Cosmological tests based on the abundance of galaxy clusters

We present a new normalization for the linear density-perturbation spectrum in a multi-parameter model of the Universe. Using the differential mass function for the nearly galaxy clusters obtained from optical data, we have constructed a functional relation between the dispersion of the density contrast σ ₈ on the scale 8h ^?1 Mpc and the cosmological parameters Ω _m , Ω_Λ, h, n, f _v for each of three theoretical approximations of the mass function: Press-Schechter, Sheth-Tormen and Jenkins. An extended class of models of the Universe with general spatial curvature include four parameters for the matter components: baryons (Ω _b ), “cold” dark matter (Ω _c ), “hot” dark matter (Ω _v ), and the vacuum energy (Ω_Λ). It is shown that the most accurate normalization of the power spectrum is achieved with the Sheth-Tormen approximation.     

Detail studies of the physical properties in the outer regions of galaxy clusters using <Emphasis Type="Italic">Suzaku</Emphasis> observations

A detailed physical analysis of five nearby galaxy clusters using Suzaku observationsis presented. The low and stable level of the instrumental background at large radii facilitate the determination of the main physical characteristics in clusters at the virial radius. The temperatures, metal abundances, and entropy profiles have been constructed out to the outskirts of the clusters. The temperature profiles all display the same shape, with a negative gradient towards to the center and a flat outer plateau. The strong temperature gradients in the central parts of the clusters are usually associated with strong peaks of the surface brightness profiles. The temperature systematically decrease outward from the central regions, by a factor of three at and slightly beyond the cluster outskirts. The temperature profiles are compared with profiles predicted by N-body and hydrodynamical simulations obtained using several numerical algorithms. The slopes in the observed and simulated temperature profiles are consistent with each other in the cluster outskirts. The central regions of the clusters are characterized by low entropy and high metallicity. The possible influence of cool cores on the cluster outskirts is also discussed. The total mass profiles were determined using the observed gas-density and temperature profiles, assuming hydrostatic equilibriumand spherical symmetry. The gas-density profiles were fitted using an improved three-dimensional model to fit the inner and outer regions of the cluster independently. The total mass profiles were described using an NFW model out to R₂₀₀. The measurements show clear evidence for universality of the total mass distribution. The scaled mass profiles in units of R₂₀₀ and M₂₀₀ display a dispersion of ~15% at 0.1R₂₀₀. The fraction of gas out to R₂₀₀ was also found.     

The role of dark matter in the dynamical evolution of galaxy clusters in the framework of the <Emphasis Type="Italic">N</Emphasis>-body problem

NumericalN-body studies of the dynamical evolution of a cluster of 1000 galaxies were carried out in order to investigate the role of dark matter in the formation of cD galaxies. Two models explicitly describing the darkmatter as a full-fledged component of the cluster having its own physical characteristics are constructed. These treat the dark matter as a continuous underlying substrate and as “grainy” matter. The ratio of the masses of the dark and luminous matter of the cluster is varied in the range 3–100. The observed logarithmic spectrum dN ∼ dM / M is used as an initial mass spectrum for the galaxies. A comparative numerical analysis of the evolution of the mass spectrum, the dynamics of mergers of the cluster galaxies, and the evolution of the growth of the central, supermassive cD galaxy suggests that dynamical friction associated with dark matter accelerates the formation of the cD galaxy via the absorption of galaxies colliding with it. Taking into account a dark-matter “substrate” removes the formation of multiple mass-accumulation centers, and makes it easier to form a cD galaxy that accumulates 1–2% of the cluster mass within the Hubble time scale (3–8 billion years), consistent with observations.     

