Peierls–Nabarro modelling of dislocations in diopside

The core structures of dislocations in diopside have been calculated within the Peierls model, which assumes a planar core. 1/2<110> dislocations can dissociate into two collinear partial dislocations. We show that [001] glide is very difficult in (010) and that a non-collinear dissociation of [001](100) (modelled within a Peierls–Nabarro–Galerkin approach) makes glide equally easy in (100) and {110}. A widely spread core structure corresponding to a low lattice friction has been found for [100](010) and [010](100) dislocations which is not supported by mechanical data and, together with TEM observations, suggests that another, probably non-planar core structure is possible for these dislocations.     

Division of tectonic–strata superregions in China

The continent of China is grouped into Pan–Cathaysian blocks, Laurasia and Gondwana Continental margins and relics of three oceans-Paleoasian, Tethys, and Pacific as a whole. In detail, the continent of China grew up by coalescence of three blocks or platforms (North China, Tarim and Yangtze) and eight orogenic belts (Altay–Inner Mongolia–Daxinganling, Tianshan–Junggar–Beishan, Qinling–Qilian– Kunlun, Qiangtang–Sanjiang, Gangdisê, Himalaya, Cathaysia, Eastern Taiwan) during the processes of oceanic crust disappearance and acceretionary-collision of continental crusts. In the orogenic belts, six convergent crustal consumption zones (Ertix–Xar Moron, South Tianshan, Kuanping–Foziling, Bangong co–Shuanghu–Nujiang–Changning–Menglian, Yarlung–Tsangpo, Jiangshao–Chenzhou–Qinfang) have been distinguished. Correspondingly, the strata of the continent of China are subdivided into 17 tectonic-strata superregions, which tectonically belong to three blocks or platforms, six convergent crustal consumption zones and eight orogenic series, respectively. This division is based mainly on differences of tectonic environment and tectonic evolution among blocks, zones and belts, including the timing of when the oceanic crusts transferred into continental crusts, the paleobiogeographic features, and the types of strata.     

Catalogue of rogue waves reported in media in 2006–2010

The data of rogue wave accidents reported in mass media during 2006–2010 years are collected and analysed. The collection includes 106 events, which are classified by their validity as true (78) and possible (28) and by the location of their occurrence: we distinguish deep, shallow and coastal rogue waves, which occurred in deep/shallow waters or at the coast. The validity of the event has been estimated by the rogue wave height, which should be twice larger than the significant wave height (significant wave height has been taken from satellite data), and/or by the associated hazard. It is shown that rogue waves cause especially high damage in shallow waters and at the coast.     

Heavy metal contamination in the vicinity of the Daduk Au–Ag–Pb–Zn mine in Korea

The heavy metal contamination and seasonal variation of the metals in soils, plants and waters in the vicinity of an abandoned metalliferous mine in Korea were studied. Elevated levels of Cd, Cu, Pb and Zn were found in tailings with averages of 8.57, 481, 4,450 and 753 mg/kg, respectively. These metals are continuously dispersed downstream and downslope from the tailings by clastic movement through wind and water. Thus, significant levels of the elements in waters and sediments were found up to 3.3 km downstream from the mining site, especially for Cd and Zn. Enriched concentrations of heavy metals were also found in various plants grown in the vicinity of the mining area, and the metal concentrations in plants increased with those in soils. In a study of seasonal variation on the heavy metals in paddy fields, relatively high concentrations of heavy metals were found in rice leaves and stalks grown under oxidizing conditions rather than a reducing environment (P<0.05).     

