Studies of the Angular Structure of Scintillating Radio Sources at 111 MHz

The angular sizes and compactnesses of 53 scintillating radio sources observed at 111 MHz on the Large Phased Array of the Lebedev Physical Institute are estimated. The parameters of the angular structures of the sources are estimated using a new method based on a joint analysis of the scintillation index and the asymmetry coefficient for the statistical distribution of the intensity fluctuations. The asymmetry coefficient for scintillations of a point source is estimated based on an analysis of observational data for turbulence in the solar wind. Different methods for estimating source angular sizes based on observations of interplanetary scintillations are compared. It is shown that the proposed new method is suitable for sources with angular sizes up to 1″. The accuracy of the estimated angular sizes and compactnesses of the sources is about 40%.

     

WASP-121b Secondary Eclipses Revisited Using TESS Observation

Astronomy Reports - We present the detection and characterization of the ultrahot Jupiter WASP-121b ( $${{R}_{p}} \simeq 1.865{\kern 1pt} {{R}_{J}}$$ , $${{M}_{p}} \simeq 1.184{\kern 1pt}...     

Impact of land use change on groundwater quality in a typical karst watershed of southwest China: a case study of the Xiaojiang watershed,Yunnan Province

The impact of land-use change on the quality of groundwater in the Xiaotjiang watershed, China was assessed for the period 1982–2004. Groundwater samples were collected from 30 monitoring points across the watershed, and were representative of the various changes, determined by remote sensing and geographical information systems. The results indicate that 610 km² (60% of the total watershed area) were subject to land-use change during the period. The most important changes were the conversion of 135 km² of forested land to cultivated land, and 211 km² of unused land to cultivated land. The main impact was ascribed to diffuse pollution from fertilizers applied to newly cultivated land, and from building development. Overall the groundwater pH value was significantly increased, as were the concentrations of ions , , , , and Cl⁻ in groundwater whilst the concentrations of Ca²⁺ and declined. More precisely, in the regions where forested land and unused land were converted into cultivated land, the pH value and the concentrations of Mg²⁺, , , , , Cl⁻ increased whilst the concentrations of Ca²⁺ and declined. However in the region where cultivated land was converted into construction land, the pH value and the concentrations of Ca²⁺, Mg²⁺, , , , , , Cl⁻ increased.

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Résumé  L’impact des changements de l’utilisation du territoire sur la qualité de l’eau souterraine dans le bassin versant de Xiaojiang, en Chine, a été évalué de 1982 à 2004. Des échantillons d’eau souterraine ont été récoltés à partir de 30 points d’observation éparpillés sur le bassin, représentant les divers changements déterminés par télédétection et système d’information géographique. Les résultats indiquent que 610 km² (soit 60% de la surface du bassin) ont été sujets à des modifications de l’utilisation du territoire sur cette période. Les changements les plus importants furent la conversion de 135 km² de forêt et 211 km² de terres inutilisées en terres cultivées. Le principal impact est attribué à la pollution diffuse des engrais utilisés en agriculture et pour les batiments. De manière générale le pH de l’eau souterraine a augmenté significativement, ainsi que les concentrations des ions , , , , et Cl⁻, tandis que les concentration en Ca²⁺ et ont diminué. Plus précisément dans les régions transformées en terres cultivées, la valeur du pH et les concentrations en Mg²⁺, , , , , Cl⁻ ont augmenté tandis que les concentrations en Ca²⁺ et ont diminué. Toutefois dans les régions cultivées converties en zones de construction, le pH et les concentrations en Ca²⁺, Mg²⁺, , , , , , Cl⁻ ont augmenté.