Dynamical evolution of galaxy clusters in the framework of the <Emphasis Type="Italic">N</Emphasis>-body problem. The formation of supermassive cD galaxies

We have carried out numerical simulations of the dynamical evolution of galaxy clusters taking into account merging when the relative velocities of the colliding galaxies are low. In particular, we study the evolution of the structure, mass spectrum, and velocity spectrum of a cluster of a thousand galaxies, as well as the growth of the central supermassive cD galaxy. The initial velocity dispersion of the galaxies and the rotation of the cluster were taken into account. The observed logarithmic spectrum dN ～ \(\tfrac{{dM}}{M}\) was adopted as the initial mass spectrum. The dynamical evolution of galaxy clusters, allowing for the possible merging of colliding galaxies, results in the emergence of a central supermassive galaxy, whose mass continuously increases due to mergers. This occurs only if the mass of the central galaxy becomes greater than ～0.1 of the total mass of the cluster. The observation of cD galaxies with relative masses of ～0.01 suggests that they initially formed in the cluster core, merged with nearby galaxies, and accreted intergalactic gas. The model indicates that a logarithmic galaxy mass spectrum is preserved during the cluster evolution, despite the substantial decrease in the number of galaxies in the cluster with time. The model can also reproduce the observed mass distribution with distance from the cluster center, M _r ～ r ^1.7.     

Stability analysis of the slope around flood discharge tunnel under inner water exosmosis at Yangqu hydropower station

The stability of the slope around a flood discharge tunnel is influenced by the space topography, the geological structure, the seepage of the flood discharge tunnel, the rainfall and so on, which introduce complexity and uncertainty to the problem of slope engineering. For slope stability analysis at the outlet of a flood discharge tunnel affected by high interior hydraulic pressure, the inner water exosmosis (IWE) phenomenon will become obvious, the rock’s mechanical properties will be changed, and the seepage effects of the flood discharge tunnel should be focused on. In this paper, a complicated three-dimensional (3D) numerical simulation and safety assessment of the slope around the flood discharge tunnel at Yangqu hydropower station is implemented in FLAC^3D, and 3D slide arcs of good shape are obtained. When calculating the safety coefficient of slopes, the Shear Strength Reduction Technique (SSRT) is adopted, and a factor of safety (FOS) is then found. It is found that the FOS of the natural slope is 1.43 in its original condition, and in this case, the slope is in a stable state. The safety factor of the slope is 1.30 after the slope excavation without considering IWE. Under the condition of normal seepage from inside the tunnel to the outside, the safety factor is 1.29. For investigating the influence of IWE on the slope stability, we design three types of scenarios – minimal seepage, normal seepage and serious seepage – for the fluid–solid coupling calculation. Under the serious seepage condition, the safety factor of the slope is 1.26, and it is in a critical failure state. It should be pointed out that uncertainties in input parameters are not researched in this paper. There is not big difference among safety factors under different scenarios mainly because the maximum of inner water head of the flood discharge tunnel is only about 80 m. It still can be found that seepage action has an effect on the stability of the whole slope from calculation results. The stress concentrated region (SCR) near the surrounding rock grows from inside to outside as the seepage intensity increases. The surrounding rock will experience more water pressure and seepage pressure, and, at the same time, the area of the plastic zone grows. Suitable treatments and suggestions are discussed to eliminate the adverse effects of IWE. The research results in this paper can provide a reference for construction, reinforcement and drainage design of the slope in similar hydropower slope engineering scenarios.     

斜坡上异重流的三维数值模拟

针对异重流的流动特征,建立了适用于具有各向异性浮力紊动特征的三维异重流运动的数学模型,并模拟了异重流在15°斜坡底面上的潜行过程。计算结果准确地模拟了异重流的运动特征和形态,其前锋的潜行速度与实验结果相当吻合。该模型采用非结构同位网格上的SIMPLEC算法能适应复杂边界和地形,可应用于自然界实际环境中异重流的演进计算。     

Comparison of <Emphasis Type="Italic">U BV R</Emphasis> photometry of giant HII regions in the galaxy NGC 628 with a detailed grid of evolutionary models for star clusters

We present the results of U BV RI CCD photometry of giant HII regions in the spiral galaxy NGC 628, acquired with the 1.5 m telescope of the Mt. Maidanak Observatory (Uzbekistan) with an angular resolution better than 1″. We estimate the ages and interstellar extinctions of these regions and identify the acting star-formation mode by comparing the observed color indices with a detailed grid of evolutionary models covering the entire range of parameters of the initial mass function and of ages of the young star-formation complexes, and taking into account two star-formation modes. We find a radial gradient of the interstellar extinction in NGC 628, which is consistent with the radial abundance gradient found earlier by other authors from independent spectrophotometry. Our age estimates agree with abundance estimates from independent observations.     

