ORCID Profile
0000-0003-3431-6815
Current Organisations
Royal Brisbane and Women's Hospital
,
University of Queensland
,
St. Kliment Ohridski University
,
University of Melbourne
,
Australasian Society for Ultrasound in Medicine
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Publisher: Elsevier BV
Date: 05-1997
Publisher: Pleiades Publishing Ltd
Date: 22-03-2013
Publisher: Unpublished
Date: 2014
Publisher: American Physical Society (APS)
Date: 12-09-2008
Publisher: Elsevier BV
Date: 1998
Publisher: Unpublished
Date: 2015
Publisher: World Scientific Pub Co Pte Ltd
Date: 06-12-2022
DOI: 10.1142/S0219477522500249
Abstract: In this paper, the Schrödinger equation is solved for many free particles and their quantum entanglement is studied via correlation analysis. Converting the Schrödinger equation in the Madelung hydrodynamic-like form, the quantum mechanics is extended to open quantum systems by adding Ohmic friction forces. The dissipative evolution confirms the correlation decay over time, but a new integral of motion is discovered, being appropriate for storing everlasting quantum information.
Publisher: Elsevier BV
Date: 04-2008
Publisher: Biomedical Research Network, LLC
Date: 04-10-2021
Publisher: Royal Society of Chemistry (RSC)
Date: 2002
DOI: 10.1039/B207965H
Publisher: Royal Society of Chemistry (RSC)
Date: 2005
DOI: 10.1039/B501760M
Abstract: We have measured the surface tension and the capillary wave spectra at the liquid/vapour interface of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate at various temperatures up to 400 K. From the weak temperature dependence of the surface tension a low value of the surface excess entropy of approximately 3.5 x 10(5) J K(-1) m(-2) results which is consistent with a strongly aligned surface layer of imidazolium cations previously predicted by MD-calculations. The capillary wave spectra recorded at different wave numbers in the range 170 cm(-1) < or = q < or =500 cm(-1) exhibit strong deviations from the behaviour expected for the free surface of simple liquids. With an extended dispersion relation including the contributions of surface dipole moment density gamma and shear surface excess viscosity mu the spectra have been analyzed. It is found that mu is negligibly small, whereas gamma substantially influences the capillary wave spectra. The electrostatic potential across the interface, which corresponds to the measured dipole moment densities, qualitatively agrees with simulation calculations. The distinct temperature dependence of gamma suggests that with increasing temperature an order-disorder transformation occurs in the surface layer.
Publisher: Springer Science and Business Media LLC
Date: 02-06-2009
Publisher: Springer Science and Business Media LLC
Date: 10-12-2008
Publisher: Elsevier BV
Date: 08-2018
Publisher: Royal Society of Chemistry (RSC)
Date: 1997
DOI: 10.1039/A607594K
Publisher: American Chemical Society (ACS)
Date: 04-1992
DOI: 10.1021/J100187A051
Publisher: IOP Publishing
Date: 27-06-2018
Publisher: AIP Publishing
Date: 03-1994
DOI: 10.1063/1.466369
Abstract: In the present paper the stochastic dynamics of a hydrocarbon molecule moving in a solid body is examined and a generalized Langevin equation which describes the evolution of the coordinate of its center of mass is derived when the molecule behaves as a linear rigid one. An explicit expression for the friction tensor is obtained which accounts both for the molecule–solid interaction and for the thermal vibrations of the lattice of the solid. The diffusion coefficient D of the hydrocarbon molecule is calculated as a function of the number N of the carbon atoms it contains. D exhibits a periodic dependence on N, with maxima when the length of the molecule is an integer multiple of the length of the repeating unit of the lattice and minima when it is a half integer, phenomenon which could be called resonant diffusion. The results are compared with the experimental data for the diffusion of n-paraffins through zeolite T and a qualitative agreement is observed.
Publisher: Elsevier BV
Date: 06-2005
DOI: 10.1016/J.CIS.2004.07.011
Abstract: Some theoretical methods for description of the diffusion on modulated surfaces are reviewed. A general formula for calculation of the diffusion coefficient of a particle moving in the field of a periodic potential is developed, which takes into account both the potential barrier effect and the dependence of the friction coefficient on the potential. The application of the theory to the diffusion of dimers on solid surfaces reveals a non-monotonous dependence of the diffusion coefficient on the ratio between the dimer and solid spatial parameters. This resonant dependence sometimes can be suppressed by the rotations and vibrations on the dimer. In the present theory the latter are described via an adiabatic approach.
Publisher: MDPI AG
Date: 17-08-2023
DOI: 10.3390/GELS9080663
Abstract: A novel, one-pot sol–gel preparation scheme leading to reproducible incorporation of 20–40 nm sized gold nanoparticles (AuNPs) in SiO2 gels is developed based on in situ reduction during gelation using chloroauric acid and ascorbic acid. Variation in the preparation conditions affects the chemical composition, optical properties and size distribution of the AuNPs incorporated in the silica gels. Different organic dopants, i.e., oleic acid, acetic acid or dodecanethiol, are applied to modify the final composite material and to control the rate of reduction and growth of the AuNPs in the gels. The synthesized s les are characterized by UV/Vis/NIR spectroscopy, X-ray diffraction, transmission electron microscopy, thermal conductivity measurements and DTA/TG measurements. The optical properties of the obtained composites are explained using Mie theory. The incorporation of AuNPs leads to an increase in the thermal conductivity of the silica gels. The best process method in this contribution is the use of NaOH as a gelation catalyst and oleic acid as an organic modifier, leading to 20 nm AuNPs dispersed in the silica matrix.
