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1
Content available remote

Colloidal Trajectories in Two-Dimensional Light-Induced Quasicrystals with 14-Fold Symmetry due to Phasonic Drifts

100%
Martinsons M., Sandbrink M., Schmiedeberg M.
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vol. 126
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issue 2
568-571
EN
Quasicrystals are structures that are not periodic but possess a long range positional order. They can have any rotational symmetry including those that are forbidden in periodic crystals. The symmetry is classified by the point group and the rank D. In quasicrystals, phasons as additional hydrodynamic modes cause correlated rearrangements of the particles. The number of phasonic degrees of freedom depends on the rank. For colloidal quasicrystals that are induced by laser fields, specific phasonic displacements can be realized by changing the phases of the laser beams in a well-determined way. The arising trajectories of colloids in two-dimensional light-induced colloidal quasicrystals with rank D=4 have already been analyzed in detail. Here, we analyze the colloidal trajectories in two-dimensional quasicrystals with 14-fold symmetry having rank D=6. We observe complex paths of the colloids consisting of straight and winding lines as well as jumps.
2
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Activation of Silver Colloids for Enhancement of Raman Scattering

80%
Kruszewski S., Cyrankiewicz M.
Acta Physica Polonica A
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2011
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vol. 119
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issue 6A
1018-1022
EN
Obtaining of systems that provide ever-increasing enhancement of the Raman scattered light is a big challenge. The silver colloids obtained by reduction of silver nitrate by trisodium citrate are the most promising enhancement systems. Nanoparticles of silver forming fresh colloid obtained by this way exhibit in extinction spectrum the absorption band proving of the surface plasmons excitation, but do not enhance the Raman scattered light, are not surface enhanced Raman scattering active. Adding of KCl or HNO_3 causes the surface enhanced Raman scattering activation, i.e. causes that the conditions for aggregation of nanoparticles and for adsorption on their surface of molecules providing Raman scattering are created. Increasing amount of added KCl or HNO_3 leads to significant changes in the extinction spectrum and to significant increase in intensity of surface enhanced Raman scattering. The observed changes in extinction spectrum are mainly due to progressive aggregations of nanoparticles. In junctions between nanoparticles existing inside aggregates the condition for single molecule surface enhanced Raman scattering are fulfilled and therefore aggregation leads to increase in average surface enhanced Raman scattering intensity. Silver colloid activated by using KCl provides about 10-fold higher surface enhanced Raman scattering than that treated with HNO_3.
3
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The Silver Colloidal Solutions and Films for Efficient SERS

80%
Górska A., Meyer S., Balter A.
Acta Physica Polonica A
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2012
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vol. 122
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issue 2
350-352
EN
The silver colloids and silver films are known for their signal enhancing properties in Raman spectroscopy. Surface enhanced raman spectroscopy is a very useful tool to detect molecules at low concentration or even single molecules in examined samples. Here we present a study on the preparation of silver colloidal solution and deposition of silver films on mica. The colloidal solutions were examined by two methods: the UV-VIS spectroscopy to determine their optical properties and atomic force microscopy to determine the size of the particles and structure of the deposited films. The crystal violet (tris(4-(dimethylamino)phenyl)methylium chloride) solution was used as a test sample for evaluation of enhancing properties of silver colloidal solutions and films. These experiments have shown that both colloidal solutions and films, are efficient surface enhanced raman spectroscopy substrates, therefore they can be used in further studies for enhancement of the Raman signal of biopolymers, f.e. polysaccharides and DNA.
4
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Phase States in Potassium Oleate+Water and Potassium Oleate+Water+Decanol Lyotropic Systems

80%
Nesrullajev A., Kazanci N., Yildiz T.
Acta Physica Polonica A
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1998
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vol. 94
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issue 1
25-32
EN
In this work the investigations of the characteristic textures and the dynamics of their concentration and temperature transformations in potassium oleate+water lyotropic system have been carried out. The effect of the decanol on lyotropic mesomorphism as well as on the character of typical textures and the concentration ranges of lyotropic liquid crystalline mesophases have also been studied. The phase states diagrams of the potassium oleate+water and potassium oleate+decanol+water lyotropic liquid crystalline systems are presented.
5
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Temperature Dependence of a Dielectric Relaxation in Weakly Polar Ferrofluids