Experimental multipole-refined and theoretical charge density study of LiGaSi<Subscript>2</Subscript>O<Subscript>6</Subscript> clinopyroxene at ambient conditions

The synthetic LiGaSi₂O₆ clinopyroxene is monoclinic C2/c at room-T. Its experimental electron density, ρ(r), has been derived starting from accurate room-T single-crystal diffraction data. Topological analysis confirms an intermediate ionic-covalent character for Si–O bonding, as found by previous electron-density studies on other silicates such as diopside, coesite and stishovite. The non-bridging Si–O bonds have more covalent character than the bridging ones. The Ga–O bonds have different bonding characters, the Ga–O2 bond being more covalent than the two Ga–O1 bonds. Li–O bonds are classified as pure closed-shell ionic interactions. Similar to spodumene (LiAlSi₂O₆), Li has sixfold coordination, but the bond critical points associated to the two longest bonds are characterized by very low electron density values. Similar to what previously found in spodumene and diopside, O···O interactions were detected from the topological analysis of ρ(r), and indicate a cooperative interaction among the lone pairs of neighbouring oxygen atoms. In particular, this kind of interaction has been obtained for the O1···O1 edge shared between two Ga octahedra. Integration over the atomic basins gives net charges of −1.39(10), 2.82(10), 1.91(10) and 0.82(8) e for O (averaged), Si, Ga and Li atoms, respectively. Periodic Hartree–Fock and DFT calculations confirm the results obtained by multipole refinement of the experimental data. Moreover, the theoretical topological properties of the electron density distribution on the Si₂O₆ group are very similar to those calculated for spodumene. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

<Superscript>87</Superscript>Sr/<Superscript>86</Superscript>Sr anomalies in Late Cretaceous-Early Tertiary strata of the Cauvery basin,south India: Constraints on nature and rate of environmental changes across K-T boundary

The Ariyalur-Pondicherry sub-basin of the Cauvery basin comprises a near complete stratigraphic record of Upper Cretaceous-Lower Tertiary periods. Earlier studies have documented variations of clay mineral assemblages, change in microtexture of siliciclasts and many geochemical and stable isotopic anomalies far below the Cretaceous-Tertiary boundary (KTB) in these strata. This paper documents the occurrences of two positive ⁸⁷Sr/⁸⁶Sr anomalies preceding K-T boundary in this basin and discusses plausible causes. Analysis of trace elemental and stable isotopic profiles, sedimentation history, petrography and mineralogy of the rocks reveal that while both the anomalies may be due to increased detrital influx caused by sea level and climatic changes, the second anomaly might have been influenced by Deccan volcanism which in turn predated KTB. Record of such anomalies preceding K-T boundary supports the view of multi-causal step-wise extinction of biota across KTB.     

Deformation at the Easternmost Altyn Tagh Fault: Constraints on the Growth of the Northern Qinghai–Tibetan Plateau

How the Altyn Tagh fault(ATF) extends eastwards is one of the key questions in the study of the growth of the Qinghai–Tibetan Plateau. Detailed fieldwork at the easternmost part of the ATF shows that the ATF extends eastward and bypasses the Kuantan Mountain; it does not stop at the Kuantan Mountain, but connects with the northern Heishan fault in the east. The ATF does not enter the Alxa Block but extends eastward along the southern Alxa Block to the Jintanan Mountain. The Heishan fault is not ...     

