Glasses, which are important materials for photonics, have inherent fluctuations of elastic constants on the nanometer scale. The heterogeneous elasticity theory connects these fluctuations with the boson peak, a characteristic feature of the vibrational spectra of glasses in THz frequency range. We use a version of this theory to find the temperature dependence of shear modulus nanometer-scale fluctuations in glycerol, a paradigmatic glass-former, in the supercooled and liquid state. The main input parameter of the theory is the frequency of the boson peak, determined from light scattering spectra. We measured the Landau–Placzek ratio in glycerol at the same temperatures and found out that its temperature dependence is in a good agreement with that of the normalized mean-square fluctuation of the shear modulus.

Using a method of low frequency Raman scattering, hydrated planar samples of phospholipid bilayers are studied at room temperature. It has been demonstrated that a relaxation response, the spectral shape of which corresponds to a wide distribution of relaxation times in the picosecond range, is manifested in the subterahertz range. The spectral susceptibility of the relaxation response is described by a power function with an exponent of 0.25, is the same for gel and fluid phases of phospholipid bilayers, and does not depend on the degree of saturation of hydrocarbon tails of different phospholipids. The subterahertz relaxation response can be considered as an elementary relaxation event, which precedes slower relaxation processes such as lateral diffusion and changes in the thickness or curvature of a phospholipid bilayer.

Measurements and correlation analysis of radon and aeroion concentrations in the underground laboratory were carried out. For pairs of variables “pressure — radon” and “pressure — ions”, a delayed pumping effect was found, similar to that previously observed for neutrons and gamma quanta. A simple phenomenological model explaining the results is presented. In this model, the reason for the delay is the gradual accumulation of radon in the room with a decrease in atmospheric pressure. The balance of the radon accumulation rate, the time of its radioactive decay and the characteristic time of pressure variations leads to an effective delay of 2 days between atmospheric pressure variations and radon concentration. Correlation analysis for the variables “pressure — ions” indicates that ions formed in the pores of the soil are already present in the air carrying radon to the laboratory. These ions make up approximately 21% of the total number of ions in the laboratory.

There is the rapid growth in application of Brillouin scattering spectroscopy to biomedical objects in order to characterize their mechanoelastic properties in this way. However, the possibilities and limitations of the method when applied to tissues have not yet been clarified. Here, applicability of Brillouin spectroscopy for testing the elastic response of medically relevant tissues of bovine jugular vein and pericardium was considered. Parameters of the Brillouin peak were studied for samples untreated, diepoxide-fixed, and preserved after treatment in alcohol solutions. It was found that diepoxide cross-linking resulted to a slight tendency to increase the Brillouin position for hydrated tissues. The variations in the position and width of the Brillouin peaks, associated with local fluctuations in water concentration, were reduced after diepoxide treatment in the case of the pericardium, but not in the case of the vein wall. To obtain more information about the elastic response of the protein scaffold without the participation of water, dried samples were also studied. Brillouin spectra of the dried pericardium and vein wall revealed a significant increase in the Brillouin peak position (elastic modulus) after conservation in alcohol. In the case of the vein wall, this effect was found for both collagen and elastin-related peaks, which were identified in the Brillouin spectrum. This result corresponds to a denser packing of fibrous proteins after preservation in alcohol solutions. The ability of Brillouin spectroscopy to independently characterize the effect of treatment on the instantaneous elastic modulus of various tissue components is also attractive for its application in the development of new materials for bioimplants. A comparison of the Brillouin longitudinal and Young's elastic moduli determined for the hydrated samples of the vein and pericardium showed that there is no clear correspondence between these material parameters. The usefulness of using both experimental methods to obtain new information about the elastic response of the material is discussed.

An Erratum to this paper has been published: https://doi.org/10.1134/S1062873824010027

The effect of atmospheric pressure on the counting rate for natural-radioactivity gammas measured at the Large Volume Detector (LVD) in the continuous-monitoring mode is studied. Gamma emissions in the time series are associated with radon emanation from rock in the underground experimental hall. No direct relationship between changes in the pressure and in the counting rate for gammas is found on the basis of an analysis of hourly data. Also, no delayed pumping effect for gammas is observed during sharp pressure drops. A strong anticorrelation between the trends in the change in counting rate for gammas and the change in pressure is revealed on the scale of three to four months.