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Resumen  El impacto del cambio en uso de la tierra en la calidad del agua en la cuenca Xiaojiang, China fue evaluado para el periodo 1982–2004. Muestras de agua subterránea fueron tomadas de 30 puntos de monitoreo a través de la cuenca, y fueron representativas de los múltiples cambios, determinados por sensores remotos y sistemas de información geográfica. Los resultados indican que 610 km² (60% del área total de la cuenca) estaban sujetos a cambios de uso de la tierra durante el periodo estudiado. Los cambios más importantes fueron la conversión de 135 km² de bosques a tierra cultivada, y 211 km² de tierra sin uso (ociosa) a tierra cultivada. El impacto principal fue causado por contaminación difusa de fertilizantes aplicados a la tierra recientemente cultivada, y a desarrollo de construcciones. En general el pH en agua subterránea creció significantemente, al igual que las concentraciones de los iones , , , , y Cl⁻ en agua subterránea mientras que las concentraciones de Ca²⁺ y decrecieron. Mas precisamente, en las regiones donde bosque y tierra ociosa fueron convertidas en tierra cultivada, el valor de pH y las concentraciones de Mg²⁺, , , , , Cl⁻ crecieron mientras las concentraciones de Ca²⁺ y decrecieron. Sin embargo en la región donde tierra cultivada fue convertida en construcciones, el valor de pH y las concentraciones de Ca²⁺, Mg²⁺, , , , , , Cl⁻ crecieron.

     

Young Stellar Complexes in the Giant Galaxy UGC 11973

We present results of the analysis of photometric and spectroscopic observations of the young stellar complexes in the late giant spiral galaxy UGC 11973. Photometric analysis in the $$UBVRI$$ bands have been carried out for the 13 largest complexes. For one of them, metallicity of the surrounding gas $$Z = 0.013 \pm 0.005$$ , the mass $$M = (4.6 \pm 1.6) \times {{10}^{6}}{\kern 1pt} {{M}_{ \odot }}$$ , and the age of the stellar complex $$t = (2.0 \pm 1.1) \times {{10}^{6}}$$ yr were evaluated, using spectroscopic data. It is shown that all complexes are massive ( $$M \geqslant 1.7 \times {{10}^{5}}{\kern 1pt} {{M}_{ \odot }}$$ ) stellar groups younger than $$3 \times {{10}^{8}}$$ yr.     

Genesis of secondary uranium minerals associated with jasperoid veins,El Erediya area,Eastern Desert,Egypt

Uranium mineralization in the El Erediya area, Egyptian Eastern Desert, has been affected by both high temperature and low temperature fluids. Mineralization is structurally controlled and is associated with jasperoid veins that are hosted by a granitic pluton. This granite exhibits extensive alteration, including silicification, argillization, sericitization, chloritization, carbonatization, and hematization. The primary uranium mineral is pitchblende, whereas uranpyrochlore, uranophane, kasolite, and an unidentified hydrated uranium niobate mineral are the most abundant secondary uranium minerals. Uranpyrochlore and the unidentified hydrated uranium niobate mineral are interpreted as alteration products of petscheckite. The chemical formula of the uranpyrochlore based upon the Electron Probe Micro Analyzer (EPMA) is . It is characterized by a relatively high Zr content (average ZrO₂ = 6.6 wt%). The average composition of the unidentified hydrated uranium niobate mineral is , where U and Nb represent the dominant cations in the U and Nb site, respectively. Uranophane is the dominant U⁶⁺ silicate phase in oxidized zones of the jasperoid veins. Kasolite is less abundant than uranophane and contains major U, Pb, and Si but only minor Ca, Fe, P, and Zr. A two-stage metallogenetic model is proposed for the alteration processes and uranium mineralization at El Erediya. The primary uranium minerals were formed during the first stage of the hydrothermal activity that formed jasperoid veins in El Eradiya granite (130–160 Ma). This stage is related to the Late Jurassic–Early Cretaceous phase of the final Pan-African tectono-thermal event in Egypt. After initial formation of El Erediya jasperoid veins, a late stage of hydrothermal alteration includes argillization, dissolution of iron-bearing sulfide minerals, formation of iron-oxy hydroxides, and corrosion of primary uranium minerals, resulting in enrichment of U, Ca, Pb, Zr, and Si. During this stage, petscheckite was altered to uranpyrochlore and oxy-petscheckite. Uranium was likely transported as uranyl carbonate and uranyl fluoride complexes. With change of temperature and pH, these complexes became unstable and combined with silica, calcium, and lead to form uranophane and kasolite. Finally, at a later stage of low-temperature supergene alteration, oxy-petscheckite was altered to an unidentified hydrated uranium niobate mineral by removal of Fe.     

