Radial pulsations of helium stars with masses from 10 to 50<Emphasis Type="Italic">M</Emphasis><Subscript>⊙</Subscript>

We have performed hydrodynamic calculations of the radial pulsations of helium stars with masses 10M_⊙ ≤ M ≤ 50M_⊙, luminosity-to-mass ratios 5 × 10³L_⊙/M_⊙ ≤ L/M ≤ 2.5 × 10⁴L_⊙/M_⊙, and effective temperatures 2 × 10⁴ K ≤ T_eff ≤ 10⁵ K for helium and heavy-element mass fractions of Y=0.98 and Z=0.02, respectively. We show that the high-temperature boundary of the instability region for radial pulsations at L/M ? 10⁴L_⊙/M_⊙ extends to T_eff≈10⁵ K. The amplitude of the velocity variations for outer layers is several hundred km s^?1, while the brightness variations in the B band of the UBV photometric system are within the range from several hundredths to half a magnitude. At constant luminosity-to-mass ratio, the radial pulsation period is determined only by the effective temperature of the star. In the ranges of luminosity-to-mass ratios 10⁴L_⊙/M_⊙ ≤ L/M ≤ 2 × 10⁴L_⊙/M_⊙ and effective temperatures 5 × 10⁴ K ≤ T_eff ≤ 9 × 10⁴ K, the periods of the radial modes are within 6 min ?Π?10³ min.     

Hydraulic Crack Growth Dynamics from Ultrasound Transmission Monitoring in Laboratory Experiments

Izvestiya, Physics of the Solid Earth - Abstract—Acoustic transmission data obtained in the laboratory experiment are used to identify stages of hydraulic fracture initiation, growth, and...     

Experimental evidence for flexibility of a building foundation supported by concrete friction piles

This article explores the possibility to measure deformations of building foundations from measurements of ambient noise and strong motion recordings. The case under study is a seven-storey hotel building in Van Nuys, California. It has been instrumented by strong motion accelerographs, and has recorded several earthquakes, including the 1971 San Fernando (M_L=6.6, R=22 km), 1987 Whittier–Narrows (M_L=5.9, R=41 km), 1992 Landers (M_L=7.5, R=186 km), 1992 Big Bear (M_L=6.5, R=149 km), and 1994 Northridge (M_L=6.4, R=1.5 km) earthquake and its aftershocks (20 March: M_L=5.2, R=1.2 km; 6 December, 1994: M_L=4.3, R=11 km). It suffered minor structural damage in 1971 earthquake and extensive damage in 1994. Two detailed ambient vibration tests were performed following the Northridge earthquake, one before and the other one after the 20 March aftershock. These included measurements at a grid of points on the ground floor and in the parking lot surrounding the building, presented and analyzed in this article. The analysis shows that the foundation system, consisting of grade beams on friction piles, does not act as a “rigid body” but deforms during the passage of microtremor and therefore earthquake waves. For this geometrically and by design essentially symmetric building, the center of stiffness of the foundation system appears to have large eccentricity (this is seen both from the microtremor measurements and from the earthquake recordings). This eccentricity may have contributed to strong coupling of transverse and torsional responses, and to larger than expected torsional response, contributing to damage during the 1994 Northridge, earthquake.     

Estimating the validity of the recognition results of earthquake-prone areas using the ArcMap

In 1972, V. Keilis-Borok and I. Gelfand introduced the phenomenological approach based on the morphostructural zoning and pattern recognition for identification of earthquake-prone areas. This methodology identifies seismogenic nodes capable of generating strong earthquakes on the basis of geological, morphological, and geophysical data, which do not contain information on past seismicity. In the period 1972–2018, totally, 26 worldwide seismic regions have been studied and maps showing the recognized earthquake-prone areas in each region have been published. After that, 11 of these regions were hit by earthquakes of the relevant sizes. The goal of this work is to analyze the correlation of the post-publication events with seismogenic nodes defined in these 11 regions. The test was performed using the NEIC earthquake catalog because it uniformly defines the location and magnitudes of earthquakes over the globe. The ArcMap facilities were exploited to plot the post-publication events on the maps showing the recognized seismogenic nodes. We found that about 86% of such events fall in the recognized seismogenic nodes. The performed test proved the sufficient validity of the methodology for identifying areas capable of strong earthquakes and confirms the idea on nucleating strong earthquakes at the nodes.     

Planetary protection principles used for Phobos-Grunt mission

The article presents an analysis of the Phobos-Grunt mission, a classification of its phases in terms of planetary protection, and the main principles of activities management and definition of actions for fulfilling the planetary-protection requirements developed by Committee on Space Research.     

“In situ” visualization of phase states and transformations of hydrocarbons in water-oil mixtures at high and ultrahigh temperatures and pressures

Doklady Earth Sciences -     

Lithology and facies of the Burtasian and Khvalynian sediments in Manych

Results of study od the lithofacies structure of the Burtasian and Khvalynian sediments in the Manych Depression are discussed. The sediments are similar in the grain size and mineral compositions. They are mainly represented by clayey silt, as well as silty and sandy-silty clay with subangular fragments of crystalloclasts and lithoclasts. They are characterized by a low content of heavy fraction dominated by transparent minerals (apatite, garnet, biotite, chlorite, hornblende, and others). Ore minerals (limonite and magnetite) are subordinate. The Burtasian sediments are marked by thin-horizontal bedding. Bedding of the Khvalynian sediments is more diverse: horizontal, gentle-horizontal, and alternation with gentle crossbedded-diagonal (trough-like), crisscross-wavy, and other types of bedding. The lithological composition and fossil plant seeds found in the Burtasian and Khvalynian sediments make it possible to distinguish facies formed under calm (Burtasian) and calm flow (Khvalynian) hydrodynamic regimes of sedimentation in closed (lakes) and open (channels of the Khvalynian Strait) reservoirs.     

The Paleoproterozoic remagnetization trend in rocks of the Belomorian mobile belt: Paleomagnetic and geologic evidence

As a resulting of comprehensive studies of Paleoproterozoic igneous complexes a regular remagnetization trend is revealed. It is shown that the remagnetization front propagated from the northwest to southeast. The obtained remagnetization trend probably reflects the direction of the collision in the Paleoproterozoic. Correlation between remagnetization processes and rock compositions was found. The degree of conservation of secondary earlier and later magnetization components is likely associated to both the compositions of protoliths and different transformation conditions of rocks, including their fluid saturation.