Publisher: Springer Science and Business Media LLC
Date: 12-1992
DOI: 10.1007/BF02162701
Publisher: AIP Publishing
Date: 24-02-2005
DOI: 10.1063/1.1854127
Abstract: Phase formation of surface alloying by spinodal decomposition has been studied at an electrified interface. For this aim Zn was electrodeposited on Au(111) from the ionic liquid AlCl3-MBIC (58:42) containing 1 mM Zn(II) at different potentials in the underpotential range corresponding to submonolayer up to monolayer coverage. Structure evolution was observed by in situ electrochemical scanning tunneling microscopy (STM) at different times after starting the deposition via potential jumps and at temperatures of 298 and 323 K. Spinodal or labyrinth two-dimensional structures predominate at middle coverage, both in deposition and in dissolution experiments. They are characterized by a length scale of typically 5 nm which has been determined from the power spectral density of STM images. Structure formation and surface alloying are governed by slow kinetics with a rate constant k with activation energy of 120 meV and preexponential factor of 0.17s−1. The evolution of the structural features is described by a continuum model and is found to be in good agreement with the STM observations. From the experimental and model calculation results we conclude that the two-dimensional phase formation in the Zn on Au(111) system is dominated by surface alloying. The phase separation of a Zn-rich and a Zn-Au alloy phase is governed by two-dimensional spinodal decomposition.
Publisher: Universiti Malaysia Pahang Publishing
Date: 30-12-2013
Publisher: World Scientific Pub Co Pte Lt
Date: 19-11-2020
DOI: 10.1142/S0219477520500170
Abstract: A theoretical parallel between the classical Brownian motion and quantum mechanics is explored via two stochastic sources. It is shown that, in contrast to the classical Langevin force, quantum mechanics is driven by turbulent velocity fluctuations with diffusive behavior. In the case of simultaneous action of the thermal and quantum noises, the quantum Brownian motion is described as well.
Publisher: Elsevier BV
Date: 08-2010
Publisher: American Chemical Society (ACS)
Date: 10-02-2011
DOI: 10.1021/LA1044656
Abstract: The present paper reports a new drainage model accounting for the electro-Marangoni effect in thin liquid films stabilized by ionic surfactants. It was shown that the liquid outflow during the film drainage drifts charges from the diffuse part of the electrical double layer toward the film rim and thus generates a streaming potential along the film plane. This creates reverse fluxes near the film surfaces due to the requirement for zero electric current in the film. In a previous paper on this model (Tsekov et al. Langmuir, 2010, 26, 4703), the immobile surfaces were assumed. Here, the film surfaces were considered mobile, and surface velocity is controlled by an electro-Marangoni number. It was also shown that the motion of the charges makes the film surfaces more mobile, and they flow in reverse direction to the overall liquid outflow. The theory was validated by experimental data on drainage of planar foam films stabilized by cationic (tetrapentyl ammonium bromide) and anionic (sodium dodecyl sulfate) surfactants. A good agreement between the theoretical prediction and experimental data was found.
Publisher: IOP Publishing
Date: 14-08-2007
Publisher: Springer Science and Business Media LLC
Date: 04-2016
Publisher: Elsevier BV
Date: 02-2019
DOI: 10.1016/J.JCRC.2018.10.006
Abstract: Focused cardiac ultrasound (FCU) training in critical care is restricted by availability of instructors. Supervised training may be substituted by self-directed learning with an ultrasound simulator guided by automated electronic learning, enabling scalability. We prospectively compared learning outcomes in novice critical care physicians after completion of a supervised one-and-a-half-day workshop model with a self-guided course utilizing a simulator over four weeks. Both groups had identical pre-workshop on-line learning (20h). Image quality scores were compared using FCU performed on humans without pathology. Interpretive knowledge was compared using 20MCQ tests. Of 161 eligible, 145 participants consented. Total Image quality scores were higher in the Simulator group (95.2% vs. 66.0%, P < .001) and also higher for each view (all P .1). Including purchase of the simulator and ultrasound equipment, the simulator course required lower direct costs (AUD$796 vs. $1724 per participant) and instructor time (0.5 vs.1.5 days) but similar participant time (2.8 vs. 3.0 days). Self-directed learning with ultrasound simulators may be a scalable alternative to conventional supervised teaching with human models.
Publisher: Wiley
Date: 05-2012
Publisher: Elsevier BV
Date: 07-1992
Publisher: No publisher found
Date: 2015
Publisher: Wiley
Date: 16-09-2022
DOI: 10.1002/AJUM.12318
Abstract: Ultrasound‐guided peripheral intravenous cannulation (USGPIVC) benefits patients with difficult intravenous access (DIVA) through visualising otherwise non‐visible and non‐palpable veins. Supervised live‐case training is an important component of learning this skill, but supervisor availability can present a barrier limiting or delaying staff completing their training. The aim of this study was to determine the first‐attempt success rate of newly trained USGPIVC inserters using remote supervision and timely written feedback based on app‐based screen recordings taken during insertion. Secondary aims were overall procedural success, and inserter and patient experiences. This study is an observational cohort study carried out between October and December 2021. Fourteen newly trained junior medical officers (JMOs) were eligible to utilise USGPIVC on a minimum of five consenting patients while simultaneously recording the ultrasound screen during insertion to capture their technique. Feedback was generated following expert review of these recordings against a standardised feedback tool. Average first‐attempt success was 71% (n = 72) in the 102 patients recruited. The average time for JMOs to receive feedback was 30 h, and 13 JMOs (93%) felt well supported and completed the remote training pathway. The majority of patients were female (n = 59 58%), were aged 41–80 years (n = 75 74%) and had ≥2 risk factors for DIVA (n = 57 56%). First‐attempt success rates were similar when comparing remote supervision used in this study to direct supervision used by other studies.This finding supports incorporating remote supervision into training guidelines for USGPIVC as an alternative method of supervision, particularly when supervisor availability is limited.