永吉高速公路黑潭坪边坡三维稳定性研究

通过对永吉高速公路黑潭坪边坡的野外调查,详细地了解了研究区工程地质条件,探讨了边坡变形破坏机理,结合室内试验和计算反演获取岩土体强度参数,在此基础上建立三维地质模型,运用FLAC3D数值分析软件采用强度折减法对不同工况下的坡体稳定性进行详细分析并提出治理建议。研究表明:(1)边坡变形破坏是内外因素综合作用的结果,岩土体性质不良是边坡变形破坏的内在因素,坡脚便道开挖和地表水下渗是边坡变形破坏的诱导因素;(2)强度折减法应用于边坡三位稳定性分析具有较好的适用性;(3)数值模拟显示采用削坡结合锚固的综合治理措施具有明显的效果。     

<Emphasis Type="Italic">UBV RI</Emphasis> CCD photometry of the nearby low-surface-brightness galaxy NGC 5585

The structure and composition of the stellar population in the low-surface-brightness galaxy NGC 5585 is studied using UBV RI CCD photometry. The observations were obtained on the 1.5-m telescope of the Maidanak Observatory of the Astronomical Institute of the Academy of Sciences of Uzbekistan under conditions with seeing 1.2″–1.8″. A two-dimensional decomposition of the galaxy emission into bulge and disk components is carried out. Both components have low surface brightnessess. The Sersic parameter for the bulge is n = 1.2–1.6. The effective radius of the bulge in R and I is equal to the scale length for the brightness decrease in the disk, and comprises 30″–40″ (0.8–1.1 kpc). The spiral arms seem to form a bar, but the centers of the bar and ring do not coincide with the center of NGC 5585. A powerful star-forming region is observed 3.2″ (100 pc) from the galactic center, whose radiation swamps the nucleus in the U and B filters. Based on the positions of the various components of the galaxy in two-color diagrams, it is concluded that NGC 5585 has a complex star-forming history that may be different at different distances from the center.     

Effect of density and compressibility on <Emphasis Type="Italic">K</Emphasis><Subscript>0</Subscript> of cohesionless soils

This paper revisits the earth pressure coefficient at rest K ₀ of granular materials, with the focus being placed on the variation of K ₀ with the internal friction angle, density and compressibility of soils. Following laboratory tests that are carried out to determine K ₀ of two granular materials, the experimental data are interpreted using the original hypoplasticity model for sand proposed by von Wolffersdorff [49]. K ₀ is generally a function of void ratio, stress level and the critical state friction angle; it can be alternatively related to the compressibility of soil. The results show that Jáky’s equation may still be considered as a reasonable representation of K ₀ for granular soils statistically, even though it may not be able to reproduce the experimental data of a specific soil.     

New density measurements on carbonate liquids and the partial molar volume of the CaCO<Subscript>3</Subscript> component

Density measurements on nine liquids in the CaCO₃–Li₂CO₃–Na₂CO₃–K₂CO₃ quaternary system were performed at 1 bar between 555 and 969 °C using the double-bob Archimedean method. Our density data on the end-member alkali carbonate liquids are in excellent agreement with the NIST standards compiled by Janz (1992). The results were fitted to a volume equation that is linear in composition and temperature; this model recovers the measured volumes within experimental error (±0.18% on average, with a maximum residual of ±0.50%). Our results indicate that the density of the CaCO₃ component in natrocarbonate liquids is 2.502 (±0.014) g/cm³ at 800 °C and 1 bar, which is within the range of silicate melts; its coefficient of thermal expansion is 1.8 (±0.5)×10^–4 K^–1 at 800 °C. Although the volumes of carbonate liquids mix linearly with respect to carbonate components, they do not mix linearly with silicate liquids. Our data are used with those in the literature to estimate the value of in alkaline silicate magmas (20 cm³/mol at 1400 °C and 20 kbar), where CO₂ is dissolved as carbonate in close association with Ca. Our volume measurements are combined with sound speed data in the literature to derive the compressibility of the end-member liquids Li₂CO₃, Na₂CO₃, and K₂CO₃. These results are combined with calorimetric data to calculate the fusion curves for Li₂CO₃, Na₂CO₃, and K₂CO₃ to 5 kbar; the calculations are in excellent agreement with experimental determinations of the respective melting reactions.Editorial responsibility: I Carmichael     

