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1

Lower ionospheric electron density changes following lightning discharges

Atıcı R., Güzel E., Sağır S.

Acta Geophysica

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2018

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Vol. 66, no. 4

731--738

EN

The effect of lightning-induced electromagnetic (EM) waves on electron density (Ne) of the lower ionosphere is calculated by using the four-component Glukhov–Pasko–Inan (GPI) model which is modified by including two-body attachment reactions and associative detachment with negative ions of active species (namely, O and N atoms). As a result of the calculations, it is seen that three-body attachment reactions take place at about 50–73 km altitudes, associative detachment takes place at approximately 73–85 km altitudes and two-body attachment reactions take place at approximately 85–95 km altitudes on the electron density. While the effect on electron density of electric field of lightning-induced EM wave is weak at altitudes where associative detachment is effective, it is strong at altitudes where two-body attachment reactions are effective. Also, it is shown that the electron density increases up to approximately 5.5 times when compared with the background density values due to electrons occurring as a result of associative detachment with negative ions of active species.

2

Seasonal Variations of Mid-Latitude Ionospheric Trough Structure Observed with DEMETER and COSMIC

Matyjasiak B., Przepiórka D., Rothkaehl H.

Acta Geophysica

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2016

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Vol. 64, no. 6

2734--2747

EN

The mid-latitude ionospheric trough is a depleted region of ionospheric plasma observed in the topside ionosphere. Its behavior can provide useful information about the magnetospheric dynamics, since its existence is sensitive to magnetospherically induced motions. Midlatitude trough is mainly a night-time phenomenon. Both, its general features and detailed characteristics strongly depend on the level of geomagnetic disturbances, time of the day, season, and the solar cycle, among others. Although many studies provide basic information about general characteristics of the main ionospheric trough structure, an accurate prediction of the trough behavior in specific events is still understood poorly. The paper presents the mid-latitude trough characteristics with regard to the geomagnetic longitude and season during a solar activity minimum, as based on the DEMETER in situ satellite measurements and the data retrieved from FORMOSAT-3/COSMIC radio occultation measurements.

3

Znaczenie i przykłady zastosowania banków pseudoatomów asferycznych w krystalografii małych cząsteczek i ich potencjalne wykorzystanie w krystalografii makromolekuł

Dominiak P. M.

Wiadomości Chemiczne

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2014

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[Z] 68, 5-6

429--455

EN

X-rays are diffracted by the electron density of crystals. Thus, the correct analysis of a single crystal X-ray diffraction pattern can provide information about the distribution of the electron density. How precise and accurate the information could be is largely determined by the resolution of the data collected. The majority of X-ray diffraction data is collected at and below the standard resolution, dmin= 0.84 Å. Before the development of pseudoatom databases, such resolution permitted to carry out X-ray refinement only with the use of simple model of electron density called the Independent Atom Model (IAM). In the IAM, individual atoms are represented by the spherically averaged electron density distributions obtained by theoretical methods for isolated atoms in the ground state. The IAM does not take into account changes in the density distribution of individual atoms caused by such phenomena as chemical bond formation, charge transfer, lone electron pairs, etc. Only the geometrical information of the crystal structure is obtained from the IAM refinement. A more physical model has been introduced in which an atom is represented as a finite spherical harmonic expansion of the electron density around each atomic center and is called a pseudoatom. Such definition allows the pseudoatom electron density to be individually adjusted (by changing values of pseudoatom parameters) to account for density departure from spherical and neutral model. However, to refine pseudoatom parameters with experimental data subatomic resolution is required. It has been shown that the values of pseudoatom parameters are almost identical for atoms in similar chemical environments, i.e. atoms having similar local topology of connecting chemical bonds. Therefore it was possible to build a databank of different types of pseudoatoms and to use the bank to generate the Transferable Aspherical Atom Model (TAAM) for any organic molecule, including proteins and nucleic acids. There are three different pseudoatom databanks being developed: ELMAM2, GID and UBDB. They differ by the source of pseudoatom parameters and by the way how atom types are defined. Replacement of the IAM model by the TAAM in the refinement procedure of standard diffraction data leads to more accurate geometrical information and provide access to quantitative estimation of the electron density distribution and properties derived from it (dipole moment, electrostatic potential, etc.) for molecules in a crystalline environment. The review summarizes the research on the verification and application of pseudoatom databases.

4

Zastosowanie topologicznej analizy gęstości elektronowej do opisu oddziaływań niekowalencyjnych

Bankiewicz B., Rybarczyk-Pirek A., Małecka M., Domagała M., Palusiak M.