Publisher: Elsevier BV
Date: 04-1999
Publisher: Elsevier BV
Date: 02-2008
DOI: 10.1016/J.JCIS.2007.10.053
Abstract: This paper presents new theoretical and experimental results that quantify the role of surfactant adsorption and the related interfacial tension changes and interfacial forces in the emulsion film drainage and equilibrium. The experimental results were obtained with plane-parallel microscopic films from aqueous sodium dodecyl sulphate solutions formed between two toluene droplets using an improved micro-interferometric technique. The comparison between the theory and the experimental data show that the emulsion film drainage and equilibrium are controlled by the DLVO interfacial forces. The effect of interfacial viscosity and interfacial tension gradient (the Marangoni number) on the film drainage is also significant.
Publisher: AIP Publishing
Date: 28-12-2008
DOI: 10.1063/1.3046679
Abstract: We study theoretically the osmotic equilibria for a shell immersed in a suspension of polyions (e.g., colloids, polyelectrolytes, etc.). The shell is treated as impermeable for polyions, but allowing free diffusion of counterions that permeate inside the shell. From the solution of linearized Poisson–Boltzmann equation, we obtain the distribution of a potential and concentration profiles for polyions and counterions. We then obtain an explicit formula for the excess osmotic pressure of a polyion solution exerted on the shell, which includes a quadratic term in order to provide a self-consistency of a linear theory. As a result this pressure is larger than given by a concentration of polyions at the outer shell boundary obtained within linearized theory. It is, however, always smaller than or equal to the bulk osmotic pressure. This difference is attributed to a repulsive electrostatic disjoining pressure due to an overlap of counterion clouds inside the shell. A comparison with molecular dynamics simulations is provided and demonstrates that although the concentration profiles obtained within a linear theory deviate from simulation data at large potential, the theoretical and simulation pressures are in surprisingly good harmony.
Publisher: IOP Publishing
Date: 28-10-2005
Publisher: Elsevier BV
Date: 10-1990
Publisher: Springer Science and Business Media LLC
Date: 07-11-2019
Publisher: IOP Publishing
Date: 28-10-2005
Publisher: Elsevier BV
Date: 11-1998
Publisher: Elsevier BV
Date: 04-1999
Publisher: World Scientific Pub Co Pte Ltd
Date: 21-08-2017
DOI: 10.1142/S0219477517500286
Abstract: We regard the non-relativistic Schrödinger equation as an ensemble mean representation of the stochastic motion of a single particle in a vacuum, subject to an undefined stochastic quantum force. The local mean of the quantum force is found to be proportional to the third spatial derivative of the probability density function, while its associated pressure is proportional to the second spatial derivative. The latter arises from the single particle diluted gas pressure, and this observation allows to interpret the quantum Bohm potential as the energy required to put a particle in a bath of fluctuating vacuum at constant entropy and volume. The stochastic force expectation value is zero and is uncorrelated with the particle location, thus does not perform work on average. Nonetheless, it is anti-correlated with volume and this anti-correlation leads to an uncertainty relation. We analyze the dynamic Gaussian solution to the Schrödinger equation as a simple ex le for exploring the mean properties of this quantum force. We conclude with a few possible interpretations as to the origins of quantum stochasticity.
Publisher: American Chemical Society (ACS)
Date: 10-12-2010
DOI: 10.1021/LA903593P
Publisher: MDPI AG
Date: 24-09-2018
DOI: 10.20944/PREPRINTS201809.0456.V1
Abstract: The Vogel-Fulcher-Tammann equation is exposed as a particular ex le of the mean field theory. It is generalized by taking into account an arbitrary critical exponent of susceptibility, discriminating between different classes of universality. The Bell-Evans-Polanyi principle is employed to estimate the difference between the activation energies of flows in crystals and glasses, which appears to coincide with the excess Gibbs energy of the glass compared to the crystal.
Publisher: Prof. Marin Drinov Publishing House of Bulgarian Academy of Sciences
Date: 21-12-2019
Publisher: IOP Publishing
Date: 18-05-1992
Publisher: Elsevier BV
Date: 03-1992
Publisher: World Scientific Pub Co Pte Lt
Date: 27-02-2021
DOI: 10.1142/S0219477521300044
Abstract: A nonlinear master equation is derived, reflecting properly the entropy of open quantum systems. In contrast to linear alternatives, its equilibrium solution is exactly the canonical Gibbs density matrix. The corresponding nonlinear equation for the Wigner function accounts rigorously for the thermo-quantum entropy. It reduces at large friction to the quantum Smoluchowski equation in the coordinate subspace. The previously derived Maxwell–Heisenberg relation for the nonequilibrium momentum dispersion of quantum Brownian particles is confirmed as well as the related quantum generalization of the classical Einstein law of Brownian motion.
