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1

Spectroscopy and Photophysics of Monoazaphenanthrenes II. Ab initio Analysis of Molecular Parameters and Electronic Spectra

100%

Deperasińska I., Prochorow J.

Acta Physica Polonica A

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2003

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vol. 104

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issue 6

601-613

EN

The ground state structures of phenanthrene and its monoaza-deriv atives, phenanthridine and 7,8-benzoquinoline were optimized using the ab initio methods. Both methods of optimization are leading to the results, which are in good agreement with available experimental data. Calculated ground-state electric dipole moments in phenanthridine and 7,8-benzoquinoline were found to have antiparallel orientations, due to the different electronic charge distributions in these molecules. The energies of vertical electronic transitions from the ground to excited singlet states (S_0 → S_n transitions) and the corresponding oscillator strengths were calculated within the framework of configuration interaction-singles and time-dependent density functional theory. The last method was found to be more accurate in reproduction of experimental absorption spectra. Very interesting result of these computations is the change of relative orientation of the transition dipole moments for the two lowest ππ* electronic transition in monoazaphenanthrenes - from perpendicular in phenanthrene molecule to nearly parallel orientation in both monoazaphenanthrenes. The observed changes of molecular parameters and spectra can be related to the inductive effects of the substitution of nitrogen atom into the aromatic skeleton of phenanthrene.

2

Size Dependent Properties of Hollow Gold Nanoparticles: A Theoretical Investigation

80%

Senturk Dalgic S.

Acta Physica Polonica A

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2016

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vol. 129

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issue 4

531-534

EN

A new kind of nanostructures with the negative curvature defined as the hollow ones have recently used in biomedical applications. In this work, an analytic model was developed to compute the size-dependent properties of spherical hollow gold nanoparticles in shell-core-shell configuration. This model has established to calculate the cohesive energies based on the surface energy consideration depending on sizes of inner and outer surfaces of hollow nanoparticles. The size and geometry of the model particles have been obtained by using the stability diagram and the collapsing mechanism was studied by molecular dynamics simulations. The model has been also applied to the hollow particles within unstable and half stable geometry. The predicted results have been compared with each other and those obtained by solid ones. The theoretically predicted size dependent properties are consistent with experimental observations and the hollow quantum dot calculations. Thus, an atomistic insight into the size effect on the cohesive energies of hollow nanoparticles has been presented.

3

The Dependence of the Proton Conductivity on Concentration for Networks with Different Symmetry of Molecules

80%

Masłowski T., Dudek K.

Acta Physica Polonica A

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2017

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vol. 132

|

issue 1

129-131

EN

The one-dimensional numerical model of the proton conductivity in anhydrous solids is used to obtain the conductivity for different values of proton concentration. The model is constructed as a chain of rods or triangles, depending on the symmetry of molecules, linked by hydrogen bonds. An evolution of such system governed by the Grotthuss mechanism is described by means of the kinetic Monte Carlo method. It is shown that in the case of a system with molecules represented by triangles, a decrease in the conductivity corresponds to a significantly broader range of concentrations than is the case for a system constructed by means of rods. This result may prove to be of a potential importance in the case of possible electronic applications. Moreover, for the discussed systems, a strong dependence on the defect formation energies is demonstrated.

4

Seismic Risk Assessment of Historical Eastern Turkish Buildings by Finite Element Analysis

80%

Çarhoglu A., Usta P., Korkmaz K.

Acta Physica Polonica A

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2015

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vol. 127

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issue 4

1083-1085

EN

Traditional masonry buildings, commonly built in Turkey, are one of the important items of cultural heritage. There are many important historical buildings in the east part of Turkey. One of the important locations in east of Turkey is Kilis. In this study, Kilis houses of original types in terms of architectural and functionality, were examined regarding the effects of an earthquake. Therefore, five traditional Kilis houses were examined and the buildings were modeled using SAP2000 finite element software. The models were investigated with different materials such as stone, brick, pumice and cellular concrete material. Time history analyses were performed for the modeled buildings, with three different ground motion records. Displacement values, compressive stresses, tensile stresses, shear stresses and base shear values, obtained from the analysis results were examined in detail. When the results of the study were evaluated, earthquake resistance of buildings was was found to be high and the displacements values were not at a significant level.

5

Fluorescence Spectra of Phenanthridine Isolated in the Supersonic Jet Expansion - An Ab Initio Analysis

80%

Deperasińska I., Prochorow J., Stepanenko Y.

Acta Physica Polonica A

|

2005

|

vol. 108

|

issue 6

1005-1019

EN

Following the analysis of laser induced fluorescence spectrum of 7,8-benzoquinoline molecule, observed under conditions of isolation in the supersonic jet expansion, the ab initio analysis of laser induced fluorescence spectrum of phenanthridine, observed under the same experimental conditions, was performed. This analysis included: optimization of equilibrium geometry of phenanthridine in its first excited S_1 singlet state and computations of the frequencies of vibrational fundamental modes together with their geometry changes between the excited and the ground state. Comparison of the results of calculations with experimental data revealed their good agreement and an increase in the vibrational activity in the fluorescence spectrum in comparison to fluorescence spectrum of phenanthrene molecule (which is a parent aromatic hydrocarbon of phenanthridine and of 7,8-benzoquinoline). Such an increase in vibrational activity in the fluorescence spectrum was earlier observed also for 7,8-benzoquinoline molecule. Present analysis shows that this effect is due to molecular symmetry reduction caused by the substitution of nitrogen atom into the aromatic rings system of phenanthrene, as well as to the changes of equilibrium structure between the ground and excited states.

