Radiofrequency Hyperthermia of Cancer Cells Enhanced by Silicic Acid Ions Released during the Biodegradation of Porous Silicon Nanowires

The radiofrequency (RF) mild hyperthermia effect sensitized by biodegradable nanoparticles is a promising approach for therapy and diagnostics of numerous human diseases including cancer. Herein, we report the significant enhancement of local destruction of cancer cells induced by RF hyperthermia in the presence of degraded low-toxic porous silicon (PSi) nanowires (NWs). Proper selection of RF irradiation time (10 min), intensity, concentration of PSi NWs, and incubation time (24 h) decreased cell viability to 10%, which can be potentially used for cancer treatment. The incubation for 24 h is critical for degradation of PSi NWs and the formation of silicic acid ions H+ and H3SiO4- in abundance. The ions drastically change the solution conductivity in the vicinity of PSi NWs, which enhances the absorption of RF radiation and increases the hyperthermia effect. The high biodegradability and efficient photoluminescence of PSi NWs were governed by their mesoporous structure. The average size of pores was 10 nm, and the sizes of silicon nanocrystals (quantum dots) were 3-5 nm. Degradation of PSi NWs was observed as a significant decrease of optical absorbance, photoluminescence, and Raman signals of PSi NW suspensions after 24 h of incubation. Localization of PSi NWs at cell membranes revealed by confocal microscopy suggested that thermal poration of membranes could cause cell death. Thus, efficient photoluminescence in combination with RF-induced cell membrane breakdown indicates promising opportunities for theranostic applications of PSi NWs. © 2019 American Chemical Society

Low-Load Metal-Assisted Catalytic Etching Produces Scalable Porosity in Si Powders

The recently discovered low-load metal-assisted catalytic etching (LL-MACE) creates nanostructured Si with controllable and variable characteristics that distinguish this technique from the conventional high-load variant. LL-MACE employs 150 times less metal catalyst and produces porous Si instead of Si nanowires. In this work, we demonstrate that some of the features of LL-MACE cannot be explained by the present understanding of MACE. With mechanistic insight derived from extensive experimentation, it is demonstrated that (1) the method allows the use of not only Ag, Pd, Pt, and Au as metal catalysts but also Cu and (2) judicious combinations of process parameters such as the type of metal, Si doping levels, and etching temperatures facilitate control over yield (0.065−88%), pore size (3−100 nm), specific surface area (20−310 m2·g−1), and specific pore volume (0.05−1.05 cm3·g−1). The porous structure of the product depends on the space-charge layer, which is controlled by the Si doping and the chemical identity of the deposited metal. The porous structure was also dependent on the dynamic structure of the deposited metal. A distinctive comet-like structure of metal nanoparticles was observed after etching with Cu, Ag, Pd, and, in some cases, Pt; this structure consisted of 10−50 nm main particles surrounded by smaller (\u3c5 nm) nanoparticles. With good scalability and precise control of structural properties, LL-MACE facilitates Si applications in photovoltaics, energy storage, biomedicine, and water purification

Prospects for the Development of the Russian Payment Infrastructure in the Сontext of the Transformation of the Global Financial System

In the article, the author analyzes the impact of factors affecting the global financial system in the payment sphere. The analysis is based on a comparison of the set of impact factors, as noted in the materials of the World Economic Forum, with trends in the development of payment infrastructure. We show the manifestation of this influence in various aspects and properties, both for separate payment systems, and the payment sphere as a whole.The author notes that not only regulation based on international standards, but also changes in market conditions and technological innovations have a significant impact on the development of payment systems of central banks. The impact of factors in the Russian national payment system (NPS) and the role of the Bank of Russia are revealed.The author concludes that the degree of influence of the factors manifested in the implementation of planned and possible measures for the development of the NPS can be estimated by the dynamics of growth (deviation) of the share of payment traffic carried out in significant payment infrastructures. Quantitative indicators of the NPS development, presented in terms of factors and related activities affecting the global financial system, make it possible to assess the degree of mutual influence

Estimation of the parameters of asteroid movement using Beale’s nonlinearity measure

Beale’s nonlinearity estimation algorithm is adapted for solving asteroid problems. It has been tested for model and actual asteroids. It is shown that this algorithm underestimates the nonlinearity. Modifications of Beale’s nonlinearity measure are considered that allow its accuracy to be increased

MODELING OF REGIONS OF ASTEROID POSSIBLE MOTION

Peculiar properties of construction of initial regions of asteroids' possible motion from observational data in the form of probabilistic ellipsoids are investigated. For the objects which observed only in one appearance, this problem may be essentially nonlinear, and the usual method for their construction with the help of linear estimations of covariance matrices may became unacceptable. In order to make possible application of the linear estimation methods which has been developing in mathematical statistics the problem of decreasing nonlinearity is discussed. The solution of this problem with the help of appropriate system of initial parameters of asteroid orbits choice, as well as initial time and weighting matrices of observational errors is proposed. Efficiency of such technique had justified by numerical experiments with the usage of model and real observations

Stochastic simulation of orbital uncertainty of potentially hazardous asteroids observed in one appearance

The paper discusses some features in stochastic simulation of the orbital uncertainty of potentially hazardous asteroids observed in one appearance (opposition). Due to scant observational information, most of these asteroids have huge orbital uncertainties which can be difficult for stochastic simulation because of the strong nonlinearity of the inverse problem. In the paper we present different stochastic methods for simulation of orbital uncertainty and analyze their efficiency; using an original nonlinearity indicator, investigate the nonlinearity for all potentially hazardous asteroids observed in one opposition; consider the conditions that entail strong nonlinearity as well as the causes of falsely strong nonlinearity

Electrolytic conductivity-related radiofrequency heating of aqueous suspensions of nanoparticles for biomedicine.

The development of suitable contrast agents can significantly enhance the efficiency of modern imaging and treatment techniques, such as thermoacoustic (TA) tomography and radio-frequency (RF) hyperthermia of cancer. Here, we examine the heating of aqueous suspensions of silicon (Si) and gold (Au) nanoparticles (NPs) under RF irradiation in the MHz frequency range. The heating rate of aqueous suspensions of Si NPs exhibited non-monotonic dependency on the electrical conductivity of the suspension. The experimental results were explained by the mathematical model considering oscillating solvated ions as the main source of Joule heating. These ions could be the product of the dissolution of Si NPs or organic coating of Au NPs. Thus, the ions governed the conductivity of the suspensions, which in turn governs both the heating rate and the near-field RF TA response. The model predicted the contrast in different tissues taking into account both Joule heating and dielectric losses

Modeling of Heat Release in Aqueous Suspensions of Solid-State Nanoparticles under Electromagnetic Radio-Frequency Irradiation

Conference on Synthesis and Photonics of Nanoscale Materials XIII, San Francisco, CA, FEB 15-17, 2016International audienceWe examine absorption of electromagnetic radio-frequency (RF) radiation in aqueous suspensions of semiconductor (silicon) and metal (gold) nanoparticles (NPs) and theoretically investigate the heat release in these systems. The absorption of RF radiation is considered in both bulk electrolyte and the region around the NPs. Simulations show a strong dependence of the heating rate on electrical conductivity of the electrolyte rather than on that of NPs properties. The obtained results indicate that NPs can act as sensitizers of the RF induced hyperthermia for biomedical applications