Publisher: Wiley
Date: 11-2020
DOI: 10.1002/AJUM.12208
Publisher: Prof. Marin Drinov Publishing House of BAS (Bulgarian Academy of Sciences)
Date: 02-05-2022
Abstract: It is proven that the Clapeyron–Mendeleev equation, originally discovered for gases with large entropy, describes the state of dark matter/energy due to the enormous self-gravitation. It is shown that the dark matter exists as compact cold neutrino stars at positive temperature with size twice the Schwarzschild radius. In contrast, the dark energy is dark matter at temperature below the absolute zero, which is locked entirely in black holes, where the pressure is negative as required for the Universe intrinsic expansion. The derived dark phase diagram predicts negative critical temperatures for the Big Bang and the Big Rip of black holes.
Publisher: Elsevier BV
Date: 08-2001
Publisher: Springer Berlin Heidelberg
Date: 2004
DOI: 10.1007/B94005
Publisher: AIP Publishing
Date: 11-1994
DOI: 10.1063/1.468209
Abstract: The dynamics of a mechanical subsystem interacting with an amorphous solid is studied. The Hamilton equations are transformed to a set of stochastic Langevin equations governing the random evolution of the coordinates of the subsystem particles. An explicit expression for the friction tensor is obtained which accounts both for the subsystem–solid interactions and for the thermal vibrations of the atoms of the amorphous solid. The possibility to calculate the diffusion coefficient of a Brownian particle in an amorphous solid is examined. Finally, a new approach for the description of the Brownian dynamics in liquids based on the results obtained for amorphous solids is proposed.
Publisher: AIP Publishing
Date: 27-06-2007
DOI: 10.1063/1.2743432
Abstract: The authors report dynamic and coagulation properties of a dispersion of polyelectrolyte multilayer microcapsules filled with solutions of a strong polyelectrolyte. Microcapsules are shown to take a charge of the sign of encapsulated polyions and are characterized by a nonuniform distribution of inner polyions, which indicates a semipermeability of the shell and a leakage of counterions. The capsule self-diffusion coefficient in the vicinity of the similarly charged wall is measured using a particle tracking procedure from confocal images of the dispersion. The diffusion of capsules in the force field suggests that the effective interaction potential contains an electrostatic barrier, so that we deal with the same types of interaction forces as for solid particles. The theoretical estimates of the authors show that when microcapsules are in close proximity, their interaction should even be quantitatively the same as that of colloids with the same surface potential. However, due to the mobility of inner polyions they might repel stronger at large distances. The authors thus conclude that the encapsulation of charged polymers is an important factor in determining the adhesion and interaction properties of multilayer microcapsules.
Publisher: IOP Publishing
Date: 29-08-2003
Publisher: Universa BV
Date: 09-2022
DOI: 10.56126/73.3.16
Abstract: Background: Sterile ultrasound covers and conducting mediums are recommended when performing ultrasound guided percutaneous procedures to minimise risk of infection to the patient. Purpose manufactured ultrasound transducer cover kits meet these requirements. Transparent dressings meet some of these requirements however, they are not approved for use as ultrasound transducer covers. We recognised that our departmental practice may not adhere to these standards. Objective: The primary objective was to identify and improve the rate of adherence to the recommended aseptic precautions by anaesthetists performing ultrasound guided percutaneous procedures at the Department of Anaesthesia, Royal Brisbane and Women’s Hospital, the largest tertiary referral hospital in Queensland, Australia. Secondary objectives were to identify types and rates of use of various probe covers and ultrasound conductive mediums used. Design: A complete quality improvement cycle was undertaken using a plan, do, study, act model. Methods: Firstly, a departmental wide voluntary survey was distributed in March 2019 focused on practitioner’s baseline aseptic practices for ultrasound guided peripheral intravenous cannulation (USGPIVC). Subsequently a suite of interventions were undertaken between May 2019 to April 2020 focusing on highlighting recommended aseptic practices through the use of high-quality sterile transducer covers and sterile conducting mediums for all ultrasound guided percutaneous procedures. Components of the intervention included the development of a departmental policy, educational activities, and improving equipment availability and access. A post- intervention follow up audit was repeated in April 2020 to measure changes in practice. Results: Of 134 anaesthetic consultants or trainees 58 completed the pre-intervention survey and 47 completed the post- intervention survey. After the intervention the use of recommended transducer covers and conducting mediums increased from 10.3% to 76.6% and 58.6% to 83.0% respectively. Participants were more likely to choose both a recommended transducer cover and conducting medium than at least one non-recommended option ([OR] 20.4, 95% CI: 7.1 - 58.4). There was a 122% increase in the number of recommended transducer cover kits ordered when comparing stock inventory over a six-month period before and after the intervention. Conclusion: Adherence to the recommended aseptic precautions for USGPIVC improved after the implementation of educational interventions.
Publisher: AIP Publishing
Date: 03-2007
DOI: 10.1063/1.2437201
Abstract: The authors study theoretically the electrostatic equilibria for a shell filled with a suspension of polyions (e.g., colloids, polyelectrolytes, etc.) and immersed in an infinite salt-free reservoir. The shell is treated as impermeable for polyions, but allowing free diffusion of counterions. From the solution of the linearized Poisson-Boltzmann equation we obtain the distribution of the potential and concentration profiles for polyions. The authors then derive explicit formulas for the excess electro-osmotic pressure of a polyion solution exerted by the shell. This is shown to be due to a concentration of polyions at the inner shell boundary and can be very different from the pressure of a corresponding bulk polyion solution.