Study of compact radio sources using interplanetary scintillations at 111 MHz. The Pearson-Readhead sample

A complete sample of radio sources has been studied using the interplanetary scintillation method. In total, 32 sources were observed, with scintillations detected in 12 of them. The remaining sources have upper limits for the flux densities of their compact components. Integrated flux densities are estimated for 18 sources.     

Stable isotope study of the mineralization and alteration in the Madjarovo Pb–Zn district,south-east Bulgaria

The Madjarovo ore district is centred on the exposed section of a Lower Oligocene volcano and consists of radially disposed Pb–Zn-precious metal veins and attendant intermediate sulfidation wallrock alteration. Earlier high sulfidation and potassic porphyry style alterations are found in the centre of the district spatially associated with monzonitic intrusions. The total duration of all mineralization and alteration was ca. 300 ka. Stable isotope analyses (S, O, H) have been carried out on a suite of sulfides, sulfates and silicates from the mineralization, high and intermediate sulfidation alterations and a suite of basement rocks. These data range between the following limits: . We also analysed δD of fluid inclusions in quartz and barite for which we obtained, respectively, the ranges of −43.6 to −78.6 and −58.4 to −67.1‰. The data show that high sulfidation alteration was dominated by magmatic fluids with minor meteoric water, whereas the fluids responsible for the intermediate sulfidation alteration were essentially magmatic. The fluids responsible for the intermediate sulfidation Pb–Zn mineralization were mixed magmatic–meteoric and certainly contained a significant meteoric component. Sulphur is likely derived from basement and/or igneous sources. The evolution of alteration and mineralization styles from potassic, porphyry copper style to high sulfidation to intermediate sulfidation can be understood in terms of changing ore fluid composition resulting from an increasing permeability of the system and an increasingly remote source of magmatic fluid with time. These changes link directly to the geological evolution of this volcanic centre.     

Thermodynamic Properties of Brucite Determined by Solubility Studies and Their Significance to Nuclear Waste Isolation

Solubility experiments were conducted for the dissolution reaction of brucite, Mg(OH)₂ (cr): Experiments were conducted from undersaturation in deionized (DI) water and 0.010–4.4 m NaCl solutions at 22.5°C. In addition, brucite solubility was measured from supersaturation in an experiment in which brucite was precipitated via dropwise addition of 0.10 m NaOH into a 0.10 m MgCl₂ solution also at 22.5°C. The attainment of the reversal in equilibrium was demonstrated in this study. The solubility constant at 22.5°C at infinite dilution calculated from the experimental results from the direction of supersaturation by using the specific interaction theory (SIT) is: with a corresponding value of 17.0 ± 0.2 (2σ) when extrapolated to 25°C. The dimensionless standard chemical potential (μ°/RT) of brucite derived from the solubility data in 0.010 m to 4.4 m NaCl solutions from undersaturation extrapolated to 25°C is −335.76 ± 0.45 (2σ), with the corresponding Gibbs free energy of formation of brucite, , being −832.3 ± 1.1 (2σ) kJ mol⁻¹. In combination with the auxiliary thermodynamic data, the is calculated to be 17.1 ± 0.2 (2σ), based on the above Gibbs free energy of formation for brucite. This study recommends an average value of 17.05 ± 0.2 in logarithmic unit as solubility constant of brucite at 25°C, according to the values from both supersaturation and undersaturation. Sandia National Laboratories is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under Contract DE-AC04-94AL85000.     

