Search results for: Krzysztof Wojciechowski

Items from 1 to 20 out of 48 results

article

Prediction of photofading of N‐β‐hydroxyethylamino‐o‐nitrophenyl derivatives: a theoretical study

Krzysztof Wojciechowski, Lucjan Szuster

Coloration Technology > 137 > 2 > 134 - 144

Until now, the lightfastness of hair dyes had not been investigated using all‐valence molecular orbital methods. The results of calculations are used to obtain the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) frontier electron density, which can reflect the propensity for electrophilic or nucleophilic attack at an atom in a molecule. Using semi‐empirical...

article

Intermolecular interactions for two chosen anthracene derivatives

Sylwester Kania, Janusz Kuliński, Barbara Kościelniak-Mucha, Piotr Słoma, more

Scientific Bulletin. Physics / Lodz University of Technology > 2021 > Vol. 42 > 5--12

The nature of intermolecular interactions for anthrone and anthraquinone differs due to the symmetry of substitution of the central benzene ring, i.e. anthrone substituted with only one keto group and anthraquinone substituted with two keto groups. In order to interpret the interactions among the molecules, the interaction energies between molecules in crystals were calculated using DFT B3LYP calculations...

article

Volume conductivity of polycrystalline tetracene and p-quaterphenyl layers modified under influence of the surface adsorption

Sylwester Kania, Janusz Kuliński, Barbara Kościelniak-Mucha, Piotr Słoma, more

Scientific Bulletin. Physics / Lodz University of Technology > 2021 > Vol. 42 > 13--31

Volume conductivity of thin organic layers in contact with the ambient atmosphere depends on the volume properties and on the adsorption processes on the free surface of the layer. In order to clarify the role of the surface, experiments were carried out at a temperature close to 293 K to determine the influence of the adsorption dynamics on the change of characteristic relationships observed for...

article

A DFT study of reorganization energy of some chosen carbazole derivatives

Sylwester Kania, Barbara Kościelniak-Mucha, Janusz Kuliński, Piotr Słoma, more

Scientific Bulletin. Physics / Lodz University of Technology > 2020 > Vol. 41 > 33--42

Strong efforts toward finding an organic semiconductor with a molecule characterized by a low charge transfer energy applying quantum-chemical calculations are undertaken. Density Functional Theory (DFT) calculations made for carbazole (Cz) and three isomers of benzocarbazole, benzo (a) carbazole (BaCz), benzo (b) carbazole (BbCz) and benzo (c) carbazole (BcCz) proves the possibility of lacking the...

article

Charge carrier mobility in non-equilibrated transport in molecular materials

Sylwester Kania, Barbara Kościelniak-Mucha, Janusz Kuliński, Piotr Słoma, more

Scientific Bulletin. Physics / Lodz University of Technology > 2019 > Vol. 40 > 37--46

Non-equilibrated transport of charge carriers in the molecular material depends on the structure and packing of the molecules. Explanation of the measurements of the photocurrent generated with use of UV flash light in organic layer needs to define the quantity of charge carriers mobility. Definition of this quantity in the scope of some defined transport model requires the detailed analysis of generation,...

article

Polarization of organic aromatic molecule in anionic and cationic state

Sylwester Kania, Barbara Kościelniak-Mucha, Janusz Kuliński, Piotr Słoma, more

Scientific Bulletin. Physics / Lodz University of Technology > 2019 > Vol. 40 > 27--35

The modification of electron states and the change in the geometry of the structure of molecule during hopping transport of charge carriers depends on the symmetry of the molecule. During electric transport the molecule reversibly transforms from neutral state to cation when hole conductivity occurs or to anion when electron conductivity occurs. The energies of orbitals HOMO and HOMO-1 of anthrone...

article

Analysis of the fins geometry of a hot-side heat exchanger on the performance parameters of a thermoelectric generation system

Marcin Borcuch, Michał Musiał, Stanisław Gumuła, Karol Sztekler, more

Applied Thermal Engineering > 2017 > 127 > C > 1355-1363

This paper presents the influence of hot-side heat exchanger (HHX) design on the operational parameters of a thermoelectric generator (TEG). The approach is comprehensive, power needs due to pressure losses in the device are accounted for the analysis. The TEG used in the installation always requires additional power to overcome pressure drops. This directly influences the net generated power of the...