Publisher: Prof. Marin Drinov Publishing House of BAS (Bulgarian Academy of Sciences)
Date: 10-2023
Publisher: Springer US
Date: 1997
Publisher: Elsevier BV
Date: 2001
Publisher: World Scientific Pub Co Pte Lt
Date: 09-2017
DOI: 10.1142/S2424942417500086
Abstract: The quantum Liouville equation, which describes the phase space dynamics of a quantum system of fermions, is analyzed from stochastic point of view as a particular ex le of the Kramers–Moyal expansion. Quantum mechanics is extended to relativistic domain by generalizing the Wigner–Moyal equation. Thus, an expression is derived for the relativistic mass in the Wigner quantum phase space presentation. The diffusion with an imaginary diffusion coefficient is discussed. An imaginary stochastic process is proposed as the origin of quantum mechanics.
Publisher: Springer Netherlands
Date: 1999
Publisher: MDPI AG
Date: 23-05-2001
DOI: 10.3390/I2020066
Publisher: American Chemical Society (ACS)
Date: 24-07-2001
DOI: 10.1021/LA010584Y
Publisher: Unpublished
Date: 1993
Publisher: Unpublished
Date: 2012
Publisher: Prof. Marin Drinov Publishing House of Bulgarian Academy of Sciences
Date: 02-2019
Publisher: Elsevier BV
Date: 10-2018
Publisher: Unpublished
Date: 2011
Publisher: Royal Society of Chemistry (RSC)
Date: 2005
DOI: 10.1039/B510757A
Abstract: Oscillatory wetting instabilities driven by capillary-gravitation forces have been explored very recently in the binary fluid Ga-Pb alloy [A. Turchanin, R. Tsekov and W. Freyland, J. Chem. Phys., 2004, 120, 11 171]. This system is characterized by a complete wetting transition at liquid-liquid coexistence. Due to its metallic nature the bulk and interfacial instabilities are strongly coupled via variation of the respective emissivities. In our previous work we have investigated these phenomena at different cooling cycles and at constant temperature inside the miscibility gap. In this study we present for the first time the observations of the oscillatory wetting instabilities also in heating cycles. The interfacial properties of a Ga0.95Pb0.05 alloy at conditions inside the miscibility gap have been investigated by following the second harmonic generation (SHG) intensity changes. Corresponding model calculations of the Pb-rich wetting film instabilities have been performed taking into account the effect of a temperature variation vertical to the bulk s le. The influence of this temperature variation on the occurrence of the oscillations is discussed.
Publisher: Springer Science and Business Media LLC
Date: 10-09-2008
Publisher: Springer Science and Business Media LLC
Date: 09-07-2008
Publisher: IOP Publishing
Date: 03-2016
Publisher: MDPI AG
Date: 11-07-2023
DOI: 10.20944/PREPRINTS202307.0671.V1
Abstract: Trailing the modern ideas of sociophysics, a minimalistic thermodynamic model of society is proposed, which consists of three social ingredients: people, economy, and entropy. Employing the universal van der Waals equation of state, many important relationships are discovered, including laws of econophysics. The main conclusion is that the irreversible social evolution obeys the Second Law of thermodynamics, which governs the striving for social liberty and economic freedom.
Publisher: AIP Publishing
Date: 06-2007
DOI: 10.1063/1.2741151
Abstract: It has long been accepted that hydrodynamic pressure in a draining fluid film can cause inversion of curvature of a fluid-fluid interface, creating the so-called dimple. However, it was recently discovered that a different shape, dubbed a wimple, can be formed if a bubble/drop is initially in the field of repulsive surface forces, so that a wetting film is formed. The film profile then includes a central region in which the film remains thin, surrounded by a ring of greater film thickness and bounded at the outer edge by a barrier rim. This shape later evolves to a conventional dimple, which then drains in the usual way. Here we carry out numerical simulations of the draining film evolution that allow us to uncover the physical mechanism responsible for wimple formation. Simple analytical estimates are then obtained for characteristic times of different stages of drainage, and are shown to be in good agreement with experimental data. We demonstrate that wimpling is a general phenomenon that can be encountered in many different systems.
Publisher: Elsevier BV
Date: 12-1995
Publisher: Prof. Marin Drinov Publishing House of Bulgarian Academy of Sciences
Date: 26-04-2019
Publisher: MDPI AG
Date: 25-09-2018
DOI: 10.20944/PREPRINTS201809.0485.V1
Abstract: It is shown that quantum entanglement is the only force able to maintain the fourth state of matter, possessing fixed shape at an arbitrary volume. Accordingly, a new relativistic Schr& ouml dinger equation is derived and transformed further to the relativistic Bohmian mechanics via the Madelung transformation. Three dissipative models are proposed as extensions of the quantum relativistic Hamilton-Jacobi equation. The corresponding dispersion relations are obtained.
Publisher: Unpublished
Date: 2012
Publisher: AIP Publishing
Date: 23-02-2010
DOI: 10.1063/1.3328126
Abstract: Electron gases in metals are described as quantum charged Newtonian viscous fluids experiencing Ohmic Darcy friction on the solid lattice ions as well. The dispersion relation of the electron acoustic waves is derived, which shows the existence of new quantum diffusion processes. The electric double layer near a metal surface is studied, which exhibits a new quantum oscillatory-decaying behavior different from the Friedel oscillations.
Publisher: World Scientific Pub Co Pte Lt
Date: 29-09-2016
DOI: 10.1142/S021947751650022X
Abstract: A Brownian harmonic oscillator, which dissipates energy either by friction or via emission of electromagnetic radiation, is considered. This Brownian emitter is driven by the surrounding thermo-quantum fluctuations, which are theoretically described by the fluctuation–dissipation theorem. It is shown how the Abraham–Lorentz force leads to dependence of the half-width on the peak frequency of the oscillator litude spectral density. It is found that for the case of a charged particle moving in vacuum at zero temperature, its root-mean-square velocity fluctuation is a universal constant, equal to roughly 1/18 of the speed of light. The relevant Fokker–Planck and Smoluchowski equations are also derived.
