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1.
Beilstein J Nanotechnol ; 14: 23-33, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-36703908

RESUMO

The present paper considers a mathematical model describing the time evolution of spin states and magnetic properties of a nanomaterial. We present the results of two variants of nanosystem simulations. In the first variant, cobalt with a structure close to the hexagonal close-packed crystal lattice was considered. In the second case, a cobalt nanofilm formed in the previously obtained numerical experiment of multilayer niobium-cobalt nanocomposite deposition was investigated. The sizes of the systems were the same in both cases. For both simulations, after pre-correction in the initial time stages, the value of spin temperature stabilized and tended to the average value. Also, the change in spin temperature occurred near the average value. The system with a real structure had a variable spin temperature compared to that of a system with an ideal structure. In all cases of calculations for cobalt, the ferromagnetic behavior was preserved. Defects in the structure and local arrangement of the atoms cause a deterioration in the magnetic macroscopic parameters, such as a decrease in the magnetization modulus.

2.
Pharmaceutics ; 14(11)2022 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-36365090

RESUMO

A series of new composite materials based on Fe3O4 magnetic nanoparticles coated with SiO2 (or aminated SiO2) were synthesized. It has been shown that the use of N-(phosphonomethyl)iminodiacetic acid (PMIDA) to stabilize nanoparticles before silanization ensures the increased content of a SiO2 phase in the Fe3O4@SiO2 nanocomposites (NCs) in comparison with materials obtained under similar conditions, but without PMIDA. It has been demonstrated for the first time that the presence of PMIDA on the surface of NCs increases the level of Dox loading due to specific binding, while surface modification with 3-aminopropylsilane, on the contrary, significantly reduces the sorption capacity of materials. These regularities were in accordance with the results of quantum chemical calculations. It has been shown that the energies of Dox binding to the functional groups of NCs are in good agreement with the experimental data on the Dox sorption on these NCs. The mechanisms of Dox binding to the surface of NCs were proposed: simultaneous coordination of Dox on the PMIDA molecule and silanol groups at the NC surface leads to a synergistic effect in Dox binding. The synthesized NCs exhibited pH-dependent Dox release, as well as dose-dependent cytotoxicity in in vitro experiments. The cytotoxic effects of the studied materials correspond to their calculated IC50 values. NCs with a SiO2 shell obtained using PMIDA exhibited the highest effect. At the same time, the presence of PMIDA in NCs makes it possible to increase the Dox loading, as well as to reduce its desorption rate, which may be useful in the design of drug delivery vehicles with a prolonged action. We believe that the data obtained can be further used to develop stimuli-responsive materials for targeted cancer chemotherapy.

3.
Sci Rep ; 12(1): 20405, 2022 Nov 27.
Artigo em Inglês | MEDLINE | ID: mdl-36437373

RESUMO

In the present study, we investigate arc plasma expansion in an industrial vacuum arc remelting (VAR) process using experimental and numerical tools. Stainless steel is the alloy of interest for the electrode (cathode) and ingot (anode). During the operation of the VAR process, behaviors of cathode spots and plasma arc were captured using the high-speed camera (Phantom v2512). We found that spots prefer to onset and remain within the partially melted surface at the center of the electrode tip. Existing spots outside the melting zone accelerate toward the edge of the electrode to extinguish. We observed a fairly symmetrical and centric plasma column during the operation. For further investigation of the observed arc column in our experiment, we used the two-fluid magnetohydrodynamics (MHD) model of plasma proposed by Braginskii. Thus, we modeled the arc column as a mixture of two continuous interpenetrating compressible fluids involving ions and electrons. Through numerical simulations, we calculated plasma parameters such as number density of ions/electrons, electric current density, flow of ions/electrons, temperature of ions/electrons, and light intensity for the observed arc column in our experiment. The calculated light intensity of plasma was compared with images captured by the camera to verify the model. The distribution of electric current density along the surface of the anode, namely ingot, is a decisive parameter that impacts the quality of the final product (ingot) in VAR process. Herein, we confirm that the traditionally used Gaussian distribution of electric current density along the surface of the ingot is viable.


