南阿尔金木纳布拉克地区长城系巴什库尔干岩群LA-ICP-MS锆石U-Pb定年及其地质意义

采用LA-ICP-MS微区原位锆石U-Pb同位素测定技术,测得木纳布拉克地区原划长城系巴什库尔干岩群红柳泉组的二云二长片麻岩和扎斯勘赛河组二云石英片岩的原岩形成年龄分别介于498~840Ma和500~647Ma之间,表明这2种岩石原岩的形成时代均为新元古代,而不是之前认为的中元古代。另外,红柳泉组二云二长片麻岩边部锆石表现为重稀土元素相对富集型稀土配分模式,其Th/U值大部分小于0.1,为变质锆石,测得其变质时代为498±4Ma,与该地区高压麻粒岩的峰期变质时代(486±5Ma)一致,且与南阿尔金阿尔金岩群中的高压-超高压岩石的峰期变质时代一致,推断其为阿尔金俯冲碰撞引发的高压-超高压变质作用的产物,属于南阿尔金高压-超高压变质带的一部分。通过原岩残留碎屑锆石的年代学对比,发现研究区内这2种岩石及已发现的高压麻粒岩均具有与阿尔金岩群相似的锆石年龄信息,表明本区红柳泉组和扎斯勘赛河组的这3种岩石不应再划归为中元古代的长城系巴什库尔干岩群,将其归属为阿尔金岩群更为合适。     

New iron resources of the South Urals

An area with brick-red loose and viscous sandy-clayey rocks and brown ores with an average Fe content of 19.84% and possible resources of 1 billion tons of metal was determined. Mn and Ti are the main alloying components; Ni, Co, Cr, V, and Zr are additional; and goethite (FeOOH) is an ore mineral.     

Shaking table tests and numerical simulation of dynamic properties of underground structures

It is considered thai the damage of the underground structures caused by earthquakes is minor for a long time. However, the catastrophic damages induced by several recent earthquakes （e. g. Kobe earthquake in 1995 ） revealed that the study on the dynamic properties of the underground structures is indispensable. The dynamic behavior and damage mechanism of underground structure are analyzed by using shaking table tests （ both shallow-and deep-buried） and numerical simulation （3D FEM） including horizontal and vertical input motions, individually and simultaneously. From the results, the underground structure collapsed due to strong horizontal forces although vertical deformation is not negligible. The vertical excitation increases the response of structure, especially the stress and shear stress at the upper section; the soil influenced the property of soilstructure system. In the same excitation, the response in shallow-buried test is larger than deep case. Both overburden and vertical earthquake play important roles in the response of structure and those are two critical aspects in the design of the large-span underground structures, such as subway stations.     

On the exactness of estimates for irregularly structured bodies of the general term of Laplace series

The main form of the representation of a gravitational potential V for a celestial body T in outer space is the Laplace series in solid spherical harmonics \((R/r)^{n+1}Y_n(\theta ,\lambda )\) with R being the radius of the enveloping T sphere. The surface harmonic \(Y_n\) satisfies the inequality

$$\begin{aligned} \langle Y_n\rangle < Cn^{-\sigma }. \end{aligned}$$

The angular brackets mark the maximum of a function’s modulus over a unit sphere. For bodies with an irregular structure \(\sigma = 5/2\), and this value cannot be increased generally. However, a class of irregular bodies (smooth bodies with peaked mountains) has been found recently in which \(\sigma = 3\). In this paper, we will prove the exactness of this estimate, showing that a body belonging to the above class does exist and

$$\begin{aligned} 0<\varlimsup n^3\langle Y_n\rangle <\infty \end{aligned}$$

for it.

     

Time-dependent ionization in the envelopes of type II supernovae at the photospheric phase

The importance of allowance for the time-dependent effect in the kinetics at the photospheric phase during a supernova explosion has been confirmed by several independent research groups. The time-dependent effect provides a higher degree of hydrogen ionization in comparison with the steadystate solutions and strengthens the Hα line in the resulting simulated spectrum, with the intensity of the effect increasing with time. However, some researchers argue that the time-dependent ionization effect is unimportant. Its allowance leads to an insignificant strengthening of Hα in their modeling only in the first days after explosion. We have demonstrated the importance of the time-dependent effect with the models of SN 1999em as an example using the new original LEVELS software package. The role of a number of factors that can weaken the time-dependent effect has been checked. We have confirmed that the intensity of the effect is affected by the abundance of metal admixtures in the envelope, while the addition of extra levels to the model hydrogen atom weakens the time-dependent effect to a lesser degree and never removes it completely.     

Evolution of a Gas–Dust Cloud in the Upper Atmosphere: Analysis of Events October 26, 2017

Geomagnetism and Aeronomy - A sequence of digital images of a gas–dust cloud of combustion products of solid fuel that formed during the separation of rocket stages is analyzed. The images...     

Studying the Concentration of Microplastic Particles in Water,Bottom Sediments and Subsoils in the Coastal Area of the Neva Bay,the Gulf of Finland

Water Resources - The concentration of microplastic particles (with size from 100 µm to 5 mm) and their chemistry were studied in water, subsoils and sediments in the coastal area of the Neva...     

电子束CT三维重建技术与颅颌面外科

目的 探讨电子束CT三维重建技术在颅颌面外科的适应症和应用价值。方法 采用美国Imatron公司的电子束CT(electron beam CT,以下简称EBCT)C-150,对76例严重颅颌面病人实行薄层CT容积扫描。将所获CT图象经数字接口传至加拿大ISG公司生产的Allegro工作站进行三维重建。结果EBCT成像技术能立体的、详尽和精确的显示机体组织三维解剖结构极其相互关系。其再现畸形或病体模型的程度可以达到近乎解剖学的精度,为准确了解和掌握病情并制定合理的手术治疗计划提供了极为重要的依据,提高了手术治疗效果。结论EBCT三维重建技术是现代颅颌面外科最主要的诊断方法之一并具有重要的临床应用价值。