80%
Rajňák M., Kurimský J., Dolník B., Cimbala R., Paulovičová K., Kopčanský P., Timko M.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
943-945
EN
In this paper, we report on the temperature dependent broadband dielectric response of a ferrofluid based on transformer oil and magnetite nanoparticles covered with oleic acid molecules. For that purpose the method of dielectric spectroscopy has been chosen in the frequency range from 20 Hz up to 100 kHz. The experiments were carried out on thin film ferrofluid samples confined in a glass plate capacitor containing indium tin oxide (ITO) plate electrodes. The obtained complex permittivity spectrum shows a pronounced dielectric dispersion in the low frequency range. Taking into account the ferrofluid composition we associate this relaxation with ion impurity polarization at the nanoparticle-oil interface. The strong temperature dependence of the relaxation process has been found when conducting the experiments in the temperature range from 298 K to 358 K. The relaxation time of the revealed process exhibits a typical Arrhenius behavior. Based on the conducted experiments and analysis, we propose some reasonable practical applications of the studied ferrofluid in the field of electrical engineering.
6
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Peculiarities of the Schlieren Textures in Lyotropic Nematic Mesophases

80%
Nesrullajev A., Kazanci N.
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vol. 95
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issue 6
931-937
EN
In the present paper the peculiarities of schlieren textures of lyotropic nematic mesophases have been investigated by polythermic polarization microscopy and capillary temperature wedge methods. The lyotropic nematiccalamitics (N_{c}) and lyotropic nematic-discotics (N_{d}) formed in binary and ternary systems on the base of tetradecyldimethyl amino bromide and tetradecyldimethyl amino oxide have been the subjects of our investigations. The dynamics of time and temperature transformations of schlieren textures have been studied. The comparative estimation of schlieren textures of N_{c} and N_{d} mesophases has been performed. The optical force and optical sign of the schlieren textures observed have been determined.
7
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IR and Raman Investigation of Some Poly(acrylic) Acid Gels in Aqueous and Neutralized State

80%
Todica M., Stefan R., Pop C., Olar L.
Acta Physica Polonica A
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2015
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vol. 128
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issue 1
128-135
EN
The modification of local polymeric conformation of poly(acrylic) acid (PAA), induced by hydration and neutralization with triethanol amine (TEA), was investigated by IR and Raman spectroscopy. The effect of water is the perturbation of hydrogen bonds established between different polymeric chains and the modification of the local conformation of the polymer. The neutralization with TEA affects the carboxylic groups and modifies the local conformation of the polymer. These modifications are correlated with the shift and the modification of the characteristics of IR and Raman spectra.
8
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The Role of TiO₂ Nanoparticles on the UV Protection Ability and Hydrophilicity of Polyamide Fabrics

80%
Fakin D., Stana Kleinschek K., Ojstršek A.
Acta Physica Polonica A
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2015
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vol. 127
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issue 4
943-946
EN
The focus of this study was to characterize three industrially-prepared (via the sulphate synthesis process) nano-TiO₂ colloidal dispersions with the intention to elucidate their role on the hydrophilicity as well as UV shielding ability when applied onto polyamide fabric. Transmission electron microscopy (TEM) and UV spectrophotometry of the selected dispersions proved the presence of TiO₂ nanoparticles of different shapes and sizes, as well as its imposing absorption capability within the UV region. In addition, TiO₂ dispersions in three concentrations accompanied by selected chemicals and auxiliaries were applied on polyamide fabrics according to standard exhaustion procedure. Scanning electron microscopy (SEM) was adopted in order to analyse the morphological structure of nano-TiO₂-upgraded PA fabrics. Furthermore, the UV-protective ability and hydrophilic properties were evaluated. The gained results show excellent blocking properties against UV-rays (UPF 50+), as well as the (super)hydrophilicity of TiO₂-modified PA fabrics, regarding the type of employed TiO₂ colloidal dispersion.
9
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Fabrication of Superhydrophilic Polyester Fabrics Using Various TiO₂ Colloidal Dispersions

80%
Ojstršek A., Kurečič M., Fakin D.
Acta Physica Polonica A
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2015
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vol. 127
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issue 4
953-956
EN
The purpose of this research was to apply four stable colloidal dispersions, combining different TiO₂ core-shell nanoparticles, onto polyester fabric, according to exhaustion procedure, in order to enhance fabrics' water and moisture absorption properties. Firstly, all colloidal dispersions were analysed using transmission electron microscopy (TEM) and dynamic light scattering (DLS) and secondly, the morphologies of TiO₂ modified PES surfaces were evaluated by scanning electron microscopy (SEM). In addition, the superhydrophilic character of fibrous surfaces was investigated by water contact angle measurement. For this purpose, dynamic tensiometry was employed by measuring the changes in the net force on a surface during the repeated immersion and emersion of a solid into a probe liquid. The obtained results show excellent wettability of TiO₂ upgraded PES fabrics depending on the type of applied nano-sized TiO₂-hybride.
10
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Content available

Dispersion and Absorption of Longitudinal Electro-Kinetic Waves in Magnetized Ion-Implanted Semiconductor Plasmas