6

The Structure of Dendrimers with Charged Terminal Groups: Monte Carlo Simulations

80%

Majtyka M., Kłos J.

Acta Physica Polonica A

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2006

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vol. 110

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issue 6

833-843

EN

Taking into account the full Coulomb potential and the excluded volume interactions, properties of dendrimers with generations g = 5, 6 with charged terminal groups and counterions in an athermal solvent are examined by lattice Monte Carlo simulations. The study treats counterions explicitly and focuses on the local structure of the systems inspected by pair correlation functions g_{ab} that provide information on distributions of monomers, terminal groups and ions in space at various temperatures T*. Special emphasis is placed on counterions and their role they play in causing conformational changes of the molecules. The simulations show that counterions penetrate the interior of the dendrimers, and there is a major increase in their concentration there as T* decreases. Some of them condense onto the terminal groups and a reduction in the mean effective charge ⟨Q⟩ of the dendrimers appears. Within the range of temperatures where the condensation (as a function of T*) is sharp the molecules weakly swell up when compared to their size at the other temperatures. This kind of behaviour is also reflected by the distributions of monomers and terminal groups.

7

Quantitative Analysis of Transferred Nuclear Overhauser Effects in Complex Spin Systems by Full Relaxation Matrix Analysis

80%

Czaplicki J., Milon A.

Acta Physica Polonica A

|

2005

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vol. 108

|

issue 1

25-32

EN

A computer program was developed for studying transferred nuclear Overhauser effects in complex spin systems. It permits quantitative analysis of nuclear Overhauser effects observed in biologically important systems, such as ligands interacting with transmembrane receptors in the presence of lipid bilayers. The full generalized relaxation matrix approach takes into account the local mobility, spin equivalence, finite exchange rates, and spectral overlap. The program can be used either to simulate theoretical nuclear Overhauser effect buildup curves or to fit a relaxation matrix of a given model to experimental data. Selected examples illustrate the program's performance.

8

Fluorescence Spectra of 7,8-Benzoquinoline Isolated in the Supersonic Jet Expansion - An Ab Initio Analysis

80%

Deperasińska I., Prochorow J., Stepanenko Y.

Acta Physica Polonica A

|

2004

|

vol. 106

|

issue 4

535-545

EN

The optimized equilibrium geometry of 7,8-benzoquinoline molecule in its first excited, S_1, singlet state was computed with the use of ab initio RCIS/6-31G(d) method. It was found that the electronic transition to the first excited state in 7,8-benzoquinoline is not confined to the neighborhood of nitrogen atom, but is delocalized over entire aromatic rings system, much alike in the molecule of phenanthrene. With the optimized geometry of the ground and excited state of the molecule, the frequencies of the vibrational fundamental modes were computed, together with their displacement parameters (geometry changes of vibrations between the excited and the ground state). These frequencies are in good agreement with vibrational frequencies present in the fluorescence spectrum of 7,8-benzoquinoline observed recently under jet-cooling conditions in supersonic beam expansion. In comparison to the fluorescence spectrum of phenanthrene, the calculated, as well as experimental fluorescence spectra of 7,8-benzoquinoline contain much more vibrational features, and this increased vibronic activity is related to the symmetry break caused by the introduction of N-heteroatom into the aromatic ring system of phenanthrene.

9

Nonequilibrium Effects in a Bimolecular Chemical Reaction in a Dilute Gas

70%

Cukrowski A., Fritzsche S., Popielawski J.

Acta Physica Polonica A

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1993

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vol. 84

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issue 2

369-382

EN

Perturbation solution of the Boltzmann equation for a dilute gas with a chemical reaction A + A → B + B is presented. Analytical results for the nonequilibrium effects on the rate of chemical reaction are obtained for the line-of-centers model. It is shown that taking into account the energy transfer from reagents A to products B permits to get new results. The nonequilibrium corrections obtained from these results are much larger than those obtained with neglecting this energy transfer. These results are verified by a comparison with the numerical results obtained from the modified Nanbu-Babovsky Monte Carlo computer simulations.

10

Computational Material Analysis of Structural and Hemodynamic Model of Coronary Stent by CFD/FEA in Computer Aided Mechanical Engineering Approach

70%

Karaçal Ö.