Late Cretaceous‐Cenozoic Multi‐Stage Denudation at the Western Ordos Block: Constraints by the Apatite Fission Track Dating on the Langshan

The apatite fission track dating of samples from the Dabashan(i.e., the Langshan in the northeastern Alxa Block) by the laser ablation method and their thermal history modeling of AFT ages are conducted in this study. The obtained results and lines of geological evidence in the study region indicate that the Langshan has experienced complicated tectonic-thermal events during the the Late Cretaceous-Cenozoic. Firstly, it experienced a tectonic-thermal event in the Late Cretaceous(~90–70 Ma). The event had little relation with the oblique subduction of the Izanagi Plate along the eastern Eurasian Plate, but was related to the Neo-Tethys subduction and compression between the Lhasa Block and Qiangtang Block. Secondly, it underwent the dextral slip faulting in the Eocene(~50–45 Ma). The strike slip fault may develop in the same tectonic setting as sinistral slip faults in southern Mongolia and thrusts in West Qinling to the southwest Ordos Block in the same period, which is the remote far-field response to the India-Eurasia collision. Thirdly, the tectonic thermal event existed in the late Cenozoic(since ~10 Ma), thermal modeling shows that several samples began their denudation from upper region of partial annealing zone(PAZ), and the denudation may have a great relationship with the growth of Qinghai-Tibetan Plateau to the northeast. In addition, the AFT ages of Langshan indicate that the main body of the Langshan may be an upper part of fossil PAZ of the Late Cretaceous(~70 Ma). The fossil PAZ were destroyed and deformed by tectonic events repeatedly in the Cenozoic along with the denudation.     

猴子岩水电站进水口洞脸边坡稳定性分析

猴子岩进水口洞脸边坡高约180m,由于开挖所形成的边坡属于高陡边坡,其开挖后的稳定状况会极大影响引水系统的正常运行。通过对该边坡平洞揭露裂隙特征及地表工程地质条件的系统调查,对边坡的岩体结构类型及其结构面、断层与坡面组合特征进行了细致研究,在此基础上对可能的滑面组合采用刚体极限平衡法进行计算。最后对边坡的安全稳定性进行了评价。     

Potential protonation sites in the Al<Subscript>2</Subscript>SiO<Subscript>5</Subscript> polymorphs based on polarized FTIR spectroscopy and properties of the electron density distribution

Potential protonation sites for, kyanite, sillimanite, and andalusite, located in a mapping of the (3, −3) critical points displayed by their L(r) = −∇²ρ(r) distributions, are compared with polarized single-crystal FTIR spectra of kyanite and sillimanite determined earlier and with andalusite measured in this study. For andalusite, seven peaks were observed when the electric vector, E, is parallel to [100]: four intense ones at 3,440, 3,460, 3,526, and 3,597 cm⁻¹ and three weaker ones at 3,480, 3,520, and 3,653 cm⁻¹. Six peaks, three intense ones at 3,440, 3,460, and 3,526 cm⁻¹ and three weaker ones at 3,480, 3,520, and 3,653 cm⁻¹ when E parallels [010]. No peaks were observed when E is parallel to [001]. The concentration of water in andalusite varies between 110 and 168 ppm by weight % H₂O. Polarized FTIR spectra indicate that the OH vector is parallel to (001) in andalusite and sillimanite and in kyanite. Examination of the L(r) (3, −3) critical points in comparison with the polarized FTIR indicates that H prefers to bond to the oxygen atoms O1 and O2 in andalusite and O2 and O4 in sillimanite which correspond to the underbonded oxygen atoms and those with the largest L(r) maxima. In kyanite, comparison of the FTIR spectrum and the critical points indicates that H will preferentially bond to the two 4-coordinated O2 and O6 atoms.     