Origin of epithermal Ag–Au–Cu–Pb–Zn mineralization in Guanajuato, Mexico

The Guanajuato epithermal district is one of the largest silver producers in Mexico. Mineralization occurs along three main vein systems trending dominantly northwest–southeast: the central Veta Madre, the La Luz system to the northwest, and the Sierra system to the east. Mineralization consists dominantly of silver sulfides and sulfosalts, base metal sulfides (mostly chalcopyrite, galena, sphalerite, and pyrite), and electrum. There is a broad zonation of metal distribution, with up to 10 % Cu+Pb+Zn in the deeper mines along the northern and central portions of the Veta Madre. Ore occurs in banded veins and breccias and as stockworks, with gangue composed dominantly of quartz and calcite. Host rocks are Mesozoic sedimentary and intrusive igneous rocks and Tertiary volcanic rocks. Most fluid inclusion homogenization temperatures are between 200 and 300 °C, with salinities below 4 wt.% NaCl equivalent. Fluid temperature and salinity decreased with time, from 290 to 240 °C and from 2.5 to 1.1 wt.% NaCl equivalent. Relatively constant fluid inclusion liquid-to-vapor ratios and a trend of decreasing salinity with decreasing temperature and with increasing time suggest dilution of the hydrothermal solutions. However, evidence of boiling (such as quartz and calcite textures and the presence of adularia) is noted along the Veta Madre, particularly at higher elevations. Fluid inclusion and mineralogical evidence for boiling of metal-bearing solutions is found in gold-rich portions of the eastern Sierra system; this part of the system is interpreted as the least eroded part of the district. Oxygen, carbon, and sulfur isotope analysis of host rocks, ore, and gangue minerals and fluid inclusion contents indicate a hydrothermal fluid, with an initial magmatic component that mixed over time with infiltrating meteoric water and underwent exchange with host rocks. Mineral deposition was a result of decreasing activities of sulfur and oxygen, decreasing temperature, increasing pH, and, in places, boiling.     

Preliminary Understanding of Ore Genesis of Zhaxikang Pb–Zn–Ag–Sb Deposit in the North Himalaya

Please?refer?to?the?attachment(s)?for?more?details.     

Application of the region–time–length algorithm to study of earthquake precursors in the Thailand–Laos–Myanmar borders

In order to examine the precursory seismic quiescence of upcoming hazardous earthquakes, the seismicity data available in the vicinity of the Thailand–Laos–Myanmar borders was analyzed using the Region–Time–Length (RTL) algorithm based statistical technique. The utilized earthquake data were obtained from the International Seismological Centre. Thereafter, the homogeneity and completeness of the catalogue were improved. After performing iterative tests with different values of the \(r_{0}\) and \(t_{0}\) parameters, those of \(r_{0}\) = 120 km and \(t_{0}\) = 2 yr yielded reasonable estimates of the anomalous RTL scores, in both temporal variation and spatial distribution, of a few years prior to five out of eight strong-to-major recognized earthquakes. Statistical evaluation of both the correlation coefficient and stochastic process for the RTL were checked and revealed that the RTL score obtained here excluded artificial or random phenomena. Therefore, the prospective earthquake sources mentioned here should be recognized and effective mitigation plans should be provided.     

The role of acidity–basicity in evaporating refractory inclusions in chondrites

When melts of Ca–Al inclusions in chondrites, which are dominated by the oxides SiO₂, MgO, CaO, and Al₂O₃, evaporate at high temperatures, the SiO₂ and MgO fugacities are inverted: SiO₂, which is more volatile than MgO, becomes less volatile when melts rich in refractory CaO and Al₂O₃ evaporate. This fugacity inversion can be realistically explained within the framework of D.S. Korzhinskii’s theory of acid–base interaction between components in silicate melts. According to this theory, an increase in CaO concentration in the melt increases its basicity, and this, in turn, increases the activity (and hence, also fugacity) of MgO and decreases those of SiO₂. In the real compositions of the Ca–Al inclusions in chondrites, the MgO/SiO₂ ratio systematically decreases with an increase in the CaO concentration under the effect of acid–base interaction.     

