a density matrix. This example demonstrates that the “almost diagonal” structure may be derived from an interaction with a low number of degrees of freedom which play the role of the environment. We also show that decoherence effects in our example can only be observed if the interaction with the measuring device is significantly faster than the interaction with the environment (the electron). In the opposite case, when the interaction with the environment is significant during the measurement process, coherence is maintained. Finally, we propose a neutron scattering experiment on cold He atoms to observe decoherence which shows up as an additional positive contribution to the differential scattering cross section. This contribution is inversely proportional to the bombarding energy.
Quantum diffusion
Authors: Pushkarov Dimitar
Published: August 2006

Basic ideas and results which characterize quantum diffusion of defects in quantum crystals like solid helium as a new phenomenon are presented. Quantum effects in such media lead to a delocalization of point defects (vacancies, impurities etc.) and they turn into quasiparticles of a new type—defectons, which are characterized not by their position in the crystal lattice but by their quasimomentum and dispersion law. Defecton-defecton and defecton-phonon scattering are considered and an interpolation formula for the diffusion coefficient valid in all interesting temperature and concentration regions is presented. A comparison with the experimental data is made. Some alternative points of view are discussed in detail and the inconsistency of the Kisvarsanyi-Sullivan theory is shown.
The exclusive reaction of pion quasi-elastic knockout from nucleon p(e, e′ π)B to various states of the final baryon-spectator B and the quark models for the pion cloud of nucleon
Authors: Neudatchin Vladimir , Obukhovsky Igor , Sviridova Ludmila , Yudin Nikolai
Published: August 2006

The pion momentum distributions (MDs) in four channels of virtual decay p→B+π, B = N, Δ, N 1/2-(1535), N 1/2+(1440) are calculated in two models, the microscopic model of 3 P 0 scalar q−q fluctuation with the pion as a composite q−q-system and the chiral semi-microscopic model of πq interaction with the pion as a structureless Goldstone boson. The results of the above models are similar for the baryon states B = N, Δ, N 1/2-(1535) but are rather different for the Roper resonance N 1/2+(1440) which corresponds to excitation of two oscillator quanta in the nucleon. The experimental investigation of pion MDs by means of the reaction of quasi-elastic knockout of pion by an electron of a few GeV energy p(e, e′ π)B may be very suitable for Jefferson Laboratory, Virginia (JLab).
Electrical conductivity studies of mixed phthalocyanine thin films
Authors: Varghese Abraham , Menon C.
Published: August 2006

Thin films of mixed of Copper Phthalocyanine (CuPc) and Nickel Phthalocyanine (NiPc) are deposited onto a pure glass substrate by a simultaneous thermal evaporation technique at room temperature. The material D.C. electrical conductivity of films at room temperature and also films annealed at 523 K has been investigated. The optical absorption and band gaps of the films are also measured. The results show that the electrical resistance is lower for the mixed films compared with the pure samples and also the optical band gap decreases for the mixed samples compared to the pure samples.
Photon-induced switching and tunneling phenomena in a YBCO thin film junction
Authors: Yang Xi , Beckwith Andrew , Miller John
Published: August 2006

In the persistent photoconductivity (PPC) phenomenon, illumination of a YBa2Cu3O6.5 thin film junction with a 1mW He−Ne laser leads to the decrease of the critical voltage (similar to the threshold voltage). The decrease of the critical voltage was reversed by illumination with incandescent light. The critical voltage across the junction was experimentally decreased and increased by alternating illumination between He−Ne laser and incandescent light. We also observed visible quenching of the photo-induced state using a 5mW He−Ne laser. Finally, the threshold behavior of the junction was destroyed by illuminating it with incandescent light.
Simulation model for anomalous precession of the perihelion of mercury's orbit
Authors: Biswas Abhijit , Mani Krishnan
Published: August 2006