Probing interfacial reactions with X-ray reflectivity and X-ray reflection interface microscopy: Influence of NaCl on the dissolution of orthoclase at pOH 2 and 85 °C

The role of electrolyte ions in the dissolution of orthoclase (0 0 1) in 0.01 m NaOH (pOH ∼ 2) at 84 ± 1 °C is studied using a combination of in-situ X-ray reflectivity (XR) and ex-situ X-ray reflection interface microscopy (XRIM). The real-time XR measurements show characteristic intensity oscillations as a function of time indicative of the successive removal of individual layers. The dissolution rate in 0.01 m NaOH increases approximately linearly with increasing NaCl concentration up to 2 m NaCl. XRIM measurements of the lateral interfacial topography/structure were made for unreacted surfaces and those reacted in 0.01 m NaOH/1.0 m NaCl solution for 15, 30 and 58 min. The XRIM images reveal that the dissolution reaction leads to the formation of micron-scale regions that are characterized by intrinsically lower reflectivity than the unreacted regions, and appears to be nucleated at steps and defect sites. The reflectivity signal from these reacted regions in the presence of NaCl in solution is significantly lower than that calculated from an idealized layer-by-layer dissolution process, as observed previously in 0.1 m NaOH in the absence of added electrolyte. This difference suggests that dissolved NaCl results in a higher terrace reactivity leading to a more three-dimensional process, consistent with the real-time XR measurements. These observations demonstrate the feasibility of XRIM to gain new insights into processes that control interfacial reactivity, specifically the role of electrolytes in feldspar dissolution at alkaline conditions.     

The supermassive black hole at the center of our galaxy: Determination of its main physical parameters

We have used two astrometric methods developed at the Main Astronomical Observatory of the Russian Academy of Sciences—the method of apparent-motion parameters (AMP) and a direct geometrical method (DGM)—to derive the orbit of the star S2 around the Galactic center, and thereby the mass of the supermassive black hole at the Galactic center. The AMP method, which is based on measurements of the curvature of a fairly short orbital arc, is efficient if observational data on the relative radial velocity are available. The mass of the supermassive black hole was also estimated using astrophysical methods, based on the empirical relation between the masses of the supermassive black holes at the centers of galaxies and quasars and the radio and X-ray luminosities of these regions. We estimate the magnetic-field strength near the event horizon of the supermassive black hole at the Galactic center using a synchrotron self-absorption model.     

First <Superscript>40</Superscript>Ar/<Superscript>39</Superscript>Ar age determinations on the Malkhan granite-pegmatite system: Geodynamic implications

The Malkhan granite-pegmatite system located in Central Transbaikalia, in the southwestern portion of the Malkhan-Yablonovy structure-formational zone of the Caledonian folding comprises two granite massifs (Bolsherechensk and Oreshny) and a miarolitic pegmatite field of the same name, which adjoins the Chikoi deep-seated fault and Lower Cretaceous Chikoi rift depression in the north. The first ⁴⁰Ar/³⁹Ar data were obtained on porphyritic biotite granites of the Oreshny massif and on K-feldspar, muscovite, and lepidolite from the Oktyabrskaya pegmatite vein. According to these data, the age of the granitepegmatite system is 123.8–127.6 Ma, which is consistent with the age of Lower Cretaceous rocks from the Chikoi depression. The intimate spatial relationship and isochronism between the Chikoi depression and the Malkhan granite-pegmatite system are strongly suggestive of a rift regime that affected its evolution, thus highlighting the need to regard the evolution of this system as being intimately related to depression development. Such a model can easily be realized within the framework of the concept of a metamorphic core complex, which was used to explain the nature of Transbaikal-type rift depressions and conjugate granite-gneiss swells.