Magnetic fluids based on single-domain magnetic spinel ferrite nanoparticles dispersed in various liquid media are of particular practical and scientific interest. This paper presents a muon spectroscopy study of a ferrofluid based on magnetic nanoparticles of CoFe2O4 molecules dispersed in water (H2O) with a nanoparticle concentration of 3%. In this study, it was determined that the structure and magnitude of the magnetization of a ferrofluid depend on the viscosity of the liquid itself. It was shown that, at room temperature (290 K) and under an external magnetic field of 527 G, the observed additional magnetization was ~20 G. In a small fraction of the sample under study (~20%), negative magnetization (diamagnetism) was observed. At low temperatures (~30 K), the sample acted as a paramagnet in a magnetic field. For the first time, the magnetic field inside and in the immediate vicinity of a CoFe2O4 nanoparticle has been measured experimentally using the μSR method: the value was 1.96 ± 0.44 kG; thus, direct measurement of the magnetization of a nanoscale object was performed.

Small-angle neutron scattering (SANS) experimental curves for CoFe2O4/LA/SDS-Na/H2O ferrofluid sample with different dilution have been analyzed and modelled using SASView program. The radius of gyration, the mean particle dimension, and Porod exponent are computed for different values of particle volume concentration in the range 1-0.04% at two different temperatures. Dilution effects on the dimentionality of CoFe2O4/LA/SDS-Na/H2O ferrofluid ample are detected.

In this paper we present a study of the crosstalk of the individual measuring volumes in a 2D ion chamber array (QUADRO-fm detector) under proton irradiation. This is the follow-up of the similar study performed for this detector in the case of electron beams. The goal of the paper is to assess the applicability of the proposed array for measurements in charged particle beams generated by ultra-high-power laser - target interactions. Using FLUKA calculations and similar geometry conditions as for the electrons, we obtained relative dose deviation values in a 250 MeV monoenergetic proton beam. The results show low values for this quantity, in the case of the selected parameters. We can conclude that the QUADRO-fm detector can be successfully used in any type of charged particle beams generated at ELI-NP and that the calibration of the array can be performed relative to the central dose.

The high levels of ionizing radiation expected at most of the experimental areas of the Extreme Light Infrastructure - Nuclear Physics (ELI-NP) facility in Bucharest are challenging from a radiation protection point of view. FLUKA Monte Carlo code is a widely used tool allowing to estimate dose contributions of the complex radiation fields and the transport of the radiation through the bulk shielding. In this paper we present the results of a shielding study for the experimental area E1, the site of the laser driven nuclear physics experiments. Updated source terms were used and ambient dose equivalent rates were calculated to check the compliance with the design target dose values and to identify critical dose locations. To reduce radiation levels for neighbouring areas below the required limits, an optimized beam dump and local shielding were proposed.

The stability in time is a critical feature of magnetic nanoparticles in aqueous suspensions, straightly related to the usability in various biomedical fields. This study was focused on the granularity features of cobalt ferrite nanoparticles, dispersed in water by using as stabilizer shell either citrate ions or oleate ones, since fine granulation confers time stability. Microstructural properties investigation was carried out by X-ray diffractometry, Transmission Electron Microscopy, Atomic Force Microscopy and Small Angle Neutron Scattering. The changings of internal organization of colloidal nanosystems during one-year ageing, with differences between the two stabilizer molecular shells, were revealed by microscopy imaging. Two mathematical fittings of Small Angle Neutron Scattering data provided results in accord with microscopy ones for the aged samples. The differences in the bioimpact of the two aged diluted magnetizable fluids on Zea mays plantlets during early ontogenetic stages were analyzed by photosynthesis pigment assay, considering final release of used nanoparticles in the environmental waters, air and soil.

In this paper we present a preliminary study of the reciprocal influences (crosstalk) of the individual measuring volumes in a 2D ion chamber array. The array was designed to be used in the charged particle beams generated by ultra-high-power laser - target interactions. FLUKA Monte Carlo code simulations were performed to obtain dose values in a single detector placed in the geometrical center and in the individual measuring volumes of the array. A quantitative measure of crosstalk was obtained by calculating relative dose deviation values for several divergence angles of a 6 MeV spatially extended electron source and for a range of external distance values between individual measuring volumes. The results show that the relative dose deviation values are very low. No functional dependency on the considerend parameters was found. This indicates that the array can be successfully used in measurements of the radiadion generated by the ultra-high power laser pulses and that it can be calibrated relative to the central dose.

