The sulfurization recorded in tridymite in the monomict eucrite Northwest Africa 11591

Some of the tridymite in the monomict Northwest Africa (NWA) 11591 eucrite are found to have sulfide‐rich replacement textures (SRTs) to varying degrees. The SRTs of tridymite in NWA 11591 are characterized by the distribution of loose porous regions with aggregates of quartz and minor troilite grains along the rims and fractures of the tridymite, and we propose a new mechanism for the origin of this texture. According to the volume and density conversion relationship, the quartz in the SRT of tridymite with a hackle fracture pattern was transformed from tridymite. We suggest that the primary tridymite grains are affected by the S‐rich vapors along the rims and fractures, leading to the transformation of tridymite into quartz. In addition, the S‐rich vapors reacted with Fe²⁺, which was transported from the relict tridymite and/or the adjacent Fe‐rich minerals, and/or the S‐rich vapors react with the exotic metallic Fe to form troilite grains. The sulfurization in NWA 11591 most likely occurred during the prolonged subsolidus thermal metamorphism in the shallow crust of Vesta and might be an open, relatively high temperature (>800 °C) process. Sulfur would be an important component of the metasomatic fluid on Vesta.     

The distribution of QSO absorption lines and its implications

The distribution of L absorption lines has been investigated in the fractal scheme. It is found that (1) the L absorption clouds distribute completely different from that of galaxies; (2) the L absorption clouds are anti-associated with galaxies and quasars. These results may imply that there are two kinds of objects formed by different processes of clustering. This is favourable for the cosmic-string theory on the formation of large-scale structure of the Universe. In the string model, the objects can be divided into two kinds according to their clustering with or without string loops as their initial density perturbation.On leave from the Center of Astrophysics, University of Science and Technology of China, Hefei, P.R. China. Y. Chu is a research fellow of Alexander von Humboldt-Foundation.     

Short-Term Periodicity in Solar Mean Magnetic Field during Activity Maximum and Minimum Periods

The short-term periodicity in the solar mean magnetic field (SMMF) observed at the Wilcox Solar Observatory during the last four activity cycles is investigated by using Lomb?CScargle periodograms. Our results show that the SMMF has main periods of about 27, 13.5, and 9 days in both the maximum and minimum years of each activity cycle. The SMMF has the most dominant period of about 27 days during the activity maxima. However, during the activity minimum years the 13.5-day periodicity is the most significant, except for the minimum of 1984??C?1986. These results indicate that the distribution of active regions in the activity maximum years is quite different from that in the minimum years.     

The amino acid composition of the Sutter's Mill CM2 carbonaceous chondrite

We determined the abundances and enantiomeric compositions of amino acids in Sutter's Mill fragment #2 (designated SM2) recovered prior to heavy rains that fell April 25–26, 2012, and two other meteorite fragments, SM12 and SM51, that were recovered postrain. We also determined the abundance, enantiomeric, and isotopic compositions of amino acids in soil from the recovery site of fragment SM51. The three meteorite stones experienced terrestrial amino acid contamination, as evidenced by the low d/l ratios of several proteinogenic amino acids. The d/l ratios were higher in SM2 than in SM12 and SM51, consistent with rain introducing additional l‐ amino acid contaminants to SM12 and SM51. Higher percentages of glycine, β‐alanine, and γ‐amino‐n‐butyric acid were observed in free form in SM2 and SM51 compared with the soil, suggesting that these free amino acids may be indigenous. Trace levels of d +l‐ β‐aminoisobutyric acid (β‐AIB) observed in all three meteorites are not easily explained as terrestrial contamination, as β‐AIB is rare on Earth and was not detected in the soil. Bulk carbon and nitrogen and isotopic ratios of the SM samples and the soil also indicate terrestrial contamination, as does compound‐specific isotopic analysis of the amino acids in the soil. The amino acid abundances in SM2, the most pristine SM meteorite analyzed here, are approximately 20‐fold lower than in the Murchison CM2 carbonaceous chondrite. This may be due to thermal metamorphism in the Sutter's Mill parent body at temperatures greater than observed for other aqueously altered CM2 meteorites.     

