Spectrum and Variability of the Supernova Remnant G21.5-0.9

Measurements of the flux densities of the supernova remnant G21.5-0.9 at 4840 and 8450 MHz were performed in 2013–2018 on the 32-m telescope of the Svetloe Observatory of the Institute of Applied Astronomy, Russian Academy of Sciences. Multiple measurements revealed source variability. The flux densities of G21.5-0.9 for 1967–2010 from previously published data are used to compare the intensity of G21.5-0.9 and standard sources. An artificial-Moon flux scale is used to bring all the data into a single system and determine a refined spectrum. Analysis of the resulting data indicates that, first, the observed break in the source spectrum is not associated with energy losses of relativistic electrons due to synchrotron emission and, second, the source variability is manifest as flux-density changes described by one of two power-law dependencies for the flux versus frequency. The spectral indices of each of these dependencies have one of two constant values. Possible origins of the detected changes in the spectrum of G21.5-0.9 are discussed.

     

Radio Emission Variability of Supernova Remnants and a Possible Explanation of the Phenomenon

Astronomy Reports - The flux densities and current spectra of plerions and combined supernova remnants (SNRs): 3C58, 3C144, G11.2–0.3, G21.5–0.9, and 3C396 are determined on an...     

Search for Periodic Emission from Five Gamma-Ray Pulsars at the Frequency of 111 MHz

Astronomy Reports - The search for pulsar (periodic) radiation of five gamma-ray pulsars was carried out using the summed power spectra and summed periodograms. No harmonics corresponding to the...     

Accretion of neutral hydrogen and helium onto a neutron star. The X-ray and gamma-ray radiation of cool neutron stars

The accretion of neutral gas (hydrogen and helium) onto a neutron star is studied. The gas is gravitationally captured into the magnetosphere of the star, where it is ionized by thermal radiation from the stellar surface and accelerated by the electric field at the light cylinder and in a tube of open magnetic lines. Particles accelerated at light cylinder generate gamma-ray, some particles move to the star and heat its polar regions, resulting in the emission of X-rays. Our calculations of the model parameters of the X-ray and gamma-ray radiation indicate that the radiation intensities should be sufficient to be observed.     

植物-土壤有机质转化过程中的碳同位素组成变化

土壤有机质的碳同位素信息反映了上部的植被和气候状况，但植物体在被微生物分解、利用、转变为土壤有机质的过程中会产生碳同位素的分馏。本研究探了高山草甸和典型草原两种不同气候、生态环境条件下，植物转变为土壤有机质过程中的碳同位素组成变化。结果显示：在太白山高海拔地区的4个采样点，表土的δ13Corg值均随深度的增加而逐渐偏正，到距离地表10-15cm左右时，土壤的δ13Corg值基本稳定。经过长期分解稳定以后的土壤有机质的δ13C值要比其源植被约偏正1.65‰-2.27‰左右，平均约偏正1.9‰左右。在内蒙草原样地的4个采样点，亦表现出与太白山相似的变化：土壤样品的δ13Corg值从地表开始，随着深度的增加而逐渐偏正，到约距离地表10cm左右深度后，δ13Corg值逐渐达到稳定，在距地表10-16cm间基本稳定不变。在该深度土壤的δ13Corg值比它上面生长的植物的δ13C值要分别偏正1.3‰、1.4‰、1.4‰、1.2‰，4块样地平均偏正约1.3‰左右。本研究表明，在运用土壤有机碳同位素反淀古植被和古气候变化时，应考虑到不同气候、生态环境中植物转化为有机质过程中的碳同位素分馏影响。     

Rapid and Simple Measurement of H2 Emission from Active Faults Using Compact Sampling Equipments

Smaller equipment has been developed for sampling and measuring H₂ in fault zones. A considerable volume of hydrogen emission, suggesting the presence of fluid paths along fault zones, was detected within a 1‐h simple field procedure at an active fault in Central Japan, the Atotsugawa Fault. The equipment enabled measurements in a thin fault gouge with a thickness of 10 mm; this led to pervasive sampling from small fault zones hosted in harder rocks. A rapid evaluation of the spatio‐temporal heterogeneity of hydrogen emissions along the faults, using the present method, would increase knowledge of fluid circulation around faults.     

Salt Marsh Accretion and Storm Tide Variation: an Example from a Barrier Island in the North Sea

We reconstruct past accretion rates of a salt marsh on the island of Sylt, Germany, using measurements of the radioisotopes ²¹⁰Pb and ¹³⁷Cs, as well as historical aerial photographs. Results from three cores indicate accretion rates varying between 1 and 16 mm year⁻¹. Comparisons with tide gauge data show that high accretion rates during the 1980s and 1990s coincide with periods of increased storm activity. We identify a critical inundation height of 18 cm below which the strength of a storm seems to positively influence salt marsh accretion rates and above which the frequency of storms becomes the major factor. In addition to sea level rise, we conclude that in low marsh zones subject to higher inundation levels, mean storm strength is the major factor affecting marsh accretion, whereas in high marsh zones with lower inundation levels, it is storm frequency that impacts marsh accretion.     

