Electron cyclotron converters of microwaves in wireless power transmission systems

A proposal to use special electron cyclotron devices as effective converters of electromagnetic waves into direct current in modern microwave systems for wireless transmission of electrical energy to the Earth via a microwave channel from solar space power plants located on board geostationary satellites is considered. Such converters are a product of domestic development, they can have a conversion efficiency of more than 80%, they are insensitive to overloads and are several orders of magnitude more economical than the well-known semiconductor rectennas (rectifying antennas). Semiconductor rectennas, assembled from a multitude of individual semiconductor diodes with a Schottky barrier, in the process of nonlinear conversion of microwaves, generate parasitic radiation that forms a powerful electromagnetic background, which seriously interferes with the stable operation of information systems of special and general civil communications. In addition, the cost of semiconductor rectennas is several orders of magnitude higher than that of electron-cyclotron converters with the same input microwave power. Due to the high compactness of the electronic converters, they can also be installed on an intermediate satellite platform in the stratosphere, receiving the energy of the Sun through a laser beam from a geostationary orbit and transmitting it to the Earth with practically no loss through the microwave channel. The possibilities of using electron cyclotron converters in ground-based systems for wireless energy transmission are also promising. Already the first electron cyclotron converters, created at the Torii enterprise according to the project of the Lomonosov Moscow State University, had an efficiency of over 60% at an input microwave power of 10 kW

Neuroprotective Effects of Mitochondria-Targeted Plastoquinone in a Rat Model of Neonatal Hypoxic–Ischemic Brain Injury

Neonatal hypoxia–ischemia is one of the main causes of mortality and disability of newborns. To study the mechanisms of neonatal brain cell damage, we used a model of neonatal hypoxia–ischemia in seven-day-old rats, by annealing of the common carotid artery with subsequent hypoxia of 8% oxygen. We demonstrate that neonatal hypoxia–ischemia causes mitochondrial dysfunction associated with high production of reactive oxygen species, which leads to oxidative stress. Targeted delivery of antioxidants to the mitochondria can be an effective therapeutic approach to treat the deleterious effects of brain hypoxia–ischemia. We explored the neuroprotective properties of the mitochondria-targeted antioxidant SkQR1, which is the conjugate of a plant plastoquinone and a penetrating cation, rhodamine 19. Being introduced before or immediately after hypoxia–ischemia, SkQR1 affords neuroprotection as judged by the diminished brain damage and recovery of long-term neurological functions. Using vital sections of the brain, SkQR1 has been shown to reduce the development of oxidative stress. Thus, the mitochondrial-targeted antioxidant derived from plant plastoquinone can effectively protect the brain of newborns both in pre-ischemic and post-stroke conditions, making it a promising candidate for further clinical studies

Gadolinium-Doped Carbon Nanoparticles with Red Fluorescence and Enhanced Proton Relaxivity as Bimodal Nanoprobes for Bioimaging Applications

Carbon-based nanoparticles (CNPs) have demonstrated great potential in biomedical applications because of their unique physical and chemical properties, and excellent biocompatibility. Herein, we have studied two types of CNPs with gadolinium (Gd) impurities (Gd-CNPs), which were prepared by microwave synthesis (MWS) and hydrothermal synthesis (HTS), for potential applications as photoluminescent (PL) labels and contrast agents in magnetic resonance imaging (MRI). The prepared Gd-CNPs were investigated by means of transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy, UV–visible absorption spectroscopy, and magnetic-resonance relaxometry, which allowed us to reveal specific features and functional properties of the prepared samples. While the TEM data showed similar size distributions of both types of Gd-CNPs with mean sizes of 4–5 nm, the optical absorption spectroscopy showed higher absorption in the visible spectral region and stronger PL in the red and near-infrared (NIR) spectral regions for the MWS samples in comparison with those prepared by HTS. Under green light excitation the former samples exhibited the bright red-NIR PL with quantum efficiency of the order of 10%. The proton relaxometry measurements demonstrated that the HTS samples possessed longitudinal and transverse relaxivities of about 42 and 70 mM−1s−1, whereas the corresponding values for the MWS samples were about 8 and 13 mM−1s−1, respectively. The obtained results can be useful for the selection of appropriate synthesis conditions for carbon-based nanoparticles for bimodal bioimaging applications