The ‘anomalous perihelion precession’ of Mercury, announced by Le Verrier in 1859, was a highly controversial topic for more than half a century and invoked many alternative theories until 1916, when Einstein presented his theory of general relativity as an alternative theory of gravitation and showed perihelion precession to be one of its potential manifestations. As perihelion precession was a directly derived result of the full General Theory and not just the Equivalence Principle, Einstein viewed it as the most critical test of his theory. This paper presents the computed value of the anomalous perihelion precession of Mercury's orbit using a new relativistic simulation model that employs a simple transformation factor for mass and time, proposed in an earlier paper. This computed value compares well with the prediction of general relativity and is, also, in complete agreement with the observed value within its range of uncertainty. No general relativistic equations have been used for computing the results presented in this paper.
Excess thermodynamic quantities of D2O water calculated from its Raman O−D stretching spectra
Authors: Georgiev Mircho , Goutev Nikolay , Nickolov Zhorro , Georgiev Georgi
Published: August 2006

Excess thermodynamic functions of D2O water have been calculated from the vibrationally decoupled O−D stretching spectra of very dilute solutions of HOD in H2O. Comparison of the results with reference calorimetric data for water showed a good correspondence for excess heat capacity above the melting point of ice. The excess enthalpy at the melting point also coincides well with latent heat of melting.
Magnetic and transport properties of monocrystallineFe
3
O
4
Authors: Paul Karen
Published: August 2006

A monocrystal ofFe
3
O
4 is characterized by resistance, magnetoresistance and magnetic measurements in a temperature range from 4.2 K to 350 K and magnetic field-cycling from −9 T to 9 T. The resistance measurements revealed a metal-insulator Verwey transition (VT) atT
v=123.76 K with activation energy E=92.5 meV at T >T
v and temperature-substitute for the activation energy below the VT,T
0=E/k
B≈3800 K within 70 K–110K. The magnetotransport results independently verified the VT at 123.70 K, with discontinuous change in the magnetic moment ΔM≈0.21 ΔM≈0.21μ
B and resistance hysteresis, dependent on the magnetic field in a narrow temperature range of 0.4° around theT
v. The magnetic characterization established self consistentlyT
v as ≈123.67 K, the jump in the magnetization at the VT≈0.25μ
B and confirmed, that the magnetocrystalline anisotropy is the main microscopic mechanism responsible for the magnetization of the monocrystal (88%) with additional natural and imposed defects contributing as 12%.
Quasilinearization for the periodic boundary value problem for hybrid differential equation
Authors: Hall L. , Hristova S.
Published: August 2006

The method of quasilinearization for a periodic boundary value problem for nonlinear hybrid differential equations is studied. It is shown that the convergence is quadratic.
The Dirichlet problem for Baire-one functions
Authors: Spurný Jiří
Published: August 2006

Let X be a compact convex set and let ext X stand for the set of all extreme points of X. We characterize those bounded function defined on ext X which can be extended to an affine Baire-one function on the whole set X.
Generalized Mukai conjecture for special Fano varieties
Authors: Andreatta Marco , Chierici Elena , Occhetta Gianluca
Published: August 2006

Let X be a Fano variety of dimension n, pseudoindex i
X and Picard number ρX. A generalization of a conjecture of Mukai says that ρX(i
X−1)≤n. We prove that the conjecture holds for a variety X of pseudoindex i
X≥n+3/3 if X admits an unsplit covering family of rational curves; we also prove that this condition is satisfied if ρX> and either X has a fiber type extremal contraction or has not small extremal contractions. Finally we prove that the conjecture holds if X has dimension five.
Cycles of polynomial mappings in two variables over rings of integers in quadratic fields
Authors: Pezda T.
Published: August 2006

We find all possible cycle-lengths for polynomial mappings in two variables over rings of integers in quadratic extensions of rationals.
13C NMR and mass spectrometry of soil organic matter
Authors: Ivanova Galya , Randall Edward
Published: August 2006