The concept of geochemical potential field exemplified by ore formation field

Geochemical potential field is defined as the scope within the earth’s space where a given component in a certain phase of a certain material system is acted upon by a diffusion force, depending on its spatial coordinatesX, Y andZ. The three coordinates follow the relations: $$NF_{ix} = - \frac{{\partial \mu }}{{\partial x}}, NF_{iy} = - \frac{{\partial \mu }}{{\partial y}}, NF_{iz} = - \frac{{\partial \mu }}{{\partial z}}$$ The characteristics of such a field can be summarized as: (1) The summation of geochemical potentials related to the coordinatesX, Y, Z, or pseudo-velocity head, pseudo-pressure head and pseudo-potential head of a certain component in the earth is a constant as given by $$\mu _x + \mu _y + \mu _z = c$$ or $$\mu _{x2} + \mu _{y2} + \mu _{z2} = \mu _{x1} + \mu _{y1} + \mu _{z1} $$ Derived from these relations is the principle of geochemical potential conservation. The following relations have the same physical significance: $$\mu _k + \mu _u + \mu _p = c$$ or $$\mu _{k2} + \mu _{u2} + \mu _{p2} = \mu _{k1} + \mu _{u1} + \mu _{p1} $$ (2) Geochemical potential field is a vector field quantified by geochemical field intensity which is defined as the diffusion force applied to one molecular volume (or one atomic volume) of a certain component moving from its higher concentration phase to lower concentration phase. The geochemical potential field intensity is given by $$\begin{gathered} E = - grad\mu \hfill \\ E = \frac{{RT}}{x}i + \frac{{RT}}{y}j + \frac{{RT}}{z}K \hfill \\ \end{gathered} $$ The present theory has been inferred to interpret the mechanism of formation of some tungsten ore deposits in China.     

Norm of the Position Shift of a Celestial Body in a Dynamical Astronomy Problem

The averaging method is widely used in celestial mechanics, in which a mean orbit is introduced and slightly deviates from an osculating one, as long as disturbing forces are small. The difference $$\delta {\mathbf{r}}$$ in the celestial body positions in the mean and osculating orbits is a quasi-periodic function of time. Estimating the norm $$\left\| {\delta {\mathbf{r}}} \right\|$$ for deviation is interesting to note. Earlier, the exact expression of the mean-square norm for one problem of celestial mechanics was obtained: a zero-mass point moves under the gravitation of a central body and a small perturbing acceleration $${\mathbf{F}}$$. The vector $${\mathbf{F}}$$ is taken to be constant in a co-moving coordinate system with axes directed along the radius vector, the transversal, and the angular momentum vector. Here, we solved a similar problem, assuming the vector $${\mathbf{F}}$$ to be constant in the reference frame with axes directed along the tangent, the principal normal, and the angular momentum vector. It turned out that $${{\left\| {\delta {\mathbf{r}}} \right\|}^{2}}$$ is proportional to $${{a}^{6}}$$, where $$a$$ is the semi-major axis. The value $${{\left\| {\delta {\mathbf{r}}} \right\|}^{2}}{{a}^{{ - 6}}}$$ is the weighted sum of the component squares of $${\mathbf{F}}$$. The quadratic form coefficients depend only on the eccentricity and are represented by the Maclaurin series in even powers of $$e$$ that converge, at least for $$e < 1$$. The series coefficients are calculated up to $${{e}^{4}}$$ inclusive, so that the correction terms are of order $${{e}^{6}}$$.     

Eclipsing System PS UMa: Evolutionary Status and Physical Parameters of the Components

We present the first high accuracy UBVRI(RI)c CCD light curves of the newly discovered eclipsing system PS UMa = GSC 4375 1733 ($$P = 9_{·}^{d}27$$, $$V = 12_{·}^{m}42$$). The photometric solutions are found, the physical parameters of the components are derived. The eccentricity of the orbit was found to be negligible e = 0.074, which made it difficult to measure the rate of the apsidal rotation. High accuracy of our observations allowed us to find the reliable parameters of the system. Components (Sp = F7 + G1) have advanced significantly in their evolution, the age of the system is 2.4 billion years. The mass and the radius of G1 component is larger and it is ahead of the F7 component in its evolution. The model of the system best suits the theory in the absence of the overshooting in the core. Obtained from our observations photometrical parallax π = 0$$_{.}^{\prime\prime }$$00102(2) coincides with GAIA DR2 value $$\pi =0_{·}^{\prime\prime }00106(3)$$ within their errors. The new EW type variable with period $$ \approx {\kern 1pt} 0_{·}^{d}40$$ was found in the field of PS UMa.     

Galaxies with Abnormally High Gas Content in the Disk

Astronomy Reports - The content of gas in galaxies with an anomalously high relative mass of hydrogen $${{M}_{{{\text{HI}}}}}{\text{/}}{{M}_{*}}$$ for a given mass of the stellar population...     