A Study on the Light Curves of GRBs

It is generally believed that the complexity and variability of the light curves of gamma-ray bursts (GRBs) are caused by the internal shocks, which would occur when a rapid shell catches up a slower one and collides with it. The electrons in the shock layer are heated by the shocks and radiate via the mechanisms of synchrotron radiation and inverse Compton scattering. Based on relativistic kinematics, a relation between the photon number of the emission from the rapidly moving shock layer and the number of the photons received by an observer is derived. Then, employing the angular spreading of the internal shock emission, the curve equation and profile of a single pulse are obtained, and the shape is typically in the shape of a fast rise and exponential decline. Furthermore, by using the model of the successive collisions of multiple shells under the condition of reasonable parameters, the observed light curves are fitted with a rather good effect. Therefore, by this means, more different types of light curves of GRBs can be explained.     

Precise Synchrotron Radiation Spectrum of Fast-cooling Electrons and the Prompt GRB Emission

It is generally believed that the synchrotron radiation of electrons from the internal shock is the main radiation mechanism of the prompt GRB (gamma-ray burst) emission. However, what this model predicts can not explain observations well. In this paper, we confirm that electrons are quickly cooled due to radiation losses and also point out that the synchrotron radiation spectrum presented in previous papers is a relatively rough estimation. We get the precise synchrotron radiation spectrum of fast-cooling electrons by carrying out a numerical calculation, and thereby reasonably explain the observed distribution of low-energy spectral index (α) of long GRBs based on a unified model. In addition, we fit the correlation between α and the peak energy of the νFν spectrum (E_p).     

An alternative symbiotic channel to Type Ia supernovae

By assuming an aspherical stellar wind with an equatorial disc from a red giant, we investigate the production of Type Ia supernovae (SNe Ia) via a symbiotic channel. We estimate that the Galactic birthrate of SNe Ia via the symbiotic channel is between  1.03 × 10⁻³  and  2.27 × 10⁻⁵ yr⁻¹  , while the delay time of SNe Ia has a wide range from ∼0.07 to 5 Gyr. The results are greatly affected by the outflow velocity and mass-loss rate of the equatorial disc. Using our model, we discuss the progenitors of SN 2002ic and SN 2006X.     

The equilibrium configuration of rapid rotating compact stars and some gravitational effects

In this paper, the equilibrium configurations of rapid rotating compact stars and some gravitational effects are studied within the general relativity by use of the Harrison-Wheeler equation of state and by the self-consistent field method. Numerical calculations show that the equilibrium configuration of a rotating star is a spheroid. For large spin velocities, say, ω > 3.0 × 10² sec⁻¹ the eccentricity and mass increase very rapidly as the angular velocity increases, for the critical angular velocity of the rotating star, the eccentricity is about 0.7, the increase in mass is about 10–35%. The difference of the gravitational redshifts at the surface of the star caused by rotation, and the difference of the light bending when the beam moves in the direction of rotation or in the opposite direction are obvious.     

Gravity variation before Kunlun mountain pass western Ms=8.1 earthquake

The relation between the gravity variation features and Ms=8.1 earthquake in Qinghai-Xizang monitoring area is analyzed preliminarily,by using spatial dynamic variation results of regional gravity field from absolute gravity and relative gravity observation in 1998 and 2000.The results show that:1)Ms\8.1 earthquake in Kulun mountain pass westem occurred in the gravity variation high gradient near gravity‘s high negative variation;2)The Main tectonic deformation and emnergy accumulation before MS=8.1 earthquake are distributed at south side of the epicenter;3)The range of gravity‘s high negative variation at east of the MS=8.1 earthquake epicenter relatively coincides with that rupture region according to field geology investigation;4)Gravity variation distribution in high negative value region is just consistent with the second shear strain‘s high value region of strain field obtained from GPS observation.     

The distribution and natural degradation of cyanide in goldmine tailings and polluted soil in arid and semiarid areas

Farmlands and rivers have been seriously polluted by cyanide from a goldmine tailings dam that collapsed in early spring of 1995 in Yining County, Xinjiang Autonomous Region of China. The cyanide distribution in the polluted farmland and the abandoned tailings dam was studied, three and 4 years after the accident occurred. The results indicated that natural degradation of cyanide in soils is slower than in natural water bodies. The cyanide transport in the soil section is similar to freely soluble salts. In arid and semiarid areas, cyanide can be highly enriched in the salt crust in which the concentration is even higher than the fresh tailings debris though cyanide has decomposed for 4 years. In the polluted farmland, the sticky layer in the soil section can highly adsorb and enrich cyanide so it can partly prevent cyanide transfer to groundwater. According to the characteristics of cyanide natural degradation in soil, the measures for prevention and cure of soil polluted by goldmine tailing dam collapse have been discussed.