article

Thermoelectric properties of Sn doped BiCuSeO

Sayan Das, Raju Chetty, Krzysztof Wojciechowski, Satyam Suwas, more

Applied Surface Science > 2017 > 418 > PA > 238-245

BiCuSeO and Bi_1-xSn_xCuSeO (x=0.02, 0.04, 0.06, 0.08) were prepared by a two-step solid state synthesis. The phase purity and the crystal structure were investigated by the X-Ray Diffraction (XRD) and confirmed by Energy Dispersive Spectroscopy (EDS). The volatilization of Bi and Bi₂O₃ lead to off-stoichiometry of the main phase and the formation of CuSe₂ secondary phase in the undoped sample. SnO₂...

article

The current state of steppe perennial plants populations: A case study on Iris pumila

Ivan Yu. Parnikoza, Igor O. Andreev, Olena M. Bublyk, Kateryna V. Spiridonova, more

Biologia > 2017 > 72 > 1 > 24-35

A comprehensive study of a typical steppe perennial Iris pumila L. were carried out in the central zone of the European part of this species’ range, namely in Ukraine. Intraspecific differentiation, population size and isolation degree and its consequences, the threat of human impact were analyzed, as well as ecological amplitude and genetic variation in ISSR markers and selected chloroplast regions...

article

Simple synthesis of 4-cyanoquinoline N-oxides

Robert Bujok, Zbigniew Wróbel, Krzysztof Wojciechowski

Tetrahedron Letters > 2016 > 57 > 9 > 1014-1018

4-Cyanoquinoline-N-oxides were obtained in the reactions of 2-nitrobenzylcyanide carbanions with acrylonitrile.

chapter

Stochastically Incomplete Manifolds and Graphs

Radosław Krzysztof Wojciechowski

Progress in Probability > Random Walks, Boundaries and Spectra > 163-179

We survey geometric properties which imply the stochastic incompleteness of the minimal diffusion process associated to the Laplacian on manifolds and graphs. In particular, we completely characterize stochastic incompleteness for spherically symmetric graphs and show that, in contrast to the case of Riemannian manifolds, there exist examples of stochastically incomplete graphs of polynomial volume...

article

A Multi-Point Measurement Method for Thermal Characterization of Foil Bearings Using Customized Thermocouples

Michał Lubieniecki, Jakub Roemer, Adam Martowicz, Krzysztof Wojciechowski, more

Journal of Electronic Materials > 2016 > 45 > 3 > 1473-1477

Gas foil bearings have become widespread covering the applications of micro-turbines, motors, compressors, and turbocharges, prevalently of small size. The specific construction of the bearing, despite all of its advantages, makes it vulnerable to a local difference in heat generation rates that can be extremely detrimental. The developing thermal gradients may lead to thermal runaway or seizure that...

article

Influence of Sedimentation of Atoms on Structural and Thermoelectric Properties of Bi-Sb Alloys

Kamila Januszko, Artur Stabrawa, Yudai Ogata, Makoto Tokuda, more

Journal of Electronic Materials > 2016 > 45 > 3 > 1947-1955

Functionally graded thermoelectric materials (FGTMs) have been prepared by sedimentation of atoms under a strong gravitational field. Starting samples of Bi_xSb_1−x alloys with different composition x were synthesized by melting of metals and subsequent annealing of quenched samples. The thermoelectric properties (Seebeck coefficient, electrical conductivity) of the...

article

Theoretical and Experimental Study on Thermoelectric Properties of Ba₈TM_xGa_yGe_46–x–y (TM = Zn, Cu, Ag) Type I Clathrates

Juliusz Leszczynski, Andrzej Kolezynski, Jarosław Juraszek, Krzysztof Wojciechowski

Journal of Electronic Materials > 2016 > 45 > 10 > 5264-5278

In the type I clathrates Ba₈TM_xGa_yGe_46–x–y (TM = group 10 to 12 elements) where some of the Ge framework atoms are substituted by Zn, Cu or Ag, the transition-metal elements prefer to occupy the 6c site. Preliminary band-structure calculations showed that this substitution implies modification of the electronic bands in the vicinity of the...

article

Synthesis of 4-(4-toluenesulfonyl)quinolines from nitroarenes and allyl sulfones using step-by-step procedure

Karolina Anczkiewicz, Magdalena Królikiewicz, Zbigniew Wróbel, Krzysztof Wojciechowski

Tetrahedron > 2015 > 71 > 23 > 3924-3931

σ^H-Adducts formed from nitroarenes and allyl tolyl sulfone carbanions when treated with silylating agents transform into 4-toluenesulfonyl quinolines.

article

General synthesis of 2,1-benzisoxazoles (anthranils) from nitroarenes and benzylic C–H acids in aprotic media promoted by combination of strong bases and silylating agents