Acta Physica Polonica A

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2016

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vol. 130

|

issue 1

249-251

EN

With the development of new technologies, it is very popular to use a coronary stent that is a small mesh tube-shaped medical device deployed to treat narrow or weak arteries as part of a procedure called percutaneous coronary intervention. Several aspects, such as stent design, stent wire type, mechanical and material characteristics of stent have different influences on stent intervention. It has not been reported about what impacts on stent struts by the hemodynamic behavior on stent material and very few numerical studies have considered both the mechanical and hemodynamic impact of stent implementation. Computational simulation method for realization of realistic structural and hemodynamic micro environment model in this research provided valuable results of long-term functional knowledge of stent material behavior that are time consuming and expensive to determine otherwise. Computational fluid dynamics and finite element analysis simulation models were investigated and developed to evaluate engineering properties that affect stent functional attributes. These characteristics are dependences of material properties on blood flow conditions such as structural load, shear-strain rate, radial strength, and wall shear stresses, which need to be scientifically explored. To understand the material (Fe-18Cr-14Ni-2.5Mo as stainless steel 316LVM) mechanical performance of the stent, a finite element analysis simulation model was established when exposed to pulsatile blood pressure. In this study, computational fluid dynamics model was generated to calculate the wall shear stresses and strain distribution in stented vessel carrying blood to heart. The analytical analysis of mechanical and hemodynamic conduct of a stent in this investigation may help for better designs of stent, and provide deeper comprehension to support clinical cardiovascular surgeons and guide potential therapeutic strategies.

11

Theory of Translational Energy Relaxation in Binary Mixtures of Dilute Gases with Chemical Reaction

70%

Cukrowski A., Fritzsche S., Popielawski J.

Acta Physica Polonica A

|

1992

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vol. 82

|

issue 6

1005-1022

EN

A simple approach to the process of translational energy relaxation in dilute gases due to Dahler, Malkin, Shizgal and others is extended to the case of systems with chemical reaction. Fundamental quantities characterizing the relaxation processes such as the relaxation time and collision numbers during this time are computed for a number of molecular models of the chemical reaction (the Prigogine-Xhrouet model, the line-of-centers model, a modified line-of-centers model, and reverse versions of these models). Results of this analytical theory are compared with the results of numerical simulations of solutions of the appropriate Boltzmann equation with the use of the modified Nanbu-Babovsky method. This comparison leads to very good agreement between the analytical theory and numerical calculations. A marked influence of the chemical reaction on the translational relaxation in a dilute gas is another important conclusion of this paper.

12

Fullerenes as polyradicals

61%

Sheka E.

Open Physics

|

2004

|

vol. 2

|

issue 1

160-182

EN

We present the investigation of the electronic structure of X60 molecules (X=C, Si), containing 60 odd electrons with spin-dependent interaction between them. Conditions for the electrons to be excluded from the covalent pairing are discussed. A computational spin-polarized quantum-chemical scheme is suggested to evaluate four parameters-energy of radicalization, exchange integral, atom spin density, and squared spin- to characterize the effect quantitatively. A polyradical character of the species, weak for C60 and strong for Si60, is established.

13

Multi-mode ground state interaction terms in C60-based electron donor-acceptor complexes

41%

Sheka E.

Open Physics

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2004

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vol. 2

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issue 2

300-328

EN

Quantum-chemical testing of donor-acceptor properties of binary molecular complexes, related to the singlet state, is suggested as QCh calculations of studied systems and their constituents by using both spin-nondependent (RHF) and spindependent (UHF) versions of the exploited computational tool. The avoided crossing of intermolecular interaction terms of neutral moleculesE int(A 0 B 0) and molecular ionsE int(A + B −) causes a multi-mode character of the ground state term. The dependence of D-A complex properties on the type of the term, space positions of the term minimum, and the interrelation of the corresponding energies are discussed. The suggested approach has been applied to binary complexes C60+X (X=TAE, TDAE, DMMA, COANP, 2Li, Mg).

Refine search results

Spectroscopy and Photophysics of Monoazaphenanthrenes II. Ab initio Analysis of Molecular Parameters and Electronic Spectra

Size Dependent Properties of Hollow Gold Nanoparticles: A Theoretical Investigation

The Dependence of the Proton Conductivity on Concentration for Networks with Different Symmetry of Molecules

Seismic Risk Assessment of Historical Eastern Turkish Buildings by Finite Element Analysis

Fluorescence Spectra of Phenanthridine Isolated in the Supersonic Jet Expansion - An Ab Initio Analysis

The Structure of Dendrimers with Charged Terminal Groups: Monte Carlo Simulations

Quantitative Analysis of Transferred Nuclear Overhauser Effects in Complex Spin Systems by Full Relaxation Matrix Analysis

Fluorescence Spectra of 7,8-Benzoquinoline Isolated in the Supersonic Jet Expansion - An Ab Initio Analysis

Nonequilibrium Effects in a Bimolecular Chemical Reaction in a Dilute Gas

Computational Material Analysis of Structural and Hemodynamic Model of Coronary Stent by CFD/FEA in Computer Aided Mechanical Engineering Approach

Theory of Translational Energy Relaxation in Binary Mixtures of Dilute Gases with Chemical Reaction

Fullerenes as polyradicals

Multi-mode ground state interaction terms in C60-based electron donor-acceptor complexes