Liquid state, high resolution 13C NMR spectroscopy and mass spectrometry were used to study the composition and structure of soil organic matter (SOM) using soil extracts from two long-term experiments at the Rothamsted Experimental Station. Both one- and two-dimensional NMR techniques were applied. 13C NMR sub-spectra of the CHn (n=0...3) groups, obtained by the Distortionless Enhancement by Polarisation Transfer (DEPT) technique, were used for the elucidation of the qualitative and quantitative composition of humic and fulvic acids in the soils. The chemical structure of SOM was further analysed at the molecular level through Fast Atom Bombardment Mass Spectrometry (FABMS) and Gas Chromatography-Mass Spectrometry (GC/MS). Humic and fulvic extract results were not only compared to each other, but also to the solid state 13C NMR results for the complete soil sample.
Water quality study of the Struma river basin, Bulgaria (1989–1998)
Authors: Simeonova P. , Simeonov V. , Andreev G.
Published: August 2006

The present paper deals with an estimation of the water quality of the Struma river. Long-term trends, seasonal patterns and data set structures are studied by the use of statistical analysis. Nineteen sampling sites along the main river stream and different tributaries were included in the study. The sites are part of the monitoring net of the region of interest. Seventeen chemical indicators of the surface water have been measured in the period 1989–1998 in monthly intervals. It is shown that the water quality is relatively stable throughout the monitoring period, which is indicated by a lack of statistically significant trends for many of the sites and by chemical variables. Several seasonal patterns are observed at the sampling sites and four latent factors are identified as responsible for the data set structure.
Refractive index modulation in polymeric photochromic films
Authors: Ortyl Ewelina , Kucharski Stanisław
Published: August 2006

Photochromic properties of methylacrylate monomers and polymers containing azobenzene groups with heterocyclic sulfonamide functionalities viz sulfisomidyne (4-amino-N-[2,6-dimethylpyrimidyn-4-yl]benzenesulfonamide) and sulfamethoxazole (4-amino-N-[5-methylisoxazol-3-yl]benzenesulfonamide) substituents were investigated. On illumination with light the azobenzene group underwent trans-cis isomerisation, which was manifested by a drop in the absorbance of the maximum absorption peak at ca. 450 nm and by decrease in refractive index.

Quantum chemical calculations showed significant differences in UV-VIS spectra, dipole moments, polarizability and refractive index between both cis and trans form of the chromophoric monomers.

The illumination of spin-coated polymer films during ellipsometry measurements resulted in a change in refractive index within the range of 0.014 to 0.025. The dynamics of growth and decay of refractive index changes, was described by biexponential functions approach.
On the three-phase mass transfer with solid particles adhered to the gas-liquid interface
Authors: Nagy Endre
Published: August 2006

A heterogeneous, multi-layer mass transfer model is proposed for prediction of the effect of multi-layer packing of catalyst particles adhered to the gas-liquid interface. The behavior of the mass transfer rate with respect to the multi-layer packing, to the particle size and mass transfer coefficient without particles is discussed. It is shown that enhancement can be considerably increased by multi-layer packing compared to that of mono-layer packing, depending on the values of particle size and mass transfer coefficient. The predicted mass transfer rates using the proposed model was verified with experimental data taken from the literature. The model presented should be superior to that of published in the literature.
Carbon, natural and synthetic sorbents for decontamination of objects of ecosystems from pathogenic microflora
Authors: Shvets D. , Denisova T. , Strelko V.
Published: August 2006

Physico-chemical characteristics and sorption activity of carbon, organosilica sorbents and their modified forms towards proteins, possessing specific activity, and cholerae vibrio have been studied. It was found, that carbon materials modified by copper (II) effectively extracts cholerae vibrio (100%) and may be recommended for disinfection of drinking water. Sorption capacity of organosilica sorbents and their modified by copper (II) forms towards pathogenic microflora (E.coli, St.aureus, Ps.aeruginosa) depending on the composition of the sorbents, concentration of the modified reagent, pH of medium have been evaluated. The rows of the increase of sorption of pathogenic microorganisms by synthetic sorbents in water-salt solutions were established: Al(III)<Zn(II)<Cu (II). It was shown that inhibiting effect of modified synthetic organosilica and natural sorbents towards such pathogenic microorganisms as E-coli, St.aureus Ps.aeruginosa and fungus Bacillus pyocyaneus accordingly is equal 80–98%.
Aqueous p-nitrotoluene oxidation induced with direct glow discharge plasma
Authors: Gao Jinzhang , Liu Yongjun , Yang Wu , Pu Lumei , Yu Jie , Lu Quanfang
Published: August 2006