Publisher: Elsevier BV
Date: 2011
DOI: 10.1016/J.JCIS.2010.09.032
Abstract: Drainage of foam films with different radii (50-150 μm), stabilized by hexathylene glycol dodecyl ether C(12)E(6) and in a presence of 0.024 M NaCl, were analyzed in the light of a recent dynamic fractal classification of [1]. The latter accounts for the effect of film surface corrugations developed during the film drainage. For simplicity, the film surface mobility is neglected since the presence of surfactants reduces dramatically the film surface velocity. The magnitude of surface non-homogeneities, caused by the film drainage, is accounted via a dynamic fractal dimension parameter α being spanned between zero and two. Depending on the α-value the film drains by different kinetic laws. For ex le, if the thin film is planar α=2 and it drains according to the Reynolds law if α=1 the film contains an axisymmetric dimple causing faster drainage if α=1/2 the film exhibits number of asymmetric dimples and the film drains even faster finally if α=0 the film contains spatially uncorrelated domains causing the fastest possible drainage. The present analysis of experimental data suggests that the parameter α is inversely proportional to the film radius R and it is independent of the type and concentration of surfactants. A semi-empirical model for α is proposed, thus completing the generic dynamic fractal classification.
Publisher: Informa UK Limited
Date: 09-1997
Publisher: Elsevier BV
Date: 12-1997
Publisher: AIP Publishing
Date: 17-01-2012
DOI: 10.1063/1.3676246
Abstract: We consider an osmotic equilibrium between bulk solutions of polyelectrolyte bounded by semi-permeable membranes and separated by a thin film of salt-free liquid. Although the membranes are neutral, the counter-ions of the polyelectrolyte molecules permeate into the gap and lead to a steric charge separation. This gives rise to a distance-dependent membrane potential, which translates into a repulsive electrostatic disjoining pressure. From the solution of the nonlinear Poisson–Boltzmann equation, we obtain the distribution of the potential and of ions. We then derive an explicit formula for the pressure exerted on the membranes and show that it deviates from the classical van't Hoff expression for the osmotic pressure. This difference is interpreted in terms of a repulsive electrostatic disjoining pressure originating from the overlap of counterion clouds inside the gap. We also develop a simplified theory based on a linearized Poisson–Boltzmann approach. A comparison with simulation of a primitive model for the electrolyte is provided and does confirm the validity of the theoretical predictions. Beyond the fundamental result that the neutral surfaces can repel, this mechanism not only helps to control the adhesion and long-range interactions of living cells, bacteria, and vesicles, but also allows us to argue that electrostatic interactions should play enormous role in determining behavior and functions of systems bounded by semi-permeable membranes.
Publisher: IOP Publishing
Date: 07-11-1995
Publisher: IOP Publishing
Date: 12-2012
Publisher: Royal Society of Chemistry (RSC)
Date: 1992
DOI: 10.1039/FT9928800251
Publisher: Unpublished
Date: 2014
Publisher: Pleiades Publishing Ltd
Date: 22-03-2012
Publisher: IOP Publishing
Date: 07-2013
Publisher: Wiley
Date: 18-07-2007
Publisher: Wiley
Date: 12-06-2023
DOI: 10.1002/JUM.16286
Abstract: There is a lack of international consensus as to whether high‐ or low‐level disinfection (HLD or LLD) is required for ultrasound (US) transducers used during percutaneous procedures. This study compared the effectiveness of LLD to HLD on US transducers contaminated with microorganisms from skin. Two identical linear US transducers repeatedly underwent either LLD or HLD during the study. Randomization determined which of these transducers was applied to left and right forearms of each participant. Swabs taken from transducers before and after reprocessing were plated then incubated for 4–5 days, after which colony forming units (CFU) were counted and identified. The primary hypothesis was the difference in the proportion of US transducers having no CFUs remaining after LLD and HLD would be less than or equal to the noninferiority margin of −5%. Of the 654 recruited participants 73% (n = 478) had microbial growth from both transducers applied to their left and right forearms before reprocessing. These were included in the paired noninferiority statistical analysis where, after disinfection, all CFUs were eliminated in 100% (95% CI: 99.4–100.0%) of HLD transducer s les (n = 478) and 99.0% (95% CI: 97.6–99.7%) of LLD transducer s les (n = 473). The paired difference in the proportion of transducers having all CFUs eliminated between LLD and HLD was −1.0% (95% CI: −2.4 to −0.2%, P ‐value .001). Disinfection with LLD is noninferior to HLD when microorganisms from skin have contaminated the transducer. Therefore, using LLD for US transducers involved in percutaneous procedures would present no higher infection risk compared with HLD.