The LVD (Large Volume Detector), located at the Low Background Laboratory, Gran Sasso, Italy, is built to detect neutrinos from stellar core collapses in our Galaxy. The peculiarity of the search for rare events requires close attention to the background of the experiment, such as the natural radioactivity of the rock and detector materials and the interaction of cosmic ray muons underground. The LVD is capable of detecting gamma quanta from the decay of radon daughter nuclei. We convincingly show the connection between the change in the background counting rate from gammas in the detector and the change in the concentration of radon nuclei in the experimental hall. We also point out the existence of another source of radon change, this is seismic activity.

A study is performed of variations in the count rate of detector background pulses in the LVD experiment (Gran Sasso, Italy). Such variations are caused by the injection of radon from the rock into the experimental hall. Dependences are presented for variations in the air pressure on the Earth’s surface and in the experimental hall of the LVD, along with others in the count rate of LVD events associated with changes in the concentration of radon.

The ability of salts to change the macroscopic viscosity of their aqueous solutions is described by the Jones-Dole equation with B-coefficient for the linear concentration term. The sign and value of this coefficient are often considered as a measure of the salt's structure-making/breaking ability, while the validity of this assignment is still under discussion. Here, by applying Raman and Brillouin scattering spectroscopy to various salts from the Hofmeister series, we studied a possible relation between macroscopic Jones-Dole's B-coefficient and the microscopic dynamic response. Raman spectroscopy provides information about molecular vibrations and Brillouin spectroscopy about acoustic phonons with wavelengths of hundreds of nanometers. It has been found that Jones-Dole's B-coefficient correlates linearly with the coefficients, describing the concentration dependences of the average OH stretching frequency, real and imaginary parts of gigahertz elastic modulus. These relationships have been interpreted to mean that the OH stretching frequency is a measure of the ion-induced changes in the water network that cause changes in both viscosity and gigahertz relaxation. Depolarized inelastic light scattering revealed that the addition of structure-making ions not only changes the frequency of the relaxation peak but also increases the low-frequency part of the relaxation susceptibility. It was shown that the ion-induced increase in the gigahertz elastic modulus can be described by changes in the relaxational susceptibility without a noticeable change in the instantaneous elastic modulus. The isotropic Raman contribution associated with the tetrahedral-like environment of H2O molecule does not correlate with Jones-Dole's B-coefficient, suggesting a minor influence of these tetrahedral-like configurations on viscosity.

Here, we examined the gigahertz sound velocities of hydrated multibilayers of saturated (1,2-dimyristoyl-sn-glycero-3-phosphocholine, DMPC) and unsaturated (1,2-dioleoyl-sn-glycero-3-phosphocholine, DOPC) phospholipids by Brillouin spectroscopy. Out-of-plane and in-plane (lateral) phonons were studied independently of each other. Similar strong temperature dependences of the sound velocities were found for phonons of both types. The sound velocities in the low-temperature limit were two-fold higher than that at physiological temperatures; a significant part of the changes in sound velocity occurs in the solid-like gel phase. The factors that may be involved in the peculiar behavior of sound velocity include changes in the chain conformational state, relaxation susceptibility, changes in the elastic modulus at infinite frequencies, and lateral packing of molecules.

The Large Volume Detector (LVD), located in the low-background laboratory of Gran Sasso, Italy, was designed to detect neutrinos from stellar core collapses in our Galaxy. The search for rare events requires careful attention to the experiment’s background, such as the natural radioactivity of rocks and detector materials, as well as the interaction of underground cosmic-ray muons. The LVD setup is capable of detecting gamma quanta from the decay of radon daughter nuclei. We convincingly demonstrate a correlation between the variation in the count rate of background pulses from gamma quanta in the detector and the variation in the concentration of radon nuclei in the experimental hall. We also point out the existence of another source of radon concentration variation — seismic activity.