Wiadomości Chemiczne

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2014

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[Z] 68, 5-6

457--486

EN

All atomic and molecular properties are governed by an electron density distribution. Thus, the methods that deal with an analysis of the electron density distribution should have a particular appeal for chemists and help to understand the electron structure of molecules. The Quantum Theory of Atoms in Molecules gives the unique opportunity to have an insight into a region (e.g., an atom) of a given system (e.g. a molecule), delivering partitioning scheme which is defined explicitly within the rigorous quantum theory, from one side, and is applicable for experimentally available set of observables, from the other side. In that way QTAIM delivers a chemist a theoretical tool to study a small part of a molecule only, instead of dealing with the total energy of a whole system. In consequence, QTAIM has become one of the most powerful utilities of modern chemistry, forming a bridge between advanced theoretical and experimental techniques. In particular the properties of the electron density function in the so-called bond critical point (BCP, the (3, -1) saddle point on electron density curvature) seem to be valuable information for chemists, since it was proven in many papers that the chemical bonding can be characterized and classified on the basis of electron density characteristics measured in BCPs . In this review we firstly give a brief introduction to the theory, explaining most basic terms and dependences. In the main part of the review we discuss application of QTAIM in the qualitative and quantitative analysis of several various noncovalent interactions, focusing readers attention on such aspects as classification of interactions and interaction energy assessment. Both theoretical and experimental approaches are taken into account. We also discuss extensions of QTAIM to the analysis of the so called source function – the method which additionally enlarge interpretative possibilities of its parent theory. Finally, we give some examples which perhaps escape a rigorous QTAIM definition of chemical bonding. We acquaint the potential reader with arguments being pro- and against the QTAIM-based deterministic model of a chemical bond.

5

Strukturalne i elektronowe aspekty wiązania azot–azot

Gajda K., Zarychta B., Ejsmont K.

Chemik

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2014

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Vol. 68, nr 4

363--368

PL

Azot, podobnie jak wiele innych pierwiastków chemicznych, posiada zdolność do katenacji. Największą grupę związków z układami Nx stanowią te, które zawierają dwa atomy azotu, a najliczniejszą wśród nich a najliczniejsze wśród nich to związki –hydrazo, –azo, –azoksy, –azodioksy oraz związki zawierające grupę nitraminową. W prezentowanych badaniach dla ustalenia zmian w długości wiązania azot–azot wyliczono średnie jej wartości na podstawie obliczeń kwantowo-mechanicznych oraz danych z krystalograficznej bazy CSD. Dodatkowo, przy użyciu indeksu aromatyczności HOMA opartego na kryteriach geometrycznyche, wyliczono aromatyczność pierścieni fenylowych związanych z analizowanymi grupami funkcyjnymi.

EN

Nitrogen, like many other chemical elements, has catenation ability. The largest family of compounds containing Nx systems are compounds containing two nitrogen atoms, and the most numerous among them are hydrazo, azo, azoxy, azodioxy compounds and compounds with nitramine group. In the presented studies for determining changes in nitrogennitrogen bond length, average lengths were calculated based on quantum mechanical calculations and data from crystallographic database CSD. Furthermore, the aromaticity of phenyl rings connected to studied functional groups was calculated using HOMA aromaticity index based on geometric criteria.

6

Application of automated interferometric system for investigation of the behaviour of a laser-produced plasma in strong external magnetic fields.

Kasperczuk A., Pisarczyk T.

Optica Applicata

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2001

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Vol. 31, nr 3

571-597

EN

Achievements of the authors in the field of technical and numerical problems of multi-frame interferometry are presented. A three-channel interferometric system with an automatic image processing for laser-produced plasma is described. The measurements of electron density distributions in a plasma generated by a laser and confined by a strong magnetic field (up to 15 T) are the main part of this work. Numerical analysis of interferograms of the plasma and numerical methods of the reconstruction of electron density spatial profiles, both in an axially symmetrical plasma and in a plasma stream of disturbed axial symmetry are presented in more detail.

7

Badania grubości warstwy pośredniej w materiałach porowatych metodą SAXS

Pikus S., Kobylas E.

Archiwum Nauki o Materiałach

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1999

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T. 20, nr 3

177-190

PL

Metodę SAXS zastosowano do wyznaczania grubości warstwy pośredniej w szkłach porowatych pokrytych warstwą dekstranowo-poliiminową. Materiały te rokują nadzieję na powszechne ich wykorzystanie w wielu dziedzinach nauki i przemysłu. Często na swojej powierzchni wykazują istnienie warstwy pośredniej. W pracy szczegółowo omówiono podstawy teoretyczne różnych sposobów analizy efektu SAXS w materiałach z warstwą pośrednią. Wykazano dużą dokładność oznaczania metodą SAXS grubości tej warstwy w badanych materiałach porowatych. Na podstawie uzyskanych wyników badań dwiema metodami wyznaczania grubości warstwy pośredniej dla różnych materiałów stwierdzono, że istnieje wpływ zmian przebiegu gęstości elektronowej w warstwie na dokładność otrzymanych wyników.

EN

A series of porous glasses covered with polysaccharide-polyimine copolymers were studied by SAXS method. These materials can be employed in many fields of science and industry. In the studied materials the transition layer was found on the surface of the polymer. The paper presents the theoretical concepts of the SAXS effect analysis for materials with transition layer. Excellent precision for transition layer thickness estimation by SAXS method was confirmed. The SAXS results of transition layer thickness determination obtained in two different ways allowed to examine the influence of electron density changes in transition layer on the precision of SAXS measurements.