Orbital parameters of infalling dark matter substructures

We present distributions of the orbital parameters of dark matter substructures at the time of merging into their host halo. Accurate knowledge of the orbits of dark matter substructures is a crucial input to studies which aim to assess the effects of the cluster environment on galaxies, the heating of galaxy discs and many other topics. Orbits are measured for satellites in a large number of N -body simulations. We focus on the distribution of radial and tangential velocities, but consider also distributions of orbital eccentricity and semimajor axis. We show that the distribution of radial and tangential velocities has a simple form and provide a fitting formula for this distribution. We also search for possible correlations between the infall directions of pairs of satellites, finding evidence for positive correlation at small angular separations as expected if some infall occurs along filaments. We also find (weak) evidence for correlations between the direction of the infall and infall velocity and the spin of the host halo.     

Quantitative Study of Galaxy Morphology

We use an automatic algorithm to fit two-dimensional bulge and disk surface brightness profiles to a sample of 200 Sloan Digital Sky Survey Early Data Release (SDSS EDR) galaxies of known redshift and brighter than r=16. The bulge-to-disk (B/D) luminosity ratios can be combined with an estimate of the galaxy's local environment to address a number of key issues that are central to our understanding of galaxy formation:– How do B/D ratios depend upon galaxy luminosity?– What are the disk and spheroid luminosity functions for field galaxies?– How does the total luminosity in bulges and disks depend on environment?     

The End of Sustainability

It is time to move past the concept of sustainability. The realities of the Anthropocene warrant this conclusion. They include unprecedented and irreversible rates of human-induced biodiversity loss, exponential increases in per-capita resource consumption, and global climate change. These factors combine to create an increasing likelihood of rapid, nonlinear, social and ecological regime changes. The recent failure of the Rio + 20 provides an opportunity to collectively reexamine—and ultimately move past—the concept of sustainability as an environmental goal. We must face the impossibility of defining—let alone pursuing—a goal of “sustainability” in a world characterized by such extreme complexity, radical uncertainty and lack of stationarity. After briefly examining sustainability's failure, we propose resilience thinking as one possible new orientation and point to the challenges associated with translating resilience theory into policy application.     

砌体填充框架结构的实时子结构试验方法及仿真分析

由于砌体填充框架结构的砌体与框架之间的相互作用,使得其整体动力性能非常复杂。如何通过实时试验准确揭示其抗震性能是非常值得研究的内容。本文介绍了砌体填充框架结构的实时子结构试验方法,并进行了数值模拟。数值模拟的结果表明,本文的方法具有很好的稳定性和精度。     

The SCUBA HAlf Degree Extragalactic Survey – VI. 350-μm mapping of submillimetre galaxies

A follow-up survey using the Submillimetre High-Angular Resolution Camera (SHARC-II) at 350 μm has been carried out to map the regions around several 850-μm-selected sources from the Submillimetre HAlf Degree Extragalactic Survey (SHADES). These observations probe the infrared (IR) luminosities and hence star formation rates in the largest existing, most robust sample of submillimetre galaxies (SMGs). We measure 350-μm flux densities for 24 850-μm sources, seven of which are detected at ≥2.5σ within a 10 arcsec search radius of the 850-μm positions. When results from the literature are included the total number of 350-μm flux density constraints of SHADES SMGs is 31, with 15 detections. We fit a modified blackbody to the far-IR (FIR) photometry of each SMG, and confirm that typical SMGs are dust-rich  ( M _dust≃ 9 × 10⁸ M_⊙)  , luminous  ( L _FIR≃ 2 × 10¹² L_⊙)  star-forming galaxies with intrinsic dust temperatures of ≃35 K and star formation rates of  ≃400 M_⊙ yr⁻¹  . We have measured the temperature distribution of SMGs and find that the underlying distribution is slightly broader than implied by the error bars, and that most SMGs are at 28 K with a few hotter. We also place new constraints on the 350-μm source counts, N ₃₅₀(>25 mJy) ∼ 200–500 deg⁻².     

Well blowout rates and consequences in California Oil and Gas District 4 from 1991 to 2005: implications for geological storage of carbon dioxide

Well blowout rates in oil fields undergoing thermally enhanced recovery (via steam injection) in California Oil and Gas District 4 from 1991 to 2005 were on the order of 1 per 1,000 well construction operations, 1 per 10,000 active wells per year, and 1 per 100,000 shut-in/idle and plugged/abandoned wells per year. This allows some initial inferences about leakage of CO₂ via wells, which is considered perhaps the greatest leakage risk for geological storage of CO₂. During the study period, 9% of the oil produced in the United States was from District 4, and 59% of this production was via thermally enhanced recovery. There was only one possible blowout from an unknown or poorly located well, despite over a century of well drilling and production activities in the district. The blowout rate declined dramatically during the study period, most likely as a result of increasing experience, improved technology, and/or changes in safety culture. If so, this decline indicates the blowout rate in CO₂-storage fields can be significantly minimized both initially and with increasing experience over time. Comparable studies should be conducted in other areas. These studies would be particularly valuable in regions with CO₂-enhanced oil recovery (EOR) and natural gas storage. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

A tabulation and evaluation of ion exchange data on smectites

An extensive search of the literature was made for ion exchange data on smectites. The data, in the form of ion exchange equilibrium constants and free energies of exchange, have been tabulated and evaluated. Equilibrium constants describing monovalent-monovalent and monovalent-divalent types of exchange for the same reaction on the same type of smectite were found to differ by as much as an order of magnitude. While some of the difference can be attributed to variance in experimental procedures, much of the difference appears due to differences in charge densities and effective field strengths of the smectites, which are in turn related to the amount and type of substitution on intercrystalline octahedral and tetrahedral sites.