Publisher: Elsevier BV
Date: 08-2014
DOI: 10.1016/J.CIS.2013.10.019
Abstract: This work shows a successful ex le of coupling of theory and experiment to study the tribology of bubble rubbing on solid surface. Such kind of investigation is reported for the first time in the literature. A theory about wetting film intercalated between bubble and moving solid surface was developed, thus deriving the non-linear evolution differential equation which accounted for the friction slip coefficient at the solid surface. The stationary 3D film thickness profile, which appears to be a solution of the differential equation, for each particular speed of motion of the solid surface was derived by means of special procedure and unique interferometric experimental setup. This allowed us to determine the 3D map of the lift pressure within the wetting film, the friction force per unit area and the friction coefficient of rubbing at different speeds of motion of the solid surface. Thus, we observed interesting tribological details about the rubbing of the bubble on the solid surface like for ex le: 1. A regime of mixed friction between dry and lubricated friction exists in the range of 6-170 μm/s, beyond which the rubbing between the bubble and solid becomes completely lubricated and passes through the maximum 2. The friction coefficient of rubbing has high values at very small speeds of solid's motion and reduces substantially with the increase of the speed of the solid motion until reaching small values, which change insignificantly with the further increase of the speed of the solid. Despite the numerous studies on the motion of bubble/droplet in close proximity to solid wall in the literature, the present investigation appears to be a step ahead in this area as far as we were able to derive 3D maps of the bubble close to the solid surface, which makes the investigation more profound.
Publisher: IOP Publishing
Date: 08-2013
Publisher: IOP Publishing
Date: 16-02-2011
Publisher: Unpublished
Date: 2014
Publisher: Elsevier BV
Date: 03-2010
Publisher: Cambridge Media
Date: 10-04-2021
DOI: 10.33235/VA.7.1.6-11
Publisher: AIP Publishing
Date: 21-05-2007
DOI: 10.1063/1.2741507
Abstract: A simple theoretical model is developed describing ionic liquids as regular solutions. The separation of these ionic mixtures is studied on the base of the Cahn-Hilliard theory coupled with electrostatics. It is shown that the ionic liquids decompose to thin layers of oppositely charged liquids at low temperatures. At larger temperatures the separation occurs only near the ionic liquid/vacuum surface, thus explaining the oscillatory-decaying structure of the electric double layer observed via computer simulations. In contrast to noncharged liquids the ionic ones exhibit two critical temperatures, where the temperature coefficients of all characteristic lengths possess singularities. These second order ferroelectric phase transitions are possible explanations of the experimentally measured via light scattering peculiar temperature dependence of the interfacial dipole moment density on several ionic liquid/vacuum interfaces.
Publisher: AIP Publishing
Date: 24-05-2004
DOI: 10.1063/1.1737306
Abstract: We present the first experimental investigation and pertinent theoretical modeling of an interfacial oscillatory instability in a binary fluid alloy, the Ga–Pb system. It is characterized by spinodal decomposition at elevated temperatures and by a complete wetting transition at liquid–liquid coexistence. For the alloy Ga0.95Pb0.05 the fluid interface has been probed by second harmonic generation (SHG) under UHV conditions at temperatures between 740 and 550 K. At conditions inside the miscibility gap clear oscillations of the SHG-intensity with a period of ∼30 min are found for different cooling cycles and also at constant temperatures. These interfacial oscillatory instabilities simultaneously induce temperature oscillations in the bulk fluid with the same period. This phenomenon can be explained by a periodic variation of the fluid interfacial emissivity. A model has been developed which describes the wetting–dewetting dynamics by hydrodynamic equations within the Reynolds approximation. It is found that the interfacial oscillatory instability is determined by capillary-gravitation instability. The model quantitatively describes the time evolution of the interfacial and temperature oscillations and gives the correct value of the oscillation period. A detailed comparison of the experimental and model results is given.
Publisher: Elsevier BV
Date: 10-2010
Publisher: World Scientific Pub Co Pte Lt
Date: 10-10-2021
DOI: 10.1142/S0219477521500097
Abstract: It is demonstrated how the Schrödinger equation emerges from stochastic momentum kicks of the force carriers, transmitting the fundamental interactions between the point particles. The picture is consistent with quantum field theory and points out that the force carriers are the only quantum particles. Since the latter are waves in the coordinate space, they are responsible for the wavy character of quantum mechanics.
Publisher: Elsevier BV
Date: 09-2020
Publisher: Unpublished
Date: 2015
Publisher: AIP Publishing
Date: 15-05-1994
DOI: 10.1063/1.466863
Abstract: Experiments from literature have shown that the diffusion coefficients of dimers of rhenium atoms on tungsten are larger than those of the single rhenium atoms for the cross-channel configuration of the dimer and smaller for the in-channel configuration. In the present paper, expressions are derived for the diffusion coefficient which explain the above observations. They are based on Langevin equations of the motion of a single atom and dimer on a metal surface, in which the relation derived previously by the authors for the friction coefficient is employed. It is also demonstrated that the diffusion coefficient of the dimers exhibits a periodical dependence upon the ratio between the dimer length and the metal lattice parameter, phenomenon which is called resonant diffusion.
Publisher: Wiley
Date: 23-07-2012
Publisher: Elsevier BV
Date: 11-2011
DOI: 10.1016/J.JCIS.2011.08.002
Abstract: The behavior of thin wetting films on chemically patterned surfaces was investigated. The patterning was performed by means of imprinting of micro-grid on methylated glass surface with UV-light (λ=184.8 nm). Thus imprinted image of the grid contained hydrophilic cells and hydrophobic bars on the glass surface. For this aim three different patterns of grids were utilized with small, medium and large size of cells. The experiment showed that the drainage of the wetting aqueous films was not affected by the type of surface patterning. However, after film rupturing in the cases of small and medium cells of the patterned grid the liquid from the wetting film underwent fast self-organization in form of regularly ordered droplets covering completely the cells of the grid. The droplets reduced significantly their size upon time due to evaporation. In the cases of the largest cell grid, a wet spot on the place of the imprinted grid was formed after film rupturing. This wet spot disassembled slowly in time. In addition, formation of a periodical zigzag three-phase contact line (TPCL) was observed. This is a first study from the planned series of studies on this topic.