Evolution of radiolarians in the late Albian–Campanian

The dynamics of radiolarian evolution in the late Albian–Campanian is analyzed, and several stages are recognized. The first stage (late Albian–middle Cenomanian), related to the MCE regional anoxic event, showed low evolutionary tempos and hence lacked structural change in radiolarian communities. The second stage (late Cenomanian–early Turonian), corresponding to ОАЕ 2, which was a global anoxic event, is characterized by a decrease in the number of genera, while many genera showed increased diversification of species composition. At this stage, a considerable number of genera became extinct and appeared, suggesting an increased rate of the radiolarian evolution. The third stage (middle Turonian–early Coniacian), including the beginning of ОАЕ 3, is characterized by a stabilized number of genera. The fourth stage (late Coniacian–Santonian) completely encompasses ОАЕ 3 except for its very beginning. At this stage, the radiolarian communities underwent a significant structural change, while their rate of evolution increased considerably. Nevertheless, during the ОАЕ 3 stage, a distinct trend toward a decrease in generic diversity continued from the late Cenomanian to the middle Turonian. The fifth stage (Campanian) is characterized by quite significant changes in the assemblage composition, while the trend toward a gradual decrease in the number of genera steadily continued. At this stage, which coincided with a considerable cooling, twice as many genera became extinct as during ОАЕ 2. The analysis of the dynamics of radiolarian evolution showed that the anoxic MCE, ОАЕ 2, and ОАЕ 3 events did not result in degradation of radiolarian assemblages. This suggests that this group has significant stratigraphic potential. In general, the evolution of radiolarians in the Late Cretaceous was gradual. By the end of the Campanian, nearly half of the generic diversity was composed of genera which appeared at the beginning of the Cretaceous and earlier.     

Color variability of BL Lac in 2002–2008

An analysis of multicolor photometric observations of BL Lac performed at the Astronomical Institute of Saint Petersburg State University was carried out to determine the color characteristics of the variable sources responsible for the activity of this object. The existence of two variable synchrotron components has been established. One is responsible for small flux variations at low flux levels, and the second for outbursts. The outbursts are associated with the propagation of shocks in the jet.     

Assemblage of Fe–Mg–Al–Ti–Zn Oxides in Granulites of the Bunger Hills,East Antarctica: Evidence of Ultrahigh-Temperature Metamorphism

Geology of Ore Deposits - The composition and interrelations of oxides (minerals of the spinel supergroup, corundum, ilmenite, rutile) and silicates (garnet, sillimanite, orthopyroxene, cordierite)...     

Role of diffusion–precipitation reactions in authigenic pyritization

Models proposed for authigenic pyritization in the literature provide good indicators of the effect of very high concentrations of available iron on decaying organisms; however, the impact of lower concentrations of iron on an actively decaying system is not so well characterised. Gel-stabilised systems are used to model the effect of extremes of iron concentration on the precipitation of pyrite and the process of organic matter preservation. The experiments show the effect of sulphate reduction decay in an environment where iron is limited or dispersed, and in iron-rich environment where diffusion is limited. The formation of discrete sulphide bands in experiments where iron is limited indicates that negative feedback, or Liesegang, reactions play a role in the development of gaps between sites of organic matter preservation and pyrite precipitation, providing a mechanism for the formation of pyrite halos, concretion rims and overgrowths. In iron-rich environments, pyrite formation is confined to the decaying organism, and the Liesegang effect is limited due to the restricted diffusion of dissolved sulphide.     

Numerical analysis of seepage–deformation in unsaturated soils

A coupled elastic–plastic finite element analysis based on simplified consolidation theory for unsaturated soils is used to investigate the coupling processes of water infiltration and deformation. By introducing a reduced suction and an elastic–plastic constitutive equation for the soil skeleton, the simplified consolidation theory for unsaturated soils is incorporated into an in-house finite element code. Using the proposed numerical method, the generation of pore water pressure and development of deformation can be simulated under evaporation or rainfall infiltration conditions. Through a parametric study and comparison with the test results, the proposed method is found to describe well the characteristics during water evaporation/infiltration into unsaturated soils. Finally, an unsaturated soil slope with water infiltration is analyzed in detail to investigate the development of the displacement and generation of pore water pressure.     