A plasma induced degradation process has been studied to treat 4-nitrotoluene (4-NT) present as an aqueous pollutant. The plasma was locally generated from a glow discharge around a tip of a platinum anode in an electrolytic solution. The influence of initial pH and Fe2+ on the degradation was examined. Major intermediates resulting from the degradation process were identified. Amongst the aromatic intermediates, p-hydroxybenzoic acid was the predominant degradation product. The formation of oxalic acid, malic acid was also observed. The final products of degradation were NH4+, NO3− and CO2. Based on the analysis of intermediates and the kinetic considerations, the degradation was shown to follow a pseudo-first order reaction hence, a possible reaction pathway was proposed.
Rational design and convenient synthesis of a novel family of ruthenium complexes with O,N-bidentate ligands
Authors: Drozdzak Renate , Ledoux Nele , Allaert Bart , Dragutan Ileana , Dragutan Valerian , Verpoort Francis
Published: August 2006

A two step procedure for the synthesis of a novel family of homogeneous and immobilized Ru-complexes containing Schiff bases as O,N-bidentate ligands is described. The new Ru-complexes have been structurally characterized by IR, Raman,1H-,13C-NMR spectroscopy. The Schiff bases were associated with a diversity of inorganic and organic ligands such as chloride, phosphane, arenes, various carbenes (alkylidene, vinylidene, indenylidene and allenylidene as well as N-heterocyclic carbenes) and cyclodienes. By choosing a selective range of substituents for the Schiff base, useful physical and chemical properties of the prepared Rucomplexes can be induced. This synthetic approach is promising in creating a valuable and diverse selection of Ru-complexes, valuable for future applications.
Spectrophotometric determination of oxygen content in calcium substituted RBCO (R=Eu, Gd, Er) superconductors
Authors: Stoyanova-Ivanova Angelina , Nedeltcheva Tsvetanka , Vladimirova Latinka
Published: August 2006

The oxygen stoichiometry in R1−x
CaxBa2Cu3Oy (R=Eu, Er, Gd; x=0, 0.2, 0.25, 0.3) superconducting bulk samples was determined spectrophotometrically. The dependence of the critical temperature on the y-oxygen coefficient and the x-coefficient of the included calcium was studied.
On the mechanism of electroluminescence emission by porous silicon layers
Authors: Velasco Jaime
Published: August 2006

The analytical treatment of a model considering the electrooxidation of p-porous silicon layers under galvanostatic conditions is able to give account of experimental facts such as the shape and location of the electroluminescence peak as well as of the spectral shift of the electroluminescence peak produced by oxidation. The proposed model considers electroluminescence to be the result of electron injection into the conduction band by an adsorbed intermediate produced by electrooxidation of the surface coverage with hydrogen or siloxene of the silicon nanocrystallites. The access of holes to the surface is made possible by low accumulation layer conditions and is the rate determining step in the electroluminescence mechanism. In this way it is possible to give a satisfactory explanation to the shift towards the blue experimented by the electroluminiscence emission maximum as a consequence of electrooxidation.
Catalytic air oxidation of manganese in synthetic waters
Authors: Kaya Nihan , Karadurmus Erdal , Alicilar Ahmet
Published: August 2006

An attempt was made to study the oxidation of manganese by air in synthetic waters. A series of batch experments were performed at differnet values of concentration, temperature and pH. Unoxidized manganese in the solution was determined by formaldoxime spectrometric method. Results of these studies indicated that the air oxidation of manganese soluble in water can be effectively performed in basic media and that oxidation yield increasedwith an increase in pH and concentration. The yield was very high in the presence of manganese dioxide, sepiolite or clinoptilolite in solution and, the oxidation was almost completed especially at high values of pH and concentration. The reaction was found to be first order with respect to Mn2+ with a very low activation energy. A yield of 62% was obtained for the air oxidation of wastewater taken from the treatment plant of Corum Municipality.
Complex symmetrized calculations on ammonia vibrational levels
Authors: Rashev Svetoslav , Tsonev Lyubo , Zhechev Dimo
Published: August 2006