We report about quantitative measurements of the local dielectric constant of insulating materials. A conductive atomic force microscope (AFM) tip is biased relative to the sample and the resulting tip-sample electric force is measured as a function of the distance to the surface. Using a suitable analytical model, the geometric characteristics of the tip are determined from force measurements on conductive materials and are then used to calculate the local dielectric constant from the same type of measurements on insulating materials.

Scanning polarization force microscopy, a relatively new non-contact scanning probe microscopy technique, was applied in order to investigate the properties of liquid surfaces (droplets), such as: topography, microscopic contact angle , surface potential energy P(e), spreading coefficient S, and disjoining pressure ?. Investigations were carried out on glycerol droplets deposited on surfaces of bare silicon, silicon covered with native oxide, and bulk silicon oxide. Contact angle values were determined from directly measured topography profiles of micro- and nanodroplets. Values of surface potential energy, spreading coefficient, and disjoining pressure were calculated based on a model of the dependence of contact angle on droplet height. The results of these experiments offer valuable insights into the mechanisms of wetting phenomena at the microscopic scale.

For liquid droplets of sub-micrometer dimensions, the study of wetting properties (quantified by contact angle, disjoining pressure, spreading coefficient, etc.) is possible using the relatively new technique known as scanning polarization force microscopy (SPFM). This non-contact scanning probe microscopy technique was successfully implemented in our laboratory in order to study the wetting properties of glycerol and sulfuric acid on the surface of highly oriented pyrolytic graphite (HOPG) and glycerol on aluminum film deposited on mica. An AC polarization bias of 3 V at 3 kHz frequency was applied between a conductive atomic force microscope tip and the substrate. The resulting polarization force was measured with high accuracy, allowing non-contact topography profile measurements of liquid micro-and nanodroplets. The dependence of the contact angle on droplet height was determined in order to calculate the values of the spreading coefficient and the disjoining pressure between the liquid and substrates. The calculated potential energies give disjoining pressure values of similar to 0.4 atm for glycerol on HOPG, similar to 0.47 atm for glycerol on aluminum and similar to 13 atm for H2SO4 on HOPG. In the case of H2SO4 on HOPG the strength of the force appears to be thirty times bigger than that for glycerol on HOPG and aluminum.

We studied the wetting properties of glycerol on mica and stainless steel (SS) using the Scanning Polarization Force Microscopy (SPFM) technique. The precise control of the polarization force between a conductive atomic force microscope tip and a substrate allowed topography profile measurements of micro- and nanodroplets of liquid, opening the opportunity for the determination of the interaction between the liquid and the substrate: contact angle and surface potential energy between the surfaces versus height of droplets. The results of these experiments offer insights into the mechanisms of wetting phenomena at liquid-solid interfaces, at the nanometer scale.

Diffusion of a solute can be induced by the concentration gradient of another solute in solution. This transport mechanism is known as cross-diffusion. We have investigated cross-diffusion in a ternary protein-salt-water system. Specifically, we measured the two cross-diffusion coefficients for the lysozyme-NaCl-water system at 25 °C and pH 4.5 as a function of protein and salt concentrations by Rayleigh interferometry. One cross-diffusion coefficient characterizes salt osmotic diffusion induced by a protein concentration gradient, and is related to protein-salt thermodynamic interactions as described by the theories of Donnan membrane equilibrium and protein preferential hydration. The other cross-diffusion coefficient characterizes protein diffusiophoresis induced by a salt concentration gradient, and is described as the difference between a preferential-interaction coefficient and a transport parameter. We first relate our experimental results to the protein net charge and the thermodynamic excess of water near the protein surface. We then extract the Stefan-Maxwell diffusion coefficient describing protein-salt interactions in water. We find that the value of this coefficient is negative, contrary to the friction interpretation of Stefan-Maxwell equations. This result is explained by considering protein hydration. Finally, protein diffusiophoresis is quantitatively examined by considering electrophoretic and hydration effects on protein migration and utilized to accurately estimate lysozyme electrophoretic mobility. To our knowledge, this is the first time that protein diffusiophoresis has been experimentally characterized and a protein-salt Stefan-Maxwell diffusion coefficient reported. This work represents a significant contribution for understanding and modeling the effect of concentration gradients in protein-salt aqueous systems relevant to diffusion-based mass-transfer technologies and transport in living systems.

