Deliberate and local increase of the temperature within solid tumors represents an effective therapeutic approach. Thermal therapies embrace this concept leveraging the capability of some species to convert the absorbed energy into heat. To that end, magnetic hyperthermia (MHT) uses magnetic nanoparticles (MNPs) that can effectively dissipate the energy absorbed under alternating magnetic fields. However, MNPs fail to provide real‐time thermal feedback with the risk of unwanted overheating and impeding on‐the‐fly adjustment of the therapeutic parameters. Localization of MNPs within a tissue in an accurate, rapid, and cost‐effective way represents another challenge for increasing the efficacy of MHT. In this work, MNPs are combined with state‐of‐the‐art infrared luminescent nanothermometers (LNTh; Ag2S nanoparticles) in a nanocapsule that simultaneously overcomes these limitations. The novel optomagnetic nanocapsule acts as multimodal contrast agents for different imaging techniques (magnetic resonance, photoacoustic and near‐infrared fluorescence imaging, optical and X‐ray computed tomography). Most crucially, these nanocapsules provide accurate (0.2 °C resolution) and real‐time subcutaneous thermal feedback during in vivo MHT, also enabling the attainment of thermal maps of the area of interest. These findings are a milestone on the road toward controlled magnetothermal therapies with minimal side effects.
We present computer simulation results for 1:1 and 2:1 electrolyte solutions in the presence of a gravitational field, using the Monte Carlo method in the NVT ensemble for the restrictive primitive model. Coulombic interactions were taken into account comparing the Ewald and Wolf methods. Three variations of Ewald summations were considered: the exact method for slab geometries (EW2D), and the three-dimensional (3D) versions with and without a dipolar correction (EW3DC and EW3D, respectively). The equivalent 3D Wolf protocols were applied under the same conditions (WF3DC and WF3D, respectively). The Wolf and Ewald methods agree accurately in the prediction of several thermodynamic and structural properties for these inhomogeneous systems: excess internal energies, isochoric heath capacities, and density and electrostatic potential profiles. The main advantage using the Wolf method is the significant saving in computing time, which is approximately six times faster than EW3D and EW3DC, and sixty times faster than EW2D.
In this article we present a NVT Monte Carlo computer simulation study of sedimentation of an electroneutral mixture of oppositely charged hard spherocylinders (CHSC) with aspect ratio L/σ = 5, where L and σ are the length and diameter of the cylinder and hemispherical caps, respectively, for each particle. This system is an extension of the restricted primitive model for spherical particles, where L/σ = 0, and it is assumed that the ions are immersed in an structureless solvent, i.e., a continuum with dielectric constant D. The system consisted of N = 2000 particles and the Wolf method was implemented to handle the coulombic interactions of the inhomogeneous system. Results are presented for different values of the strength ratio between the gravitational and electrostatic interactions, Γ = (mgσ)/(e(2)/Dσ), where m is the mass per particle, e is the electron's charge and g is the gravitational acceleration value. A semi-infinite simulation cell was used with dimensions Lx ≈ Ly and Lz = 5Lx, where Lx, Ly, and Lz are the box dimensions in Cartesian coordinates, and the gravitational force acts along the z-direction. Sedimentation effects were studied by looking at every layer formed by the CHSC along the gravitational field. By increasing Γ, particles tend to get more packed at each layer and to arrange in local domains with an orientational ordering along two perpendicular axis, a feature not observed in the uncharged system with the same hard-body geometry. This type of arrangement, known as tetratic phase, has been observed in two-dimensional systems of hard-rectangles and rounded hard-squares. In this way, the coupling of gravitational and electric interactions in the CHSC system induces the arrangement of particles in layers, with the formation of quasi-two dimensional tetratic phases near the surface.
The two-point correlation functions among particles confined to move within a spherical two-dimensional space are studied here using Monte Carlo simulations in the canonical ensemble and the corresponding liquid theory concepts. This work takes a simple model system with soft-sphere interactions among the particles lying on the spherical surface. We focus this study on the ordering induced by the particle packing and the restrictions imposed by the system topology. The corresponding grand canonical results are obtained from the canonical Monte Carlo data using the standard statistical mechanics formulas. These grand canonical ensemble results show that as the strength of the interactions increases, the system transits between liquidlike states and crystal-like states as the average number of particles on the spherical surface matches certain specific values. The crystal-like states correspond to sharp minima in the plot of the standard deviation in the number of particles on the spherical surface versus the average value of this number. We also test the validity of the integral equation approaches for this kind of closed but boundless systems: It is found that the Percus-Yevick approximation overestimates the correlations for this system in a liquid state, whereas the hypernetted-chain approximation underestimates these correlations.
Different Monte Carlo simulation approaches are used here to study the static structure induced by a spherical neutral substrate inserted in the midst of a two-dimensional suspension of paramagnetic particles. It is then observed that in some instances some of these particles are adsorbed to the surface of the substrate, forming colloidal halos. We investigate the necessary conditions for the formation of these halos and the dependence of the number of adsorbed particles on the relevant parameters of the system. The angular distribution of the adsorbed particles around the perimeter of the substrate is analyzed here too.
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