A high-power periodic nanosecond pulse source of coherent 8-cm electromagnetic radiation

The generation of short electromagnetic pulses excited in an extended slow-wave system (SWS) of a relativistic backward wave tube (BWT) operating in the so-called superradiance regime with a carrier frequency of 3.7 GHz has been simulated and experimentally studied. At a decreased magnetic field (about 0.2 T) in the SWS, the BWT generated 2.5-ns microwave pulses with a power of up to 800 MW. At a pulse repetition rate of 100 Hz, the working life of the system was limited by the lifetime of an explosive emission cathode (10⁶ pulses). The possibility of phase synchronization of the high-frequency field of the relativistic microwave oscillator with respect to the voltage pulse front is demonstrated for the first time.     

Acoustic-Emission Monitoring of Airframe Failure under Cyclic Loading

Russian Journal of Nondestructive Testing - The structural–phenomenological approach used to classify and split acoustic-emission signals into energy clusters, together with the parameters of...     

Theoretical Analysis of Mechanical Vibrations

Russian Engineering Research - A method is proposed for transforming a mechanical system described by arbitrary generalized coordinates into a system described by primary coordinates. To this end,...     

A Novel Photoswitchable Azobenzene-Containing Local Anesthetic Ethercaine with Light-Controlled Biological Activity In Vivo

Pain is a common symptom that impairs the quality of life for people around the world. Local anesthetics widely used for pain relief have a number of side effects, which makes the development of both new drugs and new ways to control their activity particularly important. Photopharmacology makes it possible to reduce the side effects of an anesthetic and control its biological activity in the body. The purpose of this work was to create a new light-controlled local anesthetic and study its biological activity in animals. A compound with a simple scheme of synthesis was chosen to shift the UV-Vis absorption band towards the visible range of the spectrum and was synthesized for the first time. Some computer calculations were performed to make sure that the aforementioned changes would not lead to loss of biological activity. The micellar form of the new compound was prepared, and in vivo biological studies were carried out in rabbits. The existence of a local anesthetic effect, which disappeared almost completely on irradiation with light (λ = 395 nm), was shown using the surface anesthesia model. Moreover, the possibility of multiple reversible changes in the biological activity of ethercaine under the action of light was demonstrated. The latter compound manifests no local irritating effect, either. The data obtained indicate the prospects for the development of new compounds based on azobenzene for light-controlled local anesthesia.     

Growth of GaN by molecular-beam epitaxy with activation of the nitrogen by a capacitive rf magnetron discharge

It is shown that GaN films can be grown by molecular-beam epitaxy with plasma activation of the nitrogen by a magnetron rf discharge in a specially constructed coaxial source with capacitive coupling. A growth rate of ∼0.1 μm/h is obtained on GaAs and sapphire substrates, and ways are found for optimizing the design of the plasma source in order to increase the growth rate. The electrophysical and luminescence properties of undoped epitaxial films are investigated at temperatures ranging all the way to room temperature. Pis’ma Zh. Tekh. Fiz. 24, 30–35 (June 26, 1998)