Measurement of the turbulence in the free atmosphere above Mt. Ma\overset{\lower0.5em\hbox{danak

Stellar scintillations were measured at Mt. Ma $\overset{\lower0.5em\hbox{$\overset{\lower0.5em\hbox{ danak during 42 nights in 1998–1999 in order to estimate the contribution of the free atmosphere to the seeing. The atmosphere above 1–2 km provides a median seeing of _boxclose_boxclose 390\mathop .\limits^{'} 39 , which is about one-third of the total seeing ( 0\mathop .^" 700\mathop .\limits^{'} 70 ). The characteristic altitudes of turbulent layers are from 3 to 11 km above the summit, and the appearance of layers at altitudes of 3–4 km is accompanied by a degradation of the free-atmosphere seeing. The median isoplanatic angle is q₀ = 2\mathop .^" 30\theta _0 = 2\mathop .\limits^{'} 30 (λ=500 nm, at the zenith). This is the first time that such data have been obtained for Ma $\overset{\lower0.5em\hbox{$\overset{\lower0.5em\hbox{ danak. The instruments used for these measurements—a modified four-channel photometer and a prototype of a double-aperture scintillation sensor—are described in detail. The data reduction was based on accurate corrections for photon-counting statistics and the use of theoretical weighting functions relating scintillation indices to the altitudes and intensities of turbulent layers. Simultaneous or quasi-simultaneous measurements of scintillation indices using apertures of different sizes having significantly different weighting functions enable estimation of the altitude and intensity of the equivalent turbulent layer. Despite the simplicity of this one-layer model, it provides fairly robust estimates of the integrated parameters of the real free atmosphere.     

Oxygen isotope fractionation between rutile and water

Synthetic rutile-water fractionations (1000 ln α) at 775, 675, and 575° C were found to be ?2.8, ?3.5, and ?4.8, respectively. Partial exchange experiments with natural rutile at 575° C and with synthetic rutile at 475° C failed to yield reliable fractionations. Isotopic fractionation within the range 575–775° C may be expressed as follows: 1 $$1000\ln \alpha ({\rm T}i{\rm O}_{2 } - H_2 O) = - 4.1 \frac{{10^6 }}{{T_{k^2 } }} + 0.96$$ . Combined with previously determined quartz-water fractionations, the above data permit calibration of the quartz-rutile geothermometer: 1 $$1000\ln \alpha ({\text{S}}i{\rm O}_{2 } - Ti{\rm O}_{2 } ) = 6.6 \frac{{10^6 }}{{T_{k^2 } }} - 2.9$$ . When applied to B-type eclogites from Europe, as an example, the latter equation yields a mean equilibration temperature of 565° C.     

Influence of hydrogen on Fe–Mg interdiffusion in (Mg,Fe)O and implications for Earth’s lower mantle

Interdiffusion of Fe and Mg in (Mg,Fe)O has been investigated experimentally under hydrous conditions. Single crystals of MgO in contact with (Mg_0.73Fe_0.27)O were annealed hydrothermally at 300 MPa between 1,000 and 1,250°C and using a Ni–NiO buffer. After electron microprobe analyses, the dependence of the interdiffusivity on Fe concentration was determined using a Boltzmann–Matano analysis. For a water fugacity of ∼300 MPa, the Fe–Mg interdiffusion coefficient in Fe _x Mg_1−x O with 0.01 ≤ x ≤ 0.25 can be described by with and C = −80 ± 10 kJ mol⁻¹. For x = 0.1 and at 1,000°C, Fe–Mg interdiffusion is a factor of ∼4 faster under hydrous than under anhydrous conditions. This enhanced rate of interdiffusion is attributed to an increased concentration of metal vacancies resulting from the incorporation of hydrogen. Such water-induced enhancement of kinetics may have important implications for the rheological properties of the lower mantle.

