Electrostatic frequency reduction: A negative stiffness mechanism for measuring dissipation in a mechanical oscillator at low frequency.

Broadband seismometers and gravitational wave detectors make use of mechanical resonators with a high quality factor to reduce Brownian noise. At low frequency, Brownian noise is ultimately dominated by internal friction in the suspension, which has a 1/f noise compared with the white noise arising from viscous dissipation. Internal friction is typically modeled as a frequency-dependent loss and can be challenging to measure reliably through experiment. In this work, we present the physics and experimental implementation of electrostatic frequency reduction (EFR) in a mechanical oscillator-a method to measure dissipation as a function of frequency. By applying a high voltage to two parallel capacitor plates, with the center plate being a suspended mass, an electrostatic force is created that acts as a negative stiffness mechanism to reduce the system's resonance frequency. Through EFR, the loss angle can be measured as a function of frequency by measuring amplitude decay response curves for a range of applied voltages. We present experimental measurements of the loss angle for three metal helical extension springs in the nominal frequency range 0.7-2.9 Hz at 0.2 Hz intervals, demonstrating the possibility for fine adjustment of the resonance frequency for loss angle measurements. A quality factor proportional to the resonance frequency squared was measured, an indication that internal friction and other non-viscous dissipation elements, such as electrostatic damping, were the prominent loss mechanisms in our experiments. Finally, we consider the implications of Brownian noise arising from internal friction on a low 1/f noise seismometer.

[Hygienic characteristics of work conditions for main occupations in asbestos cement production of Ukraine].

Studies covered of work conditions for main occupations in asbestos cement production of Ukraine. Studies covered work conditions and occupational features of workers engaged into main occupations in asbestos cement enterprises of Ukraine. Parameters presented characterize ambient air state, microclimate conditions, levels of noise and vibration, work intensity and hardness.

Observation of the ideal Josephson effect in superfluid 4He.

Superfluids and superconductors are the only states of condensed matter that can be described by a single wavefunction, with a coherent quantum phase Phi. The mass flow in a superfluid can be described by classical hydrodynamics for small flow velocity, but above a critical velocity, quantized vortices are created and the classical picture breaks down. This can be observed for a superfluid flowing through a microscopic aperture when the mass flow is measured as a function of the phase difference across the aperture; the curve resembles a hysteretic sawtooth where each jump corresponds to the creation of a vortex. When the aperture is made small enough, the system can enter the so-called 'ideal' Josephson regime, where the superfluid mass flow becomes a continuous function of the phase difference. This regime has been detected in superfluid 3He, but was hitherto believed to be unobservable, owing to fluctuations, in 4He. Here we report the observation of the ideal Josephson effect in 4He. We study the flow of 4He through an array of micro-apertures and observe a transition to the ideal Josephson regime as the temperature is increased towards the superfluid transition temperature, Tlambda.

[The effect of manufacturing factors in asphalt-bitumen plants on the health of the workers]. / Vliianie proizvodstvennykh faktorov asfal'tobitumnykh zavodov na zdorov'e rabotaiushchikh.

Comprehensive investigations designate to study the working conditions and health status of workers of asphalt-bitumen plants were conducted. Measurable in the breathing zone of workers of basic professions were toxic substances that have a toxic effect on the body (benzene, oil hydrocarbons, toluene, nitric, carbonic oxides, and benz(a)pyrene). There was noted a high incidence of abnormalities of the internal organs, with the cardiovascular and respiratory pathology ranking first in frequency to other disorders. Studies on the allergologic and atopic status showed that as far as the development of the respiratory organ pathology and the external breathing functional shifts are concerned, the immunity status-related specificities of the body are to be considered along with in-plant factors. Measures have been designed aimed to prevent the development of disorders.