Assuntos
Indústrias , Plasma , Vácuo , Eletrodos , Eletricidade
4.
Int J Mol Sci ; 23(16)2022 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-36012356

RESUMO

Novel nanocomposite materials based on Fe3O4 magnetic nanoparticles (MNPs) coated with silica and covalently modified by [(3-triethoxysilyl)propyl]succinic acid-polyethylene glycol (PEG 3000) conjugate, which provides a high level of doxorubicin (Dox) loading, were obtained. The efficiency of Dox desorption from the surface of nanomaterials under the action of an alternating magnetic field (AMF) in acidic and neutral media was evaluated. Their high cytotoxicity against tumor cells, as well as the drug release upon application of AMF, which leads to an increase in the cytotoxic effect, was demonstrated.


Assuntos
Nanopartículas de Magnetita , Nanopartículas , Neoplasias , Linhagem Celular , Doxorrubicina/farmacologia , Portadores de Fármacos , Humanos , Concentração de Íons de Hidrogênio , Fenômenos Magnéticos , Polietilenoglicóis , Dióxido de Silício
5.
Opt Lett ; 47(4): 778-781, 2022 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-35167523

RESUMO

For the first time, to the best of the authors' knowledge, a cladding-pumped bismuth-doped fiber laser (BDFL) is demonstrated. A "home-made" Bi-doped germanosilicate fiber with a 125 µm circular outer cladding made of fused silica and coated by a low refractive index polymer is used as an active medium pumped by commercial multimode laser diodes with a total output power of 25 W at 808 nm. We find that the BDFL with a free-running cavity (when feedback is provided by ≈4% back reflection from two bare right-angle cleaved fiber ends) composed of a 100-m-long bismuth-doped fiber is capable of emitting at a wavelength of 1440 nm. A slope efficiency of 0.5% with respect to the absorbed pump power with a maximum output power of ≈50 mW is obtained in a BDFL with a cavity formed by a highly reflective Bragg grating at 1461 nm and a right-angle cleaved fiber end. The beam quality factors (M2) of the output BDFL in the horizontal and vertical directions are measured to be 1.18 and 1.13, respectively. The processes affecting the efficiency of the BDFLs are also discussed. The possible improvements for the output power scaling and increasing the efficiency of the cladding-pumped BDFLs are proposed.

6.
Beilstein J Nanotechnol ; 11: 1776-1788, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33299737

RESUMO

This work is a study of the formation processes and the effect of related process parameters of multilayer nanosystems and devices for spintronics. The model system is a superconducting spin valve, which is a multilayer structure consisting of ferromagnetic cobalt nanolayers separated by niobium superconductor nanolayers. The aim was to study the influence of the main technological parameters including temperature, concentration and spatial distribution of deposited atoms over the nanosystem surface on the atomic structure and morphology of the nanosystem. The studies were carried out using the molecular dynamics method using the many-particle potential of the modified embedded-atom method. In the calculation process the temperature was controlled using the Nose-Hoover thermostat. The simulation of the atomic nanolayer formation was performed by alternating the directional deposition of different composition layers under high vacuum and stationary temperature conditions. The structure and thickness of the formed nanolayers and the distribution of elements at their interfaces were studied. The alternating layers of the formed nanosystem and their interfaces are shown to have significantly different atomic structures depending on the main parameters of the deposition process.

8.
Phys Chem Chem Phys ; 13(20): 9863-70, 2011 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-21499626

RESUMO

A nanocapsule for high-effective methane storage is investigated using molecular dynamics simulation. Methane molecules are pumped into a nanocapsule via pumping and locking chambers by the K@C(60)(1+) ions moved by the electric field. When such a technique is used, the methane weight content in the nanocapsule reaches 36.4 wt%. At the methane storage stage the external thermodynamic conditions are normal. This paper presents the analysis of the processes taking place during the nanocapsule charging with methane, its storage and desorption.

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