Monitoring of the turbulent solar wind with the upgraded Large Phased Array of the Lebedev Institute of Physics: First results

The design properties and technical characteristics of the upgraded Large Phased Array (LPA) are briefly described. The results of an annual cycle of observations of interplanetary scintillations of radio sources on the LPA with the new 96-beam BEAM 3 system are presented. Within a day, about 5000 radio sources displaying second-timescale fluctuations in their flux densities due to interplanetary scintillations were observed. At present, the parameters of many of these radio sources are unknown. Therefore, the number of sources with root-mean-square flux-density fluctuations greater than 0.2 Jy in a 3° × 3° area of sky was used to characterize the scintillation level. The observational data obtained during the period of the maximum of solar cycle 24 can be interpreted using a three-component model for the spatial structure of the solar wind, consisting of a stable global component, propagating disturbances, and corotating structures. The global component corresponds to the spherically symmetric structure of the distribution of the turbulent interplanetary plasma. Disturbances propagating from the Sun are observed against the background of the global structure. Propagating disturbances recorded at heliocentric distances of 0.4–1 AU and at all heliolatitudes reach the Earth’s orbit one to two days after the scintillation enhancement. Enhancements of ionospheric scintillations are observed during night-time. Corotating disturbances have a recurrence period of 27^d. Disturbances of the ionosphere are observed as the coronal base of a corotating structure approaches the western edge of the solar limb.     

The Equation of State for Caspian Sea Waters

The density ρ of Caspian Sea waters was measured as a function of temperature (273.15–343.15) K at conductivity salinities of 7.8 and 11.3 using the Anton-Paar Densitometer. Measurements were also made on one of the samples (S = 11.38) diluted with water as a function of temperature (T = 273.15–338.15 K) and salinity (2.5–11.3). These latter results have been used to develop an equation of state for the Caspian Sea (σ = ±0.007 kg m⁻³)

Mechanisms of hydrogen incorporation and diffusion in iron-bearing olivine

The incorporation and diffusion of hydrogen in San Carlos olivine (Fo₉₀) single crystals were studied by performing experiments under hydrothermal conditions. The experiments were carried out either at 1.5 GPa, 1,000°C for 1.5 h in a piston cylinder apparatus or at 0.2 GPa, 900°C for 1 or 20 h in a cold-seal vessel. The oxygen fugacity was buffered using Ni–NiO, and the silica activity was buffered by adding San Carlos orthopyroxene powders. Polarized Fourier transform infrared (FTIR) spectroscopy was utilized to quantify the hydroxyl distributions in the samples after the experiments. The resulting infrared spectra reproduce the features of FTIR spectra that are observed in olivine from common mantle peridotite xenoliths. The hydrogen concentration at the edges of the hydrogenated olivine crystals corresponds to concentration levels calculated from published water solubility laws. Hydrogen diffusivities were determined for the three crystallographic axes from profiles of water content as a function of position. The chemical diffusion coefficients are comparable to those previously reported for natural iron-bearing olivine. At high temperature, hydrogenation is dominated by coupled diffusion of protons and octahedrally coordinated metal vacancies where the vacancy diffusion rate limits the process. From the experimental data, we determined the following diffusion laws (diffusivity in m² s⁻¹, activation energies in kJ mol⁻¹): for diffusion along [100] and [010]; for diffusion along [001]. These diffusion rates are fast enough to modify significantly water contents within olivine grains in xenoliths ascending from the mantle.     

Opening and resetting temperatures in heating geochronological systems

We present a theoretical model for diffusive daughter isotope loss in radiochronological systems with increasing temperature. It complements previous thermochronological models, which focused on cooling, and allows for testing opening and resetting of radiochronometers during heating. The opening and resetting temperatures are, respectively,

Principle of Formation of the Earth’s Crust under Natural Stress Conditions

This article formulates the experimentally substantiated physical principle that the natural stress condition of the Earth’s crust is formed due to the superposition of stress fields, which is caused by the gravitational forces of the Earth and by tectonic and astrophysical forces that are produced by physical processes in space. The natural stress field is represented by the stress tensor regulatory components: \(\sigma _{z}^{{\text{N}}}\) = \( - \gamma H + {{\sigma }_{{zT}}} + {{\sigma }_{{z{\text{AF}}}}}\), \(\sigma _{x}^{{\text{N}}}\) = \( - \lambda \gamma H + {{\sigma }_{{xT}}} + {{\sigma }_{{x{\text{AF}}}}}\), \(\sigma _{y}^{{\text{N}}}\) = \( - \lambda \gamma H + {{\sigma }_{{yT}}} + {{\sigma }_{{y{\text{AF}}}}}\).