80%
Ghosh S., Thakur P.
Acta Physica Polonica A
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2007
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vol. 111
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issue 2
247-256
EN
The instability of longitudinal electro-kinetic wave that is propagating across the magnetic field B_0 in ion-implanted group-IV semiconductor sample consisting of non-drifting electrons, holes, and negatively charged colloids is investigated. Using hydrodynamic approach, a compact dispersion relation D(ω,k) is derived for the same. The propagation and amplification characteristics of the wave in collision dominated regime are studied numerically in detail for slow and fast modes. Results show that the presence of transverse magnetic field is responsible for the modification of the existing wave spectra of the slow electro-kinetic branch. In case of fast electro-kinetic wave, the presence of magnetic field is found responsible for excitation and amplification of a new mode. It is also found that the magnetic field is responsible for the conversion of two existing aperiodic modes into periodic ones. These novel periodic modes are found to be counter-propagating in nature.
11
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Algorithm for Preliminary Analysis of Viscosity Behaviour of Some Aqueous Poly(ethylene oxide) Gels

80%
Todica M., Pop C., Udrescu L., Pop M.
Acta Physica Polonica A
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2011
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vol. 119
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issue 6
880-884
EN
The dependence of the viscosity on temperature and shear rate was observed for some poly(ethylene oxide) gels with different polymeric concentrations. An algorithm of analysis of experimental data, based on the Arrhenius and power law models, and a mathematical function describing the dependence of the viscosity on temperature and shear rate are proposed.
12
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Hydrodynamic Memory in the Motion of Charged Brownian Particles across the Magnetic Field

80%
Tóthová J., Lisý V.
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issue 5
1051-1053
EN
An exact solution of the Langevin equation is given for a charged Brownian particle driven in an incompressible fluid by the magnetic field, taking into account the hydrodynamic aftereffect. The stochastic integro-differential Langevin equation is converted to a deterministic equation for the particle mean square displacement. We have found the mean square displacement and other time correlation functions describing the particle motion. For the motion along the field the known results from the theory of the hydrodynamic motion of a free Brownian particle are recovered. The correlation functions across the field contain at long times the familiar Einstein terms and additional algebraic tails. The longest-lived tail in the mean square displacement is proportional to t^{1/2}. At short times the motion is ballistic and independent of the magnetic field.
13
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Structure and Dynamics of Colloidal Suspensions Studied by Means of XPCS

80%
Patkowski A., Gapinski J., Fluerasu A., Holmqvist P., Meier G., Lettinga M., Nägele G.
Acta Physica Polonica A
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2008
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vol. 114
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issue 2
339-350
EN
Structure and dynamics of suspensions of charged colloidal spheres in water were studied by means of small-angle X-ray scattering and X-ray photon correlation spectroscopy using synchrotron radiation. Experimentally obtained dependences on the scattering vector q of the structure factor S(q), short-time collective diffusion coefficient D(q) and hydrodynamic function H(q) were in good agreement with theoretical predictions. No effect of screening of the hydrodynamic interactions, suggested in the literature, was found. The conditions are discussed at which the maximum of the hydrodynamic function peak value H(q_m) can be obtained experimentally.
14
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Effect of Magnetic Field on the Fluctuations of Charged Oscillators in Viscoelastic Fluids

80%
Lisý V., Tóthová J.
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vol. 126
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issue 1
413-414
EN
In the present work the generalized Langevin equation is solved for the motion of a charged Brownian oscillator in a magnetic field, when the thermal random force is exponentially correlated in the time. This model is consistent with the assumption that the medium has weakly viscoelastic properties. The velocity autocorrelation function, time-dependent diffusion coefficient and mean square displacement of the particle have been calculated. Our solutions generalize the previous results from the literature and are obtained in a way applicable to other problems of the Brownian motion with memory.
15
Publication available in full text mode
Content available

Optical Properties of Human Blood Sediment

80%
Grzegorzewski B., Kowalińska E.
Acta Physica Polonica A
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2002
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vol. 101
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issue 1
201-209
EN
The formation of human blood sediment by means of optical method was studied. Light was transmitted through a layer of blood. The temporal changes of the transmitted light intensity along the sample were measured. Samples of blood from a healthy donor were investigated. The optical method permits us to distinguish three phases of the blood sediment. At the top of the container the well-known supernatant plasma layer creates. In the sediment of the red blood two phases were distinguished. The rouleau formation phase and the phase of demixed blood were found. The two phases are separated by the moving boundary. The kinetics of this boundary was determined. The optical data admit to a hypothesis about the physical phenomena of the sedimentation process. The spinodal decomposition may be one of the mechanisms of the blood sediment formation.
16
Publication available in full text mode
Content available