Solid–water partitioning of elements in Czech freshwaters

Partitioning of 41 elements between solids and water was studied by filtration and dialysis in situ in Czech freshwaters. Field-based distribution (partition) coefficients, K_D, between suspended particulate matter (SPM) and filtrate (‘dissolved’ fraction) differed by 4 orders of magnitude. The highest K_D values (log K_D>2.0 l/g) were exhibited by Zr, Al, Ce, Pb, La, Ti, Fe, Sm, Th and Cr which are extremely insoluble in near-neutral water or generally poorly soluble (Zr,Ti). The K_Ds decrease with element and DOC loading due to the relative increase of the element in the low molecular fraction. Log K_D mostly increased linearly with pH within a range from 3.5 to 9. K_D^U decreased at pH >6 due to carbonate complexation. The colloidal fraction (>1 kDa <0.4 μm) in a reservoir with a pH of 6.8 was mainly preferred by Fe, Pb, Be, Nb, Y, Al, Ni, U and Zr. When the colloidal fraction is not differentiated from true solution, then incorrect information about partitioning may be obtained and the highest K_D may decrease.     

Multicolor photometry of CH Cygni in 1978–1998

We present the results of long-term (1978–1998) infrared and optical observations of the unique symbiotic system CH Cygni. The system’s IR brightness and color variations are generally consistent with a model in which the source is surrounded by a dust envelope with variable optical depth. There was evidence for a hot source in the CH Cyg system during the entire period from 1978 to 1998, with the exception of several hundred days in 1987–1989. Over the observation period, there was tendency for the system to gradually redden at 0.36–5 µm, accompanied by a brightness decrease at 0.36–2.2µm and a brightness increase at 3.5 and 5 µm. The “activation” of the cool sources in 1986–1989 nearly coincided with the disappearance of radiation from the hot source. The dust envelope of CH Cyg is not spherically symmetrical, and its optical depth along the line of sight is substantially lower than its emission coefficient, the mean values being τ_ex(L)～0.06 and τ_em(L)～0.16. We confirm the presence of a 1800-to 2000-day period in both the optical and IR, both accounting for, and not accounting for, a linear trend. The spectral type of the cool star varied between M5III and M7III. The spectral type was M5III during the phase of maximum activity of the system’s hot source, while the spectral type was M7III when the star’s optical radiation was almost completely absent. The luminosity of the cool giant varied from (6300–9100)L _⊙; its radius varied by approximately 30%. The ratio of the luminosities of the dust envelope and the cool giant varied from 0.08 to 0.5; i.e., up to 50% of the cool star’s radiation could be absorbed in the envelope. The temperature of dust particles in the emitting envelope varied from 550 to 750 K; the radius of the envelope varied by more than a factor of 2. The expansion of the emitting dust envelope observed in 1979–1988 accelerated: its initial velocity (in 1979) was ～8 km/s, while the maximum velocity (in 1987–1989) was ～180 km/s. Beginning in 1988, the radiation radius of the dust envelope began to decrease, first at ～45 km/s and then (in 1996–1998) at ～3 km/s. From 1979 until 1996, the mass of the emitting dust envelope increased by approximately a factor of 27 (the masses in 1979 and 1988 were ～1.4×10^?7 M _⊙ and ～3.8×10^?6 M _⊙, respectively), after which (by 1999) it decreased by nearly a factor of 7. The mass-loss rate of the cool star increased in 1979–1989, reaching ～3.5×10^?6 ～3.5×10^?6 M _⊙/yr in 1988. Subsequently (up to the summer of 1999), the envelope itself began to lose mass at a rate exceeding that of the cool star. The largest input of matter to the envelope occurred after the phase of optical activity in 1978–1985. If the envelope’s gas-to-dust ratio is ～100, the mass of matter ejected in 1988 was ～4×10^?4 M _⊙.     