This paper introduces a fully symmetrized Hamiltonian formalism designed for description of vibrational motion in ammonia (and any XH3 molecule). A major feature of our approach is the introduction of complex basis vibrational wavefunctions in product form, satisfying the complex symmetry species (CSS) of the molecular symmetric top point group (D
3h). The described formalism for ammonia is an adaptation of the approach, previously developed and applied to benzene, based on the CSS of the point group D
6h. The molecular potential energy surface (PES) is presented in the form of a Taylor series expansion around the planar equilibrium state. Using the described formalism, calculations have been carried out on the vibrational overtone and combination levels in 14NH3 up to vibrational excitation energies corresponding to the fourth N-H stretch overtone. The results from the calculations are adjusted to experimentally measured data, in order to determine the values of the harmonic and some anharmonic force constants of the molecular PES.
Early postoperative gastric enteral nutrition improve gastric emptying after cardiac surgery
Authors: Šustić Alan , Zelić Marko , Medved Igor , Sokolić Jadranko
Published: August 2006

Postoperative intragastric enteral feeding in cardiac surgery patients is frequently complicated by delayed gastric emptying. The aim of the study was to evaluate how early postoperative gastric enteral nutrition affects the gastric emptying in coronary artery by-pass graft (CABG) surgery patients.

In the prospective, randomized study 40 patients treated at intensive care unit after CABG surgery were studied. Patients were divided in two groups: enteral feeding group E (20 patients: age 59±8 yr.; male 70%) and control group C (20 patients: age 58±10 yr.; male 80%), respectively. Paracetamol absorption test was used to evaluate gastric emptying. In the group E postoperative gastric supply of enteral formula begun 18 hours after surgery and after 6 hours the supply was stopped and paracetamol solution was administrated by nasogastric tube. The patients in group C for.rst 24 hours received only crystalloid solutions intravenously and paracetamol solution by nasogastric tube. Blood samples were obtained at 0 (t0), 15 (t+15), 30 (t+30), 60 (t+60) and 120 (t+120) min after administration of paracetamol.

The values of plasma paracetamol concentration (PPC) at 15 and 120 min were significantly higher in group E vs. group C: (t+15) 3.3±2.5
vs. 1.7±1.9 and (t+120) 5.2−2.8 vs. 3.3±1.6 (p <0.05). The PPC values at 30 and 60 min were higher, but not signi.cantly, in group E vs. group C: (t+30) 3.7±2.0 vs. 2.9±2.7 and (t+60) 5.1±3.2 vs. 3.9±3.5 (p = NS). The area under the PPC curve was 429 ± 309 in the E group vs. 293 ± 204 in the group C (p < 0.05).

In conclusion an early postoperative gastric administration of nutritients after CABG surgery stimulates the gastric emptying.
Black smoke air pollution and daily non-accidental mortality in Nis, Serbia
Authors: Bogdanovic Dragan , Nikic Dragana , Milosevic Zoran , Stankovic Aleksandra
Published: August 2006

The short-term effects of ambient black smoke concentrations on total non-accidental, cardiovascular and respiratory mortalities in Nis, during the 2000-2003 period, were investigated.

Daily measurements for black smoke (BS), as well as the daily number of deaths have been collected. Generalised linear models extending Poisson regression were applied. The e.ects of time trend, seasonal variations, days of the week, temperature, humidity and air pressure were adjusted.

The per cent increase in the daily number of total deaths associated with a 10 μg/m3 increase in BS was 1.13% (0.08–2.20%). The e.ect size was slightly higher for cardiovascular mortality (1.25%, 95% CI: 0.53–1.97%). There was no signi.cant association between air pollution and respiratory mortality.

These results indicate that current levels of ambient BS have signi.cant e.ects on total and cardiovascular mortalities in Nis.