The theoretical spinodal for a ternary solution with an amphiphilic solvent is obtained using a generalized Wheeler-Widom model and a local fitting method applied to every experimental binodal point. This fitting method imposes that the theoretical binodal curve has to pass trough each representative binodal point and that its slope, in each point, must be equal (or as close as possible) to the slope of the corresponding representative experimental binodal. Using the fitting conditions for each experimental binodal, the corresponding theoretical spinodal point is derived, and the theoretical spinodal is constructed as the interpolation curve for the set of theoretical spinodal points. The results are in agreement with an older method where the local fitting between the theoretical model and the experimental data uses the experimental tie-lines.

A new method is presented to obtain a theoretical spinodal for ternary solutions with an amphiphile component. This method uses a generalized Wheeler-Widom model representing the ternary solution, and considers local fitting conditions with the experimental binodal, imposing that the theoretical binodal must pass through a point on the experimental binodal, and also that the slope of the theoretical binodal has to be as close as possible to the slope of the representative experimental binodal. Using the previously specified fitting conditions, the corresponding spinodal is derived. The results are in agreement with an older method of local fitting between the generalized Wheeler-Widom model and the experimental data, where the fitting condition implied the coincidence of the theoretical tie-line with the experimental tie-line.

We measured accurate NaCl main-term diffusion coefficients in aqueous lysozyme solutions at 25 degrees C and pH 4.5 using the Costing diffusiometer operated in its Rayleigh interferometric optical mode. The dependence of this diffusion coefficient on lysozyme concentration was examined using the obstruction-effect theory. Agreement between experimental results and theory is achieved if lysozyme proteins are treated as hydrated spheres with a hydration number of 240, a value that is comparable with those reported in literature for this protein. Electrostatic interactions and common-ion effects due to lysozyme net charge at pH 4.5 do not contribute significantly to the behavior of the NaCl diffusion coefficient within our experimental range of salt concentrations [(0.25 to 0.90) mol.dm(-3)].

The four mutual diffusion coefficients have been determined for two sets of homogeneous compositions of the water + chloroform + acetic acid system at 25 degrees C. By extrapolating the values of the diffusion coefficients determinant in the supersaturated region, we determined the spinodal compositions for two sets of experiments. The comparison between the experimental results and the theoretical prediction of the spinodal curve within an extended Wheeler-Widom model shows an excellent agreement.

A theoretical spinodal curve for the system water + chloroform + acetic acid at 25 °C is derived using a lattice model for ternary amphiphilic solutions: rod-like molecules covering the bonds of the honeycomb lattice with three-body interactions between the molecular ends associated to the same lattice site. The molecular model is equivalent to the standard Ising model on the same lattice; its mean-field solution is the most appropriate for reproducing, by local fitting, the experimental data for the binodal composition. The derived spinodal curve is in very good agreement with the spinodal composition determined also in the present work from the measured diffusion coefficients recently reported for the same system.

The partial molar volumes and the diffusion coefficients, D(ij), for the ternary system water-chloroform-acetic acid at 25 degrees C are reported at five compositions using different choices of solvent. The analyzed compositions have a fixed ratio between water and chloroform molar fractions and a decreasing amount of acetic acid, then approaching the binodal curve. The difficulty of interpreting the D(ij) is stressed and the use of different choices of solvent for the diffusive transport is suggested to extract from the diffusion coefficients all the possible information.

We consider a Hubbard chain with an energy difference between the odd and the even sites (ionicity). For a sufficiently large ionicity and electron concentrations less than half-filling, the system can be described by the one-band Hubbard model with a bond-site interaction. We investigate the competition between the density waves localized on sites and on bonds at different band fillings by solving an appropriate Bethe-Salpeter equation. Our results indicate the occurrence of the bond density waves at quarter-filling.

We consider a Hubbard chain with an energy difference Delta between the odd and even sites. The model, known as the one-dimensional ionic Hubbard model, is used to describe the neutral-ionic transition in mixed-stack charge-transfer organic crystals and the displacive-type ferroelectric transition in perovskite oxide compounds. We show that for sufficiently large Delta and electron densities less than half-filling the system reduces to the one-band Hubbard model with a bond-site interaction, model known as relevant to quasi-one-dimensional materials with a large conduction bandwidth.