Factors and Trends in the Formation of Natural–Technogenic Associations of Polycyclic Aromatic Hydrocarbons in the Snow–Soil System

Doklady Earth Sciences - The content of polycyclic aromatic hydrocarbons (PAHs) in soil and snow cover near the carbon black plants in Moscow, Omsk, and Samara regions was studied. The differences...     

Oxidative–reductive photodecomposition of perfluorooctanoic acid in water

This article aims to elucidate on usefulness of vacuum ultraviolet (VUV) for photoreductive degradation of perfluorooctanoic acid (PFOA), a representative perfluorinated compound (PFC), in water for the first time. Bench-scale tests were conducted on oxidative and reductive (with aquated electron: e _aq ^? ) mineralization of PFOA using low-pressure UV (LPUV) lamps and potassium iodide. Unlike with 254 nm wavelength (UVC), the reductive mineralization with VUV was very inefficient compared to the corresponding oxidative mineralization. The inefficiency is attributed to low reactivity of e _aq ^? with PFOA and its fluorinated products than that of 185 nm photons. Direct VUV photolysis of PFOA and its products in reductive reaction conditions was not apparent due to a very big difference in reactivity of 185 and 254 nm photons with iodide. The results demonstrated that highly energetic VUV photons are not suitable for photoreductive degradations of PFCs involving e _aq ^? , but they can be best used for oxidative degradations. These findings should serve as an important reference on VUV usage to decompose refractory micropollutants.     

Optical Monitoring of SS 433 in 2017–2021

Astronomy Reports - The observed characteristics of the spectral and photometric variability of SS 433 are discussed based on the data for 2018–2021 and compared with earlier results. The...     

A study of outburst activity of Z and in 2000–2010

We present the results of our study of the classical symbiotic star Z And during its period of activity in 2000–2010. In this period, the system experienced a series of six outbursts, for three of which high-resolution spectra were obtained and analyzed. These observations provided information about the system’s behavior during the entire activity period, rather than during an individual outburst. In particular, we found a fundamental difference between the first outburst, which initiated the activity period, and subsequent outbursts, namely, the presence of bipolar collimated optical outflows for some of the outbursts. We propose a model that can explain all the spectroscopic phenomena observed during this series of outbursts, as well as previous series of outbursts of Z And, and suggest that similar scenarios may be valid for other classical symbiotic stars.     

Characteristics and causes of changes in annual runoff of the Wuding River in 1956–2009

The Yellow River is the second largest river in China. Its runoff experienced rapid changes in the past decades. The trend and driving forces of change of the river’s runoff has been a hot topic in some academic fields in China in recent years, due to its importance in solving the contradiction between supply and demand of water resources, reasonable exploitation and utilization of water resources and its significance in promoting the social, economic and ecologically sustainable development. The Wuding River is one of the large tributaries in the Middle Yellow River and soil and water conservation measures have been implemented in the tributary much earlier. It can be a good example for investigating the trend and causes of changes of runoff of the Yellow River. In this paper, the variation trend and abrupt change are determined in the time series of annual runoff of the Wuding River recorded at a hydrological station near its outlet during the period from 1956 to 2009 using several time series analysis methods. Secondly, the influences of climate change and human activities are estimated through calculating the amount of runoff reduction due to climate change in different periods. Results show that the annual runoff was continually decreasing, the drought trend was aggravating, and abrupt change in runoff series appeared in 1971 and 1997 as a result of large scale water and soil conservation measure after 1971 and ecosystem restoration program since 1997. It is also found that human activities were the main influence factor for runoff reduction during the period from 1972 to 2009. The contributions from climate change increased from about 23 to 30 %, and those from human activities decreased from 77 to 70 % from the period of 1972–1996 to the period of 1997–2009. Finally, a formula is built to reveal the relation of runoff with both climate factors and each main kind of human activities.