Publisher: MDPI AG
Date: 25-06-2020
Abstract: The slip effect in wetting films is theoretically studied, and a nonlinear dependence of the hydrodynamic velocity on the slip length is discovered. It is demonstrated that the hydrodynamic flow is essentially affected by the presence of a nonuniform slip length distribution, leading also to enhancement of the energy dissipation in the films. This effect could dramatically slow the usually quick hydrodynamic flows over superhydrophobic surfaces, for instance.
Publisher: Elsevier BV
Date: 12-2013
DOI: 10.1016/J.JCIS.2013.08.049
Abstract: This is the first interferometric study in the literature on wetting film entrapped between bubble and moving solid substrate. Unique experimental setup was specially designed for monitoring the thickness profiles of wetting film, intercalated between the bubble and moving solid surface. For this reason, special procedure developed for this study was applied for determination of 3D film thickness profiles. This allowed us to determine 3D profiles of the disjoining, the lift pressures as well as the viscous stress tensor as a function of the velocity of the solid surface. Thus, one can see that a strong linear dependence between the average film thickness and the speed of motion of the solid surface exists until a certain critical speed of motion, beyond which the dependence becomes weaker but keeps its linear trend. Similar is the propensity with the average lift pressure. Moreover, one can observe how the inhomogeinity of the film surfaces changes upon increasing the speed of motion of the solid surface. The proposed technique reveals new possibilities for investigation of bubbles and solid surfaces on deeper level when they are in relative motion towards each other. Thus, one can conduct detailed tribological studies on bubbles moving in close proximity to solid surfaces.
Publisher: IOP Publishing
Date: 24-05-1993
Publisher: Elsevier BV
Date: 1992
Publisher: American Chemical Society (ACS)
Date: 11-09-2008
DOI: 10.1021/LA801456J
Publisher: AIP Publishing
Date: 15-01-1994
DOI: 10.1063/1.466623
Abstract: In this paper the dynamics of a mechanical subsystem interacting with a solid body is studied. The Newton equations are transformed to a set of stochastic generalized Langevin equations describing the evolution of the coordinates of the subsystem particles. The solid is modeled as a bath of interacting harmonic oscillators, and the effect of their spatial correlations on the statistical properties of the Langevin forces is accounted for. The most important result is the relation established between the static interaction of the subsystem with the solid body and the dissipative and fluctuation forces. In the particular case of a subsystem consisting of a single particle, an expression is derived for the friction tensor in terms of the static interaction potential and Debye cutoff frequency of the solid. The analysis is applied in the latter case to some simple processes occurring in solids, such as adsorption, desorption, and diffusion.
Publisher: American Chemical Society (ACS)
Date: 26-08-2016
DOI: 10.1021/ACS.LANGMUIR.6B02349
Abstract: A method is proposed for the experimental determination of the adsorption of inorganic electrolytes at a surface covered with insoluble surfactant monolayer. This task is complicated by the fact that the change of the salt concentration alters both chemical potentials of the electrolyte and the surfactant. Our method resolves the question by combining data for the surface pressure versus area of the monolayer at several salt concentrations with data for the equilibrium spreading pressure of crystals of the surfactant (used to fix a standard state). We applied the method to alcohols spread at the surface of concentrated halide solutions. The measured salt adsorption is positive and has nonmonotonic dependence on the area per surfactant molecule. For the liquid expanded film, depending on the concentration, there is one couple of ions adsorbed per each 3-30 surfactant molecules. We analyzed which ion, the positive or the negative, stands closer to the surface, by measuring the effect of NaCl on the Volta potential of the monolayer. The potentiometric data suggest that Na(+) is specifically adsorbed, while Cl(-) remains in the diffuse layer, i.e., the surface is positively charged. The observed reverse Hofmeister series of the adsorptions of NaF, NaCl, and NaBr suggests the same conclusion holds for all these salts. The force that causes the adsorption of Na(+) seems to be the interaction of the ion with the dipole moment of the monolayer.
Publisher: Elsevier BV
Date: 06-2000
Publisher: Elsevier BV
Date: 09-1991
Publisher: Wiley
Date: 17-11-2021
DOI: 10.1002/PI.6323
Abstract: Two types (with and without a hydrolysis stabilizer) of polyamide 6.6 (PA6.6) reinforced with 30% w/w glass fibres were examined against the influence of automotive cooling fluids, e.g. ethylene glycol aqueous solutions. The overall goal was to find a methodology to compare the performance of PA6.6 materials against the impacts of the hydrolysis environment. The stabilizer effect on the hydrolytic resistance of the materials was assessed using tensile tests according to ISO 527, and their strain‐at‐break values were evaluated in more detail. The degradation mechanism of both PA types was monitored by infrared spectroscopy and SEM. The material lifetime was described by the Arrhenius equation. The results show that the hydrolysis stabilizer operates effectively at low temperature but exhibits weak performance above 130 °C, which is explained by faster consumption of the stabilizing agent. © 2021 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry.
Publisher: Elsevier BV
Date: 04-1999
Publisher: Elsevier BV
Date: 04-2013
Publisher: IOP Publishing
Date: 22-11-1993
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Start Date: 1995
End Date: 1997
Funder: Bulgarian National Science Fund
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Funder: Deutsche Forschungsgemeinschaft
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Funder: Deutsche Forschungsgemeinschaft
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Funder: Deutsche Forschungsgemeinschaft
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Funder: Bulgarian National Science Fund
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Funder: Deutsche Forschungsgemeinschaft
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