Observational Manifestations of the Precessional Wave in the Accretion Disk of a Cataclysmic Variable Star

Effects due to the interaction of the steam from the inner Lagrangian point with the accretion disk in a cataclysmic variable star are considered. The results of three-dimensional gas-dynamical numerical simulations confirm that the disk thickness in the vicinity of the interaction with the stream is minimum when the component-mass ratio is 0.6. As a consequence, some of the matter from the stream does not collide with the outer edge of the accretion disk, and continues its motion unperturbed toward the accretor. This part of the stream subsequent interacts (collides) with a thickening of the accretion disk due to the presence of a precessional wave in the disk, leading to the appearance of an additional zone of heating at the disk surface. This additional zone of enhanced luminosity (hot spot) is a direct observational manifestation of the precessional wave in the accretion disk.     

Geochemistry of Suspended Matter from Waters of the Amazon Basin

The geochemical study of the suspended matter in the waters of the Amazon River and its tributaries revealed that the chemical composition of this material ranges widely; however, generally, it is similar to the average composition of the suspended matter in the rivers and clayey sedimentary rocks around the world. Against this background, an essential regional Hg enrichment due to the anthropogenic factor is distinguished. The suspensions from the so-called clear waters from the tributaries of the Amazon River—Xingu and Trombetas—demonstrate the local enrichment in Pb, Sn, Zn, and organic carbon indicating the ore mineralization of the drainage basin, and points to the presence of metal-organic complexes.     

Crustal Accretion and Reworking within the Khanka Massif: Evidence from Zircon Hf Isotopes of Phanerozoic Granitoids

The Central Asian Orogenic Belt(CAOB)is one of the largest Phanerozoic accretionary orogen.(Windley et al.,1990,2007;Jahn et al.,2000a,b,c;Yakubchuk,2002,2004;Xiao et al.,2003,2004).It is the optimal study area for revealing the accretion and reworking processes of the continental crust.The Khanka Massif is located in the most eastern part of the CAOB,and mainly crops out in the territory of Russia,with a small segment in NE China.In addition,a large number of multi-stage granitic rocks are formed in geological evolution in this area,recording amounts of information about crustal accretion and reworking processes(De Paolo et al.,1991;Rudnick,1995;Wu et al.,2011).In view of this,this paper uses the spatial-temporal variations of trace elements and zircon Hf isotopic compositions of phanerozoic granitoids within the Khanka Massif as a case to reveal the crustal accretion and reworking processes of micro continental massifs from the orogenic belt,further to understand the formation and evolution processes and mechanisms of the global continental crust.According to the statistics of zircon U-Pb ages of granitoids in the Khanka Massif,indicate that the granitic magmatisms in the Khanka Massif have eleven peaks:492 Ma,460 Ma,445Ma,430Ma,425Ma,302Ma,287Ma,258Ma,249 Ma,216Ma and 213Ma,it can be divided into eight main stages:Late Cambrian,Middle-Late Ordovician,Middle Silurian,Late Carboniferous,EarlyPermian,Middle-Late Permian—Early Triassic,Late Triassic-Early Jurassic,Early Cretaceous.The Phanerozoic granitoids in Khanka massif are selectedinthispaperasasuiteof granodiorite-monzogranite-syenogranite.TheSi O2contents of the Phanerozoic granitoids exceed 65%,and has high Al2O3,low Mg#,TFe2O3,Cr,Co and Ni contents.This suggests that mixture with mantle-derived magma did not occur,and it should be a typical crustal source(Lu and Xu,2011).Combined with evident characteristics of light rare-earth elements(LREEs)and large ion lithophile elements(LILEs)enrichment,and heavy rare-earth elements(HREEs)and high field-strength elements(HFSEs)loss,we suggest that the primary magma was derived by partial melting of lower crustal material(Xu et al.,2009),and geochemical properties of the Phanerozoic granitoids essentially reflect the nature of the magmatic source region.According to the temporal variation of zircon Hf isotopic data of Phanerozoic granitioids,zircon Hf isotopic compositions of Phanerozoic granitoids have a obvious correlation with age.With the decrease of formation time ofthePhanerozoicgranitoids(Late Cambrian~Middle-LateOrdovician~Middle Silurian~EarlyPermian~Middle-LatePermian–Early Triassic~Late Triassic-Early Jurassic),εHf(t)values of zircons gradually increase,whereas their TDM2 ages gradually decrease(Paleoproterozoic–Neoproterozoic),suggesting that the generation of granitic magmas from the Khanka Massif could have experienced the change from the melting of the ancient crust to the juvenile crust during Paleozoic to Mesozoic.According to the sample location,it can be found thatεHf(t)values of Phanerozoic granitoids have the tendency to decrease with latitude increase,showing that components of the ancient continental crust gradually increase from south to north.However,at the same latitude range,theεHf(t)values of Phanerozoic granitoids also inconsistent.Taken together,these differences reveal the horizontal and vertical heterogeneity of the lower continental crust within the Khanka Massif.According to the relative probability of two-stage model(TDM2)ages of zircon Hf isotope from Phanerozoic granitoids within the Khanka massif,it could be divided into three stages:(1)Late Paleoproterozoic(2)Mesoproterozoic(3)Neoproterozoic.It reveals that the main part of the continental crust within the Khanka MassifwereformedinLate Paleoproterozoic–Neoproterozoic.The Phanerozoic granitoids in the Khanka Massif reworked from the source rockswithdifferent ages(Paleoproterozoic–Mesoproterozoic–Neoproterozoic).     