Effect of Density Gradient on the Acousto-Electric Wave Instability in Ion-Implanted Semiconductor Plasmas

80%
Ghosh S., Khare P.
Acta Physica Polonica A
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2006
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vol. 109
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issue 2
187-197
EN
Using hydrodynamic model of inhomogeneous plasma, an analytical investigation of excitation of acousto-electric mode was made in n-type piezoelectric ion-implanted semiconductor plasma. By employing the multi-fluid balance equations along with the elastic and Maxwell equations, a compact dispersion relation for the cases in which colloidal grains are either stationary (ϑ_{0d}=0) or streaming (ϑ_{0d}≢0$) is derived. We find that the choice of homogeneous medium is favorable in achieving higher acoustic gain per radian and the results of the investigation should be useful in understanding the characteristics of longitudinal acousto-electric wave in ion-implanted piezoelectric semiconductor whose main constituents are electrons and negatively charged colloidal particles.
17
Publication available in full text mode
Content available

The Numerical Solution of the Imaginary-Axis Eliashberg Equations

80%
Szczęśniak R.
Acta Physica Polonica A
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2006
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vol. 109
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issue 2
179-186
EN
In the paper, we solve the imaginary-axis Eliashberg equations. We calculate numerically self-consistently the superconducting order function, the wave function renormalization factor, and the energy shift function as a function of the Matsubara frequency. We consider different values of the average number of the electrons per lattice site. Additionally, we study the temperature dependence of the order function and the wave function renormalization factor. The possible extension of the Eliashberg theory to the case of the high-T_C superconductors was also briefly discussed.
18
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Generation of Fe₃O₄ Nanoparticle Aggregates in a Ferrofluid Driven by External Electric Field

70%
Kurimský J., Rajňák M., Cimbala R., Paulovičová K., Timko M., Kopčanský P., Kolcun M., Kosterec M., Kruželák L.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
907-909
EN
In the paper the experimental study of magnetic nanoparticle aggregation in a transformer oil based ferrofluid driven by an external electric field is reported. The studied ferrofluid was composed of the magnetite nanoparticles, oleic acid surfactant, and transformer oil. Generally, it is considered that superparamagnetic nanoparticles do not interact in the absence of external magnetic field. In the paper we present an experimental observation of the particle assembly formation in a direct current external electric field by optical microscopy. During the observation no external magnetic field was applied. A diluted low-polarity ferrofluid drop on a glass surface was exposed to the external static inhomogeneous electric field. It is assumed that induced dipole-dipole interaction and subsequent dielectrophoretic motion give rise to the electrohydrodynamic flow in the fluid after a certain time period. As a result, a visible particle chain was formed at the drop electrical equator. This demonstration is expected to contribute to the understanding of the streamer formation and electrical breakdown in transformer oil based ferrofluids.
19
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Ultrasound Frequency Analysis of a Magnetic Fluid in Low-Intensity External Magnetic Field

70%
Kurimský J., Rajňák M., Cimbala R., Dolník B., Tóthová J., Paulovičová K., Timko M., Kopčanský P., Kolcunová I., Petráš J., Džmura J., Balogh J.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
910-912
EN
This work deals with an interaction of a magnetic fluid of a dielectric nature with a magnetic field by means of ultrasound waves measurements and analysis. Ultrasound analysis is known as a non-destructive inspection tool often used in technical diagnostics, moreover, it has numerous applications in medicine and biology, too. We report the low-frequency ultrasound analysis of a dielectric magnetic fluid in a low-intensity external static magnetic field. The studied magnetic fluid was composed of a transformer oil and dispersed magnetite nanoparticles coated with oleic acid. Experiments were carried out by using an ultrasonic testing cell. The cell was exposed to a magnetic field of 50 mT in both parallel and perpendicular direction to the waves propagation. A through-transmission mode measurement was applied, where two fixed narrow-band transducers with completely shielded crystal for maximum RFI/EMI immunity (Physical Acoustic R15I-AST, the resonant frequency 150 kHz) served as a transmitter and a receiver. In this way we carried out the measurement of the frequency-dependent ultrasonic response to a rectangle calibrating signal of 5 μs pulse width. Digitized signals were recorded for further analysis. We present the frequency domain analysis of the low-frequency ultrasound in magnetic fluid. The frequency spectrum in magnetic fluid colloidal system was calculated by the Fourier transformation method. Results show that there is a frequency shift in the amplitude-frequency spectrum caused by the step-up magnetic field. The higher the magnetic field, the higher the frequency of the peaks. The effect of particle aggregation in magnetic field on the ultrasound wave propagation is discussed in the paper.
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