Michał Wiȩcław, Mariusz Bobin, Andrzej Kwast, Robert Bujok, more

Molecular Diversity > 2015 > 19 > 4 > 807-816

Carbanions of phenylacetonitriles, benzyl sulfones, and dialkyl benzylphosphonates add nitroarenes at the ortho-position to the nitro group to form $$\sigma ^\mathrm{H}$$ σ H -adducts that, upon treatment with trialkylchlorosilane and additional base (t-BuOK or DBU), transform into 3-aryl-2,1-benzisoxazoles in moderate-to-good yields.

article

Thermoelectric Generator with an Active Load

John Stockholm, Krzysztof Wojciechowski, Juliusz Leszczynski, Krzysztof Witek, more

Materials Today: Proceedings > 2015 > 2 > 2 > 744-750

Claims have been made, that a thermoelectric generator, with an active load, can havea conversion efficiency over two times the thermoelectric efficiency of a DC operated thermoelectric generator. Theoretical studies of pulsed systems and experimental work are reviewed. Theoretical aspects are presented that can explain the high conversion, the theory proposed by Apostolis given. Two experimental...

article

Application of nucleophilic substitution of hydrogen in nitroarenes to the chemistry of indoles

Mieczysław Mąkosza, Krzysztof Wojciechowski

Chemistry of Heterocyclic Compounds > 2015 > 51 > 3 > 210-222

Application of nucleophilic substitution of hydrogen in nitroarenes to the synthesis and transformation of indoles is discussed.

article

Naturalized dyes — A way to increase susceptibility for microbiological degradation

Małgorzata Piotrowska, Agnieszka Szymczak, Krzysztof Wojciechowski

Biotechnology and Bioprocess Engineering > 2015 > 20 > 1 > 100-108

Aim of the study was the determination of the influence of the D -gluconic acid and its acetyl derivative (2,3,4,5,6-penta- O -acetyl- D -gluconic acid) on microbiological degradation in aerobic conditions of azo dyes (Schäffer salt and I acid derivatives). The rest of the aldonic acid and its acetylated form in the structure of azo dye play a role of an...

article

Dyeing properties of CI Acid Blue 193 and the non‐equivalent properties of CI Acid Black 194 produced by different manufacturers

Krzysztof Wojciechowski, Lucjan Szuster, Joanna Rutowicz, Anna Kaminska

Coloration Technology > 130 > 3 > 215 - 220

This paper presents the results of research conducted into the colour properties of commercial metal complex dyes CI Acid Blue 193 and CI Acid Black 194. Three chromium(III) complexes with different colours were identified using thin‐layer chromatographic analysis and then separated by preparative chromatography. It was found that colour differences of the examined dyes depend on the ratio of the...

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INFONA - science communication portal

Search results for: Krzysztof Wojciechowski

Prediction of photofading of N‐β‐hydroxyethylamino‐o‐nitrophenyl derivatives: a theoretical study

Intermolecular interactions for two chosen anthracene derivatives

Volume conductivity of polycrystalline tetracene and p-quaterphenyl layers modified under influence of the surface adsorption

A DFT study of reorganization energy of some chosen carbazole derivatives

Charge carrier mobility in non-equilibrated transport in molecular materials

Polarization of organic aromatic molecule in anionic and cationic state

Analysis of the fins geometry of a hot-side heat exchanger on the performance parameters of a thermoelectric generation system

Thermoelectric properties of Sn doped BiCuSeO

The current state of steppe perennial plants populations: A case study on Iris pumila

Simple synthesis of 4-cyanoquinoline N-oxides

Stochastically Incomplete Manifolds and Graphs

A Multi-Point Measurement Method for Thermal Characterization of Foil Bearings Using Customized Thermocouples

Influence of Sedimentation of Atoms on Structural and Thermoelectric Properties of Bi-Sb Alloys

Theoretical and Experimental Study on Thermoelectric Properties of Ba₈TM_xGa_yGe_46–x–y (TM = Zn, Cu, Ag) Type I Clathrates

Synthesis of 4-(4-toluenesulfonyl)quinolines from nitroarenes and allyl sulfones using step-by-step procedure

General synthesis of 2,1-benzisoxazoles (anthranils) from nitroarenes and benzylic C–H acids in aprotic media promoted by combination of strong bases and silylating agents

Thermoelectric Generator with an Active Load

Application of nucleophilic substitution of hydrogen in nitroarenes to the chemistry of indoles

Naturalized dyes — A way to increase susceptibility for microbiological degradation

Dyeing properties of CI Acid Blue 193 and the non‐equivalent properties of CI Acid Black 194 produced by different manufacturers

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