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

Si nanoparticles as sensitizers for radio frequency-induced cancer hyperthermia

Conference on Synthesis and Photonics of Nanoscale Materials XIII, San Francisco, CA, FEB 15-17, 2016International audienceWe review our recently obtained data on the employment of Si nanoparticles as sensitizers of radiofrequency (RF) induced hyperthermia for mild cancer therapy tasks. Such an approach makes possible the heating of aqueous suspensions of Si nanoparticles by tens of degrees Celsius under relatively low intensities (1-5 W/cm2) of 27 MHz RF radiation. The heating effect is demonstrated for nanoparticles synthesized by laser ablation in water and mechanical grinding of porous silicon, while laser-ablated nanoparticles demonstrate a remarkably higher heating rate than porous silicon-based ones for the whole range of the used concentrations. The observed RF heating effect can be explained in the frame of a model considering the polarization of Si NPs and electrolyte in the external oscillating electromagnetic field and the corresponding release of heat by electric currents around the nanoparticles. Our tests evidence relative safety of Si nanostructures and their efficient dissolution in physiological solutions, suggesting potential clearance of nanoparticles from a living organism without any side effects. Profiting from Si nanoparticle-based heating, we finally demonstrate an efficient treatment of Lewis Lung carcinoma in vivo. The obtained data promise a breakthrough in the development of mild, non-invasive methods for cancer therapy

Radio frequency radiation-induced hyperthermia using Si nanoparticle-based sensitizers for mild cancer therapy

International audienceOffering mild, non-invasive and deep cancer therapy modality, radio frequency (RF) radiation-induced hyperthermia lacks for efficient biodegradable RF sensitizers to selectively target cancer cells and thus avoid side effects. Here, we assess crystalline silicon (Si) based nanomaterials as sensitizers for the RF-induced therapy. Using nanoparticles produced by mechanical grinding of porous silicon and ultraclean laser- ablative synthesis, we report efficient RF-induced heating of aqueous suspensions of the nanoparticles to temperatures above 45-50 degrees C under relatively low nanoparticle concentrations (< 1 mg/mL) and RF radiation intensities (1-5 W/cm(2)). For both types of nanoparticles the heating rate was linearly dependent on nanoparticle concentration, while laser-ablated nanoparticles demonstrated a remarkably higher heating rate than porous silicon-based ones for the whole range of the used concentrations from 0.01 to 0.4 mg/mL. The observed effect is explained by the Joule heating due to the generation of electrical currents at the nanoparticle/water interface. Profiting from the nanoparticle-based hyperthermia, we demonstrate an efficient treatment of Lewis lung carcinomain in vivo. Combined with the possibility of involvement of parallel imaging and treatment channels based on unique optical properties of Si-based nanomaterials, the proposed method promises a new landmark in the development of new modalities for mild cancer therapy

Bi‐Modal Nonlinear Optical Contrast from Si Nanoparticles for Cancer Theranostics

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