Interaction of the Extended Envelope of a Hot Jupiter with a Narrow Coronal Mass Ejection

The passage of a hot Jupiter with a quasi-closed extended envelope through a short coronal mass ejection (CME) with a small opening angle is considered. The results of three-dimensional gasdynamical simulations are used to determine the characteristics of the flow in the planet’s envelope as it intersects the CME, and to infer possible observational manifestations of such an event. Two options are considered—entry of the planet into the CME at the beginning of the CME and a tangential interaction with the leading edge of the CME. The mass lost by the planet as a result of its interaction with the CME is estimated.

     

压密灌浆法处理建筑物不均匀沉降施工实例

分析了广东省潮州市一幢商住楼不均匀沉降产生的原因，介绍了采用压密灌浆对其进行加固处理的实际情况及效果。     

Effect of the Orbit Eccentricity on the Flow in the Envelope of a Hot Jupiter

Astronomy Reports - A three-dimensional numerical gas–dynamic model is presented. The aim of the model is to study the structure of the flow in the envelopes of hot Jupiters with elliptical...     

江西九江地区晚更新世生态变迁的土壤有机质碳同位素证据

根据我国江西九江地区４个土壤剖面的土壤有机质及其δ１３Ｃ值的分析结果,认为末次冰期旋回内生态转型是由于季风效应和ＣＯ２共同作用的表现;北大西洋末次冰期内的Ｈｅｉｎｒｉｃｈ事件对中国东部的气候也产生剧烈的影响,其分布直接控制着Ｃ３和（或）Ｃ４植物的转型及其沉积物的类型．ＣＯ２及其温室气体可能是Ｈｅｉｎｒｉｃｈ事件的重要驱动因素之一．     

有机质在宣龙地区菱铁矿形成中的作用

本文通过对宣龙铁矿中菱铁矿的分布和产状，化学成分，组构特征，碳氧同位素特征及与赤铁矿的生成关系等的分析，对区内菱铁矿进行了较深入细致的研究，进而提出宣龙铁矿中菱铁矿的形成是成岩期有机质对先成赤铁矿还原的结果，沉积物中高铁与低铁的关系直接取决于起还原作用并能把高铁转化为低铁的有机质数量。上述结论又得到了有机地球化学方面资料的证实。     

Accretion of juvenile crust at the Early Palaeozoic Antarctic margin of Gondwana: geochemical and geochronological evidence from granulite xenoliths

Geodynamic models for the Antarctic sector of the active Early Palaeozoic Palaeo-Pacific margin of Gondwana are based on the nature and age of the deep crust of the Robertson Bay terrane, the outermost lithotectonic unit of the margin. As this crustal block is covered with thick turbidite deposits, the only way to probe the deep crust is through the analysis of granulite xenoliths from Cenozoic scoria cones. Low-K felsic xenoliths yield the oldest (Middle Cambrian) laser-probe U–Pb ages on zircon areas with igneous growth zoning. This finding, along with the positive whole-rock ε_Nd(500Ma), suggests that these felsic rocks derived from a juvenile magma formed during the Early Palaeozoic Ross orogenic cycle. Mafic xenoliths have geochemical-isotopic compositions similar to those of modern primitive island arcs, suggesting the involvement of subducted oceanic crust in their magma genesis and accretion of juvenile crust at the Antarctic margin of Gondwana.     

临夏塬堡全新世黄土剖面古土壤有机质碳同位素的气候记录

对甘肃临夏塬堡全新世剖面古土壤有机质碳同位素分析表明, δ13 C变化范围在-28.23‰～25.19‰之间, 平均值为-26.88‰. 结合该剖面孢粉分析结果, 观察到在孢粉所反映的温暖湿润气候期间,δ13 C表现为高值, 而在干燥寒冷期间, δ13 C表现为低值. 说明由于气候变化引起了地表植被类型的改变, 导致了古土壤中有机质δ13 C发生了变化. δ13 C的变化特征分别对应于3个不同的气候演化阶段:早全新世、中全新世和晚全新世阶段, 其所反映的全新世气候特征与我国其它地区的分析结果基本一致. 分析表明, 古土壤中有机质δ13 C是气候变化的一个良好指标.