bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractThis 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

AbstractThis 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

AbstractThe 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

AbstractThe 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

AbstractThis 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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

AbstractPseudoelasticity 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

AbstractThis 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

AbstractAn “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

AbstractBasic 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

AbstractThe 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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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%.
Generalized Mukai conjecture for special Fano varieties
Authors: Andreatta Marco , Chierici Elena , Occhetta Gianluca 
Published: August 2006

Abstract
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.
13C NMR and mass spectrometry of soil organic matter
Authors: Ivanova Galya , Randall Edward 
Published: August 2006

Abstract
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

AbstractThe 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

AbstractPhotochromic 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

AbstractA 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.