Time series of gamma-ray photons from natural radioactivity measured with the Large Volume Detector (LVD) at the Gran Sasso underground laboratory (Laboratori Nazionali del Gran Sasso, Italy) have been analyzed. The instrument is used to detect neutrinos from gravitational collapses of stellar cores in the Galaxy. The background of the experiment is due to neutrons and gamma-ray photons from the decays of daughter nuclei of uranium and thorium. An analysis of periodic variations of the number of gamma-ray photons caused by the radon concentration in the underground laboratory has shown the presence of diurnal, weekly, monthly, and annual modulations. Data collected from 2004 to 2021, including a period of low activity in the hall of the Gran Sasso laboratory during the COVID-19 pandemic, have been reported.

According to the Large Volume Detector (LVD), located in the underground laboratory of Gran Sasso, Italy, a modulation of the concentration of the radioactive gas radon from the natural radioactivity of the rock, associated with lunar-monthly cycles, was detected. The rising phase falls on the days of the full moon. The amplitude of variations varies from 0.5 to 0.8 % .

The LVD detector, located in the Gran Sasso Laboratory at a depth of 3600 m w.e., is designed for research in the field of neutrino physics, astrophysics, cosmic ray physics and the search for rare processes predicted by theory. The LVD experiment was built in 1991 to detect neutrinos from collapses of stellar nuclei in our galaxy. The background of the detector is atmospheric muons, neutrons generated by muons in the detector material and natural radioactivity underground. The report presents the latest experimental results obtained at LVD: a limit on the frequency of supernova outbreaks, muon variations with a period of 1, 4, 10 years, and also describes the problems of studying the low-energy background underground.

The LVD experiment, located in a low-background Laboratory of the Gran Sasso, is designed to search for supernovae neutrinos burst and for studying cosmic ray muons. As part of the studies of variations of atmospheric muons underground, we analyzed the obtained energy calibrations of the LVD counters in the energy range of 50−450 MeV. Energy calibration of 840 LVD counters is carried out monthly through muons passing through the detector. The procedure consists in obtaining the muon spectrum average in the form using the ADC linear channels and then in the approximation of the spectrum of each counter to determine the channel number corresponding to the muon peak. We show a seasonal change in the position (channel) of the “muon peak” used for calibration.

We propose a new method for studying the elastic properties of biorelevant films, based on studying the deformation of an object under the action of a steel ball placed in a magnetic field and used as an indenter. Varying the distance between the magnet and the steel ball makes it possible to change the magnitude of the applied force in a wide range, which opens up the great potential of the proposed method for studying a wide class of biologically significant objects. The possibilities of this method are demonstrated by the example of determining the Young’s modulus of gelatin-based hydrogel films of various stiffness.

Cosmic radiation is a potential additional tool for atmospheric monitoring. High-energy cosmic rays, interacting in the atmosphere, produce secondary particles, the production and propagation of which are ruled by the state of the atmosphere. Atmospheric muons carry information on the stratosphere, as its temperature modulates their intensity. Here, we present a comprehensive investigation of the 24-year series of the muon flux recorded underground with the Large Volume Detector in the Gran Sasso Laboratory in Italy. Using advanced spectral-analysis methods, we reveal, in addition to the well-known annual cycle, two significant variations with periods of about four and ten years. These two multiannual components, however, are not present in the series of the so-called effective temperature---an average parameter commonly used to describe the entire atmospheric profile in relationship to the detected muon flux---but we find them in the series of the raw temperatures in the lower-stratospheric levels. We show that the weaker multiannual cycles emerge in the temperature series thanks to the dampening of the dominant annual radiative cycle at these levels, which are affected by higher-frequency variability related to transport and wave processes. We also show that the multiannual variations are not typical only of the Gran Sasso area but are present at large scales throughout the Northern Hemisphere. The analysis of the series of the muon flux also reveals evidence of daily to monthly scale variations, especially during the highly variable winter period. Although such short-term modulations are also found in the series of the effective temperature, we show that the variations of the two series are brought to better agreement when considering only specific layers of the atmosphere depending on the event. The amplitudes of the multiannual variations are significantly larger than those expected based on the temperature modulations. Such differences may be due to acknowledged difficulties of the adopted temperature reanalysis dataset to thoroughly represent long-term variability scales, so that long-term modulations in the raw temperature series and, consequently, in the effective temperature record would result as artificially attenuated. The muon flux therefore may be envisaged as a high time-resolution integrated proxy of lower-stratospheric temperatures.