Piezoelectric energy nanoharvester based on an array of ZnO whisker nanocrystals and a flat copper electrode

A piezoelectric low-power nanogenerator based on an array of ZnO whisker nanocrystals and a movable flat top electrode has been developed. It has been shown that this element generates ac current under the effect of mechanical vibrations with a frequency up to 100 Hz, which makes it possible to accumulate the capacitor charge. The investigation of the sample on a vibration stand under the acceleration of 9.8 m/s² has demonstrated that the stable variable signal from 50 mV to 1.5 V appears at a frequency of 20–120 Hz. The experimental dependence of the generated voltage on the weight of the load applied to the top electrode is obtained. The appearance of the ac signal is explained in the context of the classical piezoelectric effect, namely, the ZnO whisker nanocrystals in the starting state are already bent, and the different-sign charges are generated under the effect of mechanical vibrations during bending and unbending.     

Possibility of radionuclide production for PET diagnostics and brachyteraphy on the INR RAS linac

The technology of radionuclide production for positron-emission tomography on the proton linac of the Institute for Nuclear Research, Russian Academy of Sciences, is considered. A prototype of a combined target unit for production of positron-emitting radionuclides ¹¹C, ¹³N, and ¹⁸F in the proton linac beam is presented. The production of medical isotopes ¹⁰³Pd, ^{124, 125}I, and ¹³¹Cs is briefly discussed.     

Density matrix of a quantum field in a particle-creating background

We examine the time evolution of a quantized field in external backgrounds that violate the stability of vacuum (particle-creating backgrounds). Our purpose is to study the exact form of the final quantum state (the density operator at the final instant of time) that has emerged from a given arbitrary initial state (from a given arbitrary density operator at the initial time instant) in the course of evolution. We find a generating functional that allows one to obtain density operators for an arbitrary initial state. Averaging over states of the subsystem of antiparticles (particles), we obtain explicit forms of reduced density operators for the subsystem of particles (antiparticles). Analyzing one-particle correlation functions, we establish a one-to-one correspondence between these functions and the reduced density operators. It is shown that in the general case a presence of bosons (e.g., gluons) in the initial state increases the creation rate of the same type of bosons. We discuss the question (and its relation to the initial stage of quark–gluon plasma formation) whether a thermal form of one-particle distribution can appear even if the final state of the complete system is not in thermal equilibrium. In this respect, we discuss some cases when pair-creation by an electric-like field can mimic the one-particle thermal distribution. We apply our technics to some QFT problems in slowly varying electric-like backgrounds: electric, SU(3) chromoelectric, and metric. In particular, we analyze the time and temperature behavior of the mean numbers of created particles, provided that the effects of switching the external field on and off are negligible. It is demonstrated that at high temperatures and in slowly varying electric fields the rate of particle-creation is essentially time-dependent.     

Investigation of Eco-Friendly Gas Mixture for Gas Discharge Particle Detectors

Physics of Atomic Nuclei - The first results of studying the Ar/CO2/HFO1234ze eco-friendly gas mixture for gas discharge detectors are presented. The work is performed using a prototype multiwire...     

Localization of the copper-containing component in the pore volume of zeolite ZSM-5

The distribution of the copper-containing component in the pore volume of zeolite ZSM-5 has been investigated by H₂ and N₂ adsorption at 77 K and IR spectroscopy. Samples were synthesized by ion exchange and incipient wetness impregnation. Copper-containing clusters are mostly located on the surface of the mesopores formed by packed zeolite nanocrystallites. This causes partial blocking of the volume of microporous channels for N₂ molecules, but these channels remain accessible for H₂ molecules. It has been deduced that no considerable amount of copper located in the structural channels of the zeolite. According to IR spectroscopic data, the sorption of copper ions in the Cu/ZSM-5 catalysts takes place on extraframe-work aluminum, which forms Al-OH-Al bridges and terminal Al-OH groups, and on terminal Si